709

BUIIETIN DE I'ASSOCIATION MINERATOGIOUE DU CANADA

rHE CANADIANTWNERATOOISTJOURNAL OF THE MINERATOGIGAT ASSOCIATION OF CANADA

Volume 33

The C anadian Mineralo gistVol. 33, pp.709-72t (1995)

August 1995 Part4

CONSTRAINTS FROM FLUID.INCLUSION DATAON THE ORIGIN OF THE JUBILEE CARBONATE-HOSTED Zn-Pb DEPOSIT,

CAPE BRETON, NOVA SCOTIA*

GUOKANG CHI AND MARTINE M. SAVARDGeological Suney of Canada Quzbec Geoscience Cente, P.O. Box 7500, Sainte-Foy, Quebec GIV 4C7

woNrmnorrxINRS - G4oressoarces, P.O. Box 7500, Sainte-Foy, Qulbec GIV 4C7

ABSTRACT

Aqueous (Aq) and hydrocarbon (HC) fluid inclusions were strdied in fibrous calcite (pre-ore), sphalerite, and coarse,anhedral calcite (syn- to post-ore) ofthe Jubilee Zn-Pb deposit, Cape Breton, Nova Scotia- The deposit is hosted by a limestonebreccia at the top of the Macumber Formation (imestones) and under the Canolls Corner Formation (evaporites). Aq inclusionsfrom different minerals have similar temperatures of first melting (42.1 to -46.7'C), indicating a H2O-NaCl-CaCl2compositional system. Salinities (wt%o), NaCV(NaCl + CaCl) weight ratios, and temperafires of homogenization (I) of Aqinclusions range from 21 to nVo,0.1.6 to 0.73, and 53 to 79oC for fibrous calcite, 15 ta 24Vo,0.26 to 0.64, and 59 to 228"C forsphalerite, and 12 to '24Vo, 0.L7 ta 0.72, and 66 to 224'C for anhedral calcite. The T6 - salinity correlation suggests that ahigh-temperature, high-5dinigy fluid f$t mixed with a low-t€mperature, high-safinity fluid, then mixed with a fluid of lowtemperature and salinity. HC inclusions coexist with Aq inclusions. The T1 of HC inclusions ranges from 34 to 89oC for fibrouscalcite,46 to 87'C for sphalerite, and 31 to 238'C for anhedrd calcite. Fluid pressures estimated from the intersection ofisochores of coexisting Aq and HC inclusions range from 175 ta 363 bars for the fibrous calcite, and from 160 to 398 bars forthe anhedral calcite. The microthermometric data suggest that the Jubilee deposit formed from a ho! metal-carrying brine in ashallow environment (probably less than 1500 m) characterized by a low background temperatue. Hydrocarbons migrated intothe limestone breccia before the mineralizing even! reacted with oxidized sulfur derived from the evaporites, and produced areservoir of reduced sulfur available for mineralization when the metal-carrying brine migrated tlrough.

Keywords: Zn-Pb deposi! carbonates, aqueous fluid inclusions, hydrocarbon fluid inclusions, basinal brines, Jubilee, CapeBreton, Nova Scotia-

Sornrens

Des inclusions fluides aqueuses (Aq) et dhydrocarbures (HC) ont 6t6 6tudi6es dans la calcite fibreuse (pr6-min6ralisation),la sphal6rite, et la calcite grossibre x6nomorphe (syn- i post-min6ralisation) du gfte e Zn-Pb de Jubilee, au Cap Breton,Nouvelle-Ecosse. l€ glte est encaiss6 par une brbche calcaire au sommet de la Formation de Macumber (calcaires), et en dessous

* Geological Survey of Canada contribution number 31794.

7L0

de la Formation de Carrolls Comer (6vaporites). I€s inclusions Aq des diff6rents min6raux ont des temp€ratures de premiOrefonte semblables (-42,1 d46,7'C), indiquant une composition dans le systdme HrG-NaCl-CaCl2. lrs salinit6s (7o, au poids),les rapports pond6raux de NaCV(NaCl + CaCl), et les temp6ratures dhomog6n6isation (16) des inclusions Aq varient de27 b,27c/o, 0,16 a 0,73, et 53 d 79"C pour la calcite fibreuse, de 15 d 247o, 0,26 d 0,64, et 59 d 228'C pour la sphal6rite, etde 1,2 d 24Vo, 0,I7 d 0,72, et 66 d 224"C pour la calcite x6nomorphe. La con6lation entre Th et la salinit6 suggdre qu'un fluide) temp6rature et salinitd 6lev6es se serait m6lang6 d'abord avec un fluide de faible temp6rature et de salinit6 6lev6e, et ensuiteavec un autre fluide de basses tempdratue et sa1init6. Des inclusions dTIC coexistent avec les inilusions Aq. La T6 desinclusions dTIC varie de 34 i 89oC pour la calcite fibreuse, 46 d 87"C pour la sphal6rite, et 31 e 238'C pour la calcitex6nomorphe. La pression des fluides, ddrivde par I'intersection des isochores des inclusions Aq et dHC coexistantes, varie de175 d363 bars pour la calcite fibreuse, et de 160 d 398 bars pour la calcite xdnomorphe. l,es donndes microthermom6triquessuggerent que le d6p6t de Jubilee s'est form6 l partir d'une saumure chaude m6tallifbre dans un environnement de faibleprofondeur (probablement moins de 1500 m) ayant une faible temp6rature. ks hydrocarbures ont migr6 dans la brbche calcaireavant la min6ralisation, ont r6agi avec le soufre oxyd6 d6riv6 des 6vaporites, et ont produit un r6servoir riche en soufre rdduitainsi disponible pour la min6ralisation lors du passage de la saumure m6tallifdre.

Mots-cl6s: d6pdt de Zn-Pb, carbonates, inclusions fluides aqueuses, inclusions fluides dhydrocarbures, saumures de bassins,Jubilee, Cap Breton, Nouvelle-Ecosse.

htrnooucuoN

The Jubilee Zn-Pb deposit on Cape Breton Island,Nova Scotia, is one of several base-metal depositshosted by Early Carboniferous carbonates of the LateDevonian - Permian Maritimes Basin (Fig. 1). Thesedeposits have been the subject of a number of recentstudies aiming to understand their origin and relation tothe evolution of the basin (e.g., Ravenhurst et al. 1989,Btrtt et al. 199$.

