Fe isotope fractionation during phase separation in the NaCl–H2O system: An experimental study with implications for seafloor hydrothermal vents

Syverson, Drew D.; Pester, Nicholas J.; Craddock, Paul R.; Seyfried, William E.

doi:10.1016/j.epsl.2014.09.020

Cited by 24 publications

(12 citation statements)

References 52 publications

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“…This is consistent with observed changes in 527 the Fe isotopic composition of vapors collected during Exp. 4 (Syverson et al, 2014). and Central Indian Ridge, CIR).…”

Section: Potentially Dominant Chloro-complexes 461 16mentioning

confidence: 99%

Vapor–liquid partitioning of alkaline earth and transition metals in NaCl-dominated hydrothermal fluids: An experimental study from 360 to 465 °C, near-critical to halite saturated conditions

Pester

Ding

Seyfried

2015

Geochimica et Cosmochimica Acta

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Multi-phase fluid flow is a common occurrence in magmatic hydrothermal systems; and 1 extensive modeling efforts using currently established P-V-T-x properties of the NaCl-H 2 O system are 2 impending. We have therefore performed hydrothermal flow experiments (360-465 °C) to observe vapor-3 liquid partitioning of alkaline earth and first row transition metals in NaCl-dominated source solutions. 4The data allow extraction of partition coefficients related to the intrinsic changes in both chlorinity and 5 density along the two-phase solvus. The coefficients yield an overall decrease in vapor affinity in the 6 order Cu(I) > Na > Fe(II) > Zn > Ni(II) ≥ Mg ≥ Mn(II) > Co(II) > Ca > Sr > Ba, distinguished with 95% 7 confidence for vapor densities greater than ~0.2 g/cm 3 . The alkaline earth metals are limited to purely 8 electrostatic interactions with Cl ligands, resulting in an excellent linear correlation (R 2 > 0.99) between 9 their partition coefficients and respective ionic radii. Though broadly consistent with this relationship, 10 relative behavior of the transition metals is not well resolved, being likely obscured by complex bonding 11 processes and the potential participation of Na in the formation of tetra-chloro species. At lower densities 12 (at/near halite saturation) partitioning behavior of all metals becomes highly non-linear, where M/Cl ratios 13 in the vapor begin to increase despite continued decreases in chlorinity and density. We refer to this 14 phenomenon as "volatility", which is broadly associated with substantial increases in the HCl/NaCl ratio 15 (eventually to > 1) due to hydrolysis of NaCl. Some transition metals (e.g., Fe, Zn) exhibit volatility prior 16 to halite stability, suggesting a potential shift in vapor speciation relative to nearer critical regions of the 17 © 2015. This manuscript version is made available under the Elsevier user license http://www.elsevier.com/open-access/userlicense/1.0/ 2 vapor-liquid solvus. The chemistry of deep-sea hydrothermal fluids appears affected by this process 18 during magmatic events, however, our results do not support suggestions of subseafloor halite 19 precipitation recorded in currently available field data. Ca-Cl systematics in vent fluids are specifically 20 explored, revealing behavior consistent with partitioning due to phase separation. Interestingly, the effect 21 of variable chloride on dissolved Na/Ca ratios associated with plagioclase solubility (in single-phase 22 solutions) appears fundamentally similar to that of phase separation on vapor compositions such that 23 vapors evolved in hydrothermal systems may naturally remain near equilibrium with the host lithology. 24Conversely, residual liquids/brines left behind in the crust may be undersaturated with metals, enhancing 25 the rate and extent of hydrothermal alteration. 26 3 near the magma-hydrothermal interface prior to eruption (Coombs et al., 2004;le Roux et al., 2006; 49 Michael and Cornell, 1998). Such data are not only consistent with phase separation, but also phase 50...

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“…This is consistent with observed changes in 527 the Fe isotopic composition of vapors collected during Exp. 4 (Syverson et al, 2014). and Central Indian Ridge, CIR).…”

Section: Potentially Dominant Chloro-complexes 461 16mentioning

confidence: 99%

Vapor–liquid partitioning of alkaline earth and transition metals in NaCl-dominated hydrothermal fluids: An experimental study from 360 to 465 °C, near-critical to halite saturated conditions

Pester

Ding

Seyfried

2015

Geochimica et Cosmochimica Acta

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“…In addition to fluid-rock interactions, phase separation of hydrothermal fluid influences the chemical and isotopic flux of dissolved components to the seafloor (Von Damm, 1995Damm, , 2004. Elemental partitioning and isotopic fractionation at pressure-temperature conditions representative of natural hydrothermal systems have been previously studied experimentally for a range of transition metals, alkali and alkali earth elements (Berndt et al, 1996;Heinrich et al, 1999;Liebscher et al, 2005Liebscher et al, , 2006Foustoukos and Seyfried, 2007b;Rempel et al, 2012;Pokrovski et al, 2013;Syverson et al, 2014;Pester et al, 2015). These studies provide the solubility and isotopic constraints necessary to interpret field data taken from two-phase submarine (Foustoukos et al, 2004;Rouxel et al, 2004Rouxel et al, , 2008 and subaerial (Simmons and Brown, 2006;Hardardó ttir et al, 2009) hydrothermal systems, while also serving as independent checks on first principle calculations of isotopic fractionation (Anbar et al, 2005;Chialvo and Horita, 2009;Rustad et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

