The transformation of aragonite to calcite in the presence of magnesium: Implications for marine diagenesis

Hashim, Mohammed S.; Kaczmarek, Stephen E.

doi:10.1016/j.epsl.2021.117166

Cited by 28 publications

(8 citation statements)

References 39 publications

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“…This allows Mg to be incorporated more easily into protodolomite, which is reflected in an increase in reaction rate and stoichiometry (mol% MgCO 3 ). The hydration of Mg ions has long been considered a kinetic inhibitor in the formation of dolomite and calcite alike (Bischoff, 1968; Lippmann, 1973; de Leeuw & Parker, 2001; Jones & Xiao, 2005; Fenter et al ., 2007; Vandeginste et al ., 2019; Hashim & Kaczmarek, 2021b; Aufort et al ., 2022; Mills et al ., 2022). In the case of dolomite, strong Mg hydration renders adsorption onto growth surfaces and incorporation into the crystal lattice difficult (Lippmann, 1973).…”

Section: Discussionmentioning

confidence: 99%

“…4G and F), suggesting that more Na is incorporated into dolomite when its concentration in the solution is higher. This is in general agreement with numerous studies showing that the amount of a trace element incorporated into a carbonate mineral correlates positively with its concentration in the parent solution (Mucci & Morse, 1983; Morse & Bender, 1990; Alvarez et al ., 2021; Hashim & Kaczmarek, 2021b).…”

Section: Discussionmentioning

confidence: 99%

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Effects of sodium and potassium concentrations on dolomite formation rate, stoichiometry and crystallographic characteristics

et al. 2023

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This study uses high temperature (215°C) dolomitization experiments to explore the effects of sodium (Na) and potassium (K), two common constituents of natural fluids, on dolomite formation rate, stoichiometry and crystallographic characteristics. In these experiments, aragonite ooids were dolomitized in Mg–Ca–Cl solutions with either no additional salt, or in solutions containing NaCl or KCl at different concentrations. Results show that Na solutions, and to a lesser extent K solutions, correlate with faster reaction rates and that Na at hypersaline fluid concentrations produces dolomites with higher stoichiometry, higher micro‐strain and lower cation ordering. Potassium has a different effect on the dolomite than Na at similar concentrations. Unlike Na, K does not cause micro‐strain but leads to dolomite with smaller unit cell parameters. It is proposed that Na and K catalyse dolomite precipitation and increase stoichiometry by weakening Mg hydration bonds which consequently facilitates Mg incorporation into dolomite. The decrease in dolomite cation ordering at higher Na concentrations may stem from the incorporation of Na into dolomite which strains the crystal lattice and reduces cation order. On the basis that high‐temperature experiments are applicable to natural dolomites, several implications pertinent to natural dolomites are drawn from the results. Firstly, the data suggest that the higher concentrations of Na and K in evaporative fluids (i.e. higher salinity) can explain why dolomite is generally more abundant and more stoichiometric in evaporative settings. Secondly, the results challenge a key prediction of the mixing zone dolomitization model by showing that higher Na and K concentrations increase, rather than decrease, both dolomitization rate and stoichiometry. Thirdly, the observed decrease in dolomite cation ordering with increasing Na and K concentrations implies that evaporative fluids would produce less stable dolomite that may be more prone to subsequent recrystallization and thus resetting of primary geochemical signatures.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Effects of sodium and potassium concentrations on dolomite formation rate, stoichiometry and crystallographic characteristics

et al. 2023

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“…An explanation for the LMC might be that aragonite and HMC are metastable and even under conditions of low undersaturation, aragonite and HMC tend to dissolve and reprecipitate (Gomberg & Bonatti, 1970). However, the time span for the transition of HMC to LMC is not sufficient as this process probably happens during progressive burial, making this hypothesis rather improbable (Hashim & Kaczmarek, 2021). Furthermore, LMC does not precipitate directly from modern marine waters (Sandberg, 1983) due to the high-Mg/Ca ratio and high SO 4 2− concentrations (Bots et al, 2011).…”

Section: Lmc Cementsmentioning

confidence: 99%

Occurrence and Genesis of Cold‐Seep Authigenic Carbonates from the South‐Eastern Mediterranean Sea

