论秦岭造山带及其立交桥式构造的流变学与动力学

Rheology and dynamics of Qinling orogenic belt and its grade-separation-style structure

当前受国内外地学界广泛关注的秦岭印支造山带,其前身是地球自转速度缓慢变化过程中派生的纬向剪切力和重力共同作用下,于惯性力最大的上地壳所产生的受东西向走滑正断层控制的盆-山系,而不是洋壳俯冲形成的沟-弧-盆系;其造山机制是南秦岭断陷盆地上地壳底部刚硬的结晶基底,对北秦岭断隆山软弱的中地壳塑性层俯冲所造成的壳内冲叠造山带,而不是整个岩石圈对软流层俯冲导生的板块碰撞造山带;其动力是212 Ma前发生于加拿大安大略省直径100 km撞击坑的陨击事件,促使地球自转速度急剧变慢所派生的由南向北的强烈挤压作用,而不是地幔对流带动板块漂移碰撞;其超高压变质带是壳内俯冲动力作用所致,而不是陆壳俯冲到100 km以深温压环境的产物;其立交桥式构造,是异常地幔响应了地壳上部新产生的不同方向的中-新生代断陷盆地引起的重力失衡作用的结果,而不是地幔柱主动隆升造成与原来东西向造山带的非耦合关系.

The preexistence of Qinling Indosinian Orogenic Belt which widly attracts domestic and oversea geologicians attentions is a basin-mountain system which formed on the upper crust with most powerful inertial force and is controlled by the E-W strike-slip normal faults and by the process of gravity and latitudinal shear stress derived from gradual variation of the Earth＇s rotation rate. It is not a channel-arc-basin system formed by subduction. Its orogenic mechanism is that the rigid upper crust＇s bottom crystalline basement of southern Qinling downcast basin has been subducted under the weak middle crust＇s plastic layer of northern Qinling rift rising mountain, so it is a intracrust thrust superimposed orogens and not a plate collisional orogenic belt derived from the lithosphere subducting into the asthenosphere, its power was the meteorite impact which had formed a 100km diameter impact crater before 212 Ma in Ontario, Canadian. It is not mantle convection that drives plates drifting and colliding, but the strong horizontal compression from south to north derived from the Earth＇s rotation rate sharply slowing down caused by the meteorite impact. Its ultrahigh-pressure metamorphic belt was caused by intracrust subduction dynamical effect and not by continent crust subducting in 100 kin-deep-temperature-pressure condition. Its grade-separation-style structure was the result which the anomaly Earth＇s mantle responsed to the gravity unbalancing caused by new different orientation meso-cenozoic block basins on the upside crust, and not the non-coupling relation between the mantle plume active uplifting and primary W-E orogenic belt.