藏东南地区晚白垩世隆升剥蚀与构造动力学研究

Study on Late Cretaceous Uplift, Erosion, and Tectonic Dynamics in Southeastern Xizang

摘要: 藏东南地区地处青藏高原东南缘，是新特提斯洋演化、印度–欧亚板块早期汇聚及原青藏高原生长的关键构造节点，其晚白垩世(96~66 Ma)的隆升剥蚀过程记录了区域构造体制转换的核心信息，对理解青藏高原早期生长模式具有重要意义。本文系统整合前人低温热年代学、沉积学、岩浆岩与构造解析成果，开展多学科数据综合研究，建立藏东南及邻区晚白垩世三阶段隆升剥蚀与构造演化模型，明确区域隆升剥蚀的阶段性、空间差异及其动力学机制。研究表明，藏东南晚白垩世隆升剥蚀可划分为晚白垩世早期(96~80 Ma)初始隆升剥蚀、中期(80~67 Ma)快速隆升剥蚀、晚期(67~66 Ma)构造调整三个阶段，整体呈现阶段性增强与空间差异性分布特征。构造动力学分析显示，区域隆升剥蚀受新特提斯洋北向俯冲、洋脊俯冲–板片窗效应、弧后收缩与地壳加厚共同控制，其中洋脊俯冲引发的软流圈上涌与壳幔相互作用为核心驱动力，班公湖–怒江缝合带等先存构造薄弱带控制隆升剥蚀的空间格局。本文作为系统性综合研究，在已有工作基础上构建统一构造框架，可为青藏高原早期构造演化与造山带动力学研究提供更完整的理论依据。

Abstract: The southeastern part of Xizang is located on the southeastern edge of the Qinghai-Xizang Plateau. It is a key tectonic node for the evolution of the Neothetis Ocean, the early convergence of the Indian-Eurasian Plate, and the growth of the original Qinghai-Xizang Plateau. The uplift and erosion process in the Late Cretaceous (96~66 Ma) recorded the core information of the regional tectonic system transformation and is of great significance for understanding the early growth pattern of the Qinghai-Xizang Plateau. This paper systematically integrates the previous achievements in low-temperature thermochronology, sedimentology, magmatic rock and structural analysis, conducts a comprehensive study of multi-disciplinary data, and establishes a three-stage uplift and erosion and structural evolution model of the Late Cretaceous in southeastern Xizang and its adjacent areas, clarifying the phased, spatial differences and dynamic mechanisms of regional uplift and erosion. Studies show that the uplift and erosion of the Late Cretaceous in southeastern Xizang can be divided into three stages: the initial uplift and erosion in the early late Cretaceous (96~80 Ma), the rapid uplift and erosion in the middle stage (80~67 Ma), and the structural adjustment in the late stage (67~66 Ma). Overall, it presents the characteristics of phased intensification and spatial differential distribution. Tectonic dynamics analysis shows that regional uplift and erosion are jointly controlled by the northward subduction of the Neotethes Ocean, the subduction-plate window effect of the ridge, post-arc contraction and crustal thickening. Among them, the asthenosphere upwelling and crust-mantle interaction triggered by ridge subduction are the core driving forces, and the spatial pattern of uplift and erosion is controlled by the existing weak tectonic zones such as the Bangong Lake-Nujiang suture zone. As a systematic and comprehensive study, this paper builds a unified tectonic framework on the basis of existing work, which can provide a more complete theoretical basis for the research on the early tectonic evolution and orogenic belt dynamics of the Qinghai-Xizang Plateau.