Mid-Paleozoic to early Mesozoic tectonostratigraphic ...spiercey/Piercey_Research_Site/Publicatio… · Paleozoic Evolution and Metallogeny of Pericratonic Terranes at the Ancient

� 75

Mid-Paleozoic to early Mesozoic tectonostratigraphic evolution of Yukon-Tanana and Slide Mountain terranes

and affiliated overlap assemblages, Finlayson Lake massive sulphide district, southeastern Yukon1

Donald�C.�MurphyYukon�Geological�Survey,�P.O.�Box�2703�(K-10),�Whitehorse,�Yukon,�Y1A�2C6,�Canada�

[email protected]

James�K.�MortensenPacific Centre for Isotope and Geochemical Research, Earth and Ocean Sciences, �University of British Columbia, Vancouver, British Columbia, V6T 1Z4, Canada

Stephen�J.�PierceyMineral Exploration Research Centre, Department of Earth Sciences, �

Laurentian University, 933 Ramsey Lake Road, Sudbury, Ontario, P3E 6B5, Canada

Michael.�J.�OrchardGeological Survey of Canada, 101-605 Robson Street, Vancouver, British Columbia, V6B 5J3, Canada

George E. GehrelsDepartment of Geosciences, University of Arizona,�1040 E. Fourth Street, Tucson, Arizona, 85721, USA

Murphy, D.C., Mortensen, J.K., Piercey, S.J., Orchard, M.J. and Gehrels, G.E., 2006, Mid-Paleozoic to early Mesozoic tectonostratigraphic evolution of Yukon-Tanana and Slide Mountain terranes and affiliated overlap assemblages, Finlayson Lake massive sulphide district, southeastern Yukon, in Colpron, M. and Nelson, J.L., eds., Paleozoic Evolution and Metallogeny of Pericratonic Terranes at the Ancient Pacific Margin of North America, Canadian and Alaskan Cordillera: Geological Association of Canada, Special Paper 45, p. 75-105.

AbstractThe Finlayson Lake massive sulphide district of southeastern Yukon is underlain by variably deformed, metamorphosed

and imbricated mid- to late Paleozoic rocks of Yukon-Tanana and Slide Mountain terranes and affiliated overlap as-

semblages. Yukon-Tanana terrane comprises three fault-bounded successions of Upper Devonian-Lower Mississippian

metavolcanic and metaplutonic rocks that were deposited on a pre-Late Devonian ensialic basement in west- or south-

1Data Repository items Murphy_Appendix1.pdf (Appendix�1)�and Murphy_Appendix2.pdf (Appendix 2), are available on the CD-ROM in pocket.

76

Murphy et al.

west-facing forearc, arc and back-arc geodynamic settings. Upper Mississippian and Upper Pennsylvanian to Lower

Permian limestones are locally prominent, with a rarely preserved intervening Pennsylvanian succession of chert,

intermediate and mafic volcanic rocks, and coarse-grained clastic rocks. The terrane was imbricated by north- to

northeast-vergent thrust faults in the Early Permian, an event accompanied by widespread flysch sedimentation. Slide

Mountain terrane occurs primarily north of the Jules Creek fault, the main boundary between the two terranes. It

comprises Carboniferous to Lower Permian basinal clastic rocks, chert, basalt and limestone that are inferred to have

been deposited on oceanic crust in the extending back-arc region behind the coeval west-facing Yukon-Tanana terrane

arc. Basalt and lesser chert of the Lower Permian Campbell Range formation were deposited on both sides of the Jules

Creek fault, implying juxtaposition of Yukon-Tanana and Slide Mountain terranes along the fault by, or during, the

Early Permian. The narrow distribution of the Campbell Range formation and related plutons around the Jules Creek

fault suggests that it was a ‘leaky’ transform fault. The Campbell Range formation is coeval with volcanic arc rocks to

the west, indicating that its magmatism and associated strike-slip faulting occurred in a back-arc setting.

Various geological considerations indicate a Middle Permian shift to subduction under the northern or northeastern

margin of the amalgamated terranes. This Middle Permian shift marked the onset of the closure of the Slide Mountain

ocean basin, which likely ended prior to the deposition of Upper Triassic sedimentary rocks on Yukon-Tanana terrane,

the North American margin and the remnants of the late Paleozoic Slide Mountain ocean that once separated them.

RésuméLe district de sulfures massifs de Finlayson Lake dans le sud-est du Yukon surplombe des roches du Paléozoïque

moyen à supérieur, diversement déformées, métamorphisées et imbriquées, des terranes de Yukon-Tanana et de Slide

Mountain et des assemblages de chevauchement qui y sont affiliés. Le terrane de Yukon-Tanana comprend trois suc-

cessions limitées par failles, de roches métavolcaniques et métaplutoniques du Dévonien supérieur au Mississipien

inférieur et qui ont été mises en place sur un socle ensialique pré-Dévonien supérieur dans un contexte géodynamique

d’avant-arc, d’arc et d’arrière-arc, orienté vers l’ouest ou le sud-ouest. Par endroits, les calcaires du Mississipien

supérieur et du Pennsylvanien supérieur au Permien inférieur prédominent, avec une succession de cherts

Pennsylvanienne rarement préservée, et des horizons de roches de composition intermédiaire à mafique et des roches

clastiques grossières. Le terrane a été imbriqué au début du Permien par des failles de chevauchement de vergence

nord à nord-est, un événement accompagné par une sédimentation généralisée de flysch. Le gros du terrane de Slide

Mountain est situé au nord de la faille de Jules Creek, la principale ligne de partage entre les deux terranes. Il est

constitué de roches clastiques de bassin sédimentaire, de cherts, de basaltes et de calcaires, du Carbonifère au Permien

supérieur, vraisemblablement mises en place sur une croûte océanique dans une région d’arrière-arc en extension,

derrière l’arc du terrane de Yukon-Tanana orienté vers l’ouest. Le basalte et le chert de la formation de Campbell Range

du Permien inférieur ont été déposés sur les deux côtés de la faille de Jules Creek, ce qui implique que les terranes de

Yukon-Tanana et de Slide Mountain étaient juxtaposés de part et d’autre de la faille, au tout début ou durant le Permien

inférieur. L’étroitesse de la distribution des roches de la formation de Campbell Range et des plutons qui y sont as-

sociés, le long de la faille de Jules Creek permet de penser qu’il s’agissait d’une faille de transformation qui « fuyait ».

La formation de Campbell Range est contemporaine des roches d’arc volcanique à l’ouest, ce qui est l’indication que

son magmatisme et ses failles de décrochement se sont produits dans un contexte d’arrière-arc.

Des considérations géologiques diverses indiquent un changement vers un régime de subduction au Permien moyen

sous la marge nord ou nord-est des terranes amalgamés. Ce changement au Permien moyen a marqué le début de la

fermeture du bassin océanique de Slide Mountain, laquelle a vraisemblablement pris fin avant le dépôt des sédiments

du Trias supérieur sur le terrane du Yukon-Tanana, sur la marge nord-américaine et dans les vestiges de l’océan Slide

Mountain du Paléozoïque supérieur, qui les séparait jadis.

� 77

Finlayson lake Massive sulphide district

INTRODUCTIONThe Finlayson Lake massive sulphide district of southeastern Yukon occurs in the central part of the outlier of Yukon-Tanana and Slide Mountain terranes and affiliated overlap assemblages that lies be-tween the Tintina fault, an Eocene dextral strike-slip fault (Roddick, 1967; Murphy and Mortensen, 2003; Gabrielse et al.,�in�press),�and�the Inconnu thrust fault, the probably Jurassic fault separating the terranes from the North American continental margin sequence (Figs. 1, 2; Murphy et al., 2002). Unlike much of the remainder of Yukon-Tanana and Slide Mountain terranes in the northern Cordillera of Yukon and Alaska, the Finlayson Lake district lies in the region affected by Quaternary glaciations (Duk-Rodkin, 1999), therefore boasting some of the best exposures of these generally poorly exposed terranes�and�presenting�an�excellent�opportunity�to�gain�insight�into�their nature and evolution. Indeed, some of the early competing models of the origin and evolution of Yukon-Tanana terrane (cf. Tempelman-Kluit, 1979; Mortensen and Jilson, 1985; Mortensen, 1992a, see also discussion by Colpron et al.,� this�volume),�which�informed subsequent debates about the terrane (Mortensen, 1992a; Hansen and Dusel-Bacon, 1998; Mihalynuk et al.,�1999;�Hansen�and�Oliver, 1999), were based largely on interpretations of reconnaissance mapping and geochronological data from this better exposed part of the�terrane.

The Finlayson Lake district encompasses the region underlain by the stratigraphic successions that host the five volcanogenic mas-sive sulphide (VMS) deposits discovered, or re-discovered, begin-ning in 1994 (Figs. 3, 4). The deposits include the new discoveries

at Kudz Ze Kayah, GP4F and Ice, as well as definition of reserves at the previously known Fyre Lake and Wolverine Lake occurrences (see Hunt, 2002 for a recent summary). The district is notable for the age range and diversity of its deposits. Fyre Lake is Late Devonian in age and associated with chloritic phyllite and greenstone of boni-nitic composition; Kudz Ze Kayah, GP4F and Wolverine Lake are Late Devonian and Early Mississippian in age and associated with alkalic (A-type) felsic metavolcanic host rocks; and Ice occurs in Lower Permian basalt of mid-ocean ridge basalt (MORB) composi-tion� (Piercey,�2001;�Piercey�et al., 1999, 2001a, b, 2002a, b). The deposits occur in both Yukon-Tanana and Slide Mountain terranes, with Fyre Lake, Kudz Ze Kayah, GP4F and Wolverine Lake occur-ring in the former and Ice occurring in the latter.

At the time of the discoveries, the area had been mapped twice at�1:250,000-scale�(Wheeler�et al., 1960; Tempelman-Kluit, 1977) and has been the focus of a doctoral thesis that included 1:125,000-scale regional mapping and U-Pb geochronology (Mortensen, 1983). These data formed the bases for two different models of the tectonic evolution of the region. Tempelman-Kluit (1979) proposed that the rocks in the district represented the highly deformed - to the extent that original stratigraphy was inferred to be unrecognizable - and imbricated remnants of an early Mesozoic ensialic arc, subduction complex and marginal ocean basin that lay outboard of the North American continental margin in the late Paleozoic and early Mesozoic; and accreted to the margin during and after the early Mesozoic closure of the marginal basin by subduction beneath the arc. While acknowledging the deformed and imbricated character

B.C.YT

NW

T

YT

63°N

128°W

59°N

140°

W

67°N

160°

W

56°N

128°W

Ak

YT64°N 13

2°W 122°W

60°N

57°N

56°N

140°

W

59°N

124°W124°W

Tintina

Kaltag

Denali

Tintina

Ak

Ak

YT

B.C.

B.C

.

YT

NW

TYT

B.C.YT

B.C

.A

k

Wh

FbFb

WL

Wh

D

FbFb

WL

DenaliDenali

ST+

CC

ST+

CC

PacificOcean

limitlimit ofof

Cordilleran

Cordilleran

easterneastern

deformation

deformation

Gulf ofAlaskaST

+CC

ee

E

E

EE

EE

b

b

ee

E

E

EE

E

Ebb

FinlaysonLake

FinlaysonLake

Delta

Bonnifield

Ambler

Gataga

Tulsequah

Tulsequah

MacmillanPass

MacmillanPass

Gataga

Delta

Bonnifield

C A N A D AC A N A D A0 300

km

Scale 0 300km

Scale

PALEOZOIC PERICRATONICASSEMBLAGES

CONTINENT MARGINASSEMBLAGES

Devonian - PermianStikine assemblage

Devonian - Jurassicoceanic assemblages

PermianKlondike Schist

Pennsylvanian - PermianKlinkitDevonian - Mississippianarc assemblages

Neoproterozoic - Devonian basinal facies

Neoproterozoic - Miss.rift and basinal facies

Proterozoic - Devonian platformal facies

Neoproterozoic - Paleozoicother cont. margin assembl.

Devonian - Mississippianmineral districts

A) B)

Yukon-Tanana terrane

Figure 1. Late Paleozoic to early Mesozoic tectonic assemblages of the northwestern North American Cordillera, (A) currently and (B) before displacement on the Tintina fault. The Finlayson Lake district and other mineral districts are indicated with black stars. Occurrences of high-pressure/low-temperature metamorphic rocks are indicated by letters: E, Permian eclogite; e, Mississippian eclogite; b, blueschist, age unknown. Communities, indicated by black dots: Wh, Whitehorse, Yukon; WL, Watson Lake, Yukon; D, Dawson, Yukon; Fb, Fairbanks, Alaska.

78

Murphy et al.

of the rocks of the region, Mortensen and Jilson (1985) and Mortensen (1992a) proposed that much of the region was stratigraphically intact and comprised primarily volcanic and intrusive rocks of a southwest-facing mid-Paleozoic ensialic arc, its pre-Late Devonian sialic base-ment, Pennsylvanian to Permian limestone and quartzite and mid-Permian volcanic and plutonic arc rocks produced by subduction under the northeastern margin of the terrane. These rocks were de-formed prior to the Late Triassic and imbricated with mid-Paleozoic ophiolite (Slide Mountain terrane) after the Late Triassic, in part along a transpressive suture called the Finlayson Lake fault zone. The resultant structural stack was subsequently thrust onto the North American continental margin before the mid-Cretaceous.

The geoscience data and interpretations that were available at the time of the discoveries of the VMS deposits were insufficient to account for the diversity of the deposits in the area or to relate them in such a way as to be useful for further mineral exploration. To ad-dress this situation, a new generation of 1:50,000-scale geological mapping�and�integrated�geochemical,�metallogenic,�geochronologi-cal and paleontological research was initiated in 1996. This paper

summarizes what has been learned about the geological setting and evolution of the Finlayson Lake district and environs in this latest generation of research. It describes a new provisional lithostratigra-phy of both Yukon-Tanana and Slide Mountain terranes and affiliated overlap assemblages and infers environments of deposition. It pro-poses a model of the tectonic evolution of the region that has elements in common with both previous models but differs from them in several important ways. In particular, this new work documents a metallogenically important mid- to late Paleozoic back-arc realm that includes parts of both Yukon-Tanana and Slide Mountain ter-ranes. It also documents relationships between the two terranes that challenge how terranes are defined.

STRUCTURAL AND STRATIGRAPHIC FRAMEWORK OF THE FINLAYSON LAKE DISTRICTThe Finlayson Lake district comprises variably deformed and meta-morphosed lower greenschist to amphibolite facies metasedimentary and metavolcanic rocks and affiliated metaplutonic suites. The dis-

Fig. 5

Fig. 6

Fig. 16

1 23

4

VMS DEPOSITS

Kudz Ze Kayah

Fyre Lake

Wolverine

Ice

GP4F

1

2

3

4

5

5

0 20

kilometres

132°00'

131°

15'

62°00'

61°00'

INCONNUINCONNU

MCTMCT

MCTMCT

JCFJCF

JCF

JCF

JCFJCF

JCFJCF

BCT

FAULT

CREEK

JULES

NRFNRF

NRFNRF

CLTCLT

CLTCLT

INCONNU

INCONNU

THR

UST

THR

UST

Finlayson Lake

Finlayson Lake

FrancesLake

FrancesLake

Wolverine Lake

Wolverine Lake

FireLakeFireLake

Campbell HighwayCampbell Highway

YUKON

Finlayson Lake(105G)

Frances Lake(105H)

Ross River~ 40 km

Watson Lake~ 110 km

TINTINA

FAULT

Mississippianeclogite (KMC)

Triassic rocks

Paleozoic rocks

North American ContinentalMargin Sequence

Slide Mountain terrane

Triassic rocks deposited onSlide Mountain terrane

Permian - Triassic(?) Simpson Lakegroup deposited on Slide Mountain terrane

Allochthonous Elements

Big Campbell thrust sheet

Money Creek thrust sheet

Cleaver Lake thrust sheet

Fortin Creek group

Campbell Range formation, mafic andultramafic metaplutonic rocks, andGatehouse formation


Volcanic rocks

Plutonic rocks

Post-accretionary Mesozoic and Tertiary rocks

BIG CAMPBELLWINDOW

BIG CAMPBELLWINDOW

THRUSTTHRUST

PellyPelly RiverRiver

THRUST

MONEY CREEK

THRUST

MONEY CREEK

Figure 2. Tectonostratigraphic subdivisions of the Finlayson Lake district. Numbered locations refer to volcanogenic massive sulphide deposits. Locations of Figures 5, 6 and 16 are indicated by polygons. NRF - North River fault; JCF - Jules Creek fault; CLT - Cleaver Lake thrust fault; MCT - Money Creek thrust fault; BCT - Big Campbell thrust fault; KMC - Klatsa metamorphic complex.

� 79


trict is characterized by a central core of higher grade metamorphic rocks (to lower amphibolite facies) surrounded by lower grade, low greenschist facies rocks. This relatively simple metamorphic distri-bution is a consequence of Cretaceous dynamothermal events (Murphy, 2004), not described here, that overprint and partly obscure a complex Paleozoic and early Mesozoic history, which is the topic of this paper.

In spite of locally intense deformation, regionally extensive stratigraphic units have been defined by mapping, and protoliths have been determined from locally well-preserved primary features and geochemical characteristics. The stratigraphic nature of many contacts has been inferred from a lack of convincing evidence for faulting, such as enhanced brittle or ductile deformation or contra-dictory (older over younger) geochronological or biochronological data. Stratigraphic facing directions have been determined from a combination of preserved primary indicators, absolute ages deter-mined by U-Pb geochronology and biochronology and relative ages determined from cross-cutting relationships.

Rocks assigned to Yukon-Tanana terrane lie between the Tintina fault and the Jules Creek fault, the main boundary between Yukon-Tanana and Slide Mountain terranes (Fig. 2; Murphy et al.,�2002).�Yukon-Tanana terrane has been subdivided into a number of provi-sionally named fault- and unconformity-bound groups and forma-tions (Figs. 3, 4, Murphy et al.,�2001;�Murphy�et al., 2002 [Note that a forthcoming bulletin by the senior author will establish formal status for these units. All formation and group names in this paper are therefore provisional.]). The structurally deepest rocks which are clearly part of Yukon-Tanana terrane are pre-Late Devonian to Early Permian rocks of the Big Campbell thrust sheet, bound below by the post-Late Triassic Big Campbell thrust fault and above by the Early Permian Money Creek thrust fault. The Money Creek thrust sheet also comprises pre-Late Devonian to Early Permian rocks, but of a different depositional environment and geochemical character than the Big Campbell sheet. The Money Creek thrust sheet is bound above by the Cleaver Lake thrust fault, along which a third assem-blage of Late Devonian and Early Mississippian rocks as well as retrogressed eclogite (Erdmer et al., 1998; Devine et al.,�this�volume),�were emplaced in the Early Permian.

