Dolomite Cathodoluminescence Characteristics And Diagenesis Of The Lower Cambrian Longwangmiao Formation Inthe Central Region Of Sichuan Basin

The central Sichuan basin Cambrian correlation group is China's important natural gas reservoirs discovered in recent years. In this paper, on the basis of drilling core intensive sampling, with a guide of such as sedimentary petrology, carbonate petrology theory, combining previous research results, synthetically used the casting thin sections observation, cathodoluminescence analysis, element analysis and other technical means, Studied in detail the petrological characteristics of the studied area dolomite, cathodoluminescence characteristics, the types of diagenetic fluid and diagenesis types, diagenesis sequence is established.In combination with drilling core observation, casting thin sections observation and cathodoluminescence analysis, the rock types in the study area is divided into powder-fine crystalline dolostone, rich Solution pores powder-fine crystalline dolomite, residual sand dust powder-fine crystalline dolostone and residual oolitic dolomite, and expounds on the various characteristics of rock.By trace element analysis and cathodoluminescence analysis found that: the Lower Cambrian Longwangmiao formation inthe central region of Sichuan Basin overall has high Fe(average 952×10-6), Mn(average 191×10-6) content,At the same time as a whole has a weaker cathode luminous intensity;Various types of dolomite luminous condition is different, of which: crystalline dolostone luminance is weakest, rich solution pores crystalline dolostone has the strongest luminance of three kinds of rock, the residual arene dolomite luminance between the two, with their respective content of Fe, Mn and Fe/Mn values correspond. Overall, cathodoluminescence of Longwangmiao formation is mainly controlled by the luminescence characteristics of rock structureCombined cathodoluminescence characteristics and characteristics of carbon and oxygen isotopes,we had a view that:Longwangmiao formation siltstones inthe central region of Sichuan Basin successively experienced complex fluid influence including penecontemporaneous stages syngenetic water,atmospheric fresh water and high salinity sea water at last of the stage, supergene stage atmospheric water,and middle—deep buried role in phase deep fluid.Longwangmiao formation siltstones in the central region of Sichuan Basin experienced a series of complicated diagenesis process consist of the destructive effects of compaction and late cementation,the constructive effects of pressure dissolution, early dolomitization, dissolution, hydrocarbon filling and tectonic disruption and the retention effect of the early cementation and the crystallization of clay.