Stable strontium isotope fractionation in synthetic barite

Widanagamage, Inoka H.; Schauble, E. A.; Scher, Howie D.; Griffith, Elizabeth M.

doi:10.1016/j.gca.2014.10.004

Cited by 47 publications

(51 citation statements)

References 75 publications

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“…Results from abiotic barite precipitation experiments have shown that barite preferentially incorporates the light isotopes of Sr during precipitation from solution, in agreement with previous work on stable metal isotopes in barite and other solids (e.g., calcium stable isotopes) and Density Functional Theory modeling calculations (Widanagamage et al, 2014). The experimental work also reveals that Sr-isotope fractionation is likely controlled by chemical kinetic effects primarily because at higher temperatures barite was more fractionated from the solution opposite to what equilibrium conditions would predict.…”

Section: Introductionsupporting

confidence: 88%

“…The experimental work also reveals that Sr-isotope fractionation is likely controlled by chemical kinetic effects primarily because at higher temperatures barite was more fractionated from the solution opposite to what equilibrium conditions would predict. Barite saturation state was also found to influence Sr-isotope fractionation (Widanagamage et al, 2014). This initial published work demonstrated that stable Sr-isotope ratios in barite are variable and could be useful in revealing conditions during precipitation such as abiotic processes including changes in temperature and/or solution chemistry and processes associated with biological activity if unique isotopic fractionation factors can be identified.…”

Section: Introductionmentioning

confidence: 96%

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Controls on stable Sr-isotope fractionation in continental barite

et al. 2015

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Barite precipitation typically occurs when barium rich fluids mix with sulfate rich fluids, however barite found in the modern continental environment suggests that biological activity can play an important role in barite formation by oxidizing sulfur and/or concentrating barium within microenvironments. These activities induce barite precipitation, and carry with them implications for studies of barite genesis. Strontium (Sr) is incorporated into the barite crystal structure during barite formation preserving a radiogenic and stable Sr-isotope signature in barite, providing information about its formation. Here we present Sr-isotope results from three artesian sulfidic springs with ongoing barite precipitation (Zodletone Spring, Oklahoma; Stinking Spring, Utah; and Doughty Springs, Colorado) to explore the controls on stable Sr-isotope fractionation during barite precipitation in a continental setting. Apparent stable Sr-isotope fractionation for all three sites ranged from −0.6‰ to~0.0‰ similar to previously published calculated values for equilibrium conditions and measured values of synthetic barite. However, clear relationships do not exist between water and barite chemistry in the natural systems, indicating that barite does not precipitate directly from solution, but heterogeneously within diverse microenvironments created by microbial biomass or on sediment surfaces. The dynamic microenvironments in a continental setting influence the apparent stable Sr-isotope fractionation during barite precipitation because of changing saturation conditions, Sr concentration and/or precipitation of different mineral phases (e.g., celestine). In order to better understand the geochemistry of barite deposits, future work is necessary to study the controls on radiogenic and stable Sr-isotope signatures of barite in the context of the temporally and spatially dynamic nature of the continental setting.

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Section: Introductionsupporting

confidence: 88%

Section: Introductionmentioning

confidence: 96%

Controls on stable Sr-isotope fractionation in continental barite

et al. 2015

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“…Equilibrium isotopic fractionation factors calculation is based on the knowledge of vibrational frequencies. Several studies rescaled the calculated harmonic frequencies to match the experimental ones (Schauble et al, 2006;Blanchard et al, 2009;Schauble, 2011;Widanagamage et al, 2014). This approach allows to obtain a better agreement between calculated and experimental frequencies, however, it may be hampered by either the lack of experimental vibrational spectra or an uncertain assignment of calculated and experimental vibrational modes.…”

Section: Resultsmentioning

confidence: 99%

Equilibrium zinc isotope fractionation in Zn-bearing minerals from first-principles calculations

2016

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Isotopic composition analysis contributes significantly to the investigation of the biogeochemical cycle of zinc with its economical, environmental and health implications. Interpretation of isotopic measurements is however hindered by the lack of a set of equilibrium isotopic fractionation factors between Zn-bearing minerals. In this study, equilibrium mass-dependent Zn isotope fractionation factors in Zn-bearing minerals are determined from first-principles calculations within the density functional theory (DFT) scheme. A wide range of minerals belonging to sulfide, carbonate, oxide, silicate, sulfate and arsenate mineral groups are modelled to account for the natural diversity of Zn crystal-chemical environment. Calculated reduced partition function ratios (β-factors) span a range smaller than 2 at 22 • C. All studied secondary minerals (adamite, gahnite, gunningite, hemimorphite, hydrozincite, zincite) but zinc carbonate (smithsonite) are isotopically heavier than zinc sulfide minerals (sphalerite and wurtzite) from which they could form through supergene processes. Zinc-aluminium spinel and zinc silicate are the isotopically heaviest minerals. The investigation of the crystalchemical parameters at the origin of differences in isotopic properties shows an excellent linear correlation between ln β and Zn interatomic force constants. β-factors are also observed to increase when the Zn-first neighbour bond lengths decrease and charges on atoms involved in the bonding increase and vice versa. These findings are in line with the observation of heavy isotope enrichment in systems having the largest bond strength.

