Halogens in Silicic Magmas and Their Hydrothermal Systems

Dolejš, David; Zajacz, Zoltán

doi:10.1007/978-3-319-61667-4_7

Cited by 42 publications

(17 citation statements)

References 368 publications

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“…This is expected, because the ability of water to hydrate the strong dipole NaCl ion pairs is higher at higher fluid densities due to the increased dielectric constant of water (Helgeson, 1981;Bowers and Helgeson, 1983;Driesner et al, 1998). A similar correlation between pressure and was (Shinohara et al, 1989;Signorelli and Carroll, 2002;Dolejš and Zajacz, 2018). (Shinohara et al, 1989); y=1.31(±0.23)*x-1.66(±0.50), R 2 =0.913 (Webster, 1992a).…”

Section: CLmentioning

confidence: 69%

Chlorine partitioning between granitic melt and H2O-CO2-NaCl fluids in the Earth’s upper crust and implications for magmatic-hydrothermal ore genesis

Hsu

Zajacz

Ulmer

et al. 2019

Geochimica et Cosmochimica Acta

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Section: CLmentioning

confidence: 69%

Chlorine partitioning between granitic melt and H2O-CO2-NaCl fluids in the Earth’s upper crust and implications for magmatic-hydrothermal ore genesis

Hsu

Zajacz

Ulmer

et al. 2019

Geochimica et Cosmochimica Acta

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“…Despite their minor concentrations compared to H2O and CO2,halogens (F,Cl,Br and I) are critical elements in the evolution of magmatic and volcanic systems, for instance affecting magma rheology and enabling the scavenging and hydrothermal concentration of metals in the crust (Dolejs and Zajacz, 2018;Webster et al, and references therein).…”

Section: Introductionmentioning

confidence: 99%

New insights on Br speciation in volcanic glasses and structural controls on halogen degassing

Louvel

Cadoux

Brooker

et al. 2020

American Mineralogist

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The volcanic degassing of halogens, and especially of the heavier Br and I, received increased attention over the last 20 years due to their significant effect on atmospheric chemistry, notably the depletion of stratospheric ozone. While the effect of melt composition on halogen diffusion, solubility, or fluid-melt partitioning in crustal magma chambers has been thoroughly studied, structural controls on halogen incorporation in silicate melts remain poorly known, with only few studies available in simplified borosilicate or haplogranite compositions. Here, we demonstrate that high-energy resolution fluorescence detection X-ray absorption spectroscopy (HERFD-XAS) with a crystal analyzer spectrometer (CAS) is well-suited for the study of Br speciation in natural volcanic glasses which can contain lower Br concentrations than their laboratory analogs. Especially, HERFD-XAS results in sharper and better-resolved XANES and EXAFS features than previously reported and enables detection limits for EXAFS analysis down to 100 ppm when previous studies required Br concentrations above the 1000 ppm level. XANES and EXAFS analyses suggest important structural differences between synthetic haplogranitic glass, where Br is surrounded by Na and next-nearest oxygen neighbors, and natural volcanic glasses of basaltic to rhyodacitic compositions, where Br is incorporated in at least three distinct sites, surrounded by Na, K, or Ca. Similar environments, involving both alkali and alkaline earth metals have already been reported for Cl in Ca-bearing aluminosilicate glass and our study thus underlines that the association of Br with divalent cations (Ca2+) has been underestimated in the past due to the use of simplified laboratory analogs. Overall, similarities in Cl and Br structural environments over a large array of compositions (46–67 wt% SiO2) suggest that melt composition alone may not have a significant effect on halogen degassing and further support the coupled degassing of Cl and Br in volcanic systems.

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“…This finding may indicate that the fluoride activity in the majority of metamorphic aqueous fluids is rather low. The reason for that could be the high affinity of fluorine to silicate (Dolejš and Zajacz, 2018;Dalou et al, 2015) which is one of the main components of aqueous phases in metamorphic processes (Manning, 2018;Hermann et al, 2006).…”

Section: Discussionmentioning

confidence: 99%

Yttrium speciation in subduction zone fluids from <i>ab initio</i> molecular dynamics simulations

Stefanski¹,

Jahn²

2020

Preprint

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Abstract. The rare earth elements (REE) are important geochemical tracers for geological processes such as high grade metamorphism. Aqueous fluids are considered important carriers for the REE in a variety of geological environments including settings associated with subduction zones. The capacity of a fluid to mobilize REE strongly depends on its chemical composition and on the presence of suitable ligands such as fluoride and chloride. In this study we present structural and thermodynamic properties of aqueous yttrium chloride and fluoride species at a temperature of 800 °C in a pressure range between 1.3 and 4.5 GPa derived from ab initio molecular dynamics simulations. The total yttrium coordination by H2O and halide ions changes from seven to eight within the pressure range. For the yttrium chloride species a maximum number of three chloride ligands was observed. The derived thermodynamic data show that aqueous yttrium fluoride complexes are more stable than their yttrium chloride counterparts at conditions relevant to slab dehydration. Mixed Y-(Cl,F) complexes are found to be unstable. Furthermore, in contrast to field observations thermodynamic modeling indicates that yttrium should be mobilized at rather low fluoride concentrations in high-grade metasomatic systems. These results suggest a rather low fluoride activity in the majority of subduction zone fluids because yttrium is one of the least mobile REE. Additionally, the simulations indicate that yttrium drives the self-ionization of hydration water molecules as it was observed for other high field strength elements. This might be a general property for highly charged cations in aqueous solutions under high temperature and high pressure conditions.

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Halogens in Silicic Magmas and Their Hydrothermal Systems

Cited by 42 publications

References 368 publications

Chlorine partitioning between granitic melt and H2O-CO2-NaCl fluids in the Earth’s upper crust and implications for magmatic-hydrothermal ore genesis

Chlorine partitioning between granitic melt and H2O-CO2-NaCl fluids in the Earth’s upper crust and implications for magmatic-hydrothermal ore genesis

New insights on Br speciation in volcanic glasses and structural controls on halogen degassing

Yttrium speciation in subduction zone fluids from <i>ab initio</i> molecular dynamics simulations

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Halogens in Silicic Magmas and Their Hydrothermal Systems

Cited by 42 publications

References 368 publications

Chlorine partitioning between granitic melt and H2O-CO2-NaCl fluids in the Earth’s upper crust and implications for magmatic-hydrothermal ore genesis

Chlorine partitioning between granitic melt and H2O-CO2-NaCl fluids in the Earth’s upper crust and implications for magmatic-hydrothermal ore genesis

New insights on Br speciation in volcanic glasses and structural controls on halogen degassing

Yttrium speciation in subduction zone fluids from &lt;i&gt;ab initio&lt;/i&gt; molecular dynamics simulations

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Yttrium speciation in subduction zone fluids from <i>ab initio</i> molecular dynamics simulations