Diffusion Data in Silicate Melts

Zhang, Youxue; Ni, Huaiwei; Chen, Yang

doi:10.2138/rmg.2010.72.8

Cited by 326 publications

(176 citation statements)

References 132 publications

(636 reference statements)

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“…The values used for Cl in these calculations (0.2-0.3 wt% Cl) are based on estimated concentrations in the pre-eruptive hybrid melt. However, the Cl contents in the matrix glasses are minimal values for pre-eruptive concentrations because of losses due to degassing from the hybrid trachyandesitic melt during eruption and non-negligible Cl diffusion in silicic melts at $1000 C [Zhang et al, 2010]. Therefore, the calculated values of the mass of liberated fluid are maximum values.…”

Section: Mass Of the Hybrid Trachyandesitic Magma And Fluidmentioning

confidence: 97%

“…The S contents used in the calculations (0.02 wt% S) are, however, low because of the possibility of hybrid melt degassing upon eruption. However, because of extremely sluggish S diffusion rates in silicic melts [Zhang et al, 2010;Behrens and Stelling, 2011], there is uncertainty about the actual loss rates of S related to matrix glass degassing during an eruption. The calculated maximum values of S partitioning (Kd fluid/melt = 0.4-0.9) are in the range of theoretical partitioning values at $QFM AE 1 redox conditions (Kd fluid/melt = 0.1-10 [Scaillet et al, 1998]), suggesting no significant S input from crustal S-rich hydrothermal sources during the 2010 eruption.…”

Section: Aqueous Fluid Phase: Composition and Genesismentioning

confidence: 99%

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Processes controlling the 2010 Eyjafjallajökull explosive eruption

Borisova¹,

Toutain²,

Stefánsson³

et al. 2012

J. Geophys. Res.

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[1] To constrain the temporal evolution of the fluid-magma system responsible for the 2010 Eyjafjallajökull eruption (20 March to 20 May, 2010, Southern Iceland), we investigated the volatile, major, trace element, and Sr-Nd-Pb isotopic compositions of bulk lapilli and ash samples representing different stages of the eruption. In addition, we analyzed ash leachates and volcanic plume-derived aerosols sampled over Southern Europe in early May 2010. Available remote-sensing data for the total mass of SO 2 liberated in the 2010 eruption, together with data obtained in this study, suggest that the high explosivity of the 2010 sub-plinian Eyjafjallajökull eruption was caused by saturation of the pre-eruptive hybrid trachyandesitic magma with aqueous fluid. We hypothesize that the bulk of the aqueous fluid had been dissolved in the trachydacitic melt at least since the eruption of 1821-1823. The trachydacitic melt was enriched in volatiles, large-ion lithophile elements, and high field strength elements, a composition similar to that of oceanic sediments. The Sr-Nd-Pb isotopic data obtained in this study, combined with existing O isotopic data on bulk 2010 Eyjafjallajökull lapilli and ashes, demonstrate that this melt enrichment was due to its primary source being hydrous oceanic lithosphere entrained in a deep mantle plume rather than shallow hydrothermally altered crust. The hypothesized strong crystal fractionation of plume-derived mafic melts (crystallized fraction >90%) from an enriched mantle source can explain the observed high explosivity of silicic and hybrid Icelandic magmas, especially those of the southeastern volcanic zone (Eyjafjallajökull, Katla, and Hekla).

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Section: Mass Of the Hybrid Trachyandesitic Magma And Fluidmentioning

confidence: 97%

Section: Aqueous Fluid Phase: Composition and Genesismentioning

confidence: 99%

Processes controlling the 2010 Eyjafjallajökull explosive eruption

Borisova¹,

Toutain²,

Stefánsson³

et al. 2012

J. Geophys. Res.

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“…For embayments with bubbles attached to the embayment mouth, this diffusion, while a consequence of the drop in solubility during decompression, is driven by the concentration of dissolved volatiles at the melt-bubble interface, a direct function of vapor pressure inside the bubble. The diffusivities of H 2 O, CO 2 , and S in silicate melts are sufficiently small to prevent the attainment of equilibrium concentrations within embayments that have lengths on the order of 100 microns for a wide range of decompression rates (e.g., Lensky et al, 2004;Gonnerman and Manga, 2005;Pichavant et al, 2013;Zhang et al, 2007Zhang et al, , 2010. Consequently, distinct diffusion-controlled concentration profiles may be preserved within an embayment, allowing the estimation of decompression rates via diffusion modeling (Liu et al, 2007).…”

