山东牟平宋家沟金矿床地质特征及成因研究

发布时间：2018-11-27 08:49

【摘要】：宋家沟金矿床位于山东省烟台市牟平区,地处华北与扬子两大板块的碰撞构造带,沂沭断裂带以东,胶莱盆地东北缘与胶北隆起的构造结合部位,是牟平—乳山成矿带内受密集裂隙带控制的大型金矿床。中生代晚期,胶东地区动力学环境由NW-SE向的挤压转变为NW-SE向的伸展体制,胶东东部地区进入重要的成矿期。区域出露地层主要为前寒武纪地层、中生代地层及新生代第四纪地层。区内岩浆岩较发育,主要为中生代鹊山弱片麻状细中粒含石榴二长花岗岩及闪长玢岩、闪长岩和煌斑岩等脉岩。对矿区内煌斑岩进行锆石U-Pb定年分析,确定成岩年龄为164.2+4.9Ma。区内构造发育,宋家沟金矿床矿体受张性陡倾断裂和密集裂隙带联合控制,张性断裂及密集裂隙带为区内主要的容矿和控矿构造。目前矿区内共圈定了35个工业矿体。矿体形态主要呈不规则脉状,整体走向为北东向,倾向南东,倾角为倾角多为75°-87°,局部较缓为35°-50°,矿体规模较小。矿石内金属矿物主要有银金矿、自然金和黄铁矿,其次为少量黄铜矿、闪锌矿、方铅矿和磁铁矿等；矿石结构以自形-半自形粒状结构、碎裂结构和填隙结构为主；矿石构造以致密块状、团块状、脉状、浸染状和角砾状构造为主。围岩蚀变类型主要有黄铁绢英岩化、硅化、钾化和碳酸盐化等,其中黄铁绢英岩化和硅化与金矿化关系密切。宋家沟金矿的热液成矿期可划分为四个成矿阶段：石英—黄铁矿阶段(Ⅰ)、石英—绢云母—黄铁矿阶段(Ⅱ)、金—石英—多金属硫化物阶段(Ⅲ)和碳酸岩阶段(Ⅳ),其中第Ⅱ与第Ⅲ阶段为主成矿阶段。流体包裹体研究表明,宋家沟金矿床成矿流体为CO2-H2O-NaCl体系；成矿流体具有低盐度(5.0～12.0wt%NaCleqv)、低密度(0.64～0.96g/cm3)的特点。成矿温度集中在200～2400C之间,成矿压力区间为40～62MPa,成矿深度为5.01～6.34km。氢、氧同位素测试结果表明,成矿流体来自幔源初生水,并有后期大气降水的加入；硫同位素研究表明,硫主要来自地幔,并与荆山群有一定的继承性；铅同位素研究结果表现出深源特征。综上所述,确定宋家沟金矿床成因类型为幔源流体参与成矿的中温热液脉型金矿床。宋家沟金矿床矿体受早白垩纪莱阳群内发育的张性陡倾断裂和密集裂隙带联合控制；工业矿体有明显的分段富集现象,主要富集在断裂走向偏NE的位置,而在走向偏NEE的位置矿化明显减弱；倾向上矿体主要富集在倾角由缓变陡的位置；控矿断裂构造在成矿期显示左旋正断的性质。矿体侧伏规律不明显,局部有向北东侧伏的趋势,侧伏角为30°～50°。认为胶莱盆地东北缘剥蚀程度从西向东逐渐减小,宋家沟金矿区为剥蚀程度最小的矿区；在综合分析矿化富集规律和该区剥蚀保存条件的基础上,认为宋家沟金矿区深部及外围具有一定的找矿潜力。
[Abstract]:The Songjiagou gold deposit is located in Muping District, Yantai City, Shandong Province. It is located in the collision tectonic belt of North China and Yangtze plates, east of Yishu fault zone, and the structural combination site between northeast margin of Jiaolai Basin and Jiaobei uplift. It is a large gold deposit controlled by dense fracture zone in Muping-Rushan metallogenic belt. In the late Mesozoic, the dynamic environment in Jiaodong area changed from NW-SE to compression to NW-SE extensional system, and the eastern Jiaodong area entered an important metallogenic period. The regional outcrop strata are mainly Precambrian, Mesozoic and Cenozoic Quaternary strata. The magmatic rocks in the area are relatively developed, mainly composed of granitic granites, diorite porphyrite, diorite and lamprophyre, etc. Zircon U-Pb dating analysis of lamprophyres in the mining area shows that the diagenetic age is 164.2. 9 Ma. The orebody of the Songjiagou gold deposit is controlled by tensional steep-dip faults and dense fissures, and the tensional faults and dense fissures are the main ore-holding and ore-controlling structures in the area. At present, 35 industrial orebodies have been delineated in the mining area. The shape of the orebody is mainly irregular vein, the whole strike is north-east, the inclination angle is 75 掳-87 掳, the local degree is 35 掳-50 掳, and the scale of orebody is small. The ore is mainly composed of silver gold, natural gold and pyrite, followed by a small amount of chalcopyrite, sphalerite, galena and magnetite, etc. The ore structures are compact, massive, veined, disseminated and breccia. The main alteration types of surrounding rock are yellow sericite, silicification, kalitization and carbonization, among which the yellowtigitization and silicification are closely related to gold mineralization. The hydrothermal metallogenic stage of Songjiagou gold deposit can be divided into four metallogenic stages: quartz pyrite stage (鈪，

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