米仓山与大巴山交汇区构造分区与油气分布

Structural zonation and oil/gas distribution in intersecting area of Micang and Daba mountains

米仓山与大巴山交汇区经历了至少两期以上的构造复合,表现为近东西向的米仓山背斜叠加在南北向的大巴山冲断褶皱带上,形成以米仓山基底变质岩为核心的东西向叠加背斜褶皱;其次为大致呈近东西向的通南巴主体构造,由于受大巴山构造推覆的影响使其东段构造轴向发生旋转,整体改造为一个完整的北东向背斜构造。通过研究区10余条骨干剖面平衡剖面地层缩短率的计算,指出大巴山前缘和米仓山前缘沿山前带到盆地方向,地层缩短率由大到小。据此,可将大巴山前缘和米仓山前缘划分为强变形带、中变形带和弱变形带。各带在通南巴地区相互影响、相互叠加。从构造变形强度和成藏条件分析,米仓山前叠瓦冲断区带、黑池梁、涪阳坝和南阳场4个区块为研究区勘探最有利的正向构造区块。

The intersecting area of Micang and Daba mountains would have experienced at least two tectonic combina- tions.One is the superimposition of the nearly EW trend Micang mountain anticline on the NS trend Daba mountain thrust fold belt,resulting in the formation of EW trend superimposed anticlinal fold with the metamorphic basement of Mieang mountain as the core.Another one is the approximately EW trend Tongnanba major structure,affected by the nappe of Daba Mountain structure,the structural trend in the eastern section has been rotated,as a result,it has in- tegrally been reconstructed into a complete NE anticlinal structure.Formation shortening rates of balanced cross sec- tions are calculated from over 10 major sections in the study area.According to variation of formation shortening rate from large to small,strong,medium and weak deformation zones can be divided in the direction from both Micang and Daba mountain fronts to the basin.These deformation zones have interacted and superimposed with each other in Tongnanba region.Analyses of structural deformation intensity and reservoiring conditions show that the imbricated thrust fault zone,Heichiliang,Fuyangba and Nanyangchang in Micang mountain front are the most favorable positive blocks for exploration in the study area.