n27
CanadianMineralogist
Vol. 30,pp. 1127-1142(1992)
FROMTHEKIDDCREEK
BERTHIERINE
AND METAMORPHIC
HYDROTHERMAL
ONTARIO
TIMMINS,
MASSTVE
SULFIDEDEPOSIT.
VOLCANOGENIC
JOHNF.SLACK
Virginia22092,U.S.A.
NationnlCenter,
Mail Stop954,Reston,
U.S.Geological
Survey,
WEI-TEH JIANG ANDDONALD R. PEACOR
Depamnent of Geological Sciences, University of Michigan, Ann Arbor, Michigan 48109, U.S.A.
PATRICKM. OKITA*
U.S.GeologicalSurvey,National Center,Mail Stop954, Reston,Virginia 22092,U.S.A.
ABSTRACT
Berthierine,a 7 A pe-Al memberof the serpentinegroup, occursin the footwall stringerzone of the ArcheanKidd Creek
with quartz,muscovite,chlorite,pyrite, sphalerite,chalcopyrite,andlocal tourmaline'
massivesulfidedeposit,Ontario,associated
cassiterite,andhalloysite.Berthierinehasbeenidentifiedby thelack of 14A basalreflectionsonX-ray powderdiffractionpattems,
by its composition(electron-microprobedata), and by transmissionelectron microscopy(TEM). Peoogaphic and scanning
eiectronmicroscopic(SEM) studiesreveal different types of berthierineocculrences,including interlayerswithin and rims on
deformedchlorite, intergrowthswith muscoviteand halloysite,and discretecoarsegrains.TEM imagesshow thick packetsof
berthierineand chlorite that are parallel or relatedby low-angleboundaries,and layer terminationsof chlorite by berthierine;
mixedJayer chlorite-berthierinealso is observed,intergrown with Fe-rich chlorite and berthierine.End-member(Mg-free)
berthierineis presentin smalldomainsin two samples.The Kidd Creekberthierineis chemicallysimilar to berthierinefrom other
localities,and to Fe-rich chlorite from a variety of geologicalsettings.This is the first reportedoccurence of berthierinefrom
volcanogenicmassivesulfide deposits.Textural relationssuggestthat most of the Kidd Creekberthierineformed as a primary
hydrothermalmineral at relatively high temperatures(*350"C) in the footwall stringerzone,probablyby the replacementof a
pie-existingaluminousphasesuchasmuscoviteor chlorite.However,theintergrowthtexturesobservedby SEM andTEM suggest
ofchlorite.Thedifficultyofidentifyingberthierine
replacement
originatedbysyn-orpost-metamorphic
thatsomeoftheberthierine
thatmuchofthe Fe-richchloritedescribedfrom modem
by routinepetrographic,X-ray, andelecfon-microprobemethodssuggests
andancientmassivesulfide depositsmay insteadbe berthierine.
data X-raY
Keywords:berthierine,chlorite,volcanogenicsulfidedeposit,fiansmissionelectronmicroscopy,electron-microprobe
powderdiffraction, Kidd Creekmine,Timmins, Ontario.
SonaN.lans
On trouve la berthierine,membreFe-Al I 7 A du groupede la serpentine,dansla zonede minerai en veinulesde la paroi
infdrieuredu glte archdende sulfuresmassifsde Kidd Creek,en Ontario,en associationavecquartz,muscovite,chlorite,pyrite,
sphal6rite,et chalcopyrite,avecprdsencelocalede tourmaline,cassitdriteet halloysite.On reconnaitla berthierinepar I'absence
6lectronique),
i la microsonde
d^'uneraieayantunevaleurd de-14A surle clich6de diffractionX, par sacomposition(donn6es
et par 6tudei au microscopedlectroniquepar transmission.Des6tudespdrographiqueset au microscope6lectroniquei balayage
montrentque la berthierinesepr6sentesousplus d'un aspect:elle forme une interstratificationavecet une gainesur la chlorite
avecmuscoviteet halloysite,et desgrainsindividuelsrelativementgrossiers.Les imagesobtenues
d6form6e,uneintercroissance
par transmissionmontrentd'6paisamasde berthierineet de chlorite parallblesou I faible angled'incidence,et desfeuillets de
enintercroissance
sontaussiprdsents,
Desassemblages
mixtesdechlorite-berthierine
deberthierine.
chloriteayantuneterminaison
avec chlorite fenifbre et berthierine.Le p6le ferrifdre de la berthierine(sansMg) est signalden petits domainesdansdeux
6chantillons.Du point de vue composition,la berthierinede Kidd Creekressemblea celle d'autresendroits,et d la chlorite riche
de berthierinedansun gisementde
Noussignalonsici pour la premibrefois la pr6sence
en Fe de plusieurimilieux g€ologiques.
la plupartde la berthierinei Kidd Creeks'estform6ecomme
D'ap€s lesrelationstexturales,
sulfuresmassifsvolcanog6niques.
minfral primaireI unetempdraturerelativement6lev6e(*350"C) dansla zonetr veinulesdela paroi inf6rieure,pmbablementpar
observ6espar
remplacementd'un pr&urseur alumineuxtel la muscoviteou la chlorite.Toutefois,les texturesd'intercroissances
microscopie6lectroniqued balayageet partransmissionfont penserqu'unepartiedela berthierinea uneoriginepar remplacement
dela chlorite.la difficult6 quenousavons6prouv6ed identifier la berthierineparmdthodescourantes
syn-oupost-m6tamolphique
dL Ftrograptrie, de diffraction X et d'analysei la microsonde6lectroniquenousincite i penserque la plupart desexemplesde
chloriteriche enfer citdsdansla litldraturesur lesgitesde sulfuresmassifsmodemesou ancientsseraientplut6t de la berthierine.
(Traduit par la R6daction)
Mots-clds:berthierine,chlorite,gite volcanog6niquede sulfuresmassifs,microscopie6lectroniquepartransmission,donn6esd la
microsonde6lectronique,diffraction X, m6thodedespoudres,mine de Kidd Creek,Timmins, Ontario.
*hesent address:
BHP-UtahhtemationalInc.,200FairbrookDrive,Hemdon,Virginia22070,U.S.A.
1128
TI{E CANADIAN MINERALOGIST
II.ITRODUC"noN
Chlorite is one of the mostabundantmineralsin the
alterationzonesof volcanogenic
massivesulfidedeposits (e.9.,Franklinetal. l98l); it typicallyoccursin veins
with quartz,sulfides"andotherminerals,andasreplacementsof sedimentaryand volcanichost-rocks.In ancientmetamorphosed
deposits,chloritemaybe themost
commonlayer silicate,togetherwith variableamounts
of phengitic muscovite 1 paragonite;talc, stilpnomelane,andbiotite generallyarerare.In the pristine,
unmetamorphosedalteration zones of the Miocene
KurokodepositsofJapan,layer-silicate
assemblages
are
complexandincludechlorite,illite, smectite,localtalc,
celadonite,and vermiculite,andrarechrysotile(Iijima
1974,Shirozu1974,Utadaet al. 1974,Shlrozuet al.
