g ceologi Manitoba’s Far-North Mapping Initiative ... · Christian O. Böhm ([email protected]) and Scott D. Anderson ([email protected]) Modified from Rob Rainbird,

Regional GeologyThe southeast margin of the has been regionally subdivided into six geological domains: the Mudjatik, Peter Lake (present only in Saskatchewan), Wollaston, Seal River, Great Island and Nejanilini domains. The domains are distinguished by their cover rocks, the proportion or absence of basement rocks, and their dominant structural trends.

Hearne craton

Manitoba’s Far-North Mapping Initiative: Reconnaissance Bedrock Mapping and Sampling of the Great Island Domain

Christian O. Böhm and Scott D. Anderson ([email protected]) ([email protected])

Modified from Rob Rainbird,Geological Survey of Canada, 2005Modified from Rob Rainbird,Geological Survey of Canada, 2005

Mineral Potential of Manitoba’s Far North: A Brief Overview

from Rainbird, Davis, Pehrsson (GSC Ottawa)

Hurwitz Group, central Hearne domainHurwitz Group, central Hearne domain

West of Nueltin LakeWest of Nueltin Lake

• Remote • Extensive surficial deposits• <1% outcrop exposure

(including shorelines)• Poorly understood bedrock

geology• Minimal previous exploration• Requires use of indirect

detection methods• till geochemistry• indicator mineral surveys• geophysical surveys





Dredge and Pehrsson, 2006GSC OF5320


• 420 archival (1977-1980) samples• <2 um size-fraction of surficial tills• As,Co,Cu,Cr,Fe,Mo,Mn,Ni,Pb,U,Zn

Far-north exploration:challengesFar-north exploration:challenges

West of Nueltin LakeWest of Nueltin Lake











• 420 archival (1977-1980) samples• <2 um size-fraction of surficial tills• As,Co,Cu,Cr,Fe,Mo,Mn,Ni,Pb,U,Zn

Far-north exploration:challengesFar-north exploration:challenges

UraniumUranium

Recent results: highest outcrop values ranging from 0.5 -- 0.8% U3O8, and boulders from 2% - 11% U3O8

Exploration parameters:• Post-orogenic siliciclastic

basins• Graphitic metapelites in

basement• Regional basement faults

http://gsc.nrcan.gc.ca/mindep/synth_dep/uranium/index_e.php

Wollaston Domain in Manitoba: How far below the basal unconformity?


MBSK

Snyder Lk

LacBrochet

UraniumUranium

Recent results: highest outcrop values ranging from 0.5 -- 0.8% U3O8, and boulders from 2% - 11% U3O8

Exploration parameters:• Post-orogenic siliciclastic

basins• Graphitic metapelites in

basement• Regional basement faults

http://gsc.nrcan.gc.ca/mindep/synth_dep/uranium/index_e.php



MBSK

Snyder Lk

LacBrochet

Sediment-hosted base metalsSediment-hosted base metals

Exploration parameters:• Platform/rift sequences• Restricted rift-basins• High heat-flow• Exhalative activity

• Regional heavy mineral sampling• Significant numbers of gahnite grains• BHT or SHMS prospectivity


Good potential inWollaston & Great

Island domains


Island domains

Survey by Sediment-hosted base metalsSediment-hosted base metals

Exploration parameters:• Platform/rift sequences• Restricted rift-basins• High heat-flow• Exhalative activity




Island domains


Island domains

Survey by

Volcanic-hosted massive sulphideVolcanic-hosted massive sulphide

Exploration parameters:• Subaqueous bimodal

volcanic rocks • Arc/back-arc volcanic

settings• Subaqueous rift

sequences

HudsonBay

Eppler Lake projectWestern Warrior Res. Inc.

Au-rich VHMS?Great Island Domain

(3.36 g/t Au in massive tosemi-massive sulphide)



Volcanic-hosted massive sulphideVolcanic-hosted massive sulphide

Exploration parameters:• Subaqueous bimodal

volcanic rocks • Arc/back-arc volcanic

settings• Subaqueous rift

sequences

HudsonBay


HudsonBay







Iron formation;0.41 opt Au/3.0 ft.

