Search results for " melt inclusions"
showing 8 items of 8 documents
Melt inclusions track melt evolution and degassing of Etnean magmas in the last 15 ka
2019
We present major elements compositions and volatiles contents of olivine-hosted melt inclusions from Etna volcano (Italy), which extend the existing database with the aim of interpreting the chemical variability of Etnean magmas over the last 15 ka. Olivine phenocrysts were selected from the most primitive Fall Stratified (FS) eruptive products of picritic composition (Mg# = 67–70, Fo 89–91 ), the Mt. Spagnolo eccentric lavas (Mg# = 52–64, Fo 82–88 ) and among the more recent 2002–2013 eruptive products (Mg# = 33–53, Fo 68–83 ). Crystal fractionation and degassing processes were modeled at temperatures of 1050–1300 °C, pressures <500 MPa, and oxygen fugacity between 1 and 2 log units abo…
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.…
Le comportement du soufre et les conditions d'oxydoréduction dans les basaltes hydratés de l'Etna inférés par des inclusions vitreuses et des verres …
2017
Sulfur is an important volatile component of magmas that presents different oxidation states, depending on the redox conditions and on the phase of occurrence: in silicate melts it is typically dissolved as S⁶⁺ and/or S²⁻ , in the gas phase it occurs principally as SO₂ (S⁴⁺ ) and H₂S (S²⁻). Mount Etna, in which magmatic redox conditions are poorly constrained, is used as a case study to investigate sulfur behavior in hydrous basaltic magmas during magma differentiation and degassing. This research integrates the study of natural olivine-hosted melt inclusions with an experimental study on S solubility in hydrous alkali basalts at magmatic conditions.Experimental results suggest the importan…
Volatiles in pantellerite magmas: A case study of the Green Tuff Plinian eruption (Island of Pantelleria, Italy)
2013
Abstract The Green Tuff (GT) Plinian eruption, the largest in magnitude at Pantelleria, erupted 3 to 7 km3 DRE of pantellerite magma and a small volume of trachyte. Fifty-nine anorthoclase-hosted melt inclusions from the two basal pumice members were analyzed by FT-IR spectroscopy in order to assess the pre-eruptive H2O content in the pantellerite melt. Microanalytical methods were used to determine major element, Cl, F and S contents. Melt inclusions and glassy groundmasses have a nearly homogeneous pantelleritic composition (peralkaline index = 1.9-2.2) and variable water contents ranging from 1.4 to as high as 4.2 wt %, i.e. much higher than the 1.4 wt % of earlier published studies. The…
Volatile contents of mafic-to-intermediate magmas at San Cristóbal volcano in Nicaragua
2017
San Cristóbal volcano in northwest Nicaragua is one of the most active basaltic–andesitic stratovolcanoes of the Central American Volcanic Arc (CAVA). Here we provide novel constraints on the volcano's magmatic plumbing system, by presenting the first direct measurements of major volatile contents in mafic-to-intermediate glass inclusions from Holocene and historic-present volcanic activity. Olivine-hosted (forsterite [Fo] < 80; Fo< 80) glass inclusions from Holocene tephra layers contain moderate amounts of H2O (0.1–3.3 wt%) and S and Cl up to 2500 μg/g, and define the mafic (basaltic) endmember component. Historic-present scoriae and tephra layers exhibit more-evolved olivines (Fo69…
Evidence of Two-Component Iblean-Like Mantle From 2001-2006 Igneous Products of Mount Etna
2008
EVIDENCES OF ENRICHED MANTLE (EM-2) SOURCE CONTRIBUTION TO ETNEAN MAGMAS: A COMPREHENSIVE STUDY ON FLUID AND MELT INCLUSIONS OF 2001-2006 ERUPTIONS
2009
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…