Water-bearing, high-pressure Ca-silicates

Péter Németh, Kurt Leinenweber, Hiroaki Ohfuji, Thomas Groy, Kenneth J. Domanik, I. Kovács, Judit S. Kovács, Peter R. Buseck

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

Water-bearing minerals provide fundamental knowledge regarding the water budget of the mantle and are geophysically significant through their influence on the rheological and seismic properties of Earth's interior. Here we investigate the CaO–SiO2–H2O system at 17 GPa and 1773 K, corresponding to mantle transition-zone condition, report new high-pressure (HP) water-bearing Ca-silicates and reveal the structural complexity of these phases. We document the HP polymorph of hartrurite (Ca3SiO5), post-hartrurite, which is tetragonal with space group P4/ncc, a=6.820(5), c=10.243(8) Å, V=476.4(8) Å3, and Z=4, and is isostructural with Sr3SiO5. Post-hartrurite occurs in hydrous and anhydrous forms and coexists with larnite (Ca2SiO4), which we find also has a hydrous counterpart. Si is 4-coordinated in both post-hartrurite and larnite. In their hydrous forms, H substitutes for Si (4H for each Si; hydrogrossular substitution). Fourier transform infrared (FTIR) spectroscopy shows broad hydroxyl absorption bands at ∼3550 cm−1 and at 3500–3550 cm−1 for hydrous post-hartrurite and hydrous larnite, respectively. Hydrous post-hartrurite has a defect composition of Ca2.663Si0.826O5H1.370 (5.84 weight % H2O) according to electron-probe microanalysis (EPMA), and the Si deficiency relative to Ca is also observed in the single-crystal data. Hydrous larnite has average composition of Ca1.924Si0.851O4H0.748 (4.06 weight % H2O) according to EPMA, and it is in agreement with the Si occupancy obtained using X-ray data collected on a single crystal. Superlattice reflections occur in electron-diffraction patterns of the hydrous larnite and could indicate crystallographic ordering of the hydroxyl groups and their associated cation defects. Although textural and EPMA-based compositional evidence suggests that hydrous perovskite may occur in high-Ca-containing (or low silica-activity) systems, the FTIR measurement does not show a well-defined hydroxyl absorption band for this phase, implying the water content, at least in the quenched glass, is below the limit of detection (100–1000 ppm). We conclude that at high pressure, as at ambient pressure, some calcium silicates have a high affinity for H2O and high dehydration temperatures. The thermal stability of these hydrous phases suggests that they could exist along a typical mantle geotherm and thus they might be relevant for understanding the mineralogy and water content of Earth's mantle.

Original languageEnglish
Pages (from-to)148-155
Number of pages8
JournalEarth and Planetary Science Letters
Volume469
DOIs
Publication statusPublished - Jul 1 2017

Fingerprint

Bearings (structural)
Silicates
silicates
Earth mantle
Electron probe microanalysis
electron probes
silicate
microanalysis
electron probe analysis
Hydroxyl Radical
mantle
Water
Water content
water
moisture content
defect
Absorption spectra
Earth (planet)
water content
Single crystals

Keywords

  • hydrous Ca-perovskite
  • new high-pressure phases
  • OH group ordering and superlattice reflections
  • post-hartrurite
  • water budget of the mantle
  • water-bearing Ca-silicates

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science

Cite this

Németh, P., Leinenweber, K., Ohfuji, H., Groy, T., Domanik, K. J., Kovács, I., ... Buseck, P. R. (2017). Water-bearing, high-pressure Ca-silicates. Earth and Planetary Science Letters, 469, 148-155. https://doi.org/10.1016/j.epsl.2017.04.011

Water-bearing, high-pressure Ca-silicates. / Németh, Péter; Leinenweber, Kurt; Ohfuji, Hiroaki; Groy, Thomas; Domanik, Kenneth J.; Kovács, I.; Kovács, Judit S.; Buseck, Peter R.

In: Earth and Planetary Science Letters, Vol. 469, 01.07.2017, p. 148-155.

