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| 关键词:the volcanic rocks of Yingyangguan Group chronology geochemistry tectonic setting Early Paleozoic eastern Guangxi |
| 基金项目:国土资源部百名优秀青年科技人才计划项目(编号: 200811);广西自然科学基金项目(编号: 2013GXNSFAA019272);广西壮族自治区“新世纪十百千人才工程”专项资金项目(编号: 2006218);桂林理工大学人才引进科研启动基金项目(编号: 002401003364);中国地质调查局地质矿产调查评价项目(编号: 1212011085408);桂林市漓江学者基金项目(编号: 2013-5) |
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| The Reconfirmation of Age and Tectonic Setting of the Volcanic Rocks of Yingyangguan Group in the Eastern Guangxi: Constraints on the Structural Pattern of the Southwestern Segment of Qinzhou–Hangzhou Joint Belt |
| Yingyangguan Group is widely distributed in the junction area of the Hunan, Guangdong and Guangxi Provinces. It consists dominantly of the green schist facies metamorphic spilite, (quartz-) keratophyre and related to volcanic clastic rocks, with small quantities of fine clastic rocks and carbonate rocks. Previously it had been thought that this group formed in a continental rift environment under the background of Rodinia supercontinent breakup during the Neoproterozoic time. The combined petrology, geochemistry and zircon LA-ICP-MS U-Pb dating study reveal that the volcanic rocks of Yingyangguan Group belong primarily to basic-intermediate volcanic(-clastic) rocks, and petrochemically are pronounced enrichment in large-ion incompatible elements (LILEs, e.g., U, Th, Ba, K and Rb) and LREEs and pronounced depletion in high field strength elements (HFSEs, e.g., Nb, Ta, P and Ti) and HREEs. Such signatures display geochemical characteristics of typical subduction-related arc-back arc basin volcanic rocks. A metamorphic keratophyre sample of Yingyangguan Group yielded a zircon LA-ICPMS U-Pb concordia age of (415.1±2.1) Ma (n=13, MSWD=1.8), indicate that it is to be the product of Marine volcanic eruption during Caledonian period. Together with early Paleozoic MORB-type and arc-type metabasic volcanic rocks in the northern margin of Yunkai block, appears to support a development of an early Paleozoic oceanic basin within the southwestern segment of the joint belt between the Yangtze and Cathaysian blocks (so-called Qinzhou-Hangzhou joint belt). Therefore, we conclude that Yingyangguan arc-back arc basin volcanic rocks were likely an important record of the oceanic subduction and subsequent continental collision in the southwestern segment of Qinzhou-Hangzhou joint belt during Early Paleozoic time, and Caledonian structural pattern of the southwestern segment of Qinzhou-Hangzhou joint belt is a subduction-accretion orogenic belt and not an intracontinental orogenic belt. |
| QIN Xiao-feng,WANG Zong-qi,WANG Tao,XIONG Bin,FENG Zuo-hai,YANG Wen,ZHU An-han,SONG Jiong,HUANG Jie.2015.The Reconfirmation of Age and Tectonic Setting of the Volcanic Rocks of Yingyangguan Group in the Eastern Guangxi: Constraints on the Structural Pattern of the Southwestern Segment of Qinzhou–Hangzhou Joint Belt[J].Acta Geoscientica Sinica,36(3):283-292. |
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