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<p>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&#xa0;~&#xa0;1075&#xa0;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&#xa0;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&#xa0;Ma) magmatism. Evidence of Late Eocene (35.3&#xa0;±&#xa0;1.8&#xa0;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&#xa0;Ma), followed by extension-induced exhumation. Leucogranite emplacement ceased along the South Tibetan Detachment System during the Middle Miocene (17.77&#xa0;±&#xa0;0.61&#xa0;Ma) and tectonic activity subsequently migrated southwards.</p>

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

  • 期刊论文

  • 发表日期：

    2025年7月1日

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

摘要

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.