糜棱岩型金矿床地质特征

当糜棱岩中金元素的含量足以满足工业利用，即在糜棱岩中可圈出独立的金矿体时，这种金矿床便可称为糜棱岩型金矿床.糜棱岩型金矿床是"中国金矿床工业类型"中的重要类型之一.此类金矿床多分布在古老地块周边长期活动的构造带之中.介绍了糜棱岩型金矿床的赋矿岩系、控矿构造、矿床、矿体、矿石以及含金矿物等地质特征.同时，对金成矿地质环境及矿床成因等作了探讨

GEOLOGICAL CHARACTERISTICS OF MYLONITE TYPE OF GOLD DEPOSITS

Mylonite type of gold deposits means the ones that occur in mylonite independantly The ore bodies are gold bearing mylonite series The mobilization,migration,enrichment and deposition of Au element during the metallizing process are closely correlated to the formation and evolution stages of mylonite Gold ore bodies are strictly controlled by mylonite belts As the wall rock and ore body are both mylonite,there is no obviously boundary between them The occurrences of ore bodies are stratiform,lentiform and vein,of which the stratified ore bodies are economically significant,although the amount is relatively less Most of ore bodies occur in lens or veins,characterized by swither,composite,swell and parallel The natural type of ore is silicified sulfide bearing mylonite,which may be subdivided into quartz mylonite type,sericite quartz mylonite type,altered felsic mylonite type and altered dolomitic mylonite type The ores are in hypidiomorphic idomorphic or xenomorphic granular texture,crushed texture and poikilitic texture Disseminated and veinlet disseminated structures are dominant Network and massive structures are also common The metallic minerals are mainly pyrite and natural gold,with minor chalcopyrite,pyrhotite and galena The nonmetallic minerals are quartz,sericite,feldspar,ankerite and calcite Aurifurous minerals are mainly natureal gold,with electrum and Au telluride Natural gold occurs in quartz and pyrite as intergranular gold,fissure gold and inclusion The wall rock alterations are commonly silicification,sericitization,pyritization and carbonation,which are often superimposed,so the alteration zonation is not clear This type of deposits occur mostly in the margins of old massives,the mobile belts between massives,the taphrogeosynclines in old landmasses and the marginal belts of old island arcs Gold fields are located in deep fault belts,large compresssional faulting belts or shear zones The host rocks are commonly old gneiss,schist,granulitite and marble Gold deposits are all limited in ductile shear zones Gold bearing minerals are distributed along the foliations of mylonite The deposits are formed in mesothermal and medium pressure condition The ore forming fluids represent a reduction environment of weak acid to weak alkali The genesis of this type of deposits is closely related to ductile shearing and dynamometamorphic differentiation