Data for: Uptake of gaseous Thallium, Tellurium and Vanadium into fumarole alums and implication for trace metal degassing (Lascar volcano, Chile)

Major, trace and isotope (O, Pb) composition of a fumarolic crust from the Lascar volcano (Chile) Table S1 : In situ major and trace element concentrations Table S2 : In situ oxygen isotope composition Table S3 : Bulk Pb and Sr isotope composition

Data for: Uptake of gaseous Thallium, Tellurium and Vanadium into fumarole alums and implication for trace metal degassing (Lascar volcano, Chile)

Major, trace and isotope (O, Pb) composition of a fumarolic crust from the Lascar volcano (Chile) Table S1 : In situ major and trace element concentrations Table S2 : In situ oxygen isotope composition Table S3 : Bulk Pb and Sr isotope composition

Sr–Pb isotopes signature of Lascar volcano (Chile): Insight into contamination of arc magmas ascending through a thick continental crust

co-auteur étrangerInternational audienc

Temporal oxidation of Lascar volcanic gases (Chile) recorded by V-Tl-Te zonation of a fumarolic crust

International audienc

Pb-Sr isotope temporal variations on juvenile ash samples from the last eruptive period of Tungurahua volcano (1999-2016)

International audienc

Uptake of gaseous thallium, tellurium, vanadium and molybdenum into anhydrous alum, Lascar volcano fumaroles, Chile

co-auteur étrangerInternational audienceFormation of secondary sulfate minerals during the reaction between volcanic gases and rocks modulates the compositionand flux of gaseous emanations. We report on the sub-surface formation of anhydrous alum (MIMIII(XVIO4)2with MI=-NH4+,Na+,K+;MIII=Al3+,Fe3+and XVI=S6+,Mo6+) in the 330°C fumaroles of the Lascar volcano (Chile). The alumoccurs as a few millimetres thick crust that grew internally by two-way diffusion of reaction gases and diffusive influx of rockcations within the crust. The average growth rate is estimated at ca. 0.3lm/day, based on the 19-year-long activity of thedegassing fracture hosting the crust. The growth rate is controlled by the slow migration of the rock cations and decreasestowards crust rim. The crust selectively concentrates Tl, V and Te (thousands oflg/g) and to a lesser extent Mo (hundredsoflg/g). The uptake of gaseous Tl, V and Mo is due to the possibility for these elements to enter the MI,MIIIand XVIsites ofalum, respectively. The process of Te uptake must be related to the incorporation of Tl and V with which Te tightly correlates.Extensive substitution of Tl, V and Te occurs at the surface of the crust where the supply of rock cations is the lowest. Suchsurface enrichment does not occur for Mo, because Mo substitutes for S, another element from the gas. These findings suggestthat the surface of mature alum crust has a high adsorption capacity for those gaseous metals able to compensate for the lackof rock-derived cations. Based on the composition of gases escaping from the fracture hosting the crust, it is estimated that thepartition coefficients of Tl (3.3107), V (1.1107) and Te (0.6107) between crust surface and gases are two to four ordersof magnitude higher than for other volatile metals and metalloids. It follows that gases equilibrating with anhydrous alumslose between 77 and 95% of their initial Tl content, but less than 1% of Pb. Given the Tl emission rate of Lascar volcano(5 g/day), between 17 and 104 g of toxic Tl would deposit every day if all Lascar gases were to equilibrate with anhydrousalums. This study suggests that anhydrous alums significantly immobilize Tl, V and Te in the ground of quiescent volcanoes,reducing the atmospheric emissions of these three elements.Ó2020 Elsevier Ltd. All rights reserved

Arc volcano activity driven by small-scale metasomatism of the magma source

International audienceArc volcanism arises from the release of fluids from the descending slab, which enables melting in the mantle wedge by lowering the solidus temperature. Metasomatism—compositional alteration by fluids—of the mantle is known to have an important role in magma production in volcanic arcs over long spatial and temporal scales. However, the episodic eruption of individual arc volcanoes is generally thought to be regulated primarily by the evolution and recharge of crustal magma reservoirs, with no established link to mantle processes. Here we show a link between eruptive activity in the 1999-2016 eruption sequence of Tungurahua volcano in Ecuador and small-scale metasomatism of the magma source. From high-resolution time series of the Pb and Sr isotopic composition of ashes, we determine that during the eruption sequence, the average rate of magma production varies logarithmically with the degree of source metasomatism, and that the sequence ended because of the exhaustion of the metasomatized source during its final weeks. Such an association points to mantle metasomatism over short spatial and temporal scales regulating magma production and ultimately eruptive activity of Tungurahua volcano. The influence of metasomatism on individual eruptions has been recognized for basaltic shield volcanoes, but our findings suggest that it is also a plausible mechanism to produce long-lasting eruptions at andesitic arc volcanoes

Lower crustal vs. mantle wedge fingerprint in the Ecuadorian arc magmas: Contribution of Pb isotopes from the Cotopaxi volcano

International audiencePb isotopes are very sensitive to continental crustal contamination. With these isotopes, we are able to discriminate the contribution of the lower crust from that of the upper crust. With the objective of constraining the genesis of arc magmas by focusing here on the role of the continental crust, we propose a geochemical study on eruptive products of the Cotopaxi volcano. This choice is based on the fact that Cotopaxi is constructed on a thick continental crust and that its magmatic series span a large geochemical diversity, from basaltic andesites to rhyolites (Garrison et al., 2006, Garrison et al., 2011). We provide here 23 new high-precision Pb isotope data obtained on tephras, covering the range from andesites to rhyolites, over a period ranging from pre-Holocene to historical times. Isotopes variations are comprised between 18.980 and 18.923 for 206 Pb/ 204 Pb, 15.629 and 15.640 for 207 Pb/ 204 Pb and 38.717 and 38.765 for 208 Pb/ 204 Pb. Comparing these results with published data, we observe that our data have restricte