Transcript Magmatic Ni-Cu-PGE deposits

Magmatic Ni-Cu-PGE-Cr
Deposits
Distribution of Magmatic Sulphide Deposits
Norilsk
Sudbury
Bushveld
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
Meteorite Impact Origin of the Sudbury Complex
Sudbury
Stratigraphy
Airborne debris
Onaping
Impact
Stratigraphy
Ejecta
Breccia
Melt
Sulphide concentrations
Onaping formation
Partial
melting
Sublayer
Onaping formation
Sudbury
Irruptive
Sublayer
Sudbury Footwall-Type Deposit
Sudbury Ni-Cu Ores
Inclusion Ore
Pyrrhotite-chalcopyrite
and peridotite inclusions
Chalcopyrite
Pyrrhotite
Pentlandite
Massive Ore
Pyrrhotite
Pentlandite (Fe,Ni)9S8
The Billiard Ball Model of Magmatic Sulphide
Textures (Naldrett, 1969)
Fraser and Strathcona Mines Cross-Section
Footwall Ores
Chalcopyrite sill with
alteration halo cuts off
mafic dyke. High PGE
into host gneiss
Pyrrhotite- and
chalcopyrite-dominated
veins in footwall gneiss
Oxygen/Sulphur Fugacity and FeO Controls
on Sulphur solubility in Silicate Melts
1300 oC
975 oC
Sulphur dissolves H2S at low
fO2 and as SO2 at high fO2
Wt.% Metal in Silicate Liquid
Metal partitioning between Sulphide and
Silicate Melts
Wt.% Metal in Sulphide Liquid
The Norilsk Ni-Cu Deposit
A Model for the Norilsk Deposit
Magma saturates
in sulphide due to
decrease in fO2
Flood basalts
Gabbro sill
Sulphide
Gabbro sill
Sulphide
Coal-bearing sediments
Evaporites
Limestones
Gabbroic magma
Limestones
Coal-bearing sediments
Limestones
Magma dissolves
high concentration
of sulphur
Limestones
Evaporites
Bushveld Igneous Complex
Bushveld Stratigraphy
Merensky Reef
Gabbroic anorthosite
Critical Zone
Chromitite
Anorthosite
Lower Zone
Pyroxenite
Harzburgite
Controls on the Formation of
Chromitite Layers
Assimilation
of silica-rich
sediments
Magma mixing
Merensky Reef
Chromite
Anorthosite
Merensky Reef
Pyrrhotite + PGE minerals
The Role of Convection, Crystal Settling and
Repeated Magma Injection in the Bushveld
A Model for the Emplacement of the
Bushveld Complex