scholarly journals Magma storage beneath Grímsvötn volcano, Iceland, constrained by clinopyroxene-melt thermobarometry and volatiles in melt inclusions and groundmass glass

2017 ◽  
Vol 122 (9) ◽  
pp. 6984-6997
Author(s):  
B. Haddadi ◽  
O. Sigmarsson ◽  
G. Larsen
Keyword(s):  
Melt Inclusions ◽  
Magma Storage ◽  
Groundmass Glass

scholarly journals Hydrogen Isotopic Variations in the Shergottites

Geosciences ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 148 ◽  
Author(s):  
Shuai Wang ◽  
Sen Hu
Keyword(s):  
Melt Inclusions ◽  
Crustal Rock ◽  
Evidence Based ◽  
Mantle Rock ◽  
Future Studies ◽  
Groundmass Glass ◽  
Impact Melt ◽  
Melt Glass ◽  
Isotopic Variations

Hydrogen isotopes in the shergottite Martian meteorites are among the most varied in Mars laboratory samples. By collating results of previous studies on major hydroxyl, deuterium, and H2O bearing phases, we provide a compendium of recent measurements in order to elucidate crustal-rock versus mantle-rock processes on Mars. We summarize recent works on volatile and δD measurements in a range of shergottite phases: from melt inclusions, apatite, merrillite, maskelynite, impact melt glass, groundmass glass, and nominal anhydrous minerals. We interpret these observations using an evidence-based approach, considering two particular scenarios: (1) water-rock crustal interactions versus (2) magmatic-based processes. We consider the implications of these measurements and the scope they have for future studies, paying particular attention to future works on H, S, and Cl isotopes in situ, shedding light on the nature of volatiles in the hydrosphere and lithosphere of Mars.

scholarly journals Dominica: transcrustal magmatic system and eruptive halogen budgets

2020 ◽  
Author(s):  
Thiebaut d'Augustin ◽  
Hélène Balcone-Boissard ◽  
Georges Boudon ◽  
Caroline Martel ◽  
Etienne Deloule ◽  
...  
Keyword(s):  
Melt Inclusions ◽  
Storage Conditions ◽  
Explosive Eruptions ◽  
Magma Storage ◽  
Equilibrium Data ◽  
Order Of Magnitude ◽  
First Time ◽  
Magma Storage Conditions ◽  
Degassing Budget

<p>Dominica island experienced the largest explosive eruptions (ignimbrites) of the Lesser Antilles arc. The recent revised chronostratigraphy of the Morne Trois Pitons – Micotrin eruptive activity evidenced a series of plinian eruptions that occurred between 18 ka and 9 ka BP. Here we focus on these recent eruptions in order to determine the magma storage conditions at depth and volatile degassing budget. Volatile concentrations (H<sub>2</sub>O, CO<sub>2</sub>) in melt inclusions indicate storage conditions of 200 MPa (~6-8 km deep) and 860-880°C in agreement with experimental constraints from phase-equilibrium data. The magmas were thus stored shallower than those involved during the ignimbritic eruptions (~16 km deep). Magma composition and halogen ratios suggest a common magma origin for all eruptions of Morne Trois Pitons Micotrin volcano in the last 60 kyrs. In addition, for the first time, a complete degassing budget including H<sub>2</sub>O, CO<sub>2</sub>, SO<sub>2</sub>, F, Cl, and Br has been established for all these explosive eruptions. The estimation of their eruptive fluxes towards the atmosphere supports the potential important role of halogen elements in the modification of atmosphere chemistry. Br degassing budget was the same order of magnitude as S whereas F and Cl budgets were 1 and 2 orders of magnitude higher than these two species.</p>

Shifting eruption dynamics: Constraints from mineral chemistry and plagioclase-hosted melt inclusions at Santiaguito volcanic dome complex, Guatemala

2020 ◽  
Author(s):  
Eva Hartung ◽  
Paul A. Wallace ◽  
Felix W. Von Aulock ◽  
Adrian Hornby ◽  
Yan Lavallée
Keyword(s):  
Melt Inclusions ◽  
Mineral Chemistry ◽  
Silica Content ◽  
Eruption Dynamics ◽  
Magma Storage ◽  
Fe Content ◽  
Wide Range ◽  
Storage Zone ◽  
Compositional Variations ◽  
Volcanic Dome

