Search results for "position"
showing 10 items of 6771 documents
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 …
Activity-composition relations for the calculation of partial melting equilibria in metabasic rocks
2020
A set of thermodynamic models is presented that, for the first time, allows partial melting equilibria to be calculated for metabasic rocks. The models consist of new activity–composition relations combined with end-member thermodynamic properties from the Holland & Powell dataset, version 6. They allow for forward modelling in the system Na (Formula presented.) O–CaO–K (Formula presented.) O–FeO–MgO–Al (Formula presented.) O (Formula presented.) –SiO (Formula presented.) –H (Formula presented.) O–TiO (Formula presented.) –Fe (Formula presented.) O (Formula presented.). In particular, new activity–composition relations are presented for silicate melt of broadly trondhjemitic–tonalitic compo…
A new ichnofauna from the Permian of the Zat Valley in the Marrakech High Atlas of Morocco
2020
Abstract A new ichnofauna from the Permian of Morocco is described in details: it is the first Palaeozoic ichnofauna from the Zat Valley in Marrakech High Atlas. The new tracksite was found in the Tighdouine region, in the middle-upper Permian of the Cham-el-Houa Siltstone Formation. An abundant and diverse ichnoassemblage composed of both protostomian (probably arthropods and annelids) traces and vertebrate tracks is recorded. The presence of protostomian burrows and traceways, associated with tetrapod tracks corresponds to the Scoyenia ichnofacies. Protostomian traces are ascribed to Diplichnites gouldi, Diplopodichnus biformis, Scoyenia cf. gracilis and Spongeliomorpha carlsbergi. Tetrap…
Reactive oxygen species formed in aqueous mixtures of secondary organic aerosols and mineral dust influencing cloud chemistry and public health in th…
2017
Mineral dust and secondary organic aerosols (SOA) account for a major fraction of atmospheric particulate matter, affecting climate, air quality and public health. How mineral dust interacts with SOA to influence cloud chemistry and public health, however, is not well understood. Here, we investigated the formation of reactive oxygen species (ROS), which are key species of atmospheric and physiological chemistry, in aqueous mixtures of SOA and mineral dust by applying electron paramagnetic resonance (EPR) spectrometry in combination with a spin-trapping technique, liquid chromatography-tandem mass spectrometry (LC-MS/MS), and a kinetic model. We found that substantial amounts of ROS includi…
Validation of a novel Multi-Gas sensor for volcanic HCl alongside H2S and SO2 at Mt. Etna
2017
Erratum to: Bull Volcanol (2017) 79: 36DOI 10.1007/s00445-017-1114-zDuring the steps of corrections, the publisher inadvertently changed the author affiliations so that they were no longer correct. The correct information is given below. The publisher regrets this mistake.; International audience; Volcanic gas emission measurements inform predictions of hazard and atmospheric impacts. For these measurements, Multi-Gas sensors provide low-cost in situ monitoring of gas composition but to date have lacked the ability to detect halogens. Here, two Multi-Gas instruments characterized passive outgassing emissions from Mt. Etna’s (Italy) three summit craters, Voragine (VOR), North-east Crater (NE…
Applying the USLE Family of Models at the Sparacia (South Italy) Experimental Site
2016
Soil erosion is a key process to understand the land degradation, and modelling of soil erosion will help to understand the process and to foresee its impacts. The applicability of the Universal Soil Loss Equation (USLE) at event scale is affected by the fact that USLE rainfall erosivity factor does not take into account runoff explicitly. USLE-M and USLE-MM, including the effect of runoff in the event rainfall– runoff erosivity factor, are characterized by a better capacity to predict event soil loss. The specific objectives of this paper were (i) to determine the suitable parameterization of USLE, USLE-M and USLE-MM by using the dataseries of Sparacia experimental site and (ii) to evaluat…
Selenium mobilization in soils due to volcanic derived acid rain: An example from Mt Etna volcano, Sicily
2011
International audience; The significant amounts of selenium (Se) emitted by volcanoes may have important impact on human health due to the narrow range between nutrition requirement and toxic effects for living organisms upon Se exposure. Although soils play a key role in determining the level in food and water and thereby human health, little is known about the behaviour of Se in volcanic soils. In this work we evaluated the Se release during rainwater–soil interaction under controlled conditions using soils collected on the flanks of Etna volcano and synthetic rain. Selenium concentrations in soil leachate solutions displayed a spatial distribution, which cannot be explained by plume depo…
Mountain building in NW Sicily from the superimposition of subsequent thrusting and folding events during Neogene: structural setting and tectonic ev…
2017
We present a 1:25.000 scale geological map of the Kumeta-Pizzuta ridge in north-western Sicily (Italy), achieved by integrating stratigraphic, structural and geophysical data. In this area, the tectonic edifice results from the piling-up of deep-water-, carbonate platform- and pelagic platform-derived tectonic units (Imerese and Sicilide, Panormide and Trapanese domains, respectively) resulting from deformations of the former southern Tethyan continental margin. The structural setting shows interference of tectonic events, different types of structural styles and different scales of deformational patterns. Early overthrust of the Imerese on the Trapanese units (since the late Serravallian) …
Short-Term Vegetation Recovery after a Grassland Fire in Lithuania: The Effects of Fire Severity, Slope Position and Aspect
2016
In Lithuania, fire is frequently used by farmers as a tool to remove dry grass, improve soil nutrient status and help soil tilling. However, little is known about the ecological impacts of these fires, including vegetation recovery. The objective of this work is to study the impacts of a spring grassland fire on vegetation recuperation on an east-facing (A) and a west-facing slope (B), considering fire severity and slope position, 10, 17, 31 and 46 days after the fire. Because of their effects on fire behaviour, aspect, steepness and heterogeneity of topography favoured higher fire severity on slope B than on slope A. Three different slope positions were identified on slope A – flat top, mi…