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作 者:胡飞 黄蔚 何翔 张克信[2] 骆满生[3] HU Fei;HUANG Wei;HE Xiang;ZHANG Kexin;LUO Mansheng(Guangdong Geologic Survey Institute,Guangzhou,510080;Institute of Geological Survey,China University of Geosciences,Wuhan,430074;State Key Laboratory of Biogeology and Environmental Geology,China University of Geosciences,Wuhan,430074)
机构地区:[1]广东省地质调查院,广州510080 [2]中国地质大学地质调查研究院,武汉430074 [3]中国地质大学生物地质与环境地质国家重点实验室,武汉430074
出 处:《地质论评》2023年第1期199-218,共20页Geological Review
基 金:中国地质调查局项目(编号:12120113056200);广东省地质勘查与城市地质专项(编号:2022-17);国家自然科学基金资助项目(编号:4177020748)的成果。
摘 要:本文报道了分布于兴蒙造山带东北部东乌珠穆沁旗海勒斯台岩体的岩石学、地球化学和年代学特征,以讨论该岩体的形成时代、岩石成因及其构造环境。岩石学研究表明,海勒斯台岩体岩性较为单一,主要为花岗斑岩。LA-ICP-MS锆石U-Pb定年结果显示,海勒斯台花岗斑岩的年龄为463.5±2.0 Ma,表明其形成时代为中奥陶世。花岗斑岩具有富硅(75.14%~77.88%)、富碱(6.15%~7.92%)、低钛(0.15%~0.17%)和铝(11.25%~12.61%)、贫钙(0.18%~1.25%)和镁(0.14%~0.31%),富集大离子亲石元素Rb、Th、K及高场强元素Zr、Hf,强烈亏损Sr、Eu、P、Ti,中等亏损Ba、Nb、Ta等元素,10000Ga/Al值和Zr+Nb+Ce+Y含量较高,属于A2型花岗岩。花岗斑岩的锆石饱和温度介于878~899℃之间,同时具有非常低的Sr和高Yb特征,指示岩石形成于低压高温的伸展构造背景,可能为减薄地壳的部分熔融。结合区域地质资料,认为该花岗斑岩可能形成于古亚洲洋沿着苏尼特左旗—锡林浩特一线向西伯利亚板块俯冲引起的陆缘弧后拉张环境。Objectives and Methods: We present detailed petrography, geochemistry and zircon U-Pb isotopes of the Hailesitai granite porphyry in East Ujimqin Banner, Inner Mongolia, with the aim of determining its age and petrogenesis, important for understanding the early Paleozoic tectonic evolution of the Xing ’ an—Mongolian Orogenic Belt. Resluts: The Petrography feature suggest that Hailesitai pluton mainly consist of granite porphyry. Zircon UPb analyses yield ages of 463. 5 ± 2. 0 Ma for the granite porphyry, indicating that it formed during Middle Ordovician time. The granite porphyry is characterized by high silica, alkali, low titanium and aluminum, lean calcium and magnesium. They are also enriched in large ion lithophile elements( e. g. Rb, Th, K) and high strength field elements(e. g. Zr, Hf) and strongly depleted in Sr, Eu, P, Ti and mediate depleted in Ba, Nb, Ta, with high 10000Ga/Al ratios and Zr + Nb + Ce + Y contents. These features indicate that Hailesitai granite porphyry is A2-type granite.Conclusion: The Saturation temperature of zircon ranges is between 878~899 ℃, and has a very low Sr and high Yb, indicating that the granite porphyry was formed in the extensional tectonic background of low pressure and high temperature and generated by partial melting of the thinning crust. Combined with regional geological background, we infer that the Hailesitai granite porphyry were formed in a back-arc extensional environment of an active continental margin which was resulted from northward subduction of the Paleo-Asian plate beneath the Siberia block along Sonid Zuoqi to Xilinhot.
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