南秦岭东河地区金矿床特征及成因分析

Characteristic and Genesis of the Au Deposits in Donghe Region,Southern Qinling

南秦岭东河金矿位于南秦岭西段,属南秦岭成矿带西成金铅锌多金属成矿带的东延部分,为陕甘川金成矿三角地带。区内出露地层为中上志留统舟曲岩组、志留系—泥盆系大河店组,其中,中上志留统舟曲岩组上岩段(S2+3z3)是金矿化产出的主要层位;区内断裂构造十分发育,主要表现为平行分布的近东西的层间挤压破碎带,为区内主要的控矿构造;区内构造破碎带内及旁侧发育的石英脉与金矿化关系密切。工作区内共圈定金矿体8条,矿体均近东西走向,其中主要矿体Au-8长度390m,平均厚度2.54m,Au平均品位为2.41×10-6。东河地区金矿床主要受断裂构造的控制;其次岩性、岩浆岩对金矿的形成也起一定的作用。通过对本区成矿地质背景、矿床地质特征、控矿因素等方面的研究,认为研究区金矿床为沉积-叠加改造型中-低温热液金矿床。

The Donghe gold deposit, served as a part of the eastern extension of southern Qinling Au- Pb - Zn deposit belt, is located in the west segment of southern Qinling. The mainly exposed strata in this area are Middle-Upper Silurian Zhouquyan Formation （S2＋3） and Silurian-Devonian Dahedian For- mation （S- D）, meanwhile, the upper section of Zhouqu Formation （S2＋3 z3） serves as the main layer for gold mineralization in this region. The fault structures are fully developed, which are regional major ore- controlling structures, showing as an EW-trending interformational fracture zone with nearly parallel dis- tribution. Within the regional tectonic fracture zones and its two sides, the quartz veins have close rela- tionship with gold mineralization. Totally, 8 gold ore-bodies have been delineated there, all of them are distributed as nearly E- W trending. In which, the Au - 8 is the major ore body with the length and thickness are 390 and 2.54 meters, respectively, meanwhile, its average gold grade is 2.41× 10^-6. The Donghe gold deposits are mainly controlled by faults. Besides, lithology and magmatic rocks are also pla- ying a certain role in the enrichment and formations of gold deposit. After analyzing regional geological background, geological characteristics of mineral deposit and ore-controlling factors, the Donghe gold de- posit is classified as sedimentary reformed and superimposed exothermal-epithermal deposit.