1975). The alterationpipes of Cretaceousmassive
sulfide depositson Cyprus, also unmetamorphosed,
containillite, chlorite,smectite,andrectorite(Lydon&
Galley 1986,Richardset aL.1989).In this paper,we
describetheoccurrence
of berthierine.
anFe-Al sementine-type mineral, and berthierine--chlorite
mixtures
from the metamorphosed
Kidd Creekmassivesulfide
deposit,ofArcheanage,anddiscusstheimplicationsof
thesemixturesfor interpretingthe paragenesis
of Fe-Al
layer silicatesin modern and ancient volcanogenic
sulfideenvironments.
KC-813
KC-3231
24
IDEN'TFICATON
ANDOCCURRENCE
'20(CuKal
Geologicalsetting
pattems(CuKcrradiation)for
Fro. l. X-ray powder-diffraction
mineral separatesof layer silicates from the footwall
The large Kidd CreekCu-Zn-Pb-Ag deposit,north
stringer zone (north orebody) of the Kidd Creek mine.
of Timmins,Ontario,consistsof massivepyrite"chalcoPattemsfor samplesKC-813, KC-2505, and KC-3421
pyrite,sphalerite,pynhotite,andgalenalocally under-14 A (63'2e) and4.7 A (ts.s"zo)
lackthe diagnostic
lain by a chalcopyrite-richstringer zone(Walker et al.
peaksof truechlorite(chl) andconsistmainly (or wholly)
1975,Coad 1985).The ores are hostedby Archean
of berthierine(ber) mixed wilh muscovite(mus)1 quartz
volcanicrocksdatedby U-Pb zirconmethodsat2711
(qtz); small peaksat 7.V7.5"20 axeinstrumentalartifacts.
Ma (Nunes& Pyke 1981,Banie& Davis 1990)andare
Compare pattem^for sample KC-3231 (bottom) that
believed to have formed on or near the sea floor
containsonly 14A chlorite.All patternswereacquiredon
synchronously
with localvolcanismandsedimentation.
air-driedanduntreatedsamples.
Multiple events related to postore deformation are
evidencedby mine-scalefaultsand shearzones,strain
fabrics in hand specimenand thin section,and U-Pb
geochronological
data(Walkeret al. 1975,Bisbinet al. fied (by JFS) on the basis of optical featuresand results
1990,Banie & Davis 1990).Regionalmetamorphism, of electron-microprobe analyses. Identification of the
which only reachedlower greenschistgrade,took place Fe-rich chlorite is in error, however, as shown by X-ray
at approximately
2685Ma (Percival& Krogh 1983)and powder-diffraction Q(RD) patterns of mineral separates
was followed by a local metasomaticeventin the mine of layer silicates from Several samples^(Fig. 1). The
areaat about2576Ma(Maaset al. 1986).
Fe-rich silicate lacks the diagnostic 14 A reflection of
chlorite, and therefore is berthierine" an Fe-Al member
of the serpentine group (a.9., Brindley 1982, Bailey
1988). The Fe-rich chlorite ("daphnite") described by
Slack& Coad(1989)recentlydescribed
thetextures Slack & Coad ( I 989, Table 2, Fig. 12) consists largely
and chemistry of Mg- and Fe-rich chlorite from the or wholly of berthierine, including that in samples
footwall stringerzoneat Kidd Creekandsuggested
that KC-8 I 3, KC-2505, KC-3421 , and KC-3482. An XRD
thesetwo compositionaltypesof chloriteformedduring study of layer silicate separates from the other Kidd
separatehydrothermalevents.The chlorite was identi- Creek samples(e.g.,KC-3231, Fig. l) showsprominent
X-ray powderdffiaction
BERTHIERINEFROM TI{E KIDD CREEK DEPOSIT
TM
h](l
(@no)
001
020
110
1U
o2l
oo2
o22
20t
2XO
1. X-W
h&l
(h*)
010
100
mn-Drlmgld
AlEsb@
al-ca1c
otr1l
rc-au
d-calc
d-oalc
Kc-342r
d-calc
?.05
1.67
4. sg
4.24
7.!2
4.6S
1.O9
7.09
4.30
3.93
4,26
4,26
2.AO
2.64
2.44
2.71
2.44
101
002
110
1Xr
'
DAIA mR Bmlmlm
2.40
2.34
2.45
2.24
222
311
233
060
"mF cud
'PDF cdd
1953'
tL2
004
2.L4
1.494
1.769
1.700
2.L5
L.779
2.OA
1.943
7.175
L72A
2.24
2.13
2.OO
1.459
t.ala
300
?-315.
31-618.
k*hl6rire
&itbL€rlno
fr@ Atrahire,
m (arlndley
1951)
f,t@ @rby, w (Brlndl€y
& :ouell
14 A basalreflections;thus thesedo containchlorite.
X-ray dataacquiredfor samplesKC-813 andKC-3421
(Table 1) yield similar d-valuesto thosereportedfor
berthierine
fromAyrshire,Scotland(Brindley195I ) and
Corby,England(Brindley& Youell 1953).
(Nelson& Roy 1958),
Formerlycalledseptechlorite
and(incorrectly)chamositeand7 A chamosite,berthierine is an Fe-rich aluminous fioctahedral 7 A layer
silicate with a 1:I structuresimilar to that of lizardite
(Bailey 1988).Berthierineis difficult to recognizeby
normal XRD methodsbecausethe critical identifying
feature, the absenceof a 14 A basal reflection, is
commonly maskedby a peak due to admixedchlorite
(a.9.,Brindley 1982);conventionalXRD studiescan
documentthe presenceof berthierineonly in samples
that lack chlorite. Benhierine associatedwith a small
amountof Mg-Fe-rich chlorite can be misidentifiedas
Fe-rich chlorite, becauseFe-rich chlorite has a very
strongreflectionat about 7 A rehtive to its -14 A
reflection(Brindley1982).Mixed layeringof berthierine and chlorite may be suggestedby broader and
weaker,odd-ordered00/ reflections,comparedto those
of pure chlorite (Dean 1983,Ahn & Peacor1985).
Possible minor (<107o) interstratified Fe-Mg-rich
chlorite cannotbe detectedby XRD, however,because
of the weak nature of the odd-order reflections
(Reynolds1988).TheKidd Creeksamples
thatlacka 14
A basalreflection(Fig. 1) thusconsisteitherentirelyof
berthierine, or of berthierine and minor interlayered
chlorite not resolvableby )(RD methods.
Petrographyanl scanningelectronmicroscopy
Berthierinefromthe Kidd Creekmineformsanhedral
grains and subhedralcrystals associatedwith quartz,
muscovite,chlorite,pyrite, sphalerite,chalcopyrite,and
local tourmaline, cassiterite,and halloysite. Typical
tt29
grain-sizes
are 10-50!rm, althoughsomelargecrystals
thatappearprismaticin crosssection(normalto {001})
in samplesKC-3421 and KC-3482 are as much as
100-200 pm long. Bertlierine grains commonlyare
pleochroic from colorlessto pale green or from pale
greento mediumgreen,and most havehigherbirefringencethan chlorite-groupminerals(e.g., Hey 1954,
Alber-1962),producingyellow to orange(rarelypurple)
first-orderinterferencecolors(n!-na= 0.018).However,
the berthierine grains in several sampleshave lower
birefringenceand superficially resemblechlorite, thus
leadingto misidentificationbasedon petrographiccriteria alone.
