| Southern Longmenxia Profile is located in Guanghui town, which is to the northeast of Guangan city, eastern Sichuan Basin. Its structural position is on the west side of high and steep structures in East Sichuan, belong to the axis –anticline of the Huaying Mountain brush structures. There are continuous Triassic strata exposed surface. This paper choose Jialingjiang Formation in Longmenxia section as the research object, combining field observations with laboratory analysis, based on the theories of sedimentary petrology, carbonate sedimentology, lithofacies-paleogeography and so on, through the measured data of the outcrops, comprehensive using thin section identification, cathodoluminescence and other technical means, research the characteristics of the carbonate rocks and diagenesis of the study area. We have identified the components, structure and types of the rocks and briefly discussed the types of diagenesis here.The total thickness of Jialingjiang formation of Longmenxia profile is 669.44 meters,which is thicker than other areas of eastern Sichuan. Combining with the field profile measurement and the analysis of indoor thin section observation, we divided the Jialingjiang formation into four sections according to lithologic difference. In the first and the third section of the Jialingjiang Formation, limestone is the same main rock type and the thicknesses of the two sections are 319.04 m, 196.86 m. Dolomites and evaporite-solution breccias are the main rock types in the second and the fourth section of the Jialingjiang Formation, and the thicknesses of the two sections are 70.13 m, 83.41 m.Based on the results of field observations and thin section analysis, we consider that the rock types of the study area should be divided into three major categories of limestone, dolomite and salt breccia, and on this basis subdivided into 8 subclasses of sparry grain limestone, microcrystalline particles limestone, particle micrite-containing particles micrite, laminated micrite, vermiculate micrite, crystalline limestone, microcrystalline dolomite, crystalline dolomite. During Jialingjiang phase, the sedimentary facies of the study area are restricted platform and evaporation platform, and further divided into 3 subfacies of the lagoon, tidal flat and evaporation tidal flat on the basis of rock characteristics. During Jialingjiang phase, the sedimentary facies of the study area are restricted platform and evaporation platform based on the study of Petrological characteristics.Jialingjiang Formation has experienced complex diagenetic processes In the long geological history. The types of diagenesis are various, and mainly include mud crystallization, compaction, pressure solution, calcite cementation, dolomitization, recrystallization, fracturing, dissolution, silicification, degypsification, and formation of authigenic minerals such as pyrite, fluorite, celestite and so on. The general expression of elements migration is the losing of Sr and the acquisition of Mn、Fe during the diagenetic process.Mostly the cathodoluminance of dolostone is stronger than limestone because of the relatively higher content of Mn. |
