U.S. DEPARTMENT OF THE INTERIOR U.S. GEOLOGICAL SURVEY

Descriptive ^nd cheniicah^ta)for hydrothermal

northern Cl§%^ti]eilt, i^inile Fuca Ridge

-15

Monolith Vent; Southern Edifice, 1994

Areas of live biological communities Area of old biological communities

oxidizied surfaces Broken Sheet flow,

Youngest (Beehives)

Sulfidesubstrate

Oldest withoxidizied surfaces

Focused flow, light grey fluids

Medium flow rate, dark grey vent fluid

Diffuse flow, clear fluids

U.S. DEPARTMENT OF THE INTERIOR

U.S. GEOLOGICAL SURVEY

Descriptive and chemical data for hydrothermal sulfide-sulfate-silica

chimneys from the northern Cleft segment, Juan de Fuca Ridge

by

Virginia K. Smith 1

Randolph A. Koski 1

Open File Report 94-15

This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey

editorial standards (or with the North American Stratigraphic Code.) Any use of trade, product, or

firm names is for descriptive purposes only and does not imply endorsement by the U.S.

Government.

U.S. Geological Survey, Menlo Park, CA.

CONTENTS

Page

Introduction 1Vent Sites 4Description of Chimney Samples 4

Type I Chimneys 7Type II Chimneys 7Type IE Chimneys 16Type IV Chimneys 16

Bulk Chemistry of Chimneys 16Summary 19Acknowledgments 19References 20

ILLUSTRATIONS

Figure 1. SeaBeamMap 2Figure 2. Geologic Map 3Figure 3. Black and White Alvin photos 2Figure 4. Black and White photos of samples 3

TABLES

Table 1. Chimney Characteristics 7Table 2. Sample Descriptions 10Table 3. Chemistry 17

INTRODUCTION

During dive programs in 1988, 1990, and 1991, 37 hydrothermal chimney samples were collected by the submersible Alvin between latitudes 44°54' N and 45°01'N on the northern Cleft segment of the Juan de Fuca Ridge, northeast Pacific Ocean (fig. 1). Recent volcanic eruptions from a fissure system at the ridge axis has produced a 7.5-km-long sheet flow and a series of pillow mounds (fig. 2, Chadwick and others, 1991; Embley and others, 1991). In 1986 and 1987, thermal and chemical "megaplumes" produced by large exhalations of hydrothermal fluid were detected on the same ridge segment (Baker and others, 1987; 1989). Active hydrothermal discharge in the northern Cleft segment consists of (1) diffuse low-temperature (<60°C) flow through the young sheet flows and along the fissure system within a few kilometers north and south of the sheet flow area, and (2) focused high-temperature (to 328°C) flow from sulfide mounds and chimneys at three principal sites (the Monolith, Fountain, and Pipe Organ vents) along the fissured terrain (fig. 2).

In this report, we present macroscopic descriptions and all available bulk chemical data for the chimney samples. More comprehensive descriptions of the geologic setting and the hydrothermal deposits are presented by Embley and Chadwick (1994) and Koski and others (1994).

130°16'W 130° 15' 130° 14' 130° 13' 130° 12' 130° 11' 130° 10' 130° 09'45C

45° OO1

44° 59' -

44° 58' --

Inactive Sulfide Chimney

Mapped Sheet Flow

44° 57' -

44° 56

44° 55' ^

44° 54'

FIGURE 1. SeaBeam map of the northern Cleft Segment showing area of recent sheet flow, high- temperature vent sites, and other inactive chimney samples. Contour interval is 10 m. Bathymetry and location of sheet flow provided by R. Embley.

130°15'W 130°14' 130°13' 130°12' 130°10'

45°01'N

45°00'

44°59' -

44°58' _

44057- _/

44°56' _

44°55'

Constructional Terrain(1) = Youngest(2) = Intermediate(3) = Older(4) = Oldest

High Temperature Vent Fault Fissure

- - Lineation Young Sheet FlowInactive Sulfide Chimneys

New Piilovy Mound

LavaRiseRidge

ALV2435-3 ALV2266-3 ALV2266-4ALV2094-4

ALV2435-9A ALV2435-8

Fountain Vent Monolith Vent

ALV2258-1 A.

ALV2094-1

^ /

ipe,; ^e/nt J/ j It"

ALV2444-3A

/3 J // ALV2078-2Wl

0 1 Kilometers

i

FIGURE 2. Interpretive geologic map of the northern Cleft segment showing bathymetry, area of young sheet flow lava, constructional terrains (pillow-lava mounds), linear features, high-temperature vent sites, and inactive sulfide deposits. The pillow-lava mounds are subdivided into four separate ages based on reflectivity and the amount of sediment cover (Embley and Chadwick, 1994). Samples from high-temperature vent sites are designated in Table 1. Table and Brigadoon vent sites (not shown) are located 5 and 20 m north of Monolith Vent, respectively. Modified from Embley and Chadwick (1994).

VENT SITESThe Monolith Vent, constructed on the eastern edge of a fissure, consists of a basal mound

topped by diverse active chimneys (figs. 3A and B). The basal dimensions in 1991 were approximately 8 m by 5 m; the total height of the structure including chimneys was about 5 m. The hottest fluid temperatures in both 1990 and 1991, approximately 328°C, were measured at small side spouts near the lower western flank of the mound. Two smaller sulfide edifices, the Table and Brigadoon vents with maximum fluid temperatures between 275°C and 283°C, are located 5 and 20 m north of the Monolith edifice, respectively (figs. 2 and 3Q.

The Fountain Vent, located approximately 560 m north-northeast of the Monolith Vent (fig. 2), consists of two active sulfide mounds on the east side of a fissure. In 1991 the larger edifice was approximately 5 m in diameter at the base and 4 m in height, and much of the upper part was covered by robust tube-worm colonies (fig. 4A). The maximum hydrothermal fluid temperatures measured at Fountain Vent is 312°C.

The Pipe Organ vent field occurs in a fissure along the eastern margin of the sheet flow (fig. 2). In 1991, approximately 20 active sulfide chimneys were present in a cluster trending north-northeast parallel to the ridge axis. The sulfide structures consisted of spindly columns to 0.1 m in diameter and coalesced chimneys to 0.5 m in diameter (fig. 4#); the maximum chimney heights were 12 m. The maximum temperature of 261°C was measured in fluid discharging from a 4-m-tall chimney.

Inactive sulfide pinnacles up to 14 m in height are present along the northern and eastern edge of the sheet flow and in fissured terrain north of the Monolith Vent (figs. 2 and 4Q. Field relations and Pb-210 analyses indicate that these sulfide structures represent an earlier hydrothermal episode that predated the sheet flow eruption (Koski and others, 1994).

DESCRIPTION OF CHIMNEY SAMPLES

The chimney samples can be classified into four categories based on their morphology, composition, texture, and fluid temperatures. Type I, Type n, and Type III chimneys formed at high-temperature vent sites whereas Type IV chimneys represent the earlier lower-temperature hydrothermal event. Table 1 is a summary of chimney characteristics. The location, classification, fluid temperatures, and descriptions of the chimney samples are presented in Table 2. Sample locations are shown in Figure 2.

FIGURE 3. Alvin photographs of high-temperature vent sites and inactive sulfide chimney. A. View of south side of Monolith Vent, in 1990, showing active 1 -m-high Type I chimney in foreground and cluster of chimneys including active Type II chimney on east side of mound. B. A large, bulbous Type II beehive chimney (about 1m in height) as seen in 1991, venting diffusely at the base of the northern edifice at Monolith Vent. C. Diffuse venting from small (0.5-m-high) Type III chimneys at Table Vent, 5 m north of the Monolith edifice.

