鄂尔多斯块体新生代构造活动和动力学的讨论

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鄂尔多斯块体除西南边界为挤压边界外, 四周被共轭剪切拉张带所围限,东西和南北两侧分别为右旋和左旋剪切拉张带, 全新世水平和垂直滑动速率分别达5m m /a 和03~3m m /a。鄂尔多斯块体自始新世起从西南挤压边界两端开始发育,逐渐向远端发展, 至上新世最后形成山西断陷盆地带。新生代以来块体不断缓慢上升, 距今 140 Ma 以来的隆起总量为 160m 。形变测量说明块体现代隆升速率为 1~28m m /a, 周缘断陷盆地带现代下降速率为- 4~- 5m m /a。块体内部莫霍面变化平缓, 埋深40km ~42km , 上地幔高导层埋深123km ~131km , 它们在周缘断陷盆地带相对隆起, 前者隆起幅度 15km ~6km , 后者埋深仅70km ~100km 。6 级以上地震均发生在块体周边活动构造带内, 块体内部无6 级以上地震发生, 4~5 级地震也很少。震源机制、地应力和断层滑动矢量测量等得到的主压应力方位为 N E N E E向,与控制块体周边活动构造的区域应力场一致,主要与青藏块体的 N E向挤压作用相关,盆地地下深部物质上涌产生的垂直力也起着重要作用。所以, 区域性水平应力场和深部物质运动产生的垂直力联合作用是本区新构造活动 Except that the southwestern boundary is the extrusion boundary, the Ordos block is surrounded by the conjugate shear tension bands around the east and west and north-south extents, respectively. The horizontal and vertical slip rates of Holocene Up to 5m m / a and 03 ~ 3m m / a. Ordos blocks started to develop from both ends of the southwest extrusion boundary since the Eocene and gradually developed to the distal direction. Finally, the Ordos block formed the Shanxi rift basin zone during the Pliocene. Since the Cenozoic, the mass has been increasing slowly, up to 160 m since 140 Ma. The deformation measurements show that the modern uplift rate of block is 1 ~ 28m m / a, and that of the peripheral rift basin is -4 ~ -5m m / a. The Moho inside the block changes gently, with a buried depth of 40km ~ 42km and a buried depth of 123km ~ 131km in the upper mantle. They are relatively uplifted in the peripheral rift basin with the former uplifted by 1.5km ~ 6km and the latter buried only 70km ~ 100km. Earthquakes of magnitude 6 and above occurred within the active tectonic belts around the block. No earthquakes of magnitude 6 or above occurred in the block, and earthquakes of magnitude 4 to 5 were rare. The principal compressive stress azimuth obtained from focal mechanism, in-situ stress and fault slip vector measurements is N E N E E, which is consistent with the regional stress field around the active structure of the control block and mainly compresses with the N E direction of the Qinghai-Tibet block The vertical forces generated by upwelling of deep underground material in the basin also play an important role. Therefore, the combined effect of regional horizontal stress field and vertical force generated by deep material movement is the new tectonic activity in this area
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