Slide Mountain terrane comprises Mississippian (and possibly older) to Lower Permian carbonaceous metaclastic rocks and chert, Lower Permian basalt and chert, Early Permian mafic and ultramafic metaplutonic rocks, and Middle Permian limestone and quartzite. Rocks assigned to Slide Mountain terrane occur primarily between the Jules Creek fault and the Inconnu thrust fault, the fault boundary between the North American continental margin sequence and the allochthonous terranes (Fig. 2; Murphy et al.,� 2002).� Lower� and�Middle Permian rocks of Slide Mountain terrane also depositionally overlie Yukon-Tanana terrane south of the Jules Creek fault, provid-ing a firm linkage between the two terranes by the Early Permian. Clasts of Yukon-Tanana terrane occur in upper Middle Permian (-Triassic?) conglomerate deposited on Slide Mountain terrane, further affirming the linkage between the two terranes by that time. Finally, as observed in the Big Campbell window (Figs. 2, 3), rocks of Slide Mountain terrane occur in the footwall of the Big Campbell

thrust fault, structurally beneath rocks of Yukon-Tanana terrane in the Big Campbell thrust sheet. In the window, meta-basalt and ser-pentinized ultramafic rock of Slide Mountain terrane are overlain (depositionally?) by, and imbricated with, Upper Triassic shale and siltstone.

Slide Mountain and Yukon-Tanana terranes and overlapping rocks are juxtaposed against Triassic shale and siltstone and older rocks of the North American continental margin sequence along the Inconnu thrust fault (Figs. 2, 3). The presence of Triassic rocks be-neath both the Big Campbell and Inconnu thrust faults suggests that the rocks of Slide Mountain terrane in the Big Campbell window occur in a duplex structure related to the Inconnu thrust.

The following summary starts with descriptions and paleogeo-graphic interpretations of first Yukon-Tanana terrane, then Slide Mountain terrane and finally the affiliated overlap assemblages. It proceeds in order of age and encompasses both the rock units and structures within each interval. The discussion concludes with a summary of the geodynamic evolution of the allochthonous rocks of the Finlayson Lake district.

YUKON-TANANA TERRANE

Local Basement CompositionThe mid- to late Paleozoic supracrustal rocks of Yukon-Tanana ter-rane in the Finlayson Lake district were deposited on and intruded into a pre-Late Devonian crustal basement, which is not exposed in the area but which can be characterized as generally sialic by isotopic and geochemical data from younger felsic igneous rocks (Mortensen, 1992b; Grant, 1997; Piercey et al.,�2003).�With�local�exceptions,�εNd

t�

from felsic igneous rocks is typically highly negative and the rocks have Early to Middle Proterozoic T

DM�ages�(Mortensen,�1992a;�Grant�

et al.,�1996;�Piercey�et al., 2003). Similarly, the Sr and Pb isotopic composition of felsic igneous rocks and the Pb isotopic compositions of sulphide minerals from syngenetic mineral occurrences are highly radiogenic�(Mortensen,�1992a;�Grant,�1997;�Mortensen�et al.,�this�volume). Inherited Pb in zircons from numerous samples of felsic metavolcanic and metaplutonic rocks indicates the presence of a basement source area with an Early to Middle Proterozoic average age�(Mortensen,�1992a;�Mortensen�et al., this volume). All of these data suggest that felsic igneous rocks in the district were either de-rived from older sialic crustal material or were contaminated by older sialic crustal material during passage of the melt through the crust.�

In contrast to the highly evolved nature of the felsic igneous rocks in the district, the Nd isotopic signatures of mafic metavolcanic rocks are more variable, ranging from –5 to nearly +9 (Fig. 5), sug-gesting the presence of small domains of more primitive character (Piercey� et al., 2004). The rocks with near chondritic to slightly evolved signatures generally occur in areas where the felsic rocks are highly evolved, suggesting that the mafic rocks were contami-nated during their passage through the sialic crust. The rocks with the most primitive signatures cluster in an east-west belt across the central part of the district, defining a region either underlain by more primitive�lithosphere�or�in�which�magma�moved�through�sialic�crust�

80

Murphy et al.

12

3

4

VM

S D

EP

OS

ITS

Kud

z Z

e K

ayah

Fyr

e La

ke

Wol

verin

e

Ice

GP

4F5

020

kilo

met

res

132°

00'

62°0

0'

130°

00'

61°0

0'

61°4

5'

INC

ON

NU

INC

ON

NU

MC

TM

CT

MC

TM

CT

BIG

CA

MP

BE

LL

WIN

DO

WB

IG C

AM

PB

EL

LW

IND

OW

JCF

JCF

JCFJCF

JCFJCF

JCF

JCF

BCT

FAU

LT

CR

EE

K

JUL

ES

NR

FN

RF

CLT

CLT

CL

TC

LT

TH

RU

STT

HR

UST

INCONNU

INCONNU

THRUSTTHRUST

TH

RU

ST

MO

NE

Y C

RE

EK

TH

RU

ST

MO

NE

Y C

RE

EK

Pel

lyP

elly

Riv

erR

iver

Fin

lays

on

La

keF

inla

yson

Lake

Fra

nces

Lake

Fra

nces

Lake

Wol

verin

e

Lak

e

Wol

verin

e

Lak

e

Fir

eLa

keF

ire

Lake

Cam

pbel

l Hig

hway

Cam

pbel

l Hig

hway

YU

KO

N

Fin

lays

on L

ake

(105

G)

Fra

nces

La

ke(1

05H

)

Ros

s R

iver

~ 40

km

Wat

son

Lake

~ 11

0 km

TINTIN

A

FAU

LT

Mis

siss

ippi

anec

logi

te (

KM

C)

Nor

th K

lippe

n

Mon

ey K

lippe

1 2 3 4 5

81


ultr

amaf

ic a

nd m

afic

intr

usio

ns

poly

mic

tic c

ongl

omer

ate,

san

dsto

ne,

silts

tone

, maf

ic a

nd fe

lsic

vol

cani

c ro

cks,

lim

esto

ne

limes

tone

and

qua

rtzi

te

basa

lt an

d va

ricol

oure

d ch

ert

dark

phy

llite

and

san

dsto

ne, c

hert

, ch

ert-

pebb

le c

ongl

omer

ate,

dia

mic

tite

dark

phy

llite

and

che

rt, v

aric

olou

red

cher

t, ch

ert-

pebb

le c

ongl

omer

ate,

sa

ndst

one,

lim

esto

ne, f

elsi

c an

d m

afic

m

etav

olca

nic

rock

s

YU

KO

N-T

AN

AN

A T

ER

RA

NE

YU

KO

N-T

AN

AN

A T

ER

RA

NE

PO

ST

- Y

TT

/ S

MT

A

MA

LG

AM

AT

ION

SL

IDE

MO

UN

TAIN

TE

RR

AN

E

SL

IDE

MO

UN

TAIN

TE

RR

AN

E

LE

GE

ND

INT

RU

SIV

E R

OC

KS

INT

RU

SIV

E R

OC

KS

LAY

ER

ED

RO

CK

S

LAY

ER

ED

RO

CK

S

SIM

PS

ON

LA

KE

GR

OU

P

Cam

pbel

l Ran

ge fo

rmat

ion

Gat

ehou

se fo

rmat

ion

Mon

ey C

reek

form

atio

n

mas

sive

bio

clas

tic li

mes

tone

Whi

tefis

h lim

esto

ne

Ear

ly P

erm

ian

gran

ite, q

uart

z m

onzo

nite

au

gen

gran

ite

Late

Dev

onia

n to

Ear

ly M

issi

ssip

pian

Low

er P

erm

ian

Low

er t

o M

iddl

e P

erm

ian

Low

er P

erm

ian

Upp

er M

issi

ssip

pian

gree

n an

d pi

nk c

hert

, lim

esto

ne, s

ands

tone

,co

nglo

mer

ate,

maf

ic m

etav

olca

nic

rock

s

undi

ffere

ntia

ted

Whi

te L

ake

and

Kin

g A

rctic

form

atio

ns

Upp

er M

issi

ssip

pian

to m

id-P

enns

ylva

nian

mas

sive

bio

clas

tic li

mes

tone

Fin

lays

on C

reek

lim

esto

ne

Mid

-Pen

nsyl

vani

an to

Low

er P

erm

ian

inte

rmed

iate

, fel

sic

and

maf

ic v

olca

nic

rock

s, s

ands

tone

, che

rt, l

imes

tone

Tuch

itua

Riv

er fo

rmat

ion

Low

er M

issi

ssip

pian

undi

ffere

ntia

ted

maf

ic a

nd fe

lsic

vo

lcan

ic r

ocks

and

dar

k cl

astic

roc

ks

of th

e F

ire L

ake,

Kud

z Z

e K

ayah

and

W

ind

Lake

form

atio

ns

gran

ite, q

uart

z m

onzo

nite

, gr

anod

iorit

e

SIM

PS

ON

RA

NG

E P

LUT

ON

IC S

UIT

E

GR

AS

S L

AK

ES

PLU

TO

NIC

SU

ITE

ultr

amaf

ic a

nd m

afic

intr

usio

ns,

Big

Cam

pbel

l and

Cle

aver

Lak

eth

rust

she

ets

GR

AS

S L

AK

ES

GR

OU

P

calc

-alk

alin

e ba

salt,

rhy

olite

, che

rt

and

volc

anic

-der

ived

san

dsto

ne

Cle

aver

Lak

e fo

rmat

ion

Nor

th R

iver

form

atio

n

fels

ic to

inte

rmed

iate

met

avol

cani

c ro

cks

and

carb

onac

eous

phy

llite

Wat

ers

Cre

ek fo

rmat

ion

Upp

er D

evon

ian

to L

ower

Mis

siss

ippi

an

Pre

-Upp

er D

evon

ian

quar

tzos

e m

etac

last

ic r

ocks

, mar

ble

and

non-

carb

onac

eous

pel

itic

schi

st

undi

ffere

ntia

ted

maf

ic a

nd fe

lsic

vo

lcan

ic r

ocks

and

dar

k cl

astic

roc

ks

WO

LVE

RIN

E L

AK

E G

RO

UP

FO

RT

IN C

RE

EK

GR

OU

P

Car

boni

fero

us to

Per

mia

n?

undi

ffere

ntia

ted

intr

usio

ns

undi

ffere

ntia

ted

volc

anic

roc

ks

Mes

ozoi

c an

d C

enoz

oic

grey

sha

le, s

iltst

one

and

limes

tone

Tria

ssic

Per

mia

n -

Tria

ssic

dark

sha

le, s

iltst

one

and

limes

tone

Tria

ssic

NO

RT

H A

ME

RIC

AN

C

ON

TIN

EN

TAL

MA

RG

IN

undi

ffere

ntia

ted

form

atio

ns o

f Sel

wyn

B

asin

, McE

voy

Pla

tform

, Ear

n G

roup

an

d M

t. C

hris

tie F

orm

atio

n

Pal

eozo

ic

Fig

ure

3. G

eolo

gica

l map

of t

he F

inla

yson

Lak

e di

stri

ct a

nd e

nvir

ons.

Fau

lt ab

brev

iati

ons

as in

Fig

ure

2.

82

Murphy et al.

with only limited contamination. In this region, the Fire Lake forma-tion is made up of primitive-arc boninites, the products of melting of highly refractory mantle source regions that have been variably metasomatized by subducted slab fluids (Piercey et al.,� 2001a).�Boninites are typically found in intra-oceanic suprasubduction zone settings� (Piercey� et al., 2001a and references therein), thus their presence in the Finlayson Lake district likely defines that part of Yukon-Tanana terrane that was underlain by basement of more primitive�composition.�

Pre-Upper Devonian North River FormationThe oldest exposed rock unit in the Finlayson Lake district, occur-ring in both the Big Campbell and Money Creek thrust sheets, is the pre-Upper Devonian North River formation (Figs. 3, 4). This unit consists primarily of quartzose psammite, non-carbonaceous me-tapelite and locally important marble, calc-schist and felsic meta-volcanic members at or near its top. The age of the North River for-mation is constrained only to be pre-Late Devonian, older than the stratigraphically overlying Late Devonian Fire Lake formation and cross-cutting Early Mississippian intrusions.

Late Devonian and Early Mississippian Magmatism and SedimentationThe Late Devonian to Early Mississippian period in the Finlayson Lake district is represented by three fault-bounded assemblages that formed in different depositional environments. From the structurally deepest levels in the core of the district outward these include: (1) the Grass Lakes and Wolverine Lake groups and affiliated metaplutonic rocks in the Big Campbell thrust sheet, (2) the Waters Creek and Tuchitua River formations and affiliated intrusions in the Money Creek thrust sheet, and (3) the Cleaver Lake formation and intrusions of the Cleaver Lake thrust sheet (Figs. 3, 4). Coarse-grained meta-morphic rocks with Early Mississippian cooling ages and character-istics suggestive of a high pressure/low temperature metamorphic regime (Erdmer et al., 1998; Klatsa metamorphic complex of Devine et al.,� this� volume)� also� occur� in� the� Cleaver� Lake� thrust� sheet.�Structural�considerations�suggest�that�the�rocks�in�the�Money�Creek�thrust sheet formed at least 45 km southwest of their current location with�respect�to�the�Grass�Lakes�and�Wolverine�Lake�groups�(Murphy�and Piercey, 2000b). The rocks of the Cleaver Lake thrust sheet in turn lay an unknown distance to the south-southwest from the rocks of the Money Creek thrust sheet. The Late Devonian and Early Mississippian period was metallogenically important as all the VMS deposits and occurrences in this part of Yukon-Tanana terrane formed during this interval (Figs. 3, 4).

Big Campbell Thrust SheetThe Grass Lakes group (Murphy et al.,�2002)�comprises�three�map�units, the Fire Lake, Kudz Ze Kayah and Wind Lake formations. The oldest unit, which directly overlies the North River formation, is the laterally extensive Upper Devonian Fire Lake formation, host of the Fyre Lake Cu-Co-Au VMS deposit (Murphy, 1998a; Foreman, 1998; Hunt, 2002). The Fire Lake formation comprises chloritic phyllite or schist (mafic volcanic and volcaniclastic rocks) and lesser

carbonaceous phyllite or schist and muscovite-quartz phyllite or schist (felsic volcanic or volcaniclastic rocks). The basal contact of the Fire Lake formation is generally sharp although local, possibly structural, intercalation of mafic schist with quartz-rich schist sug-gests a narrowly transitional contact. Bodies of mafic and variably serpentinized ultramafic metaplutonic rocks occur within the Fire Lake formation and in underlying rocks of the North River formation along�a�greater�than�115�km-long,�west-northwest-trending�corridor�(Fig. 3). These bodies occur as layer-subparallel, laterally tapering slabs within the Fire Lake formation and as discordant, dike-like bodies in the underlying North River formation. Although initially inferred to be allochthonous slices of ophiolite (Tempelman-Kluit, 1979; Mortensen and Jilson, 1985; Mortensen, 1992a), these bodies have been re-interpreted as intrusions - sills within the Fire Lake formation and dikes in the North River formation - based on their spatial association with the Fire Lake formation, their geometry and the lack of evidence for displacement along their generally sharp contacts (Murphy, 1998b).

Geochemically, the Fire Lake formation, the initial pulse of magmatism in the area, has attributes that generally indicate a rift setting but with a tendency to become more arc-like in a southerly direction. In the northern part of the Finlayson Lake district, chloritic phyllite of the Fire Lake formation is of basaltic composition with back-arc basin basalt (BABB), enriched mid-oceanic ridge basalt (E-MORB), niobium-enriched basalt (NEB), and Th-enriched NEB varieties, all typical of non-arc, rift-type settings (Fig. 6; Piercey, 2001;�Piercey�et al., 2004). In contrast, in the south, the majority of samples of the Fire Lake formation are boninite and island arc tho-leiite (IAT) in composition. This southwestward transition coincides with a lateral transition within the rocks of the Fire Lake formation from a slightly negative εNd

t�(-0.3)�value�to�slightly�to�moderately�

positive�εNdt values (+0.5 to +8.5; Fig. 5) and by dramatic increases

in thickness of the Fire Lake formation and in the volume of the in-tercalated mafic and ultramafic metaplutonic intrusions (Murphy, 1998b). The coincident increase in both volcanic thickness and amount of comagmatic intrusion has been attributed to down-to-the south synvolcanic normal faulting, a conclusion also supported by the presence of the Fyre Lake VMS deposit located along this trend (Murphy, 1998b; Murphy and Piercey, 2000a). These coincident transitions are attributed to rapid extension of crust with domains of more primitive and more evolved crust material and a southward change into subduction-fluid-fluxed mantle (Piercey et al.,�2001a).�

The age of the Fire Lake formation is constrained to be Late Devonian by two ca. 365 Ma U-Pb dates from the North Lakes metadiorite, one of the spatially associated intrusions inferred to be comagmatic with the Fire Lake formation (Table 1, Fig. 7; Table A1, Appendix 1 [see footnote 1]). Younger, stratigraphically overlying rocks are intruded by bodies of the Grass Lakes plutonic suite as old as 362.2 ± 3.3 Ma (Table 1, Fig. 8, Appendix 1).

The Fire Lake formation passes upward into a carbonaceous phyllite-dominated succession, with the felsic metavolcanic rocks that host the Kudz Ze Kayah and GP4F deposits in the lower part (Kudz Ze Kayah formation), and mafic metavolcanic rocks and quartzite in the upper part (Wind Lake formation; Murphy, 1998a).

83


? ?

383

376

342

311

360

327

314

306

Gzhelian

Kasimovian

Moscovian

Bashkirian

Frasnian

Fam

enni

an

DEV

ON

IAN

MIS

SISS

IPPI

ANPE

NN

SYLV

ANIA

N

380

370

360

350

340

330

320

310

300

290

Viséan

Tour

nais

ian

Serp

ukho

vian

PER

MIA

NTR

IASS

IC

280

270

260

250

240

230

220

210

Asselian

Tatarian

Sakmarian

Artinskian

Kungurian

KazanianUfimian

285

280

272269

264

300

253

200

Induan

Olenekian

Anisian

248

Ladinian

Carnian

Norian

Rhaetian

240.6244

231

221.6

205.5

?e

Mo

ney

Cre

ek

Inconnu

thrust

Inco

nn

u t

hru

st

Big Campbell thrust

Cle

aver

Lak

e th

rust

thru

st

358 Ma

Cam

pb

ell

Cam

pb

ell

Gra

ssL

akes

Fo

rtin

Mo

ney

Cle

aver

Wat

ers

Tu

chit

ua

WF

KMC

NR NR

KAWL

FC

Sim

pso

n

Wo

lver

ine

?

? ?

?

??

?

?

D

Thrusting

D

Jule

s C

reek

fau

lt

Big Campbell window

North

American

miogeoclinal

sequence

(undifferentiated)

Big Campbellthrust sheet

Money Creekthrust sheet

Cleaver Lakethrust sheet

N-MORBE-MORB >

Arc

N-MORB,

N-MORB

BAB

E-,N-MORB BAB

ArcALK

ALK

BAB

OIB

OIB

Arc

Arc

MORBBON

NEB

4

4

1

1

2

2

3

3

5

5

1

2

3

8

46

7

2425

26

2827

5

5

9

1011

17

15

16

1816

21

222023

19

12

13

14

F2

F4

F13

F16F17

F15

F14

F12

F8

F10

F3

F6,9

F7

F18

F19F20

F21

F23

F24

F25

F5

F1

F26

F11

Protolith Lithologies

Felsicintrusion

Chert, argillite

Intermediateintrusion

Basic volcanic rock

Intermediatevolcanic rock

Volcaniclasticrock

Conglomerate

Orthoquartzite

Sandstone,siltstone

Carbonaceousclastic rocks

LimestoneMaficintrusion

Felsic volcanic rock

Grit

Ultramaficrock

Exhalite

SymbolsFossil age (keyed toTables 4, 5, 8)

U-Pb age (keyed toTables 1, 2, 3, 6, 7)

Age of youngest detritalzircon (Table 1, Fig. 9)

Unconformity

Deformation

Kudz ZeKayah

GP4F

Wolverine

Fyre

Ice

Eclogite

D

e358 Ma

ArcBABBONN-MORBOIBE-MORBNEBALK

= island arc= back-arc basin = boninite= normal mid-ocean ridge basalt= ocean island basalt= enriched mid-ocean ridge basalt= niobium-enriched basalt= alkalic

Petrogenetic AffinitiesVMS Deposits

F7

Figure 4. Summary diagram illustrating the structural and stratigraphic relationships in the Finlayson Lake district. Numbers and num-bered symbols refer to points tabulated in Tables 1-8. KMC - Klatsa metamorphic complex; WF - Whitefish limestone; WL - White Lake formation; KA - King Arctic formation; FC - Finlayson Creek limestone; NR - North River formation. Time scale of Okulitch (2002).

