构造热事件对伊利石形成过程的控制：以北部湾盆地岩浆侵入地区为例

自生伊利石是碎屑岩成岩时期形成的粘土矿物，以往研究对热事件发育地区自生伊利石的形成过程涉及较少。北部湾盆地岩浆侵入地区存在明显的区域性热异常，粗砂岩中自生伊利石颗粒大且纯度高，是开展年代学分析的理想对象。本项目拟使用“逐步缩小粒径”法分选出同一砂岩样品中不同粒径的自生伊利石样品，完成样品纯度检验，进而通过系统的矿物学、Rb-Sr和K-Ar年代学以及微量元素分析，查明自生伊利石形成过程及其物理化学条件的变化。并利用Ar-Ar和锆石U-Pb定年手段，确定岩浆侵入年代和期次。在此基础上，通过对比岩浆侵入年代和自生伊利石的年龄分布特征，揭示构造热事件与伊利石形成过程二者之间的响应关系。伊利石形成和烃源岩成熟都是盆地热效应的产物，预期研究成果不仅可以揭示构造热事件对自生伊利石形成过程和烃源岩快速成熟生烃的控制作用，而且对北部湾盆地油气资源评价具有指导意义，并有望在类似含油气盆地中推广应用。

Authigenic illite is an important component part of clay minerals formed during diagenetic period in sedimentary basins. In previous studies, little attention has been paid to the formation process of authigenic illite in the regions where tectonic thermal events developed. The magma intrusion regions developed in the Beibuwan Basin, South China Sea are characterized by regional thermal anomaly. The authigenic illite formed in the coarse sandstones in the regions is over 1.5 μm in length with high purity, suggesting that it is particularly suitable for geochronologic dating. In this proposal, different size fractions of authigenic illite will be separated from Palaeogene coarse sandstones using the "step-reduce particle size" method, followed by a series of purity inspections. Then a systematic mineralogical, geochemical and Rb-Sr, K-Ar geochronological study will be carried out to better understand the formation process of authigenic illite, and to investigate physicochemical conditions during this process. In addition, magma intrusion history will be determined by Ar-Ar and zircon U-Pb dating of the magmatic rocks intruded within the Paleogene Liushagang Formation. Comparisons of age distributions between authigenic illite and magmatic rocks will be used to reveal the response relationship between regional thermal events and the formation processes of authigenic illite. Since both the formation of authigenic illite and the maturity of hydrocarbon source rocks are controlled by heating effect, the proposed study can not only shed significant insights into the controlling effect of thermal events on the formation processes of authigenic illite and the rapid maturity of hydrocarbon source rocks in the regions where thermal events develop, but also provide important guide to hydrocarbon resources evaluation in Beibuwan Basin. The research methods and results are of great value to be applied in the other petroliferous basins which have geological conditions similar to Beibuwan Basin.