新疆达拉布特蛇绿岩带玄武岩地球化学特征：古亚洲洋与特提斯洋的对比  

Geochemical and Sr-Nd-Pb isotopic characteristics of the Dalabute ophiolite,Xinjiang:Comparison between the Paleo-Asian ocean and the Tethyan mantle domains.

作　　者：雷敏[1,2] 赵志丹[1] 侯青叶[1] 张宏飞[3] 许继峰[4] 陈岳龙[1] 张本仁[3] 刘希军[4] 

机构地区：[1]中国地质大学地质过程与矿产资源国家重点实验室,中国地质大学地球科学与资源学院,北京100083 [2]中国地质科学院地质研究所,北京100037 [3]中国地质大学地质过程与矿产资源国家重点实验室,中国地质大学地球化学系,武汉430074 [4]中国科学院广州地球化学研究所同位素年代学和地球化学重点实验室,广州510640

出　　处：《岩石学报》2008年第4期661-672,共12页Acta Petrologica Sinica

基　　金：国家重点基础研究发展规划项目(2002CB412603);国家自然科学基金(40473020,40234052);国家杰出青年基金(40425003);中国地调局综合研究项目;中科院广州地化所同位素开放实验室基金;高等学校学科创新引智计划(B07011)资助。

摘　　要：发育在我国北部的古亚洲洋构造域和西南部的特提斯构造域是中国境内最重要的两个构造体系,有关这两个构造域的地幔地球化学特征是揭示它们的演化与交接关系的重要课题之一。本文选择发育在新疆西准噶尔地区达拉布特蛇绿岩带中阿克巴斯套和大棍的枕状玄武岩进行了系统的岩石学和地球化学与Sr-Nd-Pb同位素地球化学研究,结果表明,达拉布特蛇绿岩带中枕状玄武岩具有N-MORB和E-MORB特征,可能形成于大洋中脊环境。岩石的^(87)Sr/^(86)Sr为0.682112～0.706040之间;^(143)Nd/^(144)Nd为0.512713～0.512879,ε_(Nd)(t)=+2.8～+5.1,^(206)Pb/^(204)Pb、^(207)Pb/^(204)Pb和^(208)Pb/^(204)Pb的变化范围分别是18.341～20.085、15.541～15.651和38.292～40.534。将达拉布特玄武岩的微量元素特征比值、Nd-Pb同位素等与印度洋MORB和太平洋与北大西洋MORB,以及已知的特提斯和古亚洲洋地幔域进行对比表明,达拉布特蛇绿岩单元内MORB型玄武岩与特提斯构造域特蛇绿岩单元内MORB型玄武岩同位素特征一致,都显示了印度洋型的MORB特征。这意味着位于现今新疆西准噶尔地区的古亚洲洋地幔域没有显示出与特提斯不同的典型的太平洋和北大西洋的地球化学特征。The Paleo-Asian Ocean in northern China and the Tethys in southwestern China are the two major tectonic domains in China. Geochemical study is one of the most important issues in revealing the nature of the upper mantle and their relationship between the above two mantle domains. This paper present a systemetic study of petrology, geochemical and Sr-Nd-Pb isotopic gechemistry of the basaltic rocks collected from Akebasitao and Dagun regions of Dalabute ophiolite in Western Junggar of Xinjiang. The rock show typical N-MORB and E-MORB type geochemical features, indicating that they have mid-ocean ridge environmental affinity. Their Sr-Nd-Pb isotopic compositions （ ^87 Sr/^86 Sr = 0. 682112 - 0. 706040, ^143 Nd/^144 Nd = 0. 512713 - 0. 512879, εNd （ t ） = ＋ 2. 8 - ＋ 5.1 , ^206Pb/^204Pb = 18. 341 - 20. 085, ^207Pb/^204 Pb = 15. 541 - 15. 651 , and ^208Pb/^204 Pb = 38. 292 - 40. 534） and representative element ratios show that they have similar compositions to that of the Tethyan mantle domain. They all have typical Indian MORB-type geochemical features, and distinct to the known Paleo-Asian Ocean mantle domain. This suggests that the Dalabute ophiolite in Xinjiang now located in the Paleo-Asian tectonic settings, show Tethyan （Indian MORB） mantle domain feature, instead of the Pacific and north Atlantic oceanic mantle domains.

关 键 词：古亚洲洋 特提斯洋 蛇绿岩 玄武岩 同位素地球化学 新疆西准噶尔 

分 类 号：P588.145[天文地球—岩石学]