吉林延边棉田金铜矿床成矿流体特征及矿床成因

Characteristics of ore-forming fluids and ore genesis of Miantian gold-copper deposit in Yanbian of Jilin Province

棉田金铜矿床是受断裂构造和中性侵入体联合控制的以金、铜为主的多金属矿床。笔者在对该区地质调查的基础上,运用红外光谱分析和显微测温技术对成矿流体进行研究,发现该区围岩蚀变以绢云母化和青磐岩化最为普遍,并将成矿阶段分为4个阶段:黄铁绢英岩阶段、石英--黄铁矿阶段、多金属硫化物阶段和石英--碳酸盐阶段;对应的均一温度为320℃～360℃、280℃～320℃、200℃～280℃和200℃～240℃;其中主成矿阶段为第二、三阶段,主成矿温度为200℃～320℃,这也是热液中水和二氧化碳含量最高的阶段。流体盐度为1.91～13.40(wt%,NaCl),密度为0.69～0.95g/cm3,具低盐度和低密度的特点;成矿深度为0.8～1.5 km,具浅层成矿的特点;氢氧同位素分析,δ18OH2O的值为-4.7×10-3～5.83×10-3,δDH2O的值为-89×10-3～-124×10-3,说明成矿流体主要为岩浆水,含少量大气水。综合研究表明,棉田金铜矿床属于浅成中温岩浆热液型矿床。

Miantian gold-copper deposit is a gold-copper-based multi-metal deposit controlled by faults and neutral intrusions. On the basis of geological survey, we studied the ore-forming fluids by infrared spectroscopy and micro themometry. The results showed that the wall rock alteration was dominated by sericitization and propylitiza- tion, and the mineralization consisted of four stages, including the beresite stage, quartz-pyrite stage, polymetallic sulfides stage and quartz-carbonate stage. Correspondingly the homogenization temperatures were 320℃ -360℃, 280℃ -320℃, 200℃ - 280℃ and 200℃ -240℃, in which the second and third were the main mineralization stages, corresponding h omogenization temperatures from 200℃ to 320℃ ）. At the same time there were the highest contents of H20 and CO2 in the main mineralization stages. Salinity of fluid varied between 1.91% and 13.40% （wt%, Nacl） and density was 0.69 -0. 95 g/cm3, with obvious characteristics of low salinity and density. The main ore-forming depth was from 0. 8 km to 1.5 kin, which indicated the epizonal characteristics. Based on the compositional analytical results of fluid inclusions, the values of δ^18OH2O and δDH2O were -4.7 × 10^-3 -5.83 × 10^-3 and -89 × 10^-3 -124 ×10^ -3, which illustrated that the ore-forming fluids mainly originated from magmatic hydrothermal along with a small amount of atmospheric water. Miantian gold-copper deposit belonged to medium temperature epizonal magmatic-hydrothermal deposit.