Effect of cationic substitution on the pressure-induced phase transitions in calcium carbonate

Abstract

The high-pressure CaCO3 phase diagram has been the most extensively studied within the carbonates group. However, both the diverse mineralogy of carbonates and the abundance of solid solutions in natural samples require the investigation of multi-component systems at high pressures (P) and temperatures (T). Here we studied a member of the CaCO3-SrCO3 solid solution series, and revealed the effect of substituting Ca 2+ with Sr 2+ on the pressure-induced phase transitions in calcium carbonate. This is the peer-reviewed, final accepted version for American Mineralogist, published by the Mineralogical Society of America. The published version is subject to change. Cite as Authors (Year) Title. American Mineralogist, in press.

Structural, Physical, and Thermodynamic Properties of Aragonitic CaxSr1–xCO3 Solid Solutions

“…This is expected, as its structure is a derivative of the structure of calcite. Despite the high-pressure synthesis employed by Martirosyan et al, the smaller unit cell volume of the corresponding polymorph with an aragonite structure obtained here implies that calcitic Sr–Ca-solid solutions are not the high-pressure forms.…”

“…In comparison with our samples, which are isostructural to aragonite, the sample from Martirosyan et al 9 with Ca 0.82 Sr 0.18 CO 3 composition shows a significantly higher (≈7%) unit cell volume under ambient conditions. This is expected, as its structure is a derivative of the structure of calcite.…”

“…The error bars of the unit cell volume are smaller than the symbol size. The Ca 0.82 Sr 0.18 CO 3 samples synthesized in a multianvil press by Martirosyan et al 9 and by Saito et al 8 have a calcitic structure. As our data faithfully reproduce the undisputed thermodynamic properties of the end members, we conclude that our data are more reliable than the older values.…”

“…6 The present day Sr−Ca ratio is ≈0.1% in marine calcite and ≈1% in aragonite. 7 Recently, Saito et al 8 showed that Sr concentrations of x = 0.5 can be obtained by heating an amorphous precursor to 673 K. Martirosyan et al 9 investigated the highpressure behavior of a calcitic Ca−Sr solid solution with Ca 0.82 Sr 0.18 CO 3 composition and monoclinic P2 1 /c space group symmetry in a diamond anvil cell (DAC) up to 50 GPa by Raman spectroscopy. The sample had been synthesized in a multianvil press at 2 GPa and 1273 K. They inferred pressure-induced phase transitions between 0 and 7 GPa.…”

Effects of hydrostaticity and Mn-substitution on dolomite stability at high pressure

“…DOI: https://doi.org/10.2138/am-2022-8248. http://www.minsocam.org/ (Martirosyan et al, 2021;. The distorted structural environments provide a potential way to transport carbon into the deep mantle through a plethora of high-pressure polymorphisms of carbonate minerals due to diverse bonding patterns for carbon (Boulard et al, 2020;Lobanov and Goncharov, 2020).…”