Division of volcanic eruption stages and distribution patterns of volcanic rocks in Yingcheng Formation of Xujiaweizi fault depression, Songliao Basin
Based on a large number of drilling cores, thin sections, well logs, isotope age and three-dimensional seismic data, the coal-bearing pyroclastic sedimentary interlayer of the Ying 2 Member was used as the standard layer, and the volcanic stratigraphic interface was identified through well log curves, combined with the Gd obtained from ECS logs. and Ti elements to identify the type of volcanic stratigraphic interface, and establish the "three sections and six phases" volcanic stratigraphic sequence of the Yingcheng Formation in the Xujiaweizi Fault Depression in the northern Songliao Basin. On this basis, the characteristics of the volcanic eruption phase interface are summarized, and the Yingcheng Formation sequence is discussed. The relationship between the distribution of volcanic rocks in the Cheng Formation and deep faults. The results show that the lithology of the three phases of the Ying 1 Member from bottom to top is "intermediate basic lava/sandy conglomerate→acidic (clastic) lava/volcaniclastic rock→acidic Lava/Pyroclastic Rock"; the lithology of the three phases of the Ying3 Member from bottom to top is "acidic lava→medium-basic lava→acidic acid (clastic) lava/volcaniclastic rock occasionally intercalated with intermediate-basic lava "; The interfaces between periods are mainly weathering crusts, lithological interfaces and interlayers of re-transported sediments; the stratigraphic interfaces within periods are usually small weathering crusts of the same lithology, weathered alteration zones and volcanic debris interlayers; T4 in Xudong area Two sets of volcanic rocks with obviously different occurrences developed between the -1 and T4 interfaces are the products of different periods of volcanic eruptions in the Ying 1 Member; the Ying 1 Member is mainly distributed in Xudong, Xuxi and Shengping-Songzhan areas, and is not developed in the Anda area; from the early In the late stage, the volcanic eruption center migrated from south to north, and was controlled by the Xuzhong Fault → Xuzhong Fault and the southern part of the Xudong Fault → the southern part of the Xudong Fault; the third section of Ying is mainly distributed in the Anda, Shengping-Songzhan and Xuxi areas. It is not developed in the eastern area; the volcanic rocks of the Ying3 Member in the northern part of the fault depression are controlled by the Xuxi Fault → Xuxi Fault and Xudong Fault → Xuxi Fault and Xudong Fault from early to late stages; the volcanic rocks in the southern part of the fault depression are mainly controlled by the Xuzhong Fault and Xudong Fault. Commonly controlled by the Xuxi fault.