“…These studies provide the solubility and isotopic constraints necessary to interpret field data taken from two-phase submarine (Foustoukos et al, 2004;Rouxel et al, 2004Rouxel et al, , 2008 and subaerial (Simmons and Brown, 2006;Hardardó ttir et al, 2009) hydrothermal systems, while also serving as independent checks on first principle calculations of isotopic fractionation (Anbar et al, 2005;Chialvo and Horita, 2009;Rustad et al, 2010). Additionally, isotopic studies of twophase fluid systems are useful to identify changes in aqueous speciation between vapor and liquid, given that, for many elements, the bonding and coordination environment in either phase often prefers one isotope relative to others (Liebscher et al, 2005(Liebscher et al, , 2006Rempel et al, 2012;Syverson et al, 2014). For example, Syverson et al (2014) proposed that Fe isotope fractionation was caused by two distinct Fe species, [FeCl 2 (H 2 O) 2 ] 0 and [FeCl 4 ] 2À , coexisting in the vapor and liquid, respectively.…”

Section: Introductionmentioning

confidence: 99%

Calcium isotope systematics at hydrothermal conditions: Mid-ocean ridge vent fluids and experiments in the CaSO4-NaCl-H2O system

Scheuermann

Syverson

Higgins

et al. 2018

Geochimica et Cosmochimica Acta

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Two sets of hydrothermal experiments were performed to explore Ca isotope fractionation and exchange rates at hydrothermal conditions (410-450°C, 31.0-50.0 MPa). The first set of experiments determined the magnitude of vaporliquid Ca isotope fractionation and anhydrite solubility in the CaSO 4 -NaCl-H 2 O system. The data indicate no statistical difference between the Ca isotopic composition of coexisting vapor and liquid. The second set of experiments utilized an anomalous 43 Ca spike to determine the rate of Ca exchange between fluid and anhydrite as a function of total dissolved Ca concentration. Results show that the rate of exchange increases with dissolved Ca concentrations (12-23 mM/kg), but no change in exchange rate is observed when the Ca concentration increases from 23 to 44 mM/kg Ca. 74-142 days are required to achieve 90% anhydrite-fluid Ca isotope exchange at the conditions investigated, while only several hours are necessary for vapor-liquid isotopic equilibrium. The lack of vapor-liquid Ca isotope fractionation in our experiments is consistent with d 44 Ca of mid-ocean ridge hydrothermal vent fluids that remain constant, regardless of chlorinity. Moreover, the narrow range of end member fluid d 44 Ca, À0.98 to À1.13‰ (SW), is largely indistinguishable from MORB d 44 Ca, suggesting that neither phase separation nor fluid-rock interactions at depth significantly fractionate Ca isotopes in modern high-temperature midocean ridge hydrothermal systems.

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“…During the fluid phase separation period, the gas phase depleted in Cl was likely enriched in heavy Fe isotopes. 0 preferentially entered the gas phase [63]. Theoretical calculations indicated that the degree of Fe isotope fractionation caused by the difference between the coordination chemistry of Fe-Cl and Fe-H 2 O complexes is likely caused by an oxidization-reduction effect [81].…”

Section: Phase Separation Of Hydrothermal Fluidsmentioning

confidence: 99%

“…Previous studies included simulated experiments on variations in the Fe isotope compositions of hydrothermal fluid systems during the phase separation period at seafloor hydrothermal vents within a temperature range of 424 to 466 ∘ C and a pressure range of 35.2 to 24.7 MPa [63]. When the solution system did not exhibit phase separation, the 56 Fe value was −0.29 ± 0.03‰ (2 ).…”

Section: Phase Separation Of Hydrothermal Fluidsmentioning

confidence: 99%

Fe Isotopic Compositions of Modern Seafloor Hydrothermal Systems and Their Influence Factors

Wang

2017

Journal of Chemistry

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Based on previous research on the Fe isotope compositions of various components and systems of the Earth, this study focused on the Fe isotope compositions of hydrothermal systems, including the Fe isotope variations in chalcopyrite, pyrite, and sphalerite, and their possible controlling factors. The main findings are as follows: (1) 56 Fe values of pyrite/marcasite display a larger range than those of chalcopyrite. This pattern is directly related to equilibrium fractionation or kinetic fractionation of Fe isotopes during the deposition of sulfides. To better understand the Fe isotope compositions of modern seafloor hydrothermal systems, the geochemical behavior and fractionation mechanisms of Fe isotopes require further in situ study.

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Fe isotope fractionation during phase separation in the NaCl–H2O system: An experimental study with implications for seafloor hydrothermal vents

Cited by 24 publications

References 52 publications

Vapor–liquid partitioning of alkaline earth and transition metals in NaCl-dominated hydrothermal fluids: An experimental study from 360 to 465 °C, near-critical to halite saturated conditions

Vapor–liquid partitioning of alkaline earth and transition metals in NaCl-dominated hydrothermal fluids: An experimental study from 360 to 465 °C, near-critical to halite saturated conditions

Calcium isotope systematics at hydrothermal conditions: Mid-ocean ridge vent fluids and experiments in the CaSO4-NaCl-H2O system

Fe Isotopic Compositions of Modern Seafloor Hydrothermal Systems and Their Influence Factors

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