Magmatic Ni-Cu-PGE-Cr Deposits

Distribution of Magmatic Sulphide Deposits

Bushveld

Sudbury

Norilsk

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

Ni Grades and Tonnages

Cu Grades and Tonnages

PGE Grades and Tonnages

Geology of the Sudbury Complex

Evidence of Meteorite Impact

Onaping fallback breccia

Shatter cones

Granophyre - impact melt

Airborne debrisOnaping

Ejecta

Breccia

Melt

Sulphide concentrations

Onaping formation

Onaping formation

Partialmelting

SublayerSublayer

Sudbury

Irruptive

Meteorite Impact Origin of the Sudbury Complex

Impact Stratigraphy

Sudbury Stratigraphy

Sudbury Footwall-Type Deposit

Sudbury Ni-Cu Ores

Pyrrhotite-chalcopyriteand peridotite inclusions

Massive Ore

Inclusion Ore

PyrrhotitePentlandite (Fe,Ni)9S8

Pentlandite

Pyrrhotite

Chalcopyrite

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

Fraser and Strathcona Mines Cross-Section

Pyrrhotite- and chalcopyrite-dominated veins in footwall gneiss

Footwall Ores

Chalcopyrite sill with alteration halo cuts off mafic dyke. High PGE into host gneiss

Oxygen/Sulphur Fugacity and FeO Controls on Sulphur solubility in Silicate Melts

Sulphur dissolves H2S at lowfO2 and as SO2 at high fO2

1300 oC

975 oC

Metal partitioning between Sulphide and Silicate Melts

Wt.%

Met

al i

n S

ilica

te L

iqui

d

Wt.% Metal in Sulphide Liquid

The Norilsk Ni-Cu Deposit

A Model for the Norilsk Deposit

Flood basalts

Gabbro sillGabbro sill

Coal-bearing sediments Coal-bearing sediments

Sulphide Sulphide

Limestones

LimestonesLimestones

Limestones

Evaporites EvaporitesMagma dissolves high concentration of sulphur

Magma saturates in sulphide due to decrease in fO2

Ga

bbr

oic

mag

ma

Bushveld Igneous Complex

Bushveld Stratigraphy

Anorthosite

Chromitite

Merensky Reef

Gabbroic anorthosite

Lower Zone

Harzburgite

Pyroxenite

Critical Zone

Controls on the Formation of Chromitite Layers

Magma mixing

Assimilation of silica-rich sediments

Merensky Reef

Anorthosite

Merensky Reef

Pyrrhotite + PGE minerals

Chromite

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

A Model for the Emplacement of the Bushveld Complex