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7 Cards in this Set
- Front
- Back
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Grade & Tonnage |
Tonnage - mostly >10Mt Grade - mostly >!wt% |
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Ore Minerals |
Ni - pentlandite (Fe, Ni)9S8, ~34% Ni, forms solid solution with pyrrhotite so always found together (monosulfide solid solution - MSS)
Cu - chalcopyrite (CuFeS2), ~33% Cu, forms intermediate solid solution with pyrrhotite (ISS) |
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Ore Textures |
- interstitial/disseminated - triangle ore - globules - net/matrix - massive - stratiform occurances - breccia - zonation |
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Sudbury Complex |
1. meteorite impact, caused flash melting of the crust - evidence of meteorite impact: - strange basin shape, breccia of host rock spread over large area, full of iriduim, presence of glass as matrix
2. feeder conduits to high level intrusions or continental flood basalt - small intrusions in thick crust komatiite (spinifex texture)
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Genesis (1) |
Source of Ni (enriched) - mantle? - bulk earth has 18% Ni but is concentrated in core and depleted from crust - need a mantle source for melt |
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Genesis (2) |
Melting (specific conditions) - in peridotites Ni is partitioned between sulfide alloy + olv - Ni needs a high degree of PM to release it form the Olv in mantle rocks - less partial melting is needed for less compatible elements, more melting dilutes concentration - need melting of large amount of mantle rocks |
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Genesis (3) |
Magma ascending (rapid without fractionation) - requires minimal crystallisation of olv and segregation of sulfide melt - if temp decrease before emplacement, olv will take out all NI (5% crys. removes 15%Ni) - sulfide melt will take away Ni, Cu + PGE (5% fractionation will remove 27% Ni) - need good, clear conduct - hence associated with rift environments) |