According to previous studies, the Jubilee depositshows similarities and differences with Mississippi-Valley-type (MVT) deposits (see Anderson &Macqueen 1988). Like MVT deposits, it is located nearthe edge of a basin, hosted by carbonates, controlled bya system ofpre-existing inrosity, and has a relativelysimple mineralogy. Hydrocarbon-bearing fluid inclu-sions are present in ore and gangue minerals (Heinet al. 1993). Unlike most MVT deposits, it is hosted bylimestone instead of dolostone (Paradis et al. 1993),

Krn*ffi*tt"

rITIII TRIASSIC.JURASSICF:=I IATE CARBONIFEROUS-PERMIANI EARTV CARBONTFEROUSlo o q DEVoN|AN-cARBoNtFERousf f i NNONYNIAN.MIDDLE DEVONIAN

o o o o os2o km i, .f,- 1 . - - . : i r

MARI I IMES BASIN

Flc. 1. Regional geological map of the southem margin of the Maritimes Basin (after Boehner et al. 1989) showing the locationof the Jubilee and several other deposits: I Jubilee Zn-Pb deposig 2 Pembroke Pb deposrt 3 Smithfield Pb-Zn deposit4 Gays River Zn-Pb deposit, 5 Walton Ba-Pb-Zn deposit. The inset map shows the regional setting of the Maritimes Basin(after Howie & Barss 1975).

TIIE JIJBII.F:p Zo-Pb DEPOSIT. CAPE BRETON 7l l

and mineralization seems to have been stronglycontrolled by faults Qlern et al. 1993). Temperatures offluid-inclusion homogenization range from 82-98'C inpost-ore barite (Hein et aI. 1993) ta 353-392"Cin sphalerite (Stewafi 1978), which is markedly higherthan in most MVT deposits.

Stable isotope studies (Armstrong et al. 1993,Fallara et al. 1994) have suggested that the Jubileedeposit formed from circulating basinal brines, and thathydrocarbons likely played an important role in theprecipitation of sulfides. However, little is knownabout the comFosition of the brines, their relationshipwith each other, and with the hydrocarbons. This lackof knowledge about the fluids direcfly involved inmineralization seriously hinders our understanding ofthe mechanisms that produced the deposit. Fluid inclu-sions in hydrothennal minerals represent samples ofthe fluids that once existed in the mineralizing $ystem,and can provide direct information about the compo-sition ofthe fluids and the physicochemical conditionsof the mineralizing processes. Fluid-inclusion studiesof reconnaissance nature have previously been carriedout (Stewart 1978, Hein et al. 7993). However, thesestudies measured homogenization temperatures of fluidinclusions, but did not report qu3qtitative data onfreezing temperatures. Consequently, the composi-tional systems and salinities of the fluids are unknown.

Besides, the significance of the reported large rangeof homogenization temperatures 1g11nins an openquestion.

This paper presents a systematic microthermometricstudy of aqueous and hydrocarbon-bearing fluid inclu-sions from, pre-, syn-, to post-ore minerals of tleJubilee deposir The main objective of this sfirdy is todetermine the compositional systems, snlinities, andtemperatures of the aqueous and hydrocarbon-bearingfluids present before, during, and after mineralization,and to evaluate the thermal regime, depth, andmechanisms ef mineralization.

Gsol-ocv oF TUE DEPosrr

The Jubilee deposit is located near an NNW-trending elongate dome @g. 2). T\e sftatigraphicsequence, from bottom to top, consists of conglomerateand sandstone of the Horton Group, and limestone(Macumber Formation) and evaporites (CarrollsCorner Formation) of the Lower Windsor Group. Alimestone breccia (<15 m) occurs at the top of theMacumber (Ilein et al. 1988, Graves et al. L990,FaTTara et al. 1994) and hosts the deposit.

A number of NW-striking faults occur in the area.The Jubilee fault, which extends northwest from thedome, and the Road fault along the northeastern margin

Flo. 2. Geological map of the Jubilee Zn-Pb deposit and schematic dishibution pattems ofZn + Pb grades multiplied by thickness in meters (Vom; aftetFallara 1995). Drill holesfrom which the samples ofthis study were collected are shown by filled circles.

712 THE CANADIAN MINERALOGIST

of the dome (Frg. 2), are the most prominent. They arenormal faults with very high angles of dip.

Mineralization is spatially associated with theJubilee fault (the main ore-zone) and the Road fault(Fig.2). Sulfides (pynte, marcasite, sphalerite, galenaand minor chalcopyrite) occur as cements in thebreccia and as veinlets or disseminations in the matrixand in recrystallized fragments. Massive, high-gradeore locally replaces limestone (Fig. 2). The maingangue mineral is calcite; no dolomite has been found(Paradis et al. 1993). Minor gangue minerals includebarite, anhydrite and gypsum. The total reserves areestimated at 0.9 million metric tonnes grading 5.2VoZnand L.4Vo Pb (Hein et al. 1993).

The paragenetic sequence at the Jubilee deposit wasstudied by Paradis et al (1993) andFalTara et al. (1994),and is summarized as follows: (1) fibrous calcite,Q) pyne and marcasite, (3) sphalerite, (4) galeta,sphalerite and coarse, anhedral calcite, (5) coarseanhedral calcite, and (6) sulfates Oarite, anhydrite andgypsum).

SaNpLes axo PtrnocnapwoF FLLD h,tct-ustotts

Nine samples from five drill cores in the main orezone, ono sample from a drill core near the Road fault(Fig.2), and a sample from the main showing on thesurface, were prepared for fluid-inclusion study. Allsamples from drill cores in the main ore-zone containfibrous calcite, pynte - marcasite, sphalerite, galena,and anhedral calcite. The sample from the Road faultcontains fibrous and anhedral types of calcite, but doesnot contain sphalerite. The sample from the surfaceshowing contains massive, fine-grained sphalerite thatreplaces limestone; the sphalerite in this sample doesnot contain fluid inclusions suitable for microthermo-metric measurements.

Fibrous calcite occurs as cement partly filling thesecondary pores of the limestone breccia. It mainlypredates pydte - marcasite, and invariably predatessphalerite. Two petrographic types of sphalerite weredistinguished in the samples, an anhedral q4)e, veryabundant, with brown to light yellow zonations thattypically contain numerous tiny fluid inclusions, and aeuhedral type, less abundant, yellow, and free ofinclusions. The zoned sphalerite occurs as layersencrusting fibrous calcite and pyrite - marcasiteo or asveinlets cutting fibrous calcite, pyrite - marcasite, andbreccia fragments. The euhedral sphalerite postdatesthe zoned sphalerite, and occurs with galena andanhedrat calcite, which fills the residual pores betweenbreccia fragments. The anhedral calcite is partlycontemporaneous with, but mainly postdates, zonedand euhedral types of sphalerite.

Fluid inclusions were studied in fibrous calcite(pre-ore), zoned sphalerite, and a:rhedral calcite (syn-to post-ore). Both aqueous and hydrocarbon-bearing

fluid inclusions were observed in these minerals. Mostaqueous fluid inclusions comprise a liquid and a vaporphase at room temperature (Ftg. 3A). A few aqueousfluid inclusions comprise only a liquid phase. Nodaughter minerals were observed in any ofthe aqueousfluid inclusions. Hydrocarbon fluid inclusionscomprise a liquid and a vapor phase as well at roomtemperature (Fig. 3B), and are distinguished ,fromaqueous fluid inclusions by their coloro freezingbehavior, and fluorescence under blue light excitation.The liquid phase of hydrocarbon fluid inclusions iseither brown to yellow-brown (Ftg. 3B) or colorless@gs. 3C, D); the former is more abundant than thelatter. Some inclusions comprise both a brown hydro-carbon liquid and a colorless hydrocarbon liquid, plusa vapor phase (Fig. 3E). A few inclusions comprise anaqueous liquid, a hydrocarbon liquid, and a vaporphase @ig. 3F).

