Structural evolution of the Yushu-Nangqian region and its relationship to syncollisional igneous activity, east-central Tibet
Structural evolution of the Yushu-Nangqian region and its relationship to syncollisional igneous activity, east-central Tibet
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DOI：
10.1130/b25572.1
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发表时间：
2005-09
影响因子：
4.9
通讯作者：
M. Spurlin;A. Yin;B. Horton;Jiangyu Zhou;Jianghai Wang
中科院分区：
文献类型：
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作者：
M. Spurlin;A. Yin;B. Horton;Jiangyu Zhou;Jianghai Wang
野外测绘、年代学分析和剖面构造揭示了西藏北部玉树-囊谦冲断带的长期变形历史和新生代NE-SW缩短（在当前坐标）至少61公里。新生代收缩开始于51Ma之前，随后首先发生西北走向的右滑断层，随后发生西北走向的左滑断层。新近纪地层的褶皱和逆冲作用表现出新的东北-西南收缩，随后又出现了西北走向的左滑断层。新近纪晚期变形表现为局部北伸正断层。玉树-囊谦带的缩短似乎是通过薄皮逆冲来调节的，这就提出了下地壳层如何调节变形的问题。为了解决这个问题，我们对 51-49 Ma 和 38-37 Ma 的火成岩进行了地球化学分析。这些岩石表现出俯冲特征的地球化学特征，这意味着西藏东北部同时代的地壳增厚很可能是由大陆俯冲引起的。
Field mapping, geochronological analyses, and cross section construction reveal a protracted deformation history and a minimum of 61 km of Cenozoic NE-SW shortening (in present coordinates) across the Yushu-Nangqian thrust belt in northern Tibet. Cenozoic contraction started prior to 51 Ma and was followed first by northwest-striking right-slip faulting and later by northwest-striking left-slip faulting. Renewed NE-SW contraction is expressed by folding of Neogene strata and thrusting, which again was followed by northwest-striking left-slip faults. Late Neogene deformation is expressed by local north-striking normal faults. Shortening across the Yushu-Nangqian belt appears to be accommodated by thin-skinned thrusting, which raises the question of how the deformation was accommodated in the lower crustal levels. To resolve this problem, we perform geochemical analysis of igneous rocks dated as 51–49 and 38–37 Ma. The rocks exhibit geochemical signatures characteristic of subduction, which implies that coeval crustal thickening in northeastern Tibet was most likely induced by continental subduction.