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首页> 外文期刊>Geological Society of America Bulletin >Oceanic plateau subduction during closure of the Bangong-Nujiang Tethyan Ocean: Insights from central Tibetan volcanic rocks
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Oceanic plateau subduction during closure of the Bangong-Nujiang Tethyan Ocean: Insights from central Tibetan volcanic rocks

机译：孟敬 - 努江蒂斯山海洋关闭期间的海洋高原俯冲：中部藏族火山岩中央洞察力

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摘要

Identification of arc magmatic rock associations in a subduction zone has important implications for specifically revealing the geodynamic evolution of the subduction system. The closure time of the Bangong-Nujiang Tethyan Ocean and the detailed subduction processes have been hotly debated, hindering our understanding of the tectonic evolution of central Tibet. Here, we investigated the ca. 110-104 Ma Gerze lavas (basalts, basaltic andesites, andesites, dacites, and rhyolites) in southern Qiangtang. Fusion of slab fluid-metasomatized mantle wedge could yield the basalts, and such basaltic magmas, if contaminated with ancient basement orthogneisses, could have formed the andesites. The basaltic andesites with high Nb and Nb/La are similar to the Nb-enriched arc basalts and probably originated from slab melt-metasomatized mantle. The dacites were generated by fractional crystallization of the subducted melange-derived intermediate magmas. The rhyolites have geochemical characteristics (high SiO2 and La/Yb; low MgO and Sr/Y) similar to those of Jamaican-type adakites and were possibly sourced from the subducted oceanic plateau at low pressures. The Gerze Jamaican-type adakites and Nb-enriched basalt association could imply intense slab-mantle interactions. The Gerze lava suites show clear arc affinities, indicating that oceanic subduction may have lasted until 100 Ma. Based on previous studies and a noticeable ca. 145-125 Ma magmatic lull in southern Qiangtang, we suggest that the Bangong-Nujiang oceanic subduction geodynamics involved normal subduction (170-145 Ma), flat subduction (145-125 Ma), and slab roll-back (125-101 Ma). Moreover, the flat subduction was most likely caused by subduction of the oceanic plateau. Therefore, we propose, for the first time, that Tethyan oceanic plateau subduction during the Early Cretaceous could explain the tectonic evolution of the Bangong-Nujiang Ocean and distinctive magmatism in southern Qiangtang, central Tibet.
机译：俯冲区域中的弧形岩石岩的识别具有重要意义，专门揭示俯冲系统的地磁演变。邦贡 - 怒江Tethyan海洋的关闭时间和详细的俯冲流程已经热烈辩论，阻碍了我们对西藏中部构造演变的理解。在这里，我们调查了CA. 110-104南羌塘南部沼泽熔岩（玄武岩，玄武岩，玄武岩，脂肪酸和流变脉）。板坯流体偏析的地幔楔形融合可以产生玄武岩，而这种玄武岩岩浆，如果遭受古代地下室的突出症，可以形成茜素。具有高Nb和Nb / La的玄武岩和叶茎类似于Nb富含Nb的弧形沼气，并且可能源自板坯熔融弥物的搭腔。达科酸盐通过底电解的混合物衍生的中间岩浆的分数结晶产生。流螺栓具有类似于牙买加型Adakites的地球化学特性（高SiO2和La / Yb;低MgO和Sr / Y），并且可能在低压下从底层海洋高原中源。 Gerze Jamaican型Adakites和NB富含玄武岩协会可能意味着强烈的平板式互动。 Gerze Lava Suites显示出清晰的电弧亲和力，表明海洋俯冲可能持续到100 mA。基于以前的研究和一个明显的CA. 145-125 Ma Magmatic Bull在南羌塘南部，邦贡 - 怒江海洋俯冲地球动力学涉及正常俯冲（170-145 mA），平板（145-125 mA），平板回来（125-101 ma） 。此外，平面俯冲最有可能由海洋高原俯冲引起的。因此，我们首次提出Thetyan海洋高原郊区在早期的白垩纪中可以解释邦格 - 南羌塘中部南部的邦戈 - 怒江海洋和独特的岩浆的构造演变。

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    Hao Lu-Lu; Wang Qiang; Zhang Chunfu; Ou Quan; Yang Jin-Hui; Dan Wei; Jiang Zi-Qi;

  • 作者单位

    Chinese Acad Sci Guangzhou Inst Geochem State Key Lab Isotope Geochem Guangzhou 510640 Guangdong Peoples R China;

    Chinese Acad Sci Guangzhou Inst Geochem State Key Lab Isotope Geochem Guangzhou 510640 Guangdong Peoples R China;

    Ft Hays State Univ Dept Geosci Hays KS 67601 USA;

    Chinese Acad Sci Guangzhou Inst Geochem State Key Lab Isotope Geochem Guangzhou 510640 Guangdong Peoples R China;

    Chinese Acad Sci Inst Geol &

    Geophys Beijing 100029 Peoples R China;

    Chinese Acad Sci Guangzhou Inst Geochem State Key Lab Isotope Geochem Guangzhou 510640 Guangdong Peoples R China;

    Guilin Univ Technol Sch Earth Sci Guilin 541004 Peoples R China;

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  • 正文语种 eng
  • 中图分类 地质学;
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