Geochemistry of Middle Triassic Radiolarian Cherts from Northern Thailand:Implication for Depositional Environment

查看全文 作　　者：Hathaithip [1]Thassanapak;Mongkol [2]Udchachon;Chongpan [3]Chonglakmani;[4]冯庆来

机构地区：[1]Department of Biology,Faculty of Science,Mahasarakham University;[2]Palaeontological Research and Education Centre,Mahasarakham University;[3]School of Geotechnology,Institute of Engineering,Suranaree University of Technology;[4]State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences

出　　处：《Journal of Earth Science》索引2011年第22卷第6期,共16页

基　　金：supported mainly by the National Natural Science Foundation of China (No. 40772143);the Special Fund of the State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences;the Faculty of Science,Mahasarakham University 摘　　要：Geochemical analysis reveals that Middle Triassic radiolarian cherts from northern Thailand,including Chiang Dao,Lamphun and Den Chai,are of biogenic origin.These cherts present slightly high SiO2 content which was possibly modified by diagenetic alteration and migration processes as indicated by negative correlation between SiO2 and most of the other major elements.The relatively high content of Cr,Zr,Hf,Rb and Th and high positive correlation of these elements with Al and Ti from the majority of cherts suggest a close relation to terrigenous component.The Ce anomaly(Ce/Ce*) with geometric means ranging from 0.85 to 0.93 is compatible with that of continental margin composition(0.67-1.52) from Murray et al.(1990) which is also consistent with low Eu anomalies(Eu/Eu*,0.91-0.94).Moreover,the slightly low ratios of La and Ce NASC normalized(Lan/Cen,0.91-0.94) and the low LREE and HREE ratios in most of our samples(Lan/Ybn,0.62-0.85) are in agreement with the continental margin.The result from Lan/Cen vs.Al2O3/(Al2O3+Fe2O3) discrimination diagrams also supports the continental margin(residual basin,s.str.) interpretation.These geochemical results are compatible with geological evidence,which suggest that during the Middle Triassic,radio-larian cherts were deposited within a deeper part of a residual basin in which an accommodation space was possibly controlled by faults under extensional regime subsequent to Late Variscan(Permian) orogeny.Paleogeographi-cally,the main Paleotethys which closed during Late Triassic should be located further to the west of these study localities.This scenario is in agreement with the current view of the Tethys in this part of the world. 关键词：放射虫硅质岩中三叠世地球化学特征沉积环境泰国 SIO2含量铝/氧化铝地球化学分析

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Geochemistry of Middle Triassic Radiolarian Cherts from Northern Thailand:Implication for Depositional Environment

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