Weidlich

Bialik

Rüggeberg

et al. 2023

The Depositional Record

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Methane‐derived authigenic seep carbonates occur globally along continental margins. These carbonates are important archives to identify seep dynamics, the source of the ascending methane‐enriched fluids together with their timing, and are an important carbon sequestration mechanism. Recently, seep carbonates were discovered in the Levant Basin in the South‐Eastern Mediterranean Sea. To elucidate past seepage activity and dynamics across the basin, different seep carbonate morphologies (chimneys, crusts and pavements) retrieved from the Levant Basin were mapped based on remotely operating vehicle data and analysed using standard sediment petrographic techniques, X‐ray diffraction and stable carbon and oxygen isotope analyses. Carbonate chimneys consist of micrite (δ13CVPDB of ‐10 to +5 ‰) with dispersed barite and dolomite crystals, fan‐shaped aragonite (δ13CVPDB of ‐52 to ‐30 ‰) and high‐magnesium calcite cements, with the latter often growing from low‐magnesium calcite spherules. Botryoidal low‐magnesium calcite cements are forming in small cavities. Carbonate crusts consist of micrite with low‐magnesium calcite breccias, high‐magnesium calcite nodules (δ13CVPDB of ‐35 to ‐20 ‰) and cements, and partially replaced fan‐shaped aragonite cements. Carbonate pavements consist of low‐magnesium calcite microsparite, micritic dolomite and high‐magnesium calcite. Fan‐shaped aragonite is locally present as pore‐lining cement. Iron‐oxides are often seen coating the low‐magnesium calcite, high‐magnesium calcite and dolomite cements. Chimneys and crusts, characterised by high amounts of high‐magnesium calcite and aragonite, are interpreted to have formed through advective methane fluxes. Pavements, with high quantities of dolomite, are explained as the product of diffusive methane flux. Sediment petrographic and geochemical analysis of the different carbonate morphologies and cement phases therein witness distinct modes of ascending fluid fluxes and their mixing with marine porewater and/or seawater during precipitation of the individual phases.

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“…Aragonite is an abundant carbonate mineral in modern shallow-marine sediments and was originally present in many Phanerozoic limestones ( Gischler et al, 2013 ; Hasim and Kaczmarek, 2019 , 2021 ). The precipitation of aragonite and hence abundance through time, however, does vary reflecting changes in the chemical composition of seawater, notably the Mg/Ca ratio, as well as the evolution and demise of skeletal organisms in their biomineralization ( Sandberg, 1975 , 1983 ; Balthasar and Cusack, 2015 ; Sun et al, 2015 ; Pederson et al, 2019 ; Hasim and Kaczmarek, 2021 ). The variation in seawater chemistry and hence aragonite vs. calcite precipitation is mostly controlled by geotectonic processes an rates of seafloor spreading.…”

Section: Introductionmentioning

confidence: 99%

The incorporation of Mg2+ ions into aragonite during biomineralization: Implications for the dolomitization of aragonite

et al. 2023

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Bacteria can facilitate the increase of Mg2+ content in biotic aragonite, but the molecular mechanisms of the incorporation of Mg2+ ion into aragonite facilitated by bacteria are still unclear and the dolomitization of aragonite grains is rarely reported. In our laboratory experiments, the content of Mg2+ ions in biotic aragonite is higher than that in inorganically-precipitated aragonite and we hypothesize that the higher Mg content may enhance the subsequent dolomitization of aragonite. In this study, biotic aragonite was induced by Bacillus licheniformis Y1 at different Mg/Ca molar ratios. XRD data show that only aragonite was precipitated in the media with Mg/Ca molar ratios at 6, 9, and 12 after culturing for 25 days. The EDS and atomic absorption results show that the content of Mg2+ ions in biotic aragonite increased with rising Mg/Ca molar ratios. In addition, our analyses show that the EPS from the bacteria and the organics extracted from the interior of the biotic aragonite contain the same biomolecules, including Ala, Gly, Glu and hexadecanoic acid. The content of Mg2+ ions in the aragonite precipitates mediated by biomolecules is significantly higher than that in inorganically-precipitated aragonite. Additionally, compared with Ala and Gly, the increase of the Mg2+ ions content in aragonite promoted by Glu and hexadecanoic acid is more significant. The DFT (density functional theory) calculations reveal that the energy needed for Mg2+ ion incorporation into aragonite mediated by Glu, hexadecanoic acid, Gly and Ala increased gradually, but was lower than that without acidic biomolecules. The experiments also show that the Mg2+ ion content in the aragonite significantly increased with the increasing concentration of biomolecules. In a medium with high Mg2+ concentration and with bacteria, after 2 months, micron-sized dolomite rhombs were precipitated on the surfaces of the aragonite particles. This study may provide new insights into the important role played by biomolecules in the incorporation of the Mg2+ ions into aragonite. Moreover, these experiments may contribute towards our understanding of the dolomitization of aragonite in the presence of bacteria.

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The transformation of aragonite to calcite in the presence of magnesium: Implications for marine diagenesis

Cited by 28 publications

References 39 publications

Effects of sodium and potassium concentrations on dolomite formation rate, stoichiometry and crystallographic characteristics

Effects of sodium and potassium concentrations on dolomite formation rate, stoichiometry and crystallographic characteristics

Occurrence and Genesis of Cold‐Seep Authigenic Carbonates from the South‐Eastern Mediterranean Sea

The incorporation of Mg2+ ions into aragonite during biomineralization: Implications for the dolomitization of aragonite

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