Sulfate from volcanism

Similar heterogeneous reactions also can occur, but somewhat less efticientiy, in the lower stratosphere on global sulfate clouds (ie, aerosols of sulfuric acid), which are formed by oxidation of SO2 and COS from volcanic and biological activity, respectively (80). The effect is most pronounced in the colder regions of the stratosphere at high latitudes. Indeed, the sulfate aerosols resulting from emptions of El Chicon in 1982 and Mt. Pinatubo in 1991 have been impHcated in subsequent reduced ozone concentrations (85). 

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. 

Contributions both from sulfide sulfur leached from volcanic rocks and marine sulfate in Green tuff. 

On the early Earth, ions were mobilized from volcanic rocks by chemical weathering. Rivers and hydrothermal emissions transported these chemicals into the ocean, making seawater salty. These salts are now recycled within the crustal-ocean-atmosphere fectory via incorporation into sediments followed by deep burial, metamorphosis into sedimentary rock, uplift, and weathering. The last process remobilizes the salts, enabling their redelivery to the ocean via river runoff and aeolian transport. In the case of sodium and chlorine, evaporites are the single most important sedimentary sink. This sedimentary rock is also a significant sink for magnesium, sulfate, potassium, and calcium. 

Second, reaction 8.9 and other relevant reactions appear to occur preferentially on available solid surfaces, which are often ice crystals but may also be particles of sulfate hazes from volcanic eruptions or human activity. Third, volatile bromine compounds are even more effective (via Br atoms) than chlorine sources at destroying ozone methyl bromide is released into the atmosphere naturally by forest fires and the oceans, but anthropogenic sources include the use of organic bromides as soil fumigants (methyl bromide, ethylene dibromide) and bromofluorocarbons as fire extinguishers (halons such as CFsBr, CF2BrCl, and C2F4Br2). 

A very different conceptual model is based on the assumption that the early Martian atmosphere was dominated by acidic volatiles from volcanic activity, which leads directly to sulfuric acid weathering (Fig. 5.15). This model leads to the dominance of sulfate minerals and leaves open the possibility of both ferrous and ferric iron sulfates. In addition to atmospheric acidification,... 

Although TES and THEMIS are sensitive to carbonates and sulfates, these minerals have not yet been detected unambiguously from orbit (Bandfield, 2002). The low carbon abundance in APXS-analyzed soils rules out much carbonate, although appreciable sulfur and chlorine are present in all soils. Thermodynamic stability considerations suggest that sulfates and iron carbonates should be present under martian conditions (Clark and Van Hart, 1981 Catling, 1999). It is unclear whether sulfate formed by reactions with acidic vapor from volcanic exhalations (Banin et al., 1997) or evaporation of surface brines (Warren, 1998 McSween and Harvey, 1998). 

Other evidence for low Archean atmospheric oxygen concentrations come from studies of mass-independent sulfur isotope fractionation. Photochemical oxidation of volcanic sulfur species, in contrast with aqueous-phase oxidation and dissolution that characterizes the modem sulfur cycle, may have been the major source of sulfate to seawater in the Archean (Farquhar et al., 2002 Farquhar et al., 2000). Distinct shifts in and in sulfide and sulfate from... 

Hence the Archaean sulfur cycle (Fig. 5.5) would comprise inputs into the atmosphere and oceans from volcanic gases and into the oceans from hydrothermal activity but not river-borne sulfate. In addition, in the anoxic oceans, the oxidative alteration of the ocean floor would not take place. Thus the surface sulfur reservoir would have been small and most sulfur recycled back into the mantle as sulfide minerals. The sulfate part of the sulfur cycle is unlikely to have been fully operational until the late Proterozoic (Canfield, 2004). 

Heavy Rare Earth Element). Therefore, it is considered that negative Ce and positive Eu anomalies in hydrothermally altered volcanic rocks, Kuroko ores, and ferruginous chert and LREE enrichment in the Kuroko ores have been caused by hydrothermal alteration and precipitations of minerals from hydrothermal solution responsible for sulfides-sulfate (barite) mineralization. 

Origin of sulfide sulfur of epithermal base-metal veins is thought to be same as that of Kuroko deposits because average 8 S value of base-metal vein-type deposits is - -4.7%o which is identical to that of Kuroko deposits (- -4.6%o) (Shikazono, 1987b). Namely, sulfide sulfur of base-metal veins came from igneous rocks, sulfate of trapped seawater in marine sedimentary rocks, calcium sulfate (anhydrite, gypsum) and pyrite. 8 S of sulfide sulfur of epithermal base-metal vein-type deposits can be explained by the interaction of seawater (or evolved seawater) with volcanic rocks. 

In contrast to the of hydrothermal solution for the vein, that of pyrite in hydrothermally altered rocks (Shimanto Shale) varies very widely, ranging from —5%o to - -15%o. Based on the microscopic observation, pyrite with low values less than 0%o is usually framboidal in form, suggesting that low 8 S was caused by bacterial reduction of seawater sulfate. There are two possible interpretations of high 8 " S values (+10%o to - -15%o). One is the reduction of seawater sulfate in a relatively closed system. The other one is a contribution of volcanic SO2 gas. As noted already, volcanic SO2 gas interacts with H2O to form H2SO4 and H2S. value of SO formed by... 

Sulfur has four unique characteristics related to its occurrence and chemistry in soil. As sulfate, it is one of the principle counterions that keep the soil electrically neutral. Soil receives constant additions of sulfur through volcanic activity around the world and industrial pollution, usually in the form of acid rain. This means that soils usually have sufficient sulfur for plant growth. Lastly, plants can take and use sulfur dioxide from the air as a source of sulfur for growth [22,38],... 

Natural emissions of sulfur compounds to the atmosphere occur from a variety of sources, including volcanic eruptions, sea spray, and a host of biogenic processes (e.g., Aneja, 1990). Most of the volcanic sulfur is emitted as S02, with smaller and highly variable amounts of hydrogen sulfide and dimethyl sulfide (CH3SCH3). Sea spray contains sulfate, some of which is carried over land masses. 

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