The Triple Group and the Platinova gold and palladium reefs in the Skaergaard Intrusion; stratigraphic and petrographic relations

Andersen, Jens C.Ø.; Rasmussen, Henrik; Nielsen, Thorkild; Rønsbo, Jørn G.

doi:10.2113/gsecongeo.93.4.488

Cited by 141 publications

(81 citation statements)

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“…In particular, the main PGE peaks in all of these deposits are generally below the main Cu peak; the latter of which marks an increase in bulk sulfide content. The metal offsets have been attributed by some to be due to the effects of D sul/sil values, with elements with higher D values concentrated into the earliest (lowest) layers (Prendergast and Keays 1989;Prendergast 2000;Holwell and Keays 2014); the effects of kinetic fractionation of metals (Mungall 2002); fractionation of the sulfide liquid during filter pressing (e.g., Andersen et al 1998); and separation of and transport by a volatile-and Au-bearing residual of Fe-rich immiscible silicate melts Nielsen et al 2015).…”

Section: Characteristicsmentioning

confidence: 99%

“…1d) which marks the base of the mineralized unit. The gabbros of the Triple Group are made up of Fe-rich plagioclase, clinopyroxene and ilmenite/titanomagnetite (Wager and Brown 1968;Bird et al 1991;Andersen et al 1998;Tegner and Cawthorn 2010;Holness et al 2011;Godel et al 2014).…”

Section: Geological Setting Of the Platinova Reef Skaergaard Intrusionmentioning

confidence: 99%

“…The Skaergaard Intrusion in east Greenland is host to the Platinova Reef, which is an example of a rare subclass of magmatic sulfide deposit, manifested as stratiform PGE reef deposits in the upper parts of the host intrusions (Brooks 1989;Bird et al 1991;Andersen et al 1998;Nielsen et al 2005, Miller andAndersen 2002;Godel et al 2014;Holwell and Keays 2014;Nielsen et al 2015). These deposits differ from the more common disseminated and massive pyrrhotite-pentlandite-chalcopyrite ores found in the lower parts of layered mafic and ultramafic host intrusions, including along the margins and within conduits that feed larger intrusions (e.g., Maier 2005; Naldrett 2011 and references therein).…”

Section: Introductionmentioning

confidence: 99%

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Extreme enrichment of Se, Te, PGE and Au in Cu sulfide microdroplets: evidence from LA-ICP-MS analysis of sulfides in the Skaergaard Intrusion, east Greenland

Holwell

Keays

McDonald

et al. 2015

Contrib Mineral Petrol

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evidence implies that there is no significant post-magmatic hydrothermal S loss and that the metal profiles are essentially a function of magmatic processes. We propose that to generate these extreme precious and semimetal contents, the sulfides must have formed from an anomalously metal-rich package of magma, possibly formed via the dissolution of a previously PGE-enriched sulfide. Other processes such as kinetic diffusion may have also occurred alongside this to produce the ultra-high tenors. The characteristic metal offset pattern observed is largely controlled by partitioning effects, producing offset peaks in the order Pt+Pd>Au>Te>Se>Cu that are entirely consistent with published D values. This study confirms that extreme enrichment in sulfide droplets can occur in closed-system layered intrusions in situ, but this will characteristically form ore deposits that are so low in sulfide that they do not conform to conventional deposit models for Cu-Ni-PGE sulfides which require very high R factors, and settling of sulfide liquids.

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Section: Characteristicsmentioning

confidence: 99%

Section: Geological Setting Of the Platinova Reef Skaergaard Intrusionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Extreme enrichment of Se, Te, PGE and Au in Cu sulfide microdroplets: evidence from LA-ICP-MS analysis of sulfides in the Skaergaard Intrusion, east Greenland

Holwell

Keays

McDonald

et al. 2015

Contrib Mineral Petrol

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“…Many other large layered intrusions, including the Great Dyke of Zimbabwe (Wilson et al 1989), the Munni Munni (Barnes et al 1990) and Windimura intrusions (Parks & Hill 1986) of Western Australia, the Skaergaard intrusion of Greenland (Andersen et al 1998), and the Penikat intrusion of northern Finland (Alapieti & Lahtinen 1986) host only minor occurrences of disseminated stratiform sulfide, generally some distance above the base of the intrusions. These are, however, commonly highly enriched in PGE.…”

Section: Other Large Layered Intrusionsmentioning

confidence: 99%

WHY ARE THERE NO MAJOR Ni Cu SULFIDE DEPOSITS IN LARGE LAYERED MAFIC-ULTRAMAFIC INTRUSIONS?

