内蒙古东珺铅锌银矿床成矿机制的热力学相图研究  

The thermodynamic phase diagram and the ore-forming mechanism of the Dongjun Pb-Zn-Ag deposit

作　　者：谢伟[1] 温守钦[1] 唐铁乔 马鹏程[1] XIE Wei;WEN Shouqin;TANG Tieqiao;MA Pengcheng(Key Laboratory of Ministry of Educationon Safe Mining of Deep Metal Mines,Department,of Geology,Northeastern University,Shenyang 110819)

机构地区：[1]东北大学地质系深部金属矿山安全开采教育部重点实验室,沈阳110819

出　　处：《地质学报》2020年第5期1482-1504,共23页Acta Geologica Sinica

基　　金：国家自然科学基金项目(编号41372098)资助的成果。

摘　　要：大兴安岭广泛分布与岩浆热液作用有关的铅锌多金属矿床,对于该类型矿床中成矿物质的运移沉淀机制和矿物共生组合的研究是揭示成矿机制的关键。本文选取了大兴安岭成矿带东珺典型中高温岩浆热液型铅锌银矿床,通过对该矿床进行详细的野外地质调查和镜下矿物共生组合的研究,结合流体包裹体的显微测温研究,激光拉曼测试和H-O同位素测试,选择了方铅矿、闪锌矿和黄铁矿三种主要金属硫化物进行了热力学平衡的相关计算,依据包裹体显微测温结果选取了473K、513K、553K、593K四个温度截面绘制了热力学Eh-pH、lg[Pb2+]-pH和lg[HS-]-pH相图。结果显示随着热液成矿过程的不断演化,主要金属硫化物及其共生组合由Py(Ⅰ)→Py(Ⅱ)+Gn(Ⅰ)+Sp(Ⅰ)→Gn(Ⅰ)+Sp(Ⅰ)→Gn(Ⅰ)+Sp(Ⅱ)→Gn(Ⅱ)+Sp(Ⅱ)→Gn(Ⅱ)。流体沸腾、流体混合和水岩反应是东珺铅锌银矿床的主要成矿机制,由此引发的温度、离子活度、Eh和pH的变化对于成矿物质的运移沉淀和硫化物共生组合的形成具有重要的控制作用,东珺矿床热液成矿期主要金属硫化物及其共生组合的形成是多因素协同作用的结果。此研究对于解释大兴安岭典型热液型铅锌多金属矿床的运移沉淀机制和矿物共生组合特征具有重要的指导意义。The Great Xing’an Range hosts many hydrothermal Pb-Zn polymetallic deposits related to magmatism.A study of the characteristics of mineral paragenetic associations and the mechanisms of migration and precipitation of ore-forming elements in these types of deposits is essential for a continued study of mineral deposits.Towards this objective,a typical magmatic hydrothermal deposit in the Great Xing’an Range,the Dongjun Pb-Zn-Ag deposit,was selected.Based on the detailed field geological investigations,microscopic study of mineral assemblages,combined with the study of microthermometry and laser Raman spectroscopy of fluid inclusions,and H-O isotope data,three main metal sulfides:galena,sphalerite,and pyrite,were selected for the calculation of thermodynamic equilibrium.According to the results of microthermometry of fluid inclusions,four temperature sections(473 K,513 K,553 Kand 593 K)were selected for drawing the phase diagrams of Eh-pH,lg[Pb2+]-pH,and lg[HS-]-pH.Results show that as the evolution of hydrothermal mineralization period progresses,the main metal sulfides and their mineral assemblages are Py(Ⅰ)→Py(Ⅱ)+Gn(Ⅰ)+Sp(Ⅰ)→Gn(Ⅰ)+Sp(Ⅰ)→Gn(Ⅰ)+Sp(Ⅱ)→Gn(Ⅱ)+Sp(Ⅱ)→Gn(Ⅱ).Fluid boiling,fluid mixing and water-rock reaction are the main ore-forming mechanisms of the Dongjun Pb-Zn-Ag deposit,and the resulting changes in temperature,ion activity,Eh and pH play an important role in controlling the migration and precipitation of ore-forming materials and the formation of mineral assemblages.The formation of the main metal sulfide and their mineral assemblages during the hydrothermal mineralization of the Dongjun deposit is the result of multiple factors.This study adds to the current understanding of mechanisms of mineral migration and precipitation and mineral assemblages of typical hydrothermal Pb-Zn deposits in the Great Xing’an Range.

关 键 词：大兴安岭 东珺铅锌银矿床 流体包裹体 H-O同位素 热力学相图 

分 类 号：P618.4[天文地球—矿床学] P618.52[天文地球—地质学]