ИСТИНА

The published data on the physicochemical parameters and chemical composition of the hydrothermal mineralizing fluids of gold deposits were collected and analyzed in terms of the geological history of the Earth. The data array included 5570 definitions of parameters for 360 gold deposits of various ages, from different regions of the Earth and the various genetic types: orogenic, shear zone related, epithermal, porphyry, “carlin”, intrusion-related, IOGS and others. The dataset of the Raman definitions of gas composition consists of more than 500 tests. The general trends in the changes of physicochemical parameters and the chemical composition of the mineral-forming fluids in the Earth history are revealed. They are partly associated with increasing of the erosion level of hydrothermal systems with increasing of their age, which is consistent with the conclusions of the article (Kesler, Wilkinson, 2006). The point is primarily about the increasing of the average quantities of mineral-forming fluid pressure from the Cenozoic deposits to the Proterozoic ones, the absence of low-pressure fluid in the Precambrian deposits and the prevalence of weakly mineralized fluids in young fields. The data of the Raman-microanalysis of gas inclusions show the change in the average composition of the gas phase of fluid inclusions in the quartz from gold deposits with their age (mol %): Archean – CO2 78.8, CH4 20.7, N2 0.4, CO2/CH4 3.8 (n=114), Proterozoic – CO2 71.5, CH4 13.5, N2 14.5, CO2/CH4 5.3 (n=103), Paleozoic – CO2 92.2, CH4 5.8, N2 2.0, CO2/CH4 15.9 (n=177), Mesozoic – CO2 77.5, CH4 5.0, N2 17.5, CO2/CH4 15.5 (n=63), Cenozoic – CO2 94.4, CH4 0.8, N2 4.8, CO2/CH4 120.0 (n=97). There is a regular increase of the CO2/CH4 ratio for fluids from the ancient gold deposits to the young ones. The revealed regularity is associated not only with different erosion sections of the deposits and the depth of capture of fluids into inclusions. The composition of the gas phase is affected by the general trend of the fluid regime change in time, associated with an increase in the proportion of oxidized forms of carbon from the early epochs to the late ones. This is consistent with the data of the carbon isotope studies of fluid inclusions in quartz of Archean and Proterozoic African gold deposits. These studies have shown the presence of different geochemical reservoirs of carbon dioxide, from which it enters the Archean and Proterozoic ore-forming systems of African gold deposits (Lüders et al., 2015).