Prof. Denis Andrault [University Clermont Auvergne, France]

Title: Melting curve of deep mantle silicate phases and implications for cooling of the early Earth

Time: 9:30 - 11:00 AM, May 28, 2024 

Place: Conference room A417, HPSTAR (Beijing)   

Host: Dr. Yanhao Lin 

Abstract:

The high-pressure tools traditionally used to study the Earth's interior, namely the diamond anvil cell and the multi-anvil press, can be combined with in situ measurements to study the melting properties of the deep mantle. Several types of in situ probes are available, including synchrotron-based X-ray diffraction and imaging, and in house optical and electrical techniques. A major complication inherent to the study of geological materials is progressive melting when temperature is increased from solidus to liquidus. Therefore, beyond the basic determination of the solidus profile over a large range of mantle pressures, a main experimental challenge is the control of the rate of fusion. We will present some strategies developed in last years to determine melting curves as precisely as possible in the pressure range between 10 and 135 GPa.

The temperature gap between solidus and liquidus affects significantly the mechanism of gradual mantle solidification after the early episode of global magma ocean. Significant amounts of melt may have persisted much longer than was thought originally. We will develop a model for the gradual cooling of the deep mantle based on mantle dynamics, which explains well the composition of early lavas such as komatiites as well as more recent large igneous provinces. The solidification model also provides insights into the geodynamic transition between Archean and Proterozoic periods.

References cited: 

1     Pierru, R. et al. Deep mantle