| Autor: |
Saha, Pinku, Murakami, Motohiko, McCammon, Catherine, Liebske, Christian, Krymarys, Ewa |
| Předmět: |
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| Zdroj: |
Geophysical Research Letters; 7/28/2023, Vol. 50 Issue 14, p1-10, 10p |
| Abstrakt: |
We have carried out in situ high‐pressure acoustic velocity measurements of (Fe2+, Al)‐bearing MgSiO3 glass up to pressures of 155 GPa, which confirmed a distinct pressure‐induced trend change in the transverse acoustic velocity (VS) profile around 98 GPa, likely caused by the Si‐O coordination number (CN) change from 6 to 6+. Although it has been reported that the substitution of Fe2+ in MgSiO3 glass induces almost linear velocity reduction up to ∼160 GPa, we revealed that the VS profile of (Fe2+, Al)‐bearing MgSiO3 becomes anomalously steeper above ∼100 GPa and eventually came to be equivalent to MgSiO3 glass above ∼125 GPa. This implies the incorporation of Al into Fe‐bearing MgSiO3 glass significantly facilitates making it far elastically stiffer and thus the densification under pressures well within the Earth's lower mantle. Our results indicate the possible presence of stiff and highly dense silicate melts in deep MOs in the rocky terrestrial planets. Plain Language Summary: Since the terrestrial planets are thought to have gone through multiple episodes of magma ocean (MO) in their formation processes, clarifying the structure and physical properties of silicate melts under relevant deep MO conditions is crucial to understanding the internal structure and evolution of the terrestrial planets. Our in situ high‐pressure acoustic velocity measurements of (Fe2+, Al)‐bearing MgSiO3 glass, used as a structural analog of silicate melts, shows both Al and Fe2+ are very effective to reduce the pressure corresponding to the Si‐O CN change from 6 to 6+. In addition, a few percentages of Al incorporation could make the Fe‐bearing MgSiO3 glass significantly far elastically stiff and thus dense with 6+ CN in Si‐O in the deep terrestrial interiors. The presence of stiff and highly dense silicate melts in deep MOs in the terrestrial planets would offer essential insights into the MO convection, gravitational stability of silicate melts in the course of MO crystallization, and the mantle stratification of the terrestrial planets. Key Points: We have carried out acoustic wave velocity measurements of (Fe2+, Al)‐bearing MgSiO3 glass up to 155 GPaVS profile displays a change at 98 GPa induced by the Si‐O coordination number change from 6 to 6+ followed by anomalously steeper trendResults indicate the possible presence of highly dense Al, Fe2+‐bearing Si‐rich melts in the deep terrestrial magma oceans [ABSTRACT FROM AUTHOR] |
| Databáze: |
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