High-Pressure and High-Temperature Phase Transitions in Fe<sub>2</sub>TiO<sub>4</sub> and Mg<sub>2</sub>TiO<sub>4</sub> with Implications for Titanomagnetite Inclusions in Superdeep Diamonds
Phase transitions of Mg<sub>2</sub>TiO<sub>4</sub> and Fe<sub>2</sub>TiO<sub>4</sub> were examined up to 28 GPa and 1600 °C using a multianvil apparatus. The quenched samples were examined by powder X-ray diffraction. With increasing pressure...
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MDPI AG
2019-10-01
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| Series: | Minerals |
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| Online Access: | https://www.mdpi.com/2075-163X/9/10/614 |
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| author | Masaki Akaogi Taisuke Tajima Masaki Okano Hiroshi Kojitani |
| author_facet | Masaki Akaogi Taisuke Tajima Masaki Okano Hiroshi Kojitani |
| author_sort | Masaki Akaogi |
| collection | DOAJ |
| description | Phase transitions of Mg<sub>2</sub>TiO<sub>4</sub> and Fe<sub>2</sub>TiO<sub>4</sub> were examined up to 28 GPa and 1600 °C using a multianvil apparatus. The quenched samples were examined by powder X-ray diffraction. With increasing pressure at high temperature, spinel-type Mg<sub>2</sub>TiO<sub>4</sub> decomposes into MgO and ilmenite-type MgTiO<sub>3</sub> which further transforms to perovskite-type MgTiO<sub>3</sub>. At ~21 GPa, the assemblage of MgTiO<sub>3</sub> perovskite + MgO changes to 2MgO + TiO<sub>2</sub> with baddeleyite (or orthorhombic I)-type structure. Fe<sub>2</sub>TiO<sub>4</sub> undergoes transitions similar to Mg<sub>2</sub>TiO<sub>4</sub> with pressure: spinel-type Fe<sub>2</sub>TiO<sub>4</sub> dissociates into FeO and ilmenite-type FeTiO<sub>3</sub> which transforms to perovskite-type FeTiO<sub>3</sub>. Both of MgTiO<sub>3</sub> and FeTiO<sub>3</sub> perovskites change to LiNbO<sub>3</sub>-type phases on release of pressure. In Fe<sub>2</sub>TiO<sub>4</sub>, however, perovskite-type FeTiO<sub>3</sub> and FeO combine into calcium titanate-type Fe<sub>2</sub>TiO<sub>4</sub> at ~15 GPa. The formation of calcium titanate-type Fe<sub>2</sub>TiO<sub>4</sub> at high pressure may be explained by effects of crystal field stabilization and high spin−low spin transition in Fe<sup>2+</sup> in the octahedral sites of calcium titanate-type Fe<sub>2</sub>TiO<sub>4</sub>. It is inferred from the determined phase relations that some of Fe<sub>2</sub>TiO<sub>4</sub>-rich titanomagnetite inclusions in diamonds recently found in São Luiz, Juina, Brazil, may be originally calcium titanate-type Fe<sub>2</sub>TiO<sub>4</sub> at pressure above ~15 GPa in the transition zone or lower mantle and transformed to spinel-type in the upper mantle conditions. |
| first_indexed | 2024-04-13T15:09:51Z |
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| last_indexed | 2024-04-13T15:09:51Z |
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| spelling | doaj.art-4926230007de40ccaf7103e257aeb24d2022-12-22T02:42:02ZengMDPI AGMinerals2075-163X2019-10-0191061410.3390/min9100614min9100614High-Pressure and High-Temperature Phase Transitions in Fe<sub>2</sub>TiO<sub>4</sub> and Mg<sub>2</sub>TiO<sub>4</sub> with Implications for Titanomagnetite Inclusions in Superdeep DiamondsMasaki Akaogi0Taisuke Tajima1Masaki Okano2Hiroshi Kojitani3Department of Chemistry, Gakushuin University, Mejiro, Toshima-ku, Tokyo 171-8588, JapanDepartment of Chemistry, Gakushuin University, Mejiro, Toshima-ku, Tokyo 171-8588, JapanDepartment of Chemistry, Gakushuin University, Mejiro, Toshima-ku, Tokyo 171-8588, JapanDepartment of Chemistry, Gakushuin University, Mejiro, Toshima-ku, Tokyo 171-8588, JapanPhase transitions of Mg<sub>2</sub>TiO<sub>4</sub> and Fe<sub>2</sub>TiO<sub>4</sub> were examined up to 28 GPa and 1600 °C using a multianvil apparatus. The quenched samples were examined by powder X-ray diffraction. With increasing pressure at high temperature, spinel-type Mg<sub>2</sub>TiO<sub>4</sub> decomposes into MgO and ilmenite-type MgTiO<sub>3</sub> which further transforms to perovskite-type MgTiO<sub>3</sub>. At ~21 GPa, the assemblage of MgTiO<sub>3</sub> perovskite + MgO changes to 2MgO + TiO<sub>2</sub> with baddeleyite (or orthorhombic I)-type structure. Fe<sub>2</sub>TiO<sub>4</sub> undergoes transitions similar to Mg<sub>2</sub>TiO<sub>4</sub> with pressure: spinel-type Fe<sub>2</sub>TiO<sub>4</sub> dissociates into FeO and ilmenite-type FeTiO<sub>3</sub> which transforms to perovskite-type FeTiO<sub>3</sub>. Both of MgTiO<sub>3</sub> and FeTiO<sub>3</sub> perovskites change to LiNbO<sub>3</sub>-type phases on release of pressure. In Fe<sub>2</sub>TiO<sub>4</sub>, however, perovskite-type FeTiO<sub>3</sub> and FeO combine into calcium titanate-type Fe<sub>2</sub>TiO<sub>4</sub> at ~15 GPa. The formation of calcium titanate-type Fe<sub>2</sub>TiO<sub>4</sub> at high pressure may be explained by effects of crystal field stabilization and high spin−low spin transition in Fe<sup>2+</sup> in the octahedral sites of calcium titanate-type Fe<sub>2</sub>TiO<sub>4</sub>. It is inferred from the determined phase relations that some of Fe<sub>2</sub>TiO<sub>4</sub>-rich titanomagnetite inclusions in diamonds recently found in São Luiz, Juina, Brazil, may be originally calcium titanate-type Fe<sub>2</sub>TiO<sub>4</sub> at pressure above ~15 GPa in the transition zone or lower mantle and transformed to spinel-type in the upper mantle conditions.https://www.mdpi.com/2075-163X/9/10/614phase transitionhigh pressuremg<sub>2</sub>tio<sub>4</sub>fe<sub>2</sub>tio<sub>4</sub>spinelilmeniteperovskitelithium niobatecalcium titanatediamond inclusion |
| spellingShingle | Masaki Akaogi Taisuke Tajima Masaki Okano Hiroshi Kojitani High-Pressure and High-Temperature Phase Transitions in Fe<sub>2</sub>TiO<sub>4</sub> and Mg<sub>2</sub>TiO<sub>4</sub> with Implications for Titanomagnetite Inclusions in Superdeep Diamonds Minerals phase transition high pressure mg<sub>2</sub>tio<sub>4</sub> fe<sub>2</sub>tio<sub>4</sub> spinel ilmenite perovskite lithium niobate calcium titanate diamond inclusion |
| title | High-Pressure and High-Temperature Phase Transitions in Fe<sub>2</sub>TiO<sub>4</sub> and Mg<sub>2</sub>TiO<sub>4</sub> with Implications for Titanomagnetite Inclusions in Superdeep Diamonds |
| title_full | High-Pressure and High-Temperature Phase Transitions in Fe<sub>2</sub>TiO<sub>4</sub> and Mg<sub>2</sub>TiO<sub>4</sub> with Implications for Titanomagnetite Inclusions in Superdeep Diamonds |
| title_fullStr | High-Pressure and High-Temperature Phase Transitions in Fe<sub>2</sub>TiO<sub>4</sub> and Mg<sub>2</sub>TiO<sub>4</sub> with Implications for Titanomagnetite Inclusions in Superdeep Diamonds |
| title_full_unstemmed | High-Pressure and High-Temperature Phase Transitions in Fe<sub>2</sub>TiO<sub>4</sub> and Mg<sub>2</sub>TiO<sub>4</sub> with Implications for Titanomagnetite Inclusions in Superdeep Diamonds |
| title_short | High-Pressure and High-Temperature Phase Transitions in Fe<sub>2</sub>TiO<sub>4</sub> and Mg<sub>2</sub>TiO<sub>4</sub> with Implications for Titanomagnetite Inclusions in Superdeep Diamonds |
| title_sort | high pressure and high temperature phase transitions in fe sub 2 sub tio sub 4 sub and mg sub 2 sub tio sub 4 sub with implications for titanomagnetite inclusions in superdeep diamonds |
| topic | phase transition high pressure mg<sub>2</sub>tio<sub>4</sub> fe<sub>2</sub>tio<sub>4</sub> spinel ilmenite perovskite lithium niobate calcium titanate diamond inclusion |
| url | https://www.mdpi.com/2075-163X/9/10/614 |
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