青藏高原北部柴达木盆地北缘新生代风化剥蚀记录

The continental weathering and erosion are the main way of atmosphere, biosphere, hydrosphere and lithosphere interaction, and the important physical, chemical and biological process that may have resulted in enhanced atmospheric CO2 consumption, affected global carbon cycle and climate change, controlled and changed the evolution of surface landforms and material transfer. The weathering erosion and uplift of the Tibetan Plateau and their climatic effects are the international frontier science problem and the most typical representation of the interaction between the deep geological processes and the surface processes. The uplift of the plateau is directly manifested as the uplift of the mountain, the weathering erosion and transfer of material, and the subsidence and material accumulation in the basin, but the link to this process is weathering erosion. However, there is a lack of the systematic and continuous research on the Cenozoic weathering erosion history in the northern Tibetan Plateau at present. . The Qaidam Basin lies at the northeastern edge of the Tibetan Plateau, which is constrained by three large Asian mountain ranges: the Qilian Mountains to the north, the Kunlun–Qimantagh Mountains to the south, and the Altyn Mountains to the west. The Cenozoic deposition of the Qaidam Basin initiated following the Eocene, synchronous with the India–Asia collision, and the maximum sediment thickness is up to 15 km (Metivier et al. 1998). In this project, the northern margin of Qaidam basin is selected as the erosion-deposition system of the Mountain-Basin coupling, using the Cenozoic high-resolution magnetostratigraphic age, sedimentary flux, regional tectonic sequences and climate change obtained by previous and our research results, the purposes of the project expect to achieve the major weathering denudation events and chemical weathering history in the source regions since the Cenozoic through Cenozoic sedimentary characteristics (e.g., palaeocurrent, source, sedimentary facies and sedimentary flux) and the high-resolution chemical weathering indexes (such as CIA, CIW, Rb/Sr and Na2O/Al2O3) of clay component (<2 μm) of the northern Qaidam basin, combining with the detrtial zircon U-Pb and apatite fission track dating of Cenozoic sediments from the basin, and the apatite fission track and (U-Th)/He dating of rocks from the Qilian Shan. Then, by comparing with regional tectonic events, regional and global climate changes, the key factor of the major weathering denudation events and chemical weathering change should be discussed, and the results should provide significant evidence on understanding the relationships between the tectonics-climate-weathering erosion interaction in the northern Tibetan Plateau during the Cenozoic.

青藏高原隆升与风化剥蚀及其产生的气候效应是目前国际前沿的科学问题。高原隆起表现为山地抬升和物质风化剥蚀转移以及盆地下沉与物质堆积，联系这个过程的纽带是风化剥蚀作用。本申请选择青藏高原北部柴达木盆地北缘地区作为盆山剥蚀-沉积体系，利用我们和前人在该区域获得的新生代地层年代、沉积通量变化、重大构造事件和气候变化资料，针对高原北部缺乏系统的新生代风化剥蚀研究，采用盆地与山脉二个研究途径相结合方法，通过柴达木盆地北缘新生代沉积特征（古水流、物源和沉积通量等）以及高分辨率小于2µm粘粒组分CIA和Sr/Rb等化学风化指标系统研究，结合盆地碎屑与祁连山基岩磷灰石裂变径迹和(U-Th)/He年龄分析，获取该区新生代重大风化剥蚀事件和化学风化过程，并与该区重大构造和气候变化及全球深海氧同位素曲线对比，探讨青藏高原北缘风化剥蚀和硅酸盐化学风化的主控因素，为青藏高原构造-气候-风化剥蚀相互作用研究提供证据。

青藏高原隆升与风化剥蚀及其产生的气候效应是目前国际前沿的科学问题，而青藏高原北部缺乏新生代长序列风化剥蚀研究。项目采用盆地与山脉二个研究途径相结合方法，通过柴达木盆地北缘和酒泉盆地新生代古流向、物源变化、碎屑锆石U-Pb年代、磷灰石裂变径迹低温热年代、粘土矿物以及小于2µm硅酸盐粘粒组分化学风化指标（CIA以及K2O/Na2O、Na2O/Al2O3和Rb/Sr比值）系统研究，结合祁连山基岩磷灰石U-Th/He和裂变径迹热年代学分析，获得了青藏高原北缘柴达木盆地北部和酒泉盆地新生代连续长序列的化学风化过程，首次建立了青藏高原北缘53Ma以来完整的硅酸盐化学风化记录，揭示了青藏高原北缘新生代化学风化强度具古近纪减弱、新近纪早期阶段性增强和晚新近纪逐步减弱的变化规律。通过其与该区重大构造和气候变化及全球深海氧同位素曲线对比分析，认为青藏高原北缘新生代化学风化强度变化受气候与构造双重控制，其中全球气候变化为主控因素。即青藏高原东北部硅酸盐风化强度古近纪减弱主要受全球变冷控制、新近纪早期增强可能与构造抬升使东亚夏季风加强有关以及新近纪晚期逐渐减弱与全球变冷和区域干旱化加强有关。同时揭示了祁连山新生代60-50、42-36、~22、15-8和~2.1Ma五次构造驱动的重大快速剥露事件。这些研究成果不仅对青藏高原构造-气候-风化剥蚀相互作用研究提供了证据，而且对祁连山新生代构造隆升过程的研究具重要参考价值。