Research output: Contribution to journalArticle

Németh, P, Leinenweber, K, Ohfuji, H, Groy, T, Domanik, KJ, Kovács, I, Kovács, JS & Buseck, PR 2017, 'Water-bearing, high-pressure Ca-silicates', Earth and Planetary Science Letters, vol. 469, pp. 148-155. https://doi.org/10.1016/j.epsl.2017.04.011
Németh P, Leinenweber K, Ohfuji H, Groy T, Domanik KJ, Kovács I et al. Water-bearing, high-pressure Ca-silicates. Earth and Planetary Science Letters. 2017 Jul 1;469:148-155. https://doi.org/10.1016/j.epsl.2017.04.011
Németh, Péter ; Leinenweber, Kurt ; Ohfuji, Hiroaki ; Groy, Thomas ; Domanik, Kenneth J. ; Kovács, I. ; Kovács, Judit S. ; Buseck, Peter R. / Water-bearing, high-pressure Ca-silicates. In: Earth and Planetary Science Letters. 2017 ; Vol. 469. pp. 148-155.
@article{2d6ec81369b14ff8bb4b96d0702686d5,
title = "Water-bearing, high-pressure Ca-silicates",
abstract = "Water-bearing minerals provide fundamental knowledge regarding the water budget of the mantle and are geophysically significant through their influence on the rheological and seismic properties of Earth's interior. Here we investigate the CaO–SiO2–H2O system at 17 GPa and 1773 K, corresponding to mantle transition-zone condition, report new high-pressure (HP) water-bearing Ca-silicates and reveal the structural complexity of these phases. We document the HP polymorph of hartrurite (Ca3SiO5), post-hartrurite, which is tetragonal with space group P4/ncc, a=6.820(5), c=10.243(8) {\AA}, V=476.4(8) {\AA}3, and Z=4, and is isostructural with Sr3SiO5. Post-hartrurite occurs in hydrous and anhydrous forms and coexists with larnite (Ca2SiO4), which we find also has a hydrous counterpart. Si is 4-coordinated in both post-hartrurite and larnite. In their hydrous forms, H substitutes for Si (4H for each Si; hydrogrossular substitution). Fourier transform infrared (FTIR) spectroscopy shows broad hydroxyl absorption bands at ∼3550 cm−1 and at 3500–3550 cm−1 for hydrous post-hartrurite and hydrous larnite, respectively. Hydrous post-hartrurite has a defect composition of Ca2.663Si0.826O5H1.370 (5.84 weight {\%} H2O) according to electron-probe microanalysis (EPMA), and the Si deficiency relative to Ca is also observed in the single-crystal data. Hydrous larnite has average composition of Ca1.924Si0.851O4H0.748 (4.06 weight {\%} H2O) according to EPMA, and it is in agreement with the Si occupancy obtained using X-ray data collected on a single crystal. Superlattice reflections occur in electron-diffraction patterns of the hydrous larnite and could indicate crystallographic ordering of the hydroxyl groups and their associated cation defects. Although textural and EPMA-based compositional evidence suggests that hydrous perovskite may occur in high-Ca-containing (or low silica-activity) systems, the FTIR measurement does not show a well-defined hydroxyl absorption band for this phase, implying the water content, at least in the quenched glass, is below the limit of detection (100–1000 ppm). We conclude that at high pressure, as at ambient pressure, some calcium silicates have a high affinity for H2O and high dehydration temperatures. The thermal stability of these hydrous phases suggests that they could exist along a typical mantle geotherm and thus they might be relevant for understanding the mineralogy and water content of Earth's mantle.",
keywords = "hydrous Ca-perovskite, new high-pressure phases, OH group ordering and superlattice reflections, post-hartrurite, water budget of the mantle, water-bearing Ca-silicates",
author = "P{\'e}ter N{\'e}meth and Kurt Leinenweber and Hiroaki Ohfuji and Thomas Groy and Domanik, {Kenneth J.} and I. Kov{\'a}cs and Kov{\'a}cs, {Judit S.} and Buseck, {Peter R.}",
year = "2017",
month = "7",
day = "1",
doi = "10.1016/j.epsl.2017.04.011",
language = "English",
volume = "469",
pages = "148--155",
journal = "Earth and Planetary Sciences Letters",
issn = "0012-821X",
publisher = "Elsevier",

}

TY - JOUR

T1 - Water-bearing, high-pressure Ca-silicates

AU - Németh, Péter

AU - Leinenweber, Kurt

AU - Ohfuji, Hiroaki

AU - Groy, Thomas

AU - Domanik, Kenneth J.

AU - Kovács, I.

AU - Kovács, Judit S.

AU - Buseck, Peter R.

