新疆东天山土屋斑岩铜矿床流体包裹体地球化学特征

Fluid inclusion geochemistry of Tuwu porphyry copper deposit, eastern Tianshan in Xinjiang

本文在系统总结前人关于土屋矿床地质特征及成矿作用的基础上,开展了氢氧同位素研究及石英流体包裹体均一法和冷冻法测温,并对石英样品进行了气相及离子色谱测量,对石英中流体包裹体中的稀土元素进行了测试。结果表明,流体包裹体均一温度变化于125～363℃,主要集中于140～200℃,盐度变化于0.18%～58.28%NaCl,主要集中于2%～10%NaCl。流体包裹体气相的主要成分为H_2O和CO_2,液相成分以Ca^(2+)、Na^+、SO_4^(2-)、Cl^-为主。石英流体包裹体中∑REE为8.07×10^(-6)～12.15×10^(-6),轻、重稀土之比值(LREE/HREE)变化于5.39～6.75,δEu为1.80～1.91。流体包裹体中稀土元素配分型式呈右倾型,并表现出Eu的正异常及Ce的负异常。石英中流体包裹体的δD_(V-SMOW)值为～70‰～-66‰,石英的δ^(18)O_(V-SMOW)为9.4‰～12.3‰,计算所得的δ^(18)O_水为-5.1‰～-1.2‰。根据离子色谱分析结果,F^-/Cl^-介于0.009～0-024之间,SO_4^(2-)、Cl^-介于0.45～1.01之间。综合以上流体包裹体的组成和特征,表明成矿流体可能主要来源于岩浆水和大气降水。

Based on a systematical summing-up of the previous research on the geological characteristics and mineralization of Tuwu porphyry copper deposit, the authors carried out supplement measurements of hydrogen and oxygen isotopes, homogeneous and freezing temperatures analysis of fluid inclusions in quartz, gas and ion chromatographic analysis of quartz samples and analysis of REE in fluid inclusions of quartz. The results show that the homogenization temperatures of the fluid inclusions vary from 125 to 363 degrees C, and mostly range from 140 to 200 degrees C. The salinities of fluids range from 0. 18% NaCl to 58. 28% NaCl and mostly range from 2% NaCl to 10% NaCl. The gas components of fluid inclusions are mainly H(2)O and CO(2), and the liquid components of fluid inclusions are mainly Ca(2+), Na(+), SO(4)(2-), Cl(-). The Sigma REE of fluid inclusions range from 8.07 x 10(-6) to 12.15 X 10-6, the LREE/HREE ratios vary from 5.39 to 6.75, and delta Eu ranging from 1.80 to 1.91. The ore fluid in the fluid inclusions display right-inclines chondrite-normalized REE distribution patterns and positive Eu and negative Cc anomaly. The delta D(V-SMOW), of the inclusions in quartz range from similar to 70 parts per thousand to -66 parts per thousand, and the delta(18)O(V-SMOW) values of quartz range from 9.4 parts per thousand to 12.3 parts per thousand. According to the calculated results the delta(18)O(H2O) range from -5.1 parts per thousand to of 1.2 parts per thousand. The results of ion chromatographic analysis showing that the ratio of F(-)/Cl(-) range from 0. 009 to 0. 024, and that 4 Cl(-) range from 0. 45 to 1.01. It is suggested that the ore-forming fluid was mainly derived from mixture fluid of meteoric water with magma water.