Extensive, water-rich magma reservoir beneath southern Montserrat

Edmonds, Marie; Kohn, Simon C.; Hauri, E. H.; Humphreys, Madeleine C. S.; Cassidy, Michael

doi:10.1016/j.lithos.2016.02.026

Cited by 46 publications

(42 citation statements)

References 117 publications

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“…As MIs with H 2 O content higher than 7 wt% are rarely reported, our data place the central Dominica magmas amongst the wettest in the world, comparable, for example, to dacites from Pinatubo, Philippines (Wallace 2005). Edmonds et al (2016) have proposed similarly H 2 O-rich andesite magmas (≤ 9.4 wt%) for Soufriere Hills Volcano, Montserrat, on the indirect basis of the H content of orthopyroxene phenocryst cores. On this basis, they invoke magma storage at depths of 5-16 km beneath Montserrat.…”

Section: Volatile Content and Behavior: Implications For Pre-eruptivesupporting

confidence: 69%

“…Based on H content of orthopyroxene phenocryst cores Edmonds et al (2016) have proposed H 2 O-rich andesite magmas (≤ 9.4 wt%), interpreted as due to a magma storage at depths of 5-16 km beneath Montserrat. The magma plumbing system beneath this volcano has also been described through the prism of the mush based on the excess of SO 2 flux interpreted as resulting from a decoupled sulfur degassing through transcrustal magmatic system.…”

Section: Soufriere Hills Volcano (Montserrat)mentioning

confidence: 99%

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Deep pre-eruptive storage of silicic magmas feeding Plinian and dome-forming eruptions of central and northern Dominica (Lesser Antilles) inferred from volatile contents of melt inclusions

Balcone-Boissard

Boudon

Blundy

et al. 2018

Contrib Mineral Petrol

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Volatiles contribute to magma ascent through the sub-volcanic plumbing system. Here, we investigate melt inclusion compositions in terms of major and trace elements, as well as volatiles (H 2 O, CO 2 , SO 2 , F, Cl, Br, S) for Quaternary Plinian and dome-forming dacite and andesite eruptions in the central and the northern part of Dominica (Lesser Antilles arc). Melt inclusions, hosted in orthopyroxene, clinopyroxene and plagioclase are consistently rhyolitic. Post-entrapment crystallisation effects are limited, and negligible in orthopyroxene-hosted inclusions. Melt inclusions are among the most water-rich yet recorded (≤ 8 wt% H 2 O). CO 2 contents are generally low (< 650 ppm), although in general the highest pressure melt inclusion contain the highest CO 2. Some low-pressure (< 3 kbars) inclusions have elevated CO 2 (up to 1100-1150 ppm), suggestive of fluxing of shallow magmas with CO 2-rich fluids. CO 2-trace element systematics indicate that melts were volatile-saturated at the time of entrapment and can be used for volatile-saturation barometry. The calculated pressure range (0.8-7.5 kbars) indicates that magmas originate from a vertically-extensive (3-27 km depth) storage zone within the crust that may extend to the sub-Dominica Moho (28 km). The vertically-extensive crustal system is consistent with mush models for sub-volcanic arc crust wherein mantle-derived mafic magmas undergo differentiation over a range of crustal depths. The other volatile range of composition for melt inclusions from the central part is F (75-557 ppm), Cl (1525-3137 ppm), Br (6.1-15.4 ppm) and SO 2 (< 140 ppm), and for the northern part it's F (92-798 ppm), Cl (1506-4428 ppm), Br (not determined) and SO 2 (< 569; one value at 1015 ppm). All MIs, regardless of provenance, describe the same Cl/F correlation (8.3 ± 2.7), indicating that the magma source at depth is similar. The high H 2 O content of Dominica magmas has implications for hazard assessment.

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Section: Volatile Content and Behavior: Implications For Pre-eruptivesupporting

confidence: 69%

Section: Soufriere Hills Volcano (Montserrat)mentioning

confidence: 99%

Deep pre-eruptive storage of silicic magmas feeding Plinian and dome-forming eruptions of central and northern Dominica (Lesser Antilles) inferred from volatile contents of melt inclusions

Balcone-Boissard

Boudon

Blundy

et al. 2018

Contrib Mineral Petrol

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“…Edmonds et al (2016) propose 6-9 wt% H 2 O in andesites from Soufrière Hills Volcano, Montserrat, on the basis of H 2 O dissolved in orthopyroxene phenocrysts. Grove et al (2003) proposed ≥ 11 wt% H 2 O in some primitive magmas from Mt.…”

Section: Implication For Arc Magmatismmentioning

confidence: 98%

Petrological and experimental evidence for differentiation of water-rich magmas beneath St. Kitts, Lesser Antilles

