Origin of the Xigaze ophiolite, Yarlung Zangbo suture zone, southern Tibet
Origin of the Xigaze ophiolite, Yarlung Zangbo suture zone, southern Tibet
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DOI：
10.1016/0040-1951(85)90048-4
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发表时间：
1985-10
期刊：
影响因子：
2.9
通讯作者：
J. Girardeau;J. Mercier;Z. Yougong
中科院分区：
文献类型：
--
作者：
J. Girardeau;J. Mercier;Z. Yougong
西藏日喀则蛇绿岩具有独特的岩性、岩石学、结构和构造特征。在整个蛇绿岩序列中没有大量的堆晶辉长岩，但有粗玄岩侵入体，其中一些侵入到已经蛇纹化的橄榄岩中，只有少量残余方辉橄榄岩和纯橄榄岩在低温和低压下平衡，最上部的橄榄岩中有相对低温的变形结构。这些特征表明，日喀则蛇绿岩形成的扩张中心热流值很低，与扩张中心的不连续和缓慢增生的成因相一致。然而，这条蛇绿岩并不代表典型的洋中脊蛇绿岩;相反，它形成于欧亚大陆南缘的一个小盆地，因此在一个预先存在的海洋岩石圈内。近南北向日喀则古脊的开启是180 ~ 110 Ma期间非洲相对于欧亚大陆的东西向漂移的结果。日喀则蛇绿岩形成于120 ~ 110 Ma前，向南北方向侵位到大陆上，与非洲和印度板块运动方向的变化相关：第一次洋内逆冲事件可能发生在110 ~ 85 Ma，最后一次逆冲事件可能发生在50 Ma左右。印度-欧亚大陆碰撞期间。
The Xigaze ophiolite, (Tibet) displays unusual lithological, petrological, textural, and structural characteristics. There are no large masses of cumulate gabbros, but dolerite intrusives throughout the whole ophiolite sequence, some of which were intruded into already serpentinized peridotites, only minor residual harzburgites and dunites in dominantly Iherzolitic peridotites equilibrated at low temperatures and pressures, and relatively low-temperature deformation structures in the uppermost peridotites. These features suggest a very low heat flow at the spreading center where the Xigaze ophiolite was formed, in good agreement with a discontinuous and slowly-accreting spreading center origin. However, this ophiolite does not represent a typical mid-oceanic ridge ophiolite; rather it was formed in a small basin located at the southern margin of Eurasia, hence within a preexisting oceanic lithosphere. The opening of the nearly N-S Xigaze paleo-ridge resulted from the W-E drift of Africa relative to Eurasia from 180 to 110 Ma. The N-S emplacement onto the continent of the Xigaze ophiolite, formed 120 to 110 Ma ago, can be correlated to changes in direction of motion of the African and Indian plates: a primary intra-oceanic thrusting event probably occurring at 110 or 85 Ma and the final obduction near 50 Ma during the India-Eurasia collision.