Geochemical characteristics of island-arc volcanic rocks in the Nan-Nam Pat-Phetchabun zone,northern Thailand  

作　　者：SHEN Shangyue FENG Qinglai YANG Wenqiang ZHANG Zhibin Chongpom Chonglakmani 

机构地区：[1]State Key Laboratory of GPMR, China University of Geology, Hubei, Wuhan 430074, China [2]Institute of Regional Geology, Yunnan Bureau of Geology and Mineral Resources, Yunnan, Yuxi 653110, China [3]School ofGeotechnology, Suranaree University of Technology, Thailand

出　　处：《Chinese Journal Of Geochemistry》2010年第4期337-342,共6页中国地球化学学报

基　　金：the National Natural Science Foundation of China (Grant Nos. 40372105 and 40772143)

摘　　要：Late Permian-Early Triassic(P2-T1) volcanic rocks distributed on the eastern side of ocean-ridge and oceanic-island basalts in the Nan-Uttaradit zone were analyzed from aspects of petrographic characteristics,rock assemblage,REE,trace elements,geotectonic setting,etc.,indicating that those volcanic rocks possess the characteristic features of island-arc volcanic rocks.The volcanic rock assemblage is basalt-basaltic andesite-andesite.The volcanic rocks are sub-alkaline,dominated by calc-alkaline series,with tholeiite series coming next.The chemical composition of the volcanic rocks is characterized by low TiO2 and K2O and high Al2O3 and Na2O.Their REE patterns are of the flat,weak LREE-enrichment right-inclined type.The trace elements are characterized by the enrichment of large cation elements such as K,Rb and Ba,common enrichment of U and Th,and depletion of Nb,Ta,Zr and Hf.The petrochemical plot falls within the field of volcanic rocks,in consistency with the plot of island-arc volcanic rocks in the Jinsha River zone of China.This island-arc volcanic zone,together with the ocean-ridge/oceanic island type volcanic rocks in the Nan-Uttaradit zone,constitutes the ocean-ridge volcanic rock-island-arc magmatic rock zones which are distributed in pairs,indicating that the oceanic crust of the Nan-Uttaradit zone once was of eastward subduction.This work is of great significance in exploring the evolution of paleo-Tethys in the Nan-Uttaradit zone.Late Permian-Early Triassic（P2-T1） volcanic rocks distributed on the eastern side of ocean-ridge and oceanic-island basalts in the Nan-Uttaradit zone were analyzed from aspects of petrographic characteristics,rock assemblage,REE,trace elements,geotectonic setting,etc.,indicating that those volcanic rocks possess the characteristic features of island-arc volcanic rocks.The volcanic rock assemblage is basalt-basaltic andesite-andesite.The volcanic rocks are sub-alkaline,dominated by calc-alkaline series,with tholeiite series coming next.The chemical composition of the volcanic rocks is characterized by low TiO2 and K2O and high Al2O3 and Na2O.Their REE patterns are of the flat,weak LREE-enrichment right-inclined type.The trace elements are characterized by the enrichment of large cation elements such as K,Rb and Ba,common enrichment of U and Th,and depletion of Nb,Ta,Zr and Hf.The petrochemical plot falls within the field of volcanic rocks,in consistency with the plot of island-arc volcanic rocks in the Jinsha River zone of China.This island-arc volcanic zone,together with the ocean-ridge/oceanic island type volcanic rocks in the Nan-Uttaradit zone,constitutes the ocean-ridge volcanic rock-island-arc magmatic rock zones which are distributed in pairs,indicating that the oceanic crust of the Nan-Uttaradit zone once was of eastward subduction.This work is of great significance in exploring the evolution of paleo-Tethys in the Nan-Uttaradit zone.

关 键 词：岛弧火山岩 地球化学特征 Al2O3含量 岩石学特征 洋岛玄武岩 玄武安山岩 钙碱性系列 泰国 

分 类 号：P588.14[天文地球—岩石学] P618.51[天文地球—地质学]