Volatile contents of primitive bubble-bearing melt inclusions from Klyuchevskoy volcano, Kamchatka: Comparison of volatile contents determined by mass-balance versus experimental homogenization

Primitive olivine-hosted melt inclusions provide information concerning the pre-eruptive volatile contents of silicate melts, but compositional changes associated with post-entrapment processes (PEP) sometimes complicate their interpretation. In particular, crystallization of the host phase along the wall of the melt inclusion and diffusion of H+ through the host promote CO2 and potentially S or other volatiles to exsolve from the melt into a separate fluid phase. Experimental rehomogenization and analysis of MI, or a combination of Raman spectroscopy, numerical modeling, and mass balance calculations are potentially effective methods to account for PEP and restore the original volatile contents of melt inclusions. In order to compare these different approaches, we studied melt inclusions from a suite of samples from Klyuchevskoy volcano (Kamchatka Arc) for which volatile compositions have been determined using experimental rehydration, Raman spectroscopy, and numerical modeling. The maximum CO2 contents of melt inclusions are in agreement (~3600-4000 ppm), regardless of the method used to correct for CO2 in the bubble, but significantly more uncertainty is observed using mass balance calculations. This uncertainty is largely due to the lack of precision associated with the petrographic method of determining bubble volumes and may also be related to the presence of daughter minerals at the glass-bubble interface

Composition of Fluids Responsible for Gold Mineralization in the Pechenga Structure-Imandra-Varzuga Greenstone Belt, Kola Peninsula, Russia.

This study presents the first fluid inclusion data from quartz of albite–carbonate–quartz altered rocks and metasomatic quartzite hosting gold mineralization in the Pechenga structure of the Pechenga– Imandra–Varzuga greenstone belt. A temperature of 275–370°C, pressure of 1.2–4.5 kbar, and the fluid composition of gold-bearing fluid are estimated by microthermometry, Raman spectroscopy, and LA-ICP-MS of individual fluid inclusions, as well as by bulk chemical analyses of fluid inclusions. In particular, the Au and Ag concentrations have been determined in fluid inclusions. It is shown that albite–carbonate–quartz altered rocks and metasomatic quartzite interacted with fluids of similar chemical composition but under different physicochemical conditions. It is concluded that the gold-bearing fluid in the Pechenga structure is similar to that of orogenic gold deposits

Volumetric properties of CO{sub 2}-CH{sub 4}-N{sub 2} fluids at 200{degree}C and 1000 bars: A comparison of equations of state and experimental data. Chapter 4

Predictions of molar volume, excess molar volume, and isochoric P-T trajectories from 13 published equations of state are compared with one another and with preliminary volumetric data for CO{sub 2}-CH{sub 4}-N{sub 2} fluids at 200{degrees}C and 1000 bars. The equations of state investigated represent a wide variety of empirical and semi-empirical approaches to the modeling of fluids. The experimental data indicate that excess volumes of CO{sub 2}-CH{sub 4}-N{sub 2} mixtures are small (<3% of the total volume of the mixture, except near the critical point of CO{sub 2}). The NIST software package DDMIX yields volumetric properties that are most consistent with our experimental results. Differences in the calculated volumetric properties of mixtures from the different equations of state are significant For example, estimates of the equilibrium trapping temperature of a fluid inclusion (2000 bars, 60% CO{sub 2}-20% CH{sub 4}20% N{sub 2}mixture, V=59.10 cm{sup 3}/mole) calculated from various equations of state range from 462-570{degrees}C. The major source of error in calculated volumetric properties of fluid mixtures is the inability of equations of state to accurately predict the volumetric properties of the pure components