In fibrous calcite, aqueous fluid inclusions areabundant and randomly distributed in three dimen-sions. These inclusions are likely primary according tothe criteria of Roedder (1984). However, since theseinclusions are densely distributed, it is possible thatsome of tlem are controlled by microfractures(secondary), but cannot be distinguished from theothers in the thin sections. Some aqueous fluidinclusions are distributed along healed fractures cross-cutting crystal boundaries. These secondary inclusionscan readily be distinguished from the randomlydistributed inclusions. Hydrocarbon fluid inclusionsare scat[ered among the randomly distributed popula-tion of aqueous fluid inclusions, and are consideredprimary because no fracture control has beenobserved. All the hydrocarbon fluid inclusions infibrous calcite are brown to yellow-brown. No color-less hydrocarbon-bearing fluid inclusions have beenobserved.

It zoned sphalerite, numerous aqueous fluidinclusions occur along gro*th zones defined by colorzoning @g. 3G). These inclusions are primary, but arenot amenable to microthermometric analysis becausethey are less than 1 ttm.in diameter. A number ofaqueous fluid inclusions occur in clusters lackingfracture control, and some of them are relativelyisolated. These inclusions are considered primary anddistinguished from secondary inclusions in healedfractures cross-cutting crystal boundaries. Hydro-carbon fluid inclusions are much less abundant thanaqueous fluid inclusions. They were observed withinclusters of aqueous fluid inclusions, and are alsolikely primary. Both brown to yellow-brown andcolorless hydrocarbon-bearing fluid inclusions wereobserved.

In anhedral calcite, aqueous fluid inclusions occruin clusters lacking fracture control or in short healedfractures terminating within individual crystals. Someinclusions are relatively isolated @g. 3A). Theseinclusions are likely primary or pseudosecondary.

THE JIIBI n.F Zn-Pb DEPOSIT. CAPE BRETON 713

Ftc.-laA.. An isolated aqueous fluid inclusion in alhedral calcite; B: an isolated hydrocarbon fluid inclusions (yellow-brown,HC-l) in anhedral calcite; C: hydrocarbon fluid inclusions (colorless, HC-2) in sphalerite at room temperatue; D: sameinclusions as B at -36'C (note that the vapor bubble expanded and became irregular in form); E: an inclusion comprisinga colorless hydrocarbon liquid QIC-2), a brown hydrocarbon liquid (HC-l), and a vapor phase (Vp), in anhe&al ;abiteF: an inclusion comprising an aqueous liquid (Aq), a brown hydrocarbon liquid (HC-l), and a vapor phase (Vp), in anhedrafcalcite; G: primary fluid inclusions distributed along growth zones of a sphalerite crystal.

Secondary inclusions in healed fractures cross-cutting crystal boundaries are abundant. Hydrocarbonfluid inclusions are either scattered in clusters ofaqueous fluid inclusions, or occur in healed fracturescross-cutting crystal boundarie$. The former is likelyprimary, and the latter is secondary. Both brorrun toyellow-brown and colorless hydrocarbon-bearingfluid inclusions were observed in the clusters. whereasonly brown to yellow-brown hydrocarbon-bearing fluid inclusions were found in the healedfractures.

The petrographic study described above suggeststhat aqueous fluid and liquid hydrocarbon were co-existent during the precipitation of fibrous calcite,sphalerite, and anhedral calcite. They may haveoccurred as immiscible liquids and may have beentrapped as separate aqueorn and hydrocarbon fluidinclusions. Occasionally, both aqueous and hydro-carbon fluids were trapped in the same inclusion (i.e.,heterogeneous trapping, Fig. 3F).

Fluid inclusions that are likd primary or pseudo-seconda4r, with the longest dimension ranging from5 to 54 trun (mainly >10 FLm), were selected formicrothermometric analysis. Some secondary inclu-sions also were studied for comparison.

Anaryrrcar ME"[roos

Homogenization temperatures of aqueous andhydrocarbon fluid inclusions, and melting temperaturesof aqueous fluid inclusions, were measured using aU.S.G.S. heating-freezing stage that was calibrated toa precision and accuracy of t 0.1'C with syntheticstandard fluid inclusions provided by Fluid Inc.Homogenization temperatures were measured for eachselected fluid inclusion in a chip of sample prior togsoling runs, in order to avoid the effect of stretchingcaused by fluid freezing.

The fluorescence spectrum of individual hydro-carbon fluid inclusions was measured using a Zeiss trphotomicroscope, equipped with a F{BO W2 100 high-pressure mercury lamp, a BG-12 excitation filtero aZeiss FL prism, an oil immersion NEOFLUAR l00xobjective, and an optovar set at 1.25x. The objectivediaphragm apertures were 3, 6 and 10 pm, and themeasuring diaphragm aperture was 3 pm. The excita-tion wavelength is 405 nm (blue lighg. The fluores-cenca specta ofthe hydrocarbon fluid inclusions werecalibrated against a uranyl glass GG17 standard at eachl0 nm interval in wavelength ranglng from 400 to700 nm.

7t4 TIIE CANADIAN MINERALOGIST

RESULTS

Microthermometric results of aqueous and hydro-carbon fluid inclusions from fibrous calcite, zonedsphalerite, and anhedral calcite are summarized inTable 1, and are described as follows. All the descrip-tions, unless otherwise specified, apply to the fluidinclusions that are likely primary or pseudosecondaryotr the basis of their petrography. The aqueous fluidinclusions in fibrous calcite classified as type P* inTable I are considered primary based on T6 - salinityrelationship, which will be discussed in detail in thenext section.

Aque ous fluid inclusions

Aqueous fluid inclusions from different mineralsshow similar temperatures of first melting, ranglngfrom -62.1 to 46.7"C (table l). These frst meltingtemperatures are compatible with those found in thesystem H2O-NaCl{aClr. The first melting tempera-

tures of such system are usually within 3'C of theeutectic temperaflre C52"C) if stable salt hydratesform during cooling, but they may be as low as -80oC

if there are metastable salthydrates (Davis et al. 1990).Minor amounts of other cations such as Mg2* and K+are possibly present, but cannot be examined in thepresent study.

Melting temperatures of hydrohalite (NaCl'2H2o),which was identified by its tabular shape and higherrelief than ice, range from -37.6 to -24.9, -33.9 to-26.0. and -37.2 to -24.6"C for fluid inclusions fromfibrous calcite, sphalerite, and anhedral calcite, respec-tively (Iable 1). These temperatures are considered tobe approximate because hydrohalite crystals cannot beseen clearly in the case of many inclusions.NaCV(NaCl + CaCl) weight ratios, estimated frommelting temperatures of hydrohalite by using theH2O-NaCl{aCl2 diagram (Oakes et al. 1990) (Fie. ),range from 0.16 to 0.73, 0.26 to 0.64, and 0.17 to 0.72for fluid inclusions from fibrous calcite, sphalerite, andanhedral calcite, respectively Clable 1).