<p>Activity at Santiaguito volcanic dome complex started in 1922 with the continuous eruption of crystal-rich dacitic-andesitic lavas, which over the course of the last century, constructed a series of four domes and were host to frequent minor explosions. In 2016, a drastic shift in activity occurred with an 8-months period of heightened explosion intensity. We present records of textural and compositional variations in plagioclase, orthopyroxene and plagioclase-hosted melt inclusions of a series of ash and ballistic samples erupted and collected in-situ between 2015 and 2019 to reconstruct the magmatic processes associated with such shifts in activity.</p><p>Plagioclase phenocrysts show a wide range of compositions (An<sub>90-35</sub>) and can be grouped into three populations based on compositional and textural variations: crystals with resorbed albite-rich cores (An<sub>35–40</sub>), anorthite-rich cores (An<sub>85–90</sub>) and patchy zoned cores (An<sub>50–85</sub>). All plagioclase crystals contain homogenous rims of An<sub>50 </sub>that are marked by an increase in Fe content from about 3000 to 5000 ppm and a higher Mg content (of up to 300 ppm) towards the rim. Orthopyroxene phenocrysts show constant enstatite compositions from core to rim (En<sub>68-70</sub>). However, rims are relatively enriched and depleted in Ti and Mn contents respectively. Plagioclase-hosted melt inclusions are found in reversely zoned crystals, in crystal rims and between glomerocrysts. Irregularly shaped melt pockets are frequently observed in patchy zoned cores. Melt inclusions overall range in silica content from 71 to 78 SiO<sub>2 </sub>wt.% (anhydrous) and are marked by relatively high TiO<sub>2 </sub>and K<sub>2</sub>O contents.</p><p>Melt and mineral compositions and textures suggest that a shallow magma storage zone currently exists below Santiaguito volcanic dome complex. Pressure estimates of plagioclase-hosted melt inclusions yield an average of about 150 MPa (± 50 MPa) using rhyolite-MELTS indicating magma storage at depth of about 4 to 8 km. The observed increase in Fe, Mg and Ti contents in the rims of the plagioclase and orthopyroxene phenocrysts and microlite crystals are consistent with recharge of new magma into the upper crust, which was likely responsible for the drastic shift in eruption dynamics at Santiaguito volcanic dome complex in 2015-2016.</p>

Plagioclase as a witness of syn-eruptive degassing in rhyolitic magmas

2020 ◽  
Author(s):  
Ben Ellis ◽  
Julia Neukampf ◽  
Oscar Laurent ◽  
Lena Steinmann ◽  
Stefan Weyer ◽  
...  
Keyword(s):  
Melt Inclusions ◽  
Sudden Change ◽  
Isotopic Fractionation ◽  
Explosive Volcanism ◽  
Volcanic Field ◽  
Major And Trace Elements ◽  
Groundmass Glass ◽  
Strong Gradient ◽  
Anhydrous Mineral ◽  
Equilibrium Fractionation

<p>Lithium (Li) is one of the fastest diffusing elements in most geological media and so has the potential to provide information about processes occurring on timescales too short to be captured by other proxies.  These processes may be of fundamental importance both in terms of understanding what happens during explosive volcanism and for defining where lithium, an element of increasing economic importance, ends up.  To investigate the fate of Li, we studied in detail the 1.30 Ma Mesa Falls Tuff (MFT) from the Yellowstone volcanic field (USA).  MFT is a typical rhyolite of the Yellowstone system containing an anhydrous mineral assemblage of sanidine, quartz, plagioclase, clinopyroxene, fayalite, orthopyroxene and accessory phases.  We focussed on plagioclase crystals that have a strong gradient in Li contents from cores at ~25 ppm to rims with ~ 5 ppm.  This notable decrease in Li abundance is decoupled from changes in other major and trace elements.  δ<sup>7</sup>Li values measured by fs-LA-MC-ICPMS in the plagioclase crystals reveal that cores are about 5 ‰ lower than rims.  Taken together, the Li abundance and isotopic data make a compelling case for the plagioclase attempting to react to a sudden change in Li abundance in the surrounding melt.  Diffusion modelling of these gradients indicates that this sudden Li drop in the melt occurred over timescales of tens of minutes prior to quenching.  The volatile behaviour of Li implied by this result finds support in Li concentrations measured in quartz-hosted melt inclusions that reach 400 ppm while groundmass glass Li contents are much lower (36-55 ppm).  While equilibrium fractionation of stable isotopes is minimised at high temperatures, the large-magnitude, rapid loss of lithium from the melt phase may allow kinetic isotopic fractionation to occur, as recorded in the plagioclase crystals.  With glass / groundmass both volumetrically dominant and the main repository of Li in virtually all volcanic deposits, further consideration of how syn-eruptive processes may affect the bulk Li identity of a sample is warranted.        </p><p> </p>

scholarly journals Mid-crustal storage and crystallization of Eyjafjallajökull ankaramites, South Iceland

