Principal physicochemical parameters of natural mineral-forming fluids |
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| Authors: | V B Naumov V A Dorofeeva O F Mironova |
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| Institution: | 1.Vernadsky Institute of Geochemistry and Analytical Chemistry,Russian Academy of Sciences,Moscow,Russia |
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| Abstract: | The authors’ database (which includes data from more than 17500 publications on fluid and melt inclusions in minerals) was
used to generalize information on the principal physicochemical parameters of natural mineral-forming fluids (temperature,
pressure, density, salinity of aqueous solutions, and the gas composition of the fluids). For 21 minerals, data are reported
on the frequency of occurrence of the homogenization temperatures of fluid inclusions in various temperature ranges, which
make it possible to reveal temperature ranges most favorable for the crystallization of these minerals. Data on 5260 determinations
were used to evaluate the frequency of occurrence of certain temperature and pressure ranges of natural fluids within the
temperature intervals of 20–1200°C and 1–12000 bar. Within these intervals, frequencies of occurrence were evaluated for water-dominated
and water-poor or water-free fluid inclusions in minerals. The former are predominant at temperatures below 600°C and pressures
below 4000 bar, whereas the latter dominate at temperatures of 600–1200°C and pressures of 4000-12000 bar. Illustrative examples
are presented for visually discernible magmatic water that exists as an individual high-density phase in melt inclusions in
minerals from various rocks sampled worldwide (in the Caucasus, Italy, Slovakia, United States, Uzbekistan, New Zealand, Chile,
and others). Attention is drawn to the fact that extensive data testify to fairly high (>1000–1500 bar) pressures during hydrothermal
mineral-forming processes. These pressures are much higher not only than the hydrostatic but also the lithostatic pressures
of the overlying rocks. Data on more than 18000 determinations are used to evaluate the frequency of occurrence of certain
temperature and salinity ranges of mineral-forming fluids within the intervals of 20–1000°C and 0–80 wt % equiv. NaCl and
certain temperature and density ranges of these fluids at 20–1000°C and 0.01–1.90 g/cm3. Information is presented on the gas analysis methods most commonly applied to natural fluids in studying fluid inclusions
in minerals in 1965–2007. The average composition of the gaseous phase of natural inclusions is calculated based on more than
3000 Raman spectroscopic analyses (the most frequently used method for analyzing individual inclusions). |
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