84

Murphy et al.

0 20

kilometres

Slide Mountain terrane

LEGEND

Big Campbell thrust sheet

Money Creek thrust sheet

Cleaver Lake thrust sheet

Campbell Range formation

Fortin Creek group


Jules Creekfault

Money Creekthrust

Cleaver Lake thrust

TINTINA FAULT -1.6

+8.1

-5.0+1.6

-3.2+7.1

+2.6 +8.5 +0.5+5.1

+6.4+1.7

-0.3+6.9

+5.5

+7.1

+5.0

+3.3

-4.0+6.0

+5.5+3.6

+1.1

-2.8

+7.0

+2.2

Nd350 < 0

0 < Nd350 < +5

+5 < Nd350

131°

15’

131°

15’

61°15’61°15’

61°30’61°30’

131°

00’

131°

00’

Figure 5. Neodymium isotopic data from mafic magmatic rocks constraining the nature of the lithosphere underlying the mid-Paleozoic rocks of Yukon-Tanana terrane in the Finlayson Lake district (from Piercey et al., 2004; S.J. Piercey and R.A. Creaser, unpublished data).

0 20

kilometres

WL

FL

FrL

FL = Finlayson Lake

WL = Wolverine Lake

FrL = Fire Lake

Arc Suites

Boninite

Nb-enriched basalt

Transitional Nb-enriched basalt

Back-arc basin basalt

Island Arc Tholeiite

Non-Arc Suites

Grass Lakes group (includingFire Lake formation)

Mafic and ultramafic rocks

LEGEND

Ocean island basalt

ArcArc

ArcArc

Non-ArcNon-Arc

131°

30’

131°

30’

131°

15’

131°

15’

61°15’61°15’

61°30’61°30’

Figure 6. Compositional variability of the Fire Lake formation in the Finlayson Lake district (from Piercey et al., 2004). Dashed line de-limits the boundary between rocks with ‘arc’ geochemical signatures and those with ‘non-arc’ signatures.

85


Metavolcanic rocks in the Kudz Ze Kayah and Wind Lake formations have� within-plate� geochemical� signatures� (Piercey� et al., 2001b, 2002a). Felsic metavolcanic rocks of the Kudz Ze Kayah formation plot in the fields for within-plate felsic rocks on tectonic discrimina-tion diagrams, with predominantly A-type affinities (Piercey et al.,�2001b). Mafic metavolcanic rocks in the Wind Lake formation are weakly alkalic with signatures similar to ocean island basalt (OIB, Piercey�et al., 2002a). These signatures are attributed to ongoing rifting, following its onset in Fire Lake formation magmatism. The evolution from felsic to mafic magmatism in the upper part of the Grass Lake group is attributed to the onset of decompression melting of the mantle following thinning, rifting and partial melting of the overlying� continental� crust� (Piercey� et al.,� 2002a).� According� to�Piercey�et al.�(2003),�a�continental�crustal�signature�is�evident�in�the�

felsic rocks of the Kudz Ze Kayah formation (εNdt = -7.8) as are geo-

chemical indications of minor crustal contamination in the overlying mafic rocks (εNd

t = -2.8).

The ages of the Kudz Ze Kayah and Wind Lake formations are constrained to be younger than the ca. 365 Ma age of the Fire Lake formation and older than the 362.2 ± 3.3 Ma age of an intrusion of the Grass Lakes plutonic suite into the Wind Lake formation (Table 1, Fig. 8A, Table A1, Appendix 1).

The Grass Lakes group is intruded by texturally heterogeneous Late Devonian to Early Mississippian peraluminous granitic meta-plutonic rocks of the Grass Lake plutonic suite. The most common rock type of the Grass Lakes plutonic suite, making up the batholith-sized plutons in the area, is a foliated, locally megacrystic, potassium feldspar augen granite. Foliated, medium-grained and equigranular

Figure 7. U-Pb concordia diagrams for two samples of the North Lakes meta-diorite, inferred to be comagmatic with the Fire Lake forma-tion. See Appendix 1 for data tables and geochronological interpretations.

#1 Sample Unit Age (Ma) 2 σ Lithology / Relationship Source

INTRUSIONS INFERRED TO BE COMAGMATIC WITH THE FIRE LAKE FORMATION

1 HD-35 North Lakes metadiorite

365.0 ± 1.2 Foliated hornblende-biotite; intruded by augen-bearing phase of Grass Lakes plutonic�suite�

Mortensen (1992); this paper, Fig. 7A

96DM-065 North Lakes metadiorite

366.3 ± 10.2 Foliated hornblende-biotite; intruded by augen-bearing phase of Grass Lakes plutonic�suite�

this paper, Fig. 7B

GRASS LAKES PLUTONIC SUITE

2 98DM-088 un-named 362.2 ± 3.3 Foliated equigranular quartz monzonite; intrudes upper unit of Grass Lakes group


3 GG-19 un-named 359.9 ± 0.9 Foliated locally potassium feldspar megacrystic granitic to quartz monzonitic metaplutonic�rock;�intrudes�Grass�Lakes�group

Mortensen (1992); this paper, Fig. 8B

4 96DM-119 un-named 357.3 ± 2.8 Slightly foliated medium-grained equigranular granite; intrudes Grass Lakes group, augen phase of Grass Lakes plutonic suite and North Lakes meta-diorite

this paper, Fig. 8C

WOLVERINE LAKE GROUP

5 01DM-318 lower�part ca.�357.5 Youngest detrital zircons from quartzofeldspathic conglomerate unconformably overlying the Kudz Ze Kayah formation

this paper; Fig. 9

6 FV-21 lower�part 356.2 ± 0.9 Quartz-feldspar-muscovite schist intercalated with carbonaceous phyllite and quartzofeldspathic sandstone and conglomerate


7 P98-069A Fisher porphyry- middle�part

346.6 ± 2.2 Foliated quartz-feldspar porphyry intruding or extruding near top of middle part of Wolverine Lake group

Piercey (2001); this paper, Fig. 10B

8 GP4F-1 GP4F (porphyry) 346.9 ± 0.7 Foliated quartz-feldspar porphyry intruding Kudz Ze Kayah formation of the Grass�Lakes�group

this paper, Fig. 10C

9 98DM-GDR un-named� 347.3 ± 3.7 Hornblende-biotite granite — relationship with nearby coeval rocks of the lower Wolverine�Lake�group�unclear

this paper, Fig. 10D

1�Number is keyed to data points presented in Figure 4.

Table 1. U-Pb Zircon Geochronological Constraints, Big Campbell Thrust Sheet.

360

364

A

B

C

0.420 0.424 0.428 0.432 0.4360.056

0.057

0.058

350

400

450

500

550

600

650

700

750

A

BC

D

0.3 0.9 1.50.04

0.08

0.12

A B

86

Murphy et al.

granite and weakly to un-foliated, fine- to medium-grained and equigranular granite are less common. The latter intrudes across axial surfaces of recumbent isoclinal folds and is spatially associated with dikes that cut an earlier foliation, thereby defining a Devono-Mississippian episode of deformation in Yukon-Tanana terrane.

The Fire Lake and Kudz Ze Kayah formations are also intruded by an undated pluton of the metaluminous Simpson Range plutonic suite near the Tintina fault (Fig. 3). The Simpson Range plutonic suite comprises hornblende-biotite granodiorite, diorite and quartz monzonite and typically occurs in the Money Creek and Cleaver Lake�thrust�sheets.

The geochemical signatures, spatial distribution and U-Pb age range of intrusive rocks that cut the Grass Lakes group are similar to those of the metavolcanic rocks within the group (Piercey et al.,�2003). All samples of the Grass Lakes plutonic suite are geochemi-cally and isotopically nearly identical to felsic metavolcanic rocks of the Kudz Ze Kayah formation. According to Mortensen (1992a) and�Piercey�et al.�(2003),�the�plutons�plot�primarily�as�A-type�within-plate�granites�and�are�isotopically�evolved,�with�strongly�negative�εNd

t values. The single intrusion of the Simpson Range plutonic

suite affinity has not been evaluated geochemically; but if it has the volcanic arc geochemical signature typical of that suite (see below), then� the� intrusions� in� the� area� would� show� the� same� southward�transition from within-plate geochemistry to more arc-like geochem-istry as is exhibited by the Fire Lake formation.

The age of the Grass Lakes plutonic suite is constrained by three U-Pb dates (Table 1, Fig. 8, Table A1, Appendix 1). A sample of foli-ated equigranular granite that cuts the Wind Lake formation yielded a 362.2 ± 3.3 Ma date (Fig. 8A, Appendix 1). A sample of foliated K feldspar-megacrystic granite yielded a concordant date of 359.9 ± 1.0 Ma (Fig. 8B, Table A1, Appendix 1). A weakly foliated intrusion that cuts recumbent isoclinal folds yielded a date of 357.3 ± 2.8 Ma (Fig. 8C, Table A1, Appendix 1), constraining the age of the first regional deformation in the area.

The Wolverine Lake group overlies different units of the Grass Lakes group in different areas, implying an angular unconformity (Figs. 3, 4). The basal unit of the succession comprises quartz- and feldspar-pebble conglomerate, grit and sandstone and carbonaceous phyllite. It grades upward into a unit of carbonaceous phyllite, quartz- and feldspar-phyric felsic metavolcanic rocks, and rare chert and quartz sandstone (Murphy and Piercey, 1998, 1999a; Murphy et al.,�2001, 2002). The Wolverine Zn-Pb-Cu-Ag-Au VMS deposit occurs associated with pyrite-carbonate exhalite near the top of this middle unit, at a pronounced change in the character of the volcanic rocks (Murphy�and�Piercey,�1999a;�Bradshaw�et al.,�2001,�2003;�Piercey�et al., 2001b). The upper unit of the Wolverine Lake group comprises locally silicified aphyric rhyolite breccia, regionally extensive sili-ceous barite-magnetite exhalite, and at the top, massive mafic metavolcanic�rocks�(Bradshaw�et al., 2001, 2003). Volumetrically minor subvolcanic feldspar (+/- quartz) porphyry bodies cut the middle unit of the succession and underlying rocks (Murphy and Piercey, 1998, 1999a, b; Bradshaw et al.,�2003).�

The metavolcanic rocks of the Wolverine Lake group have geo-chemical and isotopic signatures indicating a second cycle of within-

320

360

400

440

480

520

560

A

BC

D

E

0.3 0.7 1.10.04

0.05

0.06

0.07

0.08

0.09

330

340

350

360

A

B

C

D

0.37 0.410.051

0.053

0.055

0.057

300

400

500

600

700

800

900

1000

1100

1200

AB

C

D

E

F

M1M2

0.0

0.04

0.08

0.12

0.16

0.20

206 P

b/23

8 U

207Pb/235U

98DM-088

GG-19

to 2.50 Ga

to 2.34 Ga

to 1.90 Ga

2-pt. regressions through D

D concordant @ 359.9 ± 0.9 Ma

weighted average of Pb/Pb agesof B-C-E

362.2 ± 3.3 Ma

96DM-119

average Pb/Pb age of 4 pts357.3 ± 2.8 Ma

A

B

C

0.0 1.0 2.0 3.0 4.0

Figure 8. U-Pb concordia diagrams for three samples of the Grass Lakes plutonic suite: (A) sample 98DM-88 intrudes the youngest formation of the Grass Lakes group, the Wind Lake formation; (B) sample GG-19 is a sample of a sill of granite emanating from one of the larger batholiths of the Grass Lakes suite; (C) sample 96DM-119 is from a granite that is weakly foliated yet discordant relative to the prominent foliation in the host rock. Its age therefore documents a Devono-Mississippian phase of deformation in Yukon-Tanana terrane. See Appendix 1 for analytical methods, data tables and geochronological interpretations.

87


plate magmatism, which culminated in full sea floor spreading (Piercey,�2001;�Piercey�et al., 2001b, 2002a, b, 2003). Felsic volcanic and subvolcanic intrusive rocks from the lower part of the group are remarkably similar to the Kudz Ze Kayah formation with primarily within-plate,�A-type�signatures�and�evolved�isotopic�signatures�in-dicative of partial melting of continental crust (Piercey et al., 2001b, 2003). Felsic volcanic rocks above the Wolverine deposit, near the top of the unit, differ in that they are subalkalic and plot in the vol-canic arc field on discrimination diagrams (Piercey et al., 2001b). They pass transitionally upwards into basalt of primarily normal mid-ocean ridge basalt (N-MORB) affinity. Piercey et al. (2001b) attribute the progression from felsic A-type to felsic arc compositions to either a reduction in the temperature of melting of the continental crust or to mixing of partial melts of continental crust with high-field-strength-element-depleted mafic material; eventually pure mafic melts were erupted.

U-Pb geochronological data from igneous rocks and detrital zircons show that deposition of the Wolverine Lake group started at ca. 357 Ma and persisted to at least 347 Ma (Table 1; Figs. 9, 10; Appendices 1, 2). Detrital zircons from the basal conglomerate are as� young� as� ca. 358 Ma (Fig. 9, Table A3, Appendix 2 [see foot-note 1]). A 356.2 ± 0.9 Ma date was obtained from felsic metavolcanic rocks intercalated with the basal conglomerate (Fig. 10A, Appendix 1). Felsic metavolcanic rocks and subvolcanic intrusions in the footwall of the Wolverine deposit and intruding older stratig-raphy� elsewhere� in� the� area� are� ca. 347 Ma (Figs. 10B, C, D; Appendix�1).�

Money Creek Thrust SheetStratigraphically overlying the North River formation in the Money Creek thrust sheet are felsic and minor mafic or intermediate meta-volcanic rocks, carbonaceous phyllite, bedded barite, quartzite, quartz-pebble conglomerate and chert of the Waters Creek formation (Fig. 4). Felsic metavolcanic rocks of the Waters Creek formation are hornblende-phyr ic, and locally quar tz and feldspar porphyritic.�

The Waters Creek formation is intruded by sills or transposed dikes of locally megacrystic metaporphyry, which are common around a large unnamed foliated pluton of the older phase of the Simpson Range plutonic suite. Composed of variably megacrystic hornblende-biotite granodiorite, the pluton and porphyry sheets re-semble the hornblende-phyric rocks of the Waters Creek formation, suggesting that the pluton may be a shallow subvolcanic feeder to the volcanic rocks. The Waters Creek formation is also intruded by the Tuchitua River pluton, a weakly foliated to unfoliated body of massive, equigranular, hornblende-biotite granodiorite, which is part of a younger phase of the Simpson Range plutonic suite.

Geochemical and isotopic data from volcanic rocks in the Waters Creek formation are limited, and intrusions of the older phase of the Simpson Range plutonic suite have not been evaluated geo-chemically. One sample of mafic metavolcanic rock from the Waters Creek formation is Nb-enriched basalt of non-arc affinity (Piercey et al.,�2001a).�Grant�(1997)�reported�highly�evolved�εNd

t�signatures�

207Pb/235U

Age of youngest detritalzircon: ca. 357.5 Ma

Detrital zircon age distributionprobability plot

C

0 500 1000 1500 2000 2500 3000

Detrital zircon age (Ma)

Rela

tive

Prob

abili

ty

2800

2400

2000

1600

1200

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0 4 8 12 16 20

data-point error ellipses are 68.3% confidence

480

440

400

360

320

280

240

0.03

0.04

0.05

0.06

0.07

0.08

0.2 0.3 0.4 0.5 0.6

B

A

01DM-318

206 P

b/23

8 U

data-point error ellipses are 68.3% confidence

Figure 9. U-Pb data for detrital zircon grains from the basal clastic unit of the Wolverine Lake group. (A) concordia diagram showing all zircon analyses; (B) concordia diagram for the zircons plotting in the early to mid-Paleozoic part of the concordia diagram; (C) probability plot illustrating the range of probable ages of detrital zircons in the sample. The age of the youngest set of zircons (ca. 357 Ma) provides a maximum age for the basal clastic unit of the Wolverine Lake group. See Appendix 2 for analytical methods and data tables.

88

Murphy et al.

(εNdt >-13.1) from siliceous carbonaceous phyllite at three locations

in the Waters Creek formation.The age of the Waters Creek formation is constrained to be Late

Devonian by U-Pb dates on felsic metavolcanic rocks and cross-cut-ting intrusions (Table 2). A 360.8 ± 0.8 Ma zircon date has been ob-tained from felsic metavolcanic rocks in the formation (Fig. 11, Appendix 1). The Tuchitua River pluton, which intrudes the youngest chert member of the formation, is 356.9 ± 0.6 Ma (Fig. 12B, Appendix�1).

The Waters Creek formation is stratigraphically overlain by the Tuchitua River formation, which comprises slightly foliated, prima-rily intermediate and lesser felsic volcanic, volcaniclastic and epi-clastic rocks. Relatively weakly deformed rocks of the Tuchitua River formation overlie different, more highly deformed members of the Waters Creek formation in different places, indicating that the base of the Tuchitua River formation is an angular unconformity.

The Tuchitua River formation and underlying rocks are intruded by weakly to unfoliated hornblende-biotite granodiorite and granite of a younger phase of Simpson Range plutonic suite (Mortensen, 1992a;�Grant�et al., 1996; Grant, 1997). The less highly strained na-ture of both the volcanic and plutonic rocks suggest that they both postdated a phase of regional deformation. As well, their composi-tional similarity suggests that the plutons may be the subvolcanic feeders to the volcanic rocks (Mortensen, 1992a).

Geochemical and isotopic data from the Tuchitua River forma-tion�are�limited.�Metavolcanic�rocks�have�typical�volcanic�arc�geo-chemical�signatures�(Grant�et al.,�1996;�Grant,�1997;�Piercey�et al.,�this volume). One sample reported by Grant (1997) yielded a mod-erately�negative�εNd

t (-11.4), suggesting that the volcanic arc was

ensialic.�Similarly, granitoids of the Simpson Range plutonic suite have

geochemical signatures typical of a volcanic arc setting (Grant et al.,�

206 P

b/23

8 U

360

400

440

480

520

560

ABC

D

E

FGH

L

0.050

0.058

0.066

0.074

0.082

0.090

332

336

340

344

348

352

356

A

BC

D

E

F

0.38 0.40 0.42 0.440.052

0.054

0.056

320

330

340

350

AB

C

D

0.049

0.051

0.053

0.055

0.057

P98-069A

GP4F-1 98DM-GDR

A & F concordant@ 346.9 ± 0.7 Ma

3 fractions concordant@ 346.6 ± 2.2 Ma

347.3 ± 3.7 Maaverage Pb/Pb age of A & B

B

C D

360

370

A

B

C

D

0.056

0.058

D concordant @ 356.2 ± 0.9 Ma

FV-21

A0.37 0.45 0.53 0.61 0.69 0.77

0.36 0.40

0.41 0.43 0.45

207Pb/235UFigure 10. U-Pb concordia diagrams for two samples of felsic metavolcanic rocks in the Wolverine Lake group and two coeval sub-volcanic intrusions. (A) sample FV-21, felsic metavolcanic rock from near base of the succession; (B) sample P98-098B (Fisher porphyry), felsic volcanic or sub-volcanic porphyry found near the middle of Wolverine Lake group; (C) GP4F-1, porphyritic felsic intrusion into the Kudz Ze Kayah formation; (D) 98DM-GDR, hornblende granite intruding the North River formation. See Appendix 1 for analytical methods, data tables and geochronological interpretations.

