An experimental study of magnesite precipitation rates at neutral to alkaline conditions and 100–200°C as a function of pH, aqueous solution composition and chemical affinity

Saldi, Giuseppe D.; Schott, Jacques; Pokrovsky, Oleg S.; Gautier, Quentin; Oelkers, Eric H.

doi:10.1016/j.gca.2011.12.005

Cited by 116 publications

(97 citation statements)

References 105 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The formation of such minerals occurs at lower rates compared to pure Cabearing carbonates owing to the slow dehydration of aqueous Mg that is required prior to its incorporation in the crystal (e.g. Mavromatis et al, 2013) even at temperature as high as 200 • C (Saldi et al, 2009(Saldi et al, , 2012.…”

Section: Grain Size and Chemistry Of The Newly Formed Calcitementioning

confidence: 99%

Experimental diagenesis: insights into aragonite to calcite transformation of <i>Arctica islandica</i> shells by hydrothermal treatment

Casella¹,

Griesshaber²,

Yin³

et al. 2017

Biogeosciences

View full text Add to dashboard Cite

Abstract. Biomineralised hard parts form the most important physical fossil record of past environmental conditions. However, living organisms are not in thermodynamic equilibrium with their environment and create local chemical compartments within their bodies where physiologic processes such as biomineralisation take place. In generating their mineralised hard parts, most marine invertebrates produce metastable aragonite rather than the stable polymorph of CaCO 3 , calcite. After death of the organism the physiological conditions, which were present during biomineralisation, are not sustained any further and the system moves toward inorganic equilibrium with the surrounding inorganic geological system. Thus, during diagenesis the original biogenic structure of aragonitic tissue disappears and is replaced by inorganic structural features.In order to understand the diagenetic replacement of biogenic aragonite to non-biogenic calcite, we subjected Arctica islandica mollusc shells to hydrothermal alteration experiments. Experimental conditions were between 100 and 175 • C, with the main focus on 100 and 175 • C, reaction durations between 1 and 84 days, and alteration fluids simulating meteoric and burial waters, respectively. Detailed microstructural and geochemical data were collected for samples altered at 100 • C (and at 0.1 MPa pressure) for 28 days and for samples altered at 175 • C (and at 0.9 MPa pressure) for 7 and 84 days. During hydrothermal alteration at 100 • C for 28 days most but not the entire biopolymer matrix was destroyed, while shell aragonite and its characteristic microstructure was largely preserved. In all experiments up to 174 • C, there are no signs of a replacement reaction of shell aragonite to calcite in X-ray diffraction bulk analysis. At 175 • C the replacement reaction started after a dormant time of 4 days, and the original shell microstructure was almost completely overprinted by the aragonite to calcite replacement reaction after 10 days. Newly formed calcite nucleated at locations which were in contact with the fluid, at the shell surface, in the open pore system, and along growth lines. In the experiments with fluids simulating meteoric water, calcite crystals reached sizes up to 200 µm, while in the experiments with Mg-containing fluids the calcite crystals reached sizes up to 1 mm after 7 days of alteration. Aragonite is metastable at all applied conditions. Only a small bulk thermodynamicPublished by Copernicus Publications on behalf of the European Geosciences Union. 1462 L. A. Casella et al.: Experimental diagenesis: insights into aragonite to calcite transformation driving force exists for the transition to calcite. We attribute the sluggish replacement reaction to the inhibition of calcite nucleation in the temperature window from ca. 50 to ca. 170 • C or, additionally, to the presence of magnesium. Correspondingly, in Mg 2+ -bearing solutions the newly formed calcite crystals are larger than in Mg 2+ -free solutions. Overall, the aragonite-calcite transition occurs via ...

show abstract

Section: Grain Size and Chemistry Of The Newly Formed Calcitementioning

confidence: 99%

Experimental diagenesis: insights into aragonite to calcite transformation of <i>Arctica islandica</i> shells by hydrothermal treatment

Casella¹,

Griesshaber²,

Yin³

et al. 2017

Biogeosciences

View full text Add to dashboard Cite

show abstract

“…Finally, long-term olivine dissolution rates can also be limited by the slow precipitation rates of secondary minerals, which could lead the fluid to approach equilibrium with the dissolving mineral (e.g. Zhu and Lu, 2009;Zhu et al, 2010;Saldi et al, 2012). This study was motivated in part to assess how these various processes might influence forsterite dissolution rates over time-scales larger than those typically considered in laboratory studies.…”

Section: Introductionmentioning

confidence: 99%

The efficient long-term inhibition of forsterite dissolution by common soil bacteria and fungi at Earth surface conditions

Oelkers

Benning

Lutz

et al. 2015

Geochimica et Cosmochimica Acta

Self Cite

View full text Add to dashboard Cite

“…However, a less attractive feature of magnesite formation is its notoriously slow reaction kinetics at ambient temperatures. In a recent paper, Saldi et al (2012) showed that the rate of magnesite formation at the expense of forsterite at temperatures between 100 and 200 °C is probably controlled by the slow rate of magnesite precipitation and not by forsterite dissolution, as is often assumed. In fact, magnesite precipitation is so slow that it would likely also control the rate of magnesite formation at the expense of serpentine.…”

Section: Serpentinite Carbonation At Linnajavrimentioning

confidence: 93%

Sculpting of Rocks by Reactive Fluids

Jamtveit¹,

Hammer²

2012

Geochem Persp

View full text Add to dashboard Cite

An experimental study of magnesite precipitation rates at neutral to alkaline conditions and 100–200°C as a function of pH, aqueous solution composition and chemical affinity

Cited by 116 publications

References 105 publications

Experimental diagenesis: insights into aragonite to calcite transformation of <i>Arctica islandica</i> shells by hydrothermal treatment

Experimental diagenesis: insights into aragonite to calcite transformation of <i>Arctica islandica</i> shells by hydrothermal treatment

The efficient long-term inhibition of forsterite dissolution by common soil bacteria and fungi at Earth surface conditions

Sculpting of Rocks by Reactive Fluids

Contact Info

Product

Resources

About

An experimental study of magnesite precipitation rates at neutral to alkaline conditions and 100–200°C as a function of pH, aqueous solution composition and chemical affinity

Cited by 116 publications

References 105 publications

Experimental diagenesis: insights into aragonite to calcite transformation of &lt;i&gt;Arctica islandica&lt;/i&gt; shells by hydrothermal treatment

Experimental diagenesis: insights into aragonite to calcite transformation of &lt;i&gt;Arctica islandica&lt;/i&gt; shells by hydrothermal treatment

The efficient long-term inhibition of forsterite dissolution by common soil bacteria and fungi at Earth surface conditions

Sculpting of Rocks by Reactive Fluids

Contact Info

Product

Resources

About

Experimental diagenesis: insights into aragonite to calcite transformation of <i>Arctica islandica</i> shells by hydrothermal treatment

Experimental diagenesis: insights into aragonite to calcite transformation of <i>Arctica islandica</i> shells by hydrothermal treatment