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Magmatic Ni-Cu-PGE-Cr Deposits. Distribution of Magmatic Sulphide Deposits Bushveld Sudbury Norilsk.

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Presentation on theme: "Magmatic Ni-Cu-PGE-Cr Deposits. Distribution of Magmatic Sulphide Deposits Bushveld Sudbury Norilsk."— Presentation transcript:

1 Magmatic Ni-Cu-PGE-Cr Deposits

2 Distribution of Magmatic Sulphide Deposits Bushveld Sudbury Norilsk

3 Magmatic Sulphide Ore (Pyrrhotite and subordinate pentlandite (Fe,Ni) 8 S 9 )

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

10 Sudbury Footwall-Type Deposit

11 Sudbury Ni-Cu Ores Pyrrhotite-chalcopyrite and peridotite inclusions Massive Ore Inclusion Ore Pyrrhotite Pentlandite (Fe,Ni) 9 S 8 Pentlandite Pyrrhotite Chalcopyrite

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

13 Fraser and Strathcona Mines Cross-Section

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

15 Oxygen/Sulphur Fugacity and FeO Controls on Sulphur solubility in Silicate Melts Sulphur dissolves H 2 S at low fO 2 and as SO 2 at high fO o C 975 o C

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 fO 2 Gabbroic magma

19 Bushveld Igneous Complex

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

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

22 Merensky Reef Anorthosite Merensky Reef 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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