Host fype

Th( o c) Salinity (wt%) NaCyNsCl+ CaCl2)

fmgg @d lvlm md

{mbq Sd.Dev.

tmgemd M@md{mber sd. Dw.

md M@@d

r StilDw.

Fibrc!8

Calcfte

{qP{Q PN

{Q: sItc(br): P

u.1-204.E(4O eoj(r-36.O12.v79.2(r') 66.1(+/4.8)t0.7-69.6(4) E6.0({./4.0)t4.348.7 Q9, 51.2({r'-119)

r4$26.8Q8) 20.W4.4)20.8-26.8(15) 23.6(t t-rs)Q1-BA@\ 13.4(+l-Ot

164.73(19) 038(+/-0.14)160.73(9) 0.40(t-0.1t32453(4) 0.44({r'-O.09)

Sphalsite \Q: P\ Q Slqbf):P{c(cD. P

i8 s-na tpz) 92J(d-38.8)t6.+9O2(4' 832(t-5.8){5.?0)t5.8-s7.1(2) 715(+.t-2Lr)

14.62i.6(17)'t7 5(tl-3.o,15J-18.9(2) 772.(+l-25,

0.45(44.r2)0.36(+/4.09)

tuhedmlCstg'lB

\(! P\Qslc(br): PIqcD:PIc(h): S

'6 2:lA.tt(5lt 1 01.1(+/-37.61103-87.3(9) n.4$l-s.9'tL a-87.q66) EE.r(+-48.0).6.r -r2r 3Q> tt3.7 (4 -1O.7.t33-983(v)t 54.1(t-15.1)

Le24.3(31') 15.2{11-3s)33-r4.4A 8.9(44,4)

r7432Q6, o.44{1't4.13)334J7(O 0.45(+/{.09)

AQ aqqeousflddhcl$toqs({h):brosntoyellow+omtydooafi(nflddh0lsd@;uc(d):coldl$ltdoca$(Efldd irchdq n Ehary (nstrdfig 1x€odos€cmdry) tnsed o petmgr@y; Pr: dosy baeed o lmoplzad@Mp€6ahrs- saliDityletad@; S: s€o@d8y; Tn-lst first-Eethg bqEr8@; TB-SH: metdngtmpsafre dhtaMalIei TB-geO nsldng mperatrs of icq 1lr: hmogdzat'ro hry€rde.

TAEIA 1. MICROIHKMOMETRIC DATA Ori[ AQITEOUS At{D ETDROCARBo{ FLIIID INg.UsIoNs

Hct rr?e

Tm-ls(- o c) Tn-HHG oC) Tn-H2C(- o C)

tngemd M@md\ftmbq Sd.Dw.

lmgemd M@md{umbq Sd.Dfl.

md Mmmdr Sd.Dev.

FibroBCalcib

\QP\ q F\qs

836LlQ5 s45(+!-3i')4E3421(13) 5s3(+/-3.E)49.+54.1(4) 51.q+f1.9)

t4.9-37.q1' 31.2(+t-3.3)r6247.q9' 30.9(+/-3.6),:1.8-323(4') 29.8(4-1.9)

e.9-34.3Q8' 192(4-'7.6)19J-343(15) 25.r(4-4n8X-9J(4) 93(+/4J)

Sph8lqiE \Q: P\Q: s

s0.8-59.4(17) 5t.9(4-2.6)56.+572Q) 56.8(+r'-0.6)

.0-339(9') 29.s(4-2.4)29.9-33.W) 31.5(4-22'

10.625.3(l'.t) LqX(+r'4nrr.Gt62(2) L1,N'-X.3'

ADh€dnl

C8lciE

\Q:P{QS

46.7-60.3(3E) 535({-/3.0)50.3-55.8(8) 53.1(r-1.8)

24.6-37.2(25) 29.9(4 -2.8)

nt-32.0(6) 29s(4-r.8).64.qs1\ 12.qt-5o3-10.4{7) 9.9rj/4.4)

O Fibrous calciteo Sphalerite

x Anhedral calcite

Liquid+Ice

Melting temperatures of ice range from -34.3 to-9.9, -25.3 to -10.6" atd -27.O to -7.6oC for fluidinclusions from fibrous calcite, sphalerite, and anhedralcalcite, respectively (Table 1). Melting temperatures ofice that indicate metastability, i.e., as revealed by avapor bubble appearing at the momenl ice melts, areuseless and are not reported in Table 1. Salinities werecalculated using melting temperatures of ice andNaCU(NaCl + CaCl) ratios with the equation 2 ofOakes e/ al. (1990). For fluid inclusions for which themelting temperature of hydrohalite was not measured,the average NaCU(NaCl + CaCl) ratio of fluidinclusions in the same mineral (0.38 for fibrous calcite,0.45 for sphaleriie, and0.44 for anhedral calcite) wasused to calculate salinities. The salinities obtainedrange from 14.0 to 26.8, L4.6 to 23.6, and 11.6 to24.3 wt%o for fluid inclusions from fibrous calcite.sphalerite, and anhedral calcite, respectively (Iable l).

Temperatures of homogenization (to the liquidphase) range from 41.1 to 204.8,58.5 to 228.1, and66.2 to 22f+.4"C for fluid inclusions in fibrous calcits.sphalerite, and anhedral calcite, respectively @g. 5).

Flc. 5. Histograms of homogenization temperatures of aque-ous fluid inclusions from fibrous calcite, sphalerite, andanhedral calcite. The hatched area for fibrous calcite reo-resent fluid inclusions that are most likely primary, on thebasis of homogenization temperature - salinity relation-ship (see Fig. 8).

4A @ 80 lm DA tN 160 180 m n0

Homoge,nizafion Temperatue (oC)

TIIE JIIBILEE Zn-Pb DEPOSIT. CAPE BRETON

IIzO

\

\&

715

Ftc.4. Composition of prima-ry aqueous fluid inclu-sions from fibrous calcite,sphalerite, and anhedralcalcite plotted in thesystem H2O-NaCl-CaCl,(isotherms are fromOakes et al.1990\.

/,

Av

$_,t

E D

P 8F

b 4

2o

) r zr

o 6o

E +z

7t6 T}IE CANADIAN MINBRALOGIST

Secondary fluid inclusions in different host mineralsshow similar and relatively convergent microthermo-metric characleristics. Salinities, NaCV(NaCl + CaCl2)ratios, and homogenization temperatures range fromI2.7 to 13.8 wt%o,032 to 0.53, and 80.7 to 89.8oC forfibrous calcite, from 15.5 to 18.9 wt%o,0.29 to 0.42,and 76.4 to 90.2"C for sphalerite, and from 13.3 to14.4 wt%o,0.33 to 0.57, and 70.3 to 87.3'C for anhedralcalcite.

