滇西保山核桃坪铅锌多金属矿床蚀变分带特征及成因浅析

Alteration Zoning Characteristics and Genesis of the Hetaoping Pb-Zn Polymetal Deposit in Baoshan,Western Yunnan

滇西保山核桃坪铅锌多金属矿床位于冈底斯-念青唐古拉褶皱系南段福贡-镇康褶皱带之保山-永德褶皱束北端。矿体呈似层状、透镜状及囊状沿近南北向断裂带及旁侧层间破碎带产出,赋矿围岩为沿断裂带产出的矽卡岩及其附近的上寒武统核桃坪组中-厚层状大理岩化灰岩与泥质灰岩。近南北向的F1断裂及其次级断裂为主要的控矿构造,构成热液型锌、铅、银、铜、铁、金多金属矿床。根据热液脉体穿切关系、矿物组合及成因特征,将热液成矿作用分为7个矿化阶段,其中第Ⅲ、Ⅳ、Ⅴ阶段是锌的主成矿阶段。与矿化关系密切的主要蚀变类型有矽卡岩化、硅化、方解石化及黄铁矿化等。对V1矿体的蚀变填图及蚀变矿物组合、分带特征进行系统的观测,结果表明:蚀变分带模式具中心式环带结构,纵向上由浅表至深部,成矿元素具有Cu(Fe)→Cu、Zn(Fe)→Pb、Zn(Cu、Au、Ag)→Au的分带;侧向上从矿体向围岩,成矿元素具有CuZn(Fe)或CuPbZn→PbZn(Cu、Au、Ag)→Au的分带,显示成矿热液叠加复合分带性特征,并指示矿液具有从北东向南西方向迁移的趋势。综合分析后认为该矿床是多期叠加复合成矿作用的结果,与区内深部岩体有关的矽卡岩矿化为早期成矿,而后又叠加晚期中低温热液成矿作用,该矿床是一个重要的同位、多阶段成矿的典型矿床。

The Hetaoping lead-zinc deposits,located in Baoshan area,western Yunnan,is occurred within the northern part of Bashan-Yongde virgation in Fugong-Zhenkang fold belt,which is situated in the southern section of Gangdese-Nyainqentanglha fold systems.The ore body is occurred along N-S fault and interstratified fracture zone,with layer,lentoid and vesicular shapes.The ore-forming rock is skarn within fracture zone and marble limestore and argillaceous limestone in upper Cambrian Hetaoping group.The ore-controlling tectonic are N-S F1 fault and NN-W secondary faults,where develop hydro-thermal Zn,Pb,Ag,Cu,Fe and Au deposits.According the veins cutting relationships,minerals assemblages and origin characters,the hydrothermal process can be divided into seven mineralization stages,in which the third,fourth and five stages are main Zn mineralized phases.The main types of alterations closely related to mineralization are skarnization,silicification,calcilization and pyritization.The alteration mapping has been carried out,the altered minerals assemblages of V1 ore body in DK15 have been analyzed,and the zoned alteration process has been revealed.From the deep to surface,ore-forming elements have a zoning feature of Cu（Fe）→Cu,Zn（Fe）→Pb,Zn（Cu,Au,Ag）→Au;From ore body to wall-rock,ore-forming elements have a changing trend of CuZn（Fe）or CuPbZn→PbZn（Cu,Au,Ag）→Au,shoeing the superimposition and zonation characters of hydrothermal fluid.These results suggest that the hydrothermal fluid has a migrated trend from the northeast to southwest.In brief,the Hetaoping Pb-Zn deposit is a skarn-type deposit formed by the multiple superimposition of hydrothermal fluid,which has association with the skarnization of deep magma in early stage and is related to the middle-and low-temperature hydrothermal mineralization in late stage.This deposit can be served as an important example of multiple mineralized deposits.