Chenmingite, FeCr2O4 in the CaFe2O4-type structure, a shock-induced, high-pressure mineral in the Tissint martian meteorite
| Autor: | John R. Beckett, Yang Liu, Eran Greenberg, Chi Ma, Oliver Tschauner, Vitali B. Prakapenka |
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| Rok vydání: | 2019 |
| Předmět: |
Ulvöspinel
Martian Materials science Mineral 010504 meteorology & atmospheric sciences Xieite engineering.material 010502 geochemistry & geophysics 01 natural sciences Crystallography Geophysics Meteorite Geochemistry and Petrology High pressure engineering Orthorhombic crystal system Chromite 0105 earth and related environmental sciences |
| Zdroj: | American Mineralogist. 104:1521-1525 |
| ISSN: | 1945-3027 0003-004X |
| DOI: | 10.2138/am-2019-6999 |
| Popis: | Chenmingite (FeCr2O4; IMA 2017-036) is a high-pressure mineral, occurring as micrometer- to submicrometer-sized lamellae within precursor chromite grains along with xieite and Fe,Cr-rich ulvöspinel next to shock-induced melt pockets, from the Tissint martian meteorite. The composition of type chenmingite by electron probe analysis shows an empirical formula of (Fe2+0.75Mg0.23Mn0.02) (Cr1.60Al0.29Fe3+0.06Fe2+0.04Ti0.02)Σ2.01O4. The general and end-member formulas are (Fe,Mg)(Cr,Al)2O4 and FeCr2O4. Synchrotron X-ray diffraction reveals that chenmingite has an orthorhombic Pnma CaFe2O4-type (CF) structure with unit-cell dimensions: a = 9.715(6) Å, b = 2.87(1) Å, c = 9.49(7) Å, V = 264.6(4) Å3, and Z = 4. Both chenmingite and xieite formed by solid-state transformation of precursor chromite under high pressure and high temperature during the Tissint impact event on Mars. The xieite regions are always in contact with melt pockets, whereas chenmingite lamellae only occur within chromite, a few micrometers away from the melt pockets. This arrangement suggests that chenmingite formed under similar pressures as xieite but at lower temperatures, in agreement with experimental studies. |
| Databáze: | OpenAIRE |
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