In Situ High-Temperature and High-Pressure Spectroscopic Study of the Thermal and Pressure Behavior of Hydrous Fe-Rich Ringwoodite

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In situ high-temperature Raman spectroscopy (up to 550 °C) and infrared spectroscopy (up to 700 °C) were employed to analyze hydrous Fe-rich ringwoodite (Fo76 composition containing 0.69 wt% H2O). The results demonstrate that the hydrous Fe-rich ringwoodite sample undergoes irreversible structural transformation above 300 °C at ambient pressure, converting to an amorphous phase. This indicates a lower thermal stability threshold compared to Fe-bearing ringwoodite (Fo90) with equivalent water content. Notably, identical infrared spectral evolution patterns were observed during heating (25–500 °C) for the studied Fo76 sample and previously reported Fo82/Fo90 specimens, suggesting minimal influence of iron content variation on hydroxyl group behavior. The material derived from Fe-rich ringwoodite through structural transformation at ~350 °C retains the capacity to preserve water within a defined temperature window (400–550 °C). In situ high-pressure Raman spectroscopy experiments conducted up to 20 GPa detected no notable structural modifications, suggesting that hydrous Fe-rich ringwoodite, hydrous Fe-bearing ringwoodite, and hydrous Mg-endmember ringwoodite exhibit comparable structural stability within this pressure range.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.