准南地区前陆冲断带晚新生代构造变形特征与油气成藏

准南地区前陆冲断带晚新生代构造活动始于约24Ma,主要形成于10Ma以来,在此期间,前陆冲断带持续扩展,形成现今地表可见的三排褶皱冲断带,其中二、三构造带主要形成于近3Ma以来。准南冲断带晚新生代以来的变形强度自南向北逐渐减弱,变形时间由南向北逐渐接近现今,其中,齐古—喀拉扎地区的构造变形较弱,向两侧变形有所增强。准南前陆冲断带晚新生代构造变形特征显示,冲断带前缘、推覆体下盘和隐伏背斜及具有早期构造背景、晚期构造变形较弱的构造是油气成藏的有利部位,但二、三排构造带的构造形成时间较晚,可能是其油气丰度的制约因素之一。

Late Cenozoic structural deformation and its implication for petroleum accumulation in the southern Junggar thrust belt

The intense Cenozoic tectonism of the southern Junggar thrust belt initiated at about 24Ma before present, formed in recent 10Ma and associated with intense tectonic deformation. The structural deformation, rapid uplift and denudation in recent 10Ma led to the formation of foreland thrust belt including three structural belts, and the formation of the second and third structural belts mainly occurred in recent 3Ma. The deformation of the Late Cenozoic resulted in the relatively gentle deformation at Qigu-Kalazha area and widespread tectonic deformation transporting and retrogressing from south to north. The differential tectonic deformation indicated that the front of thrust belt was advantageous for hydrocarbon accumulation, although the timing of 3Ma was a restraint factor for a large scale of hydrocarbon accumulation. Moreover, the early structures with gentle remolding in the Late Cenozoic, the bottom wall of thrust block and buried structure also imply a favorable petroleum potential for prospecting in the southern Junggar thrust belt.