Geochemistry of ophiolite cherts from the Qinling orogenic belt and implications for their tectonic settings

作     者：ZHANG Chengli GAO Shan ZHANG Guowei GUO Anlin YUAN Honglin LIU Xiaoming WANG Jianqi 

作者机构：The key Laboratory of Continental DynamicsMinistry of EducationDepartment of GeologyNorthwest UniversityXian 710069 China State Key Laboratory for Mineral Deposits ResearchNanjing UniversityNanjing 210093China Department of GeochemistryChina University of GeosciencesWuhan 430074China 

出 版 物：《Science China Earth Sciences》 (中国科学（地球科学英文版）)

年 卷 期：2004年第47卷第4期

页      面：329-337页

核心收录：

学科分类：070902[理学-地球化学] 0709[理学-地质学] 07[理学] 

基　　金：This project was jointly supported by the NationalNatural Science Foundation of China (Grant Nos. 40372039,40032010-C, 40133020 and 49732080) the Foundations of Senior Visiting Scholarship of Colleges in Western areas and Backbone Teacher of Ministry of Education, China (Grant No. 2000-143) 

主　　题：Qinling orogenic belt radiolarian cherts ophiolite m閘ange zone. 

摘      要：Paleozoic cherts from the Mianl and the Erlangping ophiolite zones of the Qinling orogenic belt are characterized by low Si/Al ratios (52.14-683.52 in the Mianle cherts, 12.29-58.62 in the Erlangping cherts), Fe2O3 (0.01-0.35 and 0.02-1.24) and high Al2O3/(Al2O3+Fe2O3) ratios (0.82-0.99 and 0.83-0.99). The negative correlation between Si2O and Al2O3 in the cherts reflects the important role of terrigenous components. The Erlangping cherts have Lan/Cen=0.9-1.15 and Ce/Ce*=0.95-1.15 with low contents of V, Ni and Cu, consistent with those of cherts forming on the continental margin. In contrast, the Ce/Ce* ratios of the Mianle cherts range from 0.71 to 1.18 and Lan/Cen from 0.88 to 1.43 with slightly high V, Ni and Cu, which are similar to cherts found in the mid-ocean ridges and pelagic basins. Combined with the features of basic lavas associated with the cherts, it is suggested that during the Paleozoic, when the back-arc basin represented by the Erlangping ophiolite commenced shrinking in size in the mid-Ordovician, the southern Qinling was still in an extensional regime and finally grew into a new limited oceanic basin in the early Carboniferous.