拉萨地体大型剥蚀面形成时代及过程的低温年代学示踪

青藏高原地貌面的形成时代及过程作为青藏高原研究的核心问题之一，对恢复青藏高原的隆升历史具有重要意义。不过前人对青藏高原面的认识大多基于定性研究，而缺乏定量化的约束。本研究拟聚焦在拉萨地体夹持于林子宗火山岩与塔克那组地层之间的大型剥蚀面，该剥蚀面在拉萨以西被林子宗火山岩所埋藏，而在拉萨以东为基岩暴露的剥蚀面。本项目拟对拉萨以西埋藏剥蚀面进行详细的野外调查，通过对剥蚀面中保存的古土壤进行氧同位素研究以重建该剥蚀面形成时的古高度。同时，对拉萨以东暴露基岩剥蚀面进行数字高程地貌分析，甄选沿该剥蚀面暴露于地表的花岗岩体，通过野外系统采样，以低温热年代学实验技术为主要手段（锆石和磷灰石的裂变径迹和（U-Th）/He测年），借助热史模拟方法，定量刻画该剥蚀面T-t演化轨迹，揭示拉萨地体以东大规模剥蚀面的形成时代及演化过程，结合该剥蚀面形成时的古高度，制约碰撞后拉萨地体隆升幅度和机制。

The research of timing and evolution of surfaces on the Tibetan Plateau is one of the key questions to understand the uplift history of Tibetan Plateau.However,privous studies are almost qualitative rather than quantitative. We focus on the large-scale denudation surfaces between the Linzizong volcanic rocks and the Takena Formation in the Lhasa terrene, southern Tibet. Surfaces west of Lhasa were buried by the Linzizong volcanic Formation whereas erosion surfaces east of Lhasa were exposed on the granitic bedrocks.Detailded field investigations will be processed in the western of Lhasa to take paleosoils near the surfaces for modeling paleo-elevations during surfaces formation.The low temperature thermochronology such as zircon and aptite dating by both fission-track and (U-Th)/He methods are processed during this study,accomppanied by DEM analysis of exposed erosion surfaces in eastern Lhasa and field investigations in order to select the granitic batholiths cut by this large-scale denudation surfaces.By thermal modeling,we try to depict its T-t thermal history in details and it will shed light on the timing and evolution of this large-scale denudation surfaces.Combined with paleo-elevations suggested by paleosoil oxygen isotopes,uplift history of Lhasa terrane will be constrainted after the India-Asia continental collison.