钠长岩类地质地球化学特征及变质变形与铜矿的形成——以四川会理拉拉铜矿床为例

Geology-geochemistry, metamorphism and deformatiom of albitites and their bearings on copper mineralization: an example from the Lala copper deposit in Huili, Sichuan

关键词:  拉拉铜矿  钠长岩  变质变形  碎裂-糜棱构造  充填交代

Key words:  Lala copper deposit  albitite  metamorphism and deformation  cataclasticmylonitic structure  filling and replacement

摘要:

本文论述了拉拉铜矿区钠长岩类的地质地球化学特征及变质变形与铜矿的形成。伴随前寒纪的构造运动,拉拉地区经历了NWW向的剪切变形,使钠长岩产生碎裂-糜棱岩化作用,形成碎裂结构、碎斑结构,显微眼球构造、压力影、云母鱼等。这些结构构造的形成使岩石孔隙度增加,起到扩容作用。由沿近东西向主断裂侵位的辉绿辉长岩体提供的含矿流体及区域变质中产生的变质热液沿钠长岩的碎裂-糜棱构造充填交代,在其产生多种蚀变的同时,铜、钼、钴硫化物沉淀成矿,形成钠长岩型浸染状铜矿石或脉状-网脉状铜矿石。在金云母化较强地段,在变质作用下,形成片岩型铜矿石。因而总体上,拉拉铜矿属动力变质热液型铜矿床。

Abstract:

The detailed studies have been conducted on the geology-geochemistry,metamorphism and deformation of albitites and their bearings on the mineralization of the Lala copper deposit in Huili,Sichuan.The NWW-trending (nearly E-W-trending) shear deformation caused by the Precambrian tectonic movements in the Lala district is believed to be responsible for the generation of cataclasis and mylonitization of the albitites in this area,and for the formation of such textures and structures as cataclastic texture,mortar structure,micro-augen structure,pressure shadow and fish-shaped mica,which brought about the increase in porosity.The ore-bearing fluids from the diabase and gabbro masses emplaced along the nearly E-W-trending major fault and metamorphic hydrothermal solutions originated from regional metamorphism infilled and replaced the fissures and pore spaces within the cataclastic-mylonitic structures.The subsequent alterations resulted in the precipitation and mineralization of copper,molybdenum and cobalt sulfides,and in the formation of the albitite-type impregnated or vein-netvein copper ores.In the places where the phlogopitazation occurred,the schist-type copper ores were formed by metamorphism.It follows that the Lala copper depoist is of dynamic metamorphic-hydrothermal origin.