五台山绿岩带主要金矿类型及构造控矿规律探讨

A tentative discussion on structural ore-controlling regularity and main types of gold deposits in Wutai Mountain greenstone belt

依据构造控矿为成矿主因、矿源层是物质基础,将五台山绿岩带金矿划分为3种主要类型:与次级褶皱有关的条带状铁建造型金矿床、与剪切变形有关的变质中酸性火山沉积岩型金矿床、与剪切变形有关的变质砾岩型金矿床。这些不同类型的金矿床构造控矿特征明显。五台山绿岩带的区域性倒转复式向斜构造制约了含矿带呈NEE向展布,大型紧闭褶皱转折端控制了矿床的定位,与紧闭褶皱伴生的剪切变形及次级褶皱控制着矿体的规模、形态和产状,剪切裂隙控制着金矿脉的分布和金矿化的局部富集。紧闭褶皱倒转翼部(近转折端)的剪切变形是五台山绿岩带金矿构造控矿的普遍规律。矿源层是物质基础,而经历了紧闭褶皱及伴生的剪切变形带叠加改造的矿源层才是最佳的成矿和找矿靶区。文章以构造控矿理论为指导,重点剖析了典型矿床的构造控矿特征,深入探讨了控矿构造对矿床定位、规模大小、矿体形态、富集程度的制约,认为褶皱与剪切变形不仅在于控矿,而且其本身就是一种重要的成矿作用,进而总结了五台山绿岩带金矿构造控矿的普遍规律。

Based on the hypothesis that structural ore-control is the major ore-forming factor and the ore source bed constitutes the foundation of ore-forming materials, the author has divided the gold deposits in the Wutai Mountain greenstone belt into three main types,namely banded iron formation（BIF） related to secondary folds,metamorphic intermediate-acid volcanic-sedimentary type related to shear deformation,and metamorphic conglomerate type related to shear deformation.Gold deposits of these types are obviously controlled by structures.The regional overturned compound syncline of the Wutai Mountain controls the ore-forming belt of the NEE-trending regional distribution pattern,the large tight fold hinge belt controls the positions of gold deposits,the shear deformation associated with tight folds and secondary folds control sizes,shapes and attitudes of ore bodies,and the shearing fissures control the distribution and local enrichment of gold veins.Shear deformation on the overturned limb（near the hinge zone） of the tight fold constitutes the structural ore-controlling regularity for gold deposits of the Wutai Mountain greenstone belt.The ore source bed is the foundation of ore-forming materials,and ore-bearing strata reformed by superimposed tight fold and shear deformation are the best target areas for metallogenesis and ore prospecting.Based on the structural ore-controlling theory,this paper has made an emphatic analysis of the ore-controlling structural features of typical ore deposits,probed deeply into the effects of ore-control structures on the positions,sizes,shapes and enrichment of gold deposits,and pointed out that folds and shear deformations not only are ore-control structures but also serve as main mineralization themselves.The structural ore-controlling regularity of gold deposits in the Wutai Mountain greenstone belt is also summed up.