用高精度重磁电法研究古牧地构造地质结构

Application of High-Precision Gravity-Magnetic-Electric Prospectings to Study of Geologic Structures in Gumudi Area in Southern Margin of Junggar Basin

准噶尔盆地南缘不同时代地层之间密度、电阻率差异明显,重磁电勘探具有良好的地球物理条件。研究表明,古牧地构造为博格达山前褶皱冲断带的前锋构造,受阶梯状断裂控制,古牧地构造纵向上具多层构造特征,其中,浅层为紧闭型逆冲倒转背斜,中层为受阶状逆冲断层控制的屋脊状断块,深层为潜山披覆型冲断背斜;重力异常显示古牧地背斜西围斜可能是一完整的背斜构造,古牧地中深层构造和古牧地背斜西围斜评价为有利的油气勘探目标。

Because of the blind area existed in middle-deep seismic images, the understanding of the structural characters in Gumudi area is still unclear up to now. In view of obvious differences of density and resistivity of strata in different ages in southern margin of Junggar basin, there are good geophysical conditions for gravity-magnetic-electric prospectings. The study shows that Gumudi structure belongs to front structure of piedmont folded thrust belt in Bogda mountain. Controlled by step fractures, it is characterized by vertical multi-strata structures： the shallow strata assume tight overthrust inverted anticline; the middle strata appear in roof-like fault block controlled by step overthrust faults, and the deep strata are buried hill drape-like thrust anticline. The gravity anomaly displays that the west pericline of Gumudi anticline could be a complete anticline. It is concluded that the middle-deep structures and the west pericline in Gumudi area are favorable targets for petroleum exploration.