Search results for "volcan"
showing 10 items of 899 documents
Trace elements in Mirror of Venus lake waters (Pantelleria Island, Italy)
2016
Mirror of Venus lake (MV) is a small (1.5 km2) endorheic alkaline lake located in a calderic depression on the northern side of Pantelleria Island (South Italy), a quiescent Pleistocenic stratovolcano located in the NW-SE trending continental rift developed between North Africa and Sicily. The lake, sub-squared in shape (around ca 450 m long and ca 350 m wide and 13 m depth) water input contribution is essentially from the thermal springs situated on its shores (Q = 0.1 l.s-1) and from meteoric waters. A total volume of 580.000 m3 has been estimated in June 2014. CO2 flux measurements made with a floating accumulation chamber in 2014 on the MV surface (both diffusive and bubbling CO2) highl…
Anaplastic Thyroid Cancer in Sicily: The Role of Environmental Characteristics
2017
Background: Anaplastic thyroid cancer (ATC) is a rare but extremely aggressive cancer of the thyroid, contributing up to 30-40% of thyroid cancer-specific mortality. We analyzed ATC characteristics and survival rates in Sicily to evaluate the possible influence of environmental factors. With this aim data regarding ATC incidences in urban/rural and industrial, iodine deficient and volcanic vs. control areas were compared in Sicily as well as ATC data from Sicily and USA. Methods: Using the Sicilian Register of Thyroid Cancer (SRTC) database incidence, age, gender, tumor size and histotype, extrathyroidal extension, stage and coexistence with pre-existing differentiated thyroid cancer (DTC) …
Patterns and origin of igneous activity around the Tanzanian craton
2012
Abstract Tertiary and later igneous activity is common on and around the Tanzanian craton, with primitive magma compositions ranging from kimberlites and varieties of picrites through nephelinites, basanites and alkali basalts. This review focuses on elucidating the conditions of origin of the melts, addressing the question of the state and involvement of the Tanzanian cratonic lithosphere in magma genesis. The Tanzanian craton is anomalous with a surface elevation of >1100 m reflecting buoyancy supported by a subcratonic plume whose effects are seen in the volcanics of both western and eastern rift branches. Magmatism on the craton and at its edge has high K/Na and primitive melts show fra…
Temporal–spatial evolution of low-SiO2 volcanism in the Pleistocene West Eifel volcanic field (West Germany) and relationship to upwelling asthenosph…
2015
Abstract The temporal–spatial evolution of low-SiO 2 lavas from the Pleistocene West Eifel volcanic field (Central European Volcanic Province) and linked petrogenetic variations are evaluated using 40 Ar/ 39 Ar age and geochemical data. Geochronological and petrological evidence is related to the physical structure of the previously established seismologically anomalous asthenosphere interpreted as thermally upwelling mantle (Eifel Plume). Lava flows >480 ka (Middle Pleistocene) occur exclusively in the NW of the volcanic field. After a time span of ca. 400 ka lacking significant activity, volcanism has migrated to the SE generating flows At melting depth >70 km of parental asthenospheric m…
Carbon concentration increases with depth of melting in Earth’s upper mantle
2021
Carbon in the upper mantle controls incipient melting of carbonated peridotite and so acts as a critical driver of plate tectonics. The carbon-rich melts that form control the rate of volatile outflux from the Earth’s interior, contributing to climate evolution over geological times. However, attempts to constrain the carbon concentrations of the mantle source beneath oceanic islands and continental rifts is complicated by pre-eruptive volatile loss from magmas. Here, we compile literature data on magmatic gases, as a surface expression of the pre-eruptive volatile loss, from 12 oceanic island and continental rift volcanoes. We find that the levels of carbon enrichment in magmatic gases cor…
Highly siderophile elements (PGE, Re and Au) in mantle xenoliths from the West Eifel volcanic field (Germany)
2003
Abstract Mantle peridotite xenoliths ranging in modal composition between fertile lherzolites and modally metasomatized harzburgites, and magmatic pyroxenite xenoliths from the West Eifel and Vogelsberg volcanic fields (Germany) have been analyzed for their whole rock major and minor elements, six platinum-group elements PGE (PGE: Os, Ir, Pt, Ru, Rh, Pd), Re and Au, rare earth elements (REE), and several other trace elements (e.g., As, Ta). The bulk rock Ir concentrations range from 0.23 to 9.07 ng/g (total PGE contents range between 43.2 ng/g), exceeding the range previously found in mantle rocks. Two pyroxenite samples show large variabilities in their PGE concentrations, with Ir contents…
Geodynamic Setting of the Tertiary Hocheifel Volcanism (Germany), Part II: Geochemistry and Sr, Nd and Pb Isotopic Compositions.
2007
Major and trace element as well as isotopic compositions on 26 volcanic rocks from the Tertiary Hocheifel volcanic field and for comparison from Upper Rhine Graben occurrences (western Central European Volcanic Province) were measured in order to provide geochemical evidence for the geodynamic setting of the Tertiary Eifel volcanism. Except for a few differentiated lavas there are mainly basanitic compositions. These rocks were produced by low degree partial melting of a previously metasomatized garnet peridotite source at pressures and temperatures corresponding to depths of about 75 to 90 km. In contrast to the differentiated lavas, most of the basanites are not significantly affected by …
Petrogenesis of strongly alkaline primitive volcanic rocks at the propagating tip of the western branch of the East African Rift
2009
Abstract Strongly silica-undersaturated potassic lavas (kamafugites) and carbonatitic tuffs are characteristic of the Toro-Ankole volcanic field in southwestern Uganda, forming the youngest and most northward volcanics of the western branch of the East African Rift. Lavas contain exceptionally low SiO2 (31.8–42.8 wt.%), high CaO (up to 16.6 wt.%) and K2O (up to 7 wt.%). They exhibit moderately enriched correlated Nd (eNd − 0.1 to − 4.7) and Hf (eHf − 0.1 to − 8.8) isotope signatures, indicating time-integrated enrichment in incompatible elements in the source, attributed to mixing between two metasomatic assemblages, a phlogopite-rich MARID-type and a later carbonate-rich assemblage. The re…
The fate of subducted oceanic slabs in the shallow mantle: Insights from boron isotopes and light element composition of metasomatized blueschists fr…
2012
Abstract Serpentine muds from South Chamorro Seamount (SCS), drilled during ODP Leg 195 at Site 1200 contain metamafic clasts that experienced blueschist-facies metamorphism (including the critical mineral assemblage pumpellyite – Na-amphibole – epidote). These schists represent fragments from the actual slab–mantle interface at ~ 27 km depth. Their heterogeneous lithology with a metasomatic character indicates significant mobility of major elements in the Mariana forearc, a region of melange formation as it can also be observed in onland exposures such as the Catalina Schist. As the Mariana forearc blueschists show no late stage alteration they permit the direct study of material transfer …
First measurements of magmatic gas composition and fluxes during an eruption (October 2010) of Piton de la Fournaise hot spot volcano, La reunion isl…
2011
Piton de la Fournaise (PdF), in the western Indian Ocean, is a very active hot spot basaltic volcano, with 1-2 fissure eruptions per year on average. Its magmas have been widely studied and its eruptions are well anticipated by the local seismic-geodetic monitoring network. However, no datum was yet available for its magmatic gas emissions (restricted to only eruptive phases and hardly accessible). Here we report on the first measurements of the chemical composition and mass flux of magmatic gases emitted during a PdF eruption in October 2010. Hot gases arising from different eruptive vents were remotely measured with OP-FTIR spectroscopy, using molten lava fragments as IR radiation source,…