藏南沙拉岗锑矿流体包裹体红外显微测温研究

Infrared fluid inclusion microthemometry on stibnite from Shalagang antimony ore in southern Tibet,China

沙拉岗锑矿是藏南金锑成矿带内最具有代表性的锑矿床。为了更直接地了解该矿床的流体物理化学特征,本文利用红外显微镜对辉锑矿及紧密共生石英中的流体包裹体进行了显微测温研究。红外显微测温分析结果表明,辉锑矿中包裹体均一温度在134.9～221.9℃,峰值在160～190℃之间,盐度在1.7%～7.3%NaCleqv,峰值在5.0%～6.0%NaCleqv之间,密度在0.879～0.958g/cm3之间,平均值为0.934g/cm3;共生石英中包裹体均一温度在142.5～205.6℃,峰值在160～190℃之间,盐度在2.3%～7.0%NaCleqv,峰值在4.0%～6.0%NaCleqv之间,密度在0.910～0.947g/cm3之间,平均值为0.929g/cm3。通过对比研究认为沙拉岗辉锑矿及共生石英形成于同一物理化学条件,捕获同一成矿流体。结合石英中单个流体包裹体激光拉曼成分分析认为成矿流体为含微量CO2、N2、CH4气体的低温、低盐度和低密度的NaCl-H2O热液体系。成矿流体的沸腾作用是辉锑矿大量沉淀主要原因。

The Shalagang antimony deposit is the most representative antimony deposit of gold-antimony ore-forming belt in southern Tibet,China. A microthermometric study using infrared microscopy was performed on fluid inclusions hosted in stibnite and symbiotic quartz,in order to directly characterize physicochemical conditions of ore-forming fluid from Shalagang antimony deposit. Results of infrared microthermometric measurement show that fluid inclusions hosted in stibnite have homogenitation temperatures values of 134. 9 ～ 221. 9℃,with a peak of 160 ～ 190℃,salinity values of 1. 65% ～ 7. 25% NaCleqv,with a peak of 5. 0% ～ 6. 0% NaCleqv,and density values of 0. 879 ～ 0. 958g / cm3,with an average of 0. 934g/cm3; fluid inclusions hosted in symbiotic quartz have homogenitation temperatures values of 142. 5 ～ 205. 6℃,with a peak of 160 ～ 190℃,salinity values of 2. 31% ～ 6. 96% NaCleqv, with a peak of 4. 0% ～ 6. 0% NaCleqv,and density values of 0. 910 ～ 0. 947g / cm3,with an average of 0. 929g/cm3. Comparative study indicates that stibnite and symbiotic quartz from Shalagang antimony deposit formed in the same physicochemical conditions and capture the same ore-forming fluids. With Laser Raman analysis of fluid inclusions hosted in symbiotic quartz,it shows that the oreforming fluids of the Shalagang antimony deposit is a NaCl-H 2 O fluid system which is characterized by low homogenization temperature, low salinity,low density and trace CO 2,N 2 and H 4 gases. The boiling of ore-forming fluid is the dominant factor for stibnite deposition.