Abstract
High-pressure Raman and infrared spectra of a natural sample of prehnite, with a chemical composition of Ca2(Al0.74,Fe0.26)2Si3O10(OH)2, are presented. Analyses of the spectra indicate that prehnite undergoes a reversible structural change between 6 and 8 GPa that is most likely associated with a subtle alteration in the orientation and/or deformation of the polyhedra comprising the framework of the structure. At pressures in excess of ~11 GPa, the high-pressure spectra indicate that prehnite undergoes a reversible phase transition involving the collapse of the framework structure.
Highlights
Prehnite is a hydrous calcium aluminosilicate mineral and a member of the prehnite-pumpellyite metamorphic facies, and is commonly associated with oceanic plate subduction zones, where hydrogen incorporation into mineral structures occurs [1]
Prehnite and its associated minerals provide valuable information pertaining to important geological processes, such as rock formation and water transportation, and for this reason, the evaluation of their physical and structural properties as a function of pressure and temperature is of importance
When viewed along the [010] direction, the prehnite framework appears to consist of layers of octahedra, connected by three layers of tetrahedra (Figure 1)
Summary
Prehnite is a hydrous calcium aluminosilicate mineral and a member of the prehnite-pumpellyite metamorphic facies, and is commonly associated with oceanic plate subduction zones, where hydrogen incorporation into mineral structures occurs [1]. When viewed along the [010] direction, the prehnite framework appears to consist of layers of octahedra, connected by three layers of tetrahedra (Figure 1). These (Si,Al)O4 tetrahedra form a corkscrew arrangement that extends parallel to [010]. If the structure is described in orthorhombic space group Pncm, the average structure that is obtained is disordered, and the central atoms of the tetrahedra comprising the intermediate layer must be modelled as Si and Al in a 1:1 ratio (Figure 1). The apices of the octahedra are protonated, leading to possible hydrogen bonding between octahedral units that lie adjacent to each other in the [010] direction, as shown in Figure 1 where the bifurcated environment of the H and its nearest oxygen atoms is indicated by dashed lines. The anionic charge on the framework is compensated for by Ca2+ ions, located within the channels of the framework that run parallel to [010]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
