地学前缘 ›› 2010, Vol. 17 ›› Issue (3): 44-52.

• 论文 • 上一篇    下一篇

昌宁—孟连缝合带乌木龙—铜厂街洋岛型火山岩地球化学特征及其大地构造意义

赖绍聪, 秦江锋, 李学军, 臧文娟   

  1. 西北大学 大陆动力学国家重点实验室; 西北大学 地质学系,  陕西 西安 710069
  • 收稿日期:2009-12-10 修回日期:2010-01-28 出版日期:2010-05-15 发布日期:2010-06-18
  • 作者简介:赖绍聪(1963—),男,教授,博士生导师,岩石学及地球化学专业。Email: shaocong@nwu.edu.cn
  • 基金资助:

    陕西省教育厅省级重点实验室科研与建设计划项目(08JZ62);西北大学大陆动力学国家重点实验室科技部专项;国家自然科学基金项目(40872060)

 Geochemistry of the OIBtype basalt from the WumulongTongchangjie area, ChangningMenglian suture zone：Its petrogenesis and tectonic implications.

 LAI  Chao-Cong, QIN  Jiang-Feng, LI  Hua-Jun, CANG  Wen-Juan   

  1. State Key Laboratory of Continental Dynamics; Department of Geology, Northwest University, Xian 710069, China
  • Received:2009-12-10 Revised:2010-01-28 Online:2010-05-15 Published:2010-06-18

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摘要：

详细的地球化学解析表明,乌木龙—铜厂街地区出露的蛇绿混杂岩主要包括方辉橄榄岩、纯橄榄岩和碱性玄武岩。其中,方辉橄榄岩和纯橄榄岩具有极低的CaO含量(<01％)、稀土总量(<5×10-6)和(La/Yb)N(096～114)值,(Ce/Yb)N为104～137,为轻稀土弱亏损型。本区碱性玄武岩具有高TiO2(257%～333％)、高K2O(229%～552％)的显著特征,(La/Yb)N为1542～1981,(Ce/Yb)N为1248～1476,为轻稀土强烈富集型;岩石Ti/V、Th/Ta、Th/Yb、Ti/Yb、Ta/Yb与来自亏损地幔的MORB以及与俯冲有关的岛弧火山岩明显不同,而主要显示为OIB型火山岩的微量元素地球化学特征,乃是典型的大洋板块内部岩浆作用的产物。该区洋岛型火山岩的厘定,表明昌宁—孟连古洋盆在石炭—二叠纪期间曾经历过一个由初始洋盆到成熟洋盆的完整发育演化过程。

关键词: 地球化学, 洋岛玄武岩, 昌宁&mdash, 孟连缝合带

Abstract:

Ophiolite mélange from the WumulongTongchangjie area, ChangningMenglian tectonic zone mainly consists of ultrabasic and basaltic rocks. The ultrabasic rocks are mainly composed of harzburgite and dunite. They exhibit distinctive geochemical characteristics of extremely low CaO (<01%), low rare earth element content (<5×10-6), (La/Yb)N=096114 and (Ce/Yb)N=104137, showing the depletion of light rare earth elements. The basaltic rocks are alkaline and have high TiO2 (257%333%) and K2O (229%552%) content, as well as high (La/Yb)N=1542～1981 and (Ce/Yb)N=12481476, which show strong enrichment in light rare earth elements. The Ti/V, Th/Ta, Th/Yb, Ti/Yb and Ta/Yb of the alkaline basalt are much similar to that of the typical oceanic island basalt (OIB); while are obviously different from that of the basalts originated from depleted mantle and/or generated by oceanic crust subduction. Therefore, the alkaline basalts in the studied area belong to typical oceanic island basalt (OIB) which was generated by magmatism within oceanic plate. It implies that the ChangningMenglian ancient ocean basin had undergone a whole evolutionary process from initial limited ocean basin to a mature ancient ocean basin.

Key words: geochemistry, oceanic island basalt, ChangningMenglian suture zone

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