| 藏北双湖鄂柔地区变质岩和玄武岩的~(40)Ar/~(39)Ar年龄及其意义 |
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| 引用本文： | 王立全,潘桂棠,朱弟成,朱同兴,林仕良,李宗亮.藏北双湖鄂柔地区变质岩和玄武岩的~(40)Ar/~(39)Ar年龄及其意义[J].地学前缘,2006,13(4):221-232. |
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| 作者姓名： | 王立全 潘桂棠 朱弟成 朱同兴 林仕良 李宗亮 |
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| 作者单位： | 成都地质矿产研究所,四川,成都,610082 |
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| 基金项目： | 国家研究发展基金;国家高技术研究发展计划(863计划);中国地质调查局资助项目 |
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| 摘 要： | 在藏北龙木错—双湖缝合带东段双湖鄂柔地区,获得绿泥阳起石片岩中阳起石矿物的40Ar/39Ar坪年龄为(235·9±2·6)Ma和枕状玄武岩中蚀变辉石斑晶的40Ar/39Ar坪年龄为(232·5±2·4)Ma,两个年龄具有极好的一致性,记录了中三叠世晚期—晚三叠世早期沿龙木错—双湖缝合带发生俯冲碰撞作用的构造-热事件。羌塘地区中三叠世晚期—晚三叠世早期的俯冲碰撞造山事件使得龙木错—双湖缝合带及其以北的大部分地区(即北羌塘盆地)转变为前陆盆地,区域上三叠统底部不整合面和底砾岩的发育是碰撞造山作用地质记录的重要标志。绿泥阳起石片岩的原岩主要为富含玄武岩的火山-沉积岩系,绿泥阳起石片岩和蚀变枕状玄武岩具有Ti O2、P2O5、MgO含量较高和LREE富集型、无Eu异常,以及“大隆起”微量元素配分模式和富集Nb、Ta、Ti元素等地球化学特征,显示为较典型的洋岛型碱性玄武岩性质。
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| 关 键 词： | 龙木错—双湖缝合带 绿泥阳起石片岩 蚀变枕状玄武岩 40Ar/39Ar年龄测定 俯冲碰撞作用 |
| 文章编号： | 1005-2321（2006）04-0221-12 |
| 收稿时间： | 2006-05-20 |
| 修稿时间： | 2006-06-19 |
40Ar/39Ar ages of the metamorphic rocks and basalts in E'rou area of Shuanghu, northern Xizang and their significance |
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| WANG Li-quan,PAN Gui-tang,ZHU Di-cheng,ZHU Tong-xing,LIN Shi-liang,LI Zong-liang.40Ar/39Ar ages of the metamorphic rocks and basalts in E''''rou area of Shuanghu, northern Xizang and their significance[J].Earth Science Frontiers,2006,13(4):221-232. |
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| Authors: | WANG Li-quan PAN Gui-tang ZHU Di-cheng ZHU Tong-xing LIN Shi-liang LI Zong-liang |
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| Abstract: | Actinolite and pyroxene phenocrysts separated respectively,from chlorite-actinolite schist and altered pillow basalt in the E'rou area of the eastern part of the Shuanghu-Longmuco suture zone, yield well-defined ~ 40 Ar/~ 39 Ar plateau ages of 235.9±2.6 Ma and 232.5±2.4 Ma. These nearly identical ages are interpreted as defining the age of the tectonothermal event of subduction-related collision along the Shuanghu-Longmuco suture zone. Collision in the Qiangtang region led to the greater part of the Shuanghu-Longmuco suture zone and its northern flank (i.e., the northern Qiangtang basin) becoming a foreland basin during the late Middle Triassic to early Late Triassic. The regional unconformity at the base of the Upper Triassic, and the conglomerate above it are important geological indicators of this collisional orogenesis. The protoliths of the chlorite-actinolite schist were mainly volcanic-sedimentary rocks enriched in basalt. The chlorite-actinolite schist and the altered pillowbasalt are characterized by high contents of TiO_2, P_2O_5 and MgO, LREE-enriched patterns with negative Eu anomalies, and “tumescence” patterns for trace elements with enrichment in Nb, Ta and Ti;these are typical characteristics of “OIB-type” alkaline basalt. |
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| Keywords: | Shuanghu-Longmuco suture zone chlorite-actinolite schist altered pillow-basalt ~40Ar/~39Ar dating subduction-related collision |
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