Magmatic Sulfide Deposits
in Mafic Layered Intrusions
Jim Miller
GEOL 5100 – Mafic Layered Intrusions
PGE-dominant
Deposits
Ni-Cu Sulfidedominant
Deposits
Two Major
Groups of
Magmatic
Sulfide
Deposits
Naldrett, 2010
Ni-Cu Sulfide Deposits
STAGES IN THE LIFE OF A MAGMATIC SULFIDE DEPOSIT
Naldrett, 2010
Ni-Cu Sulfide Deposits
Partial Melting of the Mantle
Adiabatic Rise of Magmas
Amount of metals taken up by the
magma depends on degree of melting
SCSS (sulfide concentration at sulfide
saturation) increases with decreasing
pressure resulting in sulfide-undersaturated
magmas in the upper crust
Normal Range of
Mantle Melting
Crust
Mantle
Naldrett, 2010
Mavrogenes and O’Neill, 2010
Ni-Cu Sulfide Deposits
Contamination by sulfur-bearing
country rocks is CRITICAL to
formation of magmatic sulfide.
Other factors lowering the sulfide carrying
capacity of magma, thus promoting sulfide
liquation:
• Increased Si contamination
• Decreased Fe content
• Oxidation
• Decreased Temperature
Mavrogenes and O’Neill, 2010
Lescher and
Barnes, 2009
Ni-Cu Sulfide Deposits
Metal Tenor of Sulfides controlled by
R-factor = Wt% silicate magma/Wt% sulfide liquid
and Recharge leading to Upgrading
Naldrett, 2010
Li, 2009
Dominant Mineralogy
of Magmatic
Cu-Ni Sulfide Deposits
Po - Pyrrhotite – FeS1-x
Cp - Chalcopyrite - CuFeS2
Pn - Pentlandite - (Fe,Ni)9S8
Cb - Cubanite – CuFe2S3
Tk - Talnahkite – Cu9(Fe,Ni)8S16
Bn - Bornite - Cu5FeS4
Cc - Chalcocite - Cu2S
Co - Cobaltite - CoAsS
Platinum
Group
Elements
(PGE)
Platinum Group
Minerals (PGM)
Metal Alloys or
PGEs complexed
with Bi, As, Sb,
Sn, Pb, Te,
IPGEs
Follows Ni
PPGEs
Follows Cu
Precious Metal Minerals
PMM Name
Formula
Total #
Sulfide Host Mineral
Total PMM
In Sulfide
cp
pn
cb
po
tn
bn
Kotulskite
Pd(Bi,Te)1-2
15
8
8
0
0
0
0
0
Froodite
PdBi2
11
10
3
6
1
0
0
0
Naldrettite
Pd2Sb
3
3
3
0
0
0
0
0
Paolovite
Pd2Sn
83
68
45
10
7
4
1
1
Sobolevskite
PdBi
2
2
1
0
0
0
1
0
Sperrylite
PtAs2
26
22
13
5
3
1
0
0
Stibiopalladinite
Pd5Sb2
11
5
4
1
0
0
0
0
Taimyrite
(Pd,Pt,Cu)3Sn
2
2
2
0
0
0
0
0
Telluropalladinite
Pd9Te4
1
1
1
0
0
0
0
0
93
68
31
24
3
4
3
3
Undetermined PGM
Silver sulfide
AgS
16
11
7
3
1
0
0
0
Empressite
AgTe
2
2
1
0
0
1
0
0
Hessite
Ag2Te
3
3
1
1
1
0
0
0
Electrum
AuAg
62
22
12
3
3
3
1
0
Gold
Au
17
7
3
1
0
3
0
0
347
234
135
54
19
16
6
4
67%
57%
23%
8%
7%
3%
2%
TOTALS
%
PMM study of NorthMet ore, Cervin, 2011
Ni-Cu Sulfide Deposits
Fractionation of Sulfide Liquid
MSS –mono-sulfide
solution (Fe,NiS)
With IPGEs
Exsolves to Po + Pn
Kullerud (1976)
ISS : intermediate
sulfide solution
(Fe,CuS)
Exsolves to Cp-Cb
Holwell (2010)
Types of Ni-Cu Sulfide Deposits
Naldrett, 2010
Eckstrand and Hulbert, 2007
Types of Ni-Cu Sulfide Deposits
Naldrett, 2010
Li, 2009
Types of Ni-Cu Sulfide Deposits
Naldrett, 2010
Oovoid Ore Body, Voisey’s Bay
Types of Ni-Cu Sulfide Deposits
Types of Ni-Cu Sulfide Deposits
Eckstrand and Hulbert, 2007
Li, 2009
Types of Ni-Cu Sulfide Deposits
Duke Island
from Ripley, 2009
PGE-dominant Deposits
PGE-dominant Deposits
PGE-dominant Deposits
Comparison of Attributes of Skaergaard-type and Classic PGE Reefs
Skaergaard-type PGE Reefs
Classic PGE Reefs
Tectonic Setting
Plume-influenced continental rifts, occur as
subvolcanic intrusions
Unclear, occur as large, isolated intrusions within
Precambrian cratons
Age
Mesoproterozoic and younger
Neoarchean to Paleoproterozoic
Parent Magma
Aluminous, olivine tholeiite (E-MORB)
High-Cr/Mg/Si boninite/komatiite (U-type) with
aluminous tholeiite (A-type)
Host Rock
Gabbroic to ferrogabbroic cumulates
(Pl+CpxOxOl); some associated with
layering.
