cm7_663
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TEMPERATURESF FORi,IATIONOF THE CHISEI AKE
sutpHtDEDEPOS|T,NOW [AKE, MANTTOBA
A. E. BENCEercD . C. COLEMAN
tln iaer ity of Sashatchezaan,os atoon,Saskatchaaan
During the winter of 1961-62a study was madeof the ore mineralogyof the chisel Lake Mine by A. E. Benceworking under the supervision
of L. c. coleman.This mine s located n centralManitoba at 84"b0,N.Lat., 100007/ w. Long. specimensfor this work were provided by theHudsonBay Mining and SmeltingCompany.
The sulphides: arsenopyrite, pyrite, sphalerite, chalcopyrite, galena,pyrrhotite, gudmundite, marcasite, and the sulphosalts: meneghinite,tetrahedrite, and a bournonite-seligmannite olid solution, wereobservedas well as small amounts of native gold.
on the basisof textural relationships he following generalsequence fevents for the formation of the metallic componentsof the ore body ispostulated: the crystallization of arsenopyritefollowed by deformation;crystallizationof pyrite;introductionof gold; crystallizationofpyrrhotite,sphalerite, and chalcopyrite, generally in that order but with somereversals and overlapping relationships; fracturing followed by theemplacementof galena, the sulphosalts, gudmundite, and pyrite; andfinally, the formation of marcasiteby the alteration of pyrrhotite.
Two geothermometerswere employed to determine emperatures offormation. Thesewere the FeS-ZnSgeothermometerof Kullerud (lgbg)
and skinner & Barton (195s) and the pyrrhotite geothermometei ofArnold (1962).
All measurementswere made with a Norelco wide angle diffracto-meter using filtered cu radiation for the sphalerite samples and Feradiation for the pyrrhotite samples.An external silicon standard wasemployed and the 2g values measuredare believed to be accurate to+0.005'. corrections for Mns and cdSx in solid solution in sphaleritewere made basedon the curves of coleman (19b7).The amounts of coand Ni* present in the pyrrhotite are less than 400 p.p.m. and
theireffectson the unit cell dimensionsare negligible.
.*Yr and
9d.analyses-of so,haleriteand co and Ni analysesof pyrrhotite were doneby Dr. R. G. Arnold of the saskatchewan Research council uriig r-rt-fluorescencetechniques.
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664 THE CANADIAN MINERALOGIST
Sphalerites rom fourteenspecimenswereanalyzed.Thesesampleshad
been taken at regular intervals along the plunge of the orebody to see f
a temperature gradient existed during its formation.
The correctedunit cell dimensiotr" t.bl" 1) vary from 5.4131A to5.4158A which indicate FeS contents of the sphaleritesranging from
about 8.4-14.3 mol/s. Using data from Kullerud (1953)' a range of
minimum temperaturesof formation of the sphaleritewas determinedas
having beenfrom 275" C. to 425"C.
T"tt" 1. T""""-"tt*a""
F.
MnS and
Sample Meas"red Wl % Wt.To CdS Correqted" N;:* - oo Ai - 'Mir6" caS" correction oo (A)
Minimum
Mol Vo formationFeS Temp. "C.
234o6a
8I
10t l7213L4
5.4153 .675.4140 .695.4160 .405.4157 .275.4160 .595.4151 .485.4157 .295.4163 .485.4161 .295.4140 .48
6.41,45 .545.4161 .735.4152 .735.4135 .36
.08 -.0006
.13 - .0007
.10 - .0004
.L4 -.0003
.13 - .0006
.12 -.0005
.17 - .0003
. r2 - .0005
.L7 - .0003
.13 -.0005
.L2 - .0005.14 - .0007
.17 - .0007
.t7 - .0004
5.4L47 11.855.4133 8.805.4156 13.805.4154 13.356.4154 13.355.4t46 11.605.4154 13.355.4158 74.255.4158 14.256.4135 9.20
5.4140 10.305.4154 13.355.4145 11.405.4131 8.35
3702854L5405405360405425425300
330405360275
Pyrrhotite from two specimenswas analysed n the present study and
d(l}z) spacingsof 2.05-65 and 2.0558A w"r" measured (Table 2)'
These indicate pyrrhotite compositions containing about 46.5 atomic
percent metals and a temperature of formation for the pyrrhotite from
toth specimensof 510+10' C. This is a minimum tempefature offormation but, since n both specimenshe pyrrhotite is closelyassociated
with pyrite, the results are probably very close o the true temperature
of formation.
Tenr-B 2. TsMrsRAruREs op FotuetroN oF Pvnnsortrp
Sample - d'(l}Z)a - Atomic % lemperature of
Nd. Angsirom units metals formation oC'
13 2.0565 46.50 510
The results of this work suggest he following possibilities: first, that
either a temperature gradient existed during the formation of the
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CEISEL LAKE SULPEIDE DEPOSIT 6 6 5
sphalerite or that there was a time-space relationship for sphaleriteformation, and second hat the temperatureof formation of the pyrrhotitewas higher than that of the sphalerite and that, therefore, the physical
conditions were changing during the formation of the deposit.The Fes content of the sphalerites as determined by the unit celldimensionsappears o be a function of the distance from the margins ofthe ore body (Table 1, Fig. 1). This feature could be accounted or if
GLACIAL
o tt":::
\ i,1ffi\ ,. \.1;z\ :i,\ !i .iii
i . f i !. /1 i i
.i".j/t' .i li fi'i.,+ |,iiii "/..1g,"r'1,
E--?i':/MARGINOF OREBODY
SPHALERITEISOTHERMS--35O...-
gAlAUEBrr_EAMPLE JLOCATIONS
LOIIGITUDINAL SECTION
CHISEL LAKE M|NE
LOOKING N.67OE.
SCALE: t INCH32Oo FEET
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666 THE CANADIAN MINERALOGIST
the deposit had formed as the result of hydrothermal solutions which
were introduced along some"channelway" located near its centre and if
such introduction had createda thermal gradient diminishing outwards
from the locus of introduction. An alternative explanation is that theformation of sphalerite extended over a period of time during which
temperatures in the region were progressively changing. In this case,
sphalerite tourard the centre of the orebody would, presumably, have
been formed earliest and the formation of sphalerite would have pro-
gressedoutwards, with time, towards the margins of the deposit.
This study has shown that the pyrrhotite formed at a higher temper-
ature than the sphalerite.On this basis,assumingwhat is considered he
normal sequenceofevents (i.e. decreasing emperature with time), the
pyrrhotite formed earlier than the sphalerite.Age relationshipsof these
minerals deduced rom textural evidencesupport this idea.
RrrBnBNcss
AnnolD, R. G. (1962): Equilibrium reliationsbetween pyrrhotite and pyrite from 325"
to 743oC., Econ. GeoI., 57, 72-90.Cor-sMeN,L. C. (1957): Mineralogy of the Giant Yellowknife gold mine, Yellowknife,
N.W.T.. Econ.Geol'., ,400-42,5.
Kwr-rnr,o, G. (1952) Fe$ZnS system, a geological hermometer, Nmsh. GeoI.T'id'sshr,,32.6L-t47.
SKTNNTR, , J., & BAnroN, P. B., Jn. (1958): Recent work on sphalerite, its.bearing on
the sphaierite geothermometer (abstr.), Geol',Soc. Amerha Bul'|,., 69, L768.
Manuscribt rece'fuedctober 6, 1962