Crystal growth rate effect on Mg/Ca and Sr/Ca partitioning between calcite and fluid: An in situ approach

R. I. Gabitov, A. Sadekov, A. Leinweber

Research output: Contribution to journalArticle

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Abstract

Partition coefficients of Mg and Sr (KMg and KSr) between calcite and fluid were determined in crystals grown under different rates (V), where V is defined as the crystal extension per unit of time (nm/s). Addition of rare earth elements (REE) into the fluid, leads to REE preservation in the calcite. This preservation allows for a direct determination of the values of V by measuring the widths of the REE spiked zones. The edge to edge spot analyses of Mg/Ca, Sr/Ca, and REE/Ca in the individual crystals were conducted using Secondary Ion Mass Spectrometry (SIMS). The Mg/Ca and Sr/Ca ratios in the fluids, from which calcites precipitated, were also measured with Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-OES). This allowed for the first time, to evaluate KMg in situ in the individual crystals without averaging the data from the multiple calcite crystals. Results show that KSr increases by a factor of six with increasing calcite growth rate from 0.001 to 4nm/s. KMg decreases by a factor of three with the same increase of V values. These KSr and KMg behaviors were described quantitatively using a growth entrapment model (GEM). According to the GEM simulations, Sr is enriched and Mg is depleted in the near-surface layer of calcite relative to the bulk lattice. This distinct outermost region of the crystal may be fully or partially captured by its lattice during rapid growth. This process causes disequilibrium partitioning of Sr and Mg through growth entrapment.

Original languageEnglish
Pages (from-to)70-82
Number of pages13
JournalChemical Geology
Volume367
DOIs
Publication statusPublished - 28 Feb 2014
Externally publishedYes

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Calcium Carbonate
Crystallization
calcite
partitioning
crystal
Rare earth elements
Crystals
Fluids
fluid
rare earth element
Atomic emission spectroscopy
atomic emission spectroscopy
Inductively coupled plasma
Secondary ion mass spectrometry
partition coefficient
Crystal lattices
disequilibrium
in situ
effect
surface layer

Cite this

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title = "Crystal growth rate effect on Mg/Ca and Sr/Ca partitioning between calcite and fluid: An in situ approach",
abstract = "Partition coefficients of Mg and Sr (KMg and KSr) between calcite and fluid were determined in crystals grown under different rates (V), where V is defined as the crystal extension per unit of time (nm/s). Addition of rare earth elements (REE) into the fluid, leads to REE preservation in the calcite. This preservation allows for a direct determination of the values of V by measuring the widths of the REE spiked zones. The edge to edge spot analyses of Mg/Ca, Sr/Ca, and REE/Ca in the individual crystals were conducted using Secondary Ion Mass Spectrometry (SIMS). The Mg/Ca and Sr/Ca ratios in the fluids, from which calcites precipitated, were also measured with Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-OES). This allowed for the first time, to evaluate KMg in situ in the individual crystals without averaging the data from the multiple calcite crystals. Results show that KSr increases by a factor of six with increasing calcite growth rate from 0.001 to 4nm/s. KMg decreases by a factor of three with the same increase of V values. These KSr and KMg behaviors were described quantitatively using a growth entrapment model (GEM). According to the GEM simulations, Sr is enriched and Mg is depleted in the near-surface layer of calcite relative to the bulk lattice. This distinct outermost region of the crystal may be fully or partially captured by its lattice during rapid growth. This process causes disequilibrium partitioning of Sr and Mg through growth entrapment.",
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Crystal growth rate effect on Mg/Ca and Sr/Ca partitioning between calcite and fluid : An in situ approach. / Gabitov, R. I.; Sadekov, A.; Leinweber, A.

In: Chemical Geology, Vol. 367, 28.02.2014, p. 70-82.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Crystal growth rate effect on Mg/Ca and Sr/Ca partitioning between calcite and fluid

T2 - An in situ approach

AU - Gabitov, R. I.

AU - Sadekov, A.

AU - Leinweber, A.

PY - 2014/2/28

Y1 - 2014/2/28

N2 - Partition coefficients of Mg and Sr (KMg and KSr) between calcite and fluid were determined in crystals grown under different rates (V), where V is defined as the crystal extension per unit of time (nm/s). Addition of rare earth elements (REE) into the fluid, leads to REE preservation in the calcite. This preservation allows for a direct determination of the values of V by measuring the widths of the REE spiked zones. The edge to edge spot analyses of Mg/Ca, Sr/Ca, and REE/Ca in the individual crystals were conducted using Secondary Ion Mass Spectrometry (SIMS). The Mg/Ca and Sr/Ca ratios in the fluids, from which calcites precipitated, were also measured with Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-OES). This allowed for the first time, to evaluate KMg in situ in the individual crystals without averaging the data from the multiple calcite crystals. Results show that KSr increases by a factor of six with increasing calcite growth rate from 0.001 to 4nm/s. KMg decreases by a factor of three with the same increase of V values. These KSr and KMg behaviors were described quantitatively using a growth entrapment model (GEM). According to the GEM simulations, Sr is enriched and Mg is depleted in the near-surface layer of calcite relative to the bulk lattice. This distinct outermost region of the crystal may be fully or partially captured by its lattice during rapid growth. This process causes disequilibrium partitioning of Sr and Mg through growth entrapment.

AB - Partition coefficients of Mg and Sr (KMg and KSr) between calcite and fluid were determined in crystals grown under different rates (V), where V is defined as the crystal extension per unit of time (nm/s). Addition of rare earth elements (REE) into the fluid, leads to REE preservation in the calcite. This preservation allows for a direct determination of the values of V by measuring the widths of the REE spiked zones. The edge to edge spot analyses of Mg/Ca, Sr/Ca, and REE/Ca in the individual crystals were conducted using Secondary Ion Mass Spectrometry (SIMS). The Mg/Ca and Sr/Ca ratios in the fluids, from which calcites precipitated, were also measured with Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-OES). This allowed for the first time, to evaluate KMg in situ in the individual crystals without averaging the data from the multiple calcite crystals. Results show that KSr increases by a factor of six with increasing calcite growth rate from 0.001 to 4nm/s. KMg decreases by a factor of three with the same increase of V values. These KSr and KMg behaviors were described quantitatively using a growth entrapment model (GEM). According to the GEM simulations, Sr is enriched and Mg is depleted in the near-surface layer of calcite relative to the bulk lattice. This distinct outermost region of the crystal may be fully or partially captured by its lattice during rapid growth. This process causes disequilibrium partitioning of Sr and Mg through growth entrapment.

KW - Calcite

KW - Equilibrium

KW - Growth rate

KW - Magnesium

KW - SIMS

KW - Strontium

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DO - 10.1016/j.chemgeo.2013.12.019

M3 - Article

VL - 367

SP - 70

EP - 82

JO - Chemical Geology

JF - Chemical Geology

SN - 0009-2541

ER -