甘肃文县阳山金矿带显微构造研究

甘肃文县阳山金矿位于西秦岭南亚带,地处中国扬子大陆—华北大陆—松潘甘孜地块三大地块(华北—扬子—松潘)的汇聚转化部位,大地构造背景极为复杂。本次工作着力研究该区显微构造特征,通过显微构造来反映宏观构造。主要研究内容与成果包括:①通过对显微构造特征观察,认为该区构造应变主要为脆—韧性变化,区域构造运动至少可以分为4个期次,与宏观构造所反映的构造期次基本一致;②显微构造运动学分析表明,该区断裂带活动方式有变化,从而造成了剪切方向的不一致;③动力学分析表明,该区域主应力方向为NW—NE,与宏观构造所反映的区域主应力方向一致;动态重结晶法计算古应力差值为20MPa左右,反映为后期剪切作用的差异应力,其构造层次也相对较浅,属于表—浅构造层次。

STUDY ON MICROSTRUCTURES IN THE YANGSHAN GOLD ORE BELT, WEN COUNTY, GANSU

The Yangshan gold ore deposit, Wen County, Gansu lies in the south sub-zone of west Qinling, in the convergence-transformation place of three major massifs of Yangtze, North China and Songpan Ganzi, where tectonic background is very complicated. All major studies in the area have focused on the origin, features and ore-control models of gold deposits. It was the first time to perform systematic micro-scale research in the area, and this work centered on study of microstructures in the area, by which to reflect macrostructures. Major research contents and results include： 1）observation of microstructure features suggested substantial brittle- ductile change in the area; 2） microstructure dynamics indicated change in the mode of fracturing activity in the area, thus causing unconformity in shearing direction; 3）dynamic analysis implied primary stress in the direction of NW-NE, in line with that of regional primary stress reflected in macrostructures; dynamic recrystallization method gave calculated difference of 20MPa for ancient stress, possibly a reflection of late differential stress of shearing, and of relatively shallow structural level; 4）view ofmicrostructures supported at least four tectonic phases in the area, basically as they are shown in macrostructures.