黔西北青山铅锌矿床主要控矿断裂构造岩-岩相分带模式

Model of tectonite-lithofacies zoning in ore-controlling faults of the Qingshan lead-zinc deposit in northwestern Guizhou

青山铅锌矿床是黔西北矿集区内威宁-水城成矿亚带的典型矿床之一,矿体产出严格受构造和岩性双重因素控制。含矿断裂带中构造岩既是构造变形作用的载体,也是相应变形环境的受体,其具有显著的分带特征。针对斜落走滑构造环境下弱蚀变构造岩与热液成矿成生联系研究的薄弱环节,基于构造岩-岩相学填图方法以及不同岩相带内节理、裂隙构造解析,系统采集不同构造岩-岩相带内定向构造岩样品,进行显微构造与地球化学分析,剖析不同岩相带内构造岩类型、物质组成、内部结构、构造及其分带特征,构建了该矿床构造岩-岩相分带模式,即从矿体向外,依次为:张裂岩相带→泥化相带(一、三中段及以上)→扭裂岩相带→压裂岩相带。扭裂岩相带内发育黄铁矿化、铅锌矿化、方解石化、弱白云石化,压裂岩相带内主要发育方解石化,矿化蚀变随着远离矿体呈现出从强变弱的变化规律,成矿环境也随着温度逐渐降低,呈现氧化→弱氧化-弱还原→还原的变化特征。同时,结合宏观和显微构造应力场分析,认为矿体外侧不同类型的构造岩是在统一构造应力场作用下,因不同位置的局部应力场变化而形成的不同类型的构造岩,发育在北西向断裂下盘的次级断裂不仅控制了矿体定位和形态产状,也控制了其外侧构造岩-岩相带。

The Qingshan lead-zinc deposit is one of the typical deposits in the Weining-Shuicheng metallogenic subzone in the northwestern Guizhou ore concentration area,and orebodies are strictly controlled by both tectonic and lithologic factors.The tectonites in the ore-bearing fault zone with remarkable zoning characteristics are not only the hosts of deformation processes but also the responses for the environment of structure deformation.This paper focuses on the weak links in the study of the genetic connection between weakly altered tectonites and hydrothermal metallogenesis in the oblique strike-slip tectonic condition.Based on the tectonite-lithofacies zoning mapping method,we analyzed joints and fracture structures in different lithofacies belts,and systematically collected directional tectonite samples for microstructural and geochemical analysis.The tectonite type,material composition,internal texture and structure,and zoning characteristics were analyzed,and the zoning model of tectonitelithofacies in this deposit was constructed.That is,outward from the orebody,the zoning sequence is as follows:the tensile initial cataclasite zone→the sludging zone(Level 1,3 and above)→the torsional initial cataclasite zone→the compressive initial cataclasite zone.Pyritization,lead-zinc mineralization,calcitization and weak dolomitization occur in the torsional initial cataclasite zone,and calcitization occur in the compressive initial cataclasite zone.Mineralization-alteration changes from strong to weak as it moves away from the ore body,and the mineralization environment gradually decreases with the temperature,showing a tendency of oxidation→weak oxidation→weak reduction→reduction.Combined with the stress field analysis of macroscopic and microscopic structure,it is believed that different types of tectonites outside orebodies were caused by the changes in the partial stress field at different locations of the uniform tectonic stress field,and the secondary faults in the footwall of NW trending faults not only controlled the location and morphology of orebodies but also controlled the outward tectonitelithofacies zone.