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.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
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。
