Chromite-silicate chemistry of the Neoarchean Sittampundi Complex, southern India: Implications for subduction-related arc magmatism

Rao, Dharma CV and Santosh, M and Sajeev, K and Windley, BF (2013) Chromite-silicate chemistry of the Neoarchean Sittampundi Complex, southern India: Implications for subduction-related arc magmatism. In: PRECAMBRIAN RESEARCH, 227 (SI). pp. 259-275.

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Abstract

The Neoarchean layered anorthositic complex at Sittampundi in southern India is known for its chromitite layers that are mostly associated with anorthosite (An(90-100)). The chromitites contain FeAl-rich chromites concentrated in layers between amphibole-rich layers with a dominant mineralogy of amphibole-spinel-plagiocase+/-sapphirine. The chromite-rich layers contain only amphibole and plagioclase. Mineral compositions illustrated by X-ray composition maps and profiles show subtle chemical differences. The chrome spinels are of refractory grade with Cr2O3 and Al2O3 contents varying between 34-40 wt.% and 23-28 wt.%. The chromite compositions are noticeably different from those in layered igneous intrusions of the Bushveld-Stillwater type. The existence of original highly calcic plagioclase, FeAl-rich chromite, and magmatic amphibole is consistent with derivation from a parental magma of hydrous tholeiitic composition that was most likely generated in a supra-subduction zone arc setting. In terms of mineralogy and field relations, the Sittampundi chromitites are remarkably similar to anorthosite-hosted chromitites in the Neoarchean Fiskensset anorthositic complex, Greenland. We propose that the Sittampundi chromitites formed by partial melting of unusually aluminous harzburgite in a hydrated mantle wedge above a subduction zone. This melting process produced hydrous, aluminous basalt, which fractionated at depth to give rise to a variety of high-alumina basalt compositions from which the anorthositic complex with its cumulate chromite-rich and amphibole-rich layers formed within the magma chamber of a supra-subduction zone arc. (C) 2011 Elsevier B.V. All rights reserved.

Item Type:	Journal Article
Publication:	PRECAMBRIAN RESEARCH
Publisher:	ELSEVIER SCIENCE BV
Additional Information:	Copyright for this article belongs to the ELSEVIER SCIENCE BV, NETHERLANDS.
Keywords:	Suprasubduction zone; Arc magmatism; Geochemistry; Tectonics; Sittampundi; Southern India
Department/Centre:	Division of Mechanical Sciences > Centre for Earth Sciences
Date Deposited:	30 Apr 2013 11:25
Last Modified:	30 Apr 2013 11:25
URI:	http://eprints.iisc.ac.in/id/eprint/46460

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