青藏高原中部是否存在一个大的古近纪盆地?

Understanding the growth history and mechanism(s) of the Tibetan plateau have fundamental implications on the studies of landscape forms and its evolution, and the interactions between surface processes and deep lithospheric processes. Despite this importance, no consensus has been reached on this issue. This is illustrated by the two end-member models: (1) the plateau grew sequentially from south to north the (independent basin model); (2) early plateau uplift occurred in the south (Lhasa and Qiangtang terranes) and north (Qilian thrust belt) trapping a large basin in the intervening region (the contiguous basin model). A first-order problem is the lack of detailed knowledge on spatial and temporal development of the Eastern Kunlun Range together with its flanking sedimentary basins. This project intends to focus on the central Eastern Kunlun Range together with its flanking sedimentary basins' margin, and integrates tectonic geomorphology analysis, balanced section, and fission track, in order to quantitatively analyse when did the initial tectonic topography of the Eastern Kunlun Range begin to form and its structural characteristics. Together with basin sedimentary analysis, U-Pb detrital zircon dating, we intend to establish stratigraphic correlation and provenance analysis of the Eocene to Miocene strata in the study area. We conduct an integrated study to detect if there was a large Paleogene basin in central Tibetan plateau, and further discriminate various end models of plateau growth history and mechanism(s).

理解青藏高原的生长历史和形成机制对研究活动造山带地貌形态和演化、以及地表过程和深部地球动力学过程之间相互作用具有重要意义, 但尚未形成统一认识，争议焦点在于两种端元模型：（1）独立盆地模型认为高原是从南到北顺序生长；（2）连续盆地模型认为青藏高原的早期隆升发育在高原南部（拉萨和羌塘地块）和高原北部（祁连逆冲断层带），中间发育一个大的盆地。因此，青藏高原中部东昆仑山和两侧盆地的时空关系是研究青高原生长历史和形成机制的关键切入点。本项目选取东昆仑山中部以及两侧盆地边缘为研究对象，综合运用构造-地貌分析、平衡剖面和裂变径迹等方法定量分析东昆仑山构造地貌何时开始形成及其构造特征。结合盆地沉积分析以及U-Pb碎屑锆石测年方法，进行研究区始新世-中新世地层对比和物源分析，从而进一步探讨青藏高原中部是否存在一个大的古近纪盆地，为区分新生代青藏高原生长形成的不同模型提供重要证据和约束。

理解青藏高原的生长历史和形成机制对研究活动造山带地貌形态和演化、以及地表过程和深部地球动力学过程之间相互作用具有重要意义, 但尚未形成统一认识，争议焦点在于两种端元模型：（1）独立盆地模型认为高原是从南到北顺序生长；（2）连续盆地模型认为青藏高原的早期隆升发育在高原南部（拉萨和羌塘地块）和高原北部（祁连逆冲断层带），中间发育一个大的盆地。因此，青藏高原中部东昆仑山和两侧盆地的时空关系是研究青高原生长历史和形成机制的关键切入点。本项目选取东昆仑山以及两侧盆地边缘为研究对象，综合运用构造-地貌分析、平衡剖面、裂变径迹等方法定量分析东昆仑山的快速隆升开始时间晚于20 Ma，结合盆地沉积分析以及U-Pb碎屑锆石测年方法，进行研究区晚中生代-新生代地层对比和物源分析，进一步支持了青藏高原中部存在一个大的古近纪盆地。新生代昆仑断层的活动及其应力分布特征与昆仑断层的顺时针旋转和“书斜”断裂体系的围岩特性相关，建立了青藏高原北部南-北向右行剪切模式，进一步提出三叠纪缝合带为新生代昆仑断裂系统的发育提供有利条件的假说。通过平衡剖面恢复和断层系几何换算，表明东昆仑西缘挤压变形无法为阿尔金断裂约10 mm/y的左行滑动速率产生明显的贡献