| 北山地区早古生代洋盆俯冲记录——来自石板井高镁闪长岩的年代学、地球化学证据 |
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| 引用本文： | 专少鹏,陈超,申宗义,潘志龙,张运强,赵华平,陈宏强,杨瑞,修迪.北山地区早古生代洋盆俯冲记录——来自石板井高镁闪长岩的年代学、地球化学证据[J].岩石矿物学杂志,2018,37(4):533-546. |
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| 作者姓名： | 专少鹏 陈超 申宗义 潘志龙 张运强 赵华平 陈宏强 杨瑞 修迪 |
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| 作者单位： | 河北省区域地质调查院 |
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| 基金项目： | 中国地质调查局地质调查项目（12120114064101） |
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| 摘 要： | 北山造山带中部石板井地区发育高镁闪长岩体。LA-ICP-MS锆石U-Pb分析获得该类岩石的年龄为456±2Ma,表明其形成于晚奥陶世。地球化学数据显示:岩石属钠质钙碱性系列,SiO_2含量为51.94%~55.30%,具有较高的MgO(4.12%~6.19%,平均5.17%)、Mg#值(0.45~0.69,平均0.53)、Cr(35.82×10~(-6)~985.50×10~(-6),平均284.84×10~(-6))、Ni(20.93×10~(-6)~148.59×10~(-6),平均70.23×10~(-6))含量,稀土元素配分曲线均呈平缓右倾,轻稀土元素略相对富集,富集大离子亲石元素(LILE)(如Rb、Ba、Th、U、K),亏损高场强元素(HFSE)(如Ta、Nb、P、Ti)。这些特征类似于日本西南新生代Setouchi火山岩带赞岐岩。通过岩石成因分析,认为该岩体很可能由俯冲洋壳和沉积物部分熔融产生的含水流体与地幔橄榄岩相互作用形成,进而揭示其形成于岛弧环境。这表明红柳河-牛圈子-洗肠井古洋盆在晚奥陶世仍在向北俯冲,哈萨克斯坦板块和塔里木板块最终的拼合时间可能在奥陶纪之后。
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| 关 键 词： | 高镁闪长岩 锆石U-Pb定年 岩石成因 构造环境 北山地区 |
| 收稿时间： | 2017/10/18 0:00:00 |
Early Paleozoic subduction of the ocean in Beishan region: Zircon U-Pb geochronological and geochemical evidence from the high-Mg diorite in the Shibanjing area |
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| ZHUAN Shao-peng,CHEN Chao,SHEN Zong-yi,PAN Zhi-long,ZHANG Yun-qiang,ZHAO Hua-ping,CHEN Hong-qiang,YANG Rui and XIU Di.Early Paleozoic subduction of the ocean in Beishan region: Zircon U-Pb geochronological and geochemical evidence from the high-Mg diorite in the Shibanjing area[J].Acta Petrologica Et Mineralogica,2018,37(4):533-546. |
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| Authors: | ZHUAN Shao-peng CHEN Chao SHEN Zong-yi PAN Zhi-long ZHANG Yun-qiang ZHAO Hua-ping CHEN Hong-qiang YANG Rui and XIU Di |
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| Institution: | Institute of Regional Geological and Mineral Resource Survey of Hebei Province, Langfang 065000, China,Institute of Regional Geological and Mineral Resource Survey of Hebei Province, Langfang 065000, China,Institute of Regional Geological and Mineral Resource Survey of Hebei Province, Langfang 065000, China,Institute of Regional Geological and Mineral Resource Survey of Hebei Province, Langfang 065000, China,Institute of Regional Geological and Mineral Resource Survey of Hebei Province, Langfang 065000, China,Institute of Regional Geological and Mineral Resource Survey of Hebei Province, Langfang 065000, China,Institute of Regional Geological and Mineral Resource Survey of Hebei Province, Langfang 065000, China,Institute of Regional Geological and Mineral Resource Survey of Hebei Province, Langfang 065000, China and Institute of Regional Geological and Mineral Resource Survey of Hebei Province, Langfang 065000, China |
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| Abstract: | The high-Mg diorites occur in the Shibanjing area of central Beishan orogenic belt and are dated at 456±2 Ma by the LA-ICP-MS zircon U-Pb method, which indicates that they were generated in the Late Ordovician. According to geochemical data, the high-Mg diorites belong to the sodic calc-alkaline series, the content of SiO2 is 51.94%~55.30%. They are geochemically characterized by high MgO (4.12%~6.19%, avg. 5.17%), Mg# (0.45~0.69, avg. 0.53), Cr (35.82×10-6~985.50×10-6, avg. 284.84×10-6), and Ni (20.93×10-6~148.59×10-6, avg. 70.23×10-6), and also exhibit nearly flat right-declined REE patterns with slight enrichment of LREE. The high-Mg diorites are strongly enriched in large-on-lithophile elements such as Rb, Ba, Th, U and K, and are characterized by depletion of high-field-strength elements such as Nb, Ta, P and Ti. These geochemical features are analogous to those of Cenozoic Setouchi volcanic belt in southwestern Japan. Petrogenesis analysis shows that the rock mass was probably formed by the interaction between the aqueous fluid produced by partial melting of subducted oceanic crust and sediments and the mantle peridotite, suggesting that it was formed in an island arc environment. It is thus concluded that the Hongliuhe-Niuquanzi-Xichangjing ancient ocean plate was presumably in the process of subduction during the late Ordovician, and the collision between Kazakhstan plate and the Tarim plate might have occurred after Ordovician. |
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| Keywords: | high-Mg diorite LA-ICP-MS zircon U-Pb dating petrogenesis tectonic setting Beishan region |
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