临兴地区本溪组--山西组含菱铁矿岩层的成因、演化及地质意义

临兴地区本溪组～山西组发育多层含菱铁矿岩层，但对其成因、演化及地质意义的研究较少，基于Y2-10及Y3-6井的岩心观察、薄片鉴定、常微量元素测试及低温液氮吸附实验，归纳了3种菱铁矿的垂向沉积组合，研究了含菱铁矿岩层的岩石学特征并划分出凝胶状、微粉晶、球形及菱面体4类微观形态，分析了菱铁矿的成因演化及地质意义。研究结果表明，研究区内菱铁矿形成需要富Fe与CO2、贫氧弱还原的海陆过渡环境，成矿铁质源于阴山-阿拉善古陆，CO2的来源则与微生物分解有机质、海相碳酸盐岩等有关；菱铁矿的成矿物质浓度、空间、渗透性及地球化学环境是影响其形态演化的重要因素；含菱铁矿泥岩比普通泥岩孔隙体积微小、数量更少且开放程度更低，以介孔和微孔为主，具有低孔低渗特性，可见其具有隔水阻气的特殊地质意义。

Origin, evolution and geological significance of siderite containing layers in C2b~P1s, Linxing region

There are multiple siderite containing layers in C2b~P1s in Linxing region, only few researches on its origin, evolution and geological significance. Based on lithological characteristics, thin section identification, macroelements and trace elements testing and low-temperature liquid nitrogen adsorption experiments of Y2-10 and Y3-6 wells, this research analyzed the sedimentary characteristics, genetic evolution and geological significance of siderite. The research summarizes three types of sedimentary assemblage of siderite-containing layers, concludes four types of micromorphology (gelatinous, microcrystalline, spherical and rhombohedral); and discusses the genesis and source area. The results show that the formation of siderite in the study area requires a transition environment of sea and land rich in Fe and CO2 and weak reduction of oxygen. The ore-forming iron element originates from the Yinshan Mountains-Alashan ancient land. The source of CO2 is related to microbial decomposition of organic matter and marine carbonate rocks. The concentration, space, permeability and geochemical environment of ore-forming material are the important factors affecting the morphological evolution of siderite. Siderite-bearing mudstone has smaller pore volume, less quantity and lower opening degree than ordinary mudstone, mainly mesoporous and micropore, with low pore and low permeability characteristics, which shows its special geological significance of water isolation and gas inhibition.