FIGURE 4. A. View of north side of Fountain Vent with dense covering of tube worms and small active beehive chimneys near the top. Width of mound approximately 5 m. B. Coalesced chimneys at Pipe Organ Vent coated with Fe oxyhydroxides and bacteria. Maximum width of coalesced chimney at right center is about 0.5 m. C Inactive Type IV sulfide pinnacle, 1 m in height, with a few sessile organisms.

TABLE 1. Characteristics of Four Chimney Types

Characteristics

Form

Substrate

Type I

Columnar- cylindrical

Sulfide mound

Type II

Bulbous ("Beehive")

Sulfide mound

Type IE

Columnar- spindly

Basalt

Type IV

Pinnacle

Basalt

Temperature (°C) 310 - 328

or chimney

293-312 261 - 276 < 250 (est.)

Fluid Flow Focused, rapid Diffuse, slower Focused, slow Diffuse (?), slowthan Type I

Type I ChimneysType I chimneys are tubular structures that vent focused high-temperature fluid at the

Monolith Vent. Two samples were collected one year apart from the same orifice: the central part of a 1-m-tall chimney in 1990 (ALV2259-1, fig. 3A) and a 0.2-m-tall chimney (ALV2429-1) in 1991. Both samples display a tubular structure and a smooth-walled open channelway (figs. 5A and B). In cross section, the chimneys are concentrically zoned with an inner wall of massive chalcopyrite with minor pyrite and bornite, a wide middle wall of sphalerite, wurtzite, chalcopyrite, pyrite, and anhydrite, and a relatively narrow outer wall of marcasite, pyrite, sphalerite, and barite. The measured temperature of fluids venting from these chimneys was 310° in 1990 and 1991 (Koski and others, 1994).

Type n Chimneys (Beehive Structures)Chimneys with a bulbous form and circumferential ribbing pattern are referred to as Type

II or "beehive" structures. They occur on the Monolith and Fountain sulfide mounds (figs. 3A, B, and 4A) and on top of some of the chimneys at the Pipe Organ Vent. Type n chimneys vent fluid at temperatures between 293° and 312°C through their porous tops and side walls. The active chimneys consist of a fragile anhydrite-rich shell containing minor pyrite, sphalerite, wurtzite, and chalcopyrite (fig. 5Q. Porosity of shell fragments are about 30%. A beehive structure at the north end of the Monolith Vent is topped by small columnar anhydrite chimneys (fig. 3B). Fossil Type n chimneys (e.g. sample ALV2442-7) are plugged by concentric layers of massive Zn sulfides, mostly sphalerite exhibiting a range of dendritic, colloform, and subhedral-granular textures.

A large high-temperature (314°C) chimney from Monolith Vent (sample ALV2433-3D) has a composite morphology with both Type I and Type II features. The chimney has the external shape and ribbing of a beehive structure, but the massive layers of chalcopyrite and anhydrite surrounding the large open channelway are more characteristic of Type I chimneys (fig. 6A). This hybrid chimney probably formed during a transition from Type n to Type I conditions at the vent (Koski and others, 1994).

A 10 cm Scale^H1 WZBIWIMl

ALV2259-1A

JALV2429-1

FIGURE 5. Photographs of chimney samples. A, B. Cross sections of Type I chimneys sampled from the same orifice at Monolith Vent (fig. 3A.). ALV2259-1A sampled in 1990 has a central channelway enclosed by a thin layer of chalcopyrite (light gray), wide Zn-sulfide-rich zone (gray), and a thin crust of partially oxidized pyrite and marcasite. ALV2429-1 sampled in 1991 has a thick inner layer of chalcopyrite (light gray) with a narrow outer layer of anhydrite+sphalerite. C. ALV2433-2C is a Type II anhydrite rich wall fragment with rib structures sampled in 1991. White patches are pure anhydrite.

B

AI VA4-31-3K

ALV2435-9A-1C-210 cm Scale

FIGURE 6. A. Cross section of sample ALV2433-3D with both Type I and Type II characteristics.The central channelway is enclosed, in sequence, by a layer of chalcopyrite and pyrite (medium gray), a wide anhydrite-rich layer (light gray), and a Zn-sulfide-rich shell (dark gray). D. Sample ALV2437-3A is an inactive Type [II coalesced chimney structure from Pipe Organ Vent that is predominantly Zn sulfides with numerous small channelways and outer, partly oxidized crust of marcasite and pyrite Scale units are 1 cm. C. ALV2435-9A-1C is a Type IV chimney in which the central channelway and smaller conduits are infilled by colloform amorphous silica (white).

TA

BL

E 2

. D

escr

iptio

ns o

f C

him

ney

Sam

ples

Sam

ple

Num

ber

ALV

2078

-2A

2

ALV

2078

-2B

2

Lat

itude

Lo

ngitu

de

Chi

mne

y M

easu

red

°N

°W

type

and

W

ater

activ

ity'

Tem

pera

ture

44°5

4'49

" 13

0°

IV14

'15"

(i

)

44°5

4'49

" 13

0°

IV14

'15"

(i

)

Wt.

Min

eral

ogy2

G

ener

al D

escr

iptio

ns(k

g)

0.75

py

, m

e, s

i, w

t, sp

, To

p of

50-

cm-ta

ll, c

him

ney

with

kno

bby

prot

uber

ance

s;gl

, ba

, Fe

ox.

pr

edom

inan

tly F

e su

lfide

s in

con

cent

ric r

ings

aro

und

cond

uits

fille

d w

ith a

mor

phou

s si

lica.

O

rang

e Fe

-oxy

hydr

oxid

e co

atin

gan

d fo

ssili

zed

wor

m t

ubes

are

fou

nd o

n th

e su

rfac

e of

the

Fe-

sulfi

de c

rust

. C

him

ney

loca

ted

on ju

mbl

ed s

heet

flo

ws.

Leng

th =

26

cm,

diam

eter

= 8

cm

.0.1

py

, m

e, s

i, ba

, sp

, To

p 0.

3 m

of

a 7-

m-ta

ll ch

imne

y w

ith k

nobb

y pr

otub

eran

ces;

clay

, su

l, Fe

ox.

si

mila

r to

2A

but

with

a t

hick

er F

e-ox

yhyd

roxi

de c

oatin

g.In

terio

r co

nsis

ts o

f de

nse,

col

lofo

rm F

e su

lfide

s w

itham

orph

ous

silic

a lin

ing

num

erou

s co

ndui

ts a

nd o

ld w

orm

tub

est

ruct

ures

. C

him

ney

loca

ted

near

ALV

2078

-2A

2.

Leng

th =

27

cm,

diam

eter

= 8

cm

.A

LV20

81-1

B

44°5

8'33

" 13

0°

IV12

'30"

(i

)py

, m

e, s

i, sp

, w

t, W

all

frag

men

t fr

om t

op o

f 8-

m-ta

ll ch

imne

y.

Inte

rior

is

cp,

ba,

Fe o

x.

pred

omin

antly

den

driti

c Fe

sul

fides

with

num

erou

s ri

ng-l

ike

stru

ctur

es a

roun

d ch

anne

lway

s.

Bla

ck c

oatin

g (M

n ox

ide?

) on

th

e ex

terio

r. C

him

ney

loca

ted

on o

lder

sed

imen

t co

vere

d,

___________pil

low

lav

as.

