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

• 作者: OA Arpita Karmakar Tushar Meshram Mohammad Asif Yogesh Pandey Geological Survey of India
• 来源期刊: 地球化学学报(英文）
• 学科: 地球科学
• 年，卷（期）: 2025,（3）
• 页码范围: 85-101
• 页数: 17页
• 语种: 中文

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 Cr2O3（39.69 to 51.66 wt%）, Al2O3（05.30 wt% to 08.71 wt%）,FeO（21.74 wt% to 27.51 wt%）, Fe2O3（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 °C）.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.