内蒙古二连盆地川井坳陷赛汉组泥岩地球化学特征

为探究内蒙古二连盆地川井坳陷赛汉组泥岩作为高放废物地质处置库备选围岩地质条件的适宜性，选取研究区内KZK2-6钻孔23个赛汉组泥岩样品开展了矿物组分、地球化学等分析测试，对赛汉组泥岩的矿物组分、沉积环境、源岩属性、构造背景等进行了探讨。研究结果表明：赛汉组泥岩以石英、黏土矿物、钠长石为主，其中以伊利石为主的黏土矿物平均质量百分数达21.2%;一定质量百分数的方沸石、白云石和黄铁矿凸显了其作为处置库围岩在核素吸附等方面的优势。主量元素以SiO₂、Al₂O₃、TFe₂O₃为主，贫MnO、P₂O₅和TiO₂。与大陆上地壳相比，微量元素Ga、Cr、Cu等元素稍有富集，而Ba、Sr略微亏损。稀土元素特征表现为轻重稀土分异明显，轻稀土富集，重稀土亏损，配分曲线呈明显“右倾”趋势，δEu明显负异常。物源为长英质和活动大陆边缘的混合来源，母岩以沉积岩和花岗岩为主并形成于大陆岛弧的构造背景。沉积环境指示赛汉组为海陆过渡的微咸湖相沉...

Geochemical characteristics of Saihan mudstone in Chuanjing depression, Erlian basin, Inner Mongolia

To explore the suitability of Saihan Formation mudstone in the Chuanjing Depression of Erlian Basin, Inner Mongolia, as an alternative surrounding rock geological condition for high-level radioactive waste geological disposal repository, this paper selected 23 samples of Saihan Formation mudstone from borehole KZK2-6 in the study area to carry out analysis and test on mineral composition and geochemistry and discussed the mineral composition, sedimentary environment, source rock properties and structural background of Saihan Formation mudstone. The results show that the mudstone of the Saihan Formation is mainly composed of quartz, clay minerals, and albite, and the average mass percentage of clay minerals dominated by illite is 21.2%. A certain mass percentage of analcime, dolomite, and pyrite highlights its advantages in nuclide adsorption as the surrounding rock of the repository. The major elements are mainly SiO2, Al2O3 and TFE2O3, and are poor in MnO, P2O5 and TiO2. Compared with the continental upper crust, trace elements such as Ga, Cr, and Cu are slightly enriched, while Ba and Sr are slightly depleted. Rare earth elements are characterized by obvious differentiation between light and heavy rare earth, enrichment of light rare earth, loss of heavy rare earth, obvious "right-leaning" trend of the distribution curve, and obvious negative anomaly of EU. The provenance is a mixture of the felsic and active continental margin, and the parent rocks are mainly sedimentary rocks and granite, which were formed in the tectonic background of the continental island arc. The sedimentary environment indicates that the Saihan Formation is a brackish lacustrine deposit with land-sea transition, and the overall anaerobic reduction environment is dominant, which is conducive to nuclide solidification. To sum up, the mudstone of Saihan Formation in Chuanjing Depression conforms to the geological and geochemical conditions of the alternative surrounding rock of the repository in terms of mineral composition and sedimentary environment and can be used as the key research object in the next research and development stage of the screening and evaluation of clay rock (mudstone) site in the geological repository of high-level radioactive waste.