Fission Track Ages as Evidence for the Thermal History of Jiala Fault (Eastern Tibet) and its Tectonic Implications
Date Issued
2006
Date
2006
Author(s)
Chung, Ling
DOI
zh-TW
Abstract
Jiali Fault in eastern Tibet bounds the Karakorum-Jiali Fault Zone (KJFZ) in the east and cuts the Namche Barwa Syntaxis northerly. Its movement is not only closely related to the clockwise rotation and extruded body of eastern Tibet, but also strongly correlated to the northeastward indentation of India plate. Representative samples have been collected for fission-track (FT) dating from Jiali fault zone (Tungmai, north of Namche Barwa Syntaxis) and its two easternmost branches, the Parlung and Puqu Faults (near Chayu).
FT ages are analyzed using external detector method. In Chayu region, zircon and apatite FT ages from undeformed granites in Parlung Fault are ca. 23-19 Ma; in the southern branch, Puqu Fault, zircon and apatite FT ages (from both deformed and undeformed rocks) are 10-9 Ma and ca. 6 Ma respectively. In Tungmai area, FT results yield younger ranges than Chayu area (both zircon and apatite ages < 3 Ma from deformed samples).
Based on the FT dates in this study, we can conclude that the stress/strain of Jiali Shearing Zone may have shifted from northern branch to southern branch since its initial movement. During 23-19 Ma, the northern branch, Parlung Fault, had undergone an uplifting event which is considered to be related to the shearing of the fault. Consequently, the shearing stress may transfer to the southern branch and had lasted until ~11 Ma. The different ages younger than ~10 Ma obtained from Chayu and Tungmai suggest that the 10-6 Ma uplifting was a large scale event that occurred in Himalayas region and eastern Tibet. However, the uplifting after 3 Ma is believed to be a regional event that resulted from the indentation of India into Eurasia Plate and focusing erosion in Eastern Himalaya Syntaxis. Moreover, the diachronous uplifting in eastern Tibet might provide possible time series constraint for the river capture hypothesis of the unusual drainage system in eastern Tibet.
Subjects
西藏
嘉黎斷裂帶
核飛跡定年
Tibet
Jiali Fault
Fission track dating
Type
thesis
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