Palladium, platinum, rhodium, ruthenium, and iridium in chromitites from the Massif du Sud and Tiebaghi Massif, New Caledonia

Page, Norman J; Cassard, Daniel; Haffty, Joseph

doi:10.2113/gsecongeo.77.6.1571

Cited by 65 publications

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“…Although most chromitites in ophiolites contain between 100 and 500 ppb of PGE and have moderate to low Pd/Ir values (0.8-0.1) (Leblanc 1991), PGE-rich (>750 ppb) chromitites with very low Pd/Ir values (< 0.1) have been described from some ophiolites, such as the Massif du Sud in New Caledonia (Page et al 1982a). The PGE contents of our PGE-rich chromitite (1500 ppb) with an extremely low Pd/Ir value (0.007) (Ahmed & Arai 2002) now place parts of the Oman ophiolite among the most PGE-enriched of ophiolite complexes.…”

Section: The Oman Ophiolite Among Others: a Comparisonmentioning

confidence: 99%

Platinum-Group Minerals in Podiform Chromitites of the Oman Ophiolite

Ahmed¹,

Arai²

2003

The Canadian Mineralogist

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Chromitite lenses rich in the platinum-group elements (PGE) have recently been discovered in the deeper part of the mantle section of the northern part of the Oman ophiolite. In terms of stratigraphic level, there are two types of chromitite: Moho transition zone (MTZ) and mantle types. The mantle type can be further classified into two subtypes: PGE-poor and PGE-rich. Platinum-group minerals (PGM) have been mainly observed in the PGE-rich mantle chromitite and, to a lesser extent, in the PGEpoor mantle chromitite, although a few PGM grains have been detected from the MTZ chromitites. The PGM comprise four main categories in the following order of abundance: (1) sulfides [Os-rich laurite, erlichmanite and unnamed (Ir,Rh)(Ni,Cu,Fe) 2 S 3 ], (2) sulfarsenide and arsenide (irarsite-hollingworthite series, palladoarsenide), (3) alloys and native metals [Os-Ir alloy, (Cu-Pt-FeIr-Rh) alloy, Pt-Fe alloy, (Ni-Ru-Os-Ir) alloy, Ir-Pt alloy, Ir-Rh alloy and native Pd metal], and (4) PGE oxide (Ru-Os-Ir oxide). Base-metal sulfides (BMS) and base-metal alloys (BMA) also are found, as inclusions in chromian spinel and interstitial matrix, mainly in the MTZ and PGE-poor mantle chromitites. The common abundance of PGE sulfides, i.e., Os-rich laurite, in the Oman chromitites is ascribed to the sulfide-undersaturated nature of the magma involved in chromitite formation. However, the sulfur fugacity was sufficiently high to produce the Os-rich laurite and, to a lesser extent, erlichmanite and Ru-poor Os-Ir alloy. The sulfur fugacity was higher in the formation of the PGE-poor mantle chromitite relative to the PGE-rich chromitite, as indicated by the presence of the unnamed Ir-rich sulfides and, to a lesser extent, BMS. The presence of PGE oxide commonly associated with fractured chromian spinel indicates that the PGE distribution in rocks can easily be modified at an early stage of serpentinization.Keywords: laurite, chromitite, ophiolite, platinum-group elements, platinum-group minerals, sulfur fugacity, northern Oman. SOMMAIRENous avons récemment découvert des lentilles de chromitite enrichies en éléments du groupe du platine (EGP) dans la partie la plus profonde de la séquence mantellique de la partie nord de l'ophiolite d'Oman. Du point de vue niveau stratigraphique, nous distinguons deux sortes de chromitites, celles qui sont associées à la zone de transition du Moho (MTZ), et celles provenant du manteau sousjacent. Ces dernières comprennent à leur tour deux types, l'un pauvre en EGP et l'autre enrichi en EGP. Les minéraux du groupe du platine se trouvent surtout dans les chromitites mantelliques enrichies en EGP, quoique qu'on en trouve aussi, mais à un degré moindre, dans les chromitites mantelliques à faible teneur en EGP et dans les chromitites de type MTZ. Nous documentons quatre groupes de ces minéraux, présentés ici dans un ordre selon leur abondance: (1) (4) oxyde des EGP (oxyde Ru-Os-Ir). Nous avons aussi trouvé des sulfures et des alliages de métaux de base, en inclusion dans le spinelle chromifère et dans l...

