甘肃阳山金矿带构造变形特征研究

Study on the characteristics of structural deformation in Yangshan gold deposit belt,Gansu province

阳山金矿带内构造变形复杂强烈,对构造变形特征的系统研究表明:阳山金矿带内发育有A型线理、石香肠、旋转碎斑等构造,这些构造大部分都表现出由北向南的韧-脆性剪切特征;对褶皱轴面产状的统计表明其主应力方向为近南北向;利用石英颗粒动态重结晶法得到古应力值为45.55 MPa。结合蠕变方程得到变形平均应变速率为3.6×10-10s-1;根据矿物显微变形特征认为变形形成温度为280～400℃,应发生于地壳深度不超过12 km的范围内;依据斜长花岗斑岩形成时间及地层变形特征,认为剪切变形形成于晚三叠世—早白垩世;结合阳山金矿成矿特点,认为该剪切对本区金的活化、迁移富集以及最终金矿体的最终定位,有着极其重要的控制作用。

Structural deformation in Yangshan gold deposit belt is .very strong and complicated. This paper has studied the structural deformation characteristics of the deposit belt in detail. The main conclusions are listed as fol- lows： there are some important structures, such as A-type lineation, boudinages, rotated porphyroclast, which indi- cate the ductile-brittle shear characteristics from N to S ; the axial planes of folds show that the orientation of principal stress is near NS. By the measurement of the dynamically recrystallized quartz grain, the paleo-stress is calculated as 45.55 MPa. In terms of the creep equation, the average strain velocity is obtained as 3.6 x lO-l^s-1. According to the features of the deformed minerals, it is determined that the ductile-brittle shear formed at the temperature from 280 ~C to 400 ~C and its depth of formation was no more than 12 km beneath the ground. According to the formation time of plagiogranite porphyry and deformation characteristics of strata, the ductile-brittle shear formed between the Upper Triassic and the Lower Cretaceous. Based on the ore forming features of Yangshan gold deposit, it is believed that the shear is significant for the gold element activation, enrichment and final orientation.