Controls on stable Sr-isotope fractionation in continental barite

Widanagamage, Inoka H.; Griffith, Elizabeth M.; Singer, David M.; Scher, Howie D.; Buckley, Wayne; Senko, John M.

doi:10.1016/j.chemgeo.2015.07.011

Cited by 19 publications

(27 citation statements)

References 57 publications

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“…This indicates that the natural warm Variations in barite crystal morphologies are commonly controlled by the initial solution conditions from which the mineral is precipitated [28][29][30]33]. Rosette-like barite crystals like those that we identified in our experiments are commonly observed in warm springs [12,18]. The euhedral crystals were formed at higher temperatures (40 • C), which might have increased the diffusion rate of solutes and the kinetic energy of the molecules and thus changed precipitation conditions, resulting in the formation of a new crystal shape ( Figure 1D).…”

Section: Resultssupporting

confidence: 60%

“…Cold experiments (5 • C) were conducted in a refrigerator, and warm experiments (40 • C) were performed on top of a hot plate; the temperature of the experimental solution was controlled using a thermometer. In addition, Sr/Ba ratio of the initial solution was changed to 5 and 15 based on previous studies and previously published data considering natural environmental conditions in which barite precipitates in warm springs [12,30]. After precipitation, the solutions were filtered using 0.2 µm nitrocellulose membranes and air-dried.…”

Section: Experimental Designmentioning

confidence: 99%

“…Our observations revealed that rather than the Ba 2+ /SO 4 2− ratio, the Sr/Ba ratios in the solution and, to a lesser extent, the temperature were the factors that most strongly influenced barite crystal morphology. Temperature plays an important role in chemical kinetics [9,12,28]. Mobility of ions and the rate of diffusion of ions correlated with the temperature of the solution.…”

Section: −mentioning

confidence: 99%

“…In order to provide meaningful interpretations of geologically ancient environments that are associated with barite occurrences, we frequently use modern environments as analog systems. Within modern natural settings, barite will precipitate in any environment (e.g., marine, hydrothermal, continental) when barium-rich fluids mix with sulfate-rich anoxic solutions (e.g., brines) in the presence of sufficient concentrations of barium and sulfate ions [5,[8][9][10][11][12]. Additionally, barite will precipitate in biologically maintained environments [3,8,13].…”

Section: Introductionmentioning

confidence: 99%

“…Modern continental warm springs are not extensively studied but show that barite crystal morphologies may vary from irregular dendritic, prism-like, and needle-like to rosette crystals [12,18]. Continental spring parameters change temporally and spatially (e.g., wet and dry season, degassing of deep-sourced fluids, turbulent mixing), creating diverse barite crystal morphologies.…”

Section: Introductionmentioning

confidence: 99%

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Controls on Barite Crystal Morphology during Abiotic Precipitation

2018

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Barite (BaSO4) is a stable and widely distributed mineral in Earth’s crust. As such, barite has the potential to preserve specific geochemical and morphological characteristics representative of conditions at the time of its formation, which could be useful for interpretations of Earth’s ancient rocks and paleoenvironments. In this study, we used variations in saturation index, solution temperature, solution chemistry, presence of organics, and Mg2+ and Ca2+ ions to investigate variations in barite crystal morphology. Through 42 experiments, we simulated poorly understood, low temperature spring settings similar to Zodletone Spring in Anadarko Basin, Oklahoma. Using SEM/EDS, we identified barite rosettes, rounded barite, euhedral/square-shaped barite, and elliptical barite as the crystal morphologies that directly reflect different formational settings. The X-ray diffraction (XRD) patterns revealed different crystallographic characters of the four distinct barite crystal morphologies; in particular, the samples that precipitated from supersaturated SrSO4 solution exhibited double peaks at 43° 2-Theta, which matched barite with strontium substitution as barite might have incorporated strontium in its structure. Barite crystals that formed in the presence of organics in the initial solution exhibited a double peak at 33° 2-Theta, which was absent in other samples. Confocal Raman microscopy indicated that all of the samples had typical barium sulfate bands, with a few differences in bands between the samples; for example, the 638 cm−1 band showed splitting or a double band between different samples. The samples that precipitated from solution with organics had organic compounds from the experimental solution included in their composition. In both cases, C–H stretches from 2800 cm−1 to 3000 cm−1 were present as well as bands from 1350 cm−1 to 1500 cm−1, which are typical of organic compounds. Based on our experiments, the variation in barite crystal morphologies reflected changes in initial solution chemistry (or environmental settings).

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