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班公湖中特提斯洋向南俯冲的时限:来自SSZ型辉长岩的制约 被引量:8
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作者 梁桑 周涛 +4 位作者 李德威 陈超 郝海健 胡维云 李华亮 《大地构造与成矿学》 EI CAS CSCD 北大核心 2017年第5期989-1000,共12页
班公湖-怒江中特提斯洋的俯冲极性和俯冲时间一直存在争议。作者通过野外地质调查、岩相学、锆石U-Pb年代学及岩石地球化学研究,从西藏班公湖蛇绿混杂岩带中识别出一套早白垩世SSZ型蛇绿岩,岩石组合上主要由辉长岩和玄武岩组成,还有少... 班公湖-怒江中特提斯洋的俯冲极性和俯冲时间一直存在争议。作者通过野外地质调查、岩相学、锆石U-Pb年代学及岩石地球化学研究,从西藏班公湖蛇绿混杂岩带中识别出一套早白垩世SSZ型蛇绿岩,岩石组合上主要由辉长岩和玄武岩组成,还有少量的硅质岩和超基性岩。本文对辉长岩进行了全岩主、微量元素地球化学及LA-ICP-MS锆石U-Pb年代学研究。地球化学组成特征显示,辉长岩富集轻稀土元素,重稀土元素平坦,相对富集大离子亲石元素,高场强元素存在一定亏损;Th/Ta比值与岛弧玄武岩相似(Th/Ta>1.6),Ta/Hf比值较高(>0.1),显示其既保留了俯冲环境的地球化学特征,也提供了伸展构造环境的信息。辉长岩中锆石U-Pb加权平均年龄为129.2±0.4 Ma(MSWD=0.36),该年龄是班公湖-怒江缝合带中迄今报道的最年轻蛇绿岩年龄。结合区域地质背景,认为这套蛇绿岩形成于班公湖-怒江古洋盆西段向南俯冲形成的弧前盆地,而班公湖-怒江古洋盆北向俯冲可能始于早侏罗世,晚侏罗世形成双向俯冲格局,直到早白垩世洋盆关闭,晚白垩世进入陆内构造环境。 展开更多
关键词 辉长岩 锆石U-Pb年代学 弧前盆地 向南俯冲 班公湖蛇绿构造混杂岩
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Seismic facies response of tectonics and direction of block movement in the northeastern South China Sea 被引量:1
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作者 陈洁 钟广见 刘少华 《Applied Geophysics》 SCIE CSCD 2010年第4期306-314,399,共10页
The close relationship between the structure,evolution,and resources environment of the South China Sea is a current research focus and also a focal point of our study.In this paper,we use regional seismic sections to... The close relationship between the structure,evolution,and resources environment of the South China Sea is a current research focus and also a focal point of our study.In this paper,we use regional seismic sections to analyze the relationship between seismic facies and the structure and tectonic evolution of the northeastern South China Sea and propose new points about the structure and the direction of block(land mass) motion.First,the tectonic features are clear and can be divided into five different structural units which are both linked and independent of each other.Second,it doesn't matter if the South China Sea basin pattern is extensional,weakly compressive,or strongly compressive,the regional tectonic stress field is unified.For the first time we find that two shallow subduction zones are recognized in the seismic profiles.All the tectonic blocks have accordion-fold-style structures,converging in the east,and the South China Sea exhibits different stages of basin development:growth, maturity,end,and termination.The block subduction and regional block dip directions are all aligned with the regional stress field. 展开更多
关键词 Sea-floor spreading SCS shallow subduction one way drifting extrusion metamorphism accordion-style seismic facies
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