Orogenic goldOrogenic gold

Exploration parameters:• Accretionary orogens• Greenstone terranes• Major shear zones• Chemical/structural traps

Iron formation hosted AuGreat Island Domain



Iron formation;0.41 opt Au/3.0 ft.

Orogenic goldOrogenic gold

Exploration parameters:• Accretionary orogens• Greenstone terranes• Major shear zones• Chemical/structural traps



Previous exploration:Wollaston Domain (Uranium)Great Island Domain (Au, base metals)


Recent/ongoing exploration:Diamonds Base- and precious metalsUranium






Geology of the Great Island DomainMetasedimentary rocks throughout Manitoba's Far North are thought to be broadly correlative with the Paleoproterozoic Wollaston Supergroup in Saskatchewan and northwest Manitoba (ca. 2.1-1.9 Ga) and the partially time-equivalent Hurwitz Group in Nunavut (ca. 2.4-1.9 Ga). The age and possible correlation of metavolcanic rocks in the Great Island area, however, remain unknown; samples obtained during the 2008 program will be utilized to resolve outstanding questions regarding the age, provenance and correlation of all the major supracrustal rock types in the Great Island Domain.

Supracrustal rocks in the Great Island Domain are intruded by syn to late-tectonic granodiorite, quartz monzonite and granite plutons. Similar plutons in the Wollaston Domain in Saskatchewan yielded ages between ca. 1.84 and 1.80 Ga, which corresponds to the main period of Hudson granite emplacement throughout the Western Churchill Province.

Metamorphic mineral assemblages indicate that the metamorphic grade in the Great Island Domain generally ranges from low in the southeast to high in the northwest. Lower greenschist facies metasedimentary rocks are exposed in the deeply incised banks of the lower North Knife River, whereas upper amphibolite or granulite facies metaplutonic rocks are exposed in extensive outcrop fields north of Great Island, at the south margin of the Nejanilini Domain.Finite strain varies from moderate to intense in the examined outcrops. Structural trends in the south are generally east-west and mesoscopic deformation structures indicate at least two generations of tight to isoclinal folds, the latter of which is associated with the development of a penetrative, generally east-trending, transposition fabric. In the north, structural trends are much more variable and reflect the presence of macroscopic dome and basin-style folds, the most prominent example of which is centred on Meades Lake, north of Great Island. Observed bed forms and younging criteria indicate that metasedimentary rocks in this portion of the study area occupy synclinal keels, whereas metaplutonic and minor metavolcanic rocks occupy the intervening anticlinal culminations. Other prominent synclinal basins occur along the north-trending section of the lower Seal River ~30-40 km west of Hudson Bay (herein termed the 'Grand Bend' basin) and to the west of the north-trending section of the lower North Knife River (herein termed the 'Nowell Lake' basin).

The Manitoba Geological Survey (MGS) created the

to study the southeast margin of the Archean Hearne craton in Manitoba, with the goal of furthering our understanding of the nature, evolution and mineral potential of one of the principal but least explored geological building blocks of Manitoba's Precambrian shield.

The 2008 fieldwork consisted of reconnaissance bedrock

mapping and sampling in the area of the lower Seal and North

Knife rivers, which are situated within the Great Island Domain

at the southeastern extent of the Hearne craton.

The Great Island Domain, which was last mapped in the 1970s

by the MGS (Schledewitz, Weber et al.), includes key exposures

of metasedimentary cover rocks, as well as the only known

occurrences of metavolcanic rocks in Manitoba's far north, the

age and significance of which have yet to be determined.

