Observations on the Solubility of Skeletal Carbonates in Aqueous Solutions

Chave, Keith E.; Deffeyes, Kenneth S.; Weyl, Peter K.; Garrels, Robert M.; Thompson, Mary

doi:10.1126/science.137.3523.33

Cited by 146 publications

(57 citation statements)

References 9 publications

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“…The reduction in the d104 value is presumably due to the substitution of smaller size of Mg 2+ for Ca 2+ leading to a shrinkage in the calcite lattice. Compositions of the precipitated crystals calculated by the empirical curve from Zhang et al (2010) [23] using the d104 values showed that up to 19% of Mg 2+ was incorporate into calcite lattice ( Figure 9b, Table 2), almost doubling the reported theoretical maximum of ~10 mol % ( [24][25][26]). Mg content in the calcite grown on hematite in a solution with Mg/Ca ratio of 5:1 is slightly higher (~19 mol % to ~23 mol % of MgCO3) than that on biotite (Figure 10).…”

Section: Influence Of Mg 2+ On Epitaxial Growth Of Calcitementioning

confidence: 81%

Effect of Mica and Hematite (001) Surfaces on the Precipitation of Calcite

Zhou

Fang

et al. 2018

Minerals

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Abstract:The substrate effect of mica and hematite on the nucleation and crystallization of calcite was investigated using scanning electron microscope (SEM), X-ray diffraction (XRD), and electron backscatter diffraction (EBSD) methods. On mica, we found, in the absence of Mg 2+ , the substrates' (001) surfaces with hexagonal and pseudo-hexagonal two-dimensional (2-D) structure can affect the orientation of calcite nucleation with calcite (001)~// mica (001) and calcite (010)~// mica (010) to be the major interfacial relationship. On hematite, we did not observe frequent twinning relationship between adjacent calcite gains, but often saw preferentially nucleation of calcite at surface steps on hematite substrate. We suggest that calcite crystals initially nucleate from the Ca 2+ layers adsorbed on the surfaces. The pseudo-hexagonal symmetry on mica (001) surface also leads to the observed calcite (001) twinning. A second and less common orientation between calcite {104} and mica (001) was detected but could be due to local structure damage of the mica surface. Results in the presence of Mg 2+ show that the substrate surfaces can weaken Mg toxicity to calcite nucleation and lead to a higher level of Mg incorporation into calcite lattice.

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Section: Influence Of Mg 2+ On Epitaxial Growth Of Calcitementioning

confidence: 81%

Effect of Mica and Hematite (001) Surfaces on the Precipitation of Calcite

Zhou

Fang

et al. 2018

Minerals

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“…Higher Mg content in calcite increases its dissolution rate (Chave et al 1962, Rushdi et al 1998. The presence of relatively high Mg concentrations may explain, in addition to their microcristalline structure, the low preservation potential of holococcoliths, which have very sporadic fossil records (Bown et al 2004).…”

Section: Discussionmentioning

confidence: 99%

Elemental composition of coccoliths: Mg/Ca relationships

Cros¹,

Fortuño²,

Estrada³

2013

Sci. Mar.

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SUMMARY: Coccolithophores produce calcium carbonate platelets, the coccoliths, and play a significant role in the C and Ca cycles. Coccoliths are important components of marine biogenic carbonate sediments and their chemical analysis can provide tools for paleoceanographic investigation. In particular, the Mg/Ca ratio of coccoliths has been proposed as a paleotemperature proxy. The present study uses X-ray microanalysis to evaluate the Ca and Mg composition of heterococcoliths and holococcoliths of different coccolithophore species. Our measurements indicate that the Mg values in heterococcoliths do not exceed a low threshold and do not show any consistent relationship with the Ca content, while the Mg content of holococcoliths spans a wider range, can reach much higher values and shows a linear relationship with the Ca content. Several heterococcolithophore species tend to form separate clusters according to their Mg and Ca values. Within each cluster, there were no consistent differences in the Mg/Ca ratios of specimens sampled at different temperatures or seasons, suggesting that using the Mg/Ca ratio as a paleothermometer may be problematic. Our findings could have implications for the interpretation of the fossil record because Mg-rich calcite dissolves more easily.Keywords: coccolithophores, X-ray microanalysis, calcium, magnesium, holococcoliths, heterococcoliths. RESUMEN: ComposiCión elemental de CoColitos. RelaCiones mg/Ca. -Los cocolitóforos producen unas plaquitas de carbonato de calcio denominadas cocolitos, y juegan un papel significativo en los ciclos biogeoquímicos del C y el Ca. Los cocolitos constituyen un componente importante del registro sedimentario y su análisis químico puede proporcionar herramientas para la investigación paleoceanográfica. En particular, se ha sugerido que la relación Mg/Ca podría ser usada como un indicador de paleotemperatura. En este trabajo presentamos un estudio, realizado mediante la técnica de microanálisis por rayos X, de la composición elemental de holo-y heterococolitos pertenecientes a diferentes especies de cocolitóforos. Se ha observado que el contenido de Mg en los heterococolitos no supera un umbral muy bajo y no presenta relación con el de Ca, mientras que en los holococolitos el contenido de Mg es en general más elevado, abarca un rango más amplio y guarda una relación lineal con el de Ca. Diversas especies de heterococolitóforos tendían a formar grupos separados en función de su contenido en Ca y Mg. Dentro de cada especie, no se detectaban diferencias consistentes en la relación Mg/Ca de especímenes de muestras de agua de distintas temperaturas o tomadas en diferentes estaciones del año, lo que indica que el uso de la relación Mg/Ca como paleotermómetro puede ser problemático. Nuestras observaciones pueden tener implicaciones para la interpretación del registro sedimentario, ya que la calcita rica en Mg se disuelve más rápidamente.

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“…The algorithm was suggested by Carrels and Thompson (1962), and a refined and comprehensive version has been published by Truesdale and Jones (1974). Three types of equa- Table 3.…”

Section: Experimental Methodsmentioning

confidence: 99%

Polyphenol inhibition of calcite precipitation in Lake Powell 1

Reynolds

1978

Limnology & Oceanography

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Laboratory studies of calcite precipitation kinetics in waters of simulated Lake Powell composition have verified that precipitation occurs by a spiral dislocation growth mechanism. But waters from the lake and laboratory solutions containing tannic acid and plant polyphenols at low and very low levels showed calcite growth rates proportional to the fourth power of the carbonate ion concentration.The results indicate the operation of a surface polynuclear growth process that becomes effective when polyphenol adsorption blocks spiral dislocation growth sites and causes precipitation rates to diminish with increasing polyphenol concentration and to fall drastically as pH is lowered. The effects of these factors are dominant controls on the calcium carbonate geochemistry of Lake Powell. Significant amounts of calcite precipitation occur only in the surface waters of the downstream portion of the reservoir and, even there, only during the warm (6 months) portion of the year.

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Observations on the Solubility of Skeletal Carbonates in Aqueous Solutions

Cited by 146 publications

References 9 publications

Effect of Mica and Hematite (001) Surfaces on the Precipitation of Calcite

Effect of Mica and Hematite (001) Surfaces on the Precipitation of Calcite

Elemental composition of coccoliths: Mg/Ca relationships

Polyphenol inhibition of calcite precipitation in Lake Powell 1

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