滇东北矿集区昭通铅锌矿区蚀变岩分带及元素迁移特征

Alteration Zoning and Geochemical Element Migration in Alteration Rock of Zhaotong Lead-Zinc Deposit in Northeastern Yunnan Mineralization Concentration Area

围岩蚀变是昭通铅锌矿床的重要找矿标志。通过对矿区760中段98勘探线剖面实测、蚀变岩分带研究、岩石地球化学迁移特征与参数计算,指出围岩蚀变与成矿的关系:热液蚀变分带明显,在蚀变中心,黄铁矿化最强,方解石化、白云石化次之,硅化较弱,黄铁矿化与矿化关系密切;远离矿体,黄铁矿化逐渐减弱,而方解石化、白云石化逐渐增强。强黄铁矿化和强黄铁矿化-强方解石化-强硅化粗晶白云岩蚀变组合是重要的找矿标志。从细晶白云岩带到强黄铁矿化带,元素整体呈迁入形式,主要为与Zn-Pb成矿作用有关的元素,如Ge、Ag、Cd等迁入;同时伴随成矿流体作用,亲铁元素及铁明显富集,显示不同蚀变岩相受热液改造作用影响。蚀变指数(I_A)的大小,与矿化强弱呈正相关关系,I_A大,则矿化强。

Wall-rock alteration is one of the important ore-prospecting clues in the Zhaotong lead-zinc deposit. Based on the studies of the alteration zoning and element migration in altered rock of the No. 98 profileline in the 760 m level of this deposit, we discussed the relationship between the alteration and the mineralization. There develops obvious hydrothermal alteration zonation,from the center of the ore body to outside,alteration gradually weakened. In the altered center,the pyritization is most intensive,followed by dolomitization and calcitization,and silicification is the weakest,and the pyritization is closely related to mineralization. Far away from the ore body,pyritization weakened gradually,calcitization and dolomitization increased gradually. The intensive pyritization and the intensive pyritization-calcitization-silicification coarsegrained dolomite alteration are important prospecting clues. From fine-grained dolomite zone to the intensive pyritization zone,such elements as Ge,Ag and Cd,which have a close relationship to Zn-Pb of ore-forming,migrate in as a whole. Meanwile,both iron and Pro iron elements markedly enriched accompanying by the oreforming fluids elements,which indicates that different alteration facies were reformed by the hydrothermal fluids.The index of alteration（ I_A） has the positive correlation with the alteration intensity.