Hydro-uvarovite from Mantle Peridotites of Naga Hills Ophiolite:A Mineral Tracer for Neo-Tethyan Mantle Wedge Metasomatism

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外文摘要：Hydrous Cr-bearing uvarovite garnets are rare in natural occurrences and belong to the ugrandite series and exist in binary solid solutions with grossular and andradite garnets.Here,we report the occurrence of hydrous uvarovite garnet having Cr2O3 upto 19.66 wt％and CaO of 32.12-35.14 wt％in the serpentinized mantle peridotites of Naga Hills Ophiolite(NHO),India.They occur in association with low-Cr diopsides.They are enriched in LILE(Ba,Sr),LREEs,with fractionating LREE-MREE[avg.(La/Sm)N=2.16]with flat MREE/HREE patterns[avg.(Sm/Yb)N=0.95].Raman spectra indicate the presence of hydroxyl(OH-)peaks from 3500 to 3700 cm-1.Relative abundances in fluid mobile elements and their close association with clinopyroxenes are suggestive of the formation of uvarovite garnets through low temperature metasomatic alteration of low-Cr diopsides by hydrothermal slab fluids.The high LREE concentration and absence of Eu anomaly in the garnet further attest to alkaline nature of the transporting slab dehydrated fluid rather the involvement of low-pH solution.The chemical characteristics of the hydroxyl bearing uvarovite hosted by the mantle peridotite of NHO deviate from the classical features of uvarovite garnet,and their origin is attributed to the fluid-induced metasomatism of the sub arc mantle wedge in a suprasubduction zone regime.

外文关键词：

uvarovitehydroxylmetasomatic alterationlow-Cr diopsidesserpentinizationmantle peridotite

作者：

Anisha VERENCAR、Abhishek SAHA、Nilanjana SORCAR、Sohini GANGULY、Pankaj KUMAR、Atul Kumar SINGH

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作者单位：

CSIR-National Institute of Oceanography,Dona Paula,Goa 403004,India

School of Earth,Ocean and Atmospheric Sciences,Goa University,Taleigão Plateau,Goa 403206,India

National Centre for Earth Science Studies,Thiruvananthapuram,Kerala,India

Inter University Accelerator Centre(IUAC),New Delhi 110067,India

North-Eastern Hill University,Shillong,Meghalaya 793022,India

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基金：

CSIR-National Institute of Oceanography,Goa for his encouragement

项目编号：

出版年：

2024

DOI：

10.1111/1755-6724.15198

地质学报(英文版)

中国地质学会

地质学报(英文版)

CSTPCD

影响因子：1.414

ISSN：1000-9515

年,卷(期)：2024.98(4)