甘肃白银厂劈理构造的特征研究
来源期刊：中南大学学报(自然科学版)1988年第3期
论文作者：周翊 何绍勋 段嘉瑞
文章页码：243 - 250
关键词：劈理； 岩组学； 成因； 构造变形； 控矿构造； 显微构造； 动力变质作用/压溶作用； 定向成核择优生长； 甘肃白银厂
Key words：cleavage； petrofabric； cause of formation； structural deformation； orecontrolling structure； microtectonic； dynamic metamorphism/pressure solution； nucleation-oriented selective-growth； Gansu Baiyinchang
摘 要：白银厂是一个经历了多期变形的地区,各种小型构造现象非常丰富。对在石英角斑岩系中相当发育的S1劈理的宏观特征和显微构造的分析研究表明,在不同岩性和构造变形强度不同的岩石中,劈理的形态和发育程度呈现出有规律地变化。而且劈理的性质很复杂,任何一个简单的机制都不可能解释所有观察到的显微构造特征。因此,对这些特征的解释导致提出了一个定向成核择优生长和压溶作用的联合作用的成因模式。
Abstract: The research district is located in the Zheyaoshan-Xiaotieshan mine region of Baiyinchang,Gansu,and the rocks in this area are mainly a series of neutral-acidic volcanic rocks of middle Cambrian age which were repeatedly deformed.There are many kinds of minor structures,and the S1-cleavage is the most common one which crowded in a zone parallel to the regional structure line represented by the direction of anticlinorium axis,NW 290.The analysis of the macroscopic features of the cleavages indicates that the patterns and degree of development of the cleavages vary with the properties and deforming degree of rocks:the lower the rock intensity and the higher the deformed degree,the higher the cleavage density is.The microstructural evidenses of cleavages indicate that the properties of cleavage are very complicated and and any simple mechanism can not explain all of the observed microstructural features of the cleavages.From π1 to π2 and to π3 again,the patterns of cleavages change from continuous cleavage without“domain”structure to spaced cleavage with“domain”structure.The continuous cleavage is mainly characterized by the shape-oriented arrangement of fine mica minerals and quartz grains well-distributed in π1,and the porphyroblasts obviously have the intragranular deformation features.In π2 and π3,the cleavages comprise micaceous-rich domain and quartzrich domain,the former is called P-domain and equal to the cleavage domain,and the latter is called Q-domain and equal to microlithon.The intragranular deformation of porphyroblasts is weak,and its boundary has the typic diffusion-solution features.Therefore,on the basis of the detailed study of these characteristics of the cleavage,the authors think that the origin of cleavages in this area is due to the combined actions of nucleation-oriented selective-growth and pressure solution,and the microstructures of the rocks prove that the diffusion solution and grain-oriented growth play important roles during the formation of cleavages.
