粒度分析方法在沉积环境研究中的运用——以东欢坨煤矿为例

Application of Grain Size Analysis in Sedimentary Environment Research—Taking Donghuantuo Coal Mine as an Example

摘要: 粒度分布特征是沉积岩的主要特征之一，也是沉积岩分类定名的定量指标，粒度大小能反映出沉积区的水动力强弱和搬运过程，可作为分析环境的依据，粒度能直接影响到沉积岩的物理性质。本文以东欢坨煤矿为研究区，以东欢坨煤矿补勘7井累深404~421 m岩芯为研究对象，通过岩石学研究方法，分析碎屑岩的成分、结构和构造等特点，结果表明：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，岩石碎屑颗粒分选中等，磨圆中等，发育孔隙式胶结，颗粒支撑，以点接触为主，其次为线接触。并通过对碎屑颗粒的粒度分布曲线分析，判段该地区的搬运方式滚动、跳跃、悬浮；水动力条件较弱；沉积环境为陆相氧化和沼泽还原沉积。

Abstract: Grain size is not only one of the main characteristics of sedimentary rocks, but also a quantitative index for classification and naming of sedimentary rocks. Grain size can reflect the hydrodynamic characteristics of sedimentary areas, and can also be used as a basis for analyzing and comparing the environment. Grain size can directly affect the physical properties of sedimentary rocks. This paper takes Donghuantuo Coal Mine as the research area, and the core of 404~421 m in depth of No.7 well in Donghuantuo Coal Mine as the research object. Through the petrological research method, the characteristics of clastic grain properties, rock association and sedimentary structure are analyzed, and the microscopic petrographic analysis and grain size analysis are carried out. The conclusion is that the main rock type of sandstone is medium fine grained lithic arkose; The main particle size is between 0.25~0.5 mm. The rock clastic particles are moderately sorted and rounded, with pore type cementation and particle support. Point contact is the main type, followed by line contact. Through the analysis of the grain size distribution curve of the clastic particles, the transportation mode of the area is judged as rolling, jumping and suspending; The hydrodynamic condition is weak; The sedimentary environment is continental oxidation and swamp reduction.