Berthierinegrainsin sampleKC-3421 are locally
associatedwith a white clay mineral. X-ray data obcamera(H.T. Evans,Jr.,
tainedwith a Debye-Scherrer
USGS,pers.cornmun.,1991)indicatethat this clay is
traltoysiie-7A, with possiblya traceof halloysite-ldA.
beam,
usinga defocused
analyses,
Electron-microprobe
0.14.7 VoFeO,and
show45-467aSiO2,36-37VoAl2O3,
anhydrousoxide totals of 83-84Vo,consistentwith the
presenceof halloysite. The halloysite forms irregular
zones(Fig. 2A) commonly0.5-1.0 mm in diameter
within massivesphalerite,and intergrowthswith muscovite, quartz, and sparsefluorite; berthierineoccurs
alongthe marginsof somehalloysitezones(Fig. 2B).
One large zoneof halloysitefills what appearsto be a
former aggregateof euhedralflakes of muscovite(or
anotherphyllosilicate)in sphalerite(not shown),suggestinga paragenesis
ofearly muscovite(?) followedby
by
replacement
a laterstageinvolvingpseudomorphous
halloysite.Inclusionsof muscovitein some of the
halloysite zones display embayed,corrodededges,
whereasothershave smoothboundaries;similar relations exist betweensphaleriteand layer silicates.The
halloysite is interpretedas a late hydrothermalphase,
andnot a productof supergenealterationor weatltering,
basedon the lack of fracturesin this sampleand the
absenceof any secondarymineralsdiagnosticof oxidation or weatlering(e.9.,hematite,covellite,goethite).
Halloysite has beenidentified in someof the Mocene
Kurokodepositsof Japan(e.8.,Nurukawa)andrecently
in the modernKuroko-typeJadedepositactively forming in the OkinawaTrough (Marumo 1991).Stanton
(1983)reportedpossiblehalloysitefrom the Archean
Gecomassivesulfide depositin Ontario,but without
supportingXRD evidence.The occurrencein the Kidd
Creek deposit appea$ to be the first example of
hypogenehalloysitedocumentedin hecambrianrocks.
Berthierine commonly displays complex intergrowths with both muscovite and chlorite. Euhedral
berthierinebladesenclosedwithin sphaleritein sample
KC-3421 locally show embayedcontactswith muscovite (Fig. 2C) that suggestreplacementof muscovite(or
a pre-existingphyllosilicate)by berthierine.However,
other areas of this sample and areas within sample
KC-813 (Fig. 2D) have "equilibrium" texturesthat
imply contemporaneousformation of muscovite and
Ftc. 2. SEM back-scattered
electronimagesof samplesfrom the footwall stringerzone.A. Intergrowthof halloysite(dark grey)
with muscovite(mediumgrey) andberthierine(palegrey) alongright edge,sunoundedby sphalerite(white); black areasare
openpits(sampleKC-3421).B. Detailof A showingeuhedral
berthierine(palegrey)in contactwith muscovite(mediumgrey)
and halloysite(dark ercy) and associated
with sphaleritein white (sampleKC-3421). C. Massivesphalerite(palegrey)
enclosingprismaticgrainsof berthierine(mediumgrey) apparentlyreplacingmuscovite(dark grey); small white grainsare
cassiterite(sampleKC-3421). D. Grainsof berthierine(palegrey) intergrownwith and sunoundedby muscovite(medium
grey),andassociatedwith quartz(darkgrey);sphaleriteis white (sampleKC-813). E. Elongatecompositegrain ofberthierine
(palegrey) andFe-Mg chlorite (mediumgrey); muscoviteis black andsurroundingchalcopyriteis white (sampleKC-2505).
F. Detail of E showingalternatinglamellaeof finely intergrownberthierine(palegrey) and Fe-Mg chlorite (mediumgrey),
andrims of berthierineon chlorite; black areasarecracksand voids betweenminerallamellae(sampleKC-2505); seeTable
2 for resultsofelectronmicroprobeanalyses
ofthe chlorite(no.2505F1)andbenhierine(no.2505F2)in this grain.
BERTHIERINE FROM TIIE KIDD CREEK DEPOSIT
1131
berthierine (or its precursor). Berthierine in sample large crystalsof Fe-Mg-rich chlorite, (2) single layers
KC-3421 exhibits embayedand corrodededgesand or very thin packets of layers interstratified with
and
seemsto be partially replacedby the associatedhal- berthierine(1e.,mixed-layerchlorite-berthierine),
(3) crystals of relatively Fe-rich chlorite (designated
loysite(Fig.2B).
Figure2E showsa compositegrain ofberthierineand hereafteras Fe-chlorite)that are intimately intergrown
In additionto the
chloritepartlysurrounded
by muscovitein chalcopyrite- with mixed-layerchlorite-berthierine.
rich sampleKC-2505 from the coreof the stringerzone mixed layering, discrete,thick packes of berthierine
(seeSlack& Coad 1989,Fig.2). This grain is clearly intergrownwith chlorite also are present,analogousto
deformed, consistentwith the presencein the same theberthierinelamellaeshownin Figure2F.
sampleof microscopicchevronfolds definedby deFigure3 showsfypicalrelationsbetweenberthierine
formedmuscovite,chlorite,and sulfides.Most of the and the three different types of chlorite. Each layer
bordersof the compositegrain (Fig. 2E) containa thin silicate forms relatively thick, well-defined,discrete
with berthierine
(<5 pm) rim of nearlyend-member(Mg-free) berthier- packetsthatareparallelor subparallel,
ine, whereasthe interior has very fine lamellae of and mixed-layerchlorite-berthierineoccuring preferberthierine<1 pm in diameter(Fig. 2D. The deforma- entially at the boundariesof chlorite crystals.The
tion may havecausedbendingand gliding of chlorite individualpacketsof chloriteseemsimilarto thoseof
that
layers,resultingin separation
ofthelayersandformation phyllosilicatesaffectedby metamorphicprocesses
voids.Packetsofberthierine locally approachan equilibriumstate,with an absence
ofthe elongatelens-shaped
features(e.9.,mixedlayering)that
orientedparallelto thevoidsalsohavea similarlens-like ofthe heterogeneous
shape,andseveralofthe voidscontainaberthierinerim, characterizetexturesformed at very low temperatures
althoughsomeberthierinelamellaehavedifferentorien- (e.g.,Ahn & Peacor1985).However,packetsof Fewith voids.Oneinterpre- chlorite,Fe-Mg-rich chlorite,and chlorite in mixedtationsandarenot associaied
to
occurimmediatelyadjacent
tation ofthesefeaturesis thatthechloriteandberthierine layerberthierine-chlorite
representprimary hydrothermalprecipitatesthat were one another,a featurethat cleaily indicatesnonequilideformedtogether,producingthe parageneticallylate, brium conditions.