PY - 2017/7/1

Y1 - 2017/7/1

N2 - Water-bearing minerals provide fundamental knowledge regarding the water budget of the mantle and are geophysically significant through their influence on the rheological and seismic properties of Earth's interior. Here we investigate the CaO–SiO2–H2O system at 17 GPa and 1773 K, corresponding to mantle transition-zone condition, report new high-pressure (HP) water-bearing Ca-silicates and reveal the structural complexity of these phases. We document the HP polymorph of hartrurite (Ca3SiO5), post-hartrurite, which is tetragonal with space group P4/ncc, a=6.820(5), c=10.243(8) Å, V=476.4(8) Å3, and Z=4, and is isostructural with Sr3SiO5. Post-hartrurite occurs in hydrous and anhydrous forms and coexists with larnite (Ca2SiO4), which we find also has a hydrous counterpart. Si is 4-coordinated in both post-hartrurite and larnite. In their hydrous forms, H substitutes for Si (4H for each Si; hydrogrossular substitution). Fourier transform infrared (FTIR) spectroscopy shows broad hydroxyl absorption bands at ∼3550 cm−1 and at 3500–3550 cm−1 for hydrous post-hartrurite and hydrous larnite, respectively. Hydrous post-hartrurite has a defect composition of Ca2.663Si0.826O5H1.370 (5.84 weight % H2O) according to electron-probe microanalysis (EPMA), and the Si deficiency relative to Ca is also observed in the single-crystal data. Hydrous larnite has average composition of Ca1.924Si0.851O4H0.748 (4.06 weight % H2O) according to EPMA, and it is in agreement with the Si occupancy obtained using X-ray data collected on a single crystal. Superlattice reflections occur in electron-diffraction patterns of the hydrous larnite and could indicate crystallographic ordering of the hydroxyl groups and their associated cation defects. Although textural and EPMA-based compositional evidence suggests that hydrous perovskite may occur in high-Ca-containing (or low silica-activity) systems, the FTIR measurement does not show a well-defined hydroxyl absorption band for this phase, implying the water content, at least in the quenched glass, is below the limit of detection (100–1000 ppm). We conclude that at high pressure, as at ambient pressure, some calcium silicates have a high affinity for H2O and high dehydration temperatures. The thermal stability of these hydrous phases suggests that they could exist along a typical mantle geotherm and thus they might be relevant for understanding the mineralogy and water content of Earth's mantle.

AB - Water-bearing minerals provide fundamental knowledge regarding the water budget of the mantle and are geophysically significant through their influence on the rheological and seismic properties of Earth's interior. Here we investigate the CaO–SiO2–H2O system at 17 GPa and 1773 K, corresponding to mantle transition-zone condition, report new high-pressure (HP) water-bearing Ca-silicates and reveal the structural complexity of these phases. We document the HP polymorph of hartrurite (Ca3SiO5), post-hartrurite, which is tetragonal with space group P4/ncc, a=6.820(5), c=10.243(8) Å, V=476.4(8) Å3, and Z=4, and is isostructural with Sr3SiO5. Post-hartrurite occurs in hydrous and anhydrous forms and coexists with larnite (Ca2SiO4), which we find also has a hydrous counterpart. Si is 4-coordinated in both post-hartrurite and larnite. In their hydrous forms, H substitutes for Si (4H for each Si; hydrogrossular substitution). Fourier transform infrared (FTIR) spectroscopy shows broad hydroxyl absorption bands at ∼3550 cm−1 and at 3500–3550 cm−1 for hydrous post-hartrurite and hydrous larnite, respectively. Hydrous post-hartrurite has a defect composition of Ca2.663Si0.826O5H1.370 (5.84 weight % H2O) according to electron-probe microanalysis (EPMA), and the Si deficiency relative to Ca is also observed in the single-crystal data. Hydrous larnite has average composition of Ca1.924Si0.851O4H0.748 (4.06 weight % H2O) according to EPMA, and it is in agreement with the Si occupancy obtained using X-ray data collected on a single crystal. Superlattice reflections occur in electron-diffraction patterns of the hydrous larnite and could indicate crystallographic ordering of the hydroxyl groups and their associated cation defects. Although textural and EPMA-based compositional evidence suggests that hydrous perovskite may occur in high-Ca-containing (or low silica-activity) systems, the FTIR measurement does not show a well-defined hydroxyl absorption band for this phase, implying the water content, at least in the quenched glass, is below the limit of detection (100–1000 ppm). We conclude that at high pressure, as at ambient pressure, some calcium silicates have a high affinity for H2O and high dehydration temperatures. The thermal stability of these hydrous phases suggests that they could exist along a typical mantle geotherm and thus they might be relevant for understanding the mineralogy and water content of Earth's mantle.

KW - hydrous Ca-perovskite

KW - new high-pressure phases

KW - OH group ordering and superlattice reflections

KW - post-hartrurite

KW - water budget of the mantle

KW - water-bearing Ca-silicates

UR - http://www.scopus.com/inward/record.url?scp=85019004690&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85019004690&partnerID=8YFLogxK

U2 - 10.1016/j.epsl.2017.04.011

DO - 10.1016/j.epsl.2017.04.011

M3 - Article

VL - 469

SP - 148

EP - 155

JO - Earth and Planetary Sciences Letters

JF - Earth and Planetary Sciences Letters

SN - 0012-821X

ER -