Effect of growth rate and pH on lithium incorporation in calcite

A. Füger, F. Konrad, A. Leis, M. Dietzel, V. Mavromatis

Publikation: Beitrag in einer FachzeitschriftArtikelForschungBegutachtung

Abstract

Carbonates are only a minor sink of oceanic lithium, yet the presence of this element and its abundance relative to other metal cations in natural carbonate minerals is routinely used as a paleo-environmental proxy. To date, however, experimental studies on the influence of physicochemical parameters that may control lithium incorporation in calcite, like pH and precipitation rate, are scarce. Therefore, we experimentally studied Li incorporation in calcite to quantify the apparent partitioning coefficient (DLi =[Formula presented]) between calcite and reactive fluid as a function of calcite growth rate and pH. The obtained results suggest that DLi increases with calcite growth rate, according to the expression: LogDLi =1.331(±0.116)×LogRate+6.371(±0.880)(R2=0.87;10-8.1≤Rate≤10-7.1molm-2s-1) Additionally the experimental results suggest that DLi values exhibit a strong pH dependence. For experiments conducted at similar growth rates (i.e. Rate = 10−7.7±0.2 mol m−2 s−1), DLi decreases with increasing pH as described by: LogDLi =-0.57(±0.047)×pH+0.759(±0.366)(R2=0.90;6.3<pH<9.5) The positive correlation of DLi with calcite growth rate is consistent with an increasing entrapment of traces/impurities at rapidly growing calcite surfaces, although the incorporation of monovalent cations such as Li+ and Na+ does not necessarily imply a substitution of Ca2+ ions in the calcite crystal lattice. The dependence of DLi on pH can be considered as an indication that activity of aqueous HCO3 controls the incorporation of Li+ in calcite. The proposed coupled reaction can be explained by charge balance of these monovalent species, which is likely valid at least during the initial step of adsorption on the crystal surface. These new findings shed light on the mechanisms controlling Li incorporation in calcite and have direct implications on the use of Li partitioning coefficients in natural carbonates as an environmental proxy.

Originalspracheenglisch
Seiten (von - bis)14-24
Seitenumfang11
FachzeitschriftGeochimica et Cosmochimica Acta
Jahrgang248
DOIs
PublikationsstatusVeröffentlicht - 1 Mär 2019

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Calcium Carbonate
lithium
Lithium
calcite
Carbonates
carbonate
partitioning
cation
incorporation
effect
Carbonate minerals
crystal
Monovalent Cations
Crystal lattices
Cations
relative abundance
substitution
Substitution reactions
experimental study
Metals

Schlagwörter

    ASJC Scopus subject areas

    • !!Geochemistry and Petrology

    Dies zitieren

    Effect of growth rate and pH on lithium incorporation in calcite. / Füger, A.; Konrad, F.; Leis, A.; Dietzel, M.; Mavromatis, V.

    in: Geochimica et Cosmochimica Acta, Jahrgang 248, 01.03.2019, S. 14-24.

    Publikation: Beitrag in einer FachzeitschriftArtikelForschungBegutachtung

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    abstract = "Carbonates are only a minor sink of oceanic lithium, yet the presence of this element and its abundance relative to other metal cations in natural carbonate minerals is routinely used as a paleo-environmental proxy. To date, however, experimental studies on the influence of physicochemical parameters that may control lithium incorporation in calcite, like pH and precipitation rate, are scarce. Therefore, we experimentally studied Li incorporation in calcite to quantify the apparent partitioning coefficient (DLi ∗=[Formula presented]) between calcite and reactive fluid as a function of calcite growth rate and pH. The obtained results suggest that DLi ∗ increases with calcite growth rate, according to the expression: LogDLi ∗=1.331(±0.116)×LogRate+6.371(±0.880)(R2=0.87;10-8.1≤Rate≤10-7.1molm-2s-1) Additionally the experimental results suggest that DLi ∗ values exhibit a strong pH dependence. For experiments conducted at similar growth rates (i.e. Rate = 10−7.7±0.2 mol m−2 s−1), DLi ∗ decreases with increasing pH as described by: LogDLi ∗=-0.57(±0.047)×pH+0.759(±0.366)(R2=0.90;6.3Li ∗ with calcite growth rate is consistent with an increasing entrapment of traces/impurities at rapidly growing calcite surfaces, although the incorporation of monovalent cations such as Li+ and Na+ does not necessarily imply a substitution of Ca2+ ions in the calcite crystal lattice. The dependence of DLi ∗ on pH can be considered as an indication that activity of aqueous HCO3 − controls the incorporation of Li+ in calcite. The proposed coupled reaction can be explained by charge balance of these monovalent species, which is likely valid at least during the initial step of adsorption on the crystal surface. These new findings shed light on the mechanisms controlling Li incorporation in calcite and have direct implications on the use of Li partitioning coefficients in natural carbonates as an environmental proxy.",
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    TY - JOUR

    T1 - Effect of growth rate and pH on lithium incorporation in calcite

    AU - Füger, A.

