Yuan Chen

Date of Award


Degree Type


Degree Name

Doctor of Philosophy


Platinum-group minerals (PGMs) and native gold are reported in association with gersdorffite and nickeline from the Thompson mine, Thompson Nickel Belt, Manitoba. Four PGM-gold bearing ore types are distinguished on the basis of mineral assemblages and host rocks: (I) irarsite in massive Ni sulfide ore hosted by metapelite; (II) gold, sudburyite, testibiopalladite-antimonian michenerite, unnamed PGM, and merenskyite in As-rich Ni sulfide ore hosted by metapelite from the T-1 mine; (III) gold with tellurides in As-rich Ni sulfide ore hosted by metapelite from the open pit; and (IV) gold, majakite, kotulskite, merenskyite, and michenerite in As-rich Ni sulfide ore hosted by pegmatite from the T-1 mine. Native gold is argentian (Ag{dollar}\sb{lcub}22{rcub}{dollar}-Ag{dollar}\sb{lcub}32{rcub}{dollar}), and most Ag-rich in pegmatite-hosted samples. Testibiopalladite compositions straddle the previously inferred miscibility gap with michenerite. The unnamed PGM has a composition of (Pd,Ni){dollar}\sb{lcub}0.44{rcub}{dollar}(Te,Sb){dollar}\sb{lcub}0.56{rcub}{dollar}, and is distinctly anisotropic. Sporadic, minor amounts of PGEs are present in gersdorffite and nickeline.;All ore types are associated with a pervasive hydrothermal alteration event that post-dates the regional amphibolite facies metamorphism (presently constrained around 600-700{dollar}\sp\circ{dollar}C and 6-7 kbar). The alteration assemblages include: (1) biotite, muscovite, chlorite, albite, calcite, siderite, allanite, quartz and sulfide (mainly pyrite, violarite and chalcopyrite) in metapelite; (2) secondary grunerite and ferropyrosmalite in silicate-facies banded iron formation; (3) serpentine, tremolite, chlorite, epidote-zoisite and prehnite in skarn; (4) Fe-rich talc, serpentine, chlorite, actinolite, and hisingerite in ultramafic rocks. Spinel in metapelite and ultramafic rocks has been modified by Cr-Zn-rich fluids, and the oscillatory zonation in its composition reflects fluctuation in fluid composition. The latest hydrothermal alteration is characterized by high Cl concentrations, indicated by Cl-bearing allanite and ferropyrosmalite (up to 5.0 wt% Cl). The chlorite geothermometer and muscovite geobarometer suggest that the PGE-Au mineralization occurred at 250-300{dollar}\sp\circ{dollar}C, 3-4 kbar.;PGMs and gold presently reported from the Sudbury mining camp include michenerite and merenskyite at the Lindsley mine, and sperrylite, michenerite, merenskyite, Pd-melonite, and electrum at the Lockerby mine. At the Dundonald Beach exploration property, Ontario, electrum, Os-Ni-Fe alloy, froodite, and an unnamed PGM phase (Pd-Sb-Bi) occur in komatiite. The alteration assemblages in these deposits also favour the possible involvement of hydrothermal fluids in the PGE-Au mineralization.;Investigation of the partitioning of Ni between olivine and Fe-Ni monosulfide reveals that the Fe/Ni distribution coefficient (K{dollar}\sb{lcub}\rm D3{rcub}{dollar}) is in the range 4-15 at the Whistle, Levack, Trillabelle, and Ministic Lake mines of the Sudbury mining camp. However, K{dollar}\sb{lcub}\rm D3{rcub}{dollar}, values are somewhat higher (17-20) for the Thompson mine peridotite. These results are consistent with literature observations that K{dollar}\sb{lcub}\rm D3{rcub}{dollar} is generally significantly lower than the value (of 30-35) for equilibration of sulfide and olivine under magmatic conditions, but increases toward the high-temperature experimental value with increasing metamorphic grade. The komatiite from the Dundonald Beach property gave a K{dollar}\sb{lcub}\rm D3{rcub}{dollar} value of 26, which could be attributed to either hydrothermal alteration of Fe-Ni sulfide, giving Ni-enriched sulfides, or equilibrium of primary (magmatic) sulfides with olivine.



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