Severaltypesof deformationfeaturesareobserved.
lens-shaped
voids.Alternatively"berthierinemay have
voidsor by the In the middle-right part of Figure 3 is a pale grey arca
formedby filling of deformation-related
replacementof previouslydeformedchlorite.Similar with an arrowheadshapethat separatesFe-Mg-rich
lens-shaped
replacements
of deformedphyllosilicates chloritethat presumablywas oncecontinuous,as the
areaare
havebeenwidelyreportedin low-grademetamorphosed outlineson bothsidesof thearrowhead-shaped
material
to
identify
the
We
are
unable
identical.
nearly
(Craig
et al. I 982,van
andhydrothermallyalteredrocks
area,but it appearsto be
1984,Gregg1986,Ahn within this anowhead-shaped
der Pluijm & Kaars-Sijpesteijn
phase
Al, Si, K, Mg, Fe,S,
containing
a
noncrystalline
& Peacor1987.Bons1988).
by EDSspectra.Thepacketof
Cu, andCl, assuggested
Fe-Me chlorite that is dissectedby the arrowheadTransmission electron microscopy
Part of a thin section of sample KC-2505 was
preparedfor transmissionelectronmicroscopy(TEM)
following opticaland SEM studies.A 3-mm-diameter
detachedfrom
areaadhering
to analuminumwasherwas
the thin sectionand a Cu grid backingwas attachedto
onesideto preventthepossiblelossofthin edgesdueto
ratesof
differentialthinning andexpansion-contraction
layer silicatesand sulfidesduring Ar ion-beammilling.
A PhilipsCMl2 scanningtransmission
electronmicroscoper coupled with a low-angle Kevex Quantum
detector for EDS analysis was used for the TEM
observationsat the University of Michigan. The 00/
reflectionsup to the third order(chlorite) were selected
lafticefringeimages.
to produceone-dimensional
Chloritein sampleKC-2505 wasobservedto consist
ofthree principaltexturaltypes,including(l) discrete,
lAny use of trade, product, or firm namesis for descriptive
purposesonly and does not imply endonementby the U.S.
Govemment.
electronmicroscopicimageof sample
Flc. 3. Transmission
KC-2505 showingintergrowthsof berthierinewith Fe-Mg
chlorite(C), Fe-chlorite(C'), andmixed-layerchlorite-berareain the
ttrierine(C/B). The pale grey anowhead-shaped
phase(seetext).Thewhite
middle-rightis a noncrystalline
arrow indicatesa kinked areain chlorite.
n32
T}IE CANADIAN MINERALOGIST
FIc. 4. Selected-areaelectron-diffractionpafternsof areasin
Figure 3 showing 001 reflections of A) berrhierine,B)
Fe-Mg chlorite, C) mixed-layerchlorite-berthierine,and
D) chlorite + berthierine.The beamstopperwasusedfor A
andC.
shapedareahas a prominent kink (indicatedby the white
arrow). Thicknesses of the packets next to that of the
kinked packet vary along tire packet, consistent with
gliding alongboundarieswith a componentnormalto
the image.Variationsin contrastoccur within someof
the chlorite and berthierinepackets,apparentlyreflecting strain.The straincontrastat the crystalboundaryin
the middle-leftpart of the imagesuggeststhat thereis a
lattice misfit, in agreementwith an origin dueto gtding
along partially coherentinterfaces,as is normally the
casein gliding facilitatedby dislocations.Suchdeformation featureshave not beenobservedin berthierine
and mixed-layer chlorite-berthierine regions, which
implies that someof the berthierineis probablysyn- or
post-deformationin origin, replacingdeformedchlorite
or voids createdduring deformation.
Selected-areaelecron-diffraction (SAED) patterns
were obtained from different areasof Figure 3. The
SAED natterns are consistentwith the presenceof
berthierine(7 A periodicity,Fig. 4a), chlbrite(t+ A
periodicity,Fig. 4B), andmixed-layerchlorite-berthierine (relativelyweak,diffuseodd-orderandstrong,sharp
even-order00/ reflectionswhered(001) - 14 A, Fig.
4C). The continuous^
streak along c'in Figure 4C
suggeststhat the 14 A (chlorite) and 7 A (berthierine)
layers are randomly interstratified in the mixed-layer
areas.Like the interpretiveproblemsof XRD patterns
Ftc. 5. lattice-fringe image of intergrownberthierine(B), Fe-Mg chlorite (C), and mixedJayerchlorite-benhierine(C/B) in
sampleKC-2505.tayen showing-7 A (narrowfringes)and-t4 A lwiae fringes)periodicitiesareberthierineandchlorite,
respectively.layer terminationsandcomplexmixed layeringbetweenchloriteandberthierinearepresentin the middleright.
BERTHIERINEFROM THE KIDD CREEK DEPOSIT
discussedabove, it is difficult to differentiate 00/
reflections of discrete berthierine r discrete chlorite
(Frg.4D)from thoseof only discretechlorite(Frg.4B).
Packets of berthierine and mixed-layer chloriteberthierinearelocally parallelor subparallelto adjace4t
packetsof Fe-Mg chlorite (Fig. 5). Individual 14 A
layers are presentwithin the berthierine packet, and
dilcontinuiiiesbetween14A and7A hyers arepresent
in themixed-layerarea.Suchdiscontinuitiesmaybe due
to variationin the inclinationofc" alongthe layersor to
variations in crystal thickness(Amouric et al. 1988,
Jahren& Aagaard1989).However,in this casethey
appearto representtrue interfacesbecauseimagesthat
wereobtainedat differentconditionsoffocus all display
the samefeatures.
Figure 6 showsalternatingthick packetsof berthierine andFe-Mg chlorite layersthat areparallelor related
by low-angleboundaries.Suchtexturesareanalogousto
thoseobservedin many occunencesof phyllosilicate
intergrowths that formed during prograde metamorphism(e.9.,Franceschelli
et a\.1986,Frey 1987,Jiang
et al. 1990).Tltevariationin contrastalongthelayersin
the upper left reflects strain, presumablydue to shear
I 133
stress(Bons et al. 1990).The berthierineand chlorite
packes in the lower part of the image seem to be
unaffected.The slight variationsin contraston the right
are principally due to decreasingthickness of the
specimentoward the thin edges.Mixed layering and
interstratificationof packetsof nvo phyllosilicatephases
arecommonin replacementreactionsof onephyllosilicateby theother(e.g- Banfield& Eggleton1988,Jiang
& Peacorl99l), althoughthey alsomay occurwithout
phasetransitions.
An electron-diffractionpattern of berthierine (Fig.
7A) showsa highly disorderedsequenceof stacking,as
suggested
by the strongstreaksin the non-001reflection
row^swith k * 3n.The presenceof very weakstreaksand
14A reflectionssuggests
thatthereis aminorcomponent
of chlorite interstratified with the berthierine.Disorof stackingare commonin phyllosili
deredsequences
catesthat formed during diagenesisor very low-grade
metamorphism(Kisch 1983, 1987).Such disordered
sequencestransformto orderedsequencesduring prograde metamorphismbefore conditions of the lower
greenschistfacies are attained.Coexisting muscovite,
having a nearly end-membercomposition,with only
Ftc. 6. tattice-fringe imageof sampleKC-2505 showingalternatingpacketsof berthierine(B) and Fe-Mg chlorite (C) that are
parallelor relatedby low-angleboundaries.
