脉体充填的力学机制

我们把脉体充填的断裂构造的发生发展过程分为三个阶段:生成阶段、发展阶段和破坏阶段。第一阶段主要地是在水平的挤压应力作用下发生的,一般在(水)平面上形成两组剪性断裂和一组横向张性断裂,而在横剖面上则出现两组纵向压性断裂,有时还见一组张裂。这种立体空间形变特点反映在平面上构成“米”字型。此外,还有其他一些断裂。

DYNAMICAL MECHANISM OF THE VEIN FILLING

The process of generation and development of fractures filled with veins are divided by the author into three stages; i.e. stage of generation, stage of opening and filling, and stage of destruction of the veins. These stages take place in different times with different mechanisms. The first stage appears mainly to be the action of horizontal compressional stress and characterized by the deformation in three-dimensional space. The second stage appears after the formation of fractures under the action of tectonic extension.Some examples are cited in the paper to decipher firstly the intrusion of veins and part of small bodies along fractures (or fracture zones), which fill usually in the multi-direction systems of fractures, with the sharp boundaries. The syn-directional veins have relatively large accumulated thickness, and exhibit the features of a series of de-rivated structures. An analysis of various characteristics of veins is made, including the dominant occurrence of endogenic ore vein deposits aipipearred mostly in uplifted area, the complexity and variety of vein forms, filling of same kind of veins within fractures in some different directions, parallel arrangement of different kinds of ore veins in same fracture, symmetric strip, comb and miarolitic structures in same vein, and a series of internal textures and structures. According to the results of petrofabric studies, the author clarifies the coincidence of the primary orientation minerals with the direction of tectonic extension in the stage of vein filling.The comprehensive analysis shows that the vein filling take place under the tectonic extension of the fractures. Thus, the stage of generation turn into the stage of filling in an extengional environment, which has resulted from the ununiform uplift of metallogenic region, including the stress of fold upward bending and the topping of intrusion. This uplifting led the upper-levelling blocks to be in lateral extension, and the fracture to be opening and then to become the conduits for the uprising and filling of magma and ore-bearing fluids. Finally a mechanical analysis and preliminary modelling experiment are given for the stress state in the stage of extension and fillling.