Search results for "Volcano"
showing 10 items of 591 documents
Mercury content and speciation in the Phlegrean Fields volcanic complex: evidence from hydrothermal system and fumaroles
2009
Abstract Mercury is outstanding among the global environmental pollutants of continuing concern. Although degassing of active volcanic areas represents an important natural source of mercury into the atmosphere, still little is known about the amount and behaviour of Hg in volcanic aquifers, especially regarding its chemical speciation. In order to assess the importance of mercury emissions from active volcanoes, thermal waters were sampled in the area surrounding La Solfatara, Pozzuoli bay. This is the most active zone of the Phlegrean Fields complex (coastal area north–west of Naples), with intense hydrothermal activity at present day. Studied groundwaters show total Hg (THg) concentratio…
Magma Degassing at Piton de la Fournaise Volcano
2015
Since about 1860 AD, magmatic gas release at Piton de la Fournaise volcano is very weak during intra-eruptive phases and essentially occurs during the relatively short-lived eruptions. Recent gas measurements performed during an eruption in October 2010, combined with detailed review of melt and fluid inclusion composition in magmas erupted over the past 50 kyrs, indicate that most PdF eruptions extrude magmas having variably degassed at shallow depth (P 1 kbar) and the shallow magmas, whose fluids are efficiently scrubbed by the hydrothermal system and the water table. Quantification of SO2 fluxes permits to track syn-eruptive magma ascent at shallow level (above sea level). Deeper exsolut…
Mineralogical variability of Callovo-Oxfordian clays from the Paris Basin and the Subalpine Basin.
2006
High-resolution clay mineralogical data at the Middle/Upper Jurassic boundary from the French Subalpine Basin, the Jura Mountains and the Paris Basin (ANDRA boreholes) from Callovo-Oxfordian clayey deposits allow spatial and temporal terrigenous flux evolution to be considered over a period of 6 to 7 Myr. Recorded diachronisms of major mineralogical changes and complex clays distribution at the Paris Basin scale result to combined palaeogeographic/eustatic variations and climate input. In the French Subalpine Basin, mineralogical homogeneity confirms the burial diagenesis influence, but other terrigenous supplies must be involved in contrast to the Paris Basin domains. Volcanogenic clays (b…
Possible impacts of volcanic ash emissions of Mount Etna on the primary productivity in the oligotrophic Mediterranean Sea: Results from nutrient-rel…
2013
Atmospheric deposition of volcanic ash has recently been recognized as an important nutrient source into the surface ocean. Mount Etna (Italy), one of the world's most active volcanoes, is located in the oligotrophic Mediterranean Sea (MedSea). Despite the active volcanism on Mount Etna, the biogeochemical impacts of volcanic ash fallouts on the marine primary productivity (MPP) remain largely unknown. Here we present the results of seawater nutrient release experiments with volcanic ash samples from Mount Etna that have been collected during different eruptive episodes between 2001 and 2007. Our results show that volcanic ash from Mount Etna releases significant amounts of fixed-N (35-855 …
Plants as biomonitors for volcanic emissions
2014
Biomonitoring techniques have been widely used in environmental studies to monitor anthropogenic pollutant. Recently such techniques have been applied also to ascertain the impact of contaminants naturally released by volcanic activity. In the present study a biomonitoring surveys has been performed in many different active volcanic systems: Mt. Etna and Vulcano (Italy), Nisyros (Greece), Nyiragongo (DRC), Masaya (Nicaragua), Gorely (Kamchatka, Russia). We sampled leaves of different species Betulla aethnensis, Pinus nigra, Populus tremula, Senecio aethnensis and Rumex aethnensis on Etna, Cistus creticus and salvifolius on Vulcano and Nisyros, Senecio ssp. on Nyiragongo, a Fern on Masaya an…
Origin of potassic postcollisional volcanic rocks in young, shallow, blueschist-rich lithosphere
2020
Unusually high Th/La in K-rich orogenic rocks may indicate shallow blueschist-rich sources in accretionary settings.
GEOLOGIA DE LAS MARGENES DE LA PLACA DEL CARIBE: GENERALIDADES EN GUATEMALA, COSTA RICA, LA ESPAÑOLA Y RESULTADOS PRELIMINARES DEL ANALISIS DE UNA TR…
2011
The Caribbean Plate margins are constituted by deformed belts built up since the Cretaceous in acompressional and strike-slip stress field, which allowed overthrusting of the Caribbean crust onto the Pacific,North and South American Plates.The Caribbean borders include Jurassic-Cretaceous ophiolitic units (Great Antilles, Venezuela, Costa Rica,Guatemala, etc.), composed by mantle peridotites, gabbros, volcanic and sedimentary covers, which have beendeformed in at least two ductile penetrative phases and were often metamorphosed in the prehnite-pumpelleyite,green and blue schist, amphibolite, and in places eclogite facies. These units may present part of a subductioncomplex or are an accreti…
Degassing at the Volcanic/Geothermal System of Kos (Greece): Geochemical Characterization of the Released Gases and CO2 Output Estimation
2019
Forty-five gas samples have been collected from natural gas manifestations at the island of Kos—the majority of which are found underwater along the southern coast of the island. On land, two anomalous degassing areas have been recognized. These areas are mainly characterized by the lack of vegetation and after long dry periods by the presence of sulfate salt efflorescence. Carbon dioxide is the prevailing gas species (ranging from 88 to 99%), while minor amounts of N2 (up to 7.5%) and CH4 (up to 2.1%) are also present. Significant contents of H2 (up to 0.2%) and H2S (up to 0.3%) are found in the on-land manifestations. Only one of the underwater manifestations is generally rich in N2 (up t…
Shrinkage Bubbles: The C–O–H–S Magmatic Fluid System at San Cristóbal Volcano
2018
New analytical results for the composition of shrinkage bubbles (09-70 vol. %) in olivine-hosted (Fo <80%) primary melt inclusions (MIs) have been incorporated into a novel geochemical model for San Cristó bal volcano, Nicaragua. The vapour, liquid, and mineral components found inside shrinkage bubbles may represent relics of early C-O-H-S fluids exsolved from a magmatichydrothermal system. This conclusion is supported by high-resolution Raman microspectroscopy revealing: (1) gaseous CO2 (d=0·17-0·31 g/cm3 in 31 samples) coexisting with liquid H2O (in seven samples) at ambient temperature (<22°C) inside the shrinkage bubbles of naturally quenched inclusions; (2) several mineral phases (i.e.…
The geological CO2degassing history of a long-lived caldera
2015
The majority of the ~100 Holocene calderas on Earth host vigorously active hydrothermal systems, the heat and volatile budgets of which are sustained by degassing of deeply stored magma. Calderas may thus contribute a nontrivial, although poorly quantified, fraction of the global budget of magmatic volatiles such as CO2. Here we use original isotopic a d petrological results from Campi Flegrei volcano, Italy, to propose that hydrothermal calcites are natural mineral archives for the magmatic CO2 that reacted with reservoir rocks during the geological history of a caldera. We show that Campi Flegrei calcites, identified in core samples extracted from 3-km-deep geothermal wells, formed at iso…