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“…Modern seawater contains $28 mmol/kg of dissolved sulfate, whereas sulfate concentrations in endmember hydrothermal fluids are generally near zero as a result of precipitation of anhydrite within the crust and the thermo-chemical reduction of remaining sulfate during high-temperature reactions with basalt (Seyfried et al, 2003;Halevy et al, 2012). In contrast to anhydrite, which is unstable and will dissolve at ambient seafloor temperatures, barite has extremely low solubility in seawater and behaves as a closed system under typical oxic seafloor conditions, and is not prone to diagenetic alteration (Averyt and Paytan, 2003, and references therein; Widanagamage et al, 2014). Barite can thus preserve geochemical and morphological features associated with initial conditions of crystallization long after hydrothermal venting has ceased, and the occurrence, and crystallographic and geochemical properties of barite can provide insights into fluid mixing and the physicochemical conditions that drive mineral precipitation within the walls of hydrothermal chimneys.…”

Section: +mentioning

confidence: 99%

“…Laboratory growth experiments have linked barite crystal morphology to crystal growth rates and the degree of supersaturation of Ba 2+ and SO 4 2À in the crystallizing fluid (Shikazono, 1994;Judat and Kind, 2004;Li et al, 2007;Widanagamage et al, 2014). Dendritic crystals grow quickly as a result of diffusion-limited aggregation of solute atoms from highly supersaturated fluids (Turcotte, 1997).…”

Section: Crystal Morphologymentioning

confidence: 99%

Precipitation and growth of barite within hydrothermal vent deposits from the Endeavour Segment, Juan de Fuca Ridge

Jamieson

Hannington

Tivey

et al. 2016

Geochimica et Cosmochimica Acta

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Hydrothermal vent deposits form on the seafloor as a result of cooling and mixing of hot hydrothermal fluids with cold seawater. Amongst the major sulfide and sulfate minerals that are preserved at vent sites, barite (BaSO 4 ) is unique because it requires the direct mixing of Ba-rich hydrothermal fluid with sulfate-rich seawater in order for precipitation to occur. Because of its extremely low solubility, barite crystals preserve geochemical fingerprints associated with conditions of formation. Here, we present data from petrographic and geochemical analyses of hydrothermal barite from the Endeavour Segment of the Juan de Fuca Ridge, northeast Pacific Ocean, in order to determine the physical and chemical conditions under which barite precipitates within seafloor hydrothermal vent systems. Petrographic analyses of 22 barite-rich samples show a range of barite crystal morphologies: dendritic and acicular barite forms near the exterior vent walls, whereas larger bladed and tabular crystals occur within the interior of chimneys. A two component mixing model based on Sr concentrations and 87 Sr/ 86 Sr of both seawater and hydrothermal fluid, combined with 87 Sr/ 86 Sr data from whole rock and laser-ablation ICP-MS analyses of barite crystals indicate that barite precipitates from mixtures containing as low as 17% and as high as 88% hydrothermal fluid component, relative to seawater. Geochemical modelling of the relationship between aqueous species concentrations and degree of fluid mixing indicates that Ba 2+ availability is the dominant control on mineral saturation. Observations combined with model results support that dendritic barite forms from fluids of less than 40% hydrothermal component and with a saturation index greater than $0.6, whereas more euhedral crystals form at lower levels of supersaturation associated with greater contributions of hydrothermal fluid. This document is a U.S. government work and is not subject to copyright in the United States.from cyclical oscillations in hydrothermal fluid flux. Barite chemistry and morphology can be used as a reliable indicator for past conditions of mineralization within both extinct seafloor hydrothermal deposits and ancient land-based volcanogenic massive sulfide deposits.

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Stable strontium isotope fractionation in synthetic barite

Cited by 47 publications

References 75 publications

Controls on stable Sr-isotope fractionation in continental barite

Controls on stable Sr-isotope fractionation in continental barite

Equilibrium zinc isotope fractionation in Zn-bearing minerals from first-principles calculations

Precipitation and growth of barite within hydrothermal vent deposits from the Endeavour Segment, Juan de Fuca Ridge

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