Dim

ensi

ons:

25

cm x

20

cm x

8 c

m._

__

__

__

0

ALV

2081

-2B

44

°58'

33"

130°

IV

I2'2

0"

(i)

0.5

py,

me,

si,

wt,

sp,

15 c

m t

all

spire

of

a sm

all

knob

by c

him

ney.

In

teri

or h

as a

Fc o

x.

dens

e, c

ryst

allin

e py

rite

+mar

casi

te r

im (

1 to

4 c

m)

surr

ound

ing

botry

oida

l su

lfide

s lin

ing

num

erou

s sm

all

cent

ral

cond

uits

. Fe

- su

lfide

cru

st c

oate

d w

ith F

e ox

yhyd

roxi

des,

wor

m t

ubes

, an

d sp

onge

atta

chm

ents

. Sa

mpl

e lo

cate

d in

a f

ield

of

10 t

o 12

ch

imne

ys e

ach

< 1

m h

igh

risin

g ou

t of

sed

imen

t co

vere

d_______________pil

low

lav

as.

Leng

th =

15

cm,

diam

eter

= 5

cm

. ______

ALV

2093

-2B

un

know

n un

know

n IV (i

)25

py

, m

e, s

i, sp

, w

t, (e

st.)

Fe o

x.U

pper

mos

t 0.

3 m

of

5-m

-tall,

kno

bby

chim

ney

topp

ed b

y m

ultip

le s

pire

s.

Inte

rior

pre

dom

inan

tly F

e su

lfide

in

conc

entri

c rin

gs a

roun

d m

ultip

le c

ondu

its f

illed

with

am

orph

ous

silic

a an

d co

arse

cry

stal

line

sulfi

des.

Fe

oxy

hydr

oxid

es a

nd s

pars

e w

orm

ca

sing

s on

ext

erio

r. Sp

ires

are

loca

ted

on p

illow

lav

as,

but

exac

t lo

catio

n un

know

n.

Dim

ensi

ons:

64

cm x

20.

5 cm

x 2

9 cm

.

TA

BL

E 2

. D

escr

iptio

ns o

f C

him

ney

Sam

ples

(C

ontin

ued)

Sam

ple

Num

ber

ALV

2094

-1A

1

AL

V20

94-1

B

ALV

2094

-4A

1 an

d A

LV

2094

-4B

1

ALV

2258

-1

ALV

2259

-1

Mon

olith

Ven

t

AL

V22

59-2

M

onol

ith

Ven

t3

Lat

itude

L

ongi

tude

C

him

ney

Mea

sure

d °N

°W

ty

pe a

nd

Wat

er

activ

ity1

Tem

pera

ture

44°5

8'50

" 13

0°

IV

12'2

1"

(i)

4405

8'50

" 13

0°

IV

12'2

1"

(i)

44°5

9'19

" 13

0°

III

12-0

8"

(i)

44°5

9'05

" 13

0°

IV

12'2

8"

(i)

4405

9-24

" 13

0°

I 31

0-32

0 12

-05"

(a

)

44°5

9'24

" 13

0°

II 12

'05"

(i

)

Wt.

Min

eral

ogy2

G

ener

al D

escr

iptio

n (k

g) 30

py,

wt,

si,

me,

sp,

K

nobb

y ch

imne

y, 5

0-cm

-hig

h, t

hat

term

inat

es i

n m

ultip

le

(est

.)

cp,

Fe o

x.

spir

es.

Inte

rior

is

dend

ritic

Fe

sulf

ides

in

conc

entr

ic r

ings

. C

ondu

its a

re l

ined

with

am

orph

ous

silic

a.

Fe-o

xyhy

drox

ides

co

atin

g an

d w

orm

tub

es o

n ex

teri

or.

Chi

mne

y is

loc

ated

alo

ng

a fr

actu

re i

n lo

bate

flo

ws.

L

engt

h =

50 c

m,

diam

eter

= 1

5 cm

.0.

1 m

e, w

t, sp

, Fe

ox.

Fr

agm

ents

of

smal

l ch

imne

y.

Com

pose

d of

fin

e cr

ysta

lline

Fe

sulf

ides

. C

oars

er-g

rain

ed F

e su

lfid

es i

n co

ndui

t. Pa

tchy

Fe-

ox

yhyd

roxi

des

coat

ing

on e

xter

ior.

Sam

pled

fro

m a

2-t

o 3-

m-

tall

chim

ney

adja

cent

to

AV

L20

94-1

A.

Dim

ensi

ons:

6 c

m x

3

cm x

3 c

m.

4A -

7

sp,

wt,

py,

me,

si,

Wea

ther

ed,

arcu

ate

frag

men

ts o

f an

old

, ho

llow

chi

mne

y.

4B -

ba

, an

h, g

al,

Mn

Frag

men

ts c

ompo

sed

of d

ense

, al

tern

atin

g la

yers

of

dend

ritic

3.

72

ox.

Zn

sulf

ides

. E

xter

ior

is c

oate

d w

ith M

n ox

ide

with

sca

ttere

d (e

st.)

w

orm

tub

es,

spon

ge a

ttach

men

ts,

and

fora

min

ifer

a.

Chi

mne

ys

loca

ted

at t

he c

onta

ct b

etw

een

old

and

new

pill

ow l

avas

. D

imen

sion

s: 4

A1

= 30

cm

x 2

3 cm

x 2

cm

, 4B

1 =

30 c

m x

10

cm x

3 c

m.

2.58

py

, m

e, s

i, w

t, sp

, C

olum

nar

chim

ney,

30-

cm h

igh,

with

pro

tube

ranc

es.

Inte

rior

Fe

ox.

pr

edom

inan

tly d

ense

Fe

sulf

ides

in

conc

entr

ic r

ings

aro

und

cond

uits

tha

t ar

e lin

ed w

ith b

otry

oida

l Z

n su

lfid

es.

Bla

ck

oxyh

ydro

xide

coa

ting

on e

xter

ior

surf

ace.

W

orm

tub

es a

nd

spon

ge a

ttach

men

ts p

rese

nt.

Loc

ated

on

a se

dim

ent-

cove

red

shee

t fl

ow.

Len

gth

= 12

.5 c

m,

diam

eter

= 7

cm

.10

.53

cp,

sp,

wt,

py,

Mid

dle

part

of

tubu

lar

chim

ney.

Z

oned

int

erio

r ha

s 4-

cm-w

ide

me,

anh

, bn

, cv

, la

yer

of d

ense

, an

hydr

ite a

nd Z

n su

lfid

es e

nclo

sing

1 c

m t

hick

cl

ay,

ba,

gl,

Fe

laye

r of

coa

rse,

gra

ined

Cu-

Fe s

ulfi

de.

Cen

tral

cha

nnel

way

is

ox.

5.5

cm x

3.5

cm

. Pa

rtly

oxi

dize

d Fe

-sul

fide

cru

st h

as a

bund

ant

embe

dded

wor

m c

asin

gs.

Sam

pled

fro

m t

he t

op o

f so

uthe

rn

end

of s

ulfi

de m

ound

. D

imen

sion

s: 4

5 cm

x 1

1 cm

x 8

cm

.0.

91

sp,

me,

py,

wt,

Arc

uate

fra

gmen

ts o

f ou

ter

chim

ney

wal

l co

mpo

sed

of d

ense

, an

h.

coar

se-g

rain

ed Z

n su

lfid

es.

Rem

nant

cru

st o

f Fe

sul

fide

pr

esen

t w

ithin

fra

gmen

ts.

Thi

n cr

ust

of b

lack

bot

ryoi

dal

sulf

ide

with

pat

ches

of

sulf

ur o

n ex

teri

or.

