东喜马拉雅构造结快速隆升时期:来自缅甸中央盆地沉积学证据  

Rapid Uplift Period of Eastern Himalayan Syntaxis:Evidence from Sedimentology in Central Myanmar Basin

作　　者：鲁毅 崔宇驰 Si Si Thu Kyaw Kyaw Khing Myo Min Aung 朱伟林[1] 邵磊[1] Lu Yi;Cui Yuchi;Si Si Thu;Kyaw Kyaw Khing;Myo Min Aung;Zhu Weilin;Shao Lei(State Key Laboratory of Marine Geology,Tongji University,Shanghai 200092,China)

机构地区：[1]同济大学海洋地质国家重点实验室,上海200092

出　　处：《地球科学》2022年第7期2573-2585,共13页Earth Science

基　　金：国家自然科学基金重点项目(No.92055203);国家自然科学基金面上项目(No.42076066)。

摘　　要：东喜马拉雅构造结快速隆升时间以及雅鲁藏布江和伊洛瓦底江是否曾经相连已经争论了超过半个世纪.采用锆石U-Pb年代学等方法,对缅甸中央盆地新生代地层的“源-汇”路径开展研究.缅甸中央盆地始新统发育大量铬尖晶石、各坳陷的锆石年龄谱各不相同,表明该时期沉积物以盆地周边隆起为主要物源,不存在统一的源区;渐新世之后,源自区域变质岩的重矿物组合比例逐渐增加,盆地各坳陷碎屑锆石年龄谱特征趋于一致,均以40~70 Ma的主峰以及80~110 Ma次峰为特征,表明沉积物源区进入抹谷变质带,伊洛瓦底江雏形已经形成;由于缅甸中央盆地渐新统至下中新统完全没有喜马拉雅造山带信息,认为该时期雅鲁藏布江-伊洛瓦底江并未相连.晚中新世-更新世,喜马拉雅造山带特征组合十字石和蓝晶石以及110~130 Ma年龄峰的出现,表明伊洛瓦底江已经侵蚀到东喜马拉雅构造结,达到现今流域规模.因此,东喜马拉雅构造结快速隆升的时间大约在晚中新世.Rapid uplift period of formation of the eastern Himalayan syntaxis and the hypothesis of Tsangpo-Irrawaddy River connection have been debated for over half a century.A combination of detrital zircon U-Pb chronology and heavy mineral assemblages was employed to investigate the“ source to sink”pathways of Cenozoic strata in Central Myanmar Basin(CMB).The Eocene sediments indicate an intrabasinal provenance and no uniform source area with the presence of large amounts of Chromian spinel as well as the heterogeneity of zircon age spectra between all depressions.Since Oligocene,it is found that local-derived source was gradually replaced by Mogok Metamorphic Belt(MMB)and Irrawaddy River began to develop,which is revealed by zircon age spectra in all depressions tending to be identical(with 40-70 Ma at major peaks and 80-110 Ma at secondary peaks) and heavy mineral assemblages derived from regional metamorphic rock constantly increasing.In addition,due to lack of signal of Himalayan orogenic belt in Central Myanmar Basin,it is believed that there is no possibility of TsangpoIrrawaddy connection during Oligocene and Early Miocene.In Late Miocene-Pleistocene,the occurrence of granatite and kyanite and 110-130 Ma age peaks representing Himalayan orogenic belt suggest that the Irrawaddy River had eroded to the eastern Himalayan syntaxis and attained a near-modern configuration of drainage networks.Consequently,rapid uplift of eastern Himalayan syntaxis should have occurred in the Late Miocene-Pleistocene.

关 键 词：青藏东南缘 缅甸中央盆地 河流演化 锆石U-PB定年 重矿物 物源分析 地质年代学 

分 类 号：P534[天文地球—古生物学与地层学] P597.3[天文地球—地质学]