Structural Behavior of Natural Silicate–Carbonate Spurrite Mineral, Ca₅(SiO₄)₂(CO₃), under High-Pressure, High-Temperature Conditions

Abstract

We report on high-pressure and high-temperature angle-dispersive synchrotron X-ray diffraction and high-pressure Raman data up to 27 GPa and 700 K for natural silicate carbonate Ca(SiO)(CO) spurrite mineral. No phase transition was found in the studied P-T range. The room-temperature bulk modulus of spurrite using Ne as the pressure-transmitting medium is B = 77(1) GPa with a first-pressure derivative of B' = 5.9(2). The structure compression is highly anisotropic, the b axis being approximately 30% more compressible than the a and c axes. The volumetric thermal expansivity value around 8 GPa was estimated to be 4.1(3) × 10 K. A comparison with intimately related minerals CaCO calcite and aragonite and β-CaSiO larnite shows that, as the composition and structural features of spurrite suggest, its compressibility and thermal expansivity lie between those of the silicate and carbonate end members. The crystal chemistry and thermodynamic properties of spurrite are discussed.

Post-tilleyite, a dense calcium silicate-carbonate phase

“…5 of SI). The thermal expansivity of tilleyite lies between those of CaCO 3 aragonite (6.53·10 −5 K −1 ) and CaCO 3 calcite (2.01·10 −5 K −1 ) 37 , and it is only slightly smaller than those of calcium silicate β-Ca 2 SiO 4 larnite (4.24(4)·10 −5 K −1 ) 38 at room pressure and Ca 5 (SiO 4 ) 2 (CO 3 ) spurrite at ∼8 GPa (4.1(3)·10 −5 K −1 ) 18 . CaSiO 3 wollastonite, another end-member calcium silicate, exhibits a smaller thermal expansion (5.7–7·10 −6 K −1 ) 39 .…”

“…Due to the fact that the pressure is not constant during heating, we used a perturbational method to estimate the thermal expansivity at low pressures, as described in ref. 18 . This approximation has been successfully used to calculate the thermal expansivity under compression in other compounds 35,36 .…”

“…In this regard, it is important to attain an accurate description of the crystal structures and physical properties of these materials at high pressures and temperatures. The compressibility and phase stability of spurrite up to 27 GPa and 700 K have been recently reported 18 . No phase transformation was found, which suggests that the presence of carbonate [CO 3 ] units gives stability to the tetrahedral [SiO 4 ] orthosilicate group, holding up the formation of phases based on octahedral [SiO 6 ] units.…”

Oxidation of High Yield Strength Metals Tungsten and Rhenium in High-Pressure High-Temperature Experiments of Carbon Dioxide and Carbonates

“…High-pressure high-temperature X-ray diffraction (XRD) measurements were performed using symmetric and Boehler-Almax diamond-anvil cells (DACs). The chemical interaction between tungsten and carbonates was observed while laser-heating natural silicate-carbonate samples [6,22,23]. Natural tilleyite mineral (specimen YPM MIN 041104, Yale Peabody Museum) from the Crestmore quarry was analyzed by energy-dispersive X-ray spectroscopy, and only traces (<1 wt%) of Al and K were found apart the Ca, Si, C and O atoms present in the ideal Ca 5 (Si 2 O 7 )(CO 3 ) 2 formulae.…”

Crystal Structure of BaCa(CO3)2 Alstonite Carbonate and Its Phase Stability upon Compression

“…Thus, whereas CaM(CO 3 ) 2 (M = Mg, Mn, Zn, Fe) present Ca-centered octahedra, − the different Ca–Mg stoichiometry of huntite CaMg 3 (CO 3 ) 4 entails the formation of Ca-centered trigonal prisms . In calcium carbonates that include Na + , K + , Sr 2+ , Ba 2+ cations, Ca coordination varies from 6 to 9 depending on the structure or even within the same structure. − Naturally occurring calcium silicate-carbonates, for instance, present a large variety of Ca atom environments, ranging from 6-fold to 9-fold coordination. , Note that the different classes of irregular cation-centered oxygen polyhedra exhibit a wide range of volumes and bulk moduli, which suggests that other divalent cation species could be accommodated in these sites. Therefore, the study of the atomic arrangements in different Ca carbonate systems and their behavior at high pressures could provide insight into the nature of the Ca–(CO 3 ) interactions and potential chemical substitution at inner earth conditions.…”