Hy droc arb on flaid inclusions

Brown to yellow-brown and colorless hydrocarbonfluid inclusions display different behaviors upon cool-ing. The vapor bubble of brown to yellow-brownhydrocarbon fluid inclusions expands very slightlyduring cooling to liquid nitrogen temperature, and theliquid phase does not show an obvious phase-change.On the other hand, the vapor bubble within colorlesshydrocarbon fluid inclusions expands greatly andbecomes irregular upon cooling to about -5oC

@gs. 3C, D), indicating that the liquid phase becomesfrozen and shrinks.

Bbth brown to yellow-brown and colorless hydro-carbon fluid inclusions are strongly fluorescent underblue light excitation. Fluorescence spectra @ig. 6) indi-cate that the colorless hydrocarbon fluid inclusionshave a lower wavelength of spectral maximum (L*)(530 nm) than brown to yellow-brown inclusions(550-570 nm). Brown to yellow-brown hydrocarbonfluid inclusions with relatively large vapor bubblesfuave a highsl f.* (570 nm) than those with relativelysmall vapor bubbles (550 nm).

Ftc. 6. Fluorescence spectra of hydrocarbon fluid inclusionsunder blue light excitation. I. Randomly distributed hydro-carbon fluid inclusions from fibrous calcite (threeinclusions); tr. isolated and randomly distributed hydro-carbon fluid inclusions from anhedral calcite: IIa. brownto yellow-brown hydrocarbon fluid inclusions with rela-tively large bubble (five inclusions); trb. brown to yellow-brown hydrocarbon fluid inclusions with relatively smallbubble (six inclusions); IIc. colorless hydrocarbon fluidinclusions (one inclusion); III. secondary hydrocarbonfluid inclusions @rown to yellow-brown) from anhedralcalcite (tlree inclusions).

m i|lo 60 80 100 120 140 160 180 m m 2N

Homogenization Temperafure (o C)

FIc. 7. Histograms of homogenization temperatures of brownto yellow-brown hydrocarbon fluid inclusions fromfibrous calcite and anhedral calcite.

The fluorescence spectrum is a function of both thegross composition of the trapped hydrocarbons andtheir maturation state; aromatic and polyaromaticcompounds are mainly responsible for the fluorescenceproperties (Guilhaumou et al. 1990). Higher values ofL-* indicate higher thermal matuation and aro-maticity (Khorasani 1987). However, no quantitativecorrelation between a fluorescence spectrum and aspecific composition and maturity of the hydrocarbonshas been established.

Temperatures of homogenization (to the liquidphase) of hydrocarbon fluid inclusions are summarizedin Table 1; most of them were obtained from brown toyellow-brown hydrocarbon fluid inclusions in fibrousand anhedral calcite @g. 7). Only a few hydrocarbonfluid inclusions in sphalerite were measured forhomogenization temperatures (fable 1). Homogeni-zation temperatures ofbrown to yellow brown hydro-carbon fluid inclusions range from 34.3 to 88.7'C forprinary inclusions in fibrous calcite,31.0 to 237.6"Cfor pnmary inclusions in anhedml calcite, and 33.4 ta98.3'C for secondary inclusions h anhedral calcite.

DlscussloN

The microthermomefric data documented above canbe used to infer the compositions, lemperatures andpressures of the fluids existing in the hydrothermalsystem before, during, and after the formation of thedeposir The relationship between the distinct fluidsand their role during mineralization, the thermal evolu-tion of the hydrothermal system, the pressures of thefluids and corresponding depths, and the mechanismsof ore precipitation are discussed below.

* o'9'E o.eqE i a

I o.oI o.spE 0.4

; 0.,

€ 0.2E o.r \

TIIE JUBILEE Zn-Pb DEPOSIT" CAPE BRETON 7r7

Mahiple aqueous fluids and mixing

A wide range of salinities and homogenizationtemperatures of aqueous fluid inclusions is obvious(fable 1, Fig. 5). On a plot of homogenization temper-atwe versus salinity (Fig. 8), it is shown that primaryinclusions in fibrous calcite mainly plot in an area(A in Fig. 8) with homogenization temperaturesrangng from 53 to 79"C and salinities ranging from2l to ZT wtVo (lab7e 1, type P*). These inclusions arelikely representative of the aqueous fluid presentduring the precipitation of fibrous calcite. However,some inclusions in fibrous calcite plot in areas that aredominated by fluid inclusions from sphalerite andanhedral calcite. These inclusions, although assigned toprimary inclusions from petrographic judgemeng arelikely secondary inclusions that were superimposed onfibrous calcite during the precipitation ofsphalerite andanhedral calcite.

Primary inclusions in sphalerite and anhedral calciteplot in a wide area varying from low salinity - lowtemperature (C in Fig. 8) to high salinity - high tem-perature (B in Fig. 8). These wide ranges can beexplained by mixing of fluids. Two stages of mixingare envisaged. Firstly, a high-salinity high-temperaturefluid @ in Fig. 8), which likely was the metal-carryingfluid, mixed with a high-salinity low-temperature fluid(A in Fig. 8), which saturated the pores beforemineralization (i.e., the fluid present during precipita-tion of fibrous calcite). This stage of mixing resulted inhigh salinities and intermediate temperatures, whichdefine the subhorizontal mixing-line in Figure 8(mixing 1). Secondly, perhaps during the v/aning stage

of mineralization, the intermediate fluids produced bymixing 1 mixed with a third, low-temperature - low-salinity fluid (C in Fig. 8). This stage of mixingconstitutes the oblique line in Figure 8 (mixing 2). Theproportion of the third fluid may have increased withtime, and eventually dominated the hydrothermalsystem in the post-ore stage, as indicated by secondaryinclusions in anhedral calcite, which plot in the low-salinity, low-temperature area in Figure 8.

Low temperatures of the early fluid present duringthe precipitation offibrous calcite (fluid A) and ofthelate fluid present after precipitation of anhedral calcite(fluid C) probably reflect conditions of burial of thedeposit. The metal-carrying fluid (fluid B), however,was likely derived from a deep source characterized byhigh temperature and high salinity. The high salinity offluid A may have been caused by addition of saltsdissolved from evaporites during a reaction betweenoxidized sulfur in the evaporites and hydrocarbons, aswill be discussed later.

Thzrmal regime of the lrydrothermal system

The above discussion indicates that the hydro-thermal system of the Jubilee deposit evolved from alow-temperature state before mineralization, through ahigh-temperature state during mineralization, and backto a low-temperature state toward the sTaning stage ofand after mineralization. However, from Figures 5 and8, it can be seen that the number of aqueous fluidinclusions in sphalerite and anhedral calcite with a hightemperatue of homogenization is limited. A questionthat arises is whether or not these high-temperature

9zoe

€ ts(h

tra , . t '

--n'furui'-: -- 6

lg fib-* -ldt"; pd.rty-

l. sphalerite;prinaryl o anhedral calcite; prirnaryI X anhedral calcite; secondary

l0

150Homoge,rization Tempsatuo 0 O

Frc. 8. Homogenization temperature - salinity diagram ofaqueous fluid inclusions fromfibrous calcite, sphalerite, and alhedral calcite. Dashed lines show mixing trends(see the text for explanation).

