The concentration of platinum-group elements and gold in southern African and Karelian kimberlite-hosted mantle xenoliths: Implications for the noble metal content of the Earth's mantle

Maier, Wolfgang D.; Peltonen, P.; McDonald, Iain; Barnes, Sarah‐Jane; Hatton, Chris; Viljoen, K.S.

doi:10.1016/j.chemgeo.2011.06.014

Cited by 68 publications

(51 citation statements)

References 96 publications

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“…Studies based on bulk rock geochemistry (e.g., Maier et al, 2012) may be prone to significant nugget effects because of the heterogeneous distribution of PGE-bearing microphases (Lorand et al, 2013), and thus detailed investigations that combine base metal sulphide petrography, mineral trace element compositions and isotopic systematics (particularly for the Re-Os system) are vital to assess the true complexity of the upper mantle sulphur and chalcophile element reservoir (e.g., Alard et al, 2000Alard et al, , 2005Aulbach et al, 2009;Griffin et al, 2002Griffin et al, , 2004Harvey et al, 2010;Lorand et al, 1990Lorand et al, , 2008Lorand et al, , 2010Luguet et al, 2003Luguet et al, , 2004Marchesi et al, 2013;Szabo et al, 1995;Wainwright et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

Paradoxical co-existing base metal sulphides in the mantle: The multi-event record preserved in Loch Roag peridotite xenoliths, North Atlantic Craton

Hughes

McDonald

Loocke

et al. 2017

Lithos

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This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPT A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPT AbstractThe role of the subcontinental lithospheric mantle as a source of precious metals for mafic magmas is contentious and, given the chalcophile (and siderophile) character of metals such as the platinumgroup elements (PGE), Se, Te, Re, Cu and Au, the mobility of these metals is intimately linked with that of sulphur. Hence the nature of the host phase(s), and their age and stability in the subcontinental lithospheric mantle may be of critical importance. We investigate the sulphide mineralogy and sulphide in situ trace element compositions in base metal sulphides (BMS) in a suite of spinel lherzolite mantle xenoliths from northwest Scotland (Loch Roag, Isle of Lewis). This area is situated on the margin of the North Atlantic Craton which has been overprinted by a Palaeoproterozoic orogenic belt, and occurs in a region which has undergone magmatic events from the Palaeoproterozoic to the Eocene.We identify two populations of co-existing BMS within a single spinel lherzolite xenolith (LR80) and which can also be recognised in the peridotite xenolith suite as a whole. Both populations consist of a mixture of Fe-Ni-Cu sulphide minerals, and we distinguished between these according to BMS texture, petrographic setting (i.e., location within the xenolith in terms of 'interstitial' or within feldspar-spinel symplectites, as demonstrated by X-ray Computed Microtomography) and in situ trace element composition. Group A BMS are coarse, metasomatic, have low concentrations of total PGE (< 40 ppm) and high (Re/Os) N (ranging 1 to 400). Group B BMS strictly occur within symplectites of spinel and feldspar, are finer-grained rounded droplets, with micron-scale PtS (cooperite), high overall total PGE concentrations (15-800 ppm) and low (Re/Os) N ranging 0.04 to 2. Group B BMS sometimes coexist with apatite, and both the Group B BMS and apatite can preserve rounded micron-scale Ca-carbonate inclusions indicative of sulphide-carbonate-phosphate immiscibility. This carbonate-phosphate metasomatic association appears to be important in forming PGE-rich sulphide liquids, although the precise mechanism for this remains obscure. As a consequence of their position within the symplectites, Group B BMS are particularly vulnerable to being incorporated in ascending A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPTmantle-derived magmas (either by melting or physical entrainment). Based on the cross-cutting relationships of the symplectites, it is possible to in...

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Section: Introductionmentioning

confidence: 99%

Paradoxical co-existing base metal sulphides in the mantle: The multi-event record preserved in Loch Roag peridotite xenoliths, North Atlantic Craton

Hughes

McDonald

Loocke

et al. 2017

Lithos

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“…22, 23). Mantle rocks are depleted in Al, but have essentially unfractionated Pt and Ir (24). The only known terrestrial material with Pt/Ir ratios comparable to those in iron meteorites is the Pt-rich sulfides from the Sudbury Footwall (25).…”

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confidence: 99%

Large Pt anomaly in the Greenland ice core points to a cataclysm at the onset of Younger Dryas

