Geothermobarometry and fluid inclusions of dioritic rocks in Bangladesh: Implications for emplacement depth and exhumation rate

Journal article

Authors / Editors

Rajesh, Hariharan

Research Areas

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Publication Details

Author list: Hossain I, Tsunogae T, Rajesh HM

Publisher: Elsevier

Place: OXFORD

Publication year: 2009

Journal: Journal of Asian Earth Sciences (1367-9120)

Journal acronym: J ASIAN EARTH SCI

Volume number: 34

Issue number: 6

Start page: 731

End page: 739

Number of pages: 9

ISSN: 1367-9120

eISSN: 1878-5786

Languages: English-Great Britain (EN-GB)

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Abstract

Application of hornblende thermobarometry and fluid inclusion studies to the Palaeoproterozoic (1.7 Ga) basement rocks from Maddhapara, NW Bangladesh, provide information on the pressure and temperature (P-T) conditions of crystallization, the emplacement depth and composition of magmatic fluid. The basement rocks are predominantly diorite or quartz diorite with a mineral assemblage of plagioclase, homblende, biotite, quartz, K-feldspar, titanite, and secondary epidote and chlorite. The calculated P-T conditions of the dioritic rocks are 680-725 degrees C and 4.9-6.4 kbar, which probably correspond to crystallization conditions. Fluid inclusion studies suggest that low-to medium-salinity (0-6.4 wt.% NaCl(eq)) Homblende thermobarometry H(2)O-rich fluids are trapped during the crystallization of quartz and plagioclase. The isochore range calculated for primary aqueous inclusions is consistent with the P-T condition obtained by geothermobarometry. The basement rocks likely crystallized at a depth of similar to 17-22 km, with a minimum average Basement rocks exhumation rate of similar to 12-15 m/Ma during Palaeoproterozoic to Lopingian time. Such slow exhumation Palaeoproterozoic indicates low relief continental shield surface during this period. (C) 2008 Elsevier Ltd. All rights reserved.

Keywords

Bangladesh, Basement rocks, Emplacement depth, Exhumation rate, fluid inclusion, Hornblende thermobarometry, Lopingian, Palaeoproterozoic

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