|
|
 |
|||||||||||||||||
|
|||||||||||||||||
 |
|||||||||||||||||
| JOURNAL HOME | HELP | CONTACT PUBLISHER | SUBSCRIBE | ARCHIVE | SEARCH | TABLE OF CONTENTS |
Department of Geology, University of Toronto, 22 Russell
Street
Toronto, Ontario, M5S 3B1, Canada
E-mail:
mungall{at}geology.utoronto.ca
Department of Geology, University of Toronto, 22 Russell
Street
Toronto, Ontario, M5S 3B1, Canada
 |
ABSTRACT |
|---|
 TOP ABSTRACT INTRODUCTIONORE DEPOSIT MODELSPGE MINERALIZATION OF THE...FUTURE OUTLOOKREFERENCES |
|---|
KEYWORDS: platinum-group elements, ore deposits, chromite, sulfide, Bushveld Complex
|
INTRODUCTION |
|---|
|
TOPABSTRACTINTRODUCTIONORE DEPOSIT MODELSPGE MINERALIZATION OF THE...FUTURE OUTLOOKREFERENCES |
|---|
|
|
At equilibrium, the concentration of all of the PGE is at least 10,000 times higher in sulfide melt than in coexisting silicate melt, making sulfide an extremely potent agent for the collection and segregation of PGE from magmas in which each PGE normally occurs at concentrations less than 15 ppb (Fleet et al. 1999; Arndt et al. 2005). The extreme enrichment of PGE in sulfide liquid with respect to coexisting silicate melt is a consequence of the preference shown by the PGE for covalent bonding with sulfide ions in sulfide melt over the more ionic character of the bonds formed with oxygen ions in silicate melts. The processes controlling the formation of PGE deposits are therefore inextricably tied to the igneous geochemistry of sulfur.
In most common mantle-derived magmas, sulfur exists as S2- ions, which dissolve in common silicate melts primarily by forming FeS complexes in which sulfur replaces oxygen in the more common FeO melt species. The sulfur concentration at sulfide saturation in a basaltic melt is increased by increasing temperature and FeO content and decreased by increasing pressure (Wendlandt 1982; Mavrogenes and O'Neill 1999).
Sulfur geochemistry controls the genesis of PGE deposits in two principal ways: first, the presence of sulfide as a restite phase during mantle melting limits the availability of PGE to magmas; and second, the formation of an ore deposit requires the saturation of a magma with immiscible sulfide liquid and the collection of that liquid in structural traps within magmatic systems (FIG.2).
|
At the high degrees of melting implicated in the genesis of high-Mg intraplate magmas, including komatiites and picritic flood basalts, all of the sulfur in the mantle is dissolved in the silicate melt prior to magma ascent. In this case, the concentrations of all of the PGE are dictated by mineral-melt partitioning. The IPGE (Os, Ir, Ru) and Rh are mildly compatible with a peridotitic mantle residue, but the PPGE (Pt, Pd) are highly incompatible and therefore are liberated into the silicate melt as soon as the last bit of sulfide has been dissolved (Mungall 2007 and references therein). Alternatively, at oxygen fugacities that are sufficiently high to convert some or all sulfide to sulfate, the net solubility of sulfur in the melt is increased as much as ten fold (Jugo et al. 2005), and any degree of melting of the mantle may permit a mafic magma to form in the absence of a sulfide phase. Magmas formed in the absence of sulfide are fertile potential progenitors of PGE deposits.
Although there are several ways in which PGE-rich magmas may be generated, it appears that all of the major PGE deposits currently known, other than the impact-related deposits of Sudbury, Canada, owe their origins to the formation of intraplate picritic magmas. When these magmas form, the degree of melting is high enough to completely dissolve all the sulfur in their mantle source regions (Arndt et al. 2005; Barnes and Lightfoot 2005).
In order to form a PGE deposit, a fertile magma must become saturated with sulfide melt at a place in the crust where the sulfide can accumulate in a structure that will later be accessible to mining operations. Because primitive fertile magmas must be generated under sulfide-undersaturated conditions and further, because sulfide solubility increases with decreasing pressure, such magmas begin their residence in the crust strongly sulfide undersaturated and hence do not readily produce an immiscible sulfide phase.
