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

Ismail Hossain, Toshiaki Tsunogae, H. M. Rajesh

Research output: Contribution to journalArticle

16 Citations (Scopus)

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, hornblende, biotite, quartz, K-feldspar, titanite, and secondary epidote and chlorite. The calculated P-T conditions of the dioritic rocks are 680-725 °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.% NaCleq) H2O-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 ∼17-22 km, with a minimum average exhumation rate of ∼12-15 m/Ma during Palaeoproterozoic to Lopingian time. Such slow exhumation indicates low relief continental shield surface during this period.

Original languageEnglish
Pages (from-to)731-739
Number of pages9
JournalJournal of Asian Earth Sciences
Volume34
Issue number6
DOIs
Publication statusPublished - May 20 2009

All Science Journal Classification (ASJC) codes

  • Earth-Surface Processes
  • Geology

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