Timing of Displacement along the Yardoi Detachment Fault, Southern Tibet: Insights from Zircon U-Pb and Mica 40Ar−39Ar Geochronology
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-ICP-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 °C Ar closure temperature in muscovite at ≈14 Ma to the 335 °C 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-crustal 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.
Keywordsleucogranite geochronology Yardoi dome southern Tibet Himalayan Orogen
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This research was 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), the State Scholarship Fund (No. 201809110029), and the China Geological Survey (No. DD20160022). It’s an honor to be invited by Prof. Jingsui Yang to contribute our research into this special issue. Comments on an earlier version of this study from Dr. Kyle Larson improved the clarity of the manuscript. Constructive reviews by two anonymous reviewers and the editors are appreciated. The final publication is available at Springer via https://doi.org/10.1007/s12583-019-1223-z.
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