Sam

pled

at

base

of

the

edif

ice

on e

aste

rn s

ide.

D

imen

sion

s of

lar

gest

fra

gmen

ts:

19 c

m x

12

cm x

3 c

m.

TA

BL

E 2

. D

escr

iptio

ns o

f C

him

ney

Sam

ples

(C

ontin

ued)

Sam

ple

Num

ber

AL

V22

61-2

T

able

Ven

t

ALV

2265

-1

Mon

olith

V

ent3

AL

V22

66-3

Lat

itude

L

ongi

tude

°N

°W

44°5

9'24

" 13

0°

12'0

8"

4405

9-24

- 13

0°

12'0

5"

44°5

9'43

" 13

0°

ll'S

l"

Chi

mne

y M

easu

red

type

and

W

ater

ac

tivity

1 T

empe

ratu

re

HI

276

(a)

III (i)

IV (i)

Wt.

Min

eral

ogy^

(k

g)

0.59

sp

, w

t, an

h, p

y,

me,

icb

-cp,

Fe

ox.

2.5

sp,

me,

py,

wt,

icb-

cp,

Fe o

x.

16.9

4 py

, m

e, s

p, b

a, s

i, an

g, F

e ox

.

Gen

eral

Des

crip

tion

Out

er-w

all

frag

men

t of

chi

mne

y.

Inte

rior

gra

des

from

fin

e­

grai

ned

to c

oars

e cr

ysta

lline

Zn

sulf

ides

and

anh

ydri

te t

owar

d th

e ce

nter

. E

xter

ior

Fe s

ulfi

de c

rust

has

em

bedd

ed w

orm

ca

sing

s.

Chi

mne

y lo

cate

d be

twee

n cr

evic

es o

f ju

mbl

ed s

heet

fl

ows.

D

imen

sion

s: 1

1 cm

x 7

.5 c

m x

4 c

m.

Frag

men

t of

ina

ctiv

e ch

imne

y w

all.

Inte

rior

pre

dom

inan

tly

coar

se-g

rain

ed Z

n su

lfid

es w

ith e

llipt

ical

cav

ities

in

subp

aral

lel

row

s.

Ora

nge

2-m

m-t

hick

Fe

-oxy

hydr

oxid

e co

atin

g w

ith w

orm

cas

ings

on

exte

rior

. Fe

sul

fide

lay

er,

1 -cm

-thi

ck,

betw

een

the

Zn

sulf

ide

inte

rior

and

the

wea

ther

ed e

xter

ior.

Sam

pled

fro

m t

he b

ase

of M

onol

ith V

ent.

Dim

ensi

ons:

19

cm

x 1 3

cm

x 1

1 cm

.K

nobb

y, 6

0-cm

-hig

h, c

him

ney

term

inat

ing

in o

ne s

pire

with

nu

mer

ous

side

fla

nges

. In

teri

or i

s de

nse,

fin

ely

crys

talli

ne F

e

AL

V22

66-4

44

°59'

43"

130°

IV

H'5

1"

(i)

0.96

py

, m

e, w

t, si

, an

g, c

lay,

Fe

ox.

sulf

ide.

Num

erou

s co

ndui

ts l

ined

with

am

orph

ous

silic

a.

Ext

erio

r co

ated

with

ora

nge

Fe o

xyhy

drox

ides

and

wor

m

casi

ngs.

Sa

mpl

e lo

cate

d in

a f

ield

of

10 t

o 12

chi

mne

ys.

Dim

ensi

ons:

60

cm x

32

cm x

20

cm

._______________

Chi

mne

y fr

agm

ent

sim

ilar

to A

LV

2265

-1,

but

has

Fe

oxyh

ydro

xide

coa

ting

on s

ilica

with

in t

he c

entr

al c

ondu

it.

Als

o pa

tchy

Fe

oxyh

ydro

xide

coa

ting

on e

xter

ior.

Sa

me

loca

tion

as

AL

V22

66-3

. D

imen

sion

s: 7

cm

x 1

3 cm

x 1

3 cm

.A

LV

2269

-7

44°5

8'24

" 13

0°

II (?

) M

onol

ith

12'0

5"

(a)

Ven

t3

ALV

2429

-1

44°5

8'24

" 13

0°

I M

onol

ith

12'0

5"

(a)

Ven

t3

310

0.87

sp

, w

t, cp

, py

, A

rcua

te w

all

frag

men

ts f

rom

a h

igh-

tem

pera

ture

chi

mne

y.an

h.

Wal

l ha

s ri

b st

ruct

ure

and

cons

ists

of

inte

rgro

wn

dend

ritic

Zn

sulf

ide

and

anhy

drite

. C

oars

e-gr

aine

d w

urtz

ite l

inin

g ca

vitie

s.

No

exte

rior

cru

st p

rese

nt.

Dim

ensi

ons

of l

arge

st f

ragm

ent:

__

___________________15 c

m x

15

cm x

4 c

m._

__

__

__

__

__

__

__

__

__

__

__

31

0 0.

71

cp,

sp,

wt,

anh,

T

ubul

ar c

him

ney,

20

cm i

n he

ight

, w

ith z

oned

int

erio

r. A

1-

py,

si,

me,

cla

y,

cm-w

ide

laye

r of

anh

ydri

te a

nd Z

n su

lfid

e gr

ades

inw

ard

to a

1

ba,

cv,

ap,

Fe o

x.

In 2

cm

wid

e la

yer

of

coar

se-c

ryst

allin

e, c

halc

opyr

ite l

ayer

that

sur

roun

ds t

he 5

.5 c

m x

2.5

cm

ope

n ch

anne

lway

. Sa

mpl

ed

on t

he s

ame

orif

ice

as A

LV

2259

-1.

Dim

ensi

ons:

18

cm x

8 c

m

x 4

cm.

AL

V24

29-2

44

°59'

40"

130°

II

Foun

tain

Ven

t3

1T56

" (a

)1.

41

sp,

wt,

py,

me,

A

rcua

te s

labs

fro

m a

n ac

tive

beeh

ive

chim

ney.

O

ne-c

m-t

hick

(e

st.)

cp

, ba

. w

all

frag

men

t w

ith r

ibs

of d

ense

Zn

sulf

ides

. T

wo-

mm

-thi

ckcr

ust

of b

otry

oida

l Fe

sul

fide

with

enc

ased

wor

m t

ubes

.Sa

mpl

ed f

rom

the

nor

thea

ster

n ed

ific

e.

Dim

ensi

ons:

11

cm x

8cm

x 1

cm

.

TA

BL

E 2

. D

escr

iptio

ns o

f C

him

ney

Sam

ples

(C

ontin

ued)

Sam

ple

Lat

itude

Num

ber

°N

ALV

2431

-3A

-1

44°5

8'13

"Pi

pe O

rgan

Ven

t3

AL

V24

31-3

A-2

44

°58'

13"

Pipe

Org

anV

ent3

AL

V24

33-2

C

44°5

9'24

"M

onol

ithV

ent3

AL

V24

33-3

C

44°5

9'24

"M

onol

ithV

ent3

AL

V24

33-3

D

44°5

9'24

"M

onol

ithV

ent3

AL

V24

33-4

A

44°5

9'24

"M

onol

ithV

ent3

AL

V24

34-1

-20

44°5

9'24

"T

able

Ven

t

Lon

gitu

de°W 13

0°12

'45"

130°

12'4

5"

130°

12'0

5"

130°

12'0

5"

130°

12'0

5"

130°

1 205

"

130°

12'0

8"

Chi

mne

y M

easu

red

Wt.

type

and

W

ater

(k

g)ac

tivity

1 T

empe

ratu

re

III

-

2.1

(i)

(est

.)

m

-----

1.73

(i)

(est

.)