89


1996;�Grant,�1997;�Piercey�et al.,�2003).�All�studied�intrusions�in�the�Money Creek thrust sheet are hornblende-bearing, calc-alkalic, and I-type and plot in the volcanic arc field on tectonic discrimination diagram. Isotopic data from the suite yield uniformly negative εNd

t�

values, affirming the ensialic nature of the arc basement (Grant, 1997;�Piercey�et al.,�2003).

The age of the Tuchitua River formation is constrained by U-Pb dates on felsic volcanic rocks and possibly comagmatic rocks of the Simpson Range plutonic suite (Table 2). Muscovite-quartz phyllite in the upper part of the Tuchitua River formation of inferred felsic volcanic or volcaniclastic protolith yielded a 344.5 ± 2.5 Ma zircon date (Fig. 13A, Appendix 1). Rhyodacitic tuff breccia yielded a 352.5 ± 2.6 Ma zircon date (Fig. 13B, Appendix 1). Coherent, conformable (flow?) and discordant (dike?) quartz feldspar porphyry overlap in age�at�ca. 347 Ma (Fig. 13C, D; Appendix 1). The Hasselberg Lake

and Tuchitua River plutons are 357.9 ± 1.3 Ma and 356.9 ± 0.6 Ma, respectively (Fig. 12A, B; Appendix 1).

Cleaver Lake Thrust SheetThe Cleaver Lake thrust sheet is only locally preserved as klippen. These include the Money and North klippen of Tempelman-Kluit (1979), and an isolated unnamed klippe in the Campbell Range southwest of Frances Lake (Figs. 3, 4). The North klippen comprise mafic and serpentinized ultramafic rocks that are of unknown age but are inferred to be coeval with similar rocks in the Money klippe to the south. The Money klippe consists of unfoliated volcanic rocks of the Cleaver Lake formation and spatially associated and probably comagmatic intrusions, and a cross-cutting hornblende-biotite quartz monzonite and granite intrusion belonging to the youngest phase of the Simpson Range plutonic suite. The Campbell Range klippe, the Klatsa metamorphic complex of Devine et al.�(this�volume),�is�made�up of retrograded eclogite (Erdmer et al., 1998; Devine, et al.,�this�volume) and serpentinized ultramafic rock and meta-leucogabbro.

The Cleaver Lake formation comprises pillowed and fragmental basalt with lesser rhyolite, chert and greywacke. Like the Fire Lake formation, with which these rocks were originally correlated (Piercey and Murphy, 2000), this basalt-dominated unit is spatially associated with probably comagmatic gabbro and ultramafic rock. The Cleaver Lake formation is also spatially associated with quartz porphyry intrusions which locally show magma mingling textures with basaltic dikes that are inferred to be feeders to the undeformed basalt in that sequence (Piercey and Murphy, 2000). The quartz porphyry intrusion is itself inferred to be a subvolcanic feeder to rhyolite flows in the Cleaver Lake formation.

The volcanic rocks of the Cleaver Lake formation and comag-matic and cross-cutting intrusions of the Cleaver Lake thrust sheet have geochemical signatures of typical volcanic arc rocks. The Cleaver Lake formation comprises calc-alkaline basalt and rhyolite, and island arc tholeiitic basalt and rhyolite (Grant et al.,�1996;�Grant,�1997;�Piercey�et al., 2001a, 2003). Samples of the youngest phase of the Simpson Range plutonic suite are calc-alkalic and plot exclusively


WATERS CREEK FORMATION

10 FV-27 middle�part 360.8�zircon

± 0.8 Muscovite-quartz schist Mortensen (1992); this paper; Fig. 11

SIMPSON LAKE PLUTONIC SUITE

11 SL-45 Hasselberg Lake pluton

357.9�titanite

± 1.3 Hornblende-biotite granodiorite, may be comagmatic with part of the Tuchitua River formation

Mortensen (1992); this paper; Fig. 12A

12 TRP-22 Tuchitua River pluton 356.9�zircon

± 0.6 Hornblende-biotite granodiorite, intrudes Waters Creek formation, may be comagmatic with part of the Tuchitua River formation

Mortensen (1992); this paper; Fig. 12B

TUCHITUA RIVER FORMATION

13 01DM-238 344.5�zircon

± 2.5 Muscovite-quartz phyllite just below Whitefish limestone with Serpukhovian conodonts

this paper; Fig. 13A

14 PR-51 352.5�zircon

± 2.6 Rhyodacitic tuff breccia in upper part of formation Mortensen (1992); this paper; Fig. 13B

15 03DM-022 346.8 �zircon

± 2.0 Massive quartz- and feldspar-porphyritic flow(?) this paper; Fig. 13C

16 03DM-023 347.7 �zircon

± 1.4 Hornblende-phyric quartz-feldspar porphyry dike similar to volcanic rocks which it�cuts

this paper; Fig. 13D


Table 2. U-Pb Geochronological Constraints, Money Creek Thrust Sheet.

206 P

b/23

8 U

207Pb/235U

360

380

400

A

C

BD

0.41 0.47 0.530.056

0.060

0.064FV-27

to 2.29 Ga

3-pt. regression(MSWD= 2.8)

360.8 ± 0.8 Ma

Figure 11. U-Pb concordia diagram for a sample of felsic metavol-canic rock from the Waters Creek formation. See Appendix 1 for analyt ical methods, data tables and geochronological interpretations.

90

Murphy et al.

in the volcanic arc granite field of tectonic discrimination diagrams (Grant,�1997;�Grant�et al.,�1996;�Piercey�et al., 2001b).

Neodymium isotopic data for rocks of the Cleaver Lake thrust sheet suggest derivation from an evolved sialic source or contamina-tion�during�passage� through�an� evolved� sialic� crust� (Grant�et al.,�1996;�Grant,�1997;�Piercey�et al., 2003). Samples of the Simpson Range plutonic suite are highly negative, whereas the older volcanic rocks range from moderately negative to slightly positive. These data suggest that the volcanic arc was broadly ensialic (Piercey et al.,�2003).

The age of the Cleaver Lake formation is constrained to be ca.�360 Ma (and likely older) to 356 Ma (Table 3). Quartz porphyry in-trusions that are inferred to be comagmatic with rhyolite flows in the middle of the Cleaver Lake formation have yielded a 360.5 ± 1.9 Ma U-Pb date (Mortensen, 1992b). Gabbro, inferred to be comag-matic with Cleaver Lake formation basalt, has yielded a 356.1 ± 0.9 Ma U-Pb date (Fig. 14, Appendix 1). Cross-cutting Simpson Range quartz monzonite intruding the Cleaver Lake formation has

yielded two dates, 348.4 ± 0.8 Ma and 354.9 ± 1.8 Ma (Figs. 12C, D; Appendix�1).

The klippe of Klatsa metamorphic complex in the southern Campbell Range lies in a similar structural position with respect to footwall stratigraphy as the Money klippe, and is therefore inferred to be a part of the Cleaver Lake thrust sheet (Devine et al., 2004, this volume; Devine, 2005). Besides the mafic and ultramafic meta-plutonic rocks, interfoliated white mica-rich quartz schist and gar-netiferous metabasite are the predominant rock types, representing clastic and basaltic protoliths, respectively. Although retrograde muscovite�and�chlorite�are�pervasive,�these�rocks�contain�relict�tex-tures and prograde minerals that indicate high pressure/low tem-perature metamorphic conditions (Erdmer, 1987; Erdmer et al., 1998; Devine�et al., this volume; Devine, 2005). Geochemically, garnetifer-ous metabasite in the Simpson Range is of MORB affinity (Creaser et al.,�1999).

The age of the protolith of the interfoliated schists is constrained to be Ordovician to Devonian, based on detrital zircon cores as young

356

360

364

C

D

E

T1

T2

0.415 0.425 0.4350.056

0.057

0.058SL-45

titanites: 6/8 agesoverlapping @357.9 ± 1.3 Ma

A

207Pb/235U

350

360

A

BC

DE

T1

0.405 0.415 0.425 0.4350.054

0.055

0.056

0.057

0.058TRP-22

E concordant@ 356.9 ± 0.6 Ma

B

300

320

340

360

A

B

C

DE

0.32 0.38 0.440.045

0.051

0.057SA-02

lower 3-pointdiscordia intercept @

348.4 ± 0.8 Ma

to 1.86 Ga

C

206 P

b/23

8 U

330

340

350

360

A

B

C

D

EF

0.38 0.40 0.420.052

0.054

0.056

0.058SA-28

354.9 ± 1.8 Maweighted average of

Pb/Pb ages

D

Figure 12. U-Pb concordia diagrams for four samples from plutons of the Simpson Range plutonic suite. See Appendix 1 for analytical methods, data tables and geochronological interpretations.

� 91


as�ca. 473 Ma and metamorphic zircon rims as old as ca. 353�Ma�(Devine�et al., this volume; Table 3). Igneous zircons from leucogab-bro of the Klatsa metamorphic complex are ca. 368 Ma (Table 3). The Klatsa metamorphic complex was metamorphosed to eclogite facies metamorphic conditions in a subduction zone at ca.�353,�and�was subsequently rapidly uplifted through the 40Ar/39Ar� closure�temperature for white mica by ca. 353 Ma (Table 3).

Environments of Deposition and Inferred Geodynamic SettingsThe lithological, stratigraphic and geochemical characteristics of Devonian and Early Mississippian rocks in the Big Campbell thrust sheet�suggest�magmatism�and�sedimentation�in�an�initially�rapidly�subsiding, restricted, rift basinal environment developed on primarily sialic� crust� (Piercey,� 2001;� Piercey� et al.,� 2001a,� 2002a,� 2003).�Background sedimentation in the basin in which volcanism occurred

207Pb/235U

340

360

380

400

A

B

C

D

E

0.35 0.45 0.55 0.650.052

0.056

0.060

0.064 to 2.69 Ga

3-pt. regression (MSWD=0.2)C concordant @ 344.5 ± 2.5 Ma

01DM-238

A

340

350

360

A

B

C

0.39 0.40 0.41 0.42 0.430.053

0.055

0.057

PR-51

A concordant@ 352.5 ± 2.6 Ma

B

206 P

b/23

8 U

B-C-D concordant @ 347.7 ± 1.4 Ma

A contains minor inheritance D

03DM-023

340

344

348

352

A

BCD

0.39 0.410.054

0.055

0.056

B&C concordant @ 346.8 ± 2.0 Ma

03DM-022

C

340

344

348

352

356

A

B

C

0.39 0.41 0.430.053

0.055

0.057

Figure 13. U-Pb concordia diagrams for samples of felsic metavolcanic rocks from the Tuchitua River formation. (A) quartz muscovite schist near top of the formation; (B) dacitic tuff breccia near base of the formation; (C) massive conformable quartz-feldspar porphyry in-ferred to be a flow; and (D) discordant quartz-feldspar porphyry dike. See Appendix 1 for analytical methods, data tables and geochrono-logical interpretations.

206 P

b/23

8 U

207Pb/235U

344

348

352

356

A

B

CDE

0.40 0.41 0.420.053

0.055

0.057 ARG-32

356.1 ± 0.9 Maaverage Pb/Pb age

of 4 points

Figure 14. U-Pb concordia diagram for gabbro inferred to be comagmatic with basalt of the Cleaver Lake formation. See Appendix 1 for analytical methods, data tables and geochronological interpretations.

92

Murphy et al.

was carbonaceous, implying an anoxic water column (Bradshaw, 2003;� Bradshaw� et al., 2003). Most of the VMS deposits in the Finlayson Lake district occur at stratigraphic or geochemical breaks at or near the top of major volcanic cycles, locally associated with exhalative rocks and in transitions to carbonaceous basinal sedimen-tation. The onset of carbonaceous background sedimentation above the non-carbonaceous North River formation was sharp, implying a rapid change. This change also coincides with the onset of within-plate magmatism throughout most of the area, implying that mag-matism and subsidence were linked, a characteristic of rift basins (e.g.,�Storey�et al.,�1992).�As�geochemical�trends�in�the�volcanic�rocks�of the Fire Lake formation and lithological trends in cross-cutting plutonic� rocks� indicate� a� transition� to� more� arc-like� rocks� in� the�south, the environment of deposition of the rocks in the Big Campbell thrust sheet is most likely that of an ensialic back-arc basin (Piercey et al., 2000a, b, 2001a, 2002a, b, this volume).

The lithological, stratigraphic and geochemical character of the Waters Creek formation in the Money Creek thrust sheet resembles that of the rocks of the Grass Lakes group, implying a similar re-stricted basinal rift environment developed on ensialic crust. Like the�Grass�Lakes�group,�the�volcanism�occurred�in�a�setting�charac-terized by carbonaceous background sedimentation. Also, like the upward transition between the North River formation and the Grass Lakes group in the Big Campbell thrust sheet, the upward transition from the North River formation to the Waters Creek formation in the Money Creek thrust sheet is sharp and marks the rapid onset of volcanism and deposition of carbonaceous sedimentary rocks. The main difference between the two successions lies in the hornblende-bearing nature of the volcanic rocks of the Waters Creek formation and affiliated plutonic rocks which may imply a position within the basin more proximal to a volcanic arc. Existing geochemical data on the Waters Creek formation are too sparse to further evaluate this possibility at present.

In contrast to the subsiding rift basinal characteristics of the older Waters Creek formation, Grass Lakes group and the Wolverine Lake�group,�the�lithological,�stratigraphic�and�geochemical�character�of the Tuchitua River formation suggests that it was part of a volcanic

and volcaniclastic arc built in an oxygenated marine setting on sialic crust. Much of the formation is composed of pale to medium green intermediate volcanic and volcaniclastic rocks. Pink flow banded rhyolite and rhyodacitic tuff breccias may indicate locally subaerial eruption (Mortensen, 1983, 1992a; Mortensen and Jilson, 1985). Rocks of basinal character are conspicuously lacking in the Tuchitua River formation.

Like the Tuchitua River formation of the Money Creek thrust sheet, the lithological, stratigraphic and geochemical character of the Cleaver Lake formation suggests that it was a volcanic and vol-caniclastic arc buildup in an oxygenated shallow marine to locally subaerial setting. Rocks of restricted basinal character are conspicu-ously lacking in the Cleaver Lake formation. The Nd isotopic data suggest that the crustal basement to the formation was sialic; however samples in the northern part of the Money klippe are less evolved, possibly indicating either a more primitive crustal domain or lack of interaction with sialic crust as the magma passed through it.

Data are insufficient to infer a depositional environment of the protoliths of the Klatsa metamorphic complex. However, their high-pressure/low temperature metamorphic mineral assemblage implies that part of their geological history was spent at great depth, most likely in a subduction zone (Erdmer et al., 1998; Devine et al.,�this�volume).�

Correlations and Late Devonian-Early Mississippian PaleogeographyAlthough�the�various�stratigraphic�successions�and�plutonic�suites�defining Yukon-Tanana terrane in the Finlayson Lake district are fault-bounded, a Late Devonian and Early Mississippian paleogeo-graphic model can be inferred by considering the depositional en-vironments of coeval stratigraphic units, the spatial distribution of these units and the amount and direction of displacement on the faults that separate them. U-Pb geochronological data show that the Waters Creek and Tuchitua River formations in the Money Creek thrust� sheet� are� respectively� coeval� with� the� Grass� Lakes� and�Wolverine Lake groups in the footwall of the Money Creek thrust. Thus, the unconformity which separates the Grass Lakes and

#1 Sample Unit Age (Ma)

2 σ Lithology / Relationship Source

INTRUSIONS INFERRED TO BE COMAGMATIC WITH CLEAVER LAKE FORMATION

17 QP-30 unnamed 360.5 ± 1.9 Quartz porphyritic intrusion inferred to be comagmatic with rhyolite flows in Cleaver Lake formation

Mortensen�(1992a)

18 ARG-32 unnamed 356.1 ± 0.9 Gabbro inferred to be comagmatic with basalt in Cleaver Lake formation Mortensen (1992); this paper; Fig. 14

19 03FD231-1 Klatsa�Metamorphic�Complex

368.0 ± 10.0 Leucogabbro associated with serpentinite host of eclogitic rocks of Klatsa metamorphic�complex

Devine�et al.�(this�volume)

SIMPSON RANGE PLUTONIC SUITE

20 SA-02 younger�phase 348.4 ± 0.8 Hornblende-biotite granodiorite Mortensen (1992); this paper; Fig. 12C

21 SG94-14 younger�phase 345.9 ± 1.2 Hornblende-biotite granodiorite; same body as SA-02 Grant�(1997)

22 SA-28 younger�phase 354.9 ± 1.8 Hornblende-biotite granodiorite; same body as SA-02 Mortensen (1992); this paper; Fig. 12D

ECLOGITE FACIES METAMORPHIC ROCKS

03FD056-2 Klatsa�metamorphic�complex

ca. 473 Age of youngest detrital cores in layered schist Devine�et al.�(this�volume)

23 03FD039-2�03FD056-2

Klatsa�metamorphic�complex

353.1�353.0

±±

2.4�3.7

Felsic schist and metabasite; metamorphic zircons indicate age of high pressure�metamorphism

Devine�et al.�(this�volume)


Table 3. U-Pb Zircon Geochronological Constraints, Cleaver Lake Thrust Sheet.

� 93


Wolverine Lake groups correlates with the unconformity between the Waters Creek and Tuchitua River formations. The isotopic age data also show that the Cleaver Lake formation was deposited at the same time as the Waters Creek formation and the upper part of the Grass Lakes group. Leucogabbro and presumably the serpentinized ultramafic rocks of the Klatsa metamorphic complex are approxi-mately coeval with both the Fire Lake formation and possibly the mafic and ultramafic metaplutonic rocks of the Money klippe. The isotopic age data require that the rocks of the Klatsa metamorphic complex were metamorphosed and uplifted in a subduction zone at ca.�353�Ma�(Devine�et al., this volume). In terms of fault restorations, kinematic data (see section below on Early Permian syn-orogenic clastic sedimentation and shortening) suggest that both the Money Creek and Cleaver Lake thrust faults verge approximately to the northeast. The former has a minimum of 45 km of displacement, and displacement�on�the�latter�is�unconstrained.

In light of these considerations, the Late Devonian and Early Mississippian paleogeographic configuration can be reconstructed. In the Late Devonian, a volcanic arc edifice, represented by the shal-low marine to subaerial Cleaver Lake formation, passed to the northeast into a coeval subsiding proximal back-arc environment, represented by the hornblende-phyric volcanic rocks and carbona-ceous phyllite of the Waters Creek formation. The Waters Creek formation in turn graded east-northeastwardly into a more distal, subsiding back-arc rift represented by the Grass Lakes group and affiliated metaplutonic rocks. The influence of arc processes is ex-pressed in the geochemical characteristics of rocks of the Fire Lake formation in the southern exposures of the Grass Lakes group but disappears to the north where a rift signature is dominant. This dis-tribution of contemporaneous arc and back-arc facies implies northeast-dipping subduc-tion beneath the western margin of the ter-rane, as originally proposed by Mortensen (1992a). An actual Late Devonian subduc-tion complex has yet to be found, although it� may� have� coincided� with� the� slightly�younger�Klatsa�metamorphic�complex.