Two mechanisms can work, singly or in concert, to provoke sulfide saturation. In the first, because sulfide does not enter any of the common fractionating solid phases in a cooling silicate magma, its concentration increases with progressive cooling and crystallization until the magma eventually reaches sulfide saturation. This might require a large degree of crystallization, so the magma from which sulfide eventually segregates may be as highly evolved as a ferrobasalt. In this case, nucleation of the first immiscible sulfide will be somewhat inhibited due to the large interfacial tension between sulfide and the highly evolved silicate melt. Widely spaced droplets of sulfide will grow by diffusion until they are large enough to settle to the bottom of the magma body; this process can be described as fractional, like a distillation. In a moonshine still, the first fumes to leave contain the highest concentration of those volatile alcohols that are most strongly partitioned into the vapor. Similarly, during fractional removal of sulfide, the first sulfide to fall out will contain the most strongly chalcophile elements. These are the PGE, so the first appearance of sulfide is expected to produce thin layers containing very small amounts of sulfide with extremely high PGE concentrations. Due to the fractional nature of this process, a chromatographic segregation of the chalcophile elements is anticipated as a consequence of the interplay of their partition coefficients and the rate at which each PGE is able to diffuse towards a growing droplet (Mungall 2002). Important examples of deposits that might have formed in this way are the Main Sulfide Zone of the Great Dyke in Zimbabwe and possibly also the Merensky Reef in the Bushveld Intrusion (see ore deposit models below).
The second mechanism that can produce sulfide saturation involves the
assimilation of crustal rocks by the primitive, PGE-rich,
sulfide-undersaturated magma. The addition of a cool assimilant can hasten
sulfide saturation by simultaneously increasing the silica concentration and
decreasing the temperature, both of which conspire to reduce sulfide
solubility. If the assimilant contains crustal sulfur, the system approaches
sulfide saturation even more quickly. The formation of immiscible sulfide by
crustal contamination is implicated in the generation of all
base-metal-dominant magmatic sulfide deposits, but the formation of a PGE-rich
deposit by such means requires a delicate balance to achieve the right amount
of excess sulfide in the resulting mixture. Addition of just enough crustal
sulfur to bring the magma to sulfide saturation can generate small quantities
of sulfide with very high PGE tenors. If the magma is just barely saturated
with sulfide, then the net amount of PGE sequestered in the sulfide is small
compared with the total mass of PGE in the entire system; in such a case the
concentration of PGE in the sulfide approximates the product of the partition
coefficient and the bulk PGE concentration. However, if the amount of sulfide
melt is volumetrically significant, the removal of PGE into the sulfide
diminishes the concentration of PGE in the host silicate magma and hence also
the concentration in the sulfide phase. The greater the degree of sulfide
super-saturation, the higher is the modal abundance of sulfide melt and the
lower the concentration of PGE in both the sulfide and silicate phases. As a
result, the assimilation of a large amount of crustal sulfur will lead to the
segregation of large masses of PGE-poor sulfide melt that may be attractive as
sources of Ni and Cu but will not qualify as PGE deposits. This relationship
is encoded in a widely used equation
(Campbell and Naldrett 1979):
 |
Once sulfide liquid droplets have formed, they must be collected in order to produce an ore deposit. This is facilitated by their high density (about 4.5 g cm-3 versus 2.2 g cm-3 for the silicate melt), which causes the droplets of sulfide to settle to the base of the body of silicate melt. If the sulfide droplets form in a flowing mass of magma in a conduit, they will be entrained and carried in suspension until a change in the flow regime permits them to settle. This process typically occurs where a conduit widens into a larger space, where the flow passes through a portion of the conduit that is choked with unmelted fragments of wall-rock, or both. If the sulfide droplets form in a more quiescent body of magma, such as the liquid portion of a layered intrusion, they can be expected to settle to the bottom. If sulfide liquid begins to segregate in a previously sulfide-undersaturated magma column, then a distinct sulfide-rich layer may form in consequence.
