陕西凤县马蹄沟—庙沟金矿区控矿构造特征

陕西凤县马蹄沟—庙沟金矿处于华北板块与华南板块之间的唐藏—商丹构造混杂带内。矿区赋矿地层下古生界罗汉寺岩群为一套浅变质、强变形的火山—沉积岩系，经历了多期构造变形、变质作用，使得矿体形态变得更加复杂。采用矿区构造剖面与岩（矿）石切片研究方法，通过野外实地调研及构造分级分类专题研究，对区内多种类型的控矿构造样式及性质等进行了详细研究，结合岩石光薄片观察、岩石化学分析、探矿工程深部揭露和区域构造演化历史分析等方法，划分出四级控矿构造。研究表明：区内存在成矿期前剥离断层，主体控矿构造为近EW向展布的罗汉寺—瓦窑上脆—韧性断层（F9）及其NWW向派生韧—脆性剪切带和断裂破碎带；主控矿构造方向为近EW向和NWW向；矿体向北缓倾，在空间上呈复式褶皱或褶叠层样式，局部受北倾直立片理化带控制，产状较陡；与金矿体关系密切的岩脉为晚三叠世花岗斑岩脉。金成矿主体经受晚印支期脆—韧性剪切变形期热液蚀变富集，并在脆性阶段叠加有剪切带引张破裂及含金石英细脉加富。该矿床成矿类型为晚三叠世脆—韧性剪切带叠加引张破裂热液型金矿。

Characteristics of Ore-Controlling Rules of Matigou-Miaogou Gold Deposit in Fengxian County，Shaanxi Province

Matigou-Miaogou gold deposit in Fengxian County，Shaanxi Province is located in the Tangzang-Shangdan tectonic mixed zone of the Qinling orogenic belt.Because of the multi-stage orogenic ductile and brittle tectonic activities，there are many types of superimposed composite shear zones，and deep granite magmatic intrusion during collisional orogeny，which make it an important favorable zone for gold mineralization.The Lower Paleozoic Luohansi Group is a set of shallowly metamorphic and strongly deformed volcanic-sedimentary rocks in the ore-hosting strata of the mining area.It has undergone multi-stage tectonic deformation and metamorphism.Folds and faults are well developed，which make the ore body morphology complex and can be roughly divided into north-south tectonic belts.The shape of folds is complex and varied，and the overall shape of folds is reversed S-shaped，while the fracture is a series of brittle-brittle toughness with multiple primary and secondary matching.This paper uses the research methods of structural section and slice of rock and ore in the mining area，based on the field geological facts，through the special study on hierarchical classification of the mining area structure，detailed research on various types of ore-controlling structure styles and features in the area.Combined with the methods of rock slices，petrochemical analysis and deep exploration of prospecting engineering，the history of regional tectonic evolution，divided different levels of ore-controlling structures，a four-level ore-control structure was divided.Structural profiles show that tight folds and other ductile shear deformation and dynamic metamorphism such as mylonite zone and schistosomiasis zone are developed in the mining area.Rock （ore） slices show that mylonite foliation displacement early regional foliation （phyllite，etc.） is widespread in the mining area，which can reach above the level of primary mylonite，and is multi-stage brittle and ductile superimposition transformation.Gold mineralization is related to ore type and fabric.Gold grade of alterated mylonite （10.2×10^-6~17.5×10^-6，weathered：4.97×10^-6~6.23×10^-6），especially superimposed quartz vein type，is higher than altered cataclastic rock （1.16×10^-6），rock mass and boundary contact zone with the lowest grade （0.18×10^-6~0.89×10^-6），and is mineralized.The study concluded that there is a stripping fault before the metallogenic period.Matigou-Miaogou gold deposit is a fourth-order tectonic ore-controlling zone and a first-order Tangzang-Shangdan tectonic melange zone，which controls the distribution of metallogenic belts and ore-forming geological bodies in the area，i.e.the north-south tectonic slices and Jingshaowan back-shaped.The second-order is a nearly east-west-trending Luohansi-Wayaoshang brittle-ductile fracture（F9），which retains the characteristics of multi-stage compression brittle-ductile structure from north to south，and the section develops tectonic slices，it controls the spatial location of mineralized alteration zone.The third level is F9 which controls the NWW-NW secondary derivative brittle-ductile shear zone，which is nearly parallel to it，and controls the spatial form of ore bodies.The fourth level is the position where the occurrence of shear zone changes and the extensional fracture zone，which controls the occurrence change of orebodies and the changes of ore grade and type，such as thickening and quartz vein type superimposition and enrichment.The main ore-controlling structure extends in the direction of nearly east-west and northwest-west.The orebody dips northward gently and steeply locally，and is controlled by the vertical schistosomiasis zone of northward dip.The space may be in the form of multiple folds or fold stacks.The main gold metallogenic bodies in this area formed hydrothermal alteration and enrichment in the process of brittle-ductile shear deformation in the late Indosinian period，superimposed by enrichment of gold-bearing quartz veins in the extensional fracture zone of shear zone.The metallogenic type is Late Triassic brittle-ductile shear zone superimposed extension fracture hydrothermal gold deposit.