The roles of decompression rate and volatiles (H2O + Cl ± CO2± S) on crystallization in (trachy-) basaltic magma

Fiege, Adrian; Vetere, Francesco; Iezzi, Gianluca; Simon, Adam C.; Holtz, François

doi:10.1016/j.chemgeo.2015.07.016

Cited by 21 publications

(15 citation statements)

References 74 publications

(118 reference statements)

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“…Riker et al (2015) attributed the difference to an increase in the temperature of the nucleation rate maximum in the CO 2 -bearing material, and yet another factor more likely contributing to the observed textural differences is the effect of lowering dissolved H 2 O content, through the addition of CO 2 , on the phase relations of the material at the initial dwell conditions. Decreasing dissolved H 2 O at constant pressure has the same effect on plagioclase stability as decreasing H 2 O during H 2 O-saturated decompression: the plagioclase-in temperature increases Médard and Grove, 2008;Fiege et al, 2015). Taking the MP rhyolite as an example, phase equilibrium data under H 2 O-saturated conditions (Martel, 2012) indicate that at the plagioclase-in pressure (188 MPa at 850ºC), the melt has 5.8 wt.% dissolved H 2 O.…”

Section: Beyond H 2 O and Co 2 : Adding Other Volatilesmentioning

confidence: 98%

“…The run products contain nearly identical dissolved H 2 O contents, ruling out a role for H 2 O in modulating phase relations. The suggestion by Fiege et al (2015), that a reduction in the activity of H 2 O within the fluid phase accounts for the greater clinopyroxene content of the S-bearing system, requires further investigation. Vetere et al (2015) augment the experimental data set of Vetere et al (2013), which examines the effects of major-element composition, cooling rate, and thermal history on solidification kinetics in oxidized, nominally anhydrous silicate melts (Fig.…”

Section: Beyond H 2 O and Co 2 : Adding Other Volatilesmentioning

confidence: 99%

“…Nowak et al (2011) introduced a valve capable of metering incremental gas in the IHPV setup. This device was used to study degassing kinetics and was employed in crystallization experiments of Fiege et al (2015), although the results were not compared with multi-step style decompression. Preliminary experiments suggest that stepwise decompression produces similar plagioclase contents regardless of the number of steps (n, for n from 1 to 25), appreciably different plagioclase and pyroxene compositions if n < 5, and plagioclase morphology that is sensitive to n 4 25 (Hammer et al, unpublished data).…”

Section: Crystal Nucleation As a Means Of Examining Volcanic Processesmentioning

confidence: 99%

“…The difficulty containing and moderating oxidation in higher-temperature melts within cold-seal pressure vessels suppresses the experimental pursuit of crystallization kinetics studies relative to high silica compositions. Fiege et al (2015) studied crystallization of natural fused trachybasalt from the 2001 eruption of Mt. Etna, applying isothermal continuous decompression rates of 3600, 360 and 36 MPa h À1 from 300 to 70 MPa using a low-flow pressure metering valve for the internally heated pressure vessel (Nowak et al, 2011).…”

Section: Beyond H 2 O and Co 2 : Adding Other Volatilesmentioning

confidence: 99%

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Dynamic crystallization in magmas

Mollo¹,

Hammer²

2017

Mineral Reaction Kinetics: Microstructures, Textures, Chemical and Isotopic Signatures

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Undercooling and crystallization kinetics are recognized increasingly as important processes controlling the final textures and compositions of minerals as well as the physicochemical state of magmas during ascent and emplacement. Within a single volcanic unit, phenocrysts, microphenocrysts and microlites can span a wide range of compositions, develop complex zoning patterns, and show intricate textures testifying to crystallization far from equilibrium. These petrographic complexities are not associated necessarily with magma chamber processes such as mixing or mingling of distinctly different bulk compositions but, rather, may be caused by variable degrees of initial magma-undercooling and the evolution of undercooling through time. Heat-dissipation and decompression are the most effective driving forces of cooling and volatile loss that, in turn, exert a primary control on the solidification path of magma. Understanding these kinetic aspects over the temporal and spatial scales at which volcanic processes occur is therefore essential to interpret correctly the time-varying environmental conditions recorded in igneous minerals.This contribution aims to summarize and integrate experimental studies pertaining to the crystallization of magmas along kinetic or time-dependent pathways, where solidification is driven by changes in temperature, pressure and volatile concentration. Fundamental concepts examined in the last decades include the effect of undercooling on crystal nucleation and growth as well as on the transition between interface-and diffusion-controlled crystal growth and mass transfer occurring after crystals stop growing. We summarize recent static and dynamic decompression and cooling experiments that explore the role of undercooling in syn-eruptive crystallization occurring as magmas ascend in volcanic conduits and are emplaced at the surface. The ultimate aim of such studies is to decode the textural and compositional information within crystalline phases to place quantitative constraints on the crustal transport, ascent and emplacement histories of erupted and intrusive magmas.Magma crystallization under dynamic conditions will be assessed also through a comparative description of the disequilibrium features in minerals found in experimental and natural materials. A variety of departures from polyhedral growth, including morphologies indicating crystal surface instability, dendritic structures, sector zoning and growth twins are linked to the rate at which crystals grow. These have implications for the entrapment of melt inclusions and plausibility for interpreting the growth chronology of individual crystals. A simple ''tree-ring'' model, in which the oldest part of the crystal lies at the centre and the youngest at the rim, is not an appropriate description when growth is non-concentric. Further, deviation from chemical

