印度洛克理工学院G. Deshmukh团队研究了藏南拆离体系（STDS）收缩和伸展构造的U-Pb锆石年代学约束。2025年7月1日出版的《地球化学学报》杂志发表了这一最新研究成果。

南藏拆离体系（STDS）是喜马拉雅造山带的一个主要伸展断裂体系，它将大喜马拉雅层序与北部上覆的特提斯喜马拉雅层序分隔开来。在西北喜马拉雅的Dhauliganga山谷，在STDS的下盘，褶皱的沙质片麻岩产生了新元古代~ 1075 Ma的U-Pb碎屑锆石群，并被寒武-奥陶系花岗岩类侵入。随后是晚始新世-中新世中期的岩浆活动。

除了构造分析和变形组构研究外，青藏高原南缘滑脱系活动的时间可以通过构造前、构造同期和构造后变形和未变形浅花岗岩体的U-Pb锆石年代学年龄来确定。和谐白花岗岩体在部分熔融过程中继承了下盘高品位片麻岩的新元古代锆石。晚始新世岩浆岩作用和熔融岩浆岩作用（~38 ~ 34 Ma）与巴罗纪变质作用同时发生，随后是晚渐新世伸展引起的掘出。

大喜马拉雅层序最上层亮花岗岩的U-Pb锆石年代学表现为晚始新世—早渐新世（35 ~ 23 Ma）岩浆活动。在片麻岩中观察到晚始新世（35.3±1.8 Ma）西向收缩、结晶增厚和相关变质作用的证据，这些片麻岩表现出紧密的等斜褶皱，轴向北倾。晚渐新世-早中新世（24-21 Ma）可能发生了由收缩构造向伸展构造的转变，随后是伸展构造的掘出。中中新世（17.77±0.61 Ma），沿藏南拆离体系的浅花岗岩侵位停止，构造活动随后向南迁移。

附：英文原文

Title: U–Pb zircon geochronology constraints on the contractional and extensional tectonics along the South Tibetan detachment system (STDS), Dhauliganga Valley, NW Himalaya

Author: Deshmukh, G., Jain, A. K., Mukherjee, P. K., Singh, A. K., Dixit, R., Kumar, Pankaj

Issue&Volume: 2025-07-01

Abstract: The South Tibetan detachment system (STDS), a dominant extensional fault system in the Himalayan orogen, separates the Greater Himalayan Sequence from the overlying Tethyan Himalayan Sequence in the north. Along the Dhauliganga Valley, NW Himalaya, folded psammitic gneisses in the immediate footwall of the STDS yield a Neoproterozoic ~ 1075 Ma U–Pb detrital zircon population and are intruded by Cambro-Ordovician granitoids. This is followed by protracted magmatism during the Late Eocene–Middle Miocene. In addition to structural analysis and deformation fabric studies, the timing of activity along the South Tibetan Detachment System can be constrained by U–Pb zircon geochronology ages of pre-, syn- and post-tectonically deformed and undeformed leucogranite bodies. The concordant leucogranites inherit the Neoproterozoic zircons from the footwall high-grade gneisses during their partial melting. Late Eocene migmatization and melt intrusion (~38–34 Ma) were coeval with Barrovian metamorphic, followed by Late Oligocene extension-induced exhumation. The U–Pb zircon geochronology of leucogranites within the uppermost Greater Himalayan Sequence show Late Eocene–Early Oligocene (35–23 Ma) magmatism. Evidence of Late Eocene (35.3 ± 1.8 Ma) SW-directed contraction, crustal thickening and associated metamorphism is observed in gneisses exhibiting tight isoclinal folds with NE-dipping axial surfaces. The transition from contractional to extensional tectonics might have likely occurred in the Late Oligocene–Early Miocene (24–21 Ma), followed by extension-induced exhumation. Leucogranite emplacement ceased along the South Tibetan Detachment System during the Middle Miocene (17.77 ± 0.61 Ma) and tectonic activity subsequently migrated southwards.

DOI: 10.1007/s11631-025-00798-3

Source: https://link.springer.com/article/10.1007/s11631-025-00798-3