The Discovery of OIB-Type Potassic Tholeiitic Basalts from the Ganjia Area in West Qinling: Implications for the Late Mesozoic Continental Rift of West Qinling
详细信息
- 责任者：Huang Xiongfei (State Key Laboratory of Geological Processes and Mineral Resources ; School of Earth Sciences and Resources ; China University of Geosciences ; Beijing 100083 ; China) ; Yu Xuehui
- 刊名：Earth Science Frontiers
- 出版年：2013
- 卷期：20(3)
- 关键词：拉斑玄武岩 ; tholeiitic basalt ; 洋岛玄武岩 ; ocean-island basalts ; 秦岭 ; Qinling Mountains
- 页码：p.204-216
- 图表：illus., 3 tables, 54 refs.
- 分类号：0801
- issnNo：ISSN1005-2321
- isbnNo：CN11-3370/P
摘要
The Late Mesozoic volcanic rocks of West Qinling Area exposed in the Duofutun Area of Zeku County,Qinghai Province and the Hongqiang and Ganjia areas of Xiahe County,Gansu Province.Preliminary study showed that the Ganjia volcanic rocks belong to potassic tholeiitic basalts.The rocks are enriched in REE,LILE and HFSE,but the fractionation degree of LREE and HREE and the incompatible element contents are slightly lower than those of typical OIB and the Late Mesozoic sodic alkaline basalts of West Qinling.The magma of these basaltic rocks were originated from the lithosphere metasomatized by small-volume,volatiles-enriched,asthenosphere-derived silicate melts and had undergone a large degree of fractional crystallization of mafic minerals.These K-tholeiitic basalts,bearing the typical petrogenetic characteristics of intracontinental OIB,not only differ from the Ganjia seamount basalts suggested by previous authors,but also are not the member of the "Permian Longwuxia-Ganjia ophiolite".These rocks together with the Late Mesozoic sodic alkaline basalts of West Qinling are both the products of the OIB-type magmatism in the Late Mesozoic continental rift system of West Qinling.The Ganjia basalts may have a more complex assemblage of different basaltic rocks,and have a longer time span from the Late Paleozoic to the Late Mesozoic.The Late Mesozoic continental rift of West Qinling died young in the early stage of the lithospheric extension,whose occurrence and the widespread development of the near-SN or NW faults in the studied area,may be the performance of the interaction and reworking of the complexly superimposed Helan-Sichuan-Yunnan N-S trending tectonic belt with the large scale strike-slip fault system.
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