If sulfide droplets accumulate at the base of a melt body in sufficient quantity to form a continuous pool of sulfide melt, they will subsequently undergo a process of magmatic evolution largely or wholly decoupled from the evolution of the parental silicate magma. Although sulfide melt is superheated at magmatic conditions typical of basaltic magmas, a sulfide melt pool will eventually cool to its liquidus temperature and begin to solidify by forming crystals of monosulfide solid solution (mss) or magnetite, or both. Eventually the mss and magnetite are joined on the liquidus by intermediate solid solution (iss; i.e. magmatic cubanite-chalcopyrite solid solution), and during the latest stages of cooling, the sulfide melt may solidify to a variety of phases including pentlandite, millerite, bornite, and a variety of rare copper-sulfide minerals. Platinum, palladium, and gold are rejected by all of these minerals except perhaps pentlandite, with the result that fractionated sulfide melts are highly enriched in these elements compared with the sulfide that initially equilibrated with the silicate magma. As a result, even sulfides that segregate at fairly high sulfide/silicate mass ratios and consequently are not initially very rich in PGE may ultimately generate small volumes of very high-grade PGE mineralization, provided that the residual melts are able to migrate away from the mss-magnetite cumulates. Examples of this kind of PGE mineralization constitute much of the current ore reserves in the Sudbury district, where their phenomenal contained-metal value allows them to be mined economically at depths where the Ni deposits that spawned them are subeconomic.
In the ultimate stages of sulfide-magma evolution, at temperatures between 200 and 700°C, sulfide melts probably evolve into highly mobile liquid solutions composed of PGE, Au, Ag, S, Te, Bi, Sb, As, and Cl, in which PGE and all of these otherwise rare elements become major elements. The final crystallization products of these very small volumes of melt are composed primarily of platinum-group minerals such as PGE sulfides, intermetallic compounds, and sulfosalts. Widely dispersed disseminations of these minerals occur in the absence of significant base-metal sulfides around the more conventional fractionated sulfide deposits at Sudbury and have recently spurred a major boom in exploration around the Sudbury Igneous Complex.
Aqueous fluids and halide melts contain tens to hundreds of times higher concentrations of the PGE than coexisting silicate melts. Late deuteric fluids and melts have been identified at Sudbury and in both the Stillwater and the Bushveld intrusions, where they have been found to contain Pt and Pd concentrations comparable to experimentally measured values, on the order of several ppm (Hanley 2005). The possible role of these fluids in the generation of the truly vast ore deposits of the Bushveld and Stillwater intrusions remains a topic of vigorous debate, as described below.
|
|
ORE DEPOSIT MODELS |
|---|
|
TOPABSTRACTINTRODUCTIONORE DEPOSIT MODELSPGE MINERALIZATION OF THE...FUTURE OUTLOOKREFERENCES |
|---|
Peripheral To or Within Accumulations of Sulfide Liquid
This style of deposit forms as a result of the crystallization of a sulfide
liquid that has already been concentrated from mafic or ultramafic silicate
magma. Characteristically, these ores are rich in Cu, Pt, Pd, and Au and
relatively poor in Rh, Ru, Ir, and Os. They are thought to have resulted from
the cooling and crystallization (fractional, equilibrium, or a combination of
both) of the sulfide liquid, with the separation of a fractionated component
and its migration and concentration away from the early-crystallizing
pyrrhotite-dominant component (Naldrett et
al. 1982; Naldrett
2004; Mungall
2007). Classic examples of this style of mineralization are found
at Noril'sk-Talnakh in Siberia, where they constitute zones within the massive
ore, veins in the foot-wall, and peripheral disseminations; and at Sudbury,
Canada, where they form massive, chalcopyrite-rich veins. In the latter
example, Farrow et al. (2005)
showed that a zone of veinlets containing Ni- and Cu-rich sulfides (millerite,
bornite, and others) and associated high concentrations of PGE surround many
of the chalcopyrite-rich veins. This peripheral mineralization is almost
certainly a hydrothermal phase either imposed on, or originating from,
original Cu-rich magmatic sulfides, combined with widely dispersed late
sulfosalt melts that migrated along grain boundaries and microfractures
through the host rock.
