Petrogenesis of the Neoarchean zincian chromite within ultramafic xenoliths,Bastar Craton,India  

作　　者：Arpita Karmakar Tushar Meshram Mohammad Asif Yogesh Pandey 

机构地区：[1]Geological Survey of India,Vasudha Bhawan,Kumarswamy Layout,Bangalore 560111,India [2]Geological Survey of India,Nagpur,India [3]Geological Survey of India,Raipur,India

出　　处：《Acta Geochimica》2023年第3期471-487,共17页地球化学学报（英文）

基　　金：Geological Survey of India,Ministry of Mines,Government of India for funding the opportunity to work in this projects。

摘　　要：The present study reports and discusses the genesis of zincian chromite in the ultramafic xenoliths from the Dongripali area,Bastar craton,Central India.The zincian chromite is in the ultramafic xenoliths of Bengpal supracrustal rock hosted by Neoarchaean Bundeli gneisses.Compositionally zincian chromite shows a range of Cr_(2)O_(3)(39.69 to 51.66 wt%),Al_(2)O_(3)(05.30 wt%to 08.71 wt%),FeO(21.74 wt%to 27.51 wt%),Fe_(2)O_(3)(10.19 wt%to 19.36wt%)with higher ZnO content ranging from 1.73 wt%to 4.08 wt%.Accordingly,their Cr#[Cr/(Cr+Al)]varies in a narrow range from 0.83 to 0.85.Its calculated melt composition supports metamorphic or post-magmatic nature rather than common occurrences such as inclusion in diamonds,meteorites,and association with any sulfide-rich mineralised belt.This reveals that the post-magmatic processes play a vital role in transforming chromite to zincian chromite.The empirical thermometric calculation from chromite,amphibole,and pyroxene support their metamorphic origin and formed during low-P and high-T amphibolite grade facies of metamorphism(~700℃).The Neoarchaean granitic magmatism has a significant role in generating and transferring the heat during contact metamorphism with hydration of ultramafic xenoliths and further alteration,i.e.,serpentinisation.The olivine is a major repository for Mn,Zn,and Co in peridotite/ultramafic;these elements get mobilised during the metamorphism and serpentinisation.This is a possible reason for the mobilisation of zinc and incorporation in the chromite within altered ultramafic.As a result,chromiterich ultramafic xenolith subjected to metamorphic process gets enrichment of Zn and Fe due to elemental exchange.It converts common chromite into zincian chromite,as reported in altered ultramafics elsewhere.

关 键 词：Zincian chromite ULTRAMAFIC Neoarchaean granitic magmatism High-grade metamorphism 

分 类 号：P618.3[天文地球—矿床学] P618.43[天文地球—地质学]