豫西董家埝银矿床地质特征及矿床成因探讨

Geological Characteristics and Ore Genesis of Dongjianian Silver Deposit,Western Henan Province

董家埝银矿属构造蚀变岩型银矿床。银矿体赋存于F1构造蚀变带,总体产状160°∠70°;矿体沿走向延伸约650 m,沿倾向控制最大斜深约300 m;矿体最低见矿标高+630 m,最高+973 m,埋深0~282m;矿体呈脉状产出,可见分枝复合现象。银矿体Ag品位最高3 023.0×10^(-6),最低41.3×10^(-6),平均品位164.0×10^(-6),变化系数为112.6%,属较均匀型;矿体最大厚度18.23 m,最小厚度1.12 m,平均总厚度7.06 m,变化系数为101.8%,属较稳定型。成矿元素以Ag为主,伴生有用组分为Pb、Zn和Au。矿石中银的赋存形式主要有独立银矿物、晶格银矿物,且构造蚀变带中的硅化、绢云母化与银矿化关系密切。构造控矿、蚀变矿化、岩浆岩及化探异常为其主要找矿标志。初步分析认为该银矿床为中低温热液型矿床,形成于中生代,太华群和官道口群可能为其矿源层,多期岩浆活动为成矿元素的富集提供动力来源。

Dongjianian silver deposit is a structural altered rock type silver deposit. Silver body is hosted in F1 structural altered zone,ore occurrence is 160° ∠70°,the orebody extension along trend is 650 m,the maximum slant depth along trend is 300 m; the lowest elevation of found orebody is ＋ 630 m,the highest elevation is ＋ 973 m,the buried depth of silver body is 0 - 282 m; orebody occurs as veins,branching and compositing are often observed. The highest grade of silver body is 3 023. 0 × 10^-6,the lowest grade is 41. 3 × 10^-6,the average grade is 164. 0 × 10^-6,the variation coefficient is 112. 6% which shows the silver body belongs to well-distribution type. The maximum thickness of silver body is 18. 23 m,the minimum thickness is 1. 12 m,the average thickness is 7. 06 m,the variation coefficient is 101. 8% which shows the silver body belongs to stable type. Ag is the major ore-forming element,accompanying useful component includes Pb,Zn and Au. Modes of occurrence of Ag in ore includes independent silver bearing minerals and lattice silver minerals. Silicification and sericitization in structural altered zone are closely related to silver mineralization. Structural ore-control,alteration mineralization,magmatic rock and geochemical anomaly are major prospecting criteria. It is considered that the silver deposit is a medium-low temperature hydrothermal type deposit,which is formed in Mesozoic,Taihua group and Guandaokou group maybe the source bed,multistage magmatic activity provides power sources for enrichment of metallogenic elements.