胶东后夼金矿碳酸岩脉地球化学特征及其成矿意义

Geochemical Characteristics and Metallogenic Significance of Carbonic Acid Dyke Houkuang Gold Deposit of Eastern Shandong Provience

栖霞金矿集中区内的金矿床皆产于太古宙结晶基底岩系中,以石英脉型金矿为主破碎带蚀变岩型金矿次之,并富含铜、铅、锌等区别于典型的焦家式破碎带蚀变岩型和玲珑式石英脉型金矿。栖霞后夼金矿是产于前寒武纪基底变质岩系中的含菱铁矿石英脉型金矿床,前人对碳酸岩脉与金矿形成的关系探讨研究的较少,本文通过对后夼金矿区内菱铁石英脉矿石化学成分、微量元素及菱铁矿矿物属性的研究表明:后夼金矿矿脉化学成分中SiO2含量介于24.85%~85.41%之间,具有高Fe、高Mg的特征,Fe2O3 + FeO平均25.03%,MgO平均4.74%,在化学成分含量对比的百分图上反映出不同脉岩的混合特点。电子能谱分析表明化学成分中Mg具有较高的原子百分比和重量百分比,平均值分别为7.67和16.00,认为该矿物应为镁菱铁矿,具有Mg2+与Fe2+固溶体类质同象相互取代,属菱铁矿–镁菱铁矿–菱镁矿固溶体系列中的前端组合。后夼金矿具有多阶段成矿的特点,菱铁石英脉是该矿区的主要矿石类型,菱铁矿脉与石英脉呈共生关系,形成顺序为石英脉→磁铁矿脉→菱铁矿脉→含金硫化物石英脉→石英方解石脉,碳酸岩脉于石英脉具有共生关系并为金矿的富集提供了沉淀场所,Mg、Ca的菱铁矿可作为一个独特的成矿阶段。根据区域地质和脉岩资料综合分析,碳酸岩脉与石英脉应来源于不同的物质源区,碳酸岩脉来源于荆山群、粉子山群组成碳酸盐岩–钙镁硅酸岩有关,在变质或构造–岩浆热事件作用下易形成富碳酸盐岩的流体,在构造裂隙空间充填形成碳酸岩脉,而石英脉则为岩浆期后热液的最终产物,脉岩的形成是区域伸展作用的结果。

The gold deposits in Qixia gold deposit area are all located in the archean crystalline basement rock series, quartz vein type gold deposit is the main type in the fracture zone, followed by altered rock type gold deposit, and rich in copper, lead and zinc, which are different from the typical jiaojia fracture zone altered rock type and linglong quartz vein type gold deposit. Qixia Houkuang gold deposit is a quartz vein type deposit of sirite bearing in the basement metamorphic rocks of Pre-cambrian. Basis after this article through to ling in the area of stone the pulse chemical composition, trace elements and siderite ore mineral properties research showed that: vein basis after the chemical composition of SiO2 content is between 24.85% - 85.41%, has the characteristics of high Fe, Mg, Fe2O3 + FeO 25.03% on average, MgO style an average of 4.74%, in comparison of chemical composition content percentage chart reflects the different mixing characteristics of vein rocks. Electron energy spectrum analysis showed that Mg in the chemical composition had a high atomic percentage and a weight percentage, with an average of 7.67 and 16.00, respectively. The mineral was considered to be magnesium siderite, with Mg2+ and Fe2+ solid solute-like co-substitution, which was the front-end combination of siderite—magnesium siderite—magnesite solid solution series. Basis after has the characteristics of the multi-stage mineralization, ling hardness of the pulse is the main ore type of the mine area, siderite and quartz vein of arteries and veins is a symbiotic relationship, form a sequence for vein quartz vein and the magnet to the vein of siderite, gold bearing sulfide quartz vein and quartz calcite vein, dike in quartz veins have a symbiotic rela-tionship and carbonate precipitation for the enrichment of gold, Mg, Ca siderite can be used as a unique metallogenic stages. On the comprehensive analysis of the regional geology and ground data, dike carbonate and quartz vein should be derived from different material source area, carbonate vein from Jingshan, Fenzishan of calcium carbonate, magnesium silicate rock, under tec-tono-magmatic thermal metamorphism or event is easy to form rich carbonate fluid, formed in the tectonic fracture space filling dike, carbonate and quartz vein is magmatic hydrothermal end product, after the formation of vein rocks are the result of area extending action.