1134
THE CANADIAN
Flc. 7. Elecffon-diffraction patterns of berthierine in sample
KC-2505 showing continuous streaking along c* in 0ll or
hhl rows, suggestinga highly disorderedstacking sequence
(A), and the I10l or [T0l zone of muscovite with 20 A
periodicity in hhl or hhl rows, implying a twoJayer
polytype (B).
minor Fe and Mg, invariably occursas a twolayer
polyfype,givinga 20 A periodicityin non-00/reflection
rows with & + 3n of SAED pattems(Fig.7B) andwith
differentcontrastin alternate00I fringes.Themuscovite
forms eitherdiscrete,largepacketsof layers,or small
packetsof layersenclosedwithin otherphases;mixed
layeringbetweenmuscoviteand other phasesis not
observed.
All of thesefeaturesin muscoviteareconsistent with equilibrationof dioctahedralphyllosilicates
undergreenschist-facies
conditions.
MTNERAL
Cner4rslRy
Slack & Coad (1989) reportedon the results of
detailedelectron-microprobeanalysesof Mg- and Ferich chloritefrom Kidd Creek,thelatternow recognized
as berthierine.Selectedcompositionsfrom that studv.
MINERALOGIST
togetherwith more recentmicroprobedata (using the
samemethodsand standards),arepresentedinTable 2,
The berthierinecontainsnearly equalamountsof SiOt
havelittle or no Na Ca or
andA12O3,
andmostsamples
K. Many grains contain<l wtVoMgO, and several
compositions
from samplesKC-813 andKC-3482lack
detectableMgO, thus documentingthe occurrenceof
(e.9.,no.813F,Table2).Grains
end-memberberthierine
enclosedin sphaleritein sampleKC-342lhave asmuch
as 2 wt%oZnO that indicate a small componentof
fraipontite,the zinc analogof berthierine(Fransolet&
Bourguignon1975).The minoramountsof Na, Ca and
Kfoundlocallyin berthierinefrom
samples
KC-813and
KC:3421 suggestthe presenceof finely interlayered
smectiteor perhapsinterlayeredmicassuchas paragonite, muscovite,or margarite.Normalizationson the
basisof an idealchloriteanionformulaQ0 O + 16OH)
IVAIin all samples,
revealthatvlAl significantlyexceeds
in contrast with ideal end-member berthierine
for whichvrAl - IvAl. The
IGeaAl+XSi+A14)o20(oH)r6l
vlAl
in the Kidd Creeksamplesmay berelatedto
excess
thepresenceofintergrown Si-richphasessuchasquartz,
pyrophyllite,or talc, or to interlayeringwith a di,trioctahedralchloritesuchas sudoite(e.9.,Bailey & Lister
1989, Shau et al. 1990), with both the trioctahedral
chlorite and berthierine.Sudoitehasbeenidentified in
the alterationzonesof severalof the unmetamorphosed
KurokodepositsofJapan(Tsukahara1964,Hayashi&
Geco massive
Oinuma 1964) and the metamorphosed
sulfide deposit, Ontario (Stanton 1984). It is also
possiblethat the excessvlAl reflectsvacanciesin the
octahedralsites(Foster1962),which are commonin
berthierine(Brindley 1982) and some chlorite (e.9.,
Curtiselal. 198t.
QualitativeEDS andanalyticalelectronmicroscopy
(AEM) analyseshave been acquiredon sampleKC2505. The EDS analysessuggestthat most of the
berthierine crystals a.remore Fe-rich than coexisting
chlorite,althoughvery Fe-richchlorite(i.e,daphnite)is
presentlocally(Fig.3).Ahn & Peacor( I 985)andJahren
havedemonstrated
thatberthierineis
& Aagaard(.1989)
generallymoreFe-richthanchlorite,but thatoverlapsin
Fe-Mg contentsoccur.The AEM analyses,caried out
on materialsdefined as pure by TEM observation,are
consistentwitl this relation.Extremecaution,therefore.
must be usedin the identificationof Fe-richchlorite,
especiallythe aluminousvarieties.
Figure 8 shows the averagecompositionsof Kidd
Creekberthierineand chlorite comparedto the compositional fields for berthierine and chlorite from other
localities.This diagramillustratesthe overall chemical
similarity between berthierine and chlorite, and the
difficulty ofdistinguishingthemon thebasisofelectronmicroprobedataalone.Compositions
of theKidd Creek
berthierine and chlorite all plot within the field of
berthierinereportedby Brindley(1982),Iijima& Matsumoto (1982), Bhattacharyya(1983), and Velde
(1989), and also within the compositionalfields of
I 135
BERTI{IERINE FROM THE KIDD CREEK DEPOSIT
TAALE2. REPRESEITATIVE
CSPOGITIOI{S
OF BERTITIERIIIE
ANDCIIONIIE
8llp
813E
81lr
slo2 ftZ
At2gt
rlo2
F€
I'lrO
ri@
Zm
c€o
ra20
(2q
lotrl
22.U
A.0l
0.07
42.m
0.
1,'t3
n.€!
0.02
0.0E
0.u
89.35
u.62
?3.05
0.05
41.37
0.51
89.15
21.99
u.21
0.0t
42.t9
0.16
0.@
n.o.
0.02
0.05
0.t18
47.54
st
Attv
Atvr
rr
r€
lln
Is
Zn
Ca
I!
r
lotal
5.0t4
2.96
t.27
0.012
8.155
0.Ct0
0.386
0.000
0.004
0.037
0.011
19.882
5.150
2.450
3.136
0.0@
7.876
0.(Xl
0.tJ4
o.0lt0
0.021
0.1@
0.149
19,4n
0.403
0.959
0.042
0.98
n.e.
0.t0
2505F1
405F2
a.a
23.15
33.31
0.tl
7.1t
n.o.
0.03
0.oa
0.19
87.'t0
St@turut
oct Va@y 0..|7()
rol(Fdils) 0.955
lg/F6
0.U7
5.153
2.97
3.M
0.006
8.424
0.0:t!
0.(n0
0.000
0.004
0.025
u.31
8.51
0.04
41.07
0.13
1.31
0.04
0.04
0.06
84.5t
fo@lao
o
g21B
wA
lilRAfl
rURST
cmBv
USSR
21.96
?531
0.01
41.94
0,27
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0.00
0.01
0.02
89.7?
2,.8
a.A
0.03
x,77
0.14
5, t9
n.a.
0.01
0.02
0.00
88.t7
4..47
4.24
n.o.
40.15
n...
1.77
n.a.
0.lt
0.00
o.ot
E8.12
21.26
4,61
n.d.
39.19
n.d.
2.92
?2.41
4,12
n.a.
39.66
n.a.
2.72
n.6.
n.a.
n.o.
n.a,
EE.t7
?2.40
23.9
n.a.
39,63
1.9,
2.01
0,66
n.d.
n.d.
