Search results for "Petrologia"

Primo contributo sui depositi a Terra Rossa dell'Abisso del Vento, Isnello (PA).

2007

Generation of CO2-rich melts during basalt magma ascent and degassing

2013

International audience; To test mechanisms of basaltic ma gma degassing, continuous decompressions of volatile-bearing (2.7-3.8 wt% H2O, 600-1300 ppm CO2) Stromboli melts were performed from 250-200 to 50-25 MPa at 1180-1140°C. Ascent rates were varied from 0.25 to ~ 1.5 m/s. Glasses after decompression show a wide range of textures, from totally bubble-free to bubble-rich, the latter with bubble number densities from 104 to 106/cm3, similar to Stromboli pumices. Vesicularities range from 0 to ~ 20 vol%. Final melt H2O concentrations are homogeneous and always close to solubilities. In contrast, the rate of vesiculation controls the final melt CO2 concentration. High vesicularity charges ha…

PETROLOGICAL AND EXPERIMENTAL CONSTRAINTS ON THE PRE-ERUPTIVE CONDITIONS OF LA SOMMATA BASALT AND BROWN TUFFS TEPHRA (AEOLIAN ISLANDS)

2011

This work is focused on two key eruptions of Vulcano Island: 1) the most primitive magma of Vulcano erupted by the La Sommata scoria cone, a silica-undersaturated Ca-rich shoshonitic basalt with olivine-hosted primitive melt inclusions having an ultra-calcic character; 2) the most energetic eruptions of the whole Aeolian Archipelago, the Brown Tuffs (BT) eruptions, which produced several pyroclastic deposits, covering an ample age interval, spread out over a large portion of all Aeolian islands up to the northern coast of Sicily (Lucchi et al., 2008). By complementary studies of melt inclusions and experimental petrology, we pursued the following main objectives: (i) to constrain the pressu…

Seeking the mantle source and storage system of carbonatite magmas: case studies from Fuerteventura (Canary Islands) and Mt. Vulture volcano (souther…

Carbonatite magmatism is mainly associated with intraplate continental tectonic settings, with a temporal distribution from Archean to the present. The growing number of carbonatite occurrences from unconventional tectonic settings, such as oceanic contexts (e.g., Carnevale et al., 2021) or subduction zones (e.g., D’Orazio et al., 2007), received considerable attention during last two decades, given their importance as source of rare elements, and, most importantly, because they provide meaningful information about the geochemical cycle of carbon and mantle metasomatism as well. This work shows how the study of fluids trapped within minerals from carbonatites and carbonatite magmas can prov…

Melt inclusions constrain S behaviour and redox conditions in Etnean magmas

2016

Mount Etna is a complex magmatic system characterized by a continuous variability both in terms of eruptive style and composition of erupted products. Currently, its volcanic activity is marked by high gas fluxes (of above all SO2), both during eruptive and non-eruptive periods. In this study, we have studied the volatile contents and Fe speciation of olivine-hosted melt inclusions from 6 eruptions of the last 15 ky, mainly to investigate the behaviour of S during ascent and differentiation of Etnean magmas. Samples selected come from the FS eruption which is the oldest and most primitive (picritic composition, Fo91), the Mt Spagnolo and from more recent eruptions: 2002/3, 2006, 2008, and 2…

The role of melt composition on aqueous fluid vs. silicate melt partitioning of bromine in magmas

2018

International audience; Volcanogenic halogens, in particular bromine, potentially play an important role in the ozone depletion of the atmosphere. Understanding bromine behaviour in magmas is therefore crucial to properly evaluate the contribution of volcanic eruptions to atmospheric chemistry and their environmental impact. To date, bromine partitioning between silicate melts and the gas phase is very poorly constrained, with the only relevant experimental studies limited to investigation of synthetic melt with silicic compositions. In this study, fluid/melt partitioning experiments were performed using natural silicate glasses with mafic, intermediate and silicic compositions. For each co…

Experimental Crystallization of a High-K Arc Basalt: the Golden Pumice, Stromboli Volcano (Italy)

2006

International audience; The near-liquidus crystallization of a high-K basalt (PST-9 golden pumice, 49·4 wt % SiO2, 1·85 wt % K2O, 7·96 wt % MgO) from the present-day activity of Stromboli (Aeolian Islands, Italy) has been experimentally investigated between 1050 and 1175°C, at pressures from 50 to 400 MPa, for melt H2O concentrations between 1·2 and 5·5 wt % and {Delta}NNO ranging from –0·07 to +2·32. A drop-quench device was systematically used. AuPd alloys were used as containers in most cases, resulting in an average Fe loss of 13% for the 34 charges studied. Major crystallizing phases include clinopyroxene, olivine and plagioclase. Fe–Ti oxide was encountered in a few charges. Clinopyro…

Microthermometry of fluid inclusions in calcite from Fuerteventura carbonatites: composition and formation conditions

2022

The petrographic analysis in calcite minerals in carbonatitic dykes from Fuerteventura Basal Complex (Ajuy, Punta de la Nao) shows the presence of isolated primary fluid inclusions, corroborating their magmatic origin instead of a late-stage origin. Micro-thermometric studies in calcite show a restricted range of apparent eutectic temperature (Te*= -21.7 – -21.0 °C) and final ice melting temperatures (Tim= -3.2 – -2.1. °C). Homogenization temperatures and pressures are in the range of 140-210 °C and 4-16 bars respectively. Our results suggest the binary NaCl-H2O system as a characterizing chemical system in studied fluid inclusions, with the presence of low salinity fluids (≈ 5 wt. % NaCleq…

Clinopyroxene-bearing garnet amphibolites from the Ferrà valley (northern Peloritani Mts., Sicily

2001

The fumarolic CO2 output from Pico do Fogo volcano (Cape Verde)

2020

The Pico do Fogo volcano, in the Cape Verde Archipelago off the western coasts of Africa, has been the most active volcano in the Macaronesia region in the Central Atlantic, with at least 27 eruptions during the last 500 years. Between eruptions fumarolic activity has been persisting in its summit crater, but limited information exists for the chemistry and output of these gas emissions. Here, we use the results acquired during a field survey in February 2019 to quantify the quiescent summit fumaroles' volatile output for the first time. By combining measurements of the fumarole compositions (using both a portable Multi-GAS and direct sampling of the hottest fumarole) and of the SO2 flux (u…