Volcanic Gases

Vulkan, m. volcano Vulcan, -asbest, m. vulcanized asbestos, -fiber, /. Vulcanized Fiber. T.N. -gas, n. volcanic gas. -glas, n. volcanic glass tempered glass. 

There are three possible mechanisms for generating the strongly acid solution which caused the advanced argillic alteration (1) alteration caused by the vapor-dominated system as inferred by White et al. (1971) (2) alteration caused by the oxidation of H2S near the surface and (3) alteration by volcanic gas and/or hot water condensed from a volcanic gas. Among them, (3) is the most attractive mechanism given the following evidence and considerations. 

When temperatures of volcanic gases containing SO2 decrease, the reaction (1-35) proceeds to the right hand side. This reaction causes a considerable decrease in pH due to the formation of sulfuric acid. Advanced argillic alteration is formed by the interaction of volcanic gas with groundwater. 

These data could be explained by the sulfur of barite from epithermal Au-Ag-Te deposits came both from volcanic gas (SO2) and marine sulfate, but that of epithermal base-metal deposits came from marine sulfate and oxidation of H2S. 

Fig. 2.17. 8D and S 0 of Osorezan hot springs (Aoki, 1992b). P deep hotwater, HTVG high temperature volcanic gas, solid circle groundwater, the other symbols hot springs in this area. 

Previous studies demonstrated that the CO2 fluxes by hydrothermal solution and volcanic gas from midoceanic ridges play an important role in the global CO2 cycle and affect the CO2 concentration in the atmosphere (e.g., Javoy, 1988). However, submarine volcanism and hydrothermal activity occur not only at midoceanic ridges but also at island arc and back-arc basins as already noted. 

Sano and Williams (1996) calculated present-day volcanic carbon flux from subduction zones to be 3.1 x 10 mol/year based on He and C isotopes and C02/ He ratios of volcanic gases and fumaroles in circum-Pacific volcanic regions. Williams et al. (1992) and Brantley and Koepenich (1995) reported that the global CO2 flux by subaerial volcanoes is (0.5-2.0) x lO mol/m.y. and (2-3) x 10 mol/m.y. (maximum value), respectively. Le Guern (1982) has compiled several measurements from terrestrial individual volcanoes to derive a CO2 flux of ca. 2 x 10 mol/m.y. Le Cloarec and Marty (1991) and Marty and Jambon (1987) estimated a volcanic gas carbon flux of 3.3 X 10 mol/m.y. based on C/S ratio of volcanic gas and sulfur flux. Gerlach (1991) estimated about 1.8 x 10 mol/m.y. based on an extrapolation of measured flux. Thus, from previous estimates it is considered that the volcanic gas carbon flux from subduction zones is similar to or lower than that of hydrothermal solution from back-arc basins. 

The As (arsenic) concentration of seawater is controlled by input of rivers, sedimentation on the seafloor, weathering of the seafloor, exchange between atmosphere and seawater, volcanic gas input, and hydrothermal input. Previous studies on the geochemical cycle of As have not taken into account the hydrothermal flux of As. Therefore, hydrothermal flux of As from back-arc, island arc and midoceanic ridges to ocean is considered below. 

The flux of volcanic gas to ocean has not been estimated. Walsh et al. (1979) estimated As flux of volcanic gas to atmosphere to be 2.8 x 10 g/year. Therefore, this flux to ocean is also small. 

During the middle Miocene, Kuroko deposits, polymetallic vein-type deposits, gold-quartz vein-type deposits and Sb and Hg vein-type deposits were formed (see sections 1.3 and 1.6). Many vein-type deposits were formed not only in and nearby the Japanese Islands, but also at middle Miocene in northwest USA (Basin and Range Lipman, 1982), and elsewhere in the circum-Pacific regions (e.g., Peru). It is probable that large amounts of CO2 effused into the atmosphere from hydrothermal solution associated with this widespread mineralization and volcanic gas from subduction zones, causing an increase in temperature. 

In this section, Ishikawa (1996), and Kashiwagi et al. (2000) studies are described. Then, their calculated results are given, emphasizing the influence of hydrothermal and volcanic gas CO2 flux from back arc basins and island arc on CO2 concentration of atmosphere and climate change and are compared with the changes in CO2 and temperature obtained by analytical and paleontological data (S 0 of foraminiferal shell, Ce anomaly, 5 C, etc.). 

In Chapter 3, hydrothermal and volcanic gas fluxes from submarine back-arc basins and island arc are estimated. These fluxes are compared with midoceanic ridge hydrothermal fluxes. Particularly, hydrothermal flux of CO2 is considered and the influences of this flux on global long-term carbon cycle and climate change in Tertiary-Quaternary ages are discussed in Chapter 4. 

The purpose of this chapter is to outline the simplest methods of arriving at a description of the distribution of species in mixtures of liquids, gases and solids. Homogeneous equilibrium deals with single phase systems, such as electrolyte solutions (e.g., seawater) or gas mixtures (e.g., a volcanic gas). Heterogeneous equilibrium involves coexisting gaseous, liquid and solid phases. 

Volcanic Gas Condensate, Vulcano, Italy [18]0 Volcanic Gas Condensate, Kudriavy, Russia [18] 0 ... 

Micellaneous Volcanic Gas Condensate [2, 19] Micellaneous Geothermal Water [5, 6]... 

Figure 6. Stable-Cl isotopic composition of fumarolic minerals, volcanic gas condensates and geothermal waters. Bracketed numbers correspond to references listed in Figure 3, Figure 4, and, [18] Wahrenberger et al. 1997 [19] Godon et al. 2004 and [20] Kaufmann 1989.

Wahrenberger C, Eastoe CJ, Seward TM, Dietrich V (1997) Stable chlorine isotope composition of volcanic gas condensates, y" Annual Goldschmidt Conf 213... 

Below are given analyses of volcanic gas from different parts of the world by different authorities —... 

A new interesting development has been offered by Orgel and coworkers (Leman et al., 2004) they showed that carbonyl sulfide (COS), a simple volcanic gas, brings about the formation of peptides from amino acids under mild conditions in aqueous solution, and in yields approaching 80% in minutes to hours at room temperature. Dipeptides and tripeptides were thus obtained, but in this case too the answer to the question of long chains with a regulated order of sequence remains elusive. 

Rock-salt occurs to a very small extent as a volcanic product, where it is probably produced by the action of hydrogen chloride present in the volcanic gas upon the lava. It is found as a white crust or loose powder in the crater. Published analyses of crater salt show that the ratio of KC1 NaCl ranges from 1 0 062 to 1 O 948. The data in Table XV are selected from published analyses of rock-salt with... 

Francis P, Burton MR, Oppenheimer C (1998) Remote Measurements of Volcanic Gas Compositions by Solar Occulation Spectroscopy. Nature 396 567... 

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