Petrology Characteristics And Diagenesis Of Rocks In Feixianguan Formation Of Lower Triassic,Qiaoting Profile Of Sichuan

The Feixianguan Formation of lower Triassic is one of the largest resources formation in Sichuan Basin. Puguang,Luojiazhai,Tieshanpo,Dukouhe and some other mid-large gas fields were discovered one after another by predecessors in Feixianguan Formation oolitic beach in northeast Sichuan.These gas fields are mainly distributed in the south edge of the Kaijiang–Liangping trough,while research in the north rim region is less.Chosing Nanjiang-Qiaoting section which is located to the north rim of the Kaijiang–Liangping trough,combining the outdoor work such as Field profile measurement,field description and sample collection with the indoor thin section identification,cathodoluminescence,scanning electron microscopy such microscopic research methods, basing on the theories as carbonate sedimentology,paleontology,diagenesis and other related theory,we have systematiclly researched the characteristics of petrology and diagenesis of the Feixianguan Formation in Qiaoting section.In the wild,according to the lithology,structure,the structure and the occurrence of the strata characteristics, determine the group of the top and bottom boundary of feixianguan Fomration, Feixianguan Fomration is grouped into four sections. In the first and third section of Feixianguan Formation, the main rock type is green gray light gray carbonate rocks. In the secend and fourth section of Feixianguan Formation, they are mainly purple red muddy limestone and calcareous mudstone.The carbonate rocks of the Feixianguan Formation of lower Triassic are composed by carbonate minerals,idio-noncarbonate minerals and terrigenous detritals. Carbonate minerals are consisted of calcites and dolomites. Idio-noncarbonate minerals are include authigenic quartz, pyrite and Celestine. Terrigenous detritals are comprise of quartz and feldspar.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 argillaceous rocks,and on this basis subdivided into subclasses of grain limestone, microcrystalline particles limestone, micrite, powder dolostone, grain dolostone, calcareous mudstone.According to some special rock fabric and diagenesis characteristic, we have divided diagenetic environment of the Feixianguan Formation : infraneritic environment, atmospheric fresh water seepage diagenetic environment, fresh water phreatic environment, buried environment,epidiagenesis environment.The main diageneses of the carbonate rock of the interesting area include : micritization, cementation, dissolution, compaction and pressure solution, recrystallization, burst effect and sedimentation, pyritization and silication and so on, and discussed diagenetic evolutionary series of sediments.