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Os-isotope variability within sulfides from podiform chromitites

Abstract : In situ laser ablation MC-ICPMS was used to measure the Os-isotope compositions of single sulfide grains (>= 5 mu m in diameter) included in unaltered primary chromite from the podiform chromitite of Caridad (eastern Cuba). The analyzed phases include PGE-sulfides (laurite and PGE-rich monosulfide solid solution) and base-metal sulfides (BM-sulfides; millerite, heazlewoodite and pentlandite). The results show that PGE-sulfides and the BM-sulfides have distinctly different Os-isotope compositions. Significant variations in Os-isotope composition are found among sulfide grains forming parts of single composite aggregates smaller than 50 mu m in diameter. A similar degree of heterogeneity was observed in some chemically and isotopically zoned sulfide grains. At such small scales, the formation of sulfides with variable Os-isotope signatures requires a heterogeneous genetic process in which individual pulses of isotopically and chemically different melts coexisted in space and/or time. This could be achieved if the podiform chromitites formed as a result of mantle-melt reactions and the subsequent melt mixing/mingling of several batches of melt.
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Soumis le : mardi 23 juillet 2013 - 15:12:58
Dernière modification le : mercredi 3 août 2022 - 04:02:33




Jose M. Gonzalez-Jimenez, Fernando Gervilla, William L. Griffin, Joaquin A. Proenza, Thierry Augé, et al.. Os-isotope variability within sulfides from podiform chromitites. Chemical Geology, Elsevier, 2012, 291, pp.224-235. ⟨10.1016/j.chemgeo.2011.10.016⟩. ⟨hal-00847360⟩



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