0.n
90.02
4.qr4
3.@6
5.M5
2. 5
'.241
0.000
7,465
0.t22
0.68
o.tlo
0.000
o.qx)
0.088
t9.E9E
n.a.
n.d.
n.d.
n.d.
E6.9E
tho basls of 28 on€s
19.800
5.14
2,An
l. t9:t
o.ott8
6.196
0.027
2.36:t
0.000
0.00E
0.03t
0.052
t9.881)
5.087
2.913
!.406
0.@7
7.&
0.05
0.446
0.000
0.011
0.017
0.017
19.763
5,@
3.000
3.50
0.(X)t
7.9@
0,052
0.418
0.172
0,000
0.006
0.005
19.W
5.066
2.914
3.225
0.006
6.85?
0.0?i
1.724
0.000
0.003
0.0@
0.001
19.95
t.l
2.82
t.472
0.005
7,632
0.000
0.600
0.000
0.022
0.(X'0
0.@0
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7.t 9
0.(X|0
t.(xB
0.tx)o
0.000
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9.An
,.162
2.898
1.ll1
o.qD
7.506
0.0&t
0.917
o.ol!0
0.000
0.000
0.000
19.754
0.41
1.000
o.o{d
0.213
0.7u
0.31
0.42
0.950
0.057
0.127
0.9&
0.052
0.167
0.7,D
0.42
0.341
0,927
0.079
0.113
0.88
0.1l]
0.246
0.891
0.1?2,
t.au
0.(Xx,
0.185
0.917
0.0911
Not4r Total lM 6 f60t n.a. s mt @lyred or mt r€poft€di n.d. s tut d6t*ted.
E130! berthlorlm
@6l6tod
pyrlto. Elmf aphal€rlte and tl8rtz, and tre6
rlth td@(|re.
ol aerlclte (tr@ Stek & Cosd t989, lobt6 2); 813E.
borthlerlre a$el6ted
rlth qertr.
sphalorlto. f'yrlte, td@tire,
ard olrcr erlcltei
81!f: berthlerlre dslat€d
rlth pyrlt6, qetta, sphal6rlt6,
and Flrcr a€rlcltai 2505il! chtorlto Intorgr@ rlth borthlorlG
ard s@lated
rlth so.lclto, chatcoFyrlto, dd olmr qe|tz (@ Flg. zr)i 2505F2:
borthlorlre
lnto.tr@
rlth chtorlte €fd arsl6ted
rlth &rlclt6.
chalcopyrlte. oid olrcr qwm? (se flg. 2r)t 342'lB3 berthlorlE
delated
dth
@llclto,
sphslerlto, std almr cholcoFyrlte aid @sltorlto
(@ Flg, 2r)t 348243 bo.thloflre @slated
qd.t.,
pyrlto, sFhglo.lto,
rlth t@@tlm.
dld olmt aetlclta (ff@ Strcl g Co€d 1989, table 2)t ttRff{! K-typo berthlorlm of fiji@ & I,tat@to
(19Aa, t€bt€ 4) ln Trleslc
flrslay
b.ds ff@
lll.@tau
arc€, Japoi xuls(! berthl€rlc
ln baulte d€p@lt8 fr@ fq.sk, ussR (yoFhoE et s!. 19?6r; conBtt b€rthl€rlre ln Jqraedtc lr@t@
ff@
co.by, Iorth!ryt@hlro,
ua (lrlidtq/
& Y@tt 1953)t ussR: bofthlerlre ! chlorlto ln Ag-pb-zn qertz wln, ussR (R6lrcw ot at. 1987).
',ii@))
R2
Ftc. 8. Cationplot of averagemicroprobecompositionsof
chlorite(opencircles)and berthierine(solid triangles)at
Kidd Creek compared to the compositional fields of
chloritescompiledby Foster(1962)andVelde(1973)and
thefield of ber*rierines(hatchured)
from Brindley(1982),
(1983),and
Iijima & Marsumoro^(1982),
Bhattacharyya
Velde( I989).R' = Fez*+ Me + Mn + Zn.
chloritecompiledby Foster(1962)andVelde (1973).
However,theberthierineandchloritefrom Kidd Creek
differ slightly in relativeproportionsof Al andR2+(Fe2+
+ Mg + Mn + Zn) cations.The Kidd Creekberthierine
and thosesampleslistedin Table2 from Corby(England),Hiramatsu(Japan),andthe USSR(not plotted),
all are more aluminousthan the Kidd Creek chlorite.
Note that in deformedsampleKC-2505 (Fig. 2D, the
microprobedatareportedin Table 2 for the berthierine
lamellae (2505F2) also indicate a more aluminous
composition
thanthatofthe coexistingchlorite(2505Fl). With the exceptionof sample2505,this probablyis
unrelated to the extent of octahedral-sitevacancies"
which spana similar rangein the berthierine(Table2)
andchlorite(Slack& Coad1989,Table2).
DIscussIoN
Berthierine is a common mineral in many Fe-rich
sedimentaryrocks,especiallyironstonesandiron formations (e.g., French 1973, Bhattacharyya1983, Van
Houten & Purucker 1984, Maynard 1986). Recent
mineralogicalstudiesalsohaveidentifiedberthierinein
tt36
soilsandbauxites(Kodama& Foscolos1981,Nikitina
I 985),unmetamorphosed
coalmeasures
of Japan(Iijima
& Matsumoto1982),diageneticallyalteredclasticsedi
mentsof the Gulf Coast(Ahn & Peacor1985),clastic
reservoirsofoffshoreNorway(Jahren& Aagaard1989),
conglomerates
from England(Taylor 1990),and some
low-grade pelitic schists from Yenezuelaand Spain
(Amouricet al. 1988,Bons& Schryvers1989).Documented occurrencesof berthierine in hydrothermal
settingsarelessextensive,andmainly involvesulfidebearingveinssuchasin France(Cailldre& HdninI 956),
(Novaket al. 1959),England(Smith&
Czechoslovakia
Hardy 1981),theformerSovietUnion (Rusinovaer a/.
1987),andNiger(Perezetal. I 990);berthierinealsohas
been reported recently from hydrothermally altered
shalesin the SaltonSeageothermalfield of Califomia
(Yau et al. 1988,Walker & Thompson1990).The
berthierineidentified from the Kidd Creekmine in this
study representsthe first known occurrencein submarine massivesulfideenvironments.
Formntion of benhierine
Possiblemechanisms
for the formationof the Kidd
Creekberthierineinvolvehydrothermal,metamorphic,
and postmetamorphicprocesses.
Interpretationsof premetamorphichydrothermal growth are basedon the
presenceof largeprismaticcrystalsin pristinesample
KC-j421 (Fig. 2C), and on equilibriumtexturesobservedin relatively undeformedsamplessuch as KC813 (Fig. 2D) that are similar to those observedin
modernsulfidedepositsfrom the seafloor (e.g., Alt et
al. 1987,Alt & Jiang 1991),where mineral grains
commonlyareeuhedralandform straightcontactswith
layersilicates,presumablyas a resultof crystallization
in a stress-free
environment.
