内蒙古三河铅锌矿床的矿化特征及构造控矿规律

Mineralization styles and structure-controlled mineralization rules of the Sanhe Pb-Zn Deposit in Inner Mongolia

以内蒙三河铅锌矿床为研究对象,通过详细的野外和井下地质调研、勘查资料综合分析、构造地质测量、矿石和蚀变岩的岩石学和矿物学研究等,对矿区主要的构造类型、产状特征、脉体和蚀变的类型及矿化与断裂构造的关系进行了详细的研究。研究结果表明,矿区矿体主要呈脉状-网脉状产于北西西向断裂构造中。根据矿区断裂-脉体类型-蚀变的关系可以看出,走向北西西、倾向南南西的断裂为矿区主要的控矿断裂,主控矿断裂产状平直或呈舒缓波状,其间常发育铁锰碳酸盐-石英-硫化物脉,脉侧蚀变以硅化、黄铁矿化和绿泥石化为主。矿区主要矿体呈北西西走向,倾向南南西,其在走向和倾向上延伸规模大、产状稳定,地表常表现为蚀变片理化带,但其中常可见张性角砾岩脉或晶洞构造,其应为早期剪性断裂再次活化的产物。北北西和北北东向断裂为成矿后断裂,其间常被正长斑岩脉、闪斜煌斑岩脉充填,或发育方解石±石英±萤石±黏土矿物脉,可切穿含矿构造和含矿碳酸盐脉;成矿后断裂产状变化较大,分枝分叉和侧列现象常见,且其中常发育不规则状方解石-萤石脉及晶洞构造,显示了张性断裂的特征;同时对矿体有一定的错断,但断距不大,对找矿影响较小。无矿方解石-萤石-黏土矿脉两侧蚀变以黏土矿化为主,并发育少量浸染状黄铁矿化。铁锰碳酸盐脉两侧发育绿泥石化、硅化、黄铁矿化为矿区重要的找矿标志。这一认识对指导矿区及邻区同类矿床的找矿具有重要意义。

The Sanhe Pb-Zn deposit is studied in this paper through detailed field and underground geological investigations,structural geological surveys,drilling profile analysis combined with petrological and mineralogical analysis of ores and altered wall-rocks.We then discussed the ore-controlling structures and their distribution patterns,the styles of mineralization and alteration,the coupling relation between the mineralization and fault structures.Our results show that the mineralization in the Sanhe deposit show structure-controlled characteristics,and with dominant ore bodies trending NWW,dipping SSW.The extent of the ore-controlling faults can reach hundreds of meters to a few kilometers long,with relative stable occurrence.In the field,the ore-controlling faults occur as altered foliated zones but with tensional breccia veins and druse texture in them,showing a reactivated shear fault signature.NWW-and NNE-trending faults show post-ore deformation characteristics and usually with lamprophyre,syenite porphyry or calcite±quartz±fluorite±clay mineral veins occuring in them.The NNW-and NNE-trending faults and related veins crosscut the mineralized carbonate-quartz veins and NWW-trending faults indicating a post-ore brittle deformation and hydrothermal activity.The post-ore faults and related hydrothermal veins usually occur as branching,bifurcation or irregular shapes and with druse texture in the center of the veins implying a extensional faults.Although the post-ore faults can slightly dislocate the ore bodies and contemporaneous hydrothermal veins,the displacement is negligible for exploration.The alteration around the non-mineralized calcite veins is dominated by clay alteration together with minor disseminated pyrite.Combined the structure-controlled mineralization and the alteration related Pb-Zn minerlization,it is concluded that the NWW-tending faults with silicification,pyritization,chloritization alteration halo,can be used as significant prospecting criteria in the deposit and the neighbouring area.