Although punctuated by cryptic Devono-Mississippian deformation, uplift and erosion, parallel arc and back-arc envi-ronments evolved in Yukon-Tanana terrane into the Early Mississippian. Subduction at this time is recorded in the high pressure/low temperature rocks of the Klatsa metamor-phic� complex,� and� arc� magmatism� at� this�time is represented by the younger intrusions of the Simpson Range plutonic suite. Arc magmatism� predominates� in� the� Money�Creek thrust sheet, manifested by the shal-low submarine to subaerial volcanic and volcaniclastic rocks of the Tuchitua River formation and granodiorite of the Simpson Range plutonic suite. Coeval facies to the east-northeast comprise carbonaceous phyl-

lite and rift volcanic rocks of the Wolverine Lake group, interpreted as the expression of continued back-arc rifting.

Late Mississippian to Early Permian Sedimentation and MagmatismThe Late Mississippian to early Early Permian interval is represented by four sporadically occurring stratigraphic units in the Money Creek thrust sheet: the Whitefish limestone; chert, tuff, limestone and lesser clastic rocks of the White Lake formation; clastic rocks of the King Arctic formation; and a recently recognized upper limestone, the Finlayson Creek limestone. These four units rarely occur together in a continuous complete section owing to regionally significant Pennsylvanian and Early Permian erosional unconformities. The oldest stratigraphic unit of this interval, the Whitefish limestone, is of Late Mississippian age, indicating a hiatus in deposition in the region following Early Mississippian magmatism and sedimentation. Rocks of Yukon-Tanana terrane of mid-Mississippian, essentially early Viséan, age are absent in the Finlayson Lake district and environs.

The Whitefish limestone comprises up to 200 m of recrystal-lized, massive to poorly bedded, locally crinoidal grey limestone. Isolated crinoid fragments are ubiquitous; the lack of crinoids in growth position suggests that the unit is bioclastic. Lenses and later-ally continuous layers of whitish-grey silica are common. Four conodont collections constrain the age of the Whitefish limestone to be Upper Mississippian (late Viséan to Serpukhovian; Table 4). The basal contact of the Whitefish limestone is likely a disconformity or unconformity, based on its Late Mississippian age compared to the

#1 Sample# GSC# Age Reference

WHITEFISH LIMESTONE

Finlayson Lake map area (105G)

F1 96JH-Stop�3 C-303352 Early Carboniferous, Serpukhovian Orchard�(this�volume)

Frances Lake map area (105H)

F2 00DM-219 C-203145 Late Early Carboniferous, late Viséan -Serpukhovian Orchard�(this�volume)

00DM-76 C-203134 Carboniferous – Early Permian Orchard�(this�volume)

F3 00DM-324 C-203149 Early Carboniferous, Serpukhovian Orchard�(this�volume)

WHITE LAKE FORMATION


F4 00DM-45 C-203131 Early Carboniferous, late Viséan - Serpukhovian Orchard�(this�volume)

FINLAYSON CREEK LIMESTONE


F5 TOM-76-14-1 O-93513a Late Carboniferous (Late Pennsylvanian), Gzhelian Orchard�(this�volume)

95DR-67 C-303317 Late Carboniferous to Early Permian Orchard�(this�volume)

99DM-126� C-203121 Late Carboniferous (Late Pennsylvanian), Kasimovian – Gzhelian Orchard�(this�volume)


F6 00DM-90 C-203137 Late Pennsylvanian – Early Permian, Gzhelian - Asselian Orchard�(this�volume)

F7 00DM-131 C-203139 Pennsylvanian? Orchard�(this�volume)

F8 00DM-159 C-203141 Late Carboniferous, Bashkirian - Moscovian Orchard�(this�volume)

F9 03FD-292-1 C-306853 Late Pennsylvanian – Early Permian, Gzhelian - Asselian

83MJO-9306 C-102795 Pennsylvanian? Orchard�(this�volume)

Watson Lake map area (105A)

F10 83MJO-10275L C-102798 Bashkirian Orchard�(this�volume)1�Number is keyed to data points presented in Figure 4.

Table 4. Conodont Age Constraints on the Whitefish Limestone, White Lake Formation and the Finlayson Creek Limestone.

94

Murphy et al.

Early Mississippian (ca. 344 Ma) youngest age of immediately un-derlying felsic metavolcanic rocks.

Where it is not unconformably overlain by younger rocks, the Whitefish limestone is transitionally overlain by chert, tuff, limestone and fine clastic rocks of the White Lake formation. Pale green and locally pink, tan and white chert and tuff are the predominant and distinguishing rock types of the White Lake formation; crinoidal limestone beds are common in the lower part. Where the unit is most completely exposed, pale green siltstone and fine sandstone is com-mon in the upper part (Devine, 2005). The lower part of the White Lake formation is Late Viséan to Serpukhovian in age, based on conodonts from a limestone bed near the base of the unit (Table 4).

Where preserved beneath younger unconformities, the White Lake formation is unconformably overlain by the King Arctic forma-tion, a succession of conglomerate, sandstone and argillite (Devine, 2005). The base of the King Arctic formation is marked by conglom-erate made up of rounded clasts of chert and limestone derived from the underlying White Lake formation. Conglomerate passes upward into about 150 m of mottled green lithic arenite and wacke. The upper part of the formation comprises dark grey, fine grained wacke and argillite. The age of the King Arctic formation is indirectly con-strained to be Early Pennsylvanian, based on the age of the underlying White Lake formation and the age of the Finlayson Creek limestone, which is inferred to unconformably overlie the King Arctic formation (Devine,�2005).

A sporadically preserved succession of gritty and chloritic volcanolithic metaclastic rocks, intermediate to mafic metavolcanic rocks, chert and minor limestone and felsic metavolcanic rock locally lies along strike from exposures of the White Lake and King Arctic formations, below the Finlayson Creek limestone and above a lime-stone that is correlated with the Whitefish limestone, although no fossils have been extracted from it. Based on this stratigraphic posi-tion,�the�clastic�succession�is�tentatively�assigned�a�Pennsylvanian�age and correlated with the White Lake and King Arctic formations. If this is correct, then the sedimentation represented by these two formations took place in a peri-volcanic setting. The Whitefish limestone, the White Lake formation and correlative metavolcanic and volcaniclastic rocks, and the Tuchitua River formation, are all locally overlain by the Finlayson Creek limestone, the youngest rock unit in the Late Mississippian to Early Permian interval. It is massive, pale grey and locally crinoidal – virtually identical to the Whitefish limestone, with which it has been confused. The base of the limestone is locally marked by conglomerate, reflecting the unconformable nature of its basal contact. The Finlayson Creek limestone has yielded conodonts that range in age from Bashkirian to early Asselian (Table 4).

Environments of Deposition and Geodynamic SettingsThe thick-bedded, bioclastic nature of both the Whitefish and Finlayson Creek limestones gives few clues to their depositional settings. The lack of volcanic rocks in both units suggests hiatuses in arc or back-arc volcanism in this area in the Late Mississippian and Late Pennsylvanian. Volcanic rocks were deposited throughout the Pennsylvanian (White Lake and King Arctic formations and

correlative volcanic rocks) although the nature and geochemical af-finity of the volcanism has not been determined. Late Mississippian to Early Permian arc volcanism has been documented in the southern extent of Yukon-Tanana terrane (Klinkit Group; Simard et al.,�2003;�and the upper division of the Lay Range assemblage; Ferri, 1997) implying that the Finlayson Lake district may have been in a back-arc setting�during�that�time.�

Early Permian Synorogenic Clastic Sedimentation and Thrust FaultingGeological relationships in the Finlayson Lake district suggest that Yukon-Tanana terrane during the Early Permian was characterized by regional shortening, uplift, erosion and synorogenic clastic sedi-mentation. Mississippian and Pennsylvanian rocks were folded and eroded before the unconformable deposition of carbonaceous clastic rocks and chert of the Lower Permian Money Creek formation. The latter formation is itself folded and overthrust by the Cleaver Lake and Money Creek thrusts. Lower Permian rocks of the Campbell Range formation of Slide Mountain terrane unconformably overlie both the hanging wall and footwall of the Money Creek thrust, im-plying that movement on the thrust occurred during the Early Permian.

Money Creek FormationThe Money Creek formation (Figs. 3, 4) comprises carbonaceous phyllite; grey, tan, pink and green chert; diamictite; and quartzofeld-spatholithic sandstone, grit and locally conglomerate. It differs from other older carbonaceous clastic units in the area by the immature nature of its detritus and the occurrence of chert (Murphy, 2001). Angular feldspar clasts are a significant component of the Money Creek formation, and lithic clasts comprise felsic and mafic volcanic rocks, quartzite and intraformational chert and carbonaceous phyl-lite. Limestone-pebble conglomerate occurs where the unit overlies the Whitefish or Finlayson Creek limestones.

The Money Creek formation occurs in both the Big Campbell and Money Creek thrust sheets, unconformably overlying different rock units in different places. The formation stratigraphically overlies the Wolverine Lake group in the Big Campbell thrust sheet and, in different areas of the Money Creek thrust sheet, it overlies different parts of the Tuchitua River formation, as well as the Whitefish limestone, White Lake formation, King Arctic formation and Finlayson Creek limestone (Fig. 3; Devine et al., 2004). The Money Creek formation is infolded with the Whitefish limestone where it immediately�underlies�the�Cleaver�Lake�thrust.�Detailed�mapping�reveals that the basal contact of the Money Creek formation is folded by longer wavelength and lower amplitude structures than the un-derlying units, suggesting that some folding of the underlying units had already occurred before its deposition.

The age of the Money Creek formation is constrained to be Lower Permian by the youngest conodont collection from the un-derlying Finlayson Creek limestone (Gzhelian-Asselian; Table 4) and the Asselian to Sakmarian age of the overlying basalt of the Campbell Range formation (see below).

� 95


The Money Creek formation is herein interpreted as a synoro-genic flysch. Deposition of the formation followed the onset of the folding of underlying rocks, and the formation is itself folded and overthrust by the Money Creek and Cleaver Lake thrust sheets. The quartzofeldspathic and volcanolithic nature of the conglomerate implies uplift and erosion of a volcanic and possibly plutonic source area. A logical source for this detritus is the volcanic arc rocks in the hinterland of the thrust belt.

Cleaver Lake and Money Creek ThrustsThe Cleaver Lake and Money Creek thrusts are recognized on the basis of older over younger relationships and strain zones (Murphy and Piercey, 2000a, b; Murphy, 2004). Movement on the structurally higher�Cleaver�Lake�thrust�placed�the�Upper�Devonian�Cleaver�Lake�formation and Mississippian intrusions above the Lower Permian Money Creek formation. Movement on the structurally deeper Money Creek thrust juxtaposed pre-Late Devonian North River formation and younger rocks above rocks as young as the Lower Permian Money Creek formation. These relationships have locally been modified by Cretaceous normal faulting. For example, the Money and North klippen of Tempelman-Kluit (1979) of the Cleaver Lake thrust sheet rest directly on rocks of the Big Campbell thrust sheet, due to dis-placement on the Cretaceous North River fault (Figs. 2, 3; Murphy, 2004).

In terms of fault kinematics and amounts of displacement, the Money�Creek�thrust�cuts�upsection�to�the�north�and�east,�as�demon-strated by the occurrence of progressively younger rocks in both the immediate footwall and the immediate hanging wall in those direc-tions (Fig. 3). This geometry implies east to northeast vergence, an interpretation supported by sparse kinematic data from the footwall strain zone (elongation lineations and various kinematic indicators such as shear bands and asymmetrical boudinage; D.C. Murphy, unpublished data, 2003). The amount of overlap of the Money Creek thrust sheet onto the footwall rocks is about 45 km, implying at least that�much�displacement.�Hence,�rocks�in�the�Money�Creek�thrust�sheet originally lay at least 45 km west-southwest of their current location with respect to the footwall. Similarly, the Cleaver Lake thrust overlies a relatively thin section of Money Creek formation beneath the Money klippe, and a much thicker section of Money Creek formation under the klippe of Klatsa metamorphic complex in the east, implying it cuts upsection from approximately west to east. Sparse slickenside data from the Cleaver Lake thrust plane (Erdmer, 1985; D.C. Murphy, unpublished data, 1997, 1999) indicate northeast-directed displacement. Hence, the Cleaver Lake formation originally lay southwest of the rocks in the Money Creek thrust sheet, which in turn lay west-southwest of the rocks below the Money Creek thrust.

The age of thrusting is constrained to be Early Permian by the age of the youngest rocks offset by thrusting (Lower Permian Money Creek formation) and oldest rocks unaffected by thrusting (Lower Permian Campbell Range formation and related mafic and ultramafic intrusions).

SLIDE MOUNTAIN TERRANERocks in the Finlayson Lake district that have been assigned to Slide Mountain terrane include the Mississippian (and older?) to Lower Permian Fortin Creek group, the Lower Permian Campbell Range formation and comagmatic to slightly younger mafic and ultramafic rocks, and the Lower to Middle Permian Gatehouse formation. While the Fortin Creek group occurs exclusively north of the northern fault boundary of Yukon-Tanana terrane, the Jules Creek fault, the Campbell Range formation and mafic and ultramafic plutonic rock occur both north and south of the Jules Creek fault, defining a narrow corridor around it. South of the Jules Creek fault, the Campbell Range and Gatehouse formations are inferred to unconformably overlie Yukon-Tanana terrane, defining the earliest stratigraphic overlap between Yukon-Tanana and Slide Mountain terranes and requiring their juxtaposition along the Jules Creek fault in the Early Permian. The weakly deformed Campbell Range formation overlies different and more highly deformed older rocks on both sides of the Jules Creek fault, implying an Early Permian unconformity and Early Permian and/or older deformation in rocks on both sides of the fault.

Local Basement CompositionThe basement to the Fortin Creek group is not exposed in the area. However, samples of basalt of the overlying Campbell Range forma-tion that erupted through the crust in that area are uniformly primitive (εNd

t ranging from +6.4 to +8.9; S.J. Piercey and R.A. Creaser, un-

published data), implying the absence of, or lack of interaction with, sialic crust. The Fortin Creek group comprises primarily dark argil-lite and chert of basinal character, suggesting that it was deposited on thin crust of oceanic or transitional character.

Mississippian to Early Permian Sedimentation and MagmatismIn the Slide Mountain terrane of the Finlayson Lake district, the oldest, Mississippian (and older?) to Early Permian unit is the Fortin Creek group. This succession consists primarily of variably deformed dark grey, siliceous carbonaceous phyllite, and grey, green and white chert. Greyish white chert-pebble conglomerate, grey quartzite, shale-chip-bearing quartzofeldspathic grit and conglomerate, and felsic and mafic metavolcanic rock are also locally important con-stituents. The upper part of the group is characterized by tan, pink and green chert and argillite. Rare beds of limestone and dolomite occur�throughout�the�succession�(Murphy�et al.,�2002).

Preliminary geochemical data (S.J. Piercey, unpublished data) on the metavolcanic rocks of the Fortin Creek group provide evidence for a rift-type setting similar to the basinal Devonian and Mississippian rocks in the Big Campbell and Money Creek thrust sheets. A single sample of greenstone has a geochemical signature indistinguishable from that of a modern N-MORB. Six samples of felsic metavolcanic rocks at structurally high levels are weakly alkalic with�trachytic�compositions.

The Fortin Creek group is inferred to be Carboniferous to Early Permian in age on the basis of both local and regional constraints. Locally, variably deformed rocks of the Fortin Creek group are

96

Murphy et al.

overlain by weakly deformed basalt of the Lower Permian Campbell Range forma-tion (see below) and by unfoliated dolo-mite, possibly correlating with the Lower to Middle Permian Gatehouse formation (see below), from which a single conodont collection of Early Permian age was ob-tained (Table 5). Regionally, the group is lithologically�similar�to�and�is�correlated�with the Mt. Aho and Rose Mountain formations, which underlie basalt of the Campbell Range formation along strike to the northwest near Faro (Pigage, 2001, 2004). Conodonts of Early Carboniferous age have been extracted from the lower part of the Mt. Aho Formation; variegated chert of the Rose Mountain Formation ranges in age from Early Carboniferous (Viséan) to Early Permian (Pigage, 2001, 2004; Table 5).

Environments of Deposition and Inferred Geodynamic SettingThe volcanic-poor, carbonaceous shale- and chert-dominated nature of the Fortin Creek�group�suggests�an�anoxic,�deep�water�marine�environment.�The primitive nature of the Nd isotopic signature of overlying basalt suggests that the group may have been deposited on oceanic crust.

Although separated from Yukon-Tanana terrane by the Jules Creek fault, the Fortin Creek group has geological features that are compatible with having been linked geodynamically with Yukon-Tanana terrane during its evolution. With its alkalic felsic metavol-canic and carbonaceous clastic rocks, the older part of the Fortin Creek group resembles the coeval Wolverine Lake group, which records Early Mississippian rifting of Yukon-Tanana terrane ensialic crust. The occurrence of quartzofeldspathic detritus in the Fortin Creek�group�implies�proximity�to�a�granitic�source�terrane.�Although�the age and nature of this source terrane is not known, the Devonian and Mississippian felsic magmatic rocks of Yukon-Tanana terrane are likely candidates. The Fortin Creek group is interpreted as the part of the Slide Mountain ocean that lay adjacent to the inner rift-edge of the Yukon-Tanana terrane crustal block – on the opposite side of the ocean from the North American rifted margin. The Fortin Creek group may be a record of a ‘rift-drift’ transition, the transition to sea-floor spreading and sedimentation on new oceanic crust, in the back-arc region behind the Yukon-Tanana terrane arc.

Early Permian Transform-Related RiftingThe latter Early to Middle Permian interval in the Finlayson Lake district is represented by basalt and chert of the Campbell Range formation, spatially associated mafic and ultramafic plutonic rocks, and limestone and quartzite of the Gatehouse formation. These, and correlative rocks near Faro (Tempelman-Kluit, 1972; Pigage, 2001, 2004), define a 10-12 km-wide arcuate corridor that straddles the

#1 Sample# GSC# Type/Age Reference

FORTIN CREEK GROUP


HP281 radiolarian:�Mississippian�to�Permian T. Harms in�Plint�and�Gordon�(1997)�

ROSE MOUNTAIN FORMATION

Tay River map area (105K)�

F11 99LP-164A C-304787 conodont: Early Carboniferous, early Viséan Orchard�(this�volume)

F12 99LP-80 C-304785 conodont: Early Carboniferous, late Viséan- Serpukhovian Orchard�(this�volume)

F13 99LP-85 C-304786 conodont: Early Carboniferous, late Tournaisian-early Viséan Orchard�(this�volume)

F14 TO-76-27-1 O-093500 conodont: Late Carboniferous Orchard�(this�volume)

F15 TO-67-85 O-080025 fusulinid: earliest Permian Tempelman-Kluit (1972)

CAMPBELL RANGE FORMATION


F16 HP469 radiolarian: mid-Pennsylvanian to Early Permian, Atokan or possibly Missourian to Wolfcampian

T. Harms in�Plint�and�Gordon�(1997)

Tay River map area (105K)

F17 LP-99-180 radiolarian: Early Permian (Asselian-Sakmarian) F. Cordey in�Pigage�(2001, 2004)

GATEHOUSE FORMATION


F18 01MC-173 C-306046 conodont: Early Permian, late Artinskian Orchard�(this�volume)

F19 01DM-162 C-306023 conodont: Early Permian Orchard�(this�volume)


F20 85GGA-7B1 C-118102 conodont: Early Permian, Asselian to Artinskian Orchard�(this�volume)

F21 TO-68-41-8 O-82435 fusulinid: Early to Middle Permian, Wolfcampian to Wordian Tempelman-Kluit (1972)1�Number is keyed to data points presented in Figure 4.

