福建大田琴山铁矿成矿物理化学条件研究

PHYSICAL-CHEMICAL CONDITIONS FOR MINERALIZATION OF THE QINSHAN IRON DEPOSIT IN DATIAN COUNTY,FUJIAN PROVINCE

在野外地质工作基础上,通过流体包裹体和氢氧同位素研究,探讨福建大田琴山铁矿床形成的物理化学条件。流体包裹体研究显示,均一温度均值355.6℃,盐度（Na Cl质量分数）均值4.4%,流体密度均值0.65 g/cm3。流体演化成矿经历了400~420℃和240~280℃两个主要阶段,其中400~420℃为晚矽卡岩阶段磁铁矿主要成矿温度,形成深度约3 km,该阶段以混合作用为主;240~280℃为晚硫化物阶段铅锌矿主要成矿温度,形成深度约1 km,以沸腾作用为主。激光拉曼测试结果显示,成矿流体含少量CH4和CO2。氢氧同位素显示,早期成矿流体主要以岩浆水为主,晚期成矿流体混入大量大气降水。研究结果表明琴山铁矿属于热液矽卡岩型矿床。

Based on field investigation,the forming physical and chemical conditions of Qinshan iron deposit in Datian,Fujian were researched by fluid inclusions measurement and hydrogen and oxygen isotope. The homogenization temperature of fluid inclusions was 355. 6 ℃,the salinity was4. 4% Na Cl and the density was 0. 65 g / cm3. Two peaks of homogenization temperature indicated that there were two stage of ore-fluid in the process of mineralization. The earlier stage was close related with the magnetite metallogenisis on the later skarn stage and the depth of about 3 km,the homogenization temperature was 400 ~ 420 ℃. The later stage was the Pb-Zn metallogenic stage and the depth of about 1 km,the fluid temperature was 240 ~ 280 ℃ and boiling. Raman analysis showed that the ore forming fluids contained little CO2 and CH4. The hydrogen and oxygen isotope data showed that the ore forming fluid mostly was derived from magma,and mixed with lot of meteoric water at later stage. Overall,the Qinshan Iron deposit was interpreted as a hydrothermal skarn deposit.