The Yardoi dome is located in the eastern end of the northwest-southeast extending North Himalayan domes (NHD). The dome exposes a granite pluton in the core and three lithologictectonic units separated by the upper d...The Yardoi dome is located in the eastern end of the northwest-southeast extending North Himalayan domes (NHD). The dome exposes a granite pluton in the core and three lithologictectonic units separated by the upper detachment fault and the lower detachment fault. The Yardoi detachment fault (YDF), corresponding to the lower detachment fault, is a 800 m strongly deformed top-NW shear zone. LA-1CP-MS zircon U-Pb dating yielded a crystallization ages of 19.57±0.23 to 15.5±0.11 Ma for the leucogranite dyke swarm, which indicates that the ductile motion along the YDF began at ca. 20 Ma. The 40Ar/39Ar muscovite ages of 14.05±0.2 to 13.2±0.2 Ma and the 40Ar/39Ar biotite age of 13.15±0.2 Ma, suggest that the exhumation led to cooling through the 370℃ Ar closure temperature in muscovite at ~14 Ma to the 335℃ Ar closure temperature in biotite at ~13 Ma. Our new geochronological data from the Yardoi dome and other domes in the Tethyan Himalayan Sequences suggest that the ductile deformation in the region began at or before^36 Ma in a deep tectonic level, resulting in southward ductile flow at the mid-crustai tectonic level that continued from 20 to 13 Ma. Comparing the Yardoi dome to other domes in the NHD, the cooling ages show a clear diachronism and they are progressively younger from the West Himalayan to the East Himalayan.展开更多
基金supported by the Chinese Academy of Geological Sciences (CAGS) Research Fund (Nos. J1623, YYWF201708)the National Natural Science Foundation of China (Nos. 41502196, 41472198, 41872224, 41430212)+1 种基金the State Scholarship Fund (No. 201809110029)the China Geological Survey (No. DD20160022)
文摘The Yardoi dome is located in the eastern end of the northwest-southeast extending North Himalayan domes (NHD). The dome exposes a granite pluton in the core and three lithologictectonic units separated by the upper detachment fault and the lower detachment fault. The Yardoi detachment fault (YDF), corresponding to the lower detachment fault, is a 800 m strongly deformed top-NW shear zone. LA-1CP-MS zircon U-Pb dating yielded a crystallization ages of 19.57±0.23 to 15.5±0.11 Ma for the leucogranite dyke swarm, which indicates that the ductile motion along the YDF began at ca. 20 Ma. The 40Ar/39Ar muscovite ages of 14.05±0.2 to 13.2±0.2 Ma and the 40Ar/39Ar biotite age of 13.15±0.2 Ma, suggest that the exhumation led to cooling through the 370℃ Ar closure temperature in muscovite at ~14 Ma to the 335℃ Ar closure temperature in biotite at ~13 Ma. Our new geochronological data from the Yardoi dome and other domes in the Tethyan Himalayan Sequences suggest that the ductile deformation in the region began at or before^36 Ma in a deep tectonic level, resulting in southward ductile flow at the mid-crustai tectonic level that continued from 20 to 13 Ma. Comparing the Yardoi dome to other domes in the NHD, the cooling ages show a clear diachronism and they are progressively younger from the West Himalayan to the East Himalayan.