7L8 THE CANADIAN MINERALOGIST

inclusions truly record a high-temperature event. Weargue in favor of the validity of these high-temperaturedata on the basis of several lines of evidence. Firstly,fluid inclusions with necking-down features have beenavoided during selection of fluid inclusions formicrothermometric measurements. Artificial stretchingdue to freezing of the fluid has been overcome byperforming heating before freezing runs. Stretchingdue to natural heating does not seem to have happenedbecause there is no evidence that the area has beenheated to higher temperatures after the formation of thedeposit. Secondly, high temperatures of homogeniza-tion of fluid inclusions similar to those measured in thisstudy also were recorded in other base-metal depositshosted by carbonales of Lower Windsor Group in NovaScotia, e.9., 123-220"C for the Sugar Camp showing,Cape Breton Island (Chi & Savard 1995), 80-250'Cfor the Gays River deposig 120-32O'C for the Waltondeposit (Burtt et al. 1994), 130-180'C for theSmithfield deposiq and 160-250'C for the Pembrokedeposit @avenhurst et al. 1989) (see Fig. 1 for locationof the deposits). Thirdly, higher temperatures ofhomogenization (353-392'C, 9 inclusions) insphalerite from the main showing of the Jubilee deposithave been reported (Stewart 1978). Although we didnot find fluid inclusions large enough for micro-thermometric study in the fine-grained replacivesphalerite from the main showing, and therefore wereunable to confirm the accuracy of these high tempera-tures of homogenization, fluids that formed massivemineralization may have had an even higher tempera-ture than those we measured.

The limited number of fluid inclusions with hightemperatures of homogenization may be related to thefact that the high-temperature metal-bearing fluid wascooled rapidly because the ambient temperature of thedeposit was considerably lower. Mixing of the high-temperature fluid with the low-temperature fluidpresent in pre-mineralization pores inevitably acceler-ated the cooling process. Many high-temperature fluidinclusions were likely trapped in sphalerite, but itseems that they belong to the group of inclusions thatare too small for microthermometric measurements.The number of fluid inclusions studied neither reflectswhich temperature range was dominant during themain mineralization" nor the relative abundance ofthe respective fluid end-members.

The high temperatures of homogenization of theJubilee deposit, and those of other base-metal depositshosted by carbonates of Lower Windsor Group in NovaScoti4 are higher than those found in most MVTdeposits (100-150'C, Roedder 1984, p.416), but aresimilar to the Irish-type of carbonate-hosted base-metaldeposits (100-240'C, Hitzman & Large 1986). It islikely tha! as in the case ofthe hish-type deposits, theJubilee and other base-metal deposits of the MaritimesBasin formed in a more active tectonic and geothermalregime than typical MVT deposits. Clearly, the Jubilee

deposit was in a low-temperature burial setting beforeand after mineralization. Our on-going study of organicmatler in the host rocks of the Jubilee deposit indicatesthat the host rocks did not attain thermal equilibriumrvi*1 &s high-temFerafire mineralizing fluid, probablyowing to rapid cooling. Therefore, the Jubilee depositrepresents a case in which the deposit formed from hotfluids in a cool background (Sangster et al.1994).

Fluid pressure and depth estimation

The depth of mineralization of the Jubilee deposithas been difficult to determine because the age ofmineralization is unknown and therefore the thicknessof cover at the time of mineralization cannot be esti-mated from stratigraphic reconstruction. Severalauthors (e.g., Narr & Bumrss 1984, Mclimans 1987,Walgenwitz et al. 1990) have used the intersection ofisochores of coexisting aqueous and hydrocarbon fluidinclusions to estimate fluid pressures and correspond-ing depths. Petographic observations indicate thataqueous fluids and liquid hydrocarbons coexisted asimmiscible phases during the precipitation of fibrouscalcite, sphalerile, and anhedral calcite, as well as afterthe precipitation of anhedral calcite in the Jubileedeposit. The homogenization temperatures of hydro-carbon fluid inclusions are generally lower than thoseof coexisting aqueous fluid inclusions (Iable 1). Thisindicates that both aqueous and hydrocarbon fluidswere liquid at the time they were trappe4 becausehydrocarbons have a higher bubble-point curve and alower isochore slope in temperature-pressure coordi-nates than aqueous fluids, and the intersection of thetwo isochores lies in the field of liquid (e.9., Narr &Bumrss 1984, Walgenitlz et al. l99O). If bothisochores of coexisting aqueous and hydrocarbon fluidinclusions can be determined. their intersection can beused to estimate the pressure of trapping.

Isochores of aqueous fluid inclusions can be calcu-lated by using the FLINCOR program @rown 1989),with the fluid system being approximated byH2G-NaCl. The errors introduced by this approxima-tion are negligible, according to the experimental dataof Z,rarlg & Frafiz (1987). The isochores of hydro-carbon fluid inclusions, however, are difficult to deter-mine, because the composition of the hydrocarbons isunknown. In practice, isochores of hydrocarbon fluidinclusions can be approximated by crude oils (e.9.,Narr & Bumrss 1984). In order to obtain a broadestimate of fluid pressure (and depth) of the Jubileedeposit, fts minimum and maximum bubble-pointpressures of crude oils reported by Mclimans (1987)and Walgenw\tz et aL (1990) were used to constructthe isochores. These were located by extrapolationfrom the data of Walgenwitz et al. (1990), who haveused the temperatures and pressures of decrepitation ofhydrocarbon fluid inclusions to constrain the slopesof the isochores.

Fibrous caldte I teirnaryinausionsy' $

TIIE JIIBn F'F Zn-Pb DEPOSIT. CAPE BRETON 719

H

gooI

a 6 m

9 4 m6a

f ; zm

e€tsog

0 50 lm 150 ?N

Temperature f C)FIc. 9. Intercections of isochores for primary fluid inclusions

in fibrous calcite (A), primary inclusions in anhedral cal-cite (B), and secondary inclusions in anhedral calcite (C).Aql and HCI represent isochores for Mean - StandardDeviation, and Aq2 and HC2 represent isochores forMean + Standard Deviation, for aqueous and hydrocarbonfluid inclusions, respectively. The lower and upper limitsof the bubble-point curve of hydrocarbon fluid inclusionswere taken from Mclimans (1987) and Walgenw.rv. et aI.(1990), respectively. The isochores ofaqueous fluid inclu-sions were calculated by using the FLINCOR Fogram@rown 1989), with the fluid system being approximatedby H2O-NaCl. The isochores of hydrocarbon fluid inclu-sions were extrapolated from the data of Walgenwitz et al,(1990). Shaded areas indicate possible range offluid pres-sl[€s.

