辽宁省盖县猫岭金矿床地质特征及成因探讨

猫岭金矿床赋存于早元古代辽河群盖县组变质岩系内,空间上与印支期猫岭似斑状花岗岩体关系密切,两者相距仅0.2km,花岗岩体本身有金矿化及蚀变现象。矿床的成矿热液为一种氧逸度较低、富集碱金属及卤族(特别是Cl)元素的热液,其δD=-77——80‰,δ18O=6.05-7.38‰,δ34S=6.15-10.3‰。矿床的矿石铅与猫岭花岗岩体长石铅的同位素组成不尽一致。根据上述特征可认为:猫岭金矿床为与中生代花岗岩有关的、典型的岩浆热液型金矿床,但金属成矿物质除成矿热浪本身带来外,部分还由成矿热液萃取自容矿围岩-辽河群盖县组。

GEOLOGICAL CHARACTERISTIC AND GENESIS OF MAOLING GOLD DEPOSIT SN LIAONING PROVINCE

Maoling gold deposit occuring in aarly Proterozoic metamorphic rocks is near Maoling granite body, which is Mesozolc in age (K- Ar age: 207.8Ma). The distance that the gold deposit is apart from granite body is only 0.2km. and but Maoling granite itself is altered and mineralized. The host rocks of Maoling gold deposit are sericite phyllite and quartz sericite phyllite. The si-lification and sericitization are the chief alteration of the host rock. The or-ebodies consist of the gold- bearing quartz veinlets and the phyllite which was silicified and sericitized. The ore boundary is defined by chemical analysis.The whole process of the mineralization of Maoling gold depos is divided into four stages. The first astages is the overall silicification stage, in which the early quartz, sericite, scattered arsenopyrite, pyrrhotite and a small amount of seheelite and anatase are formed. Second one is the gold- quartz- arsenopyrite- multimetal sulphide stage, in which the curved gold-multimetal sulphide quartz veinlets are formed. the third one is quartz pyrrhotite stage, in which the straight pyrrhotite quartz veinlets. The fourth one is carbonate stage.The chemical analysis of primary fluid inclusion show that, there chiefly are Cl-, Na+, K+, CO as well as CO2 and CH4 in ore-forming fluid of the second stage, and there chiefly are Cl-, Na+, CO as well as CO2 and CH4 in ore-forming fluid of the third stage. On these grounds, we think that the ore-forming fluids of the second stage and the third stage in Maoling gold deposit are all the fluid which contains alkali metal and halogen, and which is situated in lower fO2 condition.The compositions of hydrogen isotope and oxygen isotope of oreformingfluid for Maoling gold deposit are:σD=-77--80‰,σ18OH2o=6.05 - 7.38%.on the σ5D vs. σ18O diagram, they are all plotted on the magmatic water field, indicating the ore-forming fluid belong to the typical magmatic hydro-thermal fluid. The compositions of sulphur isotope of Maoling gold deposit are σ34S=6.15 - 10.3‰, which is very similar to that one of magmatic hydro-thermal deposit. Ore lead isotope compositions of the various ore-forming stages are basically the same and but they are diferent from feldspar lead isotope compositions of Maoling granite, which indicate the ore-forming metals of the various ore-forming stages come from the same source, and a part of the ore-forming metals are extracted from the host rocks by the ore - forming hydrothermal fluid.From above date we think that the Maoling gold deposit belongs to magmatic hydrothermal gold deposit.