Late Oligocene-early Miocene transformation of postcollisional magmatism in Tibet
Late Oligocene-early Miocene transformation of postcollisional magmatism in Tibet
复制标题
西藏晚渐新世-早中新世碰撞后岩浆作用的转变
DOI：
10.1130/g46147.1
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发表时间：
2019-08-01
期刊：
影响因子：
5.8
通讯作者：
Wilson, Marjorie
中科院分区：
文献类型：
--
作者：
Guo, Zhengfu;Wilson, Marjorie
青藏高原的隆升被认为是新生代最重要的造山运动和气候强迫事件之一，与印度-亚洲碰撞和随后的大陆岩石圈俯冲有关的地球动力学变化有关。然而，俯冲大陆岩石圈部分的命运和规模仍然存在很大争议。利用对西藏各地碰撞后岩浆岩时空分布的全面汇编，加上新的地球化学和Sr-Nd-Pb同位素数据和建模模拟，我们提出了一个整体的两阶段演化模型来解释岩浆成因与大陆俯冲之间的联系。 25 Ma之前的岩浆活动是由特提斯台地碳酸盐沉积物覆盖的印度洋和大陆岩石圈向北俯冲引起的富含碳酸盐的上地幔柱的持续上涌引起的，而25 Ma之后的岩浆活动则与大陆向北和向南相反的俯冲有关。我们的模型表明西藏岩浆活动的分布和性质在大约25 Ma，反映了早中新世喜马拉雅-青藏造山带及相关地幔动力学过程的显着变化。了解这种转变可能会对喜马拉雅-西藏体系作为古代造山带的现代模拟的实用性产生重要影响。
Uplift of the Tibetan Plateau is thought to be one of the most important orogenic and climate forcing events of the Cenozoic Era, associated with geodynamic changes related to India-Asia collision and subsequent continental lithosphere subduction. However, the fate and scale of the subducted continental lithosphere segments remain highly controversial. Using a comprehensive compilation of the spatiotemporal distribution of postcollisional magmatic rocks across Tibet, together with new geochemical and Sr-Nd-Pb isotopic data and modeling simulations, we propose a holistic, two-stage evolutionary model to explain the link between genesis of the magmas and continental subduction. The magmatism prior to 25 Ma resulted from continuous upwelling of a carbonate-rich upper-mantle plume induced by northward underthrusting of Indian oceanic and continental lithosphere with its cover of Tethyan platform carbonate sediments, whereas magmatism after 25 Ma was related to opposing north-directed and south-directed continental subduction. Our model indicates a transformation in the distribution and nature of the magmatism in Tibet at ca. 25 Ma, which reflects a significant change in the Himalayan-Tibetan orogen and associated mantle dynamic processes in the early Miocene. Understanding this transformation could have important implications for the utility of the Himalayan-Tibetan system as a modern analogue for ancient orogens.