Layers of Very High-PGE-Tenor Sulfides Within a Layered Intrusion
Without Substantial Chromite
These constitute stratiform accumulations of PGE-rich, sparsely (0.5-3
vol%) disseminated sulfides such as those in the Merensky and J-M reefs of the
Bushveld and Stillwater complexes. The PGE contents correlate closely with the
sulfide content of the rock. Because of their importance as sources of PGE
(FIG. 3), Bushveld
deposits are discussed in greater detail below. The Great Dyke differs from
the deposits of the Bushveld Complex in that PGE, Ni, and Cu are not
associated with a distinctive horizon (i.e. "reef") but occur as a
zone of sparsely disseminated sulfide, approximately 1-5 m thick, within
uniform pyroxenite (the Main Sulfide Zone). The metals show a vertical zoning,
with the concentrations of Pd and Rh in 100% sulfides being highest near the
base of the sulfide zone and decreasing sharply upward, followed sequentially
by the concentrations of Pt, Au, Cu, and Ni
(Naldrett and Wilson 1990).
This zonation is thought to be the consequence of the ease with which the PGE
are concentrated within segregating sulfide droplets, which is, in turn, a
function of (1) the respective partition coefficients between the sulfide
liquid and the silicate magma and (2) their diffusivities within silicate
magma (Mungall 2002).
Associated with Chromitite Horizons These are also stratiform accumulations of PGE and include the UG-2, UG-1, MG-3, and MG-2 chromitites of the Bushveld Complex (Scoon and Teigler 1994; FIG. 4). The UG-2 chromitite is the world's largest single accumulation of PGE (FIG. 3) and extends for nearly the entire 400 km strike length of the eastern and western limbs of the Bushveld Complex.
|
Delayed Separation of Sulfide during the Crystallization of a Layered Intrusion
Examples include the Rio Jacaré intrusion of Bahia, Brazil
(Sá et al. 2005), and
the Platinova Reef in the Skaergaard intrusion
(Andersen et al. 2002). This
mechanism gives rise to deposits that are relatively rich in Cu, Pt, Pd, and
Au and much poorer in Ru, Ir, and Os. For example, Sá et al.'s
(2005) average Pd/Ir and Cu/Ni
ratios for the Rio Jacaré intrusion are 206 and 3.10, respectively,
compared to 16.4 and 0.31 for the Merensky Reef (Merensky data are an average
of analyses from Naldrett
2004, appendix to chapter 1). The Volkovsky deposits, which are
associated with titaniferous magnetite, apatite, and Cu-sulfides in the
calc-alkaline gabbros of the Urals Platinum Belt, also belong to this group,
as does the Stella intrusion of South Africa
(Maier et al. 2003).
Chromite Crystallization Without the Development of Sulfide Immiscibility
Deposits formed in this way tend to be enriched in Ru, Ir, and Os and
relatively poor in Ni, Cu, Pt, Pd, and Au and are mostly found within
ophiolite complexes. While examples of this association do not constitute
economic in situ PGE resources, they give rise to important placer deposits in
the Urals and elsewhere.
Hydrothermal Redistribution of PGE
Examples of this type were reviewed by Wilde
(2005) and include the New
Rambler mine in Wyoming, U.S.A., the Waterberg deposit, Transvaal, South
Africa, and the Coronation Hill deposit, Australia. The genesis of
hydrothermal ores is not well understood as yet, but most appear to be the
result of highly oxidized Cl-rich aqueous fluids concentrating PGE that occur
dispersed in host intrusions. Depositional sites are controlled by abrupt
changes in fluid pH or redox state that are caused by changes in wall-rock
chemistry. Under conditions of 1.5 kb total pressure, oxygen fugacity equal to
that of the Ni-NiO buffer, and 600-800°C, NaCl brines can dissolve very
high concentrations of Pt. For example, Pt-saturated brines containing 20 wt%
equivalent NaCl contain typically 1000-3000 ppm Pt
(Hanley 2005). Pt solubility
increases with increasing temperature but decreases markedly with increasing
NaCl concentration, suggesting that under these conditions the main ligand is
hydroxyl.
