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首页> 外文期刊>Journal of Asian earth sciences >Geochronology and geochemistry of the Eastern Erenhot ophiolitic complex: Implications for the tectonic evolution of the Inner Mongolia-Daxinganling Orogenic Belt
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Geochronology and geochemistry of the Eastern Erenhot ophiolitic complex: Implications for the tectonic evolution of the Inner Mongolia-Daxinganling Orogenic Belt

机译：二连浩特东部蛇绿岩复合体的年代学和地球化学：对内蒙古-大兴安岭造山带构造演化的启示

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摘要

The Eastern Erenhot ophiolitic complex (EOC) is one of the numerous fragments of oceanic lithosphere in southeastern Central Asian Orogenic Belt. It is composed dominantly of serpentinized ultramafic rocks with subordinate gabbros, mafic lavas and minor plagiogranite dikes. Zircons from two gabbros and one plagiogranite yielded weighted mean ~(206)Pb/~(238)U ages of 354.2 ± 4.5 Ma, 353.3 ± 3.7 Ma and 344.8 ± 5.5 Ma. These ages suggest that the oceanic crust of the EOC formed in a maximum time period of 10 Ma, and that the plagiogranite may have formed later than the gabbroic section. An undeformed and unmetamorphosed dioritic porphyry dike intruded in the Carboniferous strata near the EOC has an intrusive age of 313.6 + 2.9 Ma and provides a possible younger minimum time limit for the formation of the early Carboniferous ophiolitic complex. All the mafic rocks have similar chondrite normalized REE patterns characterized by moderate depletion in LREE with (La/Yb)_N (0.20-0.75) similar to normal middle oceanic ridge basalt (N-MORB). The PM-normalized trace element patterns of the gabbros and massive basalts are also reasonably consistent, essentially similar to those of N-MORB except for some enrichment in LILE (e.g. Rb, Ba) and slightly negative Ti anomalies. The plagiogranite samples are characterized by lower K_2O (0.45-0.73 wt%) comparable with oceanic plagiogranite. They have LREE-enriched, chon-drite-normalized REE patterns with varying Eu anomalies and the trace elements (e.g. Rb, Y, Nb) show similarity to volcanic arc granite. These geochemical features of the EOC show a similar volcanic arc affinity, suggesting that they form in a back-arc-type environment. Their origin is attributed to asthenospheric upwelling and further lithospheric extension during early Carboniferous, formed as a consequence of slab breakoff on collision of the northern early to mid-Paleozoic orogenic terrane and the Hunshandake Block.
机译：二连浩特东部蛇绿岩复合体（EOC）是中亚造山带东南部海洋岩石圈众多碎片之一。它主要由蛇纹化的超镁铁质岩石组成，具有次级辉长岩，镁铁质熔岩和次要斜长花岗岩岩脉。来自两个辉长岩和一个斜长花岗岩的锆石的加权平均〜（206）Pb /〜（238）U年龄为354.2±4.5 Ma，353.3±3.7 Ma和344.8±5.5 Ma。这些年龄表明，EOC的洋壳形成的最大时间为10 Ma，斜长花岗岩的形成可能晚于辉长岩剖面。侵入到EOC附近石炭纪地层的未变形和未变质的闪长斑岩斑岩的侵入年龄为313.6 + 2.9 Ma，并且为早期石炭纪蛇纹石复合体的形成提供了更年轻的最小时限。所有的镁铁质岩石都有类似的球粒陨石归一化REE模式，其特征在于LREE中的中等损耗（La / Yb）_N（0.20-0.75）与正常的中洋脊玄武岩（N-MORB）相似。长辉岩和块状玄武岩的PM归一化痕量元素模式也相当一致，基本与N-MORB相似，除了LILE中有一些富集（例如Rb，Ba）和Ti负异常。斜长花岗岩样品的特征在于与海洋斜长花岗岩相当的较低的K_2O（0.45-0.73 wt％）。它们具有丰富的LREE含量，按绒头状晶化归一化的REE模式，具有不同的Eu异常，并且痕量元素（例如Rb，Y，Nb）显示出与火山弧花岗岩的相似性。 EOC的这些地球化学特征显示出相似的火山弧亲和力，表明它们是在后弧型环境中形成的。它们的起源归因于石炭纪早期的软流圈上升和岩石圈的进一步扩展，这是由于北部早古生代造山地层和Hunshandake块体碰撞后平板破裂而形成的。

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  • 来源
    《Journal of Asian earth sciences》 |2015年第1期|279-293|共15页
  • 作者

    Zhicheng Zhang; Ke Li; Jianfeng Li; Wenhao Tang; Yan Chen; Zhiwen Luo;

  • 作者单位

    MOE Key Laboratory of Orogenic Belts and Crustal Evolution, Peking University, Beijing 100871, China,Department of Geology, School of Earth and Space Sciences, Room 3307, Yifu-2 Building, Peking University, No. 5 Yiheyuan Road, Haidian District, Beijing 100871, China;

    MOE Key Laboratory of Orogenic Belts and Crustal Evolution, Peking University, Beijing 100871, China School of Earth and Space Sciences, Peking University, Beijing 100871, China;

    MOE Key Laboratory of Orogenic Belts and Crustal Evolution, Peking University, Beijing 100871, China School of Earth and Space Sciences, Peking University, Beijing 100871, China;

    MOE Key Laboratory of Orogenic Belts and Crustal Evolution, Peking University, Beijing 100871, China School of Earth and Space Sciences, Peking University, Beijing 100871, China;

    MOE Key Laboratory of Orogenic Belts and Crustal Evolution, Peking University, Beijing 100871, China School of Earth and Space Sciences, Peking University, Beijing 100871, China;

    MOE Key Laboratory of Orogenic Belts and Crustal Evolution, Peking University, Beijing 100871, China School of Earth and Space Sciences, Peking University, Beijing 100871, China;

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  • 正文语种 eng
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  • 关键词

    Ophiolitic complex; Geochronology; Geochemistry; Carboniferous; Inner Mongolia-Daxinganling Orogenic Belt;

    机译：蛇纹石复合体;地球年代学;地球化学;石炭纪内蒙古大兴安岭造山带;

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