Pyroxenitic to noritic cumulates; locally associated
with chromitite layers, early anorthositic
cumulates, and pegmatite.
Sulfide Composition
of Mineralized Intervals
Cu/Ni >100 (closed systems)
Cu/Ni = 0.3-5.0 (open systems)
Precious Metal Ratios
of Mineralized Intervals
Pt/Pd = 7 – 0.1
Pt/Pd = 2.5 - 0.2
Pt+Pd/Au = 1 - 10
Pt+Pd/Au > 10
Stratigraphic Distribution of
1
Peak Concentrations
Pt / Pd  Au
Pd / Pt / Au
Pt + Pd  Cu (Ni) Au
Pt + Pd / Ni  Cu  Au
Examples
Closed systems - Skaergaard, Sonju
Intrusion, New Haven diabase
( below,  coincident with, / or)
Cu/Ni >1 (open systems)
Lake
Open systems- Layered Series at Duluth,
Kap Edvard Holm Complex, Lake Owen
Intrusion, Freetown Complex, Muskox
Intrusion, Rincón del Tigre Complex
Bushveld Complex, Stillwater Complex, Great
Dyke, Munni Munni Complex, Jimberlana
Intrusion, Penikat, Portimo and other Fennoscandian intrusions, Rum Intrusion, Muskox
Intrusion, Rincón del Tigre Complex
Based on data from this study; Arnason and Bird, 2000; Prendergast, 2000; Andersen et al., 1998; Lee, 1996; Bird et al., 1995; Barnes and Francis, 1995;
Barnes et al., 1990; Gottfried et al., 1990; Naldrett and Wilson, 1990; Naldrett, 1989b.
PGE-dominant Deposits
PGE-dominant Deposits
Classic PGE reefs involve a mix of ultramafic (U-type)
and tholeiitic (T-type) magmas. Reef occurrences
commonly occur near the mixed interface.
Mineral Norms of
Parental Magmas
Naldrett, 2010
PGE-dominant Deposits
Naldrett, Li, Mungall, Barnes, Maier, ....
Boudreau
PGE-dominant Deposits
Hydromagmatic Model of Boudreau
Boudreau, 2009
PGE-dominant Deposits
The Cu/Pd Ratio
A monitor of sulfide saturation
DPd (Sulf/Sil) = ≥ 105
DCu (Sulf/Sil) = 500-1000
DNi (Sulf/Sil) = 300-500
DNi (Ol/Sil) = 2-15
--Pt+Pd
--Cu
--Ni
PGE-dominant Deposits
Metal Offsets
PGE-dominant Deposits
Metal Offsets
Kinetic Model (Mungall, 2002)
Partitioning controlled more by
kinetic effects rather than
equilibrium
Effective R-factor proportional to
diffusivity of metal in silicate melt
Other factors:
• Size of the sulfide droplets
• Duration of that sulfide is in
contact with silicate
• Viscosity of silicate magma
PGE-dominant Deposits
Dsulf/sil~105
Dsulf/sil~102
PGE-dominant Deposits
Bushveld Complex
PGE-dominant Deposits
Bushveld Complex
PGE-dominant Deposits
Bushveld Complex
PGE-dominant Deposits
Stillwater Complex, Montana
- JM Reef
Li et al., 2010
PGE-dominant Deposits
Stillwater Complex, Montana
Cooper, 2009
PGE-dominant Deposits
Great Dyke, Zimbabwe
Barnes and Maier, 2010
PGE-dominant Deposits
Great Dyke, Zimbabwe
Li et al., 2010
PGE-dominant
Deposits
Munni Munni Intrusion
Western Australia
FennoScandian
Intrusions
Finnish PGE Reefs
SJ
Reef