Petaev

Huang

Jacobsen

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

112

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One explanation of the abrupt cooling episode known as the Younger Dryas (YD) is a cosmic impact or airburst at the YD boundary (YDB) that triggered cooling and resulted in other calamities, including the disappearance of the Clovis culture and the extinction of many large mammal species. We tested the YDB impact hypothesis by analyzing ice samples from the Greenland Ice Sheet Project 2 (GISP2) ice core across the Bølling-Allerød/YD boundary for major and trace elements. We found a large Pt anomaly at the YDB, not accompanied by a prominent Ir anomaly, with the Pt/Ir ratios at the Pt peak exceeding those in known terrestrial and extraterrestrial materials. Whereas the highly fractionated Pt/Ir ratio rules out mantle or chondritic sources of the Pt anomaly, it does not allow positive identification of the source. Circumstantial evidence such as very high, superchondritic Pt/Al ratios associated with the Pt anomaly and its timing, different from other major events recorded on the GISP2 ice core such as well-understood sulfate spikes caused by volcanic activity and the ammonium and nitrate spike due to the biomass destruction, hints for an extraterrestrial source of Pt. Such a source could have been a highly differentiated object like an Ir-poor iron meteorite that is unlikely to result in an airburst or trigger wide wildfires proposed by the YDB impact hypothesis. meteorite impact | climate change | ICP-MS analysis | PGE

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“…Maier et al [37] [85] show that the lowest PGEs contents are found in >3.5 Ga komatiites from the Barberton (South Africa) and Pilbara (Western Australia) terranes.The authors [37] [85] also show that the most of Early Archaean (3.5 -3.2 Ga) komatiites from the Barberton greenstone belt and the Pilbara craton are depleted in PGEs relative to late Archaean (~2.9 -2.7 Ga) and younger (2.5 -2.0 Ga) komatiites. Maier et al [85] proposed that the trends reflect sluggish refertilization of PGEs in the Early and Middle Archean lower mantle with the late veneer, and that the Archean mantle had heterogeneous PGEs content.…”

Section: The "Late Veneer" Hypothesis Of Pges Enrichmentmentioning

confidence: 99%

“…Maier et al [37] Prescher et al [82] state that the Archean komatiites indicate that the PGEs content of the Earth's mantle increased from about half of their present abundances at 3.5 Ga to their present abundances at 2.9 Ga. The authors [82] proposed that this secular increase in PGE content suggests a progressive mixing of the late veneer material into the Earth's mantle and that the whole mantle was relatively well mixed by 2.9 Ga.…”

Section: The "Late Veneer" Hypothesis Of Pges Enrichmentmentioning

confidence: 99%

Concentration of Platinum Group Elements during the Early Earth Evolution: A Review*

Pilchin¹,

Eppelbaum²

2017

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Numerous unique geological processes [1] took place during the early Earth evolution; several of them, especially those occurring in the Hadean-Early Archean and later, are reflected in the modern geological (geophysical, geochemical, etc.) pattern. One such significant enigmatic feature is the preservation of extremely dense and heavy platinum group elements (PGEs): Pt, Pd, Rh, Ru, Ir, Os. Concentration of PGEs during this period could have taken place in two ways: 1) presence of particular matter capable of preserving PGEs near the earth's surface, 2) transportation of PGEs by magma flows from deep lithospheric (asthenospheric) layers (slabs) to the subsurface. Clearly, much of the dense and heavy PGEs did not sink through to the Earth's mantle (core) at the time of the magma-ocean, and occur near Earth's surface in abundances for formation of ore deposits with PGE concentrations found to be 2 -3 orders of magnitude greater than those in their host media. Their enrichments are associated in numerous cases with such enigmatic phenomena as formation of anorthosites and anorthosite-bearing layered magmatic intrusions. PGE deposits and mineralization zones are also found in associations with chromitites, dunites and serpentinites. In this review, problems related to the initial concentration and preservation of PGEs, their association with anorthosites, and formation of layered intrusions are discussed in detail. The main aim of this article is analysis of the requirements-initial concentration and preservation of PGE and PGM (Platinum Group Minerals) during the early Earth evolution, as well as examination of the distribution behavior of some PGEs in different ore deposits and meteorites. It is supposed that meteoritic bombardment of Earth has played a significant role in formation of PGEs deposits. Some conclusions made in this article may be useful for developing and enhancing strategies of prospecting for PGEs deposits.

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The concentration of platinum-group elements and gold in southern African and Karelian kimberlite-hosted mantle xenoliths: Implications for the noble metal content of the Earth's mantle

Cited by 68 publications

References 96 publications

Paradoxical co-existing base metal sulphides in the mantle: The multi-event record preserved in Loch Roag peridotite xenoliths, North Atlantic Craton

Paradoxical co-existing base metal sulphides in the mantle: The multi-event record preserved in Loch Roag peridotite xenoliths, North Atlantic Craton

Large Pt anomaly in the Greenland ice core points to a cataclysm at the onset of Younger Dryas

Concentration of Platinum Group Elements during the Early Earth Evolution: A Review*

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