柴达木盆地北缘冷湖七号地区下干柴沟组上段沉积—成岩特征

综合岩石学、矿物学和元素地球化学等研究方法,对柴达木盆地北缘冷湖七号地区下干柴沟组上段(E32)碎屑岩的岩石学特征、成岩作用、沉积微相以及沉积环境进行了综合研究.结果 表明:冷湖七号地区下干柴沟组上段碎屑岩以长石质岩屑砂岩为主,其次为岩屑质长石砂岩;孔隙类型多为原生粒间孔和粒间溶蚀孔,胶结物多为方解石;黏土矿物含量平均...

Sedimentary-diagenetic characteristics of the upper section of the Lower Ganchaigou Formation in Lenghu No.7 region,North Qaidam Basin

Based on the methods of petrology,mineralogy and elemental geochemistry,petrological characteristics,diagenesis,sedimentary microfacies and sedimentary environment of clastic rocks of the upper section of the Lower Ganchaigou Formation(E₃²)of Lenghu No.7 in the northern margin of Qaidam Basin were comprehensively studied.The clastic rocks are mainly feldspathic lithic sandstones,followed by lithic arkose;the pore types are mainly primary intergranular pores and intergranular dissolution pores,and the cement is mostly calcite;the average content of clay mineral is 15.0%,the content of illite is high,followed by chlorite and illite/montmorillonite mixed layer and the diagenetic environment is alkaline environment.Alkaline diagenetic environment is conducive to the formation of chlorite coating and calcite cement in the early diagenetic stage,the former increases the mechanical strength of the rock,inhibits the siliceous cementation,and is conducive to the preservation of primary intergranular pores;when the content of the latter is less than 12%,it is conducive to the intervention of acid fluid in the late diagenetic stage,resulting in the dissolution and formation of a certain amount of secondary dissolved pores,thus playing a certain role in improving the reservoir.Underwater distributary channel,distal bar and estuarine bar are developed,high quality reservoirs are developed in sand-bodies outside distal bar with high maturity of composition and structure.The comprehensive analysis results of element B,“equivalent B”and Co show that the sedimentary water body is continental fresh-brackish water with shallow water depth and strong hydrodynamic effect.