闪锌矿流体包裹体显微红外测温及其矿床成因意义以云南会泽超大型富锗银铅锌矿床为例

摘要

Infrared micro-thermometry technique is efficient to study fluid inclusions in opaque-translucent minerals by connecting the infrared microscopy with cooling-heating table.The sphalerite-hosted fluid inclusions in Huize super-large Zn Pb (Ag Ge)deposit have been studied by this technique.There are six types of sphalerite-hosted fluid inclusions,including pure gaseous inclusions (V), pure liquid inclusions (L), gas-aqueous inclusions with aqueous-rich (L + V), gas-aqueous inclusions with rich gas(L+V),three-phase inclusions containing a daughter(L+V+S),and LCO2 +LH2 O +VCO2 three-phase inclusions.Two types of gas-aqueous fluid inclusions with rich liquid and pure liquid(L)can be only seen in calcite.The homogenous temperature of sphalerite-hosted fluid inclusions ranges from 100 to 364 ℃,in which two distinct temperature sectors are 150 221 ℃ and 320 364 ℃, with the average capture temperature 232 ℃.The salinity of sphalerite-hosted fluid inclusions has three distinct sectors of 1.1% 5.0%,5.0% 11.0%,and 12.0% 18.0%.The homogenous temperatures of sphalerite-hosted fluid inclusions of different mineralization stages reflect the evolution of the ore-forming fluids in the whole process;while the calcite-hosted fluid inclusions indicate the middle and late mineralization stages of the ore-forming fluids.Comparing with the paragenetic gangue mineral,the homogenous temperatures of fluid inclusions in sphalerite are higher,which indicates that sphalerite-hosed fluid inclusions carry more information of ore-forming fluids.From early to late mineralization stages,ore-forming fluids might have experienced the evolution of medium-high temperature and medium salinity → medium-low temperature and medium salinity → medium-low temperature and medium-low salinity.The capture temperature of fluid inclusions reflects that ore-forming fluids of early stage occurred in medium-high temperature.The features further confirm that different from the typical MVT Zn Pb deposit,Huize deposit is not a low-temperature deposit.The infrared micro-thermometry technique has provided an ideal method to study the p T x conditions of ore-forming fluids and the genesis of Zn Pb deposits in the northeast Yunnan Province.%显微红外测温是利用红外显微镜研究不透明半透明矿物的流体包裹体丰度和分布特征，并与冷热台相结合进行流体包裹体显微测温分析的一种有效的新技术。云南会泽超大型富锗银铅锌矿床是分布于川滇黔接壤区典型的会泽型（HZT）铅锌矿床。本文以该矿床的闪锌矿、方解石流体包裹体为例，应用显微红外测温技术发现闪锌矿中发育大量流体包裹体，按其相态可分为6类：纯气相（V）、富液相气液两相（L＋V）、富气相气液两相（L＋V）、纯液相（L）、含子矿物三相（L＋V＋S）、含 CO2三相（LCO 2＋LH2 O＋VCO2）包裹体，而在热液方解石中仅发现富液相气液两相（L＋V）、纯液相（L）包裹体。闪锌矿中的流体包裹体均一温度集中在2个区间：150～221℃和320～364℃；而盐度变化范围较大，主要集中于3个区间：12．0％～18．0％、5．0％～11．0％、1．1％～5．0％。不同世代闪锌矿流体包裹体均一温度大致反映成矿流体演化的全过程，而方解石流体包裹体均一温度主要反映成矿流体演化的中晚阶段，而且与脉石矿物（方解石）共生的闪锌矿流体包裹体均一温度也高于方解石包裹体均一温度；反映了闪锌矿流体包裹体较方解石更能反映成矿流体的信息，进一步揭示从早成矿阶段到晚成矿阶段，成矿流体大致经历了中高温中盐度→中低温中盐度→中低温中低盐度的演化过程。通过压力校正后的流体包裹体捕获温度反映了早成矿阶段成矿流体呈中高温，进一步证实了该矿床并非低温矿床。通过矿床对比研究，不仅反映了该矿床明显不同于典型的 MVT 铅锌矿床，而且表明了显微红外测温技术为该类矿床成矿流体 p T x 条件及矿床成因的研究提供了新方法与途径，并将在金属矿床成矿流体的研究领域发挥重要作用。