利用碎屑矿物的释光热年代学方法研究珠江口盆地热演化史

Basin scale and lithospheric-scale thermal history information to understand the formation mechanism and evolution of sedimentary basins, and the evolution of basin paleo-geothermal field is extremely important within the basin scale studies of thermal history. Zhujiangkou Basin, located at the northern South China Sea continental margin, has been known to have complex geo-thermal evolution of structure. Both existing geodynamic models and paleo-temperature data limitations can not interpret its thermal structure evolution. The key reasons might be either both methods seldom consider the temporal factor in a geological time scale or lack of other independent evidences of geothermal field evolution of the basin. .Luminescence thermochronology, based on the combination of radiation effects and weak light detection techniques, can provide information for the thermal history of sedimentary basin evolution through indirect access to the evolution of environmental paleo-temperature field by studying the capture and escape law of crystal trapped charges, which is controlled by ambient temperature field, the radiation field and time field. The project intends to obtain the indicators of the relevant geo-thermal evolution of the Zhujiangkou Basin by applying the thermoluminescence and optically stimulated luminescence thermochronology of detrital minerals and apatite (uranium, thorium) / helium thermochronology analysis, supplemented by existing geothermal data associated in the basin scale as well as the associated geological time scale. As a result, this work helps to investigate the thermal structure evolution in the Zhujiangkou Basin since the Late Cenozoic aiming at the accumulation of scientific data related to thermal history inversion.

盆地尺度和岩石圈尺度的热史资料有利于理解沉积盆地的形成机理和演化过程，盆地地温场演变特征是盆地尺度内极为重要的热史研究资料。南海北部大陆边缘的珠江口盆地具有复杂的热史演化特征，现有地球动力学模型和今、古地温资料均存在局限，较少考虑地质历史时间这一维或者缺乏其他独立的盆地古地温演变特征资料的佐证。基于辐射效应原理和弱光探测技术的释光热年代学方法，通过研究受环境温度场、辐射场和时间场共同制约的矿物晶体陷阱中电荷的捕获和逃逸规律，可间接获得环境古温度场的演变信息，从而可以为沉积盆地热史演化研究提供资料。本项目拟利用碎屑矿物的热释光和光释光热年代学方法，研究且获取可表征珠江口盆地相关地层热史演化特征的相关指标，辅以磷灰石的（铀、钍）/氦低温热年代学分析，与已有地温资料相关联，在盆地尺度以及相关联的地质时间尺度内，探讨珠江口盆地晚新生代以来的热结构演变特征，为相关热史反演积累科学资料。

开展了针对新生代沉积盆地沉积物中碎屑矿物的释光分析方法与(铀、钍)/氦分析方法研究；系统开展典型地层的钻孔岩心中长石矿物的释光分析，磷灰石矿物的(铀、钍)/氦分析，试图为南海北部大陆边缘珠江口盆地复杂的热史演化特征提供科学资料，探讨珠江口盆地晚新生代以来的热结构演变特征。目前主要在低温热年代学研究方法学、典型钻孔地层岩心中碎屑矿物的低温热年代学一手数据取的获取，以及超高压影响盆地油气藏埋藏机制等方面取得了进展。研究工作开展的主要意义：盆地尺度和岩石圈尺度的热史资料有利于理解沉积盆地的形成机理和演化过程，盆地地温场演变特征是盆地尺度内极为重要的热史研究资料。基于辐射效应原理和弱光探测技术的释光热年代学方法，通过研究受环境温度场、辐射场和时间场共同制约的矿物晶体陷阱中电荷的捕获和逃逸规律，可间接获得环境古温度场的演变信息，从而可以为沉积盆地热史演化研究提供资料。