II 29

3-29

6 1.

52(a

) 11 30

3.4

0.5

(a)

1,11

314

10.6

5(a

) II 30

9 0.

61(a

)

HI

-

0.85

(i)

Min

eral

ogy2

G

ener

al D

escr

iptio

n

sp,

py,

me,

wt,

si,

The

top

of

coal

esce

d 4-

m-t

all,

colu

mna

r ch

imne

y st

ruct

ure.

anh.

In

teri

or i

s fi

ne-g

rain

ed Z

n su

lfid

es i

ncre

asin

g in

por

osity

tow

ard

cent

er.

Fe o

xyhy

drox

ides

, w

orm

cas

ings

, an

d fo

ram

inif

era

occu

r on

out

er w

all

of F

e su

lfid

es.

Sam

ple

loca

ted

in o

ldpi

llow

lav

as.

Dim

ensi

ons:

13.

8 cm

x5.

5 cm

x 7

.4 c

m.

sp,

py,

me,

wt,

si,

Sect

ions

of

coal

esce

d co

lum

nar

chim

ney

stru

ctur

e.

The

1-c

m-

anh.

th

ick

oute

r w

all

is d

ense

, co

arse

-gra

ined

, Fe

sul

fide

s.

Thi

sgr

ades

inw

ard

into

fin

e-gr

aine

d Z

n su

lfid

es.

The

cen

ter

has

1to

5 m

m w

ide

flui

d ch

anne

lway

s.

Fe-o

xyhy

drox

ides

and

wor

mca

sing

s on

the

ext

erio

r su

rfac

e of

Fe

sulf

ides

. D

imen

sion

s: 1

0cm

x 2

0 cm

x 1

1.5

cm

.an

h, p

y, s

p, c

p,

Arc

uate

2-c

m-t

hick

sla

bs f

rom

an

activ

e be

ehiv

e ch

imne

y.

Rib

wt,

po.

stru

ctur

e re

late

d to

Zn

sulf

ides

alte

rnat

ing

with

anh

ydri

te.

Sam

ple

loca

ted

on t

he s

outh

ern

end

of M

onol

ith V

ent.

Dim

ensi

ons

of la

rges

t fr

agm

ent:

12.2

cm

x 1

5.5

cm x

2 c

m.

anh,

sp,

py,

wt,

Arc

uate

sla

bs f

rom

an

activ

e be

ehiv

e ch

imne

y si

mila

r to

2C

.cp

. M

inor

cha

lcop

yrite

and

pyr

ite l

inin

g ca

vitie

s.

Sam

pled

at

the

base

of

a co

llaps

ed b

eehi

ve c

him

ney.

D

imen

sion

s: 1

3 cm

x7.

5 cm

x 2

cm

.cp

, an

h, s

p, p

y,

Bee

hive

-sha

ped

chim

ney

with

lar

ge o

rifi

ce (

5 cm

wid

e) l

ined

wt,

gyp,

si.

with

Cu-

Fe s

ulfi

des.

The

Cu-

Fe-s

ulfi

de l

ayer

gra

des

into

a 2

cm t

hick

, ri

ng o

f de

nse,

den

driti

c, a

nhyd

rite

and

Zn

sulf

ide.

The

re i

s a

shar

p bo

unda

ry b

etw

een

laye

rs.

Out

er w

all

surf

ace

has

abun

dant

Zn

sulf

ide

and

ribb

ed m

orph

olog

y.

Feox

yhyd

roxi

de c

oatin

g on

ext

erio

r su

rfac

e w

ith w

orm

tub

espr

esen

t. Sa

mpl

ed f

rom

clu

ster

of

activ

e ch

imne

ys o

n so

uthe

ast

side

. D

imen

sion

s: 4

4 cm

x 1

7 cm

x 2

2 cm

.sp

, py

, an

h, w

t, T

hree

spi

res,

app

roxi

mat

ely

10 c

m i

n he

ight

fro

m t

op o

f an

cp,

po.

activ

e be

ehiv

e ch

imne

y.

Wal

ls a

re a

nhyd

rite

and

Zn

sulf

ide.

Sam

pled

fro

m t

he n

orth

ern

side

of

mou

nd.

Ave

rage

dim

ensi

ons:

10

cm x

7 c

m x

3 c

m.

sp,

wt,

me,

py,

Fr

agm

ents

of

a ch

imne

y th

at g

rade

s in

war

d fr

om d

endr

itic

Zn

cp.

sulf

ides

to

fine

ly c

ryst

allin

e Fe

sul

fide

s lin

ing

chan

nelw

ays.

Tw

o-m

m-t

hick

cru

st o

f Fe

sul

fide

enc

rust

ed w

ith w

orm

tub

esan

d ba

cter

ial

mat

s.

Ave

rage

dim

ensi

ons:

8 c

m x

6 c

m x

5 c

m.

TA

BL

E 2

. D

escr

iptio

ns o

f C

him

ney

Sam

ples

(C

ontin

ued)

Sam

ple

Lat

itude

N

umbe

r °N

AL

V24

35-3

44

°59'

43"

AL

V24

35-8

44

°59'

55"

AL

V24

35-9

A

45°0

0'00

"

AL

V24

36-1

E

44°5

9I40

" Fo

unta

in V

ent3

AL

V24

36-1

F 44

°59'

40"

Foun

tain

Ven

t3

AL

V24

36-2

F 44

°59'

40"

Foun

tain

Ven

t3

Lon

gitu

de°W 13

0°

irsi

"

130°

1 1

'48"

130°

1 1

'39"

130°

130°

130°

11

'56"

Chi

mne

y M

easu

red

type

and

W

ater

ac

tivity

1 T

empe

ratu

re

IV (i) iv

_(i

) iv

_0) HI (i) 11

304-

311.

5 (a

)

HI (i)

Wt.

Min

eral

ogy2

G

ener

al D

escr

iptio

n (k

g) 5 py

, sp

, w

t, si

, m

e,

Top

of

25-c

m-t

all

knob

by c

him

ney.

In

teri

or is

pre

dom

inan

tly

(est

.)

ang,

Fe

ox.

Fe s

ulfi

des

form

ing

conc

entr

ic l

ayer

s ar

ound

cha

nnel

way

s lin

ed w

ith a

mor

phou

s si

lica.

Pa

tchy

red

dish

-bro

wn

Fe

oxyh

ydro

xide

s on

sur

face

has

wor

m t

ubes

and

for

amin

ifer

a.

Sam

ple

loca

ted

in j

umbl

ed s

heet

flo

ws.

L

engt

h =

13

cm

, di

amet

er =

1 5

cm

.0.

1 py

, m

e, s

p, w

t, si

, Fr

agm

ents

fro

m t

he t

ip o

f a

2-m

-tal

l ch

imne

y, l

arge

ly

ba,

Fe o

x.

com

pose

d of

Fe

sulf

ide.

A

mor

phou

s si

lica

in c

entr

al

chan

nelw

ay i

s co

ated

with

red

, Fe

-oxy

hydr

oxid

es.

One

-mm

- th

ick

botr

yoid

al F

e-su

lfid

e cr

ust

has

wor

m c

asin

gs a

nd

fora

min

ifer

a.

Isol

ated

chi

mne

y lo

cate

d in

jum

bled

she

et f

low

. Sp

onge

s, s

tarf

ish,

and

oth

er a

ttach

ed o

rgan

ism

s w

ere

rest

rict

ed

to t

he n

orth

sid

e of

this

chi

mne

y.

