地学前缘 ›› 2018, Vol. 25 ›› Issue (6): 106-123.DOI: 10.13745/j.esf.sf.2018.11.15

• 岩石探针与全球构造 • 上一篇    下一篇

塔里木克拉通东北缘Columbia超大陆裂解事件：库鲁克塔格地区辉绿岩床的地球化学、锆石U-Pb年代学和Hf-O同位素证据

张健，李怀坤，张传林，田辉，钟焱，叶现韬   

  1. 1. 中国地质调查局 天津地质调查中心, 天津 300170 
    2. 河海大学 海洋学院, 江苏 南京 210098
  • 收稿日期:2018-07-22 修回日期:2018-10-30 出版日期:2018-11-30 发布日期:2018-11-30
  • 通讯作者: 李怀坤(1963—)，男，博士，研究员，主要从事前寒武纪年代学研究。E-mail:huaikunli@sina.com
  • 作者简介:张健(1982—)，男，硕士，高级工程师，主要从事同位素地球化学和年代学研究。E-mail：zhangjian91011@126.com
  • 基金资助:
    中国地质调查局地质调查项目(121201102000150009-06)

New evidence for the breakup of the Columbia supercontinent from the northeastern margin of Tarim Craton: rock geochemistry, zircon U-Pb geochronology and Hf-O isotopic compositions of the ca. 1.55 Ga diabase sills in the Kuruktag area.

ZHANG Jian,LI Huaikun,ZHANG Chuanlin,TIAN Hui,ZHONG Yan,YE Xiantao   

  1. 1. Tianjin Center of Geological Survey, China Geological Survey, Tianjin 300170, China 
    2. College of Oceanography, Hohai University, Nanjing 210093, China
  • Received:2018-07-22 Revised:2018-10-30 Online:2018-11-30 Published:2018-11-30
  • Supported by:
     

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摘要： 研究塔里木克拉通东北缘库鲁克塔格地区发育的中元古代早期基性岩浆活动，对深入了解Columbia超大陆裂解过程具有重要意义。本文报道了库鲁克塔格地区侵入于兴地塔格群的阿斯廷布拉克辉绿岩床SHRIMP锆石U-Pb年龄，结合岩石学、地球化学和Nd-Hf-O同位素资料，对该基性岩的形成时代、岩浆起源和源区类型以及岩浆作用的动力学背景进行讨论。研究表明：辉绿岩锆石具有高Th/U比值(>1)，CL图像带状分区，显示基性岩浆锆石特点，207Pb/206Pb 加权平均年龄(1 551±8) Ma代表辉绿岩的形成时代，锆石δ18O值为5.52‰~6.53‰(正态分布的峰值为5.8‰)，略高于地幔锆石的变化范围。辉绿岩高FeOT(11.4%~13.4%)，低MgO(5.46%~7.11%)和TiO2(1.51%~2.45%)，具有拉斑质属性，轻、重稀土元素分馏明显((La/Yb)N=4.6~5.4)，具弱的Eu正异常(δEu=1.05~1.27)，富集大离子亲石元素(LILE)，亏损Nb、Ta等高场强元素(HFSE)，微量元素组成与大陆溢流玄武岩(CFB)类似，全岩Nd(εNd(t)=-3.8~-1.8)和锆石Hf(εHf(t)=-3.7~1.9)同位素均显示岩浆来自富集地幔。阿斯廷布拉克辉绿岩是被交代的大陆岩石圈地幔部分熔融的产物，形成于板内的拉张环境，与该时期全球构造演化体制相吻合，属于中元古代早期Columbia超大陆裂解事件。

 

关键词: 塔里木克拉通, 库鲁克塔格, Columbia超大陆裂解, 中元古代, 辉绿岩

Abstract: The Mesoproterozoic diabase sills from Kuruktag along the northeastern margin of the Tarim Craton (TC) is of great significance for the understanding of the breakup of the Columbia supercontinent. In this contribution, we report new sensitive high-resolution ion microprobe (SHRIMP) zircon U-Pb ages and in-situ Hf-O isotopes, as well as whole-rock elemental and Sr-Nd isotopic data for the Astingbulake diabase sills. Zircons had high Th/U ratio and banded zoning in cathodoluminescence images, indicating their mafic magmatic origin, and yielded a weighted 207Pb/206Pb age of 1 551±8 Ma and elevated δ18O values of 5.52‰ to 6.53‰ (Gaussian distribution peak at 5.8‰) relative to mantle zircons. Geochemically, the diabase samples are characterized by high FeOT (11.4%13.4%), low TiO2 (1.51%2.45%) and MgO (5.46%7.11%) contents with Mg# ranging from 43 to 52. They contained relatively low REEs contents (90.1116)×10-6 with slightly positive Eu anomalies (δEu=1.051.27). Moreover, these samples are featured by enrichment in light rare earth elements (LREEs) and large ion lithophile elements (LILE) and depletion in heavy rare earth elements (HREEs) and Nb-Ta high field strength elements (HFSEs), consistent geochemical features with continental flood basalts (CFB). The coupled whole rock Nd and zircon Hf isotope compositions, with εNd(t) ranging from -3.8 to -1.8 and εHf(t) from -3.7 to 1.9, suggest that the Astingbulake diabase sills derived from enriched continental lithospheric mantle within intra-plate rifting or extensional setting, and the ca. 1.55 Ga diabase is closely related in time to the global early-Mesoproterozoic anorogenic magmatism associated with the breakup of Columbia supercontinent.

Key words: Tarim Craton, Kuruktag, Columbia supercontinent breakup, Mesoproterozoic, diabase

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