High temperature stability of maghemite in partially oxidized basalt lava |
| |
Authors: | Örn Helgason Haraldur P Gunnlaugsson Siguröur Steinthorsson Steen Mørup |
| |
Institution: | (1) Science Institute, University of Iceland, Dunhagi 3, 1S-107 Reykjavík, Iceland;(2) Laboratory of Applied Physics, Technical University of Denmark, DK-2800 Lyngby, Denmark |
| |
Abstract: | Mössbauer spectroscopy of basalt lava samples, exhibiting reversible thermal magnetization (JS-T) curves with Curie temperatures of about 580°C, has revealed considerable amounts of maghemite (γ-Fe2O3) in many samples. In view of the expected instability, of maghemite at temperatures above 350°C, this reversibility is rather surprising. Here we report Mössbauer studies on heated lava samples, showing high content of maghemite. The samples were kept at 600°C in oxidizing, reducing, and inactive atmospheres, respectively, for different lengths of time, and then analyzed with Mössbauer spectroscopy at room temperature. The Mössbauer spectra showed that maghemite is stable in the oxidizing atmosphere for at least several hours. In the inactive atmosphere a considerable amount of maghemite still exists after two hours heating. In the reducing atmosphere maghemite had transformed to magnetite after only 30 minutes. |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|