应用扫描电镜与X射线能谱仪研究柳江盆地上石盒子组砂岩孔隙与矿物成分特征

摘要

Liujiang Basin is a famous geologic relic national nature reserve in china located at foot of Yanshan mountain in Qinhuangdao city.Petrological study on Upper Shihezi Formation of Permian system of Liujiang Basin Focuses mainly focuses on the macro-scale geological observation and lacks research on the characteristics of its pore and mineral components.Based on the field observation of outcrops and the measured sections the author carried out SEM (scanning electron microscope)and X-ray Spectrometry analysis on samples and summarized up the pore and mineral component characteristics.The results show that Upper Shihezi Formation in Liujiang Basin is mainly a binary structure series of conglomeratic sandstone and medium sandstone/interbed mudstone and siltstone.Under scanning electron microscope are recognized two types of pore,i.e.,the primary pore and secondary pore and the secondary pore can be classified into Intergranular dissolved pore,intragranular pore,microfissure and intergranular micropore according to the position distribution and morpholohy.Minerals in sandstones are mainly quartz and feldspar,then kaolinite and illite suggesting that sandstone of Upper Shihezi Formation is the product of middle diagenetic stage.%柳江盆地是国家级地质遗迹自然保护区,位于河北省秦皇岛市北部的燕山脚下.该区内的二叠系上石盒子组砂岩的岩石学研究工作多集中于宏观野外地质观测,缺少微观尺度下对上石盒子组孔隙特征和矿物组分特征的研究.本文在野外地质观察与剖面实测基础上,采用扫描电镜和X射线能谱测试,分析了柳江盆地上石盒子组砂岩的孔隙特征与成分特征.结果表明,柳江盆地上石盒子组以含砾粗砂岩、中砂岩与粉砂岩-泥岩互层为主,具有“二元结构”.扫描电镜下观察发现上石盒子组砂岩孔隙包括原生孔隙和次生孔隙两大类,次生孔隙依据孔隙形态与分布位置又可分为粒间溶孔、粒内溶孔、微裂隙和晶间微孔.砂岩矿物组成含量最多的矿物为石英和长石,其次为高岭石和绿泥石等黏土矿物;黏土矿物的种类组合特征表明,上石盒子组砂岩处于中成岩阶段早期.