Jurassic Intra-plate Basaltic Magmatism in Southeast China:Evidence from Geological and Geochemical Characteristics of the Chebu Gabbroite in Southern Jiangxi Province  

作　　者：XIE Guiqing MAO Jingwen HU Ruizhong LI Ruiling JIANG Guohao CAO Jinjian ZHAO Junhong 

机构地区：[1]State Key Laboratory of Geological Process and Mineral Resourses, China University of Geosciences, Beijing 100083 [2]Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037 [3]Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, Guizhou 550002 [4]Earth Science Department, Sun Yat-Sun University, Guangzhou, Guangdong 510275Earth Science Department, Sun Yat-Sun University, Guangzhou, Guangdong 510275

出　　处：《Acta Geologica Sinica(English Edition)》2005年第5期662-672,共11页地质学报（英文版）

基　　金：supported jointly by the National National Science Foundation of China(Grant Nos 40402011 and 40434011);China Postdoctoral Science Foundation and Chinese Academy of Sciences(KZCX3-SW-125);the Ministry of Science and Technology of China(G1999043211)

摘　　要：Geochemical and isotopic investigations have been carded out on the Chebu gabbroite in southern Jiangxi Province, southeast China and these results are compared with gabbro bodies along the coast of Fujian Province in order to understand their magma sources and tectonic implications. The Chebu intrusion formed at the beginning of the Middle Jurassic （172~4.3 Ma）. These rocks are Ti-rich and Al-poor in major elements, characterized by strong enrichment in large-ion lithophile elements （LILE） and moderate enrichment in high field strength elements （HFSE） and light rare-earth elements CLREE）, without pronounced Nb or Ta anomalies. Age-correlated Sr-Nd isotope ratios show moderately high ranges of （^87Sr/^86Sr）i from 0.7065 to 0.7086 and 0.5124 to 0.5125 of （^143Nd/^144Nd）i. The geochemical characteristics of the Chebu gabbroite suggest that it is notably different from island-arc basalt and similar to intra-plate basaltic rocks. By combining interpretations of its geological and geochemical characteristics and the regional geological development history, the Chebu gabbroitic intrusion is thought to be the product of asthenosphere upwelling and rapid lithosphere extension during a transition of tectonic systems in southeast China. The tectonic environment and source characteristics of the intrusion are different from Cretaceous gabbro bodies along the coast of Fujian Province, The former formed in a tectonic environment of rapid intra-plate lithospheric extension and the source characteristics were of a weakly enriched primitive mantle, whereas the latter originated mainly in a volcanic-magmatic arc extensional tectonic environment and the nature of the source was an enriched mantle with more subduct subducted components.Geochemical and isotopic investigations have been carded out on the Chebu gabbroite in southern Jiangxi Province, southeast China and these results are compared with gabbro bodies along the coast of Fujian Province in order to understand their magma sources and tectonic implications. The Chebu intrusion formed at the beginning of the Middle Jurassic （172~4.3 Ma）. These rocks are Ti-rich and Al-poor in major elements, characterized by strong enrichment in large-ion lithophile elements （LILE） and moderate enrichment in high field strength elements （HFSE） and light rare-earth elements CLREE）, without pronounced Nb or Ta anomalies. Age-correlated Sr-Nd isotope ratios show moderately high ranges of （^87Sr/^86Sr）i from 0.7065 to 0.7086 and 0.5124 to 0.5125 of （^143Nd/^144Nd）i. The geochemical characteristics of the Chebu gabbroite suggest that it is notably different from island-arc basalt and similar to intra-plate basaltic rocks. By combining interpretations of its geological and geochemical characteristics and the regional geological development history, the Chebu gabbroitic intrusion is thought to be the product of asthenosphere upwelling and rapid lithosphere extension during a transition of tectonic systems in southeast China. The tectonic environment and source characteristics of the intrusion are different from Cretaceous gabbro bodies along the coast of Fujian Province, The former formed in a tectonic environment of rapid intra-plate lithospheric extension and the source characteristics were of a weakly enriched primitive mantle, whereas the latter originated mainly in a volcanic-magmatic arc extensional tectonic environment and the nature of the source was an enriched mantle with more subduct subducted components.

关 键 词：gabbroite geochemical characteristics geodynamics setting JURASSIC Jiangxi southeast China 

分 类 号：P534.52[天文地球—古生物学与地层学]