【摘 要】
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The Toudaoqiao Complex is a sequence of high-pressure metamorphic rocks located along the suture zone that separates the Xing’an and Erguna blocks in northeast China.The rocks were metamorphosed up to
【机 构】
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College of Earth Sciences,Jilin University,Changchun 130061 China
【出 处】
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2014年中国地球科学联合学术年会
论文部分内容阅读
The Toudaoqiao Complex is a sequence of high-pressure metamorphic rocks located along the suture zone that separates the Xing’an and Erguna blocks in northeast China.The rocks were metamorphosed up to epidote-blueschist facies at P-T conditions of approximately 0.9-1.1 GPa and 320-450℃.Lithological associations and major and trace element compositions indicate that the blueschists are metabasalts with ocean island basalt (OIB) and normal mid-ocean ridge basalt (N-MORB) affinities,similar to those of the Philippines intraoceanic accretionary complex formed by subduction of oceanic crust.Magmatic zircons extracted from two samples of the epidote-blueschist facies metabasalts from the North Mountain in the Toudaoqiao Complex exhibit 206Pb/238U ages of 511 ± 5 and 516 ± 17 Ma,whereas a greenschist from the South Mountain has a 206Pb/238U age of 511 ± 2 Ma; These data show that the protoliths of the Toudaoqiao Complex are of early Paleozoic age.In addition,a granitic dike from the South Mountain exhibits a weighted mean 206Pb/238U age of 492 ± 1 Ma.These ages constrain the timing of high-pressure metamorphism in the Toudaoqiao Complex to 490-510 Ma.The new data support the view that the suture zone between the Xing’an and Erguna blocks is the Toudaoqiao-Xinlin Fault,rather than the Derbugan Fault as previously thought.This suture,which extends from Xinlin,through Toudaoqiao,and southern Mongolia,named the ‘South Mongolia-Toudaoqiao-Xinlin Suture Zone’,may be an important boundary between the Central Mongolia-Erguna and Xing’an blocks.
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