柴达木盆地西部深钻记录的晚中新世到早更新世的化学风化过程及控制机理研究

The relationships among tectonic uplift, climate change and continental chemical weathering is a long debated issue. The Qaidam Basin on the northeastern Tibetan Plateau provides an ideal location for studying the tectonic and climatic effects on the continental chemical weathering because the basin experienced strong tectonic deformation and enhanced aridification since the late Miocene. This proposal intends to systematically carry out phase-based element and Sr-Nd isotopic analyses using high quality continuous fine-grained lake sediments of the new acquired SG-1-b core (average core recovery of 93%, age ranging from 7.3 to 1.6Ma) in the western Qaidam Basin. The selected well-used proxies with clear indications in silicate fraction and Sr isotopes in evaporite and carbonate would be used to reconstruct catchment high-resolution silicate chemical weathering sequence. The trace elements and Nd isotopes are used to constrain the potential provenance change. Then we compare the reconstructed catchment silicate weathering records with provenance and basin shortening deformation history as well as regional and global climate records to evaluate the impacts of tectonic and climate on catchment chemical weathering, and thus providing important basis for further understanding of the relationships among tectonic uplift, climate change and continental chemical weathering.

长期以来关于构造隆升、气候变化和大陆化学风化的相互关系存在诸多争议。青藏高原东北部柴达木盆地晚中新世以来经历的强烈构造变形和剧烈干旱化使得该盆地成为研究构造和气候对化学风化影响的理想场所。本项目拟通过柴达木盆地西部新获取的723m中德联合深钻SG-1b连续细粒湖相岩芯(平均取芯率93%，年龄7.3-1.6Ma)为研究对象，对样品系统地开展基于相态（蒸发岩、碳酸盐和硅酸盐组分）的元素组成和Sr-Nd同位素分析。通过选用机理清楚的硅酸盐组分元素地球化学指标以及蒸发岩和碳酸盐Sr同位素重建高分辨率流域硅酸盐风化历史；通过微量元素组合以及Nd同位素分析，约束可能的物源变化；进一步对比流域风化记录与物源变化及盆地地层缩短变形历史以及区域和全球气候记录，揭示该时期构造与气候对流域化学风化的影响，从而为深入理解构造隆升、气候变化和大陆化学风化之间的关系提供重要依据。

长期以来关于构造隆升、气候变化和大陆化学风化的相互关系存在诸多争议。青藏高原东北部柴达木盆地晚中新世以来经历的强烈构造变形和剧烈干旱化使得该盆地成为研究构造和气候对化学风化影响的理想场所。本项目通过柴达木盆地西部新获取的723m中德联合深钻SG-1b连续细粒湖相岩芯(平均取芯率93%，年龄7.3-1.6Ma)为研究对象，对样品系统地开展基于相态（蒸发岩、碳酸盐和硅酸盐组分）的元素组成和Sr-Nd同位素分析揭示流流域风化及其控制因素。结果表明柴达木盆地西部7.3Ma以来流域物源相对稳定，约3.3Ma开始出现相对小幅物源变化。流域整体呈现出在3.6Ma开始的气候干旱化、流域硅酸盐风化强度减弱和湖面降低的长期一致性演化，该过程在第四纪加剧。碳酸盐和蒸发岩Sr同位素在3.6Ma整体降低，可能与干旱化背景下碳酸盐风化加强有关。柴达木盆地西部7.3Ma的气候变化和流域风化主要受控于全球变冷，区域构造的影响处于次要地位。