Secondary Concentration of PGE Associated with Chromite Schlieren in Zoned Dunite-Pyroxenite Intrusions
These intrusions are commonly referred to as "Alaskan" or
"Alaskan-Ural" type, and deposits include the PGE mineralization
at Nizhny Tagil in the Urals. Similar deposits occur in Koryakia, northeastern
Russia (Nazimova et al. 2003),
and in the Kondyor intrusion within the Siberian platform. Platinum is the
principal PGE that is concentrated. Some in situ mining has occurred in this
environment in the Urals (Nizhny Tagil-Soleviev Hills), but the main
importance lies in the major Pt-rich placer deposits that result from erosion
of these intrusions.
Hydrothermally Concentrated PGE (Principally Pt) in Black Shales, Often in Association with Au
A classic example of this type is the Sukhoi Log gold deposit in Siberia
(Distler and Yudovskaya 2005).
It is important to note that the concentration of Pt does not covary with that
of Au at Sukhoi Log, implying that the two metals were concentrated by
different mechanisms.
|
PGE MINERALIZATION OF THE BUSHVELD COMPLEX |
|---|
|
TOPABSTRACTINTRODUCTIONORE DEPOSIT MODELSPGE MINERALIZATION OF THE...FUTURE OUTLOOKREFERENCES |
|---|
Based on our understanding of the causes of sulfide immiscibility, chromite precipitation may well be accompanied by the segregation of immiscible sulfide. Silicate zones within the UG-2 are marked by very radiogenic Sr (Seabrook et al. 2005), indicating that the energetic introduction of fresh magma and the mixing of this magma with melted roof rocks may have caused chromite to crystallize and sulfides to segregate. However the sparsity of sulfide and the high Ni/Cu ratio of the UG-2 in comparison with the Merensky Reef have raised doubts as to whether sulfides are in fact the principal collector. Magnetite can contain excess O2 at high temperature, but its composition narrows to stoichiometric Fe3O4 by 900°C; it is thought that the resulting chemical potential gradient of Fe into the magnetite component of chromite is sufficient to destabilize adjacent pyrrhotite, resulting in an overall loss of Fe (and S) from the sulfide phase (Naldrett 2004). Sulfide with a composition like that of the Merensky Reef could have been the principal collector of the PGE in the UG-2 but has been lost as a result of this reaction, leaving the PGE isolated in platinum-group minerals.
The Platreef is the third main source of PGE in the Bushveld. It is a zone of pyroxenite with similarities to the pyroxenites occurring within the Bushveld Critical Zone (the zone that hosts the chromitite seams and the Merensky Reef). The Platreef forms the floor of the Bushveld along the northern limb, where it has reacted extensively with country-rock dolomites, iron formation, and shale of the Transvaal Supergroup. PGE-, Ni-, and Cu-rich sulfides occur within it, forming 40-100 m thick zones as a result of repeated injections of magma along the contact. Some of the sulfide tenors are very similar to those of the Merensky Reef, perhaps as a result of Critical Zone magma escaping up the sloping contact of the Bushveld magma chamber as fresh magma entered at depth.
In all three examples of PGE mineralization hosted by the Bushveld Intrusion, there is a distinctive association of very high PGE tenor with minor quantities of sulfide liquid in equilibrium with silicate melt, underscoring the ultimate importance of sulfide melt as a collector phase for the PGE in a variety of magmatic environments. Both the "uppers" and "downers" models require the existence of sulfide melt as the final resting place of the PGE that make up the deposits, despite differences in opinion regarding the proximal sources of the PGE. Also, in both models, the ultimate source of the PGE is the mantle source region of the mafic or ultramafic rocks hosting the deposits.