Isochores were calculated for primary aqueous andbrown to yellow-brown hydrocarbon fluid inclusions infibrous and anhedral calcite and for secondary aqueousand hydrocarbon fluid inclusions in anhedral calcite

(Frg. 9). Isochores were not calculaled for fluid inclu-sions in sphalerite because only a few hydrocarbonfluid inclusions were measured for homogenizationtemperafures. In order to evaluate the possible rangeof fluid pressures, mean values t standard deviations ofhomogenization temperatures and salinities of aqueousand hydrocarbon fluid inclusions (Iable 1) were used:66.1 t 8.8'C (16 of Aq), 5L.2 t ll.g"C (f1 of HC),and 23.6 + 1,.9 wtvo (salinity of Aq) for primaryinclusions in fibrous calcite; 101.1 t 36.7'C (16 ofAq), 88.1 t 48.0'C (t6 of HC), and 15.2 t 3.5 wt%oGalinity of Aq) for primary inclusions in anhedralcalcite,77.415.9'C (I1 of Aq), 54.1 + 15.l'C (fu ofHC), and t3.9 + 0.4 tttt%o (salinity of Aq) for secondaryinclusions in anhedral calcite. The shaded areas inFigure 9 indicate possible ranges of fluid pressures.The fluid pressures thus calculated range from 175 to363 bars during precipitation of fibrous calcite, from160 to 398 bars during the precipitation of anhedralcalcile, and from 190 to 441 bars after this episode.

Because the Jubilee deposit was overlain by a thicksequence of evaporite of the Carroils Corner Formationthat constitutes an impermeable cover, the fluidpressure in the syslem was possibly close to lithostatic.Assuming a lithostatic system with a rock density of2.7 glcfr, the depths corresponding to the fluidpressures calculated above range from 661 to 1371 mduring the precipitation of fibnous calcite, 604 to1503 m during precipitation of anhedral calcite, and718 ta 1666 m after this episode. It is likely that theJubilee deposit formed at a depth less than 1500 m.These results agree with recent studies of hydrocarbonsource-rocks showing that the Horton and basalWindsor Groups sediments a few tens of kilometerswest of our study area did not pass the oil windowconditions, i.e., drd not get buried deeply (e.9., Fowleret al. t993\.

M e chanisms of s ulfile p re c ip itatio n

The precipitation of sulftdes may be caused eitherby a drop in solubility (due to temperature drop, fluid-rock interactions, etc.) if the metals were transportedtogether with reduced sulfur, or by mixing of a metal-carrying fluid with a reduced sulfur-emiched fluid(Sverjensky 198 1). Anderson (1975) pointed out that ifmetals and reduced sulfur were transported togetherothe solution must be very acid. Hayashi et aL (1990)demonstrated that zinc sulfide complexes ca:rnot bsresponsible for the significant transport ofzinc to formeconomic deposits. Sulfur isotopes of sulfides of theJubilee deposit indicate that sulfur was likely derivedfrom the evaporites of the Carrolls Corner Formation(Fallara 1995).

The presence of primary hydrocarbon fluid inclu-sions in fibrous calcile suggests that liquid hydro-carbons migrated into the high-permeability zonerepresented by the limestone breccia before mineral-

2@

Anhdralcalcite /(Primaryinclusions) /

(B)

dwAnhedralcalctte | | (C)

720 TTIB CANADIAN MINERAI'GIST

ization. Carbon isotope data suggest that the carbon offibrous calcite was mainly derived from oxidationof hydrocarbons (Armstrong et al. I993,FaIlna et al.1994). It is likely that hydrocarbons reacted withsulfate (Anderson & Garven 1987) or thiosulfate(Spirakis & Heyl 1993) derived from the evaporiteswithin and overlying the limestone breccia, producingoxidized carbon and reduced sulfur.

The reduced sulfur was possibly preserved in areservoir due to the sealing ofthe overlying evaporites.At a later time, the metal-carrying fluid migrated intotle reservoir, mixed with the pre-existing fluid, reactedwith the reduced sulfir, and precipitated Zn and Pbsulfides.

CoNcr-usroNs

The microthermometric data of fluid inclusionsfrom fibrous calcite (pre-ore), sphalerite, and anhedralcalcite (syn- to post-ore) indicate that the Jubileedeposit probably formed in a shallow (less than1500 m) burial environment with low backgroundtemperature (about 50-90'C), into which was infro-duced a hot (up to 230'C), metal-carrying brine duringmineralization. The evolution of the mineralizingsystem can be summarized as follows. At some time inthe premineralization period, liquid hydrocarbonsmigrated into the limestone breccia and reacted withoxidized sulfur (sulfate or thiosulfate or both) derivedfrom the evaporites, producing a reservoir enriched inreduced sultur and a high-salinity (21-27 wtEo)aqueous fluid, from which fibrous calcite precipitated.During the major period of mineralization, a base-metal-carrying aqueous fluid of high salinity (about24 vtt%o) and high temperature (up to 230'C) enteredthe reservoir of reduced sulfur and hydrocarbon, mixedwith the pre-existing fluids and cooled rapidly, andprecipitated Zn-Pb sulfides. Toward fts ysaning stageof mineralization, another fluid, characterized byrelatively low salinity (about 13-14 wtTo) and lowtemperature (about 70-90'C), affected the mineral-izing system, and eventually dominated the hydro-thermal system in the post-ore stage.

Acrc{oWLEDGEMB.lrs

This study was financially supported by the Canada- Nova Scotia Cooperation Agreement on MineralDevelopment. We thank Don Sangster, SuzanneParadis, Ean Kontak and Francine Fallara for helpfirldiscussion, Jean-Claude 86rub6 for the doublypolished thin sections, Luce Dub6 and Yvon Houde fordrafting, and Francine Fallara for providing Figure 2.We are particularly gratefirl to Greg Lynch, NormandTass6, and two anonymous reviewers for their criticalreview of the fust draft of the manuscript. Editorialsuggestions by Robert F. Martin have helped inclarifying the text.

Rmmnqcrs

ANDERSoN, G.M. (1975): Precipitation of Mississippi Valley-type ores. Econ. GeoL.70,937-942.

- & Ganvnl, G. (1987): Sulfate - sulfide - carbonateassociation in Mississippi Valley-type lead-zinc deposits.Econ. GeoL.82,482488.

& MAceum{, R.W. (1988): Mississippi Valley-type lead-zinc deposits. Geosciente Canrnn Reprtnt Ser.3,79-90.

Ap:usrnoNc, J.P., LoNcsrAm, F.J. & Hen.r, F.J. (1993):Carbon and oxygen isotope geochemistry of calcite fromthe Jubilee Zn-Pb deposit Cape Breton Island. Can.Mineral.3l,755-766.

BoEHr.IER, R.C., Gnrs, P.S., Mupnav, D.A. & Rvar, R.J.(1989): Carbonate buildups of the Gays River Formation,Lower Carboniferous Windsor Group, Nova Scotia. /nReefs, Canada and Adjacent Area (H.H.J, Geldstzer, N.P.James & G.E. Tebbutt, eds.'). Can. Soc. Petrol. GeoI.,Mem.13,609-621.

BRowN, P.E. (1989): FLINCOR: a microcomputer prognunfor the reduction and investigation offluid inclusion dataAm. Mircral. 7 4. 139U1393.