Table 5. Fossil Age Constraints on Rocks of the Slide Mountain Terrane.

Jules Creek and equivalent Vangorda fault for over 300 km. Within this corridor, the Campbell Range formation, and locally the Gatehouse formation, overlie many of the older rock units in the Finlayson Lake district, including the Fortin Creek group north of the Jules Creek fault, and the Money Creek and Tuchitua River for-mations and Grass Lakes group of Yukon-Tanana terrane south of the Jules Creek fault.

Originally considered to be allochthonous with respect to un-derlying rocks (Tempelman-Kluit, 1979; Mortensen and Jilson, 1985; Mortensen, 1992b; Plint and Gordon, 1997), the Campbell Range formation is now considered to have been deposited unconformably on them (Murphy and Piercey, 1999a). The basal basalt contacts are sharp,�and�a�primary�depositional�relationship�with�underlying�rocks�is inferred based on: (1) the observation that the formation every-where overlies older and commonly more deformed rocks; (2) a lack of evidence for faulting (e.g., brittle or ductile deformation) at or near the basal contact; and (3) the presence of euhedral Early Mississippian detrital zircons in a greywacke near the base of the formation, where it overlies the Money Creek formation south of the Jules Creek fault (Fig. 15; Table A2, Appendix 1 [see footnote 1]). In addition, spatially associated mafic and ultramafic plutonic rocks inferred to be comag-matic with Campbell Range basalt intrude underlying strata on both sides of the Jules Creek fault, as well as the basalts themselves.

Weakly metamorphosed basalt is the predominant rock type of the Campbell Range formation (Plint and Gordon, 1997; Murphy and Piercey, 1999a). Although locally foliated south of the Jules Creek fault, basalt is generally massive, green to brown weathering, and dark green to black on fresh surfaces. Pillowed flows and reddish

� 97


and greenish mono- and heterolithic breccias are locally common. Epidote-quartz alteration is a common feature, as is pink to tan jas-peroidal silica. Ribbon chert and argillite and rare limestone are in-tercalated with basalt. Maroon, pink and green chert and siliceous argillite are locally sufficiently widespread to form separate map units. Dark grey or carbonaceous shale occurs locally. Campbell Range basalt hosts the Ice VMS deposit and numerous other copper occurrences (Figs. 3, 4; Hunt, 2002). Diabase, leucogabbro and vari-ably serpentinized ultramafic plutonic rocks are spatially associated with basalt and locally cut it and all underlying rocks.

Early geochemical work on the Campbell Range basalt docu-mented the essential seafloor basaltic character of the unit south of the Jules Creek fault (normal and enriched mid-ocean ridge basalt types - N-MORB and E-MORB; Plint and Gordon, 1997). More re-cent work both north and south of the Jules Creek fault has revealed a greater degree of compositional variability and, in particular, ap-parent geochemical and isotopic differences across the Jules Creek fault (Piercey et al., 1999; S.J. Piercey, D.C. Murphy and R.A. Creaser, unpublished data). All samples of Campbell Range basalt north of the fault can be classified geochemically as N-MORB and BABB types; south of the fault, samples are predominantly E-MORB with lesser N-MORB and OIB (Fig. 16). Basalt north of the fault has εNd

t�

> +6, whereas south of the fault, εNdt is between -4 and +7

(Fig. 5).

The age of the Campbell Range formation is locally constrained by one mid-Pennsylvanian to Early Permian radiolarian collection from chert intercalated with basalt (T. Harms in�Plint�and�Gordon,�1997; Table 5) and two ca. 274 Ma U-Pb dates on cross-cutting, but likely comagmatic leucogabbro (Table 6, Fig. 17, Appendix 1). Regionally, Asselian to Sakmarian radiolaria have been extracted from pink chert immediately beneath basalt of the Campbell Range formation located on strike to the west near Faro (F. Cordey in�Pigage,�2001, 2004; Table 5).

Environments of Deposition and Inferred Geodynamic SettingThe lithological and stratigraphic characteristics of the Campbell Range formation suggest a marine volcanic buildup in an oxygenated basinal environment. The basinal background sedimentary rocks are pink and green radiolarian chert and shale, and basalt is locally hematized. Plint and Gordon (1997) attributed the presence of brec-cias to synvolcanic faulting. The common occurrence of both mono-lithic and heterolithic breccias suggests buildup and subsequent mass failure of topographic slopes, as well as autobrecciation that is char-acteristic of subaqueous basaltic volcanism (e.g.,� McPhie� et al.,�1993).�

Geochemical data indicate that the most likely setting for Campbell Range magmatism was a back-arc basin (Piercey et al.,�this�volume).�A�coeval�succession�with�the�geological�and�geochemi-cal attributes of a volcanic arc has been documented in Yukon-Tanana terrane near the British Columbia-Yukon border south of the Tintina fault (ca. 281 Ma volcanic rocks of the Klinkit Group; Roots et al.,�this�volume;�Simard�et al., 2003). The geographic distribution of arc and back-arc environments suggests that, as throughout the Carboniferous, subduction in the Early Permian was east- or north-east-dipping under the western or southwestern margin of Yukon-Tanana terrane.

Three considerations suggest that the part of the Early Permian back-arc region represented by the Campbell Range formation in the Finlayson Lake district was characterized by strike-slip faulting. First, the Campbell Range formation and subvolcanic intrusions only occur within a few kilometres on either side of the Jules Creek fault. Secondly, the Jules Creek fault juxtaposes different Early Permian and older lithological successions in different areas, but does not significantly vertically offset the Campbell Range formation. Thirdly, the difference in Nd isotopic character across the fault implies that it is a significant crustal boundary. These observations are best ex-plained if the Jules Creek fault was initially a strike-slip fault that juxtaposed Yukon-Tanana terrane against the basinal rocks of the Fortin Creek group of Slide Mountain terrane during and after depo-sition of the Campbell Range formation and intrusion of the comag-

800

1000

1200

1400

1600

1800

2000

2200

2400

2600

+

+

+

+

+

++

+

+

+

+

+++

A

B

CD

E

FGH

I

J

K

0.0 4.0 8.0 12.00.0

0.1

0.2

0.3

0.4

0.5

0.0550.40 0.43

L M

N

348

352

356

206

238

Pb/

U

207 235Pb/ U

0.057


INTRUSIONS INFERRED TO BE COMAGMATIC WITH CAMPBELL RANGE FORMATION

24 98DM-GB leucogabbro 273.4 ± 1.4 Intrudes basalt of Campbell Range formation; spatially associated with ultramafic rocks this paper, Fig. 17

25 GL10 plagiogranite 274.3 ± 0.5 Intrudes basalt of Campbell Range formation; spatially associated with ultramafic rocks Mortensen�(1992a)1�Number is keyed to data points presented in Figure 4.

Figure 15. U-Pb concordia diagram for detrital zircons in grey-wacke near the base of the Campbell Range formation. See Appendix 1 for analytical methods, data tables and geochronological interpretations.

Table 6. U-Pb Zircon Geochronological Constraints, Campbell Range Formation.

98

Murphy et al.

matic mafic and ultramafic plutonic rocks. Although the Jules Creek fault likely continued to be active into the Mesozoic (see below), it, the Campbell Range formation and comagmatic intrusions are in-terpreted here as manifestations of a ‘leaky’ transform fault formed initially during oblique transtension in an Early Permian back-arc region.

Late Early to Middle Permian Uplift and Shallow Water SedimentationIn the Finlayson Lake district, massive limestone or dolomite and quartzite occur in the same corridor around the Jules Creek fault as the signature basalt, chert and mafic and ultramafic metaplutonic rocks of Slide Mountain terrane. South of the Jules Creek fault near Finlayson Lake, thick-bedded, locally crinoidal limestone and overly-ing poorly bedded, grey orthoquartzite of the Lower to Middle(?) Permian Gatehouse formation overlie the upper Pennsylvanian to Lower Permian Finlayson Creek limestone, apparently without any intervening Lower Permian Campbell Range formation (Fig. 2). Similarly, north of the Jules Creek fault, unfoliated sandy dolomite

0 20

kilometres

Campbell

Highway

Highway

Finlayson Lake

GEOCHEMICAL SUITES,CAMPBELL RANGE FORMATION

Ocean island basalt

Back-arc basin basalt

Enriched mid-ocean ridge basalt (E-MORB)

Normal mid-ocean ridge basalt (N-MORB)

Carboniferous to PermianFortin Creek group

Early Permian mafic and ultramaficplutonic rocks

Triassic grey shale

Lower Permian Campbell Rangeformation

Inconnu thrust

Jules Creek fault

Jules Creek fault131°

45’

131°

45’

131°

15’

131°

15’

61°30’61°30’

61°45’61°45’

Figure 16. Compositional variations in the Campbell Range formation, northern Finlayson Lake district (S.J. Piercey and R.A. Creaser, unpublished data).

206 P

b/23

8 U

207Pb/235U

256

260

264

268

272

276

280

A

C

D

0.28 0.30 0.320.040

0.042

0.044

98DM-GB

A concordant@ 273.4 ± 1.4 Ma

Figure 17. U-Pb concordia diagram for a sample of leucogabbro intruding the Campbell Range formation. See Appendix 1 for ana-lytical methods, data tables and geochronological interpretations.

� 99


and quartzite overlie deformed chert and carbonaceous phyllite of the Fortin Creek group.

The Gatehouse formation is included within Slide Mountain terrane because the same association of massive carbonate and lo-cally quartzite with basalt, chert and ultramafic rocks of Slide Mountain�terrane�occurs�in�two�other�localities�along�strike�to�the�west. Near Faro, over 150 km to the west, massive Lower to Middle Permian limestone with large fusulinids is juxtaposed with Campbell Range-like basalt (Tempelman-Kluit, 1972; Table 5), and in a similar structural position further to the west in eastern Alaska, on the southwest side of the Tintina fault, giant fusulinid-bearing Middle Permian limestone and fossiliferous quartz sandstone are spatially associated with basalt, chert and serpentinized ultramafic rocks of the�Seventymile� terrane,� correlative�with�Slide�Mountain� terrane�(Dusel-Bacon�and�Harris,�2003).�

In the Finlayson Lake district, the age of the Gatehouse forma-tion is locally constrained by a Late Artinskian conodont collection found near the top of the limestone member south of the Jules Creek fault (Table 5). Dolomite in the lower part of the formation north of the Jules Creek fault contains Early Permian conodonts (Table 5). Large fusulinids and conodonts from the correlative limestone to the northwest near Faro are of Early to Middle Permian age (Table 5). Massive orthoquartzite in the upper part of the formation has not been found to be fossiliferous in the Finlayson Lake district; but it may correlate with quartz sandstone in a similar setting in eastern Alaska, which contains brachiopods of Permian age and lies in the same� structural� panel� as� limestone� with� Guadalupian� (Middle�Permian) fusulinid megafauna (Dusel-Bacon and Harris, 2003; Foster, 1976).

Environment of DepositionAlthough� seemingly� incongruous� with� respect� to� the� association�with ocean floor basalt, limestone and quartzite of the Gatehouse formation likely represent a shallow-water depositional setting. The absence of the Campbell Range formation beneath the Gatehouse formation near Finlayson Lake suggests that its base may be an erosional unconformity.

MIDDLE PERMIAN TO UPPER TRIASSIC SUCCESSIONSMiddle Permian and younger assemblages in the Finlayson Lake district either are deposited on, or derived from, both Yukon-Tanana and Slide Mountain terranes, attesting to initial juxtaposition of the two terranes along the Jules Creek fault prior to this time. The Middle Permian (to Triassic?) Simpson Lake group is deposited on the Fortin Creek group and the Campbell Range and Gatehouse formations. It is made up of clastic rocks containing detritus derived from both Yukon-Tanana and Slide Mountain terranes and is intercalated with Middle Permian felsic and mafic metavolcanic rocks (Mortensen et al., 1997, 1999). With the exception of coarse-grained clastic rocks of the Faro Peak formation near Faro, Upper Triassic successions deposited on the Slide Mountain terrane resemble the Middle to Upper Triassic Jones Lake Formation of the autochthonous North

American continental margin sequence, indicating that the amalga-mated allochthonous terranes may have been in close proximity to the North American margin in the Early Mesozoic. However, cono-dont fauna with Eurasian affinity (Orchard, this volume) occur in the allochthon, suggesting that its final assembly brought together rocks that may have been deposited at great distances from one an-other. The final emplacement onto autochthonous North America occurred during post-Late Triassic displacement on the Inconnu thrust.�

Late Middle to Late Permian Clastic Sedimentation and Magmatism In the Finlayson Lake district, the Middle to Late Permian interval is represented by the Simpson Lake group, a regionally extensive but narrowly distributed, polymictic conglomerate-bearing unit. Regionally, the Simpson Lake group has a similar distribution to that of the Lower Permian Campbell Range formation and affiliated mafic and ultramafic rocks, occurring within 10 km on either side of the Jules Creek fault or equivalent structures. The group comprises variable amounts of polymictic conglomerate and breccia; locally calcareous, detrital mica-bearing siltstone, sandstone and shale; massive, locally amygdaloidal basalt; limestone and felsic metavol-canic rocks. It unconformably overlies the Fortin Creek group, the Campbell Range and Gatehouse formations and either overlies or is intercalated with late Middle to Late Permian metavolcanic or sub-volcanic intrusive rocks (Figs. 3, 4); many of the conglomerate clast types reflect derivation from these units. Clasts of foliated chert and carbonaceous phyllite were likely derived from the Fortin Creek group. Clasts of basalt and serpentinized ultramafic rocks were likely derived from the Campbell Range formation and affiliated ultramafic intrusions. Clasts of quartz- and feldspar-phyric metavolcanic rock could have been derived from essentially coeval Permian metavol-canic rocks or from nearby exposures of Carboniferous felsic meta-volcanic rocks. Clasts of limestone could also be locally derived, from the Whitefish or Finlayson Creek limestones and/or the Gatehouse formation. The latter formation is potentially the source for quartzite clasts.

In exposures of the Simpson Lake group north of Watson Lake (Fig. 1), clast types also include greenstone, andesite and dacite, all with volcanic arc geochemical signatures; and blueschist and eclogite (Mortensen�et al., 1997, 1999; J.K. Mortensen, unpublished data). Dacite, blueschist and eclogite clasts have yielded mid-Permian to Triassic K-Ar dates. Bedrock sources for these clasts do not crop out around Watson Lake, but they are found elsewhere in either Yukon-Tanana or Slide Mountain terrane. Permian volcanic rocks occur in the Finlayson Lake district, in Division 3 of the Sylvester allochthon in northern British Columbia (Nelson, 1993), and in western Yukon and� easternmost� Alaska� (Klondike� Schist,� Mortensen,� 1990;�Dusel-Bacon�et al., this volume). Eclogite and blueschist with Middle to�Late�Permian� 40Ar/39Ar�dates�occur� in�several�places�along�the�northeastern margin of the amalgamated Yukon-Tanana/Slide Mountain terrane (Erdmer et al., 1998).

The best constraints on the age of the Simpson Lake group suggest that it is Middle to Late Permian, possibly ranging upward

100

Murphy et al.

into the Triassic. A maximum age of the group is provided by the late Early Permian age of the youngest underlying rocks and the mid-Permian age of dacite clasts (Mortensen, 1997, 1999; J.K. Mortensen, unpublished data). Spatially associated felsic meta-igneous rocks in Finlayson Lake map area are ca. 259 Ma (Fig. 18, Table 7, Appendix 1; late Middle to early Late Permian; Okulitch, 2002). Conodonts extracted from samples from Frances Lake and Watson Lake map areas are Permian to Early Triassic in age (Table 8).

Environment of Deposition and Geodynamic SettingThe depositional environment of the Simpson Lake group is inferred to be an oxygenated marine basin into which locally derived mass-flows were deposited and volcanic rocks were erupted. The coarse-grained and polymictic nature of conglomerate in the Simpson Lake group� suggests� a� structurally� controlled� synorogenic� setting�(Tempelman-Kluit, 1972, 1979), such as a foreland basin (Mortensen et al., 1997), forearc basin (Mortensen et al.,�1999)�or�a�strike-slip�basin. A forearc setting is indicated by the presence of clasts of arc magmatic rocks, and blueschist and eclogite clasts from the coeval subduction zone (Mortensen et al., 1999). The narrow distribution of the conglomeratic rocks of the Simpson Lake group along the Jules Creek fault and equivalent structures would support a strike-slip�setting,�although�under�certain�conditions�conglomerates�can�be narrowly distributed near thrust faults in a foreland basin setting as�well�(Catuneanu�et al., 1997). As the Lower Permian Campbell Range formation occurs at similar structural positions and elevations on either side of the Jules Creek fault, however, the fault is unlikely to have had much post-Early Permian vertical displacement.

Regionally, the Middle to Late Permian interval is represented by locally voluminous accumulations of volcanic arc rocks (Klondike Schist of western Yukon/easternmost Alaska, Mortensen, 1992a; Dusel-Bacon�et al., this volume; and Division 3 of the Sylvester al-lochthon in northern British Columbia, Nelson, 1993). In addition, Middle�to�Late�Permian�40Ar/39Ar white mica and U-Pb zircon dates have been obtained from bodies of eclogite and blueschist that are generally located on or near the northeastern edge of the amalgamated Yukon-Tanana/Slide Mountain terrane (Erdmer et al., 1998; Creaser et al., 1999). The regional distribution of Middle to Late Permian arc magmatism and high pressure/low temperature metamorphism (Fig. 1) implies subduction beneath the northeastern margin of the amalgamated Yukon-Tanana /Slide Mountain terrane (Mortensen, 1992a;�Piercey�et al., this volume). The locus of subduction under the terranes had therefore shifted from the southwestern margin of Yukon-Tanana terrane to the northeastern margin of the amalgamated terranes�during�the�Middle�Permian�(Mortensen,�1992a).

Triassic Successions and Their Implications for the History of Amalgamation with North AmericaRocks of Middle and Late Triassic age occur in four structural set-tings in or near the Finlayson Lake district. Weakly deformed and metamorphosed dark grey, silty, phyllitic shale; fine-grained, lami-nated and ripple cross-laminated, tan-brown weathering, detrital mica-bearing sandstone; and fetid, dark grey limestone of Triassic

206 P

b/23

8 U

207Pb/235U

260

270

280

A

B

C

D

E

0.28 0.32 0.360.040

0.042

0.044

0.046

280

320

360

400

440

ABC

D

E

0.25 0.45 0.65 0.850.035

0.055

0.075

230

240

250

260

AB

D

E

0.24 0.280.032

0.036

0.040

01CR-140

01DM-268

00DM-160

B concordant@ 254.7 ± 0.6 Ma

A & C concordant@ 259.8 ± 1.2 Ma

to 2.93 Ga

A & C concordant@ 259.2 ± 0.5 Ma

to 2.24 Ga

A

B

C

Figure 18. U-Pb concordia diagrams for samples constraining the age of Middle to Late Permian igneous rocks in the Finlayson Lake district. (A, B) foliated quartz-feldspar porphyries of uncertain origin near the contact between the Campbell Range formation and the Simpson Lake group; (C) undeformed hornblende-phyric dike intrud-ing the Money Creek formation. See Appendix 1 for analytical methods, data tables and geochronological interpretations.

