Search results for "element"
showing 10 items of 13601 documents
Reaction path models of magmatic gas scrubbing
2016
Gas-water-rock reactions taking place within volcano-hosted hydrothermal systems scrub reactive, water-soluble species (sulfur, halogens) from the magmatic gas phase, and as such play a major control on the composition of surface gas manifestations. A number of quantitative models of magmatic gas scrubbing have been proposed in the past, but no systematic comparison of model results with observations from natural systems has been carried out, to date. Here, we present the results of novel numerical simulations, in which we initialized models of hydrothermal gas-water-rock at conditions relevant to Icelandic volcanism. We focus on Iceland as an example of a "wet" volcanic region where scrubb…
ASSESSING TRACE ELEMENT (DIS)EQUILIBRIUM AND THE APPLICATION OF SINGLE ELEMENT THERMOMETERS IN METAMORPHIC ROCKS
2018
Abstract Empirical and experimental calibration of single element solubility thermometers, such as Zr-in-rutile, Zr-in-titanite, Ti-in-zircon, and Ti-in-quartz, within the past 13 years has greatly expanded our ability to assess the pressure and temperature conditions of individual minerals associated with specific textures in metamorphic rocks. Combined with advances in in situ techniques for analyzing trace concentrations, this has led to an increase in the combined use of single element thermometers, geochronometers, and isotope ratios, often simultaneously, in metamorphic minerals. Here we review the calibration and application of single element thermometers at the pressure and temperat…
Using mosses as biomonitors to study trace element emissions and their distribution in six different volcanic areas
2017
Volcanoes emit SO2, CO2, and H2S, but also trace elements gases and particles such as As, Cd, Cr, Cu, Hg, Ni, Pb, and Sb. Active moss bag biomonitoring, an easy to apply and low budget method, was used to determine trace element release from volcanic areas of different geological context and climates. Exposure height variations (0.7â1.6 m above ground) due to different availability of natural tie points did not affect the results. Accumulation was linear for exposure durations from three days to nine weeks, so values were comparable by normalization to moss exposure time. Uncovered moss bags showed higher accumulation than co-exposed covered ones because of additional dust and wet deposit…
Is there a global carbonate layer in the oceanic mantle?
2021
co-auteur étranger; International audience; Previous modeling of carbonate subduction by high‐pressure experimentation has allowed to propose scenarios for bulk carbon return to the mantle, but the detailed transfer mechanisms have seldom been studied. We monitored carbonate – silicate reactions by combining high‐pressure experiments and synchrotron‐based x‐ray diffraction. Carbonates break down at moderate pressure and high temperature and CO2 is trapped at grain boundaries. Further isothermal compression yields melting, which may control continuous carbon introduction, first in the mantle wedge, and next, away from the wedge. Carbon presence has been discussed in a variety of magmatic con…
The imprint of subduction fluids on subducted MORB-derived melts (Sierra del Convento Mélange, Cuba)
2011
International audience; Major and trace element signatures and Sr-Nd-Pb isotope data for muscovite (Ms)-bearing amphibolite blocks and associated muscovite-bearing trondhjemite and quartz-muscovite rocks from the Sierra del Convento melange (eastern Cuba) indicate that Proto-Caribbean oceanic crust underwent wet partial melting processes during Mesozoic subduction and after accretion to the upper plate. Trace element normalized patterns of Ms-bearing amphibolites are enriched in light rare earth elements (LREE) and large-ion lithophile elements (LILE) and evidence variable trace element transfer from the Proto-Caribbean subducting slab to the mantle wedge. Ms-bearing trondhjemites show LREE…
Trace elements in the thermal groundwaters of Vulcano Island (Sicily)
2000
The chemical concentrations of many trace elements that have never before been examined in Vulcano Island groundwaters are reported. Chemical data indicate that rock composition is not the only factor determining the metal content in the aqueous system. The observed concentrations depend mainly on: (1) the chemical composition of the host rocks; (2) the chemical–physical conditions of the weathering solution (temperature, acidity, redox conditions); (3) input of magmatic gases; (4) adsorption of metal ions on oxide particles, formation of soluble complexes and/or precipitation of solid phases. Chloride complexes in solution are of minimal significance for all elements with the exception of …
Abiotic and biotic controls on methane formation down to 2.5 km depth within the Precambrian Fennoscandian Shield
2017
Abstract Despite a geological history characterised by high temperature and pressure processes and organic carbon deprived crystalline bedrock, large amounts of hydrocarbons are found in deep groundwaters within Precambrian continental shields. In many sites, methane comprises more that 80% of the dissolved gas phase reaching concentrations of tens of mmol l −1 . In this study, we used isotopic methods to study the carbon isotope systematics and sources of crustal methane within the Fennoscandian Shield. The main study sites were the Outokumpu Deep Drill Hole and the Pyhasalmi mine in Finland, both of which allow groundwater sampling down to 2.5 km depth and have been previously studied for…
Hydrochemical mercury distribution and air-sea exchange over the submarine hydrothermal vents off-shore Panarea Island (Aeolian arc, Tyrrhenian Sea)
2017
Abstract There is a growing concern about the mercury (Hg) vented from submarine hydrothermal fluids to the marine surrounding and exchange of dissolved gaseous mercury (DGM) between the sea surface and the atmosphere. A geochemical survey of thermal waters collected from submarine vents at Panarea Island (Aeolian Islands, southern Italy) was carried out in 2015 (15–17th June and 17–18th November), in order to investigate the concentration of Hg species in hydrothermal fluids and the vertical distribution in the overlying water column close to the submarine exhalative area. Specific sampling methods were employed by Scuba divers at five submarine vents located along the main regional tecton…
Testing Sediment Connectivity at the Experimental SPA2 Basin, Sicily (Italy)
2017
The concept of sediment delivery can be used as a measure of sediment connectivity, and it can be linked to the structural connectivity (morphological unit, slope length, slope steepness, travel time) of a basin and to the hydrological connectivity (rainfall–runoff processes at morphological unit scale). In this paper, the sediment connectivity concept was tested at basin scale applying SEdiment Delivery Distributed model, which takes into account the hillslope sediment transport, and using sediment yield measurements carried out at SPA2 experimental basin (Sicily, Italy). For the SPA2 basin discretized into morphological units, the SEdiment Delivery Distributed model was first calibrated a…
Photoreduction of gaseous oxidized mercury changes global atmospheric mercury speciation, transport and deposition
2018
9 pags, 8 figs. -- Correction autor: https://doi.org/10.1038/s41467-022-28455-w http://hdl.handle.net/10261/268181