四川盆地自流井组陆相页岩石英成因研究

为了分析含气陆相页岩中石英矿物的成因、分布及其影响因素，以四川盆地自流井组含气页岩层段为主要研究对象，利用X射线衍射分析、普通薄片、扫描电镜、阴极发光、电子探针及元素地球化学分析测试手段，识别出陆源石英和成岩过程中形成的石英。陆源石英在阴极光下表现为棕色光，粒径较大。成岩过程中形成的石英在阴极发光下不发光，晶形较好，粒径较小。根据成岩作用的不同，将成岩过程中形成的石英细分为黏土矿物转化过程中形成的石英和硅质交代介壳边缘形成的石英。分析不同成因的石英分布特征发现，东岳庙段内石英矿物主要为陆源输入和黏土转化成因；马鞍山段内的石英主要为陆源石英；大安寨段内的石英则为硅质交代自生和陆源输入成因。在此基础上，总结了陆相页岩中不同成因石英的影响因素，包括沉积环境和地层压力。在沉积环境方面，随陆源物质输入的增加，陆源石英增加。同时，适合的湖水盐度，有利于介壳生物的生存，为硅质交代介壳形成石英提供物质基础。此外，地层的异常高压会抑制黏土转化，减少硅质析出，阻碍自生石英的沉淀。

The Genesis of Quartz in Ziliujing Nonmarine Shale,Sichuan Basin

Gas shale from the Ziliujing Formation in the Sichuan Basin was studied to investigate the genesis of quartz in continental shale and its distribution and influencing factors. Terrigenous quartz and quartz formed during diagenesis were identified using X-ray diffraction （XRD） analysis， observation of thin sections， scanning electron microscope cathodoluminescence （SEM-CL） and electron microprobe， combined with geochemical element test methods. Terrigenous quartz has a brown cathodoluminescence and large particle size， whereas quartz formed during diagenesis shows no cathodoluminescence， has a better shape and smaller size. Quartz formed during diagenesis is either formed at the edge of siliceous shells or during the transformation of clay minerals. Depending on its diagenesis， the quartz is formed at the edge of the silica-metasomatic shell or is formed during illitization. Analysis of the different forms found that the quartz in the Dongyuemiao member was mostly formed during illitization and from terrigenous input. In the Ma’anshan member it is mainly terrigenous； and in the Da’anzhai member the genesis is siliceous metasomatism and terrigenous input. Based on this， the influence of the different forms of quartz in nonmarine shale is summarized， taking depositional environment and formation pressure into account. In terms of depositional environment， the proportion of terrigenous quartz increases with increase in terrigenous input. At the same time， suitable salinity of the lake water is conducive to the survival of shells of organisms， which provides the material for the formation of silica in silica-metasomatic shells. In addition， abnormally high pressure inhibits illitization， and a decrease of silica precipitation hinders authigenic quartz precipitation.