Platinum group minerals (PGM) in the chromitites from the Nuasahi massif, India

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Marco E. Ciriotti
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Platinum group minerals (PGM) in the chromitites from the Nuasahi massif, India

Messaggio da Marco E. Ciriotti » lun 20 mar, 2017 10:27

Prossima pubblicazione.

Referenza:
▪ Zaccarini, F., Singh, K.A., Garuti, G., Zsatyanarayanan, M. (2017): Platinum group minerals (PGM) in the chromitites from the Nuasahi massif, eastern India: further findings and implications for their origin. European Journal of Mineralogy, 29, (in press).
Marco E. Ciriotti

«Things are interesting only in so far as they relate themselves to other things»

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Marco E. Ciriotti
Messaggi: 23537
Iscritto il: ven 25 giu, 2004 11:31
Località: via San Pietro, 55 I-10073 Devesi/Cirié TO - Italy
Contatta:

Re: Platinum group minerals (PGM) in the chromitites from the Nuasahi massif, India

Messaggio da Marco E. Ciriotti » gio 06 apr, 2017 10:13

Referenza:
▪ Zaccarini, F., Singh, K.A., Garuti, G., Zsatyanarayanan, M. (2017): Platinum-group minerals (PGM) in the chromitite from the Nuasahi massif, eastern India: further findings and implications for their origin. European Journal of Mineralogy, 29, (in press).

Abstract:
We report the first find of Al-rich chromitites in the Nuasahi massif located in the Singhbhum Craton, eastern India. Electron microprobe analyses yielded Al2O3 contents between 19.86 and 25.86 wt%. The Cr2O3 and Fe2O3 concentrations vary (in wt %) from 34.8 to 40.67 and 5.38 to 7.05, respectively. TiO2 content ranges from 0.04 to 0.71 wt%. The silicates interstitial to chromite consist of enstatite, magnesiohornblende and clinochlore. One sample contains 855 ppb of total platinum-group elements (PGE) and shows a chondrite-normalized PGE pattern with a slightly positive slope, with enrichment in Pt and Pd relative to Os and Ir. Ruthenium and Rh show positive and negative peaks, respectively. In agreement with the PGE distribution, the following platinum-group minerals (PGM) have been found: laurite ((Ru,Os)S2), erlichmanite ((Os,Ru)S2), irarsite (IrAsS), vysotskite ((Pd,Ni)S), braggite or cooperite ((Pt,Pd,Ni)S) and Pd-telluride. The PGM form small grains, less than 10 μm across, and occur associated with base metal sulphides (BMS) and rutile included in magmatic minerals, such as chromite and enstatite. The BMS occur exclusively included in chromite. Mineralogical observations suggest that the (Os, Ir, Ru), Pt- and Pd-bearing phases crystallized in the magmatic stage, before or during the precipitation of the host chromite, under relatively high sulphur fugacity. Part of the Pd, together with Te, was initially enclosed at high temperature as small clusters in the sulphide liquid and then incorporated in the crystallizing BMS. Finally, these elements precipitated as Pd-telluride blebs, as an exsolution product at lower temperatures. Rutile occurs as a minor phase in association with PGM, included in chromite or in the contact chromite–silicate. The mode of occurrence of rutile in the Nuasahi chromitite is similar to that reported from the stratiform chromitites emplaced in stable cratonic settings.
Marco E. Ciriotti

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