� 101


age (Table 8) occur in a thrust duplex exposed in the Big Campbell window through Yukon-Tanana terrane (Figs. 2, 3). These rocks are inferred to depositionally overlie undated fragmental basalt, massive greenstone and serpentinized ultramafic rock of Slide Mountain terrane. Secondly, lithologically similar rocks of Late Triassic age (early Norian, Table 8) overlie green-grey chert, carbonaceous phyl-lite and quartzite of the Fortin Creek group immediately south of the Inconnu thrust fault. Thirdly, lithologically similar rocks of Middle to Late Triassic age overlie older rocks of the North American miogeocline north and east of the Inconnu thrust fault along much of its strike length throughout the northern Cordillera (Gordey and Makepeace, 2003; Table 8). Finally, Upper Triassic polymictic con-glomerate of the Faro Peak formation (Pigage, 2001, 2004; Table 8) overlies eclogite and blueschist-bearing metamorphic rocks with Permian cooling ages south of the Vangorda fault near Faro, along strike to the northwest of the Finlayson Lake district.

With the exception of the Faro Peak formation, lithologically similar Middle and Upper Triassic clastic rocks occur on both the allochthonous rocks of the Inconnu thrust sheet and the North American autochthon. As such, these rocks may be inferred to be an overlap assemblage defining the first linkage between the auto-chthonous North American continental margin sequence and the allochthonous terranes (Gabrielse, 1991). In this case, the post-Late Triassic Inconnu thrust would therefore be a manifestation of short-ening affecting all the assemblages following their pre-Late Triassic amalgamation. However, Orchard (this volume) reports Late Triassic conodont fauna from the allochthonous rocks in the Inconnu thrust sheet in the Finlayson Lake district that are Eurasian in affinity, un-like coeval fauna from the North American continental margin se-quence and more like fauna reported from Cache Creek terrane and Wrangellia, both highly displaced tectonostratigraphic terranes in the western Cordillera. This discovery suggests that substantial displacement� could�have�occurred� within� the� amalgamated� Slide�Mountain and Yukon-Tanana terranes in the Triassic prior to their amalgamation�with�the�continental�margin�in�the�Jurassic.

The immature, coarse-grained Faro Peak formation differs from the other Upper Triassic rocks in the region, which are typically made up of well-sorted, variably calcareous and fine-grained silici-clastic rocks. Occurring only near Faro along and south of the Vangorda Creek fault, the extension of the Jules Creek fault, the formation is isolated from all other exposures of Upper Triassic rocks and it is not possible to determine the relationship, if any, between them. It resembles the Middle to Upper Permian Simpson Lake group, both in its lithological character and its narrow distribution along

the Jules Creek fault and, although there are few constraints, may be similarly interpreted as a manifestation of strike-slip faulting.

TECTONIC EVOLUTION OF THE FINLAYSON LAKE DISTRICTThe tectonic evolution of Yukon-Tanana terrane in the Finlayson Lake district that emerges from this and previous work is one of a

#1 Sample# GSC# Age Reference

SIMPSON LAKE GROUP


00DM-200 C-203143 Early Permian to Early Triassic, Asselian to Griesbachian

Orchard�(this�volume)

Watson Lake map area (105A)

96AT-M-69A C-303414 Permian to Early Triassic, Permian to Griesbachian


96AT-M-69B C-303415 Early Permian to Early Triassic, Asselian to Griesbachian


UN-NAMED UNIT IN THE BIG CAMPBELL WINDOW


F23 TO-76-12-6 O-093507� Late Triassic, early Carnian Orchard�(this�volume)

F23 01MC-124 C-306030 Permian-Middle Triassic Orchard�(this�volume)

UN-NAMED UNIT OVERLYING FORTIN CREEK GROUP SOUTH OF THE INCONNU THRUST FAULT


F25 TOM76-23-11b O-093514a Late Triassic, early Norian Orchard�(this�volume)

F25 TOM-76-23-11c O-093514b Late Triassic, early Norian Orchard�(this�volume)

F25 83MJO-CA6571 C-116320 Late Triassic, early Norian Orchard�(this�volume)



F25 83MJO-CA6759 C-116323 Late Triassic, early Norian? Orchard�(this�volume)

F25 01GGA40-2 C-306028 Late Triassic, early Norian Orchard�(this�volume)

F25 01MC-112 C-306029 Late Triassic, early Norian Orchard�(this�volume)

F25 01MC-189 C-306053 Late Triassic, early Norian Orchard�(this�volume)

F25 99P-ICE C-203124 Late Triassic, early Norian (glacial boulder)


F25 98JH-ICE-CLAIM C-303631 Late Triassic, early Norian (glacial boulder)


NORTH AMERICAN TRIASSIC


F26 01DM-284 C-306144 Middle Triassic, late Ladinian Orchard�(this�volume)

FARO PEAK FORMATION


83GGA-30J1 C-103825 Late Triassic, late Carnian; carbonate clast in conglomerate


87GGA-20B3 C-157777 Late Triassic, Carnian?; carbonate clast in conglomerate


98LP-120 C-304121 Late Triassic, early Norian Orchard�(this�volume)

TO-68-430-B(#1) O-086347 Late Triassic, early? Carnian Orchard�(this�volume)

TO-68-430-B(#2) O-086348 Late Triassic, late Norian-Rhaetian




26 01CR-140 ICE area volcanic or subvolcanic porphyry

259.8 ± 1.2 Foliated quartz feldspar porphyry inferred to be depositional/intrusive on/into Campbell Range formation and overlain by Simpson Lake group

this paper, Fig. 18A

27 01DM-268 ICE area volcanic or subvolcanic porphyry

259.2 ± 0.5 Foliated quartz feldspar porphyry inferred to be depositional/intrusive on/into Campbell Range formation and overlain by Simpson Lake group

this paper, Fig. 18B

28 00DM-160 Late�dikes 254.7 ± 0.6 Hornblende diorite dike; intrudes Tuchitua River formation; similar undated dikes intrude Campbell Range formation

this paper, Fig. 18C


Table 7. U-Pb Zircon Geochronological Constraints, Un-named Permian Magmatic Rocks.

Table 8.�Conodont�Age�Constraints�on�the�Simpson�Lake�Group�and�Triassic Successions.

102

Murphy et al.

continental or transitional crustal fragment evolving through rapidly changing�convergent�margin�geodynamic�settings�during�the�mid-�and late Paleozoic. The distribution of Late Devonian and Early Mississippian arc and back-arc magmatic products is consistent with subduction beneath the western or southwestern margin of this crustal block (Mortensen, 1992a; Piercey et al., this volume). The short period of Devonian-Mississippian intra-back-arc deformation between the deposition of the Grass Lakes and Wolverine Lake groups may reflect shortening of the thermally softened overriding plate by synthetic thrusting (Colpron et al., 2000). Following the Early Mississippian cessation of arc and back-arc magmatism in this area, a mid-Mississippian hiatus, a Late Mississippian to Early Permian period of carbonate and chert deposition and volcanism, and Early Permian synorogenic flysch sedimentation, rocks from the forearc and arc were thrust over the Lower Permian flysch and underlying carbonate and inner arc and proximal back-arc rocks along the Cleaver Lake thrust. These latter rocks were in turn thrust to the east-northeast over the back-arc rocks along the Money Creek thrust. The cause for this short-lived episode of shortening is un-known; however, it and subsequent transform faulting which juxta-posed the imbricated Yukon-Tanana terrane with oceanic back-arc rocks of Slide Mountain terrane along the Jules Creek fault may be indications of an obliquely compressional environment in the Early Permian back-arc region, in contrast to the extensional Devonian-Mississippian back-arc.

At the same time as ensialic arc and back-arc rift environments existed on Yukon-Tanana terrane, Slide Mountain terrane was char-acterized by basinal chert and carbonaceous clastic sedimentation and rift volcanism on oceanic crust. An initial sedimentological and stratigraphic link with the Yukon-Tanana terrane back-arc region is inferred from the presence of Carboniferous quartzofeldspathic sandstone in the Fortin Creek group. A firm Early Permian link be-tween the two terranes is indicated by the occurrence of ocean floor basalt of the Campbell Range formation on both Yukon-Tanana and Slide Mountain terranes, deposited during juxtaposition of the two terranes by strike-slip along the Jules Creek and equivalent faults. These linkages between the terranes suggest a Carboniferous paleo-geographic configuration similar to that of the Tertiary to modern Japan arc – Sea of Japan (Nelson, 1993; Creaser et al., 1999; Nelson et al., 2002, this volume). The Early Permian configuration differs somewhat, in the presence of significant strike-slip faulting in the back-arc region.

In the Middle to Late Permian, a forearc setting was established along the inboard (northeastern, present geographic coordinates) margin of the newly amalgamated Yukon-Tanana/Slide Mountain terrane. The switch to subduction along the inboard side of the ter-ranes initiated the process of convergence between the amalgamated Yukon-Tanana/Slide Mountain terrane and North America by the near-consumption of the intervening Slide Mountain ocean basin (Nelson, 1993; Ferri, 1997; Nelson et al.,�this�volume).�Although�the�constraints are few, strike-slip faults may have continued to have been active in the forearc region of the allochthonous terranes, con-tinuing possibly as late as the Late Triassic (Faro Peak Formation). Convergence with the North American continental margin culmi-

nated with the post-Late Triassic thrust displacement of the internally shuffled terranes and affiliated overlap assemblages onto the North American miogeocline along the Inconnu thrust fault.

Although the tectonic evolution of the Finlayson Lake district presented in this paper bears some resemblance to previous models, three aspects of the model are new and noteworthy. First of all, this work documents a metallogenically significant back-arc realm, ele-ments of which occur in both Yukon-Tanana and Slide Mountain terranes. Secondly, this work identifies a type of geological relation-ship that is difficult to categorize using standard terrane terminology, i.e. the depositional onlap of Slide Mountain-type rocks of the Campbell Range formation onto Yukon-Tanana terrane, during their Early Permian juxtaposition along the Jules Creek fault. The Campbell Range formation is therefore both part of Slide Mountain terrane and an overlap assemblage, somewhat of a contradiction. Thirdly, this work highlights the importance of Paleozoic and early Mesozoic strike-slip faulting (e.g., Jules Creek fault) in the shuffling of original paleogeographic relationships – shuffling to the degree that�two�initially�linked�and�contiguous�geodynamic�settings�were�differentiated into two “crustal block(s) or fragment(s) that preserve a distinctive geologic history that is different from the surrounding areas and that are usually bounded by faults” (modified from Coney et al., 1980), i.e. the Yukon-Tanana and Slide Mountain terranes. Furthermore, strike-slip faulting and associated magmatism provide a�mechanism�to�explain�the�apparently�contradictory�geological�re-lationships documented in the Finlayson Lake district, where the Campbell Range formation is both a defining part of Slide Mountain terrane, locally in fault contact with Yukon-Tanana terrane, and a stratigraphic overlap onto Yukon-Tanana terrane. Such relationships may actually be more common than has been documented in other areas where strike-slip faulting is the mechanism by which terranes were�originally�juxtaposed.

ACKNOWLEDGEMENTSThis paper has benefited from numerous stimulating discussions with Maurice Colpron and Grant Abbott of the Yukon Geological Survey, JoAnne Nelson of the British Columbia Geological Survey Branch, and Steve Gordey and Charlie Roots of the Geological Survey of Canada. Discussions with several geologists working with mining and exploration companies active in the Finlayson Lake district are also gratefully acknowledged. Geochronological data presented in this paper were in part produced with the support of a Natural Science and Engineering Research Council (NSERC) grant to JKM. The authors would like to further acknowledge the staff of the Pacific Centre for Isotopic and Geochemical Research at the University of British Columbia for assistance in producing these data. GG would like to thank Alex Pullen, University of Arizona, for assistance in processing the detrital zircon sample reported herein. SP is also supported by a NSERC Discovery Grant. Constructive reviews by Sarah Roeske, Tom Buntzen, Steve Gordey and Maurice Colpron are gratefully acknowledged. DM would finally like to acknowledge the contributions of the numerous geological assistants that have participated in fieldwork.

� 103


REFERENCESBradshaw, G.D., 2003, Geology and genesis of the Wolverine polymetallic volcanic

rock-hosted massive sulphide (VMS) deposit, Finlayson Lake district, Yukon, Canada: M.Sc. thesis, The University of British Columbia, Vancouver, B.C., 172�p.

Bradshaw, G.D., Tucker, T.L., Peter, J.M., Paradis, S. and Rowins, S.M., 2001, Geology of the Wolverine polymetallic volcanic-hosted massive sulphide deposit, Finlayson Lake district, Yukon Territory, Canada: in Yukon Exploration and Geology 2000, Emond, D.S. and Weston, L.H., eds., Exploration and Geological Services Division, Yukon, Indian and Northern Affairs Canada, p. 269-287.

Bradshaw, G.D., Rowins, S.M., Peter, J.M. and Taylor, B.E., 2003, Genesis of the Wolverine deposit, Finlayson Lake district, Yukon: a transitional style of polymetallic massive sulphide mineralization in an ancient continental margin setting: The Gangue, v. 79, p. 1-8.

Catuneanu, O., Beaumont, C. and Waschbusch, P., 1997, Interplay of static loads and subduction dynamics in foreland basins: reciprocal stratigraphies and the ‘missing’ peripheral bulge: Geology, v. 25, p. 1087-1090.

Colpron, M., Murphy, D.C. and Mortensen, J.K., 2000, Mid-Paleozoic tectonism in Yukon-Tanana terrane, northern Canadian Cordillera: record of intra-arc deformation [abstract]: Geological Society of America, Abstracts with Programs, v.�32,�p.�A-7.

Colpron, M., Nelson, J.L. and Murphy, D.C., this volume, A tectonostratigraphic framework for the pericratonic terranes of the northern Canadian Cordillera: in�Colpron, M. and Nelson, J.L, eds., Paleozoic Evolution and Metallogeny of Pericratonic Terranes at the Ancient Pacific Margin of North America, Canadian and Alaskan Cordillera: Geological Association of Canada, Special Paper 45, �p.�1-23.

Coney, P.J., Jones, D.L. and Monger, J.W.H., 1980, Cordilleran suspect terranes: Nature, v. 288, p. 329-333.

Creaser, R., Goodwin-Bell, J.S. and Erdmer, P., 1999, Geochemical and Nd isotopic constraints for the origin of eclogite protoliths, northern Cordillera: implications for the Paleozoic tectonic evolution of the Yukon-Tanana terrane: Canadian Journal of Earth Sciences, v. 36, p. 1697-1709.

Devine, F.D., 2005, Geology of the southern Campbell Range, southeastern Yukon: implications for the tectonic evolution of Yukon-Tanana terrane: M.Sc. thesis, Carleton�University,�Ottawa,�Ontario,�136�p.

Devine, F.D., Murphy, D.C., Kennedy, R., Tizzard, A. and Carr, S.D., 2004, Geological setting of retrogressed eclogite and jade in the southern Campbell Range: Preliminary structure and stratigraphy, Frances Lake area (NTS 105H), southeastern�Yukon,�in Emond, D.S. and Lewis, L.L., eds., Yukon Exploration and Geology 2003: Yukon Geological Survey, p. 89-105.

Devine, F.D., Carr, S.D., Murphy, D.C., Davis, W.J., Smith, S. and Villeneuve, M., this volume, Geochronological and geochemical constraints on the origin of the Klatsa metamorphic complex: Implications for Early Mississippian high-pressure metamorphism within Yukon-Tanana terrane: in Colpron, M. and Nelson, J.L., eds., Paleozoic Evolution and Metallogeny of Pericratonic Terranes at the Ancient Pacific Margin of North America, Canadian and Alaskan Cordillera: Geological Association of Canada, Special Paper 45, p. 107-130.

Duk-Rodkin, A., 1999, Glacial limits map of Yukon Territory: Geological Survey of Canada, Open File 3694, also Exploration and Geological Services Division, Yukon Region, Indian and Northern Affairs Canada, Geoscience Map 1999-2, 1:1,000,000.

Dusel-Bacon, C. and Harris, A.G., 2003, New occurrences of late Paleozoic and Triassic fossils from the Seventymile and Yukon-Tanana terranes, east-central Alaska, with comments on previously published occurrences in the same area: in�Galloway, J.P., ed., Studies in Alaska by the U.S. Geological Survey during 2001: U.S. Geological Survey Professional Paper 1678, p. 5-30.

Dusel-Bacon, C., Hopkins, M.J., Mortensen, J.K., Dashevsky, S., Bressler, J.R. and Day, W.C., this volume, Paleozoic tectonic and metallogenic evolution of the pericratonic rocks of east-central Alaska and adjacent Yukon, in Colpron,�M.�and�Nelson, J.L., eds., Paleozoic Evolution and Metallogeny of Pericratonic Terranes at the Ancient Pacific Margin of North America, Canadian and Alaskan Cordillera: Geological Association of Canada, Special Paper 45, p. 25-74.

Erdmer, P., 1985, An examination of the cataclastic fabrics and structures of parts of Nisutlin, Anvil and Simpson allochthons, central Yukon: test of the arc-continent collision model: Journal of Structural Geology, v. 7, p. 57-72.

Erdmer, P., 1987, Blueschist and eclogite in mylonitic allochthons, Ross River and Watson Lake areas, southeastern Yukon: Canadian Journal of Earth Sciences, v. 24, p. 1439-1449.

Erdmer, P., Ghent, E.D., Archibald, D.A. and Stout, M.Z., 1998, Paleozoic and Mesozoic high-pressure metamorphism at the margin of ancestral North America in central Yukon: Geological Society of America Bulletin, v. 110, p.�615-629.

Ferri, F., 1997, Nina Creek Group and Lay Range assemblage, north-central British Columbia: remnants of late Paleozoic oceanic and arc terranes: Canadian Journal of Earth Sciences, v. 34, p. 854-874.

Foreman, I., 1998, The Fyre Lake project 1997: Geology and mineralization of the Kona�massive�sulphide�deposit:�in Yukon Exploration and Geology 1997, Exploration and Geological Services Division, Yukon, Indian and Northern Affairs Canada, p. 105-113.

Foster, H.L., 1976, Geologic map of the Eagle Quadrangle, Alaska: U.S. Geological Survey Miscellaneous Investigations Series Map I-922, 1:250,000.

Gabrielse, H., 1991, Late Paleozoic and Mesozoic terrane interactions in north central British Columbia: Canadian Journal of Earth Sciences, v. 28, p. 947-957.

Gabrielse, H., Murphy, D.C. and Mortensen, J.K., in press, Cretaceous and Cenozoic dextral�orogen-parallel�displacements,�magmatism�and�paleogeography,�north�central�Canadian�Cordillera,�in Haggart, J.W., Monger, J.W.H. and Enkin, R.J., eds., Evidence for Major Lateral Displacements in the North American Cordillera: Geological Association of Canada, Special Paper 46.

