煤层顶部砂岩显微结构及地球化学特征：以东欢坨矿区古冶组为例
Microstructure and Geochemical Characteristics of Sandstone at the Top of Coal Seam: Taking the Guye Formation in Donghuantuo Mining Area as an Example

煤层顶部砂岩易于遭受风化作用，对生产和环境造成严重影响，在煤矿开采过程中，顶板砂岩的强蚀变影响着煤层开采、导水通道设置和瓦斯排逸。以东欢坨古冶组煤层顶板砂岩为研究对象，通过岩石学和地球化学研究的方法，开展煤层顶部砂岩显微结构及地球化学特征研究，取得以下认识：砂岩的岩石类型主要为中–细粒岩屑长石砂岩，主要颗粒粒度在0.25~0.5 mm之间，碎屑颗粒分选中等，磨圆中等，发育孔隙式胶结，颗粒支撑。样品中SiO2含量较高，在66.33%~74.63%之间，Al2O3/SiO2的值在0.156~0.256之间，表现出较高的成分成熟度。K2O/Na2O的值均大于1，样品中碱性长石的含量要高于斜长石。稀土元素指示轻稀土分异明显，Ce以及Eu元素均有轻微的负异常。顶部砂岩物源区为活动大陆边缘以及大陆岛弧构造环境，沉积环境主要为富氧的淡水环境，古气候为干热的气候环境。
The sandstone on the top of the coal seam is prone to weathering, which has a serious impact on production and the environment. In the process of coal mining, the strong alteration of the sand-stone on the roof affects the mining of the coal seam, the setting of water channels and the escape of gas. Taking Donghuantuo Guye Formation coal roof sandstone as the research object, through petrological and geochemical research methods, the microstructure and geochemical characteristics of the sandstone on the top of the coal seam were studied, and the following understanding was obtained: The rock types of sandstone are mainly medium-fine Granular detrital feldspar sandstone, the main particle size is between 0.25 and 0.5 mm, the sorting of detrital particles is well rounded, with developed pore-type cementation and particle support. The SiO2 content in the sample is relatively high, ranging from 66.33% to 74.63%, and the value of Al2O3/SiO2 is ranged from 0.156 to 0.256, showing a high degree of maturity. The values of K2O/Na2O are all greater than 1, and the content of alkaline feldspar in the sample is higher than that of plagioclase. Rare earth elements indicate obvious differentiation of light rare earth elements, and both Ce and Eu elements have slight negative anomalies. The source area of the top sandstone is the active continental margin and the continental island arc structure environment, the sedimentary environment is mainly oxygen-rich freshwater environment, and the paleo-climate is a dry and hot climate environment.