Os-isotope variability within sulfides from podiform chromitites

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• 作者：José ; M. Gonzá ; lez-Jimé ; nez^a ; ^{jose.gonzalez@mq.edu.au} ; ^{jmgonzj@ugr.es} ; Fernando Gervilla^b ; ^{gervilla@ugr.es} ; William L. Griffin^a ; ^{bill.griffin@mq.edu.au} ; Joaquí ; n A. Proenza^c ; ^{japroenza@ub.edu} ; Thierry Augé ; ^d ; ^{t.auge@brgm.fr} ; Suzanne Y. O'Reilly^a ; ^{sue.oreilly@mq.edu.au} ; Norman J. Pearson^a ; ^{norman.pearson@mq.edu.au}
• 关键词：Re&ndash ; Os isotopes ; Sulfides in chromitites ; Podiform chromitite ; Ophiolites ; Upper mantle
• 刊名：Chemical Geology
• 出版年：2012
• 出版时间：6 January, 2012
• 年：2012
• 卷：291
• 期：Complete
• 页码：224-235
• 全文大小：1164 K

文摘

In situ laser ablation MC-ICPMS was used to measure the Os-isotope compositions of single sulfide grains (?#xA0;5 ¦Ìm 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 ¦Ìm 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.