内蒙古化德地区三面井组沉积环境及大地构造背景研究

Study on the Sedimentary Environment and Tectonic Setting of the Sanmianjing Formation in the Huade Area, Inner Mongolia

摘要: 在进行内蒙古1:5万区域地质调查工作中，对内蒙古化德县同乐村北东一带的下二叠统三面井组粉砂岩进行了粒度分析。结果表明，样品粒度多分布在4.5 Φ左右，表明岩性以细砂和粉砂为主，样品标准偏差多在0.6~0.9之间，表明分选性较好；偏度多为0.1~1之间，峰度多为2~4，样品粒度多大于3 Φ，显示以悬移为主，可见少量跃移。概率累积曲线图多为二段式具浅海相砂岩特征。结合岩石组合类型、沉积构造特征和粒度分析结果，综合得出三面井组为滨–浅海相沉积，且为古亚洲洋向华北陆缘俯冲背景下的弧后盆地沉积。

Abstract: During the 1:50,000 regional geological survey in Inner Mongolia, grain size analysis was conducted on feldspathic lithic sandstones from the Lower Permian Sanmianjing Formation in the northeastern area of Tónglè Village, Huade County, Inner Mongolia. The results indicate that the grain sizes of the samples are mostly distributed around 4.5 Φ, suggesting the lithology is predominantly fine sand and silt. The standard deviation of the samples mostly ranges from 0.6 to 0.9, indicating relatively good sorting. The skewness is mostly between 0.1 and 1, and the kurtosis is mostly between 2 and 4. The grain sizes are mostly greater than 3 Φ, indicating a dominance of suspended transport with a minor presence of saltation. The probability cumulative curves are mostly two-segmented, characteristic of shallow marine sandstones. Based on the rock assemblage types, sedimentary structures, and grain size analysis results, it is comprehensively concluded that the Sanmianjing Formation represents a littoral-shallow marine sedimentary environment, deposited in a back-arc basin under the tectonic setting of the Paleo-Asian Ocean subducting beneath the North China margin.