北祁连西段熬油沟---二只哈拉达坂蛇绿岩的形成环境和时代

北京大学学报（自然科学版）

• 北京大学学报 •

北祁连西段熬油沟---二只哈拉达坂蛇绿岩的形成环境和时代

夏小洪¹,孙楠¹,宋述光¹,肖序常²

1. 北京大学造山带和地壳演化教育部重点实验室, 北京100871; 2. 中国地质科学院地质研究所, 北京100037;

收稿日期:2011-10-20 出版日期:2012-09-20 发布日期:2012-09-20

Age and Tectonic Setting of the Aoyougou-Erzhihaladaban Ophiolite in the Western North Qilian Mountains, NW China

XIA Xiaohong¹, SUN Nan¹, SONG Shuguang¹, XIAO Xuchang²

1. The Key Laboratory of Orogenic Belts and Crustal Evolution MOE, School of Earth and Space Sciences, Peking University, Beijing 100871; 2. Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037;

Received:2011-10-20 Online:2012-09-20 Published:2012-09-20

摘要/Abstract

摘要： 熬油沟蛇绿岩是北祁连造山带西段最具代表性的蛇绿岩残片之一。运用SHRIMPⅡ锆石U-Pb法, 对北祁连造山带西段的熬油沟和二只哈拉达坂两地出露的细粒辉长岩和粒玄岩进行了精确同位素测年。采自熬油沟剖面的细粒辉长岩样品 ²⁰⁶Pb/²³⁸U年龄数据分布在一个很小的范围(490~508 Ma), 其加权平均年龄为501±4 Ma (MSWD=1.09); 采自二只哈拉剖面的粒玄岩样品年龄值稍小, ²⁰⁶Pb/²³⁸U加权平均年龄为495±4 Ma (MSWD=0.98)。结合详细的野外调查、矿物化学和地球化学研究, 认为熬油沟?二只哈拉达坂蛇绿岩构造破坏严重, 其中基性岩浆岩代表早?中寒武世的北祁连洋壳。与新元古界朱龙关群碳酸盐岩和砂泥岩整合产出的玄武岩不能作为蛇绿岩的喷出岩系列, 而有可能是震旦纪的大陆溢流玄武岩, 代表新元古代全球Rodinia大陆裂解的岩浆产物。

关键词: 北祁连西段, 熬油沟蛇绿岩, 大陆溢流玄武岩, 形成时代

Abstract: The Aoyougou-Erzhihaladaban ophiolite is one of the representative ophiolite fragments in the west sector of the North Qilian orogenic belt. Using sensitive high resolution ion microprobe (SHRIMP), two samples from this area were dated. A fine-grained gabbro sample from the Aoyougou section has consistent apparent ²⁰⁶Pb/²³⁸U ages in the range of 490 to 508 Ma with a weighted mean age of 501 ± 4 Ma (MSWD=1.09), whereas a dolerite sample from the Erzhihaladaban section has a relatively younger ²⁰⁶Pb/²³⁸U age of 495±4 Ma (MSWD=0.98). Combined with detailed field examination, mineral and whole-rock chemical study, we conclude that the exposed Aoyougou-Erzhihaladaban ophiolite represents a part of the dismembered North Qianlian oceanic crust of the era. In addition, the authors propose that the voluminous basalts interstratified with carbonates and mudstones of the Neo-Proterozoic Zhulongguan group do not belong to the Aoyougou-Erzhihaladaban ophiolite. Instead, they may be continental flood basalts formed as a result of break-up of the Rodinia supercontinent.

Key words: Western North Qilian orogenic belt, Aoyougou ophiolite, continental flood basalts, formation age

中图分类号:

P581

夏小洪,孙楠,宋述光,肖序常. 北祁连西段熬油沟---二只哈拉达坂蛇绿岩的形成环境和时代[J]. 北京大学学报（自然科学版）.

XIA Xiaohong,SUN Nan,SONG Shuguang,XIAO Xuchang. Age and Tectonic Setting of the Aoyougou-Erzhihaladaban Ophiolite in the Western North Qilian Mountains, NW China[J]. Acta Scientiarum Naturalium Universitatis Pekinensis.

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链接本文: https://xbna.pku.edu.cn/CN/

https://xbna.pku.edu.cn/CN/Y2012/V48/I5/757

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北祁连西段熬油沟---二只哈拉达坂蛇绿岩的形成环境和时代

Age and Tectonic Setting of the Aoyougou-Erzhihaladaban Ophiolite in the Western North Qilian Mountains, NW China

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