{"title":"Post-spinel transition of Fe2SiO4 ahrensite at high pressure and high temperature","authors":"Masaki Akaogi, Natsuki Miyazaki, Taisuke Tajima, Hiroshi Kojitani","doi":"10.1007/s00269-023-01247-4","DOIUrl":null,"url":null,"abstract":"<div><p>Phase relations for dissociation of spinel-structured Fe<sub>2</sub>SiO<sub>4</sub> ahrensite to FeO wüstite + SiO<sub>2</sub> stishovite have been determined up to 20 GPa and 1400 °C under the iron-wüstite buffer conditions by multianvil high-pressure and high-temperature experiments. The dissociation boundary determined is expressed by P (GPa) = 19.6 (± 1.0) – 3.0 (± 0.8) × 10<sup>−3</sup> T (°C). The boundary with the negative dP/dT slope is placed by ~ 1–4 GPa at lower pressure at 1000–1200 °C than the previously determined boundaries whose slopes ranged from strongly positive to weakly negative. Thermodynamic calculation based on available thermodynamic data of ahrensite, wüstite and stishovite has provided the dissociation boundary which is in good agreement within the errors with that experimentally determined in this study. By combining the post-spinel phase relations in Fe<sub>2</sub>SiO<sub>4</sub> determined in this study with available phase relations in the Fe<sub>2</sub>SiO<sub>4</sub>-Mg<sub>2</sub>SiO<sub>4</sub> system, it is suggested that natural Fe<sub>2</sub>SiO<sub>4</sub>-rich ahrensite crystals found in the shocked Umbarger L6 chondrite crystallized in shock-induced melt pockets of the FeO- and SiO<sub>2</sub>-rich composition at pressures below ~ 13–16 GPa and above ~ 9–12 GPa in the shock process.</p></div>","PeriodicalId":20132,"journal":{"name":"Physics and Chemistry of Minerals","volume":null,"pages":null},"PeriodicalIF":1.2000,"publicationDate":"2023-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Physics and Chemistry of Minerals","FirstCategoryId":"89","ListUrlMain":"https://link.springer.com/article/10.1007/s00269-023-01247-4","RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q4","JCRName":"MATERIALS SCIENCE, MULTIDISCIPLINARY","Score":null,"Total":0}
引用次数: 0
Abstract
Phase relations for dissociation of spinel-structured Fe2SiO4 ahrensite to FeO wüstite + SiO2 stishovite have been determined up to 20 GPa and 1400 °C under the iron-wüstite buffer conditions by multianvil high-pressure and high-temperature experiments. The dissociation boundary determined is expressed by P (GPa) = 19.6 (± 1.0) – 3.0 (± 0.8) × 10−3 T (°C). The boundary with the negative dP/dT slope is placed by ~ 1–4 GPa at lower pressure at 1000–1200 °C than the previously determined boundaries whose slopes ranged from strongly positive to weakly negative. Thermodynamic calculation based on available thermodynamic data of ahrensite, wüstite and stishovite has provided the dissociation boundary which is in good agreement within the errors with that experimentally determined in this study. By combining the post-spinel phase relations in Fe2SiO4 determined in this study with available phase relations in the Fe2SiO4-Mg2SiO4 system, it is suggested that natural Fe2SiO4-rich ahrensite crystals found in the shocked Umbarger L6 chondrite crystallized in shock-induced melt pockets of the FeO- and SiO2-rich composition at pressures below ~ 13–16 GPa and above ~ 9–12 GPa in the shock process.
期刊介绍:
Physics and Chemistry of Minerals is an international journal devoted to publishing articles and short communications of physical or chemical studies on minerals or solids related to minerals. The aim of the journal is to support competent interdisciplinary work in mineralogy and physics or chemistry. Particular emphasis is placed on applications of modern techniques or new theories and models to interpret atomic structures and physical or chemical properties of minerals. Some subjects of interest are:
-Relationships between atomic structure and crystalline state (structures of various states, crystal energies, crystal growth, thermodynamic studies, phase transformations, solid solution, exsolution phenomena, etc.)
-General solid state spectroscopy (ultraviolet, visible, infrared, Raman, ESCA, luminescence, X-ray, electron paramagnetic resonance, nuclear magnetic resonance, gamma ray resonance, etc.)
-Experimental and theoretical analysis of chemical bonding in minerals (application of crystal field, molecular orbital, band theories, etc.)
-Physical properties (magnetic, mechanical, electric, optical, thermodynamic, etc.)
-Relations between thermal expansion, compressibility, elastic constants, and fundamental properties of atomic structure, particularly as applied to geophysical problems
-Electron microscopy in support of physical and chemical studies
-Computational methods in the study of the structure and properties of minerals
-Mineral surfaces (experimental methods, structure and properties)