Dim

ensi

ons:

4 c

m x

4 c

m x

2

cm.

11.6

9 py

, m

e, s

i, sp

, w

t, K

nobb

y, 4

5-cm

-hig

h, c

him

ney

with

col

lofo

rm F

e su

lfid

es i

n an

g, F

e ox

. co

ncen

tric

lay

ers

arou

nd n

umer

ous

cond

uits

inf

illed

with

am

orph

ous

silic

a.

Surf

ace

has

crus

t of

Fe

sulf

ide

with

wor

m

casi

ngs

and

fora

min

ifer

a.

Sam

ple

is f

rom

top

of

a 1 1

-m-h

igh

chim

ney

loca

ted

on t

he e

dge

of a

fra

ctur

e an

d su

rrou

nded

by

jum

bled

she

et f

low

. D

imen

sion

s: 4

5 cm

x 1

9 cm

x 1

3 cm

.0.

15

sp,

wt,

py,

me,

A

17-

cm-h

igh

chim

ney

spir

e w

ith a

1 -c

m-t

hick

wal

l of

den

se,

(est

.)

icb-

cp.

fine

ly c

ryst

allin

e Z

n su

lfid

es t

hat

part

ially

fill

a 1

-to 2

-cm

-wid

e ce

ntra

l ch

anne

lway

. Pa

tchy

, bo

tryo

idal

, ox

idiz

ed,

Fe-s

ulfi

de

crus

t. Sp

ire

is l

ocat

ed a

t th

e to

p of

the

nort

h si

de o

f th

e la

rge

mou

nd.

Dim

ensi

ons:

17

cm x

4 c

m x

4 c

m.

0.25

sp

, an

h, p

y, m

e,

Thr

ee a

rcua

te f

ragm

ents

fro

m a

n ac

tive

beeh

ive

chim

ney

wt,

icb-

cp.

com

pose

d pr

edom

inan

tly o

f de

nse,

fin

ely-

grai

ned

Zn

sulf

ides

an

d an

hydr

ite.

Out

er w

all

is a

thi

n la

yer

of F

e su

lfid

es.

Sam

pled

fro

m n

orth

sid

e of

larg

e m

ound

. D

imen

sion

of

larg

est

frag

men

t: 1 3

cm

x 6

cm

x 6

cm

.1.

32

sp,

py,

me,

wt,

Wal

l fr

agm

ents

fro

m a

bee

hive

chi

mne

y co

mpo

sed

of Z

n, F

e,

(est

.)

icb-

cp,

Fe o

x.

and

Cu-

Fe s

ulfi

des.

W

orm

tub

es i

ncor

pora

ted

in o

xidi

zed

Fe-

sulf

ide

crus

t. Sa

mpl

ed f

rom

the

sou

th s

ide

of la

rge

mou

nd.

Dim

ensi

ons

of la

rges

t fr

agm

ent:

12 c

m x

6 c

m x

2 c

m.

TA

BL

E 2

. D

escr

iptio

ns o

f C

him

ney

Sam

ples

(C

ontin

ued)

Sam

ple

Num

ber

AL

V24

37-3

APi

pe O

rgan

Ven

t3

AL

V24

42-7

Mon

olith

Ven

t3

AL

V24

44-3

A

Lat

itude

L

ongi

tude

C

him

ney

Mea

sure

d°N

°W

ty

pe a

nd

Wat

erac

tivity

1 T

empe

ratu

re

4405

8'13

" 13

0°

III12

'45"

(i

)

4405

9-24

- 13

0o

n

12'0

5"

(i)

44°

57' 1

0"

130°

III

12'5

1"

(i)

Wt.

Min

eral

ogy2

G

ener

al D

escr

iptio

n(k

g)

8.02

sp

, py

, m

e, s

i, po

, Se

ctio

n of

a 4

-m-h

igh

colu

mna

r st

ruct

ure

form

ed b

y 2

icb-

cp,

cv,

coal

esce

d ch

imne

ys.

Com

pose

d pr

edom

inan

tly o

f Z

n su

lfid

esFe

ox.

w

here

por

osity

inc

reas

es f

rom

rim

to

the

cent

er.

Fe s

ulfi

defo

rm c

once

ntri

c la

yers

aro

und

narr

ow c

ondu

its.

A t

hin

coat

ing

of F

e ox

yhyd

roxi

des

with

wor

m c

asin

g on

out

er F

e-su

lfid

e w

all.

Dim

ensi

ons:

41

cm x

12

cm x

20

cm.

64

sp,

wt,

py,

me.

L

arge

fos

sil

beeh

ive

chim

ney.

In

teri

or h

as v

aria

ble

poro

sity

with

con

cent

ric

laye

rs o

f Z

n su

lfid

e en

clos

ing

arcu

ate

cavi

ties.

Ext

erio

r ha

s 3-

mm

-thi

ck c

rust

of

botr

yoid

al F

e su

lfid

es a

ndw

orm

cas

ings

. C

him

ney

loca

ted

near

the

bas

e of

the

sout

hern

end

of s

ulfi

de m

ound

. L

engt

h: 6

5 cm

, ap

prox

imat

e di

amet

er:

40 c

m.

5.27

sp

, w

t, m

e, c

p,

Wea

ther

ed c

him

ney

frag

men

ts w

ith m

ultip

le c

ondu

its.

Lar

gely

po,

si,

Fe o

x.

com

pose

d of

Zn-

sulf

ide

with

min

or a

mou

nts

of C

u-Fe

sul

fide

s.W

orm

tub

es,

fora

min

ifer

a, a

nd b

acte

rial

fila

men

ts o

n su

rfac

esof

the

Fe-s

ulfi

de c

rust

. C

him

ney

loca

ted

in t

hin

shee

t fl

ows.

Dim

ensi

on o

f la

rges

t fr

agm

ent:

18 c

m x

20

cm x

15

cm.

'(a)

= ac

tive

chim

ney,

(i)

= in

activ

e ch

imne

y.2K

ey m

iner

alog

y de

term

ined

by

hand

spe

cim

en e

xam

inat

ion

and

anal

ysis

of

polis

hed

thin

sec

tions

: an

g =

angl

esite

, ap

= a

patit

e, a

nh =

anh

ydri

te,

ba =

bar

ite,

clay

= M

g- a

nd F

e-ri

ch c

lays

, cp

= c

halc

opyr

ite,

cv =

cov

ellit

e, F

e ox

= g

oeth

ite a

nd a

mor

phou

s Fe

oxy

hydr

oxid

es,

gl =

gal

ena,

gyp

= g

ypsu

m,

icb-

cp =

int

er-g

row

n is

ocub

anite

and

cha

lcop

yrite

, m

e =

mar

casi

te,

Mn

ox =

man

gane

se o

xide

, po

= p

yrrh

otite

, py

= p

yrite

, si

= am

orph

ous

and

opal

ine

silic

a, s

p =

spha

leri

te,

sul

= su

lfur

, w

t =

wur

tzite

.3P

ositi

on o

f M

onol

ith,

Foun

tain

, an

d Pi

pe O

rgan

ven

ts s

uppl

ied

by R

. E

mbl

ey,

wri

tten

com

mun

icat

ion,

199

4.

Type HI ChimneysType HI chimneys are typical of the Pipe Organ and Table vents, and are also the most

abundant chimney type in the southern Cleft segment of Juan de Fuca Ridge (Koski and others, 1984: Paradis and others, 1988). Type III chimneys located at Pipe Organ Vent are tall (to 12 m) columnar structures, often constructed of two or more coalesced chimneys. Chimneys present at Table Vent are small columnar structures up to one meter in height (fig. SCand 4B ).. Fluid venting through a Type HI chimneys at Pipe Organ Vent has a measured temperature of 261°C .