The 2008 reconnaissance bedrock mapping and sampling in the

Great Island Domain mainly focused on metavolcanic and

metasedimentary outcrops along the lower Seal and North

Knife rivers, and included the collection of representative

bedrock samples of all the major rock-types previously

identified in the Great Island Domain. These samples are being

submitted for lithogeochemical (Actlabs), Sm-Nd isotopic

(University of Alberta Radiogenic Isotope Facility) and U-Pb

geochronological analysis (Geochronology Laboratory of the

Geological Survey of Canada), in advance of a more concerted

mapping program planned for the 2009 field season as part of

the MGS’s Far North mapping initiative.

Far North Mapping Initiative

The MGS Far North Mapping Initiative commenced in 2004 with a Sm-Nd isotopic study of archival granitoid samples collected by D. Schledewitz from throughout the NTS 64P map sheet, and was followed up with targeted bedrock and surficial mapping and sampling at Nejanilini Lake in 2005 and in the Kasmere and Putahow lakes area in 2006. From a bedrock geological perspective, the Nejanilini Lake study provides detailed insight into the tectonothermal evolution of plutonic and subordinate sedimentary cover rocks inboard of the Hearne craton margin, whereas the Kasmere-Putahow lakes studies provide insight into evolution of the mainly sedimentary cover rocks at the craton margin.

Bedrock exposures examined in 2008 range up to 160 km west of Churchill. The 2008 field studies included detailed petrographic-petrological and structural mapping of bedrock exposures at 43 stations (see map to the left), which were chosen based on previous mapping by Schledewitz et al. to include all of the major rock types in the region. Emphasis was placed on known occurrences of supracrustal rocks. At each station, representative bedrock samples were collected for laboratory analysis; in most cases the quality and volume of the material collected are sufficient for geochemical, isotopic and/or geochronological analysis.

The Paleoproterozoic cover sequences

In Manitoba

to the Archean Hearne craton in Manitoba bridge the areas where similar sequences have been defined separately: the Hurwitz Group of the central Hearne craton in Nunavut and the Wollaston Supergroup of the south Hearne craton in northeast Saskatchewan. These sequences record rifting, basin opening and basin closure during the breakup of 'Kenorland' and the assembly of Laurentia.

, the cover sequences consist of thick successions of quartzite, arkose, calc-silicate, psammite, semipelite and pelite (from base to top), which are intruded by younger, Paleoproterozoic, granitoid plutons, and were deposited as a passive-margin sequence along the rifted southeast margin of the Hearne craton, and/or within restricted extensional sub-basins inboard from the craton margin. U-Pb detrital zircon age data presented here are comparable to similar rocks from both the Hurwitz Group in Nunavut and the Wollaston Supergroup in Saskatchewan.

2005 mapping

Nejanilini Lake

2004 sampling

2006 mapping

Putahow Lake

Kasmere Lake 2005 mapping

Nejanilini Lake

2004 Nd isotope scoping study

Nejanilini Domain

2004 sampling

2003 sampling

2008 scoping study

2009 Far North Mapping Initiative

2006 mapping

Putahow Lake

Kasmere Lake

Kasmere and Putahow-Goose lakes, Wollaston-Mudjatik domains

0

5

10

15

20

25

1700 1900 2100 2300 2500 2700 2900 3100

207Pb/206Pb age (Ma)

Nu

mb

er

n = 49Goose Lake PsammiteU-Pb detrital zircon age distribution

0

2

4

6

8

10

12

14

1800 2000 2200 2400 2600 2800 3000 3200


n = 51Putahow Lake PsammiteU-Pb detrital zircon age distribution

0

5

10

15

20

25

30

2450 2550 2650 2750 2850 2950 3050 3150

207Pb/

206Pb age (Ma)

