淋湘金矿地球化学特征

陕西旬阳淋湘金矿床产于南秦岭古生界泥盆系地层中，容矿围岩主要为碳酸盐岩和细碎屑岩，金矿体主要受近东西向断裂控制．第Ⅱ、第Ⅲ矿化阶段为金的主要矿化阶段，第Ⅱ～Ⅲ阶段石英包体中N2含量大于21μg/g，而第Ⅳ阶段矿物中的N2含量均小于1μg/g，说明成矿流体中的N2含量减少对金矿化不利；成矿流体的氢氧同位素组成与变质水相当；矿石的硫同位素早期为18.21‰，中晚期为17.83‰～14.01‰；铅具有正常铅同位素特征；不同矿化程度的矿石的稀土元素组成的球粒陨石标准化分配曲线，呈富轻稀土的右倾型，曲线形态基本一致，随着矿化增强其稀土元素含量明显增高．这些矿床地球化学特征表明，成矿金属元素和硫主要来源于造山带围岩地层，属容矿岩石为沉积岩中的浅层渗滤同生热盐水型金矿床，成矿时代为燕山期．

The geochemical characteristics of the Linxiang gold deposit

The Linxiang gold deposit is found in the Paleozoic Devonian strata. The gold ore-bodies occur in carbonate, fine-sandy phyllite and phyllite, and the major ore-bearings are confined to the EW ore-control fault. Pyrite, limonite, pyrrhotite, chalcopyrite and quartz are all the major carrier minerals of gold. Mineralization in the Linxiang gold deposit displays two episodes-endogenetic and exogenetic episodes. The endogenetic episode comprises four stages of mineralization., and the second and the third ore-forming stages are major mineralization stages. Ore-forming fluids are in CO2, N2, Ca2+, Na+, K+, Cl and F-. Lower nitrogen content of the ore-forming fluid is disadvantageous to the mineralization. Ore-forming fluids are of low salinity. In the main mineralizing stage,average salinity is 5% (mass fraction) NaCl equiv., density 0.855 g/cm3, pH 4.26～5.40, Eh -0.548 0～-0.393 4 eV, f(S) 1.6×10-20～5.51×10-18 Pa ,and f(O2) 3.89×10-44～5.75×10-40 Pa.The fluids in the inclusions have a wide range of homogenization and exploding temperatures from 136 ℃ to 320 ℃, but the best temperature range for gold deposition is from 210 ℃ to 250 ℃. Geochemical study on the ores and altered rocks shows that large quantities of silicon, CO2, LREE are brought into the metallogenic system during mineralization and alteration. The stable isotope, REE and ore-forming fluid characteristics suggest that the metallogenic substance comes mainly from orogenic belt strata, and the deposit is a shallow-seated, medium-low temperature, leaching, syngentic gold deposit which was formed in sedimentary in the Yanshan epoch.