Ca isotopes in carbonate sediment and pore fluid from ODP Site 807A: The Ca2+(aq)–calcite equilibrium fractionation factor and calcite recrystallization rates in Pleistocene sediments

Fantle, Matthew S.; DePaolo, Donald J.

doi:10.1016/j.gca.2007.03.006

Cited by 284 publications

(342 citation statements)

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“…This assumption is supported by inferred rates of carbonate precipitation in deep-sea sediments (~10 -19 mol/m 2 /sec; Fantle and DePaolo, 2007), which is orders of magnitude lower than previously estimated rates (~10 -12 mol/m 2 /sec) required to form carbonate minerals in carbon, oxygen, and clumped isotopic equilibrium with water regardless of the temperature or pH of the system (Watkins et al, 2013;Watkins et al, 2014;Watkins and Hunt, 2015).…”

Section: Background For Deep-sea Sedimentsmentioning

confidence: 57%

“…2; Schrag et al, 1992;Schrag et al, 1995 A1). This site was chosen, in part, because it has been used in numerous previous studies on the effects of diagenesis on the concentrations and isotopic composition of strontium (Fantle and DePaolo, 2006), calcium (Fantle and DePaolo, 2007), and magnesium (Higgins and Schrag, 2012) in carbonates and pore fluids as well as  18 O carb values (Schrag et al, 1995). All diagenetic models imply substantial amounts of recrystallization occurred at site 807.…”

Section: Model Predictions For Shallow Sedimentsmentioning

confidence: 99%

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Modeling the effects of diagenesis on carbonate clumped-isotope values in deep- and shallow-water settings

Stolper

Eiler

Higgins

2018

Geochimica et Cosmochimica Acta

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This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. O values provides new constraints on both the diagenetic history of deep-sea settings as well as past equatorial sea-surface temperatures. Specifically, the combination of the diagenetic model and data support previous work that indicates equatorial sea-surface temperatures were warmer in the Paleogene as compared to today. We then explore whether the model is applicable to shallow-water settings commonly preserved in the rock record. Using a previously published dataset from the Bahamas, we demonstrate that the model captures the main trends of the data as a function of burial depth and thus appears applicable to a range of depositional settings.

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Section: Background For Deep-sea Sedimentsmentioning

confidence: 57%

Section: Model Predictions For Shallow Sedimentsmentioning

confidence: 99%

Modeling the effects of diagenesis on carbonate clumped-isotope values in deep- and shallow-water settings

Stolper

Eiler

Higgins

2018

Geochimica et Cosmochimica Acta

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“…2), suggesting that variation in δ 44∕40 Ca does not simply reflect differences among facies in either primary fractionation of calcium isotopes or later diagenetic alteration. Finally, similar to the δ 13 C of carbonate rocks, there is far more calcium in the mineral than the pore fluids, helping buffer the δ 44∕40 Ca of carbonate minerals against alteration during burial diagenesis (40).…”

Section: Resultsmentioning

confidence: 96%

“…Isotopes of calcium are fractionated during the precipitation of calcium carbonate (25)(26)(27): 40 Ca is preferentially incorporated into the solid phase, leaving seawater enriched in 44 Ca at steady state relative to the delivery and burial fluxes (24,28). Consequently, scenarios that require imbalances between the delivery and burial fluxes of calcium in the oceans should impart changes in the calcium isotope composition in the oceans and associated sediments.…”

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confidence: 99%

Calcium isotope constraints on the end-Permian mass extinction

Payne

Turchyn

Paytan

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

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217

164

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The end-Permian mass extinction horizon is marked by an abrupt shift in style of carbonate sedimentation and a negative excursion in the carbon isotope (δ 13 C) composition of carbonate minerals. Several extinction scenarios consistent with these observations have been put forward. Secular variation in the calcium isotope (δ 44∕40 Ca) composition of marine sediments provides a tool for distinguishing among these possibilities and thereby constraining the causes of mass extinction. Here we report δ 44∕40 Ca across the Permian-Triassic boundary from marine limestone in south China. The δ 44∕40 Ca exhibits a transient negative excursion of ∼0.3‰ over a few hundred thousand years or less, which we interpret to reflect a change in the global δ 44∕40 Ca composition of seawater. CO 2 -driven ocean acidification best explains the coincidence of the δ 44∕40 Ca excursion with negative excursions in the δ 13 C of carbonates and organic matter and the preferential extinction of heavily calcified marine animals. Calcium isotope constraints on carbon cycle calculations suggest that the average δ 13 C of CO 2 released was heavier than −28‰ and more likely near −15‰; these values indicate a source containing substantial amounts of mantle-or carbonatederived carbon. Collectively, the results point toward Siberian Trap volcanism as the trigger of mass extinction.