Section: Melt Embayments and Choice Of Samplesmentioning

confidence: 99%

“…Magma temperature was found using the olivine-liquid thermometer of Helz and Thornber (1987) and was assumed constant. Although the magma may undergo cooling of about 100℃ upon ascent (e.g., Sahagian and Proussevitch, 1996;Mastin and Ghiorso, 2001), the corresponding change in volatile diffusivity is approximately a factor of 1/2 for H 2 O, CO 2 and S each (Freda et al, 2005;Zhang et al, 2007Zhang et al, , 2010. Because cooling will be most pronounced in the upper few hundred meters of the conduit, where most of the H 2 O exsolves and vapor expansion is largest, the effect of cooling is likely no more or less than a factor of two on decompression-rate estimates.…”

Section: Diffusion Modellingmentioning

confidence: 99%

Magma decompression rates during explosive eruptions of Kīlauea volcano, Hawaii, recorded by melt embayments

et al. 2016

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The decompression rate of magma as it ascends during volcanic eruptions is an important but poorly constrained parameter that controls many of the processes that influence eruptive behaviour. In this study we quantify decompression rates for basaltic magmas using volatile diffusion in olivine-hosted melt tubes (embayments) for three contrasting eruptions of Kīlauea volcano, Hawai'i. Incomplete exsolution of H 2 O, CO 2 and S from the embayment melts during eruptive ascent creates diffusion profiles that can be measured using microanalytical techniques, and then modelled to infer the average decompression rate. We obtain average rates of ~0.05-0.45 MPa s -1 for eruptions ranging from Hawaiian style fountains to basaltic subplinian, with the more intense eruptions having higher rates. The ascent timescales for these magmas vary from around ~5 to ~36 minutes from depths of ~2 to ~4 km respectively. Decompression-exsolution models based on the embayment data also allow for an estimate of the mass fraction of pre-existing exsolved volatiles within the magma body. In the eruptions studied this varies from 0.1-3.2 wt%, but does not appear to be the key control on eruptive intensity. Our results do not support a direct link between the concentration of pre-eruptive volatiles and eruptive intensity; rather they suggest that for these eruptions decompression rates are proportional to independent estimates of mass discharge rate. Although the intensity of eruptions is defined by the discharge rate, based on the currently available dataset of embayment analyses it does not appear to scale linearly with average decompression rate. This study demonstrates the utility of the embayment method for providing quantitative constraints on magma ascent during explosive basaltic eruptions.

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“…The pressure is set to 0.1 MPa and the fO 2 is set at the FMQ buffer, the crystallization conditions of NWA 1068 groundmass (Herd, 2006). The diffusion of Fe and Mg in basaltic melts is several orders of magnitude faster than Fe-Mg interdiffusion in olivine (Zhang et al, 2010). Therefore, we only model diffusion in olivine megacrysts and consider that diffusion in the melt is infinitely fast.…”

Section: Simple Diffusion and Crystallization Modelsmentioning

confidence: 99%

Crystallization history of enriched shergottites from Fe and Mg isotope fractionation in olivine megacrysts

Collinet

Charlier

Namur

et al. 2017

Geochimica et Cosmochimica Acta

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Martian meteorites are the only samples available from the surface of Mars. Among them, olivine-phyric shergottites are basalts containing large zoned olivine crystals with highly magnesian cores 26 Mg = À0.27 ± 0.04‰). The flat forsterite profiles of megacryst cores associated with anti-correlated fractionation of Fe-Mg isotopes indicate that these elements have been rehomogenized by diffusion at high temperature. We present a 1-D model of simultaneous diffusion and crystal growth that reproduces the observed element and isotope profiles. The simulation results suggest that the cooling rate during megacryst core crystallization was slow (43 ± 21°C/year), and consistent with pooling in a deep crustal magma chamber. The megacryst rims then crystallized 1-2 orders of magnitude faster during magma transport toward the shallower site of final emplacement. Megacryst cores had a forsterite content 3.2 ± 1.5 mol% higher than their current composition and some were in equilibrium with the whole-rock composition of NWA 1068 (Fo 80 ± 1.5). NWA 1068 composition is thus close to a primary melt (i.e. in equilibrium with the mantle) from which other enriched shergottites derived.

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Diffusion Data in Silicate Melts

Abstract: International audienc

Cited by 326 publications

References 132 publications

Processes controlling the 2010 Eyjafjallajökull explosive eruption

Processes controlling the 2010 Eyjafjallajökull explosive eruption

Magma decompression rates during explosive eruptions of Kīlauea volcano, Hawaii, recorded by melt embayments

Crystallization history of enriched shergottites from Fe and Mg isotope fractionation in olivine megacrysts

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