The chimneys typically have a thick-walled construction with narrow tortuous fluid channelways. The mineralogy of the chimney walls is dominated by dendritic sphalerite intergrown with subhedral to euhedral sphalerite, wurtzite, and subhedral pyrite. The narrow (1 to 5 mm) channelways are lined with concentric layers of sphalerite, isocubanite, and pyrrhotite. The chimney surfaces consist of a 1- to 2-mm-thick layer of Fe oxyhydroxides covering a 1-to 5- mm-thick layer of marcasite and pyrite (fig. 6B). Worm tubes, sponge attachments, foraminifera, and bacterial mats have been found on the exterior of Type El samples.

Type IV ChimneysMost of the inactive solitary chimneys located near the fissures and referred to as Type IV

have a distinctive low-temperature sulfide-silica-sulfate mineral assemblage. The chimneys are typically thick walled with a knobby exterior and numerous small fluid channelways (fig. 4Q. The most abundant sulfide minerals are colloform and subhedral pyrite and marcasite; coarse­ grained euhedral wurtzite and sphalerite are less abundant but concentrated around fluid channelways. Small blebs of chalcopyrite occur along the margins of wurtzite crystals in a few samples. Anglesite is the most abundant sulfate mineral, and forms subhedral to euhedral crystals interstitial to sulfides, especially around fluid channelways. Barite is present in the outer wall of several chimneys.

Open spaces and, especially, the interior channelways of most Type IV chimneys are coated or infilled with amorphous silica (fig. 6C). Amorphous silica textures typically are colloform or fibrous; the latter morphology has resulted from precipitation on the surfaces of filamentous bacteria.

BULK CHEMISTRY OF CHIMNEYS

Table 3 presents bulk chemical data for 23 chimney samples determined at the laboratories of the Geological Survey of Canada (GSC) and Bondar-Clegg & Company (BCC) in Ottawa, Canada. Major element oxides, Ag, Ba, Be, Co, Cr, Cu, Mn, Ni, Pb, Sc, Sr, V, Y, Yb, and Zr were analyzed by inductively coupled plasma/atomic emission spectrometry at GSC; As, Bi, Sb, Se, Te, and Mo by atomic absorption spectrometry at GSC; Br, Cd, Ce, Cs, Eu, Hf, Ir, La, Lu, Rb, Sm, Sn, Ta, Tb, Th, U, and W by neutron activation (except Cd, Sn, and W in samples ALV2429-1 and ALV2437-3A-2 by inductively coupled plasma/atomic emission spectrometry) at BCC; Fe (as FeO) and CO2 by wet-chemical methods at GSC; total S by a combustion/infra­ red method at GSC; and Au by a fire assay/DC plasma technique at BCC.

The two Type I samples from Monolith Vent have high but variable CaO, Cu, and Zn contents that reflect different proportions of anhydrite, chalcopyrite, and Zn sulfides in the chimneys. Pb, Ag, As, Ba, Co, and Sb are higher in the thicker-walled chimney (ALV2259-1). The active, anhydrite-rich Type H chimneys (ALV2261-2C and ALV2433-2C) have high Ca and Sr contents whereas samples of fossil beehive structures (e.g. ALV2259-2, ALV2436-1F, and ALV2442-7) contain much lower Ca and Sr and higher metal contents, especially Zn and Cd.

16

TABLE 3. Chemical Data for Hydrothermal Sulfide Chimney Samples

I I II II II II II II II II IIIChimneyType

Sample ALV2259 ALV2429 ALV2259 ALV2261 ALV2429 ALV2433 ALV2436 ALV2442 ALV2442 ALV2442 ALV2094 number -1 -1 -2 -2C -2 -2C-1B -IF -7A-3A -7A-3B -7A-3C -4A

wt%Si02TiO2A1203MgOCaONa2OK20CO2PlOs

FeCuZnPbS

AgAsAuBaBeBiBrCdCeCoCrCsEuHfIrLaLuMnMoNiRbSbScSeSmSnSrTaTbTeThUVwYYbZr

3.1n.d.0.220.040.950.270.130.20.05

13.78.60

34.10.06

34.0

150199

0.181100

0.1<0.2 345 8

1208

n.d. 31219 42

n.d.

n.d.0.8

n.d.

5.0<0.020.490.463.90.260.08 -

21.620.412.10.01

31.0

59540.06

36 <1

549 66 <5

110622 13 60

252<100

67 11

<20<5 38

2.5n.d.0.850.010.100.180.050.10.04

7.80.55

51.20.11

32.8

200376

0.28300n.d.<0.2 155-~ -10

120184 440.53 -2 - 5

n.d.n.d.n.d.

0.15n.d.0.050.04

28.80.240.080.10.04

4.90.1211.70.02

27.3

47440.12

3600.3

<0.2 12-- ~9 606

n.d. 100.34

1900

n.d. 1

n.d.n.d.

<0.5<0.02<0.20.050.130.310.11--0.04

11.30.44

49.70.09

33.5

84134

0.17<30<0.5 22

1910<2927

<10<1.9<1<3<0.05

<10<0.41802315

<1727<0.5

10.15

<10023<0.5<1.016<0.8<0.5<541<5<0.5<10

<0.5<0.02<0.20.34

30.30.220.08~0.04

7.20.695.00.01

27.8

13450.03

60<0.5 14

250<1610101

<1<1<0.05

<10<0.2<602111<551.170.34

<1001700<0.5<0.5

<10<0.2<0.2<543<5<0.5<10

0.6<0.020.24

<0.040.630.180.05~0.04

12.90.59

46.70.06

34.7

76180

0.19<30<0.5 5

>2000<3929

<10<2.5<1<4<0.11<10<0.61801811

<2331<0.5

10.19

<10033<0.5<1.3<10<1.1<0.7<562<5<0.5<10

1.30.020.830.050.070.180.06--0.03

40.10.03.20.07

48.7

6590.01

770<0.5 1528

<3441

<102

<16

<0.05<10<0.418049

<10<16

20.810.18

<10052<0.5<0.5<10<0.83.2

<5233<5<0.519

<0.5<0.02<0.20.070.070.230.09~0.05

2.50.3

60.70.18

32.7

180520.04

<30<0.5 18

1040<3936

<10<2.8<1<4<0.12<10<0.6

<60513

<2518<0.50.280.15

<100<20<0.5<1.5<20<1.2<0.7<567<5<0.5<10

1.3<0.020.390.040.060.210.07 0.04

6.91.2

55.30.03

29.8

84124

0.23<30<0.5 3

>2000<4018

<10<2.7<1<4<0.12

<10<0.6601012

<2346<0.55

<0.10<100<20<0.5<1.7<20<1.2<0.7<543<5<0.5<10

13.9n.d.0.150.140.170.590.150.60.22

9.00.35

40.40.22

28.1

720360

0.255100

n.d.0.06 1324 -1

100021n.d.

117

n.d. 43 22 0.2-

n.d. = not detected; ~ = no data

17

TABLE 3. Chemical Data for Hydrothermal Sulfide Chimney Samples (Continued)

III III III IV IV IV IV IV IV IV IV IVChimneyType

Sample ALV2265 ALV2269 ALV2437 ALV2078 ALV2081 ALV2081 ALV2093 ALV2258 ALV2266 ALV2435 ALV2435 ALV2435 number -1 -7 3A - 2 -2A-2 -IB -2B -2B -1 - 3A -3-1 -3-2 -9A-1F

wt%Si02Ti02A1203MgOCaONa2OK20C02P205

FeCuZnPbS

AgAsAuBaBeBiBrCdCeCoCrCsEuHfIrLaLuMnMoNiRbSbScSeSmSnSrTaTbTeThUVwYYbZr

1.04n.d.0.120.070.100.310.120.50.05

9.00.58

48.30.06

34.4

99136

0.11920

n.d.<0.2 ~

286

10

12021n.d.

