Early Miocene rapid exhumation in southern Tibet: Insights from P-T-t-D-magmatism path of Yardoi dome
Early Miocene rapid exhumation in southern Tibet: Insights from P-T-t-D-magmatism path of Yardoi dome
复制标题
藏南早中新世快速剥露：雅多伊圆顶P-T-t-D-岩浆作用路径的见解
DOI：
10.1016/j.lithos.2018.02.003
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发表时间：
2018
期刊：
影响因子：
3.5
通讯作者：
Liu Xiao-Chi
中科院分区：
文献类型：
--
作者：
Wang Jia-Min;Wu Fu-Yuan;Rubatto Daniela;Liu Kai;Zhang Jin-Jiang;Liu Xiao-Chi
重建造山带内片麻岩穹丘的演化面临着挑战，因为穹丘可以在各种地球动力学环境中并通过多种穹顶机制形成。对于北喜马拉雅片麻岩穹丘（NHGD），其是否在高原缩短、伸展或塌陷过程中形成，以及岩浆作用、变质作用和变形的时空关系如何，存在争议。本研究利用野外测绘、岩相学、相平衡模型和新的独居石年龄对西藏南部的雅多伊穹顶进行了调查。由此产生的P-T-时间-变形-岩浆作用路径首次揭示了Yardoi穹顶中变质作用、变形和岩浆作用的时空关系：a）穹顶地幔记录了早中新世（18-17Ma）蓝晶石级巴罗夫变质条件650±30°C和9±1kbar（M2）的顺向加载； b) 主要的自顶向北变形组构(D2)形成同峰后变质作用; c) 与隆起相关的白色花岗岩的侵位是19-17Ma的同变质作用。雅多伊圆顶的滑脱剪切带与藏南滑脱系统（STDS）之间的联系得到了证实。通过与喜马拉雅山的造山带规模的构造过程进行比较，我们认为早中新世期间汇聚的地球动力学背景下的南北延伸是雅多伊穹顶的形成的原因。在更广泛的构造背景下，早中新世深层地壳岩石的快速折返与西藏南部和喜马拉雅造山带的快速隆起同时发生。
Reconstructing the evolution of Gneiss domes within orogenic belts poses challenges because domes can form in a variety of geodynamic settings and by multiple doming mechanisms. For the North Himalayan gneiss domes (NHGD), it is debated whether they formed during shortening, extension or collapse of the plateau, and what is the spatial and temporal relationship of magmatism, metamorphism and deformation. This study investigates the Yardoi dome in southern Tibet using field mapping, petrography, phase equilibria modelling and new monazite ages. The resulting P–T–time–deformation–magmatism path for the first time reveals the spatial and temporal relationship of metamorphism, deformation and magmatism in the Yardoi dome: a) the dome mantle recorded prograde loading to kyanite-grade Barrovian metamorphic conditions of 650 ± 30 °C and 9 ± 1 kbar (M2) in the Early Miocene (18–17 Ma); b) the main top-to-the-north deformation fabric (D2) formed syn- to post-peak-metamorphism; c) the emplacement of leucorgranites related to doming is syn-metamorphism at 19–17 Ma. The link between the detachment shear zone in the Yardoi dome and the South Tibetan detachment system (STDS) is confirmed. By comparing with orogen-scale tectonic processes in the Himalaya, we suggest that north-south extension in a convergent geodynamic setting during Early Miocene accounts for formation of the Yardoi dome. In a wider tectonic context, the Early Miocene rapid exhumation of deep crustal rocks was contemporaneous with the rapid uplift of southern Tibet and the Himalayan orogen.