鲁西隆起晚中生代以来北西向正断层特征及物理模拟

Characteristics of NW-trending Normal Faults and Physical Modeling since Late Mesozoic in West Shandong Uplift,China

鲁西隆起区伸展构造极为发育，通过野外地质调查对隆起区北西向正断层的几何学特征进行研究，采用平衡剖面演化方法，选取横穿该区北西向断层的一条剖面，定量计算正断层横向上和垂向上晚中生代以来各主要构造演化阶段的构造运动学参数，并通过构造物理模拟实验详细解析鲁西隆起区伸展变形过程。研究结果表明，北西向控凹断层在三叠纪后皆发生负反转，晚中生代鲁西隆起受到强烈拉伸，伸展构造主要发生在19—20km以下的深尺度范围内，断层切割深度加大。断裂带上普遍发育断层角砾岩、碎裂岩及断层泥。古近纪伸展作用以浅层拉伸为主，鲁西伸展量和伸展率最大，伸展作用强烈，对应北西向正断层的活动速率值也达最大值，同时发育大规模、范围广的半地堑。新近纪，伸展率很小，北西向正断层活动性大大减弱，至第四纪，断层几乎不再活动，反映鲁西隆起基本处于稳定。鲁西隆起晚中生代的伸展与华北克拉通构造变革相一致，而新生代的强烈伸展主要受控于太平洋板块与欧亚板块俯冲方向与速度的改变以及印度板块与欧亚板块的碰撞。

Extensional structures developed widely in West Shandong uplift. The characteristics of the NW-trending extensional faults in West Shandong uplift are studied based on detailed field geological survey. The tectonic kinematical parameters of each main tectonic evolution stages since late Mesozoic are calculated quantitatively using balance profile restoration along a selected profile crossing the main NW- trending taults. In addition, the process of extensional deformation is demonstrated using the structural physical modeling. The results indicate that the main NW-trending faults reversed negatively after Triassic and dominated the depositions of the adjacent depressions. In late Mesozoic, West Shangdong uplift was subjected to strong extension, and the cutting depth of the normal faults reached to 19 -20 km underground. And breccia, cataclasite and fault gouge developed in the fault belt. In the Paleogene, the crustal extension mainly occurred in shallow strata. The extension amount and extensional rate of the West Shandong uplift increased to their maximum. All of those show that the West Shandong uplift suffered intensive extension. The activity rates of the NW-trending faults reached peak. Half-graben developed massively and widely. Then, in the Neogene, extension rates becane small and faults hardly activated, indi- cating that the West Shandong uplift approximately trended to be stable. The extension of the West Shan-dong uplift since late Mesozoic coincided with the tectonic evolution of the North China Craton. The strong extension in the Cenozoic is controlled by the change of the direction and the velocity of the subduction between the Pacific Plate and the Eurasian Plate, and the collision of the Indian to the Eurasian plates.