Chromian spinel-rich black sands from eastern shoreline of Andaman Island, India: Implication for source characteristics

Journal of Earth system science

Koyel Bhatta1¹  Biswajit Ghosh1¹ 

[1] Department of Geology, University of Calcutta, 35 Ballygunge Circular Road, Kolkata 700 019, India.$$

关键词: Chromian spinel;    detrital sand;    ophiolites;    Andaman Island;    India.;   

DOI  :  

学科分类：天文学(综合)

来源: Indian Academy of Sciences

【 摘 要 】

Black sands rich in chromian spinel commonly occur in pockets along the eastern shoreline of Andaman Island where various types of peridotites and volcanics belonging to the Andaman ophiolite suite are exposed in close vicinity. The chemistry of these detrital chromian spinels has been extensively used here in identifying the source rocks vis-à-vis deciphering the source characteristics. The composition of the chromian spinels (Cr#: 0.20–0.88, Mg#: 0.26–0.77, Al2O3: 5.04–48.21 wt.%, TiO2: up to 1.39 wt.% and Fe2+/Fe3+: 1.73–9.12) varies widely signifying multiple sources, of which mantle peridotites and volcanic rocks are relevant in an ophiolitic terrain. The volcanic chromian spinels are relatively fresh, commonly euhedral, sometimes with compositional variations, and contain inclusions in contrast to the mantle peridotitic chromian spinels which are rounded, extensively fractured, and altered. We used a number of geochemical bivariate plots in order to know the provenance protoliths. The volcanic chromian spinels show geochemical characters of MORB, related to spreading centers (either MOR or back-arc) and also boninites/arc-tholeiites, related to active subduction. On the other hand, the peridotitic spinels indicate partially depleted lherzolite and depleted harzburgite source of the ophiolite suite.

【 授权许可】

Unknown