Maier¹,

Waal

2001

The Canadian Mineralogist

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Large, layered intrusions throughout the world are characterized by a remarkable paucity in economically important magmatic Ni-Cu sulfide deposits. The Sudbury intrusion in Canada is a notable exception, but sulfide ores there were formed by a unique combination of processes involving crustal melting in response to a meteorite impact. Economically important magmatic Ni-Cu sulfide deposits tend to occur in magma conduit systems. Such an environment has been documented at Noril'sk, Jinchuan, and the recently discovered Uitkomst deposit of South Africa and the Voisey's Bay intrusion of Labrador, Canada, which are associated with the Bushveld Complex and the Nain Plutonic Suite, respectively. The enhanced ore potential of conduit systems is attributed to their specific flow environment and to the exploitation of the conduits by multiple flows of magma. Sulfides that were entrained and transported by ascending silicate magma were concentrated in the widened parts of the conduits and, at Voisey's Bay, near the exit of the conduit into a larger chamber, owing to a decrease in the flow velocity of the magma. Further, the precipitated sulfides were upgraded by means of reaction with continued surges of undepleted magma using the same conduit. Thus, exploration for magmatic Ni-Cu sulfide ores should be redirected from layered intrusions to their associated conduit systems.

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“…Peck et al (2001) use a similar model for the East Bull Lake anorthosite. Andersen et al (1998) and Arnason and Bird (2000) have carried the model one step further and suggested that zonation of noble metals found in the Skaergaard and Kap Edvard Holm intrusions are the product of alloy crystallization from the sulphide liquid at low-f S2. Barnes and Maier (2002) have suggested that the strong enrichment of Pt, Os, Ir, Ru and Rh in the chromitite of the Merensky reef is the result of PGM crystallization from the sulphide liquid.…”

Section: Behaviour Of Sulphides During Formation Of Silicate or Oxidementioning

confidence: 99%

Proton microprobe results for the partitioning of platinum-group elements between monosulphide solid solution and sulphide liquid

Barnes

Achterbergh

Makovicky

et al. 2001

South African Journal of Geology

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Partition coefficients (D) for Ni, Cu, and platinum-group elements (PGE) between monosulphide solid solution (mss) and Fe-sulphide liquid (liq) have been determined experimentally using an electron microprobe (EMP) to analyze experimental run products. The EMP detection limit is approximately 0.05 weight per cent for the PGE, consequently few results were obtained for Pt and Ir and the precision for Pd and Rh at low concentrations was poor. These run products have been reanalyzed using a proton microprobe (PMP), which has a detection limit between 10 and 50ppm for these elements.It is now clear that D mss/liquid for all the elements show a strong dependence on the S content of the run in S-undersaturated and S-saturated runs. However, in S-oversaturated runs the S content of the run does not appear to influence D mss/liq . The greater precision of the PMP data establishes that in S-oversaturated runs D mss/liq at 1000°C are consistently higher than those at 1100°C. In contrast, D mss/liq in the S-undersaturated and S-saturated runs are similar at both temperatures. This difference in behaviour is thought to arise because in the S-undersaturated and S-saturated runs the amount of S in the mss is controlled by the S content of the run. As the S content in the mss increases, the number of vacancies in the structure of the mss also increases, and D mss/liq rises. In contrast, in S-oversaturated runs the mss has absorbed the maximum amount of S and thus the S content of the run no longer influences the structure of the mss and hence does not control D mss/liq . Thus, the effect of temperature on D mss/liq only becomes apparent in the S-oversaturated runs. The tendency for Os, Ir, Ru and Rh to partition into mss and the exclusion of Cu, Pt and Pd from mss maybe used to explain a number of phenomena; the zonation of massive sulphide bodies, the tendency for Os, Ir, Ru and to a lesser extent Rh to be enriched in cumulates with minor sulphides, and the presence of two types of sulphides in mantle nodules (an Os-Ir -rich mss and Cu-Pd rich pentlandite).The tendency of sulphide liquids to crystallize RuOsIr and Pt-Fe minerals at low f S2 may explain the enrichment of RuOsIr in ultramafic mafic cumulate rocks in the following manner. Sulphide solubility increases as pressures falls. Thus, sulphide droplets in rising basalt magma could be partly resorbed. The PGM could crystallize from this liquid. If these PGM survive long enough, then they could be incorporated into the early cumulate phases such as olivine and chromite. This would explain both the presence of PGM in many olivine and chromite cumulates and the tendency of more evolved magmas to have high Pd/Ir ratios.

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The Triple Group and the Platinova gold and palladium reefs in the Skaergaard Intrusion; stratigraphic and petrographic relations

Cited by 141 publications

References 0 publications

Extreme enrichment of Se, Te, PGE and Au in Cu sulfide microdroplets: evidence from LA-ICP-MS analysis of sulfides in the Skaergaard Intrusion, east Greenland

Extreme enrichment of Se, Te, PGE and Au in Cu sulfide microdroplets: evidence from LA-ICP-MS analysis of sulfides in the Skaergaard Intrusion, east Greenland

WHY ARE THERE NO MAJOR Ni Cu SULFIDE DEPOSITS IN LARGE LAYERED MAFIC-ULTRAMAFIC INTRUSIONS?

Proton microprobe results for the partitioning of platinum-group elements between monosulphide solid solution and sulphide liquid

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