大岗山坝区辉绿岩脉蚀变泥化特征及机理研究

针对大岗山水电站坝区辉绿岩脉蚀变泥化问题，在系统调研和室内试验基础上探讨了蚀变泥化带的空间分布特征、结构构造、矿物学特征及物理力学性质，并结合区域地质环境分析了蚀变泥化岩形成的主要原因。研究表明，坝区SN向辉绿岩脉劈理化强烈，蚀变泥化带发育，且主要集中发育于岩脉与花岗岩接触面及内部强烈劈理化部位。蚀变泥化岩松散易碎，具有塑性高、含水量高、重度低及中等压缩性等物性特征。X衍射和扫描电镜显示蚀变生成了大量的黏土矿物，且具有多孔隙空洞的微观结构特征。富含辉石等暗色矿物和热液交代、多期次的构造挤压错动及浅表生风化作用构成岩脉蚀变泥化的主要原因。

ARGILLIZATION AND MECHANISM CHARACTERISTICS OF ALTERED-DOLERITE IN DAGANGSHAN HYDROPOWER STATION

Dolerite argillic alteration is an important geological flaw in Dagangshan hydropower station. This paper takes advantage of geological survey and laboratory experiment, combined with regional geological environment to analyze distribution, mineralogical, structural features, physical mechanics properties and formation mechanism of the altered-rock. The study reveals that the dolerite dykes along SN direction commonly develop altered argillic band. The band mainly concentrates in contact surface of the dykes and granite or internal schistosity crack. The altered-argillic rocks are loose and crumbly and have the following physical characteristics: high water content, low specific gravity, high plasticity and medium compression. Results of X ray diffraction and scanning electron microscope show that they have a lot of chlorite and pore void microstructure characteristics. Pyroxene darkly minerals enrichment, multi-period hydrothermal metasomatism and tectonic stress action constitute the formation mechanism of the dolerite argillic alteration.