BunTr, M.D., CHAGNoN, A., CIfl, G., FAr,LARA, F., tlhou&Y., Kovrer, D.J., LAvoIE, D., Peneors, S., Senn-ANronrE, P., SANcsrm, D.F, & Savano, M. (1994): Fluidmigration and mineralization in the Lower WindsorGroup, Nova Scotia. Nova Scotin Dep. Natural Resoarces,8th Aru"tual Rniew of Activities, Program and summaries,9+2,45-57.

CItr, Guo)oANc & Saveno, M.M. (1995): A preliminarymicrothermometric study of the Sugar Camp, YankeeLine, and MacPhails Brook Pb-Zn showings, Cape BretonIsland, Nova Scotta, Geol, Sun. Can., Cun. Res.l995-D,53-58.

Davrs, D.W., hwwsrml, T.K. & Spwcxn, R.J. (1990):Melting behavior of fluid inclusions in laboratory-grownhalite crystals in the systems NaCl-H2O, NaCI-KC1-H2O,NaCl-MgCl2-H2O, and NaCl-CaCl2-H2O. Geochim.C osmochim. Acta 54, 59 1-601.

FALLARA, F. (1995): Pdtrographie, gdochbnie et gttologie del'indice de Pb-7.n de Jabilee, Ile de Cape Breton.M6moire de maltrise, Unive$it6 l,aval, Qudbe.c.

Savano, M.M., LyNcr, G. & PARADIS, S. (1994):Preliminary geological and geochemical results chaxacter-i"ing the mineralization processes in the Jubilee Pb--Zndeposit Cape Breton Islan4 Nova Scotia- Geol. Surv.Can., Cun. Res. 94-), 63-7 l.

Fowr,rn, M.G., Hamml, A.P., MACDoNALD, D.J. &MCMAHoN, P.G. (1993): Geological occurence a:rd geo-chemisty of some oil shows in Nova Scottu Bull. Can,Petrol. Geol. 41, 422436.

TTIE JUBrF:F Zn-Pb DEPOSIT. CAPE BRETON 721

GRAvBs, M.C., IIrN, F.J. & Rurzuall, A. (1990): The geolo-gy ofthe Jubilee zinc-lead deposit, Victory County, CapeBreton Islald Nova Scotia supplementary datz. GeoLSurv. Can., Open-File Rep,22il9.

GuLHaur,rou, N., SzyDrowsrc, N. & Pneor$, B. (1990):Characterization ofhydrocarbon fluid inclusions by infra-red and fluorescence microspectrometry. Mineral. Mag,g.3tL-324.

Havesrn, K., Sucaxr, A. & KnAKAZE, A. (1990): Solubilityof sphalerite in aqueous sulfide solutions at temperaturesbetwe€n 25 and 24O'C. Geochim. Cosmochim. Acta 54.71,5-725.

HEnr, F.J., Gnavrs, M.C. & Rurruar, A. (1988): Geology ofthe Jubilee zinc-lead deposi! Victory County, CapeBreton Island, Nova Scotia- Geol. Surv. Can, Open-FileReo.1891.

& - (1993): The Jubilee Zn-Pbdeposit Nova Scotia: the role of synsedimentary faults.Geol. Sun. Can., Pap.9l-9,49-69.

I{rraraaN, M.W. & Lencr, D. (1986): A review and classifi-cation ofthe kish carbonate-hosted base metal deposits. /nGeology and Genesis of Mineral Deposits in keland (C.J.Andrew, R.W.A. Crowe, S. Finlay, W.M. Pennell & J.F.Bne, eds.). kish Association of Economic Geologists,Dublin, heland QlI -238).

Ho*ru, R.D. & BARss, M.S. (1975): Upper Paleozoic rocks ofthe Atlantic hovinces, Gulf of St Lawrence, and adjacentcontinental shelf. Geol. Sarv. Can., Pap,74-30, 35-50.

KHoRASANI, G.K. (1987): Novel development in fluorescencernicroscopy of complex organic mixtures: application inpetroleum geochemistry. Org. Geochem. 11, 157-168.

Mcl-naers, R.K (1987): The application of fluid inclusionsto migration of oil and diagenesis in petroleum reservoirs.Appl. Geochem. 2, 585-603.

Nann, W. & BuRRUss, R.C. (1984): Origin of reservoir frac-tures in Little Knife field" North Dakota. Am" Assoc.Petrol. Geol. BuIl. 68. 1087-1 100.

Oexrs, C.S., Bopra& R.J. & SnaoNsox, J.M. (1990): Thesystem NaCl-CaCl2-H2O. I. The ice liquidus at I atmtotal pressure. Geochim Cosmochim. Acta 54,603-610.

Panaors, S., Savanp, M.M. & Far,r,ana, F. (1993):heliminary study on diagenesis and mineralization of theJubilee Pb-Zn deposi! Nova Scotta. GeoI. Sarv. Can.,Curr. Res. 93-lD, 1ll-119.

Revmqrunsr, C.E., ReyNoIDs, P.H., Zm,rru:-t, M., KRUEGE&H.W. & Blnvrnsop, J. (1989): Formation ofCarboniferous Pb-Zn and.barite mineralization frombasin-derived fluids. Nova Scotia. Canada. Econ. Geol.a. l47t-1488.

RosnnER, E. (1984): Fluid inclusions. Rev. Mineral. 12.

Sarcsren, D.F., Nowux, G.S. & McCnacrnt, A.D. (1994):Thermal comparison of Mississippi Valley-Typelead-zinc deposits and their host rocks using fluid inclu-sion and conodont color alteration tndex data. Econ. Geol.89.493-514.

Spnans, C.S. & HeyL, A.V. (1993): Organic matier @itumenand other forms) as the key to localization of MississippiValley-type ores. /z Bitumens in Ore Deposits (J. Pamell,H. Kucha & P, Lardais, eds.). Springer-Verlag, Berlin,Germany (381-398).

Srewenr, E.B. (1978): A Stady of the Lead-ZincMineralization al Jubilee, Victoria County, Nova Scotia.M.Sc. thesis, Acadia Univ., Wolfuille, Nova Scotia.

Svmrersrv, D.A. (1981): The origin of a Mississippi Valley-t,?e deposit in the Viburnum Trend southeast Missouri.Econ Geol. 7 6. 1848-187 2.

Warcgrwnz, F., PAcEL, M., MEvER, A., MALUSK, H. &MoNm, P. (1990): Thermo-chronological approach toreservoir diagenesis in the offshore Angola basin: a fluidinclusion, aoAr-3eAr and K-Ar investigation. Am. Assoc.PetroL Geol. Bull. 7 4. 547 -563.

Znerc, Yr-GeNc & Fnarrz, J.D. (1987): Determination ofthe homogenization tempenrtures and densities of super-critical fluids in the systen NaCl-KC1{aCl2-H2O usingsynthetic fluid inclusions. Chem. Geol. @,335-350.

Received. Aagust j, 1994, revised manuscript acceptedMarch 9, 1995.