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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。
Based on a large number of previous studies, combined with the observation of thin sections and geochemical analysis, the genesis of the oolitic dolomite in the Lower Triassic Feixianguan Formation in northeastern Sichuan was studied. The results show that: (1) There are two dolomite types of mixed dolomitization and burial dolomitization in this area, and the dolomitization model of oolitic beach is established in the study area. (2) The dolomitization of mixed water extends from the surface to the shallow burial period The main dolomitization type; ③ burial dolomitization is mainly based on the early mixed dolomitization, the adjustment and enhancement of the degree of dolomitization, the superimposition of multi-stage dolomitization now formed a larger thickness, the distribution area is more Wide oolitic beach dolomite; ④ sea level changes directly affect the diagenetic environment experienced by the oolitic beach and the later diagenetic fluid properties, which are the most important factors controlling dolomitization of the oolitic beach; ⑤Differential compaction is the burial dolomitization fluid The main driving force for the migration is the high Mg2 + / Ca2 + ratio of compacted water in the shale-levee of the Kaiping-Liangping Trough and the depositional environment of evapotranspiration behind the beach. It is because of this differential compaction that the water enters the oolitic beach reservoirs as Burial dolomitization provides a material source.