Morphotectonic and petrological variations along t

Authors: Ranadhir Mukhopadhyay Sridhar D Iyer Dwijesh Ray S M Karisiddaiah Rajendra K Drolia

Publish Date: 2015/06/26

Volume: 105, Issue: 3, Pages: 905-920

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Abstract

In order to ascertain the effect of geomorphic and tectonic domains on the formation enrichment and ascension of the ridge axis melt structural and petrological data from a nearly 300kmlong axial stretch along the slowtointermediatespreading 40–60 mm/year southern Central Indian Ridge SCIR were studied The stretch approximately between 20°30′S and 23°07′S was disturbed by two major tectonic features—Egeria transform fault in the north and the Gemino Fracture Zone in the south—besides eight other discontinuities of variable dimensions This stretch was chosen to test the petrological variations and mechanisms of magma supply in four distinct geomorphic and tectonic regimes a RidgeCrestFlankValley RCFV a NeoVolcanic Zone NVZ a large transform discontinuity LTD and an overlapping spreading centre OSC The major and trace element geochemistry of 44 glass and 47 whole rocks extent and depth of melting Na8 and Fe8 respectively and melt pristinity Mg of the magma indicate that rocks along this stretch were probably sourced from a reasonably primitive melt generated at a relatively greater depth and later got accumulated in pockets at a shallower level before eruption Petrochemical analysis and isotopic composition and ratios suggest that in contrast to largely NMORB type of rocks at RCFV and OSC areas the rocks from LTD and NVZ locations show signatures of enrichment to transitional T and enriched E basalts A model explaining possible processes of enrichment and ascending framework of the melt at different tectonic regimes along SCIR are discussedThis work was carried out under India’s InRidge Program and was supported by grants from the Office of Naval Research ONRUSA Grant N0014 The whole rock and glass were analysed at the University of Hawaii RM acknowledges the support of Rodey Batiza and to the late John J Mahoney during his stay at the SOEST UH Manoa We place on record our sincere thanks to one anonymous reviewer Dr Brian Dreyer and to Prof WolfChristian Dullo editorinchief for their meticulous comments and guidance that helped immensely to improve the manuscript This is NIO contribution 5752

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