Infrared microthermometry of fluid inclusion in sphalerite:A case study of the Xinqiao deposit in the Middle-Lower Yangtze metallogenic belt  

闪锌矿中流体包裹体的红外显微测温:以长江中下游成矿带新桥矿床为例

作　　者：Yangyang Wang Yilin Xiao 王洋洋;肖益林(中国科学技术大学地球和空间科学学院岩石圈演化与环境演变全国重点实验室,安徽合肥230026;中国科学院比较行星学卓越创新中心,安徽合肥230026)

机构地区：[1]State Key Laboratory of Lithospheric and Environmental Coevolution,School of Earth and Space Sciences,University of Science of Technology of China,Hefei 230026,China [2]CAS Center for Excellence in Comparative Planetology,Hefei 230026,China

出　　处：《中国科学技术大学学报》2024年第5期10-21,I0006,共13页JUSTC

基　　金：supported by the National Key R&D Program of China(2018YFA0702701);the Fundamental Research Funds for the Central Universities(WK3410000015).

摘　　要：Infrared microthermometry allows direct measurement of fluid inclusions hosted in opaque ore minerals and can provide direct constraints on the evolution of ore-forming fluids.This study presents infrared microthermometry of spherite-hosted fluid inclusions from the Xinqiao deposit in the Middle-Lower Yangtze Metallogenic Belt and sheds new light on the ore genesis of the deposit.Considering that infrared light may lead to non-negligible temperature deviations during microthermometry,some tests were first conducted to ensure the accuracy of the microthermometric measurements.The measurement results indicated that using the lowest light intensity of the microscope and inserting an optical filter were effective in minimizing the possible temperature deviations of infrared microthermometry.All sphalerite-hosted fluid inclusions from the Xinqiao deposit were aqueous.They show homogenization temperature ranging from~200 to 350℃,but have two separate salinity groups(1.0 wt%-10 wt%and 15.1 wt%-19.2 wt%NaCl equivalent).The low-salinity group represents sedimentary exhalative(SEDEX)-associated fluids,whereas the high-salinity group results from modification by later magmatic hydrothermal fluids.Combined with published fluid inclusion data,the four-stage fluid evolution of the Xinqiao deposit was depicted.Furthermore,our data suggest that the Xinqiao deposit was formed by twostage metallogenic events including SEDEX and magmatic-hydrothermal mineralization.红外显微测温可以对不透明矿石矿物中的流体包裹体进行测试,从而直接剖析相关矿床成矿流体的演化。本文选取了位于长江中下游成矿带的新桥矿床,对闪锌矿中的流体包裹体进行了红外显微测温,并对该矿床的成因提供新的解释。由于在显微测温过程中红外光的照射会导致测温结果呈现明显的偏移,为保证测试结果的准确性,本文首先进行了一系列的条件实验,实验结果表明显微镜可调的最低光强度以及滤光片的使用可以使测温过程中的温度偏移降到最低。在新桥矿床中,闪锌矿中的流体包裹体全为水溶液包裹体,显微测温获得的均一温度在200–350℃之间,但这些包裹体的盐度(NaCl等效盐度)可以分为两组,第一组盐度为1.0 wt%–10 wt%,第二组稍高,为15.1 wt%–19.2 wt%。低盐度的这些包裹体代表了海底喷流沉积相关的成矿流体,而高盐度的包裹体则与晚阶段的岩浆-热液流体密切相关。结合该地区已有的流体包裹体数据,新桥矿床的成矿流体演化可以归纳为4个阶段。更为重要的是,本文的数据显示新桥矿床存在两期次的成矿事件,包括早期的海底喷流沉积成矿以及晚期的岩浆-热液成矿。

关 键 词：infrared microthermometry fluid inclusion SPHALERITE Xinqiao deposit 

分 类 号：P618.43[天文地球—矿床学]