摘要
控制矿脉的断裂原为雷德尔剪断裂组成的共轭系.因应力场的改变,有利一组再活动和成矿而不利于另一组.据共轭剪裂角及脉石英中二氧化碳包体的研究推断,成矿深度大约一公里.
The gold bearing quartz veins occur in Archean alkali - granitic complex of granulite facies. The fractures controling the veins can be divided into two groups. The first group strikes NNE and dips to WNW at 38° - 50° and the second ENE with dip - angles of 50° - 70° to NNW. The veins of the first group are arranged en echelon of left stepping and the latter shows right stepping. The individual veins are usually at inclination of ca 10° to thedirection of vein arrays. They are, therefore, considered here as conjugate sets and consist of Riedel shear fractures. This implicates that they developed initially under condition that the acute angle between the shear fractures was bisected by the maximum principal stress axis σ_1 and that the field suffered about NE-SW compression. The sense of movement with displacments of 1-2 m along the fracture surface of the first group, however, is left lateral judged from the some markers. The fact apparently is uncompatible with the above inference. There are many offsets of veinlets, which strike NNW, on the both sides of main veins and in the bridge areas. They are mainly responsible for the gold in the area and redgarded as a result of reativation of fractures. There is no evidence to show appreciable removement along the fracture surface of the second group. The reason for this probably is the change of the stress state. Since the σ_1 switched to the Northwest, the ratio of normal and shear stresses on the fracture surface is favorable for the first group to slip and not for the second.The fractures devoloped at very shallow levels (about 1 km) reckoned by the tensile strength of rocks, the angle between conjugate sets and the study of CO_2 enclosures in the quartz.
出处
《地质找矿论丛》
CAS
CSCD
1990年第2期20-28,共9页
Contributions to Geology and Mineral Resources Research