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“…Synthetically precipitated and natural samples of calcite and aragonite are fractionated relative to aqueous Ca 2+ such that δ 44/40 Ca in calcite is lower by 0.5-2‰ (7,11). Equilibrium Ca isotope fractionation between Ca 2+ (aq) and calcite has not been measured in the laboratory, but studies of deep-sea sedimentary pore fluids suggest that the equilibrium fractionation is negligible: ε eq ∼ 0.0 ± 0.1‰ (12). Growth of calcite from seawater-like aqueous solutions is not likely to be diffusion-limited for Ca, so the isotopic effects are inferred to be due to kinetic effects occurring at the solid/fluid interface (11,13).…”

mentioning

confidence: 99%

Ion desolvation as a mechanism for kinetic isotope fractionation in aqueous systems

Hofmann

Bourg

DePaolo

2012

Proc. Natl. Acad. Sci. U.S.A.

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Molecular dynamics simulations show that the desolvation rates of isotopes of Li + , K + , Rb + , Ca 2+ , Sr 2+ , and Ba 2+ may have a relatively strong dependence on the metal cation mass. This inference is based on the observation that the exchange rate constant, k wex , for water molecules in the first hydration shell follows an inverse power-law mass dependence (k wex ∝ m −γ ), where the coefficient γ is 0.05 ± 0.01 on average for all cations studied. Simulated waterexchange rates increase with temperature and decrease with increasing isotopic mass for each element. The magnitude of the water-exchange rate is different for simulations run using different water models [i.e., extended simple point charge (SPC/E) vs. four-site transferrable intermolecular potential (TIP4P)]; however, the value of the mass exponent γ is the same. Reaction rate theory calculations predict mass exponents consistent with those determined via molecular dynamics simulations. The simulation-derived mass dependences imply that solids precipitating from aqueous solution under kinetically controlled conditions should be enriched in the light isotopes of the metal cations relative to the solutions, consistent with measured isotopic signatures in natural materials and laboratory experiments. Desolvation effects are large enough that they may be a primary determinant of the observed isotopic fractionation during precipitation.aqueous geochemistry | kinetic isotope effect | ligand exchange N onequilibrium processes are generally recognized as important influences on isotopic fractionation during mineral precipitation, especially at temperatures below a few hundred degrees Celsius (1, 2). Recent work in "nontraditional" stable isotopes (Li, Mg, Ca, Fe, Cd, Cu, etc.) has confirmed this inference and shown that nonequilibrium fractionation must be accounted for to understand global biogeochemical cycles involving these elements (2-5). A key observation is that light isotopes are preferentially incorporated into precipitating solids (6-8)-the opposite direction of enrichment expected for equilibrium fractionation, which depends on bond energetics (9, 10). The origin of this nonequilibrium light-isotope enrichment is a key unknown in the isotopic geochemistry of mineral growth.Calcite grown from aqueous solutions provides an excellent illustration of light-isotope enrichment during precipitation. Synthetically precipitated and natural samples of calcite and aragonite are fractionated relative to aqueous Ca 2+ such that δ 44/40 Ca in calcite is lower by 0.5-2‰ (7, 11). Equilibrium Ca isotope fractionation between Ca 2+ (aq) and calcite has not been measured in the laboratory, but studies of deep-sea sedimentary pore fluids suggest that the equilibrium fractionation is negligible: ε eq ∼ 0.0 ± 0.1‰ (12). Growth of calcite from seawater-like aqueous solutions is not likely to be diffusion-limited for Ca, so the isotopic effects are inferred to be due to kinetic effects occurring at the solid/fluid interface (11, 13). Diffusion in liquid water can r...

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Ca isotopes in carbonate sediment and pore fluid from ODP Site 807A: The Ca2+(aq)–calcite equilibrium fractionation factor and calcite recrystallization rates in Pleistocene sediments

Cited by 284 publications

References 53 publications

Modeling the effects of diagenesis on carbonate clumped-isotope values in deep- and shallow-water settings

Modeling the effects of diagenesis on carbonate clumped-isotope values in deep- and shallow-water settings

Calcium isotope constraints on the end-Permian mass extinction

Ion desolvation as a mechanism for kinetic isotope fractionation in aqueous systems

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