JOKULL ◽  
2020 ◽  
Vol 69 ◽  
pp. 83-102
Author(s):  
Paavo Nikkola ◽  
Enik˝o Bali ◽  
Maren Kahl ◽  
Quinten H. A. van der Meer ◽  
O. Tapani Rämö ◽  
...  
Keyword(s):  
Melt Inclusions ◽  
Chromian Spinel ◽  
Large Temperature ◽  
Magma Storage ◽  
Short Period ◽  
Magnesian Olivine ◽  
Mg Melt ◽  
Crustal Magma ◽  
Eruptive Behaviour

Our understanding of the long-term intrusive and eruptive behaviour of volcanic systems is hampered by a relatively short period of direct observation. To probe the conditions of crustal magma storage below South Iceland, we have analysed compositions of minerals, mineral zoning patterns, and melt inclusions from two Eyjafjallajökull ankaramites located at Brattaskjól and Hvammsmúli. These two units are rich in compositionally diverse macrocrysts, including the most magnesian olivine (Fo88-90) and clinopyroxene (Mg#cpx 89.8) known from Eyjafjallajökull. Olivine-hosted spinel inclusions have high Cr#spl (52–80) and TiO2 (1–3 wt%) and low Al2O3 (8–22 wt%) compared to typical Icelandic chromian spinel. The spinel-olivine oxybarometer implies a moderate oxygen fugacity of logFMQ 0–0.5 at the time of crystallization, and clinopyroxene-liquid thermobarometry crystallization at mid-crustal pressures (1.7–4.2 kbar, 3.0±1.4 kbar on average) at 1120–1195°C. Liquid-only thermometry for melt inclusions with Mg#melt 56.1–68.5 and olivine-liquid thermometry for olivine macrocrysts with Fo80.7-88.9 yield crystallization temperatures of 1155–1222°C and 1136–1213°C, respectively. Diffusion modelling of compositional zonations in the Brattaskjól olivine grains imply that the Brattaskjól macrocrysts were mobilized and transported to the surface from their mid-crustal storage within a few weeks (at most in 9–37 days). Trends in clinopyroxene macrocryst compositions and the scarcity of plagioclase indicate that the mid-crustal cotectic assemblage was olivine and clinopyroxene, with plagioclase joining the fractionating mineral assemblage later. In all, the crystal cargoes in the Brattaskjól and Hvammsmúli ankaramites are composed of agitated wehrlitic or plagioclase wehrlitic crystal mushes that crystallized over a large temperature interval at mid-crustal depths.

scholarly journals Apatite crystals reveal melt volatile budgets and magma storage depths at Merapi volcano, Indonesia

2020 ◽  
Author(s):  
Weiran Li ◽  
Fidel Costa ◽  
Kazuhide Nagashima
Keyword(s):  
Seismic Tomography ◽  
Melt Inclusions ◽  
Type Equation ◽  
Bimodal Distribution ◽  
Major Elements ◽  
Magma Ascent ◽  
Magma Storage ◽  
Merapi Volcano ◽  
Apatite Crystals ◽  
Magmatic Volatiles