|
FUTURE OUTLOOK |
|---|
|
TOPABSTRACTINTRODUCTIONORE DEPOSIT MODELSPGE MINERALIZATION OF THE...FUTURE OUTLOOKREFERENCES |
|---|
|
ACKNOWLEDGMENTS |
|---|
|
REFERENCES |
|---|
|
TOPABSTRACTINTRODUCTIONORE DEPOSIT MODELSPGE MINERALIZATION OF THE...FUTURE OUTLOOKREFERENCES |
|---|
Andersen JCO, Power MR, Momme P (2002) Platinum-group elements in the Paleogene North Atlantic Igneous Province. In: Cabri LJ (ed)The Geology, Geochemistry, Mineralogy and Mineral Beneficiation of Platinum-Group Elements . CIM Special Volume 54, pp637 -667
Arndt NT, Lesher CM, Czamanske GK (2005) Mantle-derived magmas and magmatic Ni-Cu-(PGE) deposits. In: Hedenquist JW, Thompson JFH, Goldfarb RJ, Richards JP (eds) Economic Geology One Hundredth Anniversary Volume, pp.5 -24
Barnes S-J, Lightfoot PC (2005) Formation of magmatic nickel sulfide ore deposits and processes affecting their copper and platinum group element contents. In: Hedenquist JW, Thompson JFH, Goldfarb RJ, Richards JP (eds) Economic Geology One Hundredth Anniversary Volume, pp.179 -214
Boudreau AE, McCallum IS (1992) Concentration of
platinum-group elements by magmatic fluids in layered intrusions.Economic Geology
87:1830
-1848
Campbell IH, Naldrett AJ (1979) The influence of
silicate:sulfide ratios on the geochemistry of magmatic sulfides.Economic Geology
74:1503
-1506
Campbell IH, Naldrett AJ, Barnes SJ (1983) A model for
the origin of the platinum-rich sulfide horizons in the Bushveld and
Stillwater Complexes. Journal of Petrology24
: 133-165
Cawthorn RG (2005) Pressure fluctuations and the formation of the PGE-rich Merensky and chromitite reefs, Bushveld Complex.Mineralium Deposita 40:231 -235[CrossRef][Web of Science][GeoRef]
Distler VV, Yudovskaya MA (2005) Polymetallic platinum-group element (PGE)-Au mineralization of the Sukhoi Log deposit, Russia. In: Mungall JE (ed) Exploration for Platinum-Group Elements Deposits. Mineralogical Association of Canada Short Course Volume35 , pp 457-485
Farrow CEG, Everest JO, King DM, Jolette C (2005) Sudbury Cu-(Ni)-PGE systems: Refining the classification using McCreedy West Mine and Podolsky Project case studies. In: Mungall JE (ed) Exploration for Platinum-Group Elements Deposits. Mineralogical Association of Canada Short Course Volume 35, pp163 -180
Fleet ME, Crocket JH, Liu M, Stone WE (1999) Laboratory partitioning of platinum-group elements (PGE) and gold with application to magmatic sulfide-PGE deposits. Lithos47 : 127-142[CrossRef][Web of Science][GeoRef]
Hanley JJ (2005) The aqueous geochemistry of the platinum-group elements (PGE) in surficial, low-T hydrothermal and high-T magmatic-hydrothermal environments. In: Mungall JE (ed) Exploration for Platinum-Group Elements Deposits. Mineralogical Association of Canada Short Course Volume 35, pp35 -56
Jugo PJ, Luth RW, Richards JP (2005) An experimental
study of the sulfur content in basaltic melts saturated with immiscible
sulfide or sulfate liquids at 1300°C and 1.0 GPa. Journal of
Petrology 46:783
-798
Keays RR (1995) The role of komatiitic and picritic magmatism and S-saturation in the formation of ore deposits.Lithos 34:1 -18[CrossRef][Web of Science][GeoRef]
Kinnaird JA, Hutchinson D, Schürmann L, Nex PAM, de Lange R (2005) Petrology and mineralisation of the southern Platreef: northern limb of the Bushveld Complex, South Africa. Mineralium Deposita 40:576 -597[CrossRef][Web of Science][GeoRef]
Lorand J-P, Luguet A, Alard O (2008) Platinum-group
elements: A new set of key tracers for the Earth's interior.Elements
