软性地带与硬性地块

由于各地质构造单元结晶基底软硬程度不同，反映在布格重力异常图和磁力异常图上的差异明显。硬性地块布格重力异常图反映为区域性开阔平缓的重力高区，磁力异常图也是宽缓的磁力高或磁场平静区；软性地带布格重力异常图反映为等异常线距较紧密，具明显走向的重力低带，磁力异常图呈磁场变化区或磁场剧烈变化区。导致上述现象的原因在于硬性地块多为古隆起-新拗陷，而软性地带基底较软，在水平力挤压下容易发生横向压缩、纵向增长，形成剧烈褶皱带。

Soft region and hard block.

Because of different softness and hardness in crystalline basement of different structural units,the difference reflected on Bouguer gravimetric anomaly map and magnetic anomaly map is significant.The Bouguer map for hard block is characterized by regionally open and flat gravitational high and its magnetic map is characteristic of wide and flat magnetic high or normal magnetic response;gravitational low having clear trend and close isoanomalic contour is characteristic of Bouguer map of soft region and magnetic field of this region on magnetic map is characteristic of changed or significantly changed area.The reasons resulted in abovementioned phenomena lie in that most of the hard blocks were old uplift-new depression,the basement of soft region was softer,which is easy to produce lateral compression and vertical increase under the action of horizontal extrusion,forming severe fold belt.