滇东北银厂铅锌矿床成矿流体特征与意义

Characteristics of Ore-forming Fluids in the Yinchang Pb-Zn Deposit in NE Yunnan,China

通过对银厂铅锌矿开展野外勘查和进行室内C—O—S同位素及包裹体测温等工作,测得包裹体均一温度为175~275℃;成矿期硫化矿硫同位素δ34S值在8.4‰~17.24‰,重晶石在26.8‰~29.3‰;成矿期方解石δ13C变化范围在-3.6‰^-2‰,δ18O为17‰~18.6‰,围岩δ13C为-3.6‰^-0.7‰,δ18O为19.1‰~23.1‰。成矿物质与古老基底或碳酸盐围岩等有关,成矿流体主要来自地层水。当矿源层降于地下还原带时,激发了成矿元素的活性,在中、偏碱性的还原环境下溶解成络合离子而迁移,随着成矿流体温度的逐渐下降便在有利的岩性空间、构造条件下聚集沉淀。矿体的控矿空间主要为临近矿源层的各类逆断层附近的次级断裂或层间破碎带等,黄铁矿化、重晶石化是主要的蚀变矿物,地表铁帽是原矿风化产物。

The C-O-S isotope and fluid inclusion temperature measurement of the Yinchang Ag-Pb- Zn deposit indicate the uniform temperature of the fluid inclusions was about 175-275℃C. The sulfur isotope range of sulfide ore in the metallogenic stage was 8.4 ‰-17.24‰. The barite was between 26.8‰-29.3‰. The δ^13C of the calcite in the metallogenic stages was between -3.6‰--2‰, δ^18O is 17‰-18.6‰, the δ^13C the surrounding rock of is -3.6‰--0.7‰, and δ^18O is 19.1‰-23.1‰. It is considered that the ore-forming fluid was mainly derived from the formation water of the ancient basement or the surrounding rock. When the ore source layer with the evolution of the earth＇s crustwas located exactly at the reduction zone, the activity of ore-forming elements was stimulated. The metal elements which was dispersed in the surrounding rock in reductive environment of alkaline dissolved into complex ion and began to move, when the external physical and chemical conditions change or the primitive fluid encounters the partial acidic atmospheric water, the sulfide deposits of industrial value were formed under the favorable lithologic spatial and structural conditions. The ore controlling space of the ore body was mainly the secondary fault or the interlayer fracture zone near the source layer. Pyritization, baritization were the main alteration minerals, the gossan was weathering products of ore surface.