广西龙头山金矿载金黄铁矿地球化学特征

摘要

The Longtoushan gold deposit, located in southern Qinhang metallogenic belt, is one of the important deposits in the Dayaoshan region, different stages of pyrite were found in the deposit. According to the characteristics of occurrence, pyrites are divided into 5 types, corresponding to 5 stages: tourmaline-quartz-sulfide stage (Ⅰ), quartz-pyrite-chalcopyrite stage (Ⅱ), quartz-polymetallic sulfide stage (Ⅲ), quartz-pyrite-sphalerite stage (Ⅳ) and quartz-pyrite stage (Ⅴ). REE and trace element analysis data of pyrites show that the ore-forming fluid of gold mineralization is mainly magmatic hydrothermal with medium-high temperature and reducing, and the fluid is characterized by rich Cl? and poor F?. Au mainly is migrated by the way (AuCl2)? complexes.δ34SCDT values of pyrites range from +1.29×10?3 to +2.01×10?3, showing that ore-forming materials is derived from deep magma. Values ofμand Th/U are 9.63?9.84 and3.87?4.00, respectively. The narrow range of Th/U shows the characteristics of stable lead isotope. Based on the above analysis, ore-forming materials are from deep magma caused by basement crust remelting and the ore-forming fluid is mainly post-magmatic hydrothermal.%龙头山金矿是钦杭成矿带南段大瑶山地区重要的金矿床之一,矿区发育大量不同阶段的黄铁矿,根据其产出特征和先后关系划分为5个世代,对应着5个成矿阶段:电气石?石英?硫化物阶段(Ⅰ)、石英?黄铁矿?黄铜矿阶段(Ⅱ)、石英?多金属硫化物阶段(Ⅲ)、石英?黄铁矿?闪锌矿阶段(Ⅳ)和石英?黄铁矿阶段(Ⅴ).黄铁矿单矿物的稀土、微量元素分析结果表明:与金成矿有关的成矿流体主要为中高温岩浆热液,具有还原性,且流体富Cl?贫F?,Au主要以(AuCl2)?络合物形式迁移.黄铁矿δ34SCDT值介于+1.29×10?3~+2.01×10?3,表明成矿物质来源于深部岩浆;铅同位素μ值为9.63~9.84,Th/U值为3.87~4.00,变化范围窄,为稳定性铅同位素.综合分析认为:矿区成矿物质主要来源于基底地壳重熔形成的深部岩浆岩,其中岩浆期后热液为主要成矿热液.