Rela

tive

pro

bab

ility

n = 43

Goose Lake QuartziteU-Pb detrital zircon age distribution

0

5

10

15

20

2500 2600 2700 2800 2900 3000 3100


Nu

mb

er

Re

lativ

ep

rob

ab

ility

n = 57 Lovat Lake Quartz-areniteU-Pb detrital zircon age distribution

0

5

10

15

20

25

2000 2200 2400 2600 2800 3000 3200 3400 3600


Nu

mb

er

Re

lativ

ep

rob

ab

ility

n = 46ChurchillQuartziteU-Pb detrital zircon age distribution

2100

2000

1900

1800

0.30

0.32

0.34

0.36

0.38

0.40

4.6 5.0 5.4 5.8 6.2 6.6 7.0 7.4

207Pb/235U

20

6P

b/2

38U

data-point error ellipses are 2

97-05-1003 Nejanilini LakeSemipelitic metagreywacke

LA-MC-ICPMS U-Pb zircon

ID-TIMS U-Pb zircon

moderate amount of very small, subhedraldetrital zircons

Based on this preliminary zircon age data

the sediment age should be younger than ca. 1855 Ma

TCR Nd model age = 2.8 Ga

Nd (2.70 Ga) = 2.60

5

10

15

20

2400 2600 2800 3000 3200 3400

207Pb/

206Pb age (Ma)

Nu

mb

er

Re

lativ

ep

rob

ab

ility

n = 58

Mobilizate in paragneiss contains metamorphic zircon: 1813 +/-1 Ma

Nejanilini Lake, Nejanilini Granulite Domain

Nejanilini Lake QuartziteU-Pb detrital zircon age distribution

Nejanilini Lake GreywackeU-Pb detrital zircon ages

Churchill

Nunavut

Sa

ska

tche

wa

n

2004 Nd isotope scoping study

Nejanilini Domain

MGSMGS

ol go ie cg a la sb

uo

rti vn ea y

m

19 82

Hand-picked zircon crystals

0.1 mm

Zircon crystals with laser pits

0.1 mm

Standard and sample zircons mounted and polished in epoxy

5 mm

University of Alberta Radiogenic Isotope Facility, Dr. A. Simonetti, Nu Instruments LA -MC-ICPMS

DetritalDetrital Zircon UZircon UUsing LaserUsing LaserDetritalDetrital Zircon UZircon UUsing LaserUsing Laser

--PbPb Age Dating TechniqueAge Dating Technique--Ablation MultiAblation Multi--Collector ICPCollector ICP--MSMS

--PbPb Age Dating TechniqueAge Dating Technique--Ablation MultiAblation Multi--Collector ICPCollector ICP--MSMS

Hand-picked zircon crystals

0.1 mm

Zircon crystals with laser pits

0.1 mm

Standard and sample zircons mounted and polished in epoxy

5 mm

University of Alberta Radiogenic Isotope Facility, Dr. A. Simonetti, Nu Instruments LA -MC-ICPMS

A summary of up-to-date U-Pb detrital zircon ages of metasedimentary rocks of the southeast Hearne craton in Manitba

2008 scoping study:2008 scoping study:43 stations43 stations

49 samples49 samplesRadiometric and magnetic airborne survey (fall 2008)

2008 scoping study:2008 scoping study:43 stations43 stations

49 samples49 samplesRadiometric and magnetic airborne survey (fall 2008)

MeadesLake

Great Island

North arm Seal R.

South arm Seal R

.

Seal R

iver

‘Grand Bend’ basin

‘Nowell Lake’ basin

North Knife River

Synformal basins

Great IslandGrand BendNowell Lake

Geomapping for Energy and Minerals (GEM)

national program (2008-2013):

The Bottom Line: The Manitoba Geological Survey is ramping up for its 2009-2011 Far North Mapping Initiative. Main foci are the detailed mapping and mineral potential assessment of the supracrustal sequences partly coeval to the Wollaston and Hurwitz groups. In the Great Island area, these supracrustal rocks, together with their basement and younger intrusions, have excellent exploration potential particularly for uranium and gold.

GIGBNL

Documents

g ceologi Manitoba’s Far-North Mapping Initiative ... · Christian O. Böhm ([email protected]) and Scott D. Anderson ([email protected]) Modified from Rob Rainbird,