Search results for "Melt Inclusion"
showing 10 items of 34 documents
Volatile dilution during magma injections and implications for volcano explosivity
2016
Magma reservoirs underneath volcanoes grow through episodic emplacement of magma batches. These pulsed magma injections can substantially alter the physical state of the resident magma by changing its temperature, pressure, composition, and volatile content. Here we examine plagioclase phenocrysts in pumice from the 2014 Plinian eruption of Kelud (Indonesia) that record the progressive capture of small melt inclusions within concentric growth zones during crystallization inside a magma reservoir. High-spatial-resolution Raman spectroscopic measurements reveal the concentration of dissolved H2O within the melt inclusions, and provide insights into melt-volatile behavior at the single crystal…
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…
Melt inclusions track changes in chemistry and oxidation state of Etnean magmas
2017
Mount Etna (Italy) is a stratovolcano, located near the convergent boundary between African and European plates. Since its appearance, it was characterized by continuous variability of eruptive style and magma composition, though more subtle. Currently, its volcanic activity consists of effusive and explosive eruptions marked by high gas fluxes. Olivine hosted melt inclusions (MIs), belonging to products of the last 15 ky, were analysed for their chemical composition, volatiles contents and Fe speciation, in order to interpret the chemical variability and to evaluate the oxidation state of Etnean magmas and its eventual evolution. Olivine phenocrysts were selected from the most primitive Fa…
Volatiles and trace elements content in melt inclusions from the zoned Green Tuff ignimbrite (Pantelleria, Sicily): petrological inferences
2018
International audience; The island of Pantelleria is one of the best known localities of bimodal mafic-felsic magmatism (alkali basalt and trachyte-pantellerite). Among the felsic rocks, the coexistence in a single eruption of products of both trachyte and pantellerite compositions is limited to few occurrences, the Green Tuff (GT) ignimbrite being one of these. The GT is compositionally zoned from pantellerite (70.1 wt% SiO2, mol Na+K/Al = 1.86, 1871 ppm Zr) at the base to crystal-rich (>30 vol%) comenditic trachyte (63.4 wt% SiO2, mol Na+K/Al = 1.10, 265 ppm Zr) at the top, although the pantellertic compositions dominate the erupted volume. We present here new data on melt inclusions (MIs…
In situ quantification of the nitrogen content of olivine-hosted melt inclusions from Klyuchevskoy volcano (Kamchatka): Implications for nitrogen rec…
2021
International audience; Assessing the N content of arc magmas and their mantle source remains a challenge because the volatile element composition of melts and gases can be modified during magma ascent, storage, and eruption. Given that melt inclusions (MIs) in Mg-rich olivine represent the best proxies for primary arc melts, we applied, for the first time, an in situ high-resolution secondary ion mass spectrometry (SIMS) method to determine the N concentration in olivine-hosted MIs from Klyuchevskoy volcano in Kamchatka. To reverse the effects of post-entrapment modification processes (i.e., exsolution of volatiles into a fluid bubble), the MIs were partially to completely homogenized at h…
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…
A Raman calibration for the quantification of SO42-groups dissolved in silicate glasses: Application to natural melt inclusions
2017
Sulfur is an important volatile element involved in magmatic systems. Its quantification in silicate glasses relies on state-of-the-art techniques such as electronprobe microanalyses (EPMA) or X-ray absorption spectroscopy but is often complicated by the fact that S dissolved in silicate glasses can adopt several oxidation states (S6+for sulfates or S2-for sulfides). In the present work, we use micro-Raman spectroscopy on a series of silicate glasses to quantify the S content. The database is constituted by 47 silicate glasses of various compositions (natural and synthetic) with S content ranging from 1179 to 13 180 ppm. Most of the investigated glasses have been synthesized at high pressur…
Degassing vs. eruptive styles at Mt. Etna volcano (Sicily, Italy). Part I: Volatile stocking, gas fluxing, and the shift from low-energy to highly ex…
2018
International audience; Basaltic magmas can transport and release large amounts of volatiles into the atmosphere, especially in subduction zones, where slab-derived fluids enrich the mantle wedge. Depending on magma volatile content, basaltic volcanoes thus display a wide spectrum of eruptive styles, from common Strombolian-type activity to Plinian events. Mt. Etna, in Sicily, is a typical basaltic volcano where the volatile control on such a variable activity can be investigated. Based on a melt inclusion study in products from Strombolian or lava-fountain activity to Plinian eruptions, here we show that for the same initial volatile content, different eruptive styles reflect variable dega…
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…