马坑铁钼铅锌多金属矿成矿流体演化及矿床成因类型

马坑铁矿是福建省一个大型铁钼铅锌多金属矿床，赋存于莒舟-大洋花岗岩外接触带上石炭统经畲组-下二叠统栖霞组大理岩与下石炭统林地组石英砂岩之间，矿化阶段经历了从无水矽卡岩阶段（钙铁榴石-透辉石） →含水矽卡岩-磁铁矿阶段（绿帘石-阳起石-绿泥石-钙铁辉石） →硫化物阶段（石英-方解石-萤石-黄铁矿-闪锌矿） →碳酸盐岩阶段（石英-方解石） 演变，而本文对含水矽卡岩-磁铁矿阶段和硫化物阶段中的钙铁辉石、萤石、石英及方解石中流体包裹体所进行岩相学观察和显微测温研究表明，早期含水矽卡岩-磁铁矿阶段包裹体类型主要有含NaCl子晶三相包裹体和富液相两相包裹体，少量富气相两相包裹体；而晚期硫化物阶段包裹体类型主要为富液相两相包裹体。含水矽卡岩-磁铁矿阶段流体出现流体沸腾作用，流体温度范围为448~596℃，两端员组分流体盐度分别为26.5~48.4 wt % NaCl equiv.和2.4~6.9 wt % NaClequiv.；硫化物阶段流体呈现出混合趋势，流体温度和盐度分别为182~343℃和1.9~20.1 wt % NaCl equiv.。流体包裹体的均一温度和盐度的研究结果表明含水矽卡岩-磁铁矿阶段流体主要来自岩浆水，而硫化物阶段流体以岩浆水为主，并有大气降水加入。由于马坑铁矿化形成于含水矽卡岩阶段，铅锌矿化则形成于硫化物阶段，流体沸腾是导致马坑铁矿床形成的主要因素，而流体混合则是引起马坑铁矿床铅锌矿化的主要因素。综合地质与地球化学研究，马坑铁矿床应属于与莒舟-大洋花岗岩有关的矽卡岩型铁矿床。

A Discussion on Ore-forming Fluid Evolution and Genesis of Makeng Fe-Mo-Pb-Zn Polymetallic Deposit,Fujian Province

Makeng iron deposit is a large scale Fe-Mo-Pb-Zn polymentallic deposit in Fujian province hosted in the external contactzone of Juzhou-Dayang granites between the Jingshe Formation-Qixia Formation marbles and the Lindi Formation quartz sandstones.Mineralization stages can be classified into four stages: (1) anhydrous skarn stage (andradite-diopside); (2) hydrous skarn-magnetite(epdiote-chlorite-actinolite-hedenbergite);(3)sulfidesstage(quartz-calcite-fluorite-sphalerite-galena);(4)carbonatesstage(quartz-calcite).Petrographic and microthermometric studies of fluid inclusions in hedenbergite, fluorite, quartz and calcite of different mineralizationstages show that the fluid inclusions related to magnetite mineralization are dominated by daughter mineral-bearing fluid inclusions,liquid-rich aqueous fluid inclusions, and minor vapor-rich fluid inclusions; fluid inclusions in sulfide mineralization stage mainlyinclude liquid-rich aqueous fluid inclusions. Ore fluid in iron oxide stage evidence for boiling at the temperature range of 448 to596℃, with salinities of 26.5 to 48.4 wt % NaCl equiv. for one end member fluid and 2.4 to 6.9 wt % NaCl equiv. for the other endmember fluid. Whereas ore-forming fluid in sulfide stage exhibits a mixing trend, with the temperature and salinity of 182 to 343℃ and1.9 to 20.1 wt % NaCl equiv., respectively. Based on the fluid-inclusion data, early-stage magnetite mineralization fluids wereoriginated mainly from magmatic water, and late-stage sulfide mineralization fluids were derived from mixtures of magmatic water andmeteoric water. Because Fe mineralization was formed in the hydrous skarn stage and Pb-Zn mineralization was formed in the sulfidestage, the early-stage magnetite deposition may have resulted from fluid boiling and the late-stage sulfide deposition may havecontributed to fluid mixing between magmatic water and meteoric water. Overall, the Makeng deposit is interpreted as a skarn typeFe-Mo-Pb-Zn polymentallic deposit related to intermediate-acid pluton based on skarn mineralogy and fluid inclusion characteristics.