Experimentalstudiesalso are consistentwith a hydrothermalorigin for someof the Kidd Creekberthierine. All of the synthesiswork doneto dateon chlorire
hasmadeZ A, not 14 A phases,as initial run products
(a.9.,Nelson& Roy 1958,Turnock1960).In a detailed
studyof the stabilityof iron-richchlorite,Jameset al.
(1976)synthesized,T
A Fe-richsilicateat 300'C and2
kbar P(H2O),whereascrystallizarionof 14 A Fe-rich
chlorite requiredlonger run times (six weeks)at temperatures
in excessof 525oC.Morerecently,Nikol'skaia
et al. (1985) formed berthierineby reactingkaolinite
with FeCl3at 400"C,andYau et al. (1987)synthesized
berthierinet illite at 300"C from an interlayeredillitesmectite precursor. These experiments show that
berthierine,althoughprobablymetastable,may form in
hydrothermalsystemsat relativelyhigh temperatures
of
30H00"C. Theinfenedhydrothermalberthierinefrom
Kidd Creek is believed to have formed under similar
temperature
conditions(a.9.,Slack& Coad1989).The
formation of the hydrothermal berthierine probably
occurredby replacementof a pre-exisitingaluminous
phase,ratherthanby direct precipitationfrom solution,
basedon the low solubilityof Al in mosthydrothermal
solutionsandthe very low AVFeratiosof end-member
(Mg-free)compositions
for fluids sampledat
calculated
modernsubmarinevents(Bowers& Taylor 1985,Von
Damm & Bischoff 1987). We cannot exclude the
possibility, however,that some of the Kidd Creek
berthierineprecipitateddirectly from hydrothermalsolutions, like the illite-smectite recently discoveredby
Alt & Jiang(1991)from massivesulfidedepositson the
seafloor.
Texturalrelationsandexperimentalwork (Yaluet al.
1987) suggestthat the initial formation of berthierine
may have involved gowth from an illite-smectite
precursor(e.g.,Fig.2C),or possiblya kaoliniteprecursor (Bhattacharyya
1983,Nikol'skaiaet al. 1985)that
reacted with Fe-rich hydrothermal fluids. The latter
interpretationis consideredlesslikely, on the basisof
the observedparageneticrelations amongberthierine,
muscovite,and halloysitein the Kidd Creeksamples.
Smectitealsois not a favoredprecursorbecauseof the
lack of significantNa or Ca recordedin the microprobe
datafor the berthierine(Table 2), althoughNa and Ca
could have been leached from smectite during hydrothermalalterationto berthierine.Most, if not all, of
the premetamorphicberthierineat Kidd Creek is believed to haveformedby the hydrothermalreplacement
of pre-existingmuscoviteor chloriteat temperatures
of
approximately350'C (Slack & Coad 1989), which
producedthe observedembaymenttexturesand euhedral pseudomorphs.
Evidencein supportof a syn- or postmetamorphic
origin for someof the berthierinecomesmainly from
texturalfeaturesdocumented
by SEMandTEM studies.
Theseinclude the lamellar intergrowthsobservedin
deformedsampleKC-2505 (Frg. 2D, andthe relations
betweendeformedchlorite andundeformedberthierine
illustratedin thelatticefringe imagesof thesamesample
(Figs. 3, 5). The latter texturesare common in intergrown stacksof phyllosilicatesthat formed as stable
coexistingassemblages
in low- to medium-grade,greenrocks(e.9.,Franceschelli
et al. 1986,Frey
schist-facies
1987, Jianget al. 1990)andin phyllosilicateaggregates
that formed throughpartial replacementof a precursor
phase(e.9.,Jiang& Peacor1991).We cannotdiscriminatebetweensyn- andpostmetamorphicgrowth of this
berthierine,but regardlessof the timing, it seemslikely
thatit replacedpre-existingchlorite,eitherofhydrothermal or metamorphicorigin. The Fe necessaryfor the
formation of this metamorphicberthierine may have
comefromtherimsof tourmalinecrystalsin thefootwall
stringerzonethat were leachedof substantialamounts
of Fe, Ti, and Ca (Slack& Coad 1989,Figs.5, ll),
possiblyduringthelatemetasomatic
eventdocumented
in the mineareaby Maaset al. ( 1986).The formationof
theFe-chloritemayhaveinvolvedalterationofberthierine in thelater stagesof multiple metamorphiceventsin
theregion,identifiedby Brisbinet al. (1990)andBarrie
& Davis(1990).
BERTHIERINEFROM THE KIDD CREEK DEPOSIT
Preservation of hydrothermal benhierine
Berthierineis generallyco-nsidered
to be a metastable
phase that inverts to 14 A Fe-rich chlorite during
diagenesisand metamolphism.In clastic sediments,
berthierine is preferentially found at shallow depths
relative to Fe-rich chlorite, which commonlyis coarser
grained and parageneticallylater than the associated
berthierine(Frey 1970,1978,Lee & Peacor1983,Ahn
& Peacor1985).Velde et al. (1914)suggested
that in
arenitesand calcarenites,7 A berthierineundergoesa
polymorphictransformationto 14A chloriteat temperatures of 25-100'C. Similar relationsare observedin
hydrothermallyalteredsedimentsfrom the Salton Sea
geothermalfield, whereberthierineis found in shallow,
low-temperaturesettingsrelative to the deeper,higher
temperatureoccurrencesof Fe-rich chlorite (Yau et al.
1988,Walker& Thompson1990).
The presence
in sampleKC-3421of large(100-200
pm) prismatic crystals of berthierine together with
halloysite(Figs.2A, B), a likely metastable
precursorto
kaolinite (Churchman& Can 1975. Steefel& Van
CappellenI 990),suggests
thatthisKidd Creekberthierine is a primary hydrothermal phase and that the
halloysite formed by late hydrothermalprocesses,as
discussedabove.The preservationof berthierineand
halloysite in this samplemay reflect the armoring of
layer silicatesby massivesulfide, thus preventing
interaction with metamorphicfluids that would have
convertedthesesilicatesto Fe-richchloriteandkaolinite
(or illite), respectively.This interpretationis supported
by the fact that samplescontainingtourmalinewith a
(Slack& Coad 1989)have
metamorphicreacticifr-rim
chlorite but little or no berthierine.whereastourmaline
crystalsin othersamplesthat containabundantberthierine (e.9., KC-813) show little or no evidencefor
interactionwith a metamorphic
fluid (i.e.,absence
of a
reactionrim).
Evolution of the Kitd Creekstringer zone
Many electron-microprobestudieshave shown that
massivesulfide depositsare dominatedby Mg-rich
chlorite, but that some depositscontain local Fe-rich
chlorite [Fe/(Fe+Mg)> 0.8], assummarizedby Urabeel
al. (1983)andSlack& Coad(1989).Theinnercoresof
footwall zonesof alterationin the depositsmay show
preferential concentrationof either Mg- or Fe-rich
chlorite,relativeto peripheralzones(e.9.,Franklinet al.