230.33 4 ..n.d. n.d.n.d.n.d.

0.36n.d.0.120.020.080.180.070.10.04

5.70.29

54.80.16

33.5

280375

0.19270

n.d.<0.2

135 9

60145

56n.d.2 2

n.d.

n.d.n.d.n.d.

26.7<0.020.040.100.360.940.11 -

11.80.33

39.60.14

26.7

203239

0.5198

<1

765

13555

<5._

70120

8

34

13345

<100

164

<2<20<5

<5

35.6n.d.1.40.850.300.460.450.60.14

18.70.155.22.7

23.4

860195

0.3310000

n.d.0.04 6

26

110034n.d.

134 6

290

15 n.d.-

31.6n.d.0.800.030.210.270.260.50.14

26.60.132.80.07

32.0

210204

0.2730n.d.0.02 48 ~ ~

10008117~

30 3

12 ~6 n.d.-

32.7n.d.1.20.040.230.370.430.40.16

22.70.104.30.38

28.7

310288

0.44490

n.d.0.23 5

24

7208412

47

12

67 -

14 n.d.--

34.6n.d.0.900.160.240.850.450.50.20

21.10.073.90.40

26.5

180267

0.29660

n.d.0.13 5

24- -

720926

35 8

85

22~ n.d.-

35.8n.d.0.920.020.180.280.250.20.02

25.30.020.890.56

31.3

550127

0.3040n.d.<0.2 ~

220n.d. 6

50076n.d.

1130.29«

46 n.d. n.d.n.d.n.d.

34n.d.1.70.090.340.540.350.60.05

18.40.128.22.5017.8

590327

0.40170n.d.<0.2

577 7

110965

2180.3

32

97 - 5 n.d.n.d.n.d.

36.3<0.020.890.040.210.420.25~0.07

21.10.073.61.9

30.2

340780.28

<30<0.5

25<12<304515<1.1<2<4<0.05<10

0.56607420

<17731.350.18

<10046<0.5<0.5<10<0.90.9

<5216<5<0.5<10

28.9<0.020.510.060.180.440.27~0.10

28.20.062.20.9

29.8

320960.30

30<0.5

2313

<303119<1.1<2<4<0.05<10<0.41806823

<17750.94

<0.10<100

45<0.5<0.5<10<0.92.2

11217<5<0.5<10

61.6<0.020.990.200.220.530.30~0.09

13.90.020.70.31

14.2

77162

0.26350<0.5

17<5<238813<0.5<15

<0.05<10<0.266067

<10<13830.68

<0.22<100

72<0.5<0.5<10<0.86.56

465<5<0.5<10

n.d. = not detected = no data

18

The four Type III chimneys have high Zn/Cu ratios (>80) and high Ag contents (average 325 ppm) similar to Zn-sulfide-rich chimneys recovered from the southern Cleft segment of Juan de Fuca Ridge (Koski and others, 1984; Bischoff and others, 1983). Type IV chimneys, characterized by the low-temperature mineral assemblage marcasite + pyrite + wurtzite + amorphous silica + anglesite, have high SiC>2 (maximum 61.6%, average 36.7%), Pb (2.7%, 1.1%), Ag (860 ppm, 382 ppm), Sb (218 ppm, 90 ppm), Mn (1100 ppm, 628 ppm), Mo (96 ppm, 75 ppm), and Cr (26 ppm, 15 ppm), and low Cu (0.15%, 0.08%). The relatively high Mn contents are probably related to thin surface coatings of Mn oxide.

SUMMARYThe four chimney types represent deposition of hydrothermal minerals in response to

distinctly different fluid flow characteristics (Koski and others, 1994). Type I chimneys result from the rapid focused flow of high-temperature (>310°C) fluids through the Monolith sulfide mound. In contrast, Type II beehive structures form where slightly lower temperature (293° to 312°C) fluids are discharged more diffusely through mounds and chimneys. Type HI chimneys form from focused flow of lower-temperature (261° C) Zn-rich fluids through basaltic substrates. Similarly, Type IV chimneys are built directly on volcanic substrates, but their mineral assemblages, textures, lack of mineral zonation, and fluid inclusion characteristics (K.-Y. Lee, unpublished data, 1993) indicate deposition from hydrothermal fluids at low temperatures (<250°C) and sluggish flow rates.

ACKNOWLEDGMENTSWe thank Robert Embley and Gary Massoth for the opportunity to study samples

collected during three cruises to the southern Juan de Fuca Ridge funded by the NOAA VENTS Program. R. Embley provided the bathymetric map shown in Figure 1, a geologic map presented in modified form as Figure 2, and new positions for the three vents. lan Jonasson of the Geological Survey of Canada provided many of the onboard sample descriptions. We wish to thank Alice Davis of Pacific Marine Geology for her indepth review of the manuscript.

19

REFERENCES Baker, E.T., Lavelle, J.W., Feely, R.A., Massoth, G.J., and Walker, S.L., 1989, Episodic venting

of hydrothermal fluids from the Juan de Fuca Ridge: Journal of Geophysical Research, v.94, p. 9237-9250.

Baker, E.T., Massoth, G.J., and Feely, R.A., 1987, Cataclysmic venting on the Juan de FucaRidge: Nature, v. 329, p. 149-151.

Bischoff, J.L., Rosenbauer, R.J., Aruscavage, P.J., Baedecker, P.A., and Crock, J.G., 1983, Sea- floor massive sulfide deposits from 21°N, East Pacific Rise; Juan de Fuca Ridge; andGalapagos Rift: Bulk chemical composition and economic implications: EconomicGeology, v. 78, p. 1711-1720.

Chadwick, W.W., Embley, R.W., and Fox, C.G., 1991, Evidence for volcanic eruption on thesouthern Juan de Fuca Ridge between 1981 and 1987: Nature, v. 350, p. 416-418.

Embley, R.W., and Chadwick,. W.W., 1994, The volcanic and hydrothermal setting of thenorthern Cleft Segment: A site of sea-floor spreading during the 1980s, Journal ofGeophysical Research., in press.

Embley, R.W., Chadwick, W.W., Perfit, M.R., and Baker, E.T., 1991, Geology of the northernCleft segment, Juan de Fuca Ridge: Recent lava flows, sea-floor spreading, and theformation of megaplumes: Geology, v. 19, p. 771-775.

Koski, R.A., Clague, D.A., and Oudin, E., 1984, Mineralogy and chemistry of massive sulfidedeposits from the Juan de Fuca Ridge: Geological Society of America Bulletin, v. 95, p.930-945.

Koski, R.A., Jonasson, I.R., Kadko, D.C., Smith, V.K., and Wong, F.L., 1994, Compositions,growth mechanisms, and temporal relations of hydrothermal sulfide-sulfate-silicachimneys at the northern Cleft segment, Juan de Fuca Ridge: Journal of GeophysicalResearch, in press.

Paradis, S., Jonasson, I.R., Le Cheminant, G.M., and Watkinson, D.H., 1988, Two zinc-richchimneys from the Plume Site, southern Juan de Fuca Ridge: Canadian Mineralogist, v.25, p. 637-654.

20