CaSiO3 polymorphs are abundant in only unique geological settings on the Earth’s surface and are the major Ca-bearing phases at deep mantle condition. An accurate and comprehensive study of their density and structural evolution with pressure and temperature is still lacking. Therefore, in this study we report the elastic behavior and structural evolution of wollastonite and CaSiO3-walstromite with pressure. Both minerals are characterized by first order phase transitions to denser structures. The deformations that lead to these transformations allow a volume increase ofthe bigger polyhedra, which might ease cation substitution in the structural sites of these phases. Furthermore, their geometrical features are clear analogies with those predicted and observed for tetrahedrally-structured ultra-high-pressure carbonates, which are unfortunately unquenchable. Indeed, wollastonite and CaSiO3-walstromite have a close resemblance to ultra-high-pressure chain-and ring-carbonates. This suggests a rich polymorphism also for tetrahedral carbonates, which might increase the compositional range of these phases, including continuous solid solutions involving cations with different size (Ca vs. Mg in particular) and important minor or trace elements incorporation.

Crystal structure evolution of CaSiO3 polymorphs at earth’s mantle pressures / S. Milani, D. Comboni, P. Lotti, P. Fumagalli, L. Ziberna, J. Maurice, M. Hanfland, M. Merlini. - In: MINERALS. - ISSN 2075-163X. - 11:6(2021 Jun 19), pp. 652.1-652.14. [10.3390/min11060652]

Crystal structure evolution of CaSiO3 polymorphs at earth’s mantle pressures

S. Milani
Primo
Conceptualization
;
P. Lotti;P. Fumagalli;J. Maurice;M. Merlini
Ultimo
Conceptualization
2021-06-19

Abstract

CaSiO3 polymorphs are abundant in only unique geological settings on the Earth’s surface and are the major Ca-bearing phases at deep mantle condition. An accurate and comprehensive study of their density and structural evolution with pressure and temperature is still lacking. Therefore, in this study we report the elastic behavior and structural evolution of wollastonite and CaSiO3-walstromite with pressure. Both minerals are characterized by first order phase transitions to denser structures. The deformations that lead to these transformations allow a volume increase ofthe bigger polyhedra, which might ease cation substitution in the structural sites of these phases. Furthermore, their geometrical features are clear analogies with those predicted and observed for tetrahedrally-structured ultra-high-pressure carbonates, which are unfortunately unquenchable. Indeed, wollastonite and CaSiO3-walstromite have a close resemblance to ultra-high-pressure chain-and ring-carbonates. This suggests a rich polymorphism also for tetrahedral carbonates, which might increase the compositional range of these phases, including continuous solid solutions involving cations with different size (Ca vs. Mg in particular) and important minor or trace elements incorporation.
Carbonates; CaSiO3; polymorphs; Crystal structure; Elastic properties; Mineral physics
Settore GEO/06 - Mineralogia
Settore GEO/07 - Petrologia e Petrografia
Settore GEO/09 - Georisorse Miner.Appl.Mineral.-Petrogr.per l'amb.e i Beni Cul
Dipartimenti di Eccellenza 2018-2022 - Dipartimento di SCIENZE DELLA TERRA "ARDITO DESIO"
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/2434/853420
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