Gas composition of the fluids formed ore deposits at different geological periods (from the Archean to the Cenozoic)

An original database compiled by the authors on volatile components of mineral-hosted fluid inclusions currently includes 12 470 analyses from 480 publications and was used to calculate the average gas phase composition of fluids that formed hydrothermal deposits throughout the Earth’s geological evolution, from the Archean to Cenozoic. The paper reviews the methods used in the study, their potential errors, and limitations. Characteristics of the gas composition of fluids are traced for more than 300 ore deposits of Au, Sn, W, Cu, Cu, Pb, Zn, Sb, Mo, and U. The dominant volatile component of natural mineralizing fluids in the Earth’s crust is carbon dioxide, regardless of the geologic age. The fluids contain subordinate amounts of reduced carbon species (methane) and nitrogen, as well as minor amounts of hydrogen sulfide and some other gases. The Cenozoic fluids commonly contain more nitrogen than methane. These relations are occasionally also found in the Precambrian fluids. The CO2/CH4 ratio as an indicator of the redox state of the system notably increased over the Earth’s geological history.