کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
4723404 1639647 2013 17 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Chromite–silicate chemistry of the Neoarchean Sittampundi Complex, southern India: Implications for subduction-related arc magmatism
موضوعات مرتبط
مهندسی و علوم پایه علوم زمین و سیارات ژئوشیمی و پترولوژی
پیش نمایش صفحه اول مقاله
Chromite–silicate chemistry of the Neoarchean Sittampundi Complex, southern India: Implications for subduction-related arc magmatism
چکیده انگلیسی

The Neoarchean layered anorthositic complex at Sittampundi in southern India is known for its chromitite layers that are mostly associated with anorthosite (An90–100). 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 Fiskenæsset 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.


► Chromite was derived from a hydrous tholeite generated in a supra-subduction zone arc setting.
► Sittampundi chromitites formed by partial melting of aluminous harzburgite in a mantle wedge.
► The study has important implications for the evolution of a subduction-generated, hydrous island arc, and its bearing on crustal growth in the Archean.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Precambrian Research - Volume 227, April 2013, Pages 259–275
نویسندگان
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