川东北地区下三叠统飞仙关组鲕滩白云岩成因

基于前人大量的研究成果，结合薄片观察和地球化学分析，研究了川东北地区下三叠统飞仙关组鲕滩白云岩的成因。结果认为：①该区主要有混合水白云石化和埋藏白云石化两种白云岩成因类型，并建立了研究区鲕滩白云石化模式；②混合水白云石化从地表一直延续到浅埋藏期，是本区主要的白云石化成因类型；③埋藏白云石化主要是在早期混合水白云石化的基础上，对白云石化程度的调整和加强，多期白云石化作用的叠加形成了现今厚度较大、分布面积较广的鲕滩白云岩；④海平面的变化直接影响鲕滩所经历的成岩环境及后期的成岩流体性质，是控制鲕滩白云石化最主要的因素；⑤差异压实作用是埋藏期白云石化流体运移的主要驱动力，开江-梁平海槽中泥页岩和滩后蒸发环境沉积物中高Mg²⁺/Ca²⁺比值的压实水，正是通过这种差异压实作用进入鲕滩储集体，为埋藏期白云石化提供了物质来源。

DOLOMIZATION GENETIC OF THE LOWER TRIASSIC FEIXIANGUAN GROUP OOLITIC BEACH IN NORTHEAST SICHUAN BASIN

On the basis of a large number of previous studies, the geological data about the observations about thin sections, and geochemical analysis, this paper carried out the research on the dolomitization origin of the Lower Triassic Feixianguan formation in Northeast Sichuan Basin. The study showed that (1)there are two kinds of dolomitization in Feixianguan formation, i.e., mixed water and burial dolomitization. (2)The mixed water dolomitization was a main genetic type playing a dominating role from syndiagenesis to eodiagenesis in the area. (3)The burial dolomitization took place based on the mixed water dolomitization, and adjusting or strengthening the degree of dolomitization. The formation of the thick and extensive dolomite of oolitic beach lied on polyphase dolomitization. (4)Sea level change was the uppermost factor of dolomitization of oolitic beach, which directly affected the diagenetic environment and the characteristics of diagenesis fluids of oolitic beach. (5)Abnormal pressure was that the main actuating force of hydrocarbon migration in burial dolomitization. Compaction water with high ratio of Mg2+/Ca2+ entered into oolitic beach reservoir by the abnormal pressure in the shale of Kaijiang Liangping oceanic trough and sediments of evaporitic environment behind oolitic beach, and provided huge source for burial dolomitization.