Glass and mineral chemistry of northern central Indian ridge basalts: compositional diversity and petrogenetic significance

Ray, Dwijesh and Banerjee, R. and Iyer, Sridhar D. and Basavalingu, B. and Mukhopadhyay, Subir (2009) Glass and mineral chemistry of northern central Indian ridge basalts: compositional diversity and petrogenetic significance. Acta Geologica Sinica-English Edition, 83 (6). pp. 1122-1135. ISSN 1755-6724

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The glass and mineral chemistry of basalts examined from the northern central Indian ridge (NCIR) provides an insight into magma genesis around the vicinity of two transform faults: Vityaz (VT) and Vema (VM). The studied mid-ocean ridge basalts (MORBs) from the outer ridge flank (VT area) and a near-ridge seamount (VM area) reveal that they are moderately phyric plagioclase basalts composed of plagioclase (phenocryst An(60-90)] and groundmass An(35-79)]), olivine (Fo(81-88)), diopside (Wo(45-51), En(25-37), Fs(14-24)), and titanomagnetite (FeOt similar to 63.75 wt% and TiO2 similar to 22.69 wt%). The whole-rock composition of these basalts has similar Mg# mole Mg/mole(Mg+Fe2+)] (VT basalt: similar to 0.56-0.58; VM basalt: similar to 0.57), but differ in their total alkali content (VT basalt: similar to 2.65; VM basalt: similar to 3.24). The bulk composition of the magma was gradually depleted in MgO and enriched in FeOt, TiO2, P2O5, and Na2O with progressive fractionation, the basalts were gradually enriched in Y and Zr and depleted in Ni and Cr. In addition, the Sigma REE of magma also increased with fractionation, without any change in the (La/Yb)(N) value. Glass from the VM seamount shows more fractionated characters (Mg#: 0.56-0.57) compared to the outer ridge flank lava of the VT area (Mg#: 0.63-0.65). This study concludes that present basalts experienced low-pressure crystallization at a relatively shallow depth. The geochemical changes in the NCIR magmas resulted from fractional crystallization at a shallow depth. As a consequence, spinel was the first mineral to crystallize at a pressure > 10 kbar, followed by Fe-rich olivine at < 10 kbar pressure.

Item Type: Article
Uncontrolled Keywords: mineral chemistry; fractional crystallization; petrogenesis; northern central Indian ridge
Subjects: F Earth Science > Geology
Divisions: Department of > Earth Science
Depositing User: Users 19 not found.
Date Deposited: 28 Aug 2019 10:24
Last Modified: 28 Aug 2019 10:24

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