Gordey,�S.P.�and�Makepeace,�A.J.,�2003,�Yukon�digital�geology�(version�2):�Yukon�Geological Survey, Open File 2003-9, and Geological Survey of Canada, Open File 1749.

Grant, S.L., 1997, Geochemical, radiogenic tracer isotopic and U-Pb geochronological studies of Yukon Tanana terrane rocks from the Money klippe, southeastern Yukon, Canada: M.Sc. thesis, University of Alberta, Edmonton, Alberta, 177 p.

Grant, S.L., Creaser, R.A. and Erdmer, P., 1996, Isotopic, geochemical and kinematic studies of the Yukon-Tanana terrane in the Money klippe, SE Yukon, in Cook, F. and Erdmer, P., eds., Slave-Northern Cordillera Lithospheric Evolution (SNORCLE) and Cordilleran Tectonics Workshop: Lithoprobe Report No. 50, p. 58-60.

Hansen, V.L. and Dusel-Bacon, C., 1998, Structural and kinematic evolution of the Yukon-Tanana upland tectonites, east-central Alaska: a record of late Paleozoic to Mesozoic crustal assembly: Geological Society of America Bulletin, v. 110, p.�211-230.

Hansen, V.L. and Oliver, D.H., 1999, Structural and kinematic evolution of the Yukon-Tanana upland tectonites, east-central Alaska: A record of late Paleozoic to Mesozoic crustal assembly: Reply: Geological Society of America Bulletin, v. 111, p. 1420-1422.

Harms, T.A., 1986, The Sylvester allochthon: a tectonized oceanic assemblage record of proto-Pacific telescoping and obduction [abstract]: Geological Society of America, Abstracts with Programs, v. 18, p. 114.

Harms, T.A. and Murchey, B.L., 1992, Setting and occurrence of late Paleozoic radiolarians in the Sylvester allochthon, part of a proto-Pacific ocean floor terrane�in�the�Canadian�Cordillera:�Palaeogeography,�Palaeoclimatology,�Palaeoecology,�v.�96,�p.�127-139.

Hunt, J.A., 2002, Volcanic-associated massive sulphide (VMS) mineralization in the Yukon-Tanana terrane and coeval strata of the North American miogeocline, in the Yukon and adjacent areas: Exploration and Geological Services Division, Yukon Region, Indian and Northern Affairs Canada, Bulletin 12, 107 p.

McPhie, J., Doyle, M. and Allen, R., 1993, Volcanic Textures, A Guide to the Interpretation of Textures in Volcanic Rocks: Centre for Ore Deposit and Exploration Studies, University of Tasmania, 198 p.

Mihalynuk, M.G., Nelson, J., Murphy, D.C., Brew, D.A. and Erdmer, P., 1999, Structural and kinematic evolution of the Yukon-Tanana upland tectonites, east-central Alaska: a record of late Paleozoic to Mesozoic crustal assembly: Discussion: Geological Society of America Bulletin, v. 111, p. 1416-19.

Monger, J.W.H., Wheeler, J.O., Tipper, H.W., Gabrielse, H., Harms, T., Struik, L.C., Campbell, R.B., Dodds, C.J., Gehrels, G.E. and O’Brien, J., 1991, Part B. Cordilleran terranes, Upper Devonian to Middle Jurassic assemblages (Chapter 8), in Gabrielse, H. and Yorath, C.J., eds., Geology of the Cordilleran orogen in Canada: Geological Survey of Canada, Geology of Canada, no. 4, also Geological Society of America, The Geology of North America, v. G-2, p. 281-327.

104

Murphy et al.

Mortensen, J.K., 1983, Age and evolution of the Yukon-Tanana terrane, southeastern Yukon Territory: Ph.D thesis, University of California, Santa Barbara, California, 155 p.

Mortensen, J.K., 1990, Geology and U-Pb geochronology of the Klondike district, west-central Yukon: Canadian Journal of Earth Sciences, v. 27, p. 903-914.

Mortensen, J.K., 1992a, Pre-mid-Mesozoic tectonic evolution of the Yukon-Tanana terrane, Yukon and Alaska: Tectonics, v. 11, p. 836-853.

Mortensen, J.K., 1992b, New U-Pb ages for the Slide Mountain terrane in southeastern Yukon Territory: in Radiogenic Age and Isotopic Studies: Report 5. Geological Survey of Canada, Paper 91-2, p. 167-173.

Mortensen, J.K. and Jilson, G.A., 1985, Evolution of the Yukon-Tanana terrane: evidence from southeastern Yukon Territory: Geology, v. 13, p. 806-810.

Mortensen, J.K., Erdmer, P. and Ghent, E.D., 1997, Westerly-derived Upper Triassic clastic sedimentary rocks in southeastern Yukon: evidence for Early Mesozoic terrane interaction with the western margin of ancestral North America [abstract]: in Cook, F. and Erdmer, P., eds., Slave - Northern Cordillera Lithospheric Evolution (SNORCLE) Transect and Cordilleran Tectonics Workshop, Lithoprobe Report No. 56, p. 76.

Mortensen, J.K., Erdmer, P., Piercey, S.J. and Ghent, E.D., 1999, Evidence for Late Triassic terrane accretion in the northern Canadian Cordillera in southeastern Yukon [abstract]: in Evenchick, C.A., Woodsworth, G.J. and Jongens, R., eds., Terrane Paths 99, Circum-Pacific Terrane Conference Abstract Volume, Geological Survey of Canada/Geological Association of Canada, p. 55.

Mortensen, J.K., Dusel-Bacon, C., Hunt, J. and Gabites, J., this volume, Lead isotopic constraints on the metallogeny of syngenetic base metal occurrences in the Yukon-Tanana terrane and adjacent portions of the North American miogeocline:�in Colpron, M. and Nelson, J.L., eds., Paleozoic Evolution and Metallogeny of Pericratonic Terranes at the Ancient Pacific Margin of North America, Canadian and Alaskan Cordillera: Geological Association of Canada, Special Paper 45, p. 261-279.

Murphy, D.C., 1998a, Stratigraphic framework for syngenetic mineral occurrences, Yukon-Tanana terrane south of Finlayson Lake: a progress report: in�Yukon�Exploration and Geology 1997: Exploration and Geological Services Division, Yukon, Indian and Northern Affairs Canada, p. 51-58.

Murphy, D.C., 1998b, Mafic and ultramafic meta-plutonic rocks south of Finlayson Lake, Yukon; setting and implications for the early geological and metallogenic evolution of Yukon-Tanana terrane [abstract]: in Cook, F. and Erdmer, P., eds., Slave-Northern Cordillera Lithospheric Evolution (SNORCLE) Transect and Cordilleran Tectonics Workshop, Lithoprobe Report, no. 64, p. 120-129.

Murphy, D.C., 2001, Yukon-Tanana terrane in southwestern Frances Lake area (105H/3, 4 and 5), southeastern Yukon, in Emond, D.S. and Weston, L.H., eds., Yukon Exploration and Geology 2000: Exploration and Geological Services Division, Yukon, Indian and Northern Affairs Canada, p. 217-233.

Murphy, D.C., 2004, Devonian-Mississippian metavolcanic stratigraphy, massive sulphide potential and structural re-interpretation of Yukon-Tanana terrane south of the Finlayson Lake massive sulphide district, southeastern Yukon (105G/1, 105H/3,4,5), in Emond, D.S. and Lewis, L.L., eds., Yukon Exploration and Geology�2003:�Yukon�Geological�Survey,�p.�157-175.

Murphy, D.C. and Mortensen, J.K., 2003, Late Paleozoic and Mesozoic features constrain displacement on Tintina Fault and limit large-scale orogen-parallel displacement in the Northern Cordillera [abstract]: Geological Association of Canada Abstracts, v. 28, Abstract 151.

Murphy, D.C. and Piercey, S.J., 1998, Preliminary geological map of Wolverine Lake area, Pelly Mountains, southeastern Yukon (105G/8, north half): Exploration and Geological Services Division, Yukon, Indian and Northern Affairs Canada, Open File 1998-4, 1:50,000.

Murphy, D.C. and Piercey, S.J., 1999a, Finlayson project: Geological evolution of Yukon-Tanana terrane and its relationship to Campbell Range belt, northern Wolverine�Lake�map�area,�southeastern�Yukon,�in Roots, C.F. and Emond, D.S., eds.,Yukon Exploration and Geology 1998: Exploration and Geological Services Division, Yukon, Indian and Northern Affairs Canada, p. 47-62.

Murphy, D.C. and Piercey, S.J., 1999b, Geological map of Wolverine Lake area (105G/8), Pelly Mountains, southeastern Yukon: Exploration and Geological Services Division, Yukon, Indian and Northern Affairs Canada, Open File 1999-3,�1:50,000.

Murphy, D.C. and Piercey, S.J., 2000a, Syn-mineralization faults and their re-activation, Finlayson Lake massive sulphide district, Yukon-Tanana terrane, southeastern�Yukon,�in Emond, D.S. and Weston, L.H., eds., Yukon Exploration and Geology 1999: Exploration and Geological Services Division, Yukon, Indian and Northern Affairs Canada, p. 55-66.

Murphy, D.C. and Piercey, S.J., 2000b, The Money Creek thrust, Yukon-Tanana terrane, southeastern Yukon: Intra-terrane shortening by thrust re-activation of a syn-depositional fault [abstract]: Geological Society of America, Abstracts with Programs,�v.�32,�p.�A57.

Murphy, D.C., Colpron, M., Gordey, S.P., Roots, C.F., Abbott, G. and Lipovsky, P.S., 2001, Preliminary bedrock geological map of northern Finlayson Lake area (NTS 105G), Yukon Territory: Exploration and Geological Services Division, Yukon Region, Indian and Northern Affairs Canada, Open File 2001-33, 1:100,000�scale.

Murphy, D.C., Colpron, M., Roots, C.F., Gordey, S.P. and Abbott, J.G., 2002, Finlayson Lake Targeted Geoscience Initiative (southeastern Yukon), Part 1: Bedrock�geology,�in Emond, D.S., Weston, L.H. and Lewis, L.L., eds., Yukon Exploration and Geology 2001: Exploration and Geological Services Division, Yukon Region, Indian and Northern Affairs Canada, p. 189-207.

Nelson, J.L., 1993, The Sylvester allochthon: Upper Paleozoic marginal-basin and island-arc terranes in northern British Columbia: Canadian Journal of Earth Sciences, v. 30, p. 631-643.

Nelson, J.L., Paradis, S., Christensen, J. and Gabites, J., 2002, Canadian Cordilleran Mississippi Valley-type deposits: A case for Devonian-Mississippian back-arc hydrothermal origin: Economic Geology, v. 97, p. 1013-1036.

Nelson, J.L., Colpron, M., Piercey, S.J., Dusel-Bacon, C., Murphy, D.C. and Roots, C.F., this volume, Paleozoic tectonic and metallogenic evolution of pericratonic terranes in Yukon, northern British Columbia and eastern Alaska: in�Colpron,�M.�and Nelson, J.L., eds., Paleozoic Evolution and Metallogeny of Pericratonic Terranes at the Ancient Pacific Margin of North America, Canadian and Alaskan Cordillera: Geological Association of Canada, Special Paper 45, p. 323-360.

Okulitch, A.V., 2002, Geological time chart, 2002: Geological Survey of Canada, Open File 3040, National Earth Science Series, Geological Atlas - Revision.

Orchard, M.J., this volume, Late Paleozoic and Triassic conodont faunas of Yukon Territory and northern British Columbia and implications for the evolution of Yukon-Tanana terrane, in Colpron, M. and Nelson, J.L., eds., Paleozoic Evolution and Metallogeny of Pericratonic Terranes at the Ancient Pacific Margin of North America, Canadian and Alaskan Cordillera: Geological Association of Canada, Special Paper 45, p. 229-260.

Piercey, S.J., 2001, Petrology and tectonic setting of mafic and felsic volcanic and intrusive rocks in the Finlayson Lake volcanic-hosted massive sulphide (VMS) district, Yukon, Canada: A record of mid-Paleozoic arc and back-arc magmatism and metallogeny: Ph.D. thesis, The University of British Columbia, Vancouver, British Columbia, 305 p.

Piercey, S.J. and Murphy, D.C., 2000, Stratigraphy and regional implications of unstrained�Devono-Mississippian�volcanic�rocks�in�the�Money�Creek�thrust�sheet, Yukon-Tanana terrane, southeastern Yukon, in Emond, D.S. and Weston, L.H., eds., Yukon Exploration and Geology 1999: Exploration and Geological Services Division, Yukon, Indian and Northern Affairs Canada, p. 67-78.

Piercey, S.J., Hunt, J.A. and Murphy, D.C., 1999, Lithogeochemistry of meta-volcanic rocks from Yukon-Tanana terrane, Finlayson Lake region, Yukon: Preliminary�results,�in Roots, C.F. and Emond, D.S., eds., Yukon Exploration and Geology 1998: Exploration and Geological Services Division, Yukon, Indian and Northern Affairs Canada, p. 125-138.

Piercey, S.J., Murphy, D.C., Mortensen, J.K. and Paradis, S., 2000a, Arc-rifting and ensialic back-arc basin magmatism in the northern Canadian Cordillera: evidence from the Yukon-Tanana terrane, Finlayson Lake region, Yukon: in�Cook, F. and Erdmer, P., eds., Slave-Northern Cordillera Lithospheric Evolution (SNORCLE) and Cordilleran Tectonics Workshop, Lithoprobe Report No. 72, p. 129-138.

Piercey, S.J., Murphy, D.C., Paradis, S. and Mortensen, J.K., 2000b, Tectonic setting of the Finlayson Lake volcanogenic massive sulfide (VMS) district, Yukon-Tanana terrane, southeastern Yukon, Canada, in Volcanic Environments and Massive Sulfide Deposits, Program with Abstracts: CODES Special Publication, p. 153-154.

� 105


Piercey,�S.J.,�Murphy,�D.C.,�Mortensen,�J.K.�and�Paradis,�S.,�2001a,�Boninitic�magmatism in a continental margin setting: Yukon-Tanana terrane, southeastern Yukon, Canada: Geology, v. 29, p. 731-734.

Piercey, S.J., Paradis, S., Murphy, D.C. and Mortensen, J.K., 2001b, Geochemistry and paleotectonic setting of felsic volcanic rocks in the Finlayson Lake volcanic-hosted massive sulfide (VMS) district, Yukon, Canada: Economic Geology, v. 96, p. 1877-1905.

Piercey, S.J., Mortensen, J.K., Murphy, D.C., Paradis, S. and Creaser, R.A., 2002a, Geochemistry and tectonic significance of alkalic mafic magmatism in the Yukon-Tanana terrane, Finlayson Lake region, Yukon: Canadian Journal of Earth Sciences, v. 39, p. 1729-1744.

Piercey, S.J., Paradis, S., Peter, J.M. and Tucker, T.L., 2002b, Geochemistry of basalt from the Wolverine volcanic-hosted massive-sulphide deposit, Finlayson Lake district, Yukon Territory: Geological Survey of Canada, Current Research, 2002-A3,�11�p.

Piercey, S.J., Mortensen, J.K. and Creaser, R.A., 2003, Neodymium isotope geochemistry of felsic volcanic and intrusive rocks from the Yukon-Tanana terrane in the Finlayson Lake region, Yukon, Canada: Canadian Journal of Earth Sciences, v. 40, p. 77-97.

Piercey, S.J., Murphy, D.C., Mortensen, J.K. and Creaser, R., 2004, Mid-Paleozoic initiation of the northern Cordilleran marginal back-arc basin: geologic, geochemical and neodymium isotope evidence from the oldest mafic magmatic rocks in Yukon-Tanana terrane, Finlayson Lake district, southeast Yukon, Canada: Geological Society of America Bulletin, v. 116, p. 1087-1106.

Piercey, S.J., Nelson, J.L., Colpron, M., Dusel-Bacon, C., Roots, C.F. and Simard, R.-L., this volume, Paleozoic magmatism and crustal recycling along the ancient Pacific margin of North America, northern Cordillera, in Colpron,�M.�and Nelson, J.L., eds., Paleozoic Evolution and Metallogeny of Pericratonic Terranes at the Ancient Pacific Margin of North America, Canadian and Alaskan Cordillera: Geological Association of Canada, Special Paper 45, p. 281-322.

Pigage, L.C., 2001, Geological map of Anvil District (NTS 105K/2, 3, 5, 6, 7, 11), Central Yukon: Exploration and Geological Services Division, Yukon Region, Indian and Northern Affairs Canada, Open File 2001-31, 1:100,000.

Pigage, L.C., 2004, Bedrock geology compilation of the Anvil District (parts of 105K/2, 3, 5, 6, 7 and 11), central Yukon: Yukon Geological Survey, Bulletin 15, 103�p.

Plint, H.E. and Gordon, T.M., 1997, The Slide Mountain terrane and the structural evolution of the Finlayson Lake fault zone, southeastern Yukon: Canadian Journal of Earth Sciences, v. 34, p. 105-126.

Richards, D.R., Butler, R.F. and Harms, T.A., 1993, Paleomagnetism of the late Paleozoic Slide Mountain terrane, northern and central British Columbia: Canadian Journal of Earth Sciences, v. 30, p. 1898-1913.

Roddick, J.A., 1967, Tintina Trench: Journal of Geology, vol. 75, p. 23-32.Roots, C.F., Nelson, J.L., Simard, R.-L. and Harms, T.A., this volume, Continental

fragments, mid-Paleozoic arcs and overlapping late Paleozoic arc and Triassic sedimentary strata in the Yukon-Tanana terrane of northern British Columbia and�southern�Yukon,�in Colpron, M. and Nelson, J.L., eds., Paleozoic Evolution and Metallogeny of Pericratonic Terranes at the Ancient Pacific Margin of North America, Canadian and Alaskan Cordillera: Geological Association of Canada, Special Paper 45, p. 153-177.

Simard, R.-L., Dostal, J. and Roots, C.F., 2003, Development of late Paleozoic volcanic arcs in the Canadian Cordillera: an example from the Klinkit Group, northern British Columbia and southern Yukon: Canadian Journal of Earth Sciences, v. 40, p. 907-924

Storey, B.C., Alabaster, T. and Pankhurst, R.J., 1992, Magmatism and the Causes of Continental Break-up: Geological Society of London, Special Publication No. 68, 404 p.

Tempelman-Kluit, D.J., 1972, Geology and origin of the Faro, Vangorda, and Swim concordant zinc-lead deposits, central Yukon Territory: Geological Survey of Canada, Bulletin 208, 73 p.

Tempelman-Kluit, D.J., 1977, Quiet Lake, (105F) and Finlayson Lake (105G) map areas, Yukon Territory: Geological Survey of Canada, Open File 486, 1:250,000.

Tempelman-Kluit, D.J., 1979, Transported cataclasite, ophiolite and granodiorite in Yukon, and evidence of arc-continent collision: Geological Survey of Canada, Paper 79-14.

Wheeler, J.O., Green, L.H. and Roddick, J.A., 1960, Finlayson Lake map area, Yukon Territory: Geological Survey of Canada, Map 8-1960, 1:253,440.

106

Documents

Mid-Paleozoic to early Mesozoic tectonostratigraphic ...spiercey/Piercey_Research_Site/Publicatio… · Paleozoic Evolution and Metallogeny of Pericratonic Terranes at the Ancient