莺歌海盆地深部流体幕式活动历史：来自方解石和伊利石年代学的约束

高温高压背景下流体演化历史及油气成藏动力学研究是当今盆地流体研究中的薄弱环节。莺歌海盆地是我国目前已知最典型的高温高压盆地，盆地深部流体活动强烈，流体活动与深部地质演化和油气幕式成藏关系密切，然而尚没有学者对深部流体展开过系统的年代学分析。前期研究表明莺歌海盆地粗砂岩中自生伊利石颗粒大且纯度高，地层中还发育一些后期充填的方解石脉，是开展伊利石和方解石定年的理想对象。本项目拟采用最新研发的激光原位方解石U-Pb定年和自生伊利石Rb-Sr及Ar-Ar定年技术，共同限定深部流体活动期次和各期次流体活动精确年代，并结合微量元素、稳定同位素和Sr同位素分析，确定流体来源、温度和演化特征。预期成果不仅可以查明高温高压盆地深部流体演化过程，揭示流体活动对天然气幕式成藏的控制作用，深化高温高压地区油气成藏动力过程的认识；而且可以服务于莺歌海盆地油气勘探进程，并有望在类似含油气盆地中推广应用。

In the research field of basin fluids, few studies have focused on the fluid flow history and its controlling effect on hydrocarbon accumulation process in the sedimentary basins that are characterized by high temperature and high pressure. Yinggehai Basin is the most typical high temperature and high pressure sedimentary basin in China with intensive deep-sourced fluid flow activity. The previous studies have identified multiple fluid flow events in the Yinggehai Basin, suggesting a close relationship between fluid flow activity and geological evolution in deep basin as well as the process of hydrocarbon accumulation. However, no systematic geochronological research of fluid flow events in the Yinggehai Basin has been carried out so far. There are many calcite veins developed in the drilling cores, and the authigenic illite formed in the coarse sandstones is over 1.5 μm in length with high purity. These observations indicate that the geochronological studies of calcite veins and authigenic illite can be used to reconstruct the fluid flow history of the Yinggehai Basin. In this proposal, we will conduct both laser-ablation in situ U-Pb dating of calcite veins and Rb-Sr and Ar-Ar dating of different size fractions of authigenic illite to determine the periods of fluid flow activities and to constrain the precise ages of the fluid flow events in the Yinggehai Basin. Then a systematic geochemical studies (REE, stable isotopes and Sr isotope) will be carried out to determine the original, temperature and evolution process of the basin fluids. The proposed study can not only shed significant insights into the geologic processes of deep-sourced fluids, but also reveal the controlling effect of deep-sourced fluid flow on hydrocarbon accumulation process in the high temperature and high pressure sedimentary basins, the results of which have important implications for understanding of hydrocarbon accumulation process in the high temperature and high pressure sedimentary basins. Moreover, the research results are of great significance for the hydrocarbon resources exploration in the Yinggehai Basin, and the methods used in this study are of great value to be applied in the other petroliferous basins which have geological conditions similar to the Yinggehai Basin.