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Magmatic Ni-Cu-PGE-Cr Deposits

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Presentation on theme: "Magmatic Ni-Cu-PGE-Cr Deposits"— Presentation transcript:

1 Magmatic Ni-Cu-PGE-Cr Deposits

2 Distribution of Magmatic Sulphide Deposits
Norilsk Sudbury Bushveld

3 Magmatic Sulphide Ore (Pyrrhotite and subordinate pentlandite (Fe,Ni)8S9)

4 Ni Grades and Tonnages

5 Cu Grades and Tonnages

6 PGE Grades and Tonnages

7 Geology of the Sudbury Complex

8 Evidence of Meteorite Impact
Onaping fallback breccia Shatter cones Granophyre - impact melt

9 Meteorite Impact Origin of the Sudbury Complex
Airborne debris Onaping Ejecta Breccia Melt Sulphide concentrations Onaping formation Partial melting Sublayer Sudbury Irruptive Impact Stratigraphy Sudbury Stratigraphy

10 Sudbury Footwall-Type Deposit

11 Sudbury Ni-Cu Ores Inclusion Ore Massive Ore Pyrrhotite-chalcopyrite
and peridotite inclusions Chalcopyrite Pyrrhotite Pentlandite Massive Ore Pyrrhotite Pentlandite (Fe,Ni)9S8

12 The Billiard Ball Model of Magmatic Sulphide Textures (Naldrett, 1969)

13 Fraser and Strathcona Mines Cross-Section

14 Footwall Ores Chalcopyrite sill with alteration halo cuts off mafic dyke. High PGE into host gneiss Pyrrhotite- and chalcopyrite-dominated veins in footwall gneiss

15 Oxygen/Sulphur Fugacity and FeO Controls on Sulphur solubility in Silicate Melts
Sulphur dissolves H2S at low fO2 and as SO2 at high fO2

16 Metal partitioning between Sulphide and Silicate Melts
Wt.% Metal in Silicate Liquid Wt.% Metal in Sulphide Liquid

17 The Norilsk Ni-Cu Deposit

18 A Model for the Norilsk Deposit
Flood basalts Gabbro sill Coal-bearing sediments Sulphide Limestones Evaporites Magma dissolves high concentration of sulphur Magma saturates in sulphide due to decrease in fO2 Gabbroic magma

19 Bushveld Igneous Complex

20 Bushveld Stratigraphy
Merensky Reef Gabbroic anorthosite Critical Zone Chromitite Anorthosite Lower Zone Pyroxenite Harzburgite

21 Controls on the Formation of Chromitite Layers
Magma mixing Assimilation of silica-rich sediments

22 Merensky Reef Anorthosite Merensky Reef Chromite
Pyrrhotite + PGE minerals Chromite

23 The Role of Convection, Crystal Settling and Repeated Magma Injection in the Bushveld

24 A Model for the Emplacement of the Bushveld Complex

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