Abstract Magma volatile budgets and storage depths play a key role in controlling the eruptive styles of volcanoes. Volatile concentrations in the melt can be inferred from analyses of glass inclusions, which however may not be present in the investigated rocks or may have experienced post-entrapment processes that modify their volatile records. Apatite is becoming an alternative robust tool for unraveling the information of magmatic volatiles. Here we report a comprehensive dataset for the concentrations of volatiles and major elements in apatite crystals in the rocks from two eruptions with contrasting eruptive styles: the 2006 (dome-forming) and 2010 (explosive) eruptive events at Merapi volcano (Java, Indonesia). We obtained two-dimensional compositional distributions and in situ concentrations of H2O, CO2, F, Cl, and S in 50 apatite crystals occurring at various textural positions. The CO2 concentrations we report are probably the first ones from natural volcanic apatite. Using the volatile concentrations in apatite and existing thermodynamic models and geothermobarometers, we have calculated the volatile abundances of the pre-eruptive melts of the two eruptions. We find that the apatite from the 2006 and 2010 deposits have a similar compositional range of volatiles, with a bimodal distribution of F-H2O-CO2 contents. The apatite included in amphibole has higher H2O (0.9–1.0 wt.%) and CO2 (Type equation here.≥2400 ppm), but lower F (0.9–1.4 wt.%), compared to crystals included in plagioclase, clinopyroxene, or in the groundmass (H2O: 0.4–0.7 wt.%; CO2: 40–900 ppm; F: 1.7–2.3 wt.%). Using these volatile concentrations and apatite-melt exchange coefficients we obtained two distinct ranges of H2O-CO2-S-F-Cl concentrations in the melt. Melts in equilibrium with apatite included in amphibole had 3–8 wt.% H2O, ≥8000 ppm CO2, 340–2000 ppm S, whereas melts in equilibrium with apatite included in anhydrous minerals and in the groundmass had lower H2O (1.5–4 wt.%), CO2 (60–2500 ppm), and S (10-130 ppm). We calculated the melt H2O-CO2 saturation pressures and found that they correspond to two main magma storage depths. The shallow reservoir with melts stored at ≤10 km below the crater agrees with the depths constrained by melt inclusions, as well as the geodetic, geophysical, and seismic tomography studies from the literature. We have also found a significantly deeper melt storage zone at ≥25–30 km recorded by the C- and H2O-rich apatite in amphibole and barometry calculations using amphibole and high-Al clinopyroxene, which matches with the depths reported in seismic tomography studies. The high CO2/H2O and CO2/SO2 concentrations of the deep melt can help to explain the sharp increase in these ratios in fumarolic gas that were sampled just before the eruption in 2010. Supply of deep volatiles to the shallower magma column before the eruption in 2010 could have increased the magma buoyancy, and thus led to higher magma ascent rates and associated eruption explosivity. Evidence for the faster pre-eruptive magma ascent in 2010 than 2006 is also found on the diffusion distance of Cl in apatite microlites.

scholarly journals Mafic glass compositions: a record of magma storage conditions, mixing and ascent

2019 ◽  
Vol 377 (2139) ◽  
pp. 20180004 ◽  
Author(s):  
Katharine V. Cashman ◽  
Marie Edmonds
Keyword(s):  
Melt Inclusions ◽  
Storage Conditions ◽  
Magma Storage ◽  
Magma Evolution ◽  
Reservoir Architecture ◽  
Multiple Paths ◽  
Magma Compositions ◽  
Moho Depths ◽  
Crystallization Path ◽  
Magma System

The trans-crustal magma system paradigm is forcing us to re-think processes responsible for magma evolution and eruption. A key concept in petrology is the liquid line of descent (LLD), which relates a series of liquids derived from a single parent, and therefore tracks the inverse of the crystallization path. It is common practice to attribute multiple magma compositions, and/or multiple melt compositions (from melt inclusions and matrix glass), to a single LLD. However, growing evidence for rapid, and often syn-eruptive, assembly of multiple magma components (crystals and melts) from different parts of a magmatic system suggests that erupted magma and melt compositions will not necessarily represent a single LLD, but instead may reflect the multiple paths in pressure–temperature space. Here, we use examples from mafic magmatic systems in both ocean island and arc settings to illustrate the range of melt compositions present in erupted samples, and to explore how they are generated, and how they interact. We highlight processes that may be deduced from mafic melt compositions, including the mixing of heterogeneous primitive liquids from the mantle, pre-eruptive magma storage at a range of crustal and sub-Moho depths, and syn-eruptive mixing of melts generated from these storage regions. The relative dominance of these signatures in the glasses depends largely on the water content of the melts. We conclude that preserved melt compositions provide information that is complementary to that recorded by the volatile contents of crystal-hosted melt inclusions and coexisting mineral compositions, which together can be used to address questions about both the pre- and syn-eruptive state of volcanic systems. This article is part of the Theo Murphy meeting issue ‘Magma reservoir architecture and dynamics’.

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