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The 2005-2006-eruption of the Barren Volcano, Andaman Sea: Evolution of basaltic magmatism in island arc setting of Andaman-Java subduction complex
T. Pal, S. Raghav, A. Bhattacharya, P.C. Bandopadhyay, S.K. Mitra, M.L. Renjit, M.S. Sankar,
Published in
Volume: 39
Issue: 1-2
Pages: 12 - 23
The Barren Volcano located in the volcanic chain of Burma-Java subduction complex became active during 2005-2006 initially as Strombolian and later on as sub-Plinian type ejecting out ash laden grey smoke and coarse pyroclasts. The pyroclasts are represented by vesiculated (20-30. vol.% vesicle) porphyritic basaltic rock where the phenocrysts constituting 20-25. vol.% of the total bulk are represented by plagioclase (18-25. vol.%), olivine (1-4%), clinopyroxene (0.5-2.5. vol.%) and few iron oxides. Olivine of the 2005-lava shows a variation in Fo content from core (Fo81-85) to rim (Fo73-75) but those in the 2006-lava show a uniform composition from core to rim (Fo75-78). Feldspar grains of both the 2005 and 2006-eruptions are normally zoned, with a variation from core (An93-80) to rim (An76-55). The major oxides show basaltic composition for the 2005-lava and basaltic to basaltic andesite for the 2006-lava. Abundances of plagioclase phenocrysts, poorly hydrous glass inclusions in the phenocrysts, rarity of the mafic phase and high Zr content (69-75ppm) are suggestive of the very poorly hydrous nature of magma. The calculated fractional crystallisation trend show the differences in the 2005-lava and 2006-lava where the former show accumulated nature and the latter indicates evolved path. The major oxides and trace elements patterns indicate that both the lava had a different parental composition and the 2006-lava was subjected to fractional crystallisation. The magmatic evolution is explained by the mantle diapir model where the almost anhydrous basaltic magma of the 2005-eruption was produced from hot rind of the diapir and feebly hydrous basaltic andesite magma of the 2006-eruption was formed from cool and wet core of the diapir. © 2010 Elsevier Ltd.
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JournalJournal of Asian Earth Sciences