Journal
JOURNAL OF VOLCANOLOGY AND GEOTHERMAL RESEARCH
Volume 312, Issue -, Pages 40-52Publisher
ELSEVIER
DOI: 10.1016/j.jvolgeores.2016.01.015
Keywords
Mantle xenoliths; Olivine xenocryst; Alkali basalt; Deccan Trap; Ascent rate
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Funding
- DST [DST/INT/US-NSF/RPO-144/03]
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Kutch rift basin of northwestern India is characterized by a topography that is controlled by a number of fault controlled uplifted blocks. Kutch Mainland Uplift, the largest uplifted block in the central part of the basin, contains alkali basalt plugs and tholeiitic basalt flows of the Deccan age. Alkali plugs often contain small, discoidal mantle xenoliths of spinel lherzolite and spinel wehrlite composition. Olivine occurs as xenocrysts (coarse, fractured, broken olivine grains with embayed margin; Fo(>90)), phenocrysts (euhedral, smaller, and less forsteritic similar to Fo(80)), and as groundmass grains (small, anhedral, Fo(75)) in these alkali basalts. In a few cases, the alkali plugs are connected with feeder dykes. Based on the width of feeder dykes, on the sizes of the xenocrysts and xenoliths, thickness of alteration rim around olivine xenocryst, we estimate that the alkali magmas erupted at a minimum speed of 0.37 km per hour. The speed was likely greater because of the fact that the xenoliths broke up into smaller fragments as their host magma ascended through the lithosphere. (C) 2016 Elsevier B.V. All rights reserved.
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