Geochemical characteristics of Bikou volcanic group and Sr-Nd-Pb isotopic composition: Evidence for breakup event in the north margin of Yangtze plate, Jining era  

作　　者：LI YongFei LAI ShaoCong QIN JiangFeng LIU Xin WANG Juan 

机构地区：[1]State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi'an 710069, China State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi'an 710069, China State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi'an 710069, China State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi'an 710069, China State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi'an 710069, China

出　　处：《Science China Earth Sciences》2007年第z2期339-350,共12页中国科学（地球科学英文版）

基　　金：Supported by the National Natural Science Foundation of China (Grant Nos. 40234041 and 40272042)

摘　　要：The geodynamic setting of the Bikou volcanic group is a critical question to trace the Precambrain tectonic framework and evolution for the Yangtze plate. This study has suggested that the Bikou volcanic group is composed of several residual oceanic crust units: MORB (mid-ocean ridge basalt), Alk-OIB (alkaline ocean island basalt) and Th-OIB (tholeiitic ocean island basalt) as well as subduction-related volcanic rocks. According to field observation, those distinct rocks occurred collectively in form of tectonic contact, implying that the Bikou volcanic group was an ophiolitic mélange. Coupled with geochronological data, a perished oceanic basin at the northern margin of the Yangtze block during Neoproterozoic was tested by this ophiolitic mélange. Meanwhile, the isogeochemical data suggest that the ocean occurred in the Southern Hemisphere identical to Indian, South Atlantic and South Pacific oceans in terms of their Dupal anomalies, and the original source of the rocks could be probably mixing by EMⅠand EMⅡ component caused by dehydration melting of subducting oceanic crust during subduction process. On the basis of geochemical characteristics of the studied rocks, the Bikou volcanic group could imply that a partial breakup event occurred in the northern margin of Yangtze plate during the Neoproterozoic era.

关 键 词：Bikou VOLCANIC group  ophiolitic mélange  geochemistry  Dupal anomaly  Neoproterozoic  Yangtze plate 

分 类 号：N[自然科学总论]