Abstract:

Makeng iron deposit is a large scale Fe-Mo-Pb-Zn polymentallic deposit in Fujian province hosted in the external contact
zone 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 mineralization
stages 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 to
596℃, 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 end
member fluid. Whereas ore-forming fluid in sulfide stage exhibits a mixing trend, with the temperature and salinity of 182 to 343℃ and
1.9 to 20.1 wt % NaCl equiv., respectively. Based on the fluid-inclusion data, early-stage magnetite mineralization fluids were
originated mainly from magmatic water, and late-stage sulfide mineralization fluids were derived from mixtures of magmatic water and
meteoric water. Because Fe mineralization was formed in the hydrous skarn stage and Pb-Zn mineralization was formed in the sulfide
stage, the early-stage magnetite deposition may have resulted from fluid boiling and the late-stage sulfide deposition may have
contributed to fluid mixing between magmatic water and meteoric water. Overall, the Makeng deposit is interpreted as a skarn type
Fe-Mo-Pb-Zn polymentallic deposit related to intermediate-acid pluton based on skarn mineralogy and fluid inclusion characteristics.

Key words: Juzhou-Dayang granites, fluid inclusion, fluid boiling, Makeng deposit, Fujian Province