华北地区莱州湾沿海金矿区现今构造应力状态及构造作用

Present-day state of tectonic stress and tectonization in coastal gold mine area near Laizhou Gulf,North China

为了研究华北地区莱州湾附近沿海金矿区的现今构造应力状态和构造作用,采用应力解除法、滞弹性应变恢复法和水压致裂法开展地应力测量工作,共测定49组地应力数据。结果表明,水平构造应力在现今应力场中占主导地位,是一种典型的构造应力场。应力场的特征为σ_(H)>σ_(v)>σ_(h)(σ_(H)、σ_(h)和σ_(v)分别为最大水平主应力、最小水平主应力和垂直主应力)和σ_(H)>σ_(v)>σ_(h),这分别有利于逆冲和走滑断裂活动。应力水平相对较高,不利于地下结构的稳定性。σH的方向为WNW–ESE或近E-W向,这与震源机制解和区域地质构造分析的结果一致。现今应力场是不同地质时期动力作用和构造运动的结果,研究区的应力场总体上继承了第三期(喜马拉雅运动期)构造应力场的特征,同时部分保留了第二期(燕山期)构造应力场的特征,最终演化为以近E-W向挤压为特征的构造应力场。

To investigate the present-day state of tectonic stress and tectonization in a coastal gold mine area near the Laizhou Gulf,North China,overcoring,anelastic strain recovery,and hydraulic fracturing stress measurement campaigns were performed,and a total of 49 groups of stress data were determined.The results indicate that horizontal tectonic stress plays a predominant role in the present-day stress field,which is a typical tectonic stress field.The stress fields are characterized by σ_(H)>σ_(v)>σ_(h)(σ_(H),σ_(h) and σ_(v) are the maximum horizontal,minimum horizontal and vertical principal stresses,respectively)and σ_(H)>σ_(v)>σ_(h),which appear to favor thrust and strike-slip faulting,respectively.The stress level is relatively high and is not conducive to the stability of underground excavations.σH is oriented in the WNW−ESE or approximately E−W directions,which is in accord with that indicated by focal mechanism solutions and regional geological structure analysis.The contemporary stress field is the result of dynamic action and tectonic movement in various geological periods;the contemporary stress field generally inherited the characteristics of the third stage tectonic stress field(Himalayan movement period)while partially retaining the characteristics of the second stage tectonic stress field(Yanshanian period),and finally evolved into the tectonic stress field characterized by nearly E−W extrusion.