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Section: The Oman Ophiolite Among Others: a Comparisonmentioning

confidence: 99%

Platinum-Group Minerals in Podiform Chromitites of the Oman Ophiolite

Ahmed¹,

Arai²

2003

The Canadian Mineralogist

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“…Ophiolitic chromitites are characterized on a chondrite-normalized diagram (Fig. 8A) by curves with a negative slope (Page et al, 1982), while the chromitites of stratiform complexes generally show a strong positive slope. In the first case, the most refractory platinoids (Os, Ir, Ru) form small crystals of high-temperature alloys or sulfides which are enveloped by chromite during its crystallization, while the other platinoids remain in solution and are evacuated with the residual magma (Fig.…”

Section: Platinoidsmentioning

confidence: 99%

Ophiolitic Chromitites

Leblanc

Nicolas

1992

International Geology Review

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“…Ru is mainly found in the form of sulphur minerals such as laurite (RuS 2 ) or ruthenian pentlandite ((Ni,Fe) 8 RuS 8 ), or as Ru-Ir-Os alloys or oxides (RuO 2 ) (Garuti and Zaccarini 1997). All these Ru forms are found in either stratiform or podiform chromitites with Ru concentrations typically in the range of 0.1-1 ppm (relative to mass chromitite) and up to several ppm in Cr-rich veins (e.g., Page and Talkington 1984;Bacuta et al 1990). In ophiolite sequences, Ru-enrichments are preferentially located within tectonite and Moho transition zones, particularly in crustal dunite (Prichard and Brough 2009;Mosier et al 2012).…”

Section: How Abiotic Methane In Land-based Serpentinisation Systems Imentioning

confidence: 99%

“…Most of the land-based serpentinisation seeps documented thus far are adjacent to chromite mines or located above ultramafic rocks hosting Ru-enriched chromitites. Examples include the Chimaera fires in Turkey, located near the ancient chrome mines of Cirali (Juteau 1968), the Semail ophiolite in Oman (Page et al 1982), the Othrys ophiolite in Greece (Garuti et al 1999), the Zambales in the Philippines (Bacuta et al 1990), Newfoundland in Canada (Page and Talkington 1984), and the Cabeço de Vide in Portugal (Dias et al 2006). Deep boreholes, providing abiotic gas from crystalline Precambrian rocks at Sudbury in Canada (Sherwood Lollar et al 2008), are located in one of the richest Ru mines in North America (Ames and Farrow 2007).…”

Section: How Abiotic Methane In Land-based Serpentinisation Systems Imentioning

confidence: 99%

Seepage in Serpentinised Peridotites and on Mars

Etiope

2015

Natural Gas Seepage

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Thus far, this book has mainly addressed the classical seepage of natural gas of biotic (microbial and thermogenic) origin in sedimentary rocks. However, it is also known that methane and other light hydrocarbons can be abiotically produced (i.e., by chemical reactions that do not directly involve organic matter). Abiotic production may occur over a wide range of temperatures and pressures and within a variety of geological systems. Two main classes of abiotic CH 4 generation processes can be distinguished, magmatic and gas-water-rock interactions. For details, the reader is referred to the review of Etiope and Sherwood Lollar (2013). Here, it is important to keep in mind that while magmatic or mantle-derived CH 4 is abiotic, not all abiotic CH 4 is mantle derived. Magmatic and high temperature hydrothermal processes in volcanic and geothermal systems produce a gas mixture that is mainly composed of carbon dioxide (CO 2 ), while abiotic methane is a very minor component. Indeed, field observations suggest that the majority of abiotic gas on Earth's surface is produced by low-temperature, gas-water-rock reactions. Of particular interest are the Fischer-Tropsch Type (FTT) reactions, the mechanism most widely invoked for explaining large quantities of abiotic CH 4 seeping to the surface. In the sub-chapters that follow, only CH 4 -rich abiotic gas seeping to the surface is considered. Such seepage generally occurs in serpentinised ultramafic rocks (peridotites). Serpentinisation (the hydration of olivine and pyroxene minerals, which leads to the formation of H 2 and the subsequent production of CH 4 through FTT synthesis) is considered a fundamental step in the origin of life, representing the primordial passage from inorganic to organic chemistry (Russell et al. 2010). Serpentinisation can also be a source of methane in atypical petroleum systems where hydrocarbon reservoirs are formed by or are adjacent to igneous rocks (Sect. 7.1.2), and a potential source of methane on other planets, such as Mars (Sect. 7.2).

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Palladium, platinum, rhodium, ruthenium, and iridium in chromitites from the Massif du Sud and Tiebaghi Massif, New Caledonia

Cited by 65 publications

References 0 publications

Platinum-Group Minerals in Podiform Chromitites of the Oman Ophiolite

Platinum-Group Minerals in Podiform Chromitites of the Oman Ophiolite

Ophiolitic Chromitites

Seepage in Serpentinised Peridotites and on Mars

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