    AU - Konrad, F.

    AU - Leis, A.

    AU - Dietzel, M.

    AU - Mavromatis, V.

    PY - 2019/3/1

    Y1 - 2019/3/1

    N2 - Carbonates are only a minor sink of oceanic lithium, yet the presence of this element and its abundance relative to other metal cations in natural carbonate minerals is routinely used as a paleo-environmental proxy. To date, however, experimental studies on the influence of physicochemical parameters that may control lithium incorporation in calcite, like pH and precipitation rate, are scarce. Therefore, we experimentally studied Li incorporation in calcite to quantify the apparent partitioning coefficient (DLi ∗=[Formula presented]) between calcite and reactive fluid as a function of calcite growth rate and pH. The obtained results suggest that DLi ∗ increases with calcite growth rate, according to the expression: LogDLi ∗=1.331(±0.116)×LogRate+6.371(±0.880)(R2=0.87;10-8.1≤Rate≤10-7.1molm-2s-1) Additionally the experimental results suggest that DLi ∗ values exhibit a strong pH dependence. For experiments conducted at similar growth rates (i.e. Rate = 10−7.7±0.2 mol m−2 s−1), DLi ∗ decreases with increasing pH as described by: LogDLi ∗=-0.57(±0.047)×pH+0.759(±0.366)(R2=0.90;6.3Li ∗ with calcite growth rate is consistent with an increasing entrapment of traces/impurities at rapidly growing calcite surfaces, although the incorporation of monovalent cations such as Li+ and Na+ does not necessarily imply a substitution of Ca2+ ions in the calcite crystal lattice. The dependence of DLi ∗ on pH can be considered as an indication that activity of aqueous HCO3 − controls the incorporation of Li+ in calcite. The proposed coupled reaction can be explained by charge balance of these monovalent species, which is likely valid at least during the initial step of adsorption on the crystal surface. These new findings shed light on the mechanisms controlling Li incorporation in calcite and have direct implications on the use of Li partitioning coefficients in natural carbonates as an environmental proxy.

    AB - Carbonates are only a minor sink of oceanic lithium, yet the presence of this element and its abundance relative to other metal cations in natural carbonate minerals is routinely used as a paleo-environmental proxy. To date, however, experimental studies on the influence of physicochemical parameters that may control lithium incorporation in calcite, like pH and precipitation rate, are scarce. Therefore, we experimentally studied Li incorporation in calcite to quantify the apparent partitioning coefficient (DLi ∗=[Formula presented]) between calcite and reactive fluid as a function of calcite growth rate and pH. The obtained results suggest that DLi ∗ increases with calcite growth rate, according to the expression: LogDLi ∗=1.331(±0.116)×LogRate+6.371(±0.880)(R2=0.87;10-8.1≤Rate≤10-7.1molm-2s-1) Additionally the experimental results suggest that DLi ∗ values exhibit a strong pH dependence. For experiments conducted at similar growth rates (i.e. Rate = 10−7.7±0.2 mol m−2 s−1), DLi ∗ decreases with increasing pH as described by: LogDLi ∗=-0.57(±0.047)×pH+0.759(±0.366)(R2=0.90;6.3Li ∗ with calcite growth rate is consistent with an increasing entrapment of traces/impurities at rapidly growing calcite surfaces, although the incorporation of monovalent cations such as Li+ and Na+ does not necessarily imply a substitution of Ca2+ ions in the calcite crystal lattice. The dependence of DLi ∗ on pH can be considered as an indication that activity of aqueous HCO3 − controls the incorporation of Li+ in calcite. The proposed coupled reaction can be explained by charge balance of these monovalent species, which is likely valid at least during the initial step of adsorption on the crystal surface. These new findings shed light on the mechanisms controlling Li incorporation in calcite and have direct implications on the use of Li partitioning coefficients in natural carbonates as an environmental proxy.

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    KW - Li partitioning

    KW - Mineral growth rate

    KW - Na partitioning

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