4:247
-252
Maier WD, Barnes S-J, Gartz V, Andrews G (2003) Pt-Pd
reefs in magnetitites of the Stella layered intrusion, South Africa: A world
of new exploration possibilities for platinum group elements.Geology
31:885
-888
Mavrogenes JA, O'Neill HSC (1999) The relative effects of pressure, temperature and oxygen fugacity on the solubility of sulfide in natural magmas. Geochimica et Cosmochimica Acta63 : 1173-1180[CrossRef][Web of Science][GeoRef]
Mungall JE (2002) Kinetic controls on the partitioning
of trace elements between silicate and sulfide liquids. Journal of
Petrology 43:749
-768
Mungall JE (2007) Magmatic ore deposits. In: Rudnick R (ed) The Crust. Treatise on Geochemistry Volume 3, Chapter 21. Elsevier, pp 1-33
Naldrett AJ (2004) Magmatic Sulfide Deposits: Geology, Geochemistry and Exploration. Springer,728 pp
Naldrett AJ, Wilson AH (1990) Horizontal and vertical variations in noble-metal distribution in the Great Dyke of Zimbabwe: A model for the origin of the PGE mineralization by fractional segregation of sulfide.Chemical Geology 88:279 -300[CrossRef][Web of Science][GeoRef]
Naldrett AJ, Innes DG, Sowa J, Gorton MP (1982)
Compositional variations within and between 5 Sudbury ore deposits.Economic Geology
77:1519
-1534
Naldrett AJ, Kinnaird J, Wilson A, Chunnett G (2008) The concentration of PGE in the earth's crust with special reference to the Bushveld Complex. Earth Science Frontiers15 : (in press)
Nazimova YuV, Zaitsev VP, Mochalov AG (2003) Platinum group minerals of the Gal'moenan gabbro-pyroxenite-dunite massif in the southern part of the Koryak Highland (Russia). Geology of Ore Deposits 45:481 -500[Web of Science]
Palme H (2008) Platinum-group elements in
cosmochemistry. Elements 4:233
-238
Sá JHS, Barnes S-J, Prichard HM, Fisher PC
(2005) The distribution of base metals and platinum-group
elements in magnetitite and its host rocks in the Rio Jacaré Intrusion,
northeastern Brazil. Economic Geology100
: 333-348
Scoon RN, Teigler B (1994) Platinum-group element mineralization in the critical zone of the Bushveld Complex. 1. Sulfide-poor chromitites below the UG-2. Economic Geology89 : 1094-1121
Seabrook CL, Cawthorn RG, Kruger FJ (2005) The
Merensky Reef, Bushveld Complex: Mixing of minerals not mixing of magmas.Economic Geology
100:1191
-1206
Wendlandt RF (1982) Sulfide saturation of basalt and andesite melts at high pressures and temperatures. American Mineralogist 67:877 -885[Abstract][Web of Science][GeoRef]
Wilde A (2005) Descriptive ore deposit models: Hydrothermal & supergene Pt & Pd deposits. In: Mungall JE (ed)Exploration for Platinum-Group Elements Deposits . Mineralogical Association of Canada Short Course Volume 35, pp145 -161
This article has been cited by other articles:
|
|
 |
|
  J. M. Brenan The Platinum-Group Elements: "Admirably Adapted" for Science and Industry Elements, August 1, 2008; 4(4): 227 - 232. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. W. Carlson, S. B. Shirey, and M. Schonbachler Applications of PGE Radioisotope Systems in Geo- and Cosmochemistry Elements, August 1, 2008; 4(4): 239 - 245. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J.-P. Lorand, A. Luguet, and O. Alard Platinum-Group Elements: A New Set of Key Tracers for the Earth's Interior Elements, August 1, 2008; 4(4): 247 - 252. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| JOURNAL HOME | HELP | CONTACT PUBLISHER | SUBSCRIBE | ARCHIVE | SEARCH | TABLE OF CONTENTS |
