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《Geological Science and Technology Information》 2009-03
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Geochemistry and LA-ICP-MS Zircon U-Pb Age of Basic Dike Swarms in North Daba Mountains and Its Tectonic Significance

WANG Cun-zhi a,b,YANG Kun-guang b,c,XU Yang a,b,CHENG Wan-qiang a,b (a.Graduate School;b.Key Laboratory of Tectonics and Petroleum Resource of Ministry of Education;c.Faculty of Earth Sciences,China University of Geosciences,Wuhan 430074,China)  
Basic dike swarms are widely distributed NW-SE,intruding the Early Paleozoic strata in North Daba Mountains.The geochemistry analysis show that this rock series share similar characteristics of the average mass fraction of continental rift basalt.It is sound that K 2O+Na 2O is concentrated in the major elements with high TiO 2 and rare-earth content.Also the general high rare-earth content is associated with high concentration of light rare-earth and the incompatible large-ion lithophile elements,while the content of Ta and Nb is much higher than MORB.The basic dike swarms crystalline dated(431.0±3.2) Ma by the LA-ICP-MS zircon U-Pb dating.These geochemistry characters and dating above indicate that the basic dike swarms in the study area show the characters of the continental rift basalt.This helps to infer that the extensional tectonics developed constrainedly in the Early Paleozoic by the mantle-source rifting that happened at the boundary of paleocontinent on the northern margin of Yangtze Plate.In the process of rifting,material in the upper mantle uplifts resulted in the extension and thinning of lithospheric plate,generating intense extensional tectonics developed in the middle-upper crust of Daba area and then producing the large group of linear basic dike swarms.The age of(431±3.2) Ma represents the extension of this rift to its peak in Early Silurian.
【Fund】: 中国石油化工股份有限公司勘探南方分公司项目“南大巴构造特征及构造演化研究”(P02009)
【CateGory Index】: P597.3
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