Deposition of trace elements from high temperature gases of Satsuma-Iwojima volcano

Abstract

The Satsuma-Iwojima volcano has been emitting continuously high temperature (600• to 900• C) gases for at least 800 years. We identified the minerals that form in response to closed-system cooling of these gases and from airmixing reactions. Major differences compared with the sublimates observed at other volcanoes are the occurrence of wulfenite (PbMoO 4 ) and several mixed chlorides. This is the first report of wulfenite in fumarolic deposits. Thermochemical modeling shows that wulfenite precipitates between 540• and 490• C from a gas with lower sulfur content and/or higher f O 2 , and a higher Mo content (log f SO 2 = −2.1, log f H 2 S = −5, log f O 2 = −18.6, log f H 2 MoO 4 = −4.5, T = 500• C) than the previously reported gas composition. The occurrence of abundant K, Pb, Fe, Zn, Rb and Cs mixed chlorides may be promoted by the low S/Cl of the Satsuma-Iwojima high temperature gases. Natural sublimates of metallic elements (molybdenite, wulfenite, anglesite, Tl-Pb and Tl-Bi sulfides, Mo oxydes and Pb oxides) are deposited along the fumarolic conduit and on the ground under conditions of variable temperatures and f O 2 . The increase in f O 2 due to the mixing of the gases with the atmosphere reduces the volatility of several elements (As, Sn, Na, K and Pb) by promoting their condensation at higher temperatures. As air mixes with volcanic gas in the fumarolic plume, we can expect to find these metals as aerosols.

Hydrothermal alteration, fumarolic deposits and fluids from Lastarria Volcanic Complex: A multidisciplinary study

“…The origin of polyhalite could be attributed to a strong hydrothermal alteration of volcanic rocks by very low pH fluids (del Moro et al, 2011), sublimation from high temperature fumaroles, deposition from aerosols and vapours in low temperature fumaroles, and by alteration of volcanic rocks by oxidation and/or hydration processes (Forti, 2005 12 ] is a product of the reaction between galena and oxidizing pyrite, especially in lead deposits (Anthony et al, 2003). This is consistent with the presence of pyrite, galena and Pb-bearing minerals in fumarolic deposits, like has been reported in diverse active volcanoes (e.g., Africano and Bernard, 2000;Africano et al, 2002;Yudovskaya et al, 2008). However, in LVC only pyrite has been detected in fumarolic deposits, and the source for Pb could be inferred from at least two processes a. supplied directly from the gas phase, which is less probable due to its low concentration (Table 3), or b. directly extracted from galena or another Pb-bearing mineral present in deeper parts of the volcanic structure.…”

RHENIUM-RICH MOLYBDENITE AND RHENIITE IN THE PAGONI RACHI Mo-Cu-Te-Ag-Au PROSPECT, NORTHERN GREECE: IMPLICATIONS FOR THE Re GEOCHEMISTRY OF PORPHYRY-STYLE Cu-Mo AND Mo MINERALIZATION

“…Primary wulfenite has been recognized as a fumarolic sublimate at the Satsuma-Iwojima volcano, in Japan, together with molybdenite, anglesite and Pb oxides, deposited at temperatures between 540 and 490°C from a gas with high Mo content under oxidizing conditions (Africano et al 2002). This assemblage resembles that of sublimates from the Kudriavy volcano.…”

Trace elements in the gas emissions from the Erta Ale volcano, Afar, Ethiopia

“…However, the adverse influence of the element deposition in the tubes can be transformed into a powerful instrument to explore volcanic gas chemistry. The deposition of sublimates onto the inner walls of silica tubes was described in detail by Bernard and Le Guern (1982) and was later used by a number of researchers (including Quisefit et al, 1989;Toutain et al, 1990;Symonds, 1993;Africano et al, 2002;Zelenski and Bortnikova, 2005, etc.). As can be concluded from the comparison of the concentrations of TE in condensates and sublimates, the silica tube works as an effective concentrator of trace elements, with enrichment of up to 8-9 orders of magnitude compared with raw volcanic gases.…”