西秦岭地区大桥金矿床硅化角砾岩的特征及成因  

Characteristics and Genesis of the Silicified Breccias in the Daqiao Gold Deposit,West Qinling Orogen

作　　者：张忠平[1] 吴亚飞[2] 李建威[2,3] Zhang Zhongping;Wu Yafei;Li Jianwei(Geological Survey of Gansu Province, Lanzhou 730000, China;a. Faculty of Earth Resources;2b. State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences（Wuhan）, Wuhan 430074, China)

机构地区：[1]甘肃省地质调查院,兰州730000 [2]中国地质大学(武汉)资源学院,武汉430074 [3]中国地质大学(武汉)地质过程与矿产资源国家重点实验室,武汉430074

出　　处：《地质科技情报》2018年第2期79-88,共10页Geological Science and Technology Information

基　　金：中国地质调查局项目(1212011120570);国家自然科学基金项目(41325007)

摘　　要：大桥金矿床是西秦岭地区近年来新发现的一种金矿床类型。矿体赋存在三叠系与石炭系不整合面附近和三叠系内层间滑脱构造中,与硅化角砾岩的关系非常密切,矿化及角砾岩化自不整合面或层间滑脱构造向两侧围岩逐渐减弱。硅化角砾岩体由不同的角砾岩层构成,其产状总体轻微切层,沿走向延伸稳定;角砾主要为遭受不同程度硅化的板岩、灰岩和方解石等,杂基为原地的粉砂屑和断层泥,胶结物为细脉浸染状含金硫化物、微晶石英、玉髓和方解石等。野外观察和岩相学研究表明,大桥金矿区的硅化角砾岩是在早期构造角砾岩遭受强烈硅化的基础上进一步经过多期液压致裂作用形成的,多期次的硅化、液压致裂及自愈合作用导致角砾岩中大量含金硫化物的卸载沉淀。对西秦岭造山带的区域构造分析表明,在与碰撞造山逆冲推覆及随后的板内演化相关的区域变质变形过程中,大规模深部变质热液在压力和热梯度的驱使下沿区域深大断裂上升,多次脉冲式进入地层不整合面及层间滑脱构造中导致岩石发生强烈硅化,进而发生液压致裂作用而形成复杂的含金角砾岩。The Daqiao gold deposit is a new type gold deposit in the west Qinling orogen discovered recent years. The orebodies are mainly hosted in the unconformity interfaces of the Triassic and Carboniferous and the decollement structures in the Triassic turbidites, strictly controlled by the silicified breccias, and the mineralization and brecciation weaken from the structural interfaces to both sides of the wall rocks. The silicified breccia bodies consist of different breccia layers, slightly cutting through the strata and ex- tending along the strike stably. The breccias are mainly slate, limestone and calcite with various degrees of silicification, and matrix is composed of silt crumbs and fault gouge. The cement consists of veinlet-dis- seminated auriferous sulfides, microcrystalline quartz, chalcedony and calcite. The Daqiao silicified brecci as are therefore considered to be the hydraulic breccias resulted from the early tectonic breccias, and the multi-stage silicifications, hydraulic brecciations and self-healings led to the massive gold deposition. Dur- ing the intensive thrust napping and metamorphism after final collision in the Late Triassic in the west Qiniing, the multi-stage deep-seated metamorphic fluids driven by pressure and heat gradients moved up- wards along regional deep faults and then migrated into the high preamble unconformity interfaces and the decollement structures, forming the complex auriferous breccias.

关 键 词：构造角砾岩 液压致裂 金矿化 大桥 西秦岭 

分 类 号：P618.51[天文地球—矿床学]