Provenance analysis of the Oligocene turbidites (Andaman Flysch), South Andaman Island: A geochemical approach

Journal of Earth system science

P C Bandopadhyay1¹  Biswajit Ghosh1¹ 

[1]Department of Geology, University of Calcutta, 35 Ballygunge Circular Road, Kolkata 700 019, India.$$

关键词: Andaman Flysch;    geochemistry;    provenance;    Corbyn’s Cove;    South Andaman Island.;   

DOI  :  

学科分类：天文学(综合)

来源: Indian Academy of Sciences

【 摘 要 】

The Oligocene-aged sandstone-shale turbidites of the Andaman Flysch are best exposed along the east coast of the South Andaman Island. Previously undocumented sandstone-shale geochemistry, investigated here, provides important geochemical constraints on turbidite provenance. The average 70.75 wt% SiO2, 14.52 wt% Al2O3, 8.2 wt% Fe2O$^{ext{t}}_{3}$+MgO and average 0.20 Al2O3/SiO2 and 1.08 K2O/Na2O ratios in sandstones, compare with quartzwackes. The shale samples have average 59.63 wt% SiO2, 20.29 wt% Al2O3, 12.63 wt% Fe2O$^{ext{t}}_{3}$+MgO and average 2.42 K2O/Na2O and 0.34 Al2O3/SiO2 ratios. Geochemical data on CaO–Na2O–K2O diagram fall close to a granite field and on K2O/Na2O–SiO2 diagram within an active continental margin tectonic setting. The range and average values of Rb and Rb/Sr ratios are consistent with acid-intermediate igneous source rocks, while the values and ratios for Cr and Ni are with mafic rocks. Combined geochemical, petrographic and palaeocurrent data indicate a dominantly plutonic-metamorphic provenance with a lesser contribution from sedimentary and volcanic source, which is possibly the Shan–Thai continental block and volcanic arc of the north-eastern and eastern Myanmar. Chemical index of alteration (CIA) values suggests a moderate range of weathering of a moderate relief terrane under warm and humid climate.

【 授权许可】

Unknown