1981,Urabeet al.1983,Gustin1990).Suchcompositional variations in chlorite chemistry are generally
attributed to precipitation from solutions containing
variable proportionsof Mg-rich seawaterand Fe-rich
hydrothermalfluid (Robets & Reardon l978,Ziercnberg et al. 1988).The compositionalvariationsof the
Kidd Creekchlorite were interpretedby Slack & Coad
(1989)in a similarmanner:the Fe-Mg chloriteformed
first and was overprintedor replacedby Fe-rich'thlo-
tt37
ite" (i.e., berthierine)wherealterationand mineralization asssociated
with anearlierhydrothermaleventwere
believedtohavesealedoffthe footwall zoneof alteration
from infiltration by Mg-rich seawater.The recognition
of berthierinein the deposit,however,requires a reevaluationof this interpretation.
Slack& Coad(1989)proposedthe existenceof two
hydrothermaleventsin theKidd Creekdeposit,in which
early formation of Fe-Mg chlorite and tourmalinewas
followed by a secondeventthat chemicallyoverprinted
the chlorite to form daphnite(1e.,berthierine),whereas
the compositionsof the chemically more resistant
tourmalineremainedunaffected.However.theSEMand
TEM observationsof complex berthierine--chloriteintergrowthssuggestinsteadthat mostof the7 A berthierineformedfirstfrom anFe-rich"end-memberhvdrothermal fluid andth atthe 74 A Fe-Mg chlorite formedlater
from a seawater-dominated
fluid; quartz, tourmaline,
and sulfides apparentlywere precipitatedduring both
eventsof fluid circulation. Thesemineralizing events
need not have been separatedby a significant time
interval,howevel and could have been part of one
long-lived seafloorhydrothermalsystem.The apparent
disequilibriumbetweenthe Fe/(Fe+Mg)ratios of chloby Slack& Coad
rites and tourmalinerims suggested
(1989)thereforemay not indicatethe presenceof two
unrelatedhydrothermalfluids in the footwall stringer
zone.but insteadcouldreflecttheoccurrenceofberthierine (ratherthan daphnite)in sampleswith Fe/(Fe+Mg)
ratiosthat fall offthe equilibriumKp curvesfor chlorite
andtourmaline(seeSlack& Coad1989,Fig. 13).
Im.plicationsfor modernand ancientvolcanogenic
mnssivesulfidedeposits
The recognitionof berthierinein the ArcheanKidd
Creek massivesulfide deposit has implicationsfor
sulfide
similarancient,aswell asmodern,volcanogenic
deposits.Particularlyinterestingare the calculatedstability-relations of berthierine relative to other Fe-Al
silicates(Fig. 9). This diagramwas constructedfor a
of350oCunderconditionsofquartzsaturatemperature
tion using thermodynamicdata from SUPCRT (see
Bowerset al. 1984,and referencestherein),exceptthe
free energyand-enthalpydatafor daphnite(14 A) and
berthierine("7 A chamosite"),which are from Wolery
(1978,Table2). Despiteuncertainties
in the thermodynamic data,the calculationsshowthat berthierinehasa
similar, but smallerfield of stability relative to that of
daphnite( I 4 A Fe-richchlorite),andthereforeprobably
is metastable.
Basedon texturalrelations(e.g.,Fig.2D),
the Kidd Creekberthierineand muscoviteappearto be
coevaland may haveformed underequilibrium conditions in some of the samples,in agreementwith the
thermodynamicrelations.In a recentstudy of Ag-PbZn polymetallicveinsin the Ukraine,Rusinovae/ a/.
(1987) determinedthat berthierineformed simultaneously with sericiteand K-feldspar.The apparenttheo-
11 3 8
T]{E CANADIAN MINERALOGIST
Berthierine
\.-4.21"N
Daphnite
Kaolinite
log (a6+/ap+)
Ftc.9. Activity diagramshowingstabilityrelationsof minerals
in the systemFeG-K2G-AI2O3-SiO2-H2O
at 350"C and
500bars.Activitiesof mineralsandH2Oaresetat 1.0under
conditionsof quanz saturation.Thermodynamicdata and
calculationsfrom SUPCRT(seeBowerset al. 1984,arrd
referencestherein)exceptfreeenergy-and
enthalpydatafor
daphnite(14 A) andberthierine("7 A chamosite"),which
arefromWolery( 1978,Table2). Datapointsfor end-memberventfluids from 2l"N (OBS)andthe southemJuande
Fuca Ridge (Plume) were calculatedby J.K. Btihlke
(USGS)usingtheprogramSOLVEQ(Reed1982,Spycher
& Reed1989)andthefluid compositions
reportedby Von
Dammet a/. (1985)andVon Damm& Bischoff(1987),
respectively.
Note smallerfield of stabilityof berthierine
(dashed)relafiveto that of daohnite.
GalapagosRidge (Embleyet al. 1988)and the Kane
et al.
FractureZoneof theMid-Atlantic Ridge(DeLaney
1987),wherereportedFe-richchloritelikely contains
minorto majoramountsof berthierine.
The difficulty of identiffing berthierineby routine
methodssugoptical,X-ray, and electron-microprobe
geststhat much of the Fe-rich chlorite reportedfrom
modernand ancientmassivesulfide depositsmay instead be berthierine.Recognition of premetamorphic
berthierinein such depositsis importantbecauseit
of primarymineralassemblages
recordsthepreservation
early,Fe-richhydrotherdepositedby paragenetically
mal fluids.Additionalmineralogicalstudiesintegrating
dataareneededon
SEM,TEM, andelectron-microprobe
or weakly
layersilicatesfrom otherunmetamorphosed
massivesulfidedepositson land, and
metamorphosed
from moderndepositson theseafloor. Suchstudieswill
mineralcomposi
be usefulfor accuratelydocumenting
relationsin alterationzonesrelated
tionsandparagenetic
to massivesulfide deposits,and for improving our
understandingof fluid-rock reactionsin submarine
hydrothermal
systems.
ACKNOWLEDGEMENTS
The seniorauthorthanksL.T. Bryndziafor urging
X-ray verificationof theKidd Creek"daphnite",which
providedthebasisfor this study.We alsothankthelate
J.W. Hostermanfor acquiringthe XRD data, C.A.
andJ.V.Emery
Consolvoforhelpin samplepreparation,
and J.J.McGeefor SEM imaging.We are gratetulto
H.T. Evans,Jr., for the identificationof the halloysite,
with thermodynamic
andto J.K. Biihlke for assistance
calculations.Translationsof Russian articles were
kindly suppliedby N. Tamberg.We thankG.R.Robinson, Jr. and J.K. Biihlke for commentson an early
versionof the manuscript,and Jung-HoAhn and J.E.
Chisholmfor journal reviews.The scanningtransmissionelectronmicrocopeusedin this studywasacquired
undergrantEAR-87-O8276from the NationalScience
Foundation,andwas partially supportedby NSF grants
EAR-88-17080and EAR-86-'04170to D.R. Peacor.
of Kidd
refical incompatibility of this assemblage(Fig. 9) may We alsoacknowledgethe staffandmanagement
beanartifactofthe thermodynamic
data-base,
however, CreekMines and FalconbridgeLimited for providing
accessanddrill corefor study.
underground
particularlythepositionof theK-feldspar- muscovitequartzbuffer, andthereforedoesnot necessarilyconflict
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