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Section: Beyond H 2 O and Co 2 : Adding Other Volatilesmentioning

confidence: 98%

Section: Beyond H 2 O and Co 2 : Adding Other Volatilesmentioning

confidence: 99%

Section: Crystal Nucleation As a Means Of Examining Volcanic Processesmentioning

confidence: 99%

Section: Beyond H 2 O and Co 2 : Adding Other Volatilesmentioning

confidence: 99%

See 2 more Smart Citations

Dynamic crystallization in magmas

Mollo¹,

Hammer²

2017

Mineral Reaction Kinetics: Microstructures, Textures, Chemical and Isotopic Signatures

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show abstract

“…Most of the published experimental approaches aim to track the viscosity variation as a function of temperature, volatile content, and crystallinity. Moreover, experimental study on crystallization induced by variable decompression rates allowed scientists to shed new light on processes governing magma ascent dynamics (Fiege et al, , and references therein). Following the pioneering work of Carmichael (), reporting the rheological importance of the coexistence of crystals and liquid material, melt solidification processes have been investigated via experiments under different applied cooling rates (see Hammer, , for a general summary).…”

Section: Introductionmentioning

confidence: 99%

Viscosity of Pyroxenite Melt and Its Evolution During Cooling

et al. 2019

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New viscosity experiments at superliquidus temperatures and during cooling at a rate of 10 K/hr have been performed at different shear rates on a synthetic pyroxenite melt. Results revealed that this melt is extremely fluid at temperature between 1646 and 1530 K and measured viscosities are between 2.2 and 7.8 Pa·s. Such very low viscosities allow the lava to flow in turbulent regime as confirmed by the high Reynolds numbers, which are always >2,000. As a consequence, very long distance could be covered by the lava flow. If we consider this studied composition as proxy for Mars lava flows coupled with very high effusion rates, our results might explain the presence of extraordinary large volcanic channels, as recently hypothesized for the Kasei Valles on Mars, even considering that the gravity is approximately one third that of Earth. Few literature data tracking viscosity during cooling are available, and they reported shear thinning effect on different compositions. Our experiments performed at 0.1 and 1 s−1 have shown complex variation in the apparent viscosity, confirming that nonequilibrium rheology represents a still unexplored field of investigation useful to better understand the real geological scenarios occurring in magmatic and volcanic systems.

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Effect of melt composition on crustal carbonate assimilation: Implications for the transition from calcite consumption to skarnification and associated CO₂ degassing

Carter

Dasgupta

2016

Geochem Geophys Geosyst

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Skarns are residue of relatively low-temperature magma-induced decarbonation in the crust largely associated with silicic plutons. Mafic magmatic intrusions are also capable of releasing excess CO 2 due to carbonate assimilation. However, the effect of mafic to silicic melt evolution on the decarbonation processes, in addition to temperature controls on carbonate-intrusive magmatic systems, particularly at continental arcs, remains unclear. In this study, experiments performed in a piston cylinder apparatus at midcrustal depth (0.5 GPa) at supersolidus temperatures (900-12008C) document calcite interaction with andesite and dacite melts at equilibrium under closed-system conditions at calcite saturation in a 1:1 meltcalcite ratio by weight. With increasing silica content in the starting melt, at similar melt fractions and identical pressure, assimilation decreases drastically (65% andesite-calcite to 18% dacite-calcite). In conjunction, the CaO/SiO 2 ratio in melts resulting from calcite assimilation in andesitic starting material is >1, but 0.3 in those formed from dacite-calcite interaction. With increasing silica-content in the starting melt skarn mineralogy, particularly wollastonite, increases in modal abundance while diopsidic clinopyroxene decreases slightly. More CO 2 is released with andesite-calcite reaction (2.9 3 10 11 g/y) than with more skarn-like dacite-calcite interaction (8.1 3 10 10 g/y, at one volcano assuming respective calcite-freesuperliquidus conditions and a magma flux of 10 12 g/y). Our experimental results thus suggest that calcite assimilation in more mafic magmas may have first degassed a significant amount of crustal carbon before the melt evolves to more silicic compositions, producing skarn. Crustal decarbonation in long-lived magmatic systems may hence deliver significant albeit diminishing amounts of carbon to the atmosphere and contribute to long-term climate change. Key Points:Limestone assimilation increases with infiltration of hydrous andesitic melt over basaltic but decreases with dacite Skarn minerals like wollastonite increase in abundance in more silicic magma-calcite interaction Assimilation can release <0.4 Gt CO 2 during intruding magma evolution from basalt to granite

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The roles of decompression rate and volatiles (H2O + Cl ± CO2± S) on crystallization in (trachy-) basaltic magma

Cited by 21 publications

References 74 publications

Dynamic crystallization in magmas

Dynamic crystallization in magmas

Viscosity of Pyroxenite Melt and Its Evolution During Cooling

Effect of melt composition on crustal carbonate assimilation: Implications for the transition from calcite consumption to skarnification and associated CO₂ degassing

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The roles of decompression rate and volatiles (H2O + Cl ± CO2± S) on crystallization in (trachy-) basaltic magma

Cited by 21 publications

References 74 publications

Dynamic crystallization in magmas

Dynamic crystallization in magmas

Viscosity of Pyroxenite Melt and Its Evolution During Cooling

Effect of melt composition on crustal carbonate assimilation: Implications for the transition from calcite consumption to skarnification and associated CO2 degassing

Contact Info

Product

Resources

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Effect of melt composition on crustal carbonate assimilation: Implications for the transition from calcite consumption to skarnification and associated CO₂ degassing