Melekhova

Blundy

Martin

et al. 2017

Contrib Mineral Petrol

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cumulate xenoliths and lavas are An 97 and An 95 , respectively. Fluid-saturated, equilibrium crystallisation experiments were performed on a St. Kitts basaltic andesite, with three different fluid compositions (XH 2 O = 1.0, 0.66 and 0.33) at 2.4 kbar, 950-1025 °C, and fO 2 = NNO − 0.6 to NNO + 1.2 log units. Experiments reproduce lava liquid lines of descent and many xenolith assemblages, but fail to match xenolith and lava phenocryst mineral compositions, notably the very An-rich plagioclase. The strong positive correlation between experimentally determined plagioclase-melt Kd Ca-Na and dissolved H 2 O in the melt, together with the occurrence of Al-rich mafic lavas, suggests that parental magmas were water-rich (> 9 wt% H 2 O) basaltic andesites that crystallised over a wide pressure range (1.5-6 kbar). Comparison of experimental and natural (lava, xenolith) mafic mineral composition reveals that whereas olivine in lavas is predominantly primocrysts precipitated at low-pressure, pyroxenes and spinel are predominantly xenocrysts formed by disaggregation of plutonic mushes. Overall, St. Kitts xenoliths and lavas testify to mid-crustal differentiation of low-MgO basalt and basaltic andesite magmas within a trans-crustal, magmatic mush system. Lower crustal ultramafic cumulates that relate parental lowMgO basalts to primary, mantle -derived melts are absent on St. Kitts.Keywords Xenolith · Cumulates · High-An plagioclase · Differentiation of basaltic andesite · Experiments · 'Magma mush' IntroductionArc magmatism above subduction zones involves chemical differentiation of mantle-derived basaltic magmas Abstract St. Kitts lies in the northern Lesser Antilles, a subduction-related intraoceanic volcanic arc known for its magmatic diversity and unusually abundant cognate xenoliths. We combine the geochemistry of xenoliths, melt inclusions and lavas with high pressure-temperature experiments to explore magma differentiation processes beneath St. Kitts. Lavas range from basalt to rhyolite, with predominant andesites and basaltic andesites. Xenoliths, dominated by calcic plagioclase and amphibole, typically in reaction relationship with pyroxenes and olivine, can be divided into plutonic and cumulate varieties based on mineral textures and compositions. Cumulate varieties, formed primarily by the accumulation of liquidus phases, comprise ensembles that represent instantaneous solid compositions from one or more magma batches; plutonic varieties have mineralogy and textures consistent with protracted solidification of magmatic mush. Mineral chemistry in lavas and xenoliths is subtly different. For example, plagioclase with unusually high anorthite content (An ≤100 ) occurs in some plutonic xenoliths, whereas the most calcic plagioclase in Communicated by Othmar Müntener. Electronic supplementary materialThe online version of this article (https://doi.org/10.1007/s00410-017-1416-3) contains supplementary material, which is available to authorized users.

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“…On one hand, comparison among isotopic ages of multiple accessory phases, trace element diffusion timescales, and thermodynamic considerations suggests eruptible magma is a transient feature within a storage regime dominated by cool, crystalline, and perhaps subsolidus conditions that require an external energy source to mobilize into an eruption (Cooper & Kent, ; Rubin et al, ; Szymanowski et al, ). Conversely, elevated temperatures recorded by zircon crystals suggest eruptible magma may be stored for 10 3 –10 4 years (Barboni et al, ; Edmonds et al, ; Tierney et al, ). These models are particularly relevant for evaluating volcanic hazard because if eruptible magma is an ephemeral feature, detecting such a body using geophysical techniques would indicate a system primed for imminent eruption (Cooper & Kent, ).…”

Section: Introductionmentioning

confidence: 99%

Repeated Rhyolite Eruption From Heterogeneous Hot Zones Embedded Within a Cool, Shallow Magma Reservoir

2019

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Despite the hazard posed by explosive silicic eruptions, the magma storage conditions and dynamics that precede these events remain controversial. The Laguna del Maule volcanic field, central Chile, is an exceptional example of postglacial (younger than ca. 20,000 years) rhyolite volcanism and sustained unrest driven by a large, shallow, active silicic magma system. New zircon petrochronologic data reveal that compositionally distinct domains developed concurrently within the Laguna del Maule magma reservoir, which produced two episodes of concentrated rhyolitic eruptions at 23–19 and 8–2 ka. Zircon crystallization ages record 160 kyr of magma emplacement resulting in a several hundreds of cubic kilometers reservoir that has been imaged geophysically. The average magma emplacement rate inferred from the zircon geochronology and tomographically defined magma volume is consistent with those required by thermal models to maintain a shallow silicic system. Ti‐in‐zircon temperatures of crystal cores and rims and hiatuses in crystal growth indicates most of this volume persisted in a near‐solidus state. However, consistent patterns of trace element zoning in crystal interiors and crystallization rates derived from a model of diffusion‐limited zircon growth suggest the erupted rhyolite magma batches originated from long‐lived hot zones of extractable mush embedded within the larger, cool reservoir of rigid mush. These contrasting, coeval magma storage conditions obviate a simple hot versus cold storage dichotomy for large silicic magma systems.

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Extensive, water-rich magma reservoir beneath southern Montserrat

Cited by 46 publications

References 117 publications

Deep pre-eruptive storage of silicic magmas feeding Plinian and dome-forming eruptions of central and northern Dominica (Lesser Antilles) inferred from volatile contents of melt inclusions

Deep pre-eruptive storage of silicic magmas feeding Plinian and dome-forming eruptions of central and northern Dominica (Lesser Antilles) inferred from volatile contents of melt inclusions

Petrological and experimental evidence for differentiation of water-rich magmas beneath St. Kitts, Lesser Antilles

Repeated Rhyolite Eruption From Heterogeneous Hot Zones Embedded Within a Cool, Shallow Magma Reservoir

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