HR: 1340h
AN: T23C-1532    [Abstracts]
TI: Detrital zircon evidence from Burma for reorganization of the eastern Himalayan river system
AU: * Liang, Y
EM: d95224007@ntu.edu.tw
AF: National Taiwan University, Taipei P.O. Box 13-318, Taipei, 106, Taiwan
AU: Chung, S
AF: National Taiwan University, Taipei P.O. Box 13-318, Taipei, 106, Taiwan
AU: Liu, D
AF: Institute of Geology, Chinese Academy of Geological Sciences, No. 26, Baiwanzhuang Road, Beijing, 100037, China
AU: Xu, Y
AF: Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou P.O. Box 1131, Guangzhou, 510640, China
AU: Wu, F
AF: Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing P.O. Box 9825, Beijing, 100029, China
AU: Yang, J
AF: Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing P.O. Box 9825, Beijing, 100029, China
AU: Wang, Y
AF: Institute of Geology, Chinese Academy of Geological Sciences, No. 26, Baiwanzhuang Road, Beijing, 100037, China
AU: Mitchell, A
AF: Ivanhoe Myanmar Holdings, Ltd., 321-323, U Wisara Road, Sanchaung Township, Yangon, Myanmar
AU: Lo, C
AF: National Taiwan University, Taipei P.O. Box 13-318, Taipei, 106, Taiwan
AB: For studying the sedimentary source to sink relation and reorganizing of the mountain rivers around eastern Himalayas, we conducted a detrital zircon study from the Irrawaddy and Inner-Burma Basin by combined SHRIMP U-Pb dating and in-situ Hf isotope measurements. These results, together with U-Pb and Hf isotope data of igneous zircons from the eastern Transhimalayan batholith from southern Tibet to Burma, allow a more quantitative examination of the source provenance of sediments deposited in the drainage since Miocene time. For example, among 47 out of 62 dated zircons from Upper Miocene sandstone that show Cretaceous to Paleogene ²⁰⁶Pb/²³⁸U ages, 24 grains have positive ε_Hf(T) values up to +16. Whilst zircons of such ages are common in the Transhimalayan plutons, those showing high ε_Hf(T) values have been observed so far only in the Gangdese batholith. Our results, therefore, support the notion that by Late Miocene time the Yarlu Tsangpo, which flows past the Gangdese batholith in southeastern Tibet, drained into the Irrawaddy River. We attribute this river routing to not only regional topographic control but also the dextral movement of the Jiali-Gaoligong-Sagaing fault system that appears most active during the Middle Miocene. Subsequent reorganization of these mountain rivers was affiliated with headward erosion of the Brahmaputra River that eventually cut across the Namche Barwa Syntaxis and captured the Yarlu Tsangpo drainage to form the modern eastern Himalayan river system.
DE: 1040 Radiogenic isotope geochemistry
DE: 1100 GEOCHRONOLOGY
DE: 8102 Continental contractional orogenic belts and inversion tectonics
DE: 8150 Plate boundary: general (3040)
DE: 9320 Asia
SC: Tectonophysics [T]
MN: 2007 Fall Meeting