Search results for "volcan"
showing 10 items of 899 documents
Zircon evaporation ages and geochemistry of metamorphosed volcanic rocks from the Vinjamuru domain, Krishna Province: evidence for 1.78 Ga convergent…
2012
Palaeoproterozoic intermediate to potassic felsic volcanism in volcano-sedimentary sequences could either have occurred in continental rift or at convergent magmatic arc tectonic settings. The Vinjamuru domain of the Krishna Province in Andhra Pradesh, SE India, contains such felsic and intermediate metavolcanic rocks, whose geochemistry constrains their probable tectonic setting and which were dated by the zircon Pb evaporation method in order to constrain their time of formation. These rocks consist of interlayered quartz–garnet–biotite schist, quartz–hematite–baryte–sericite schist as well as cherty quartzite, and represent a calc-alkaline volcanic sequence of andesitic to rhyolitic rock…
Isotopic constraints on the age and formation of a Palaeoproterozoic volcanic arc complex in the Kedougou Inlier, eastern Senegal, West Africa
1997
Abstract The Palaeoproterozoic Kedougou basement in the Mako area in eastern Senegal consists of four major rock complexes: 1) high-grade amphibolitic and gneissic rocks occuring as large xenoliths (the Sandikounda amphibolite-gneiss complex); 2) voluminous bimodal volcanic rocks (the Mako volcanic-plutonic complex); 3) the Sandikounda layered plutonic complex; and 4) trondhjemitic to calc-alkaline intrusive granitoids (the Laminia-Kaourou plutonic complex). Zircons from xenoliths of the Sandikounda amphibolite-gneiss complex yielded ages of ∼2200 Ma, which are slightly older than those of the Mako Supergroup volcanic rocks. These xenoliths also have ɛNd(t) values ranging from +2.4 to +4.1.…
UV camera measurements of fumarole field degassing (La Fossa crater, Vulcano Island)
2011
Abstract The UV camera is becoming an important new tool in the armory of volcano geochemists to derive high time resolution SO2 flux measurements. Furthermore, the high camera spatial resolution is particularly useful for exploring multiple-source SO2 gas emissions, for instance the composite fumarolic systems topping most quiescent volcanoes. Here, we report on the first SO2 flux measurements from individual fumaroles of the fumarolic field of La Fossa crater (Vulcano Island, Aeolian Island), which we performed using a UV camera in two field campaigns: in November 12, 2009 and February 4, 2010. We derived ~ 0.5 Hz SO2 flux time-series finding fluxes from individual fumaroles, ranging from…
Thermal anomalies in fumaroles at Vulcano island (Italy) and their relationship with seismic activity
2013
Abstract Fumarole thermal monitoring is a useful tool in the evaluation of volcanic activity, since temperatures strongly relate to the upward flux of magmatic volatiles. Once depurated from meteorological noise, their variations can reflect permeability changes due to crustal stress dynamics eventually associated to seismic activity. In this work, we discuss a fumarole temperature record acquired in the period September 2009–May 2012 at Vulcano island (Italy), during which changes of volcanic state, local seismic activity and teleseisms occurred. Apart from positive thermal anomalies driven by increments in volcanic activity, we observed 3 episodes at least of concurrence between tectonic …
Devonian to Permian plate tectonic cycle of the Paleo-Tethys Orogen in southwest China (I): Geochemistry of ophiolites, arc/back-arc assemblages and …
2009
Abstract The Paleo-Tethys Orogen in southwest China is an amalgamation of continental terranes (Sibumasu, Simao and Yangtze), which are bounded by ophiolite belts (Ailaoshan, Jinshajiang and Changning–Menglian) that represent former ocean basins. This study concentrates on ophiolites, arc/back-arc assemblages, and within-plate igneous rocks that occur in this complex orogen. Mainly based on geochemical fingerprinting of basalts, the Paleo-Tethys ophiolites are here classified as MORB and SSZ types. The Ailaoshan ophiolite (NMORB-type; ca. 387–374 Ma) is associated with a non-volcanic segment of the rifted western Yangtze margin. The Jinshajiang ophiolite (EMORB-type; 346–341 Ma), which has …
