塔中北坡走滑断裂成因机理与油气成藏

塔中北坡发育一系列NE向走滑断裂。为了揭示走滑断裂形成机理及其对油气成藏的影响，在对走滑断裂几何学样式详细解析的基础上，运用物理模拟方法对塔中北坡NE向走滑断裂的演化过程进行了模拟。结果表明，在单一应力状态下，由于差异推挤和基底剪切共同作用，走滑断裂在平面和剖面上发育了不同的样式，沿断裂走向具有分段性特征。结合构造背景分析，认为塔中北坡走滑断裂成因机理受控于两种因素，即由于塔中Ⅰ号断裂带存在分段性，在加里东末期—海西早期北东向应力场作用下，使塔中隆起对北坡形成强度差异的推挤作用；其次，塔中北坡NE向基底断裂活动造成基底剪切作用，拖动上覆上奥陶统、志留系、泥盆系在左行力偶下运动。NE向走滑断裂的存在对塔中北坡油气成藏具有一定贡献：一方面走滑断裂会诱导高角度构造裂缝发育，从而沟通了储集空间，另一方面，走滑断裂的活动为塔中北坡多层系立体成藏提供了便利。

Mechanism of strike-slip faulting and hydrocarbon accumulation in northern slope of Tazhong area

A series of NE trending strike-slip faults developed in northern sloped of Tazhong area.In order to unravel the forming mechanism and its implication on hydrocarbon accumulation of strike-slip faults, detailed analysis upon geometric styles of strike-slip faults was performed, and the evolutional process of NE trending slip-faults in northern Tazhong area was simulated by using physical analogue model method.The results show that development of different planar and sectional structural styles of strike-slip faults is induced by differential pushing and basement shear effect under simple contractional stress field.Segmentation of characteristics is also observed along faults trending.It is concluded by physical analogue results integrated with structural background analysis that the forming mechanism of strike-slip faults in northern slope of Tazhong area was controlled by two factors.Firstly, the segmentation of Tazhong I fault gave the northern slope of Tazhong area a differential pushing stress in NE direction at the late Caledonian-early Hercynian.Secondly, NE trending basement faults activity in northern Tazhong area resulted in basement shear effect, which drag overlying upper Ordovician, Silurian, Devonian strata sinistrally.The existence of NE trending strike-slip faults contribute to hydrocarbon accumulation in northern slope of Tazhong area.On the one hand, high-angle structural faults development induced by strike-slip faults connects reservoir sections.On the other hand, faulting of strike-slip facilitates multi-layers hydrocarbon accumulation in northern slope of Tazhong area.