Physicochemical formation parameters of hydrothermal mineral deposits: Evidence from fluid inclusions. II. Gold, silver, lead, and zink deposits

Abstract

Information from a database, which was compiled and continuously updated by the authors of this paper and now includes information from 19500 publication on fluid and melt inclusions in minerals, is used to summarize results on the physicochemical formation parameters of hydrothermal Au, Ag, Pb, and Zn deposits. The database provides information on fluid inclusions in minerals from 970 Pb-Zn, 220 Au-Ag-Pb-Zn, and 825 Au-Ag deposits in various settings worldwide. Histograms for the homogenization temperatures of fluid inclusion are presented for the most typical minerals of the deposits. In sphalerite, most homogenization temperatures (1327 measurements) of fluid inclusions lie within the range of 50–200°C with a maximum at 100–200°C for this mineral from Pb-Zn deposits and within the range of 100–350°C (802 measurements) with a maximum at 200–300°C for this mineral from Au deposits. Data are presented on fluid pressures at Au (1495 measurements) and Pb-Zn (180 measurements) deposits. The pressure during the preore, ore-forming, and postore stages at these deposits ranged from 4–10 to 6000 bar. The reason for the high pressures during preore stages at the deposits is the relations of the fluids to acid magmatic and metamorphic processes. More than 70% of the fluid pressures values measured at Pb-Zn deposits lie within the range of 1–1500 bar. Au-Ag deposits are characterized by higher fluid pressures of 500–2000 bar (61% of the measurements). The overall ranges of the salinity and temperature of the mineral-forming fluid at Au-Ag (6778 measurements) and Pb-Zn (3395 measurements) deposits are 0.1–80 wt % equiv. NaCl and 20–800°C. Most measurements (∼64%) for Au-Ag deposits yield fluid salinity <10 wt % equiv. NaCl and temperatures of 200–400°C (63%). Fluids at Pb-Zn deposits are typically more saline (10–25 wt % equiv. NaCl, 51% measurements) and lower temperature (100–300°C, 74% measurements). Several measurements of the fluid density fall within the range of 0.8–1.2 g/cm3. The average composition of volatile components of the fluids was evaluated by various techniques. The average composition of volatile components of fluid inclusions in minerals is calculated for hydrothermal W, Au, Ag, Sn, and Pb-Zn deposits, metamorphic rocks, and all geological objects. The Au, Ag, Pb, and Zn concentrations in magmatic melts and mineral-forming fluids is evaluated based on analyses of individual inclusions.