Fluorine speciation in topsoils of three active volcanoes of Sicily (Italy)
2008
Fluorine is one of the many environmental harmful elements released by volcanic activity. The content of total oxalate-extractable and water-extractable fluorine was determined in 96 topsoils of three active volcanic systems of southern Italy (Mt Etna, Stromboli and Vulcano). Total fluorine (F) content (F TOT) ranges from 112 to 7,430 mg kg−1, F extracted with oxalate (F OX) ranges from 16 to 2,320 mg kg−1 (2–93% of F TOT) and F extracted with distilled water ( $$ F_{{{\text{H}}_{{\text{2}}} {\text{O}}}} $$ ) ranges from 1.7 to 159 mg kg−1 (0.2–40 % of F TOT). Fluorine in the sampled topsoils derives both from the weathering of volcanic rocks and ashes and from the enhanced deposition due t…
A christmas gift: Signature of the 24th December 2018 eruption of Mt. Etna on the chemical composition of bulk deposition in eastern sicily
2020
The eruption of Mt. Etna which occurred on December 24th 2018 was characterized by strombolian activity and fire fountains, emitted by the New South-East Crater and along a fissure that propagated towards the SE. The influence of volcanic emissions on atmospheric deposition was clearly detectable at several kilometres from the source. Wet and dry (bulk) deposition samples were collected each month, through a network of eleven collectors, in the areas of Milazzo, and Priolo between June 2018 and June 2019. They were analysed for major ions and trace elements concentrations. The pH values range from 3.9 to 8.3, while the EC values range from 7 to 396 μS cm-1. An extensive neutralization of th…
Magmatic degassing of multicomponent vapors and assessment of magma depth: application to Vulcano Island (Italy)
2001
Degassing of magmatic H2O, CO2 and rare gases plays a major role in understanding large-scale Earth processes and in the assessment of volcanic activity. Here we describe a quantitative model for magmatic degassing of H2O–CO2–noble gas–N2 mixtures. Our modeling takes into account non-ideal behaviors by adopting recently developed approaches for the solubility of H2O–CO2 mixtures in silicate liquids and for noble gas partitioning in H2O–CO2 bearing magmas. This new approach allows quantitative treatment of inert gas fractionation throughout the degassing of any H2O–CO2 bearing natural magma in a wide range of thermo-baric conditions. Magma degassing simulations performed by our model have cl…
Stratigraphy, geochemistry and geochronology of a Quaternary pyroclastic sequence of the Chichontepec volcano, El Salvador
2013
In this paper we present sedimentological, chemical and geochronological data on a pyroclasticsequence deposited at Chichontepeque Volcano (El Salvador) during a caldera-forming Plinian phase.Granulometric analyses and width distribution patterns of airfall pyroclastics showed that these are the result ofat least two eruptions, the oldest being the more complete. The Basal Fall, which marks the beginning of thePlinian eruption, shows the typical features of Plinian air-fall deposits.Chemical trends mirror roughly a downward tapping from a zoned magma chamber; inside each fall unit crys-tal fractionation trends can be recognized. 39Ar/40Ar dating of lavas underlying and overlying the pyrocla…
Anomalous magmatic degassing prior to the 5th April 2003 paroxysm on Stromboli
2004
[1] A major explosion occurred at Stromboli on April 5 2003, being the most powerful event over a period of exceptional eruptive activity lasting from December to July. Here, we describe results from a network of diffusive tubes set up on the Stromboli's summit area, aimed at a characterisation of plume composition (SO2, HCl, HF) prior to and after April 5. Data analysis revealed anomalous sulphur degassing 2–3 days before the event, when SO2/HCl ratios (≈9) significantly higher than those typical of quiescent degassing (≈1) were recorded. We interpret this exceptional plume signature as an evidence of S-rich magmas ascending in the shallow plumbing system, and propose high SO2/HCl as a pot…