Re-Os isotope systematics of sulfides in chromitites and host lherzolites of the Andaman ophiolite, India

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Abstract

Laser ablation MC-ICP-MS was used to measure the Os-isotope compositions of single sulfide grains, including laurite (RuS 2) and pentlandite [(Fe,Ni) 9S 8], from two chromitite bodies and host lherzolites from ophiolites of North Andaman (Indo-Burma-Sumatra subduction zone). The results show isotopic heterogeneity in both laurite (n = 24) and pentlandite (n = 37), similar to that observed in other chromitites and peridotites from the mantle sections of ophiolites. Rhenium-depletion model ages (T RD) of laurite and pentlandite reveal episodes of mantle magmatism and/or metasomatism in the Andaman mantle predating the formation of the ophiolite (and the host chromitites), mainly at ≈0.5, 1.2, 1.8, 2.1 and 2.5 Ga. These ages match well with the main tectonothermal events that are documented in the continental crustal rocks of South India, suggesting that the Andaman mantle (or its protolith) had a volume of lithospheric mantle once underlaying this southern Indian continental crust. As observed in other oceanic lithospheres, blocks of ancient subcontinental lithospheric mantle (SCLM) could have contributed to the development of the subduction-related Andaman–Java volcanic arc. Major-and trace-element compositions of chromite indicate crystallization from melts akin to high-Mg IAT and boninites during the initial stages of development of this intra-oceanic subduction system.

Original languageEnglish
Article number686
Pages (from-to)1-21
Number of pages21
JournalMinerals
Volume10
Issue number8
DOIs
Publication statusPublished - Aug 2020

Bibliographical note

Copyright the Author(s) 2020. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.

Keywords

  • ophiolite
  • chromitite
  • platinum-group minerals
  • osmium isotopes
  • Andaman
  • subduction zone

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