Structural Stability of Natural Magnesiochromite at High-Temperature-Pressure Conditions
Shuyu Jin , Xiang Wu , Yungui Liu , Yanfei Zhang , Chao Wang
Journal of Earth Science ›› 2024, Vol. 35 ›› Issue (4) : 1196 -1203.
Structural Stability of Natural Magnesiochromite at High-Temperature-Pressure Conditions
The podiform chromitites in the Luobusha ophiolite have been thought to experience a very deep formation, but the maximum depth is still an open issue. Here, we have investigated the structural stability of natural magnesiochromite using the synchrotron-based powder X-ray diffraction and diamond anvil cells up to 48.6 GPa and 2 450 K. The results have shown that spinel-type magnesiochromite first decomposes into corundum-type ‘Cr2O3’ + B1-type ‘MgO’ at 11–14 GPa and 1 250–1 450 K, then modified ludwigite (mLd)-type ‘Mg2Cr2O5’ + corundum-type ‘Cr2O3’ at 14.3–20.5 GPa and 1 300–2 000 K, and finally CaTi2O4-type phase at 24.5 GPa. During the quenching procession from high-temperature-pressure conditions, the mLd-type phase appeared again and was kept at ambient conditions. We also obtained the isothermal equation states of spinel-type and CaTi2O4-type phases, revealing the composition effect on their elasticities. Based on the updated results, we propose chromitites could not experience pressure exceeding ∼14.3 GPa (approximate maximum depth ∼400 km) in the subduction-recycling genesis model.
chromite / high-temperature and high-pressure / phase transitions / equation of state / chromitites genesis
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China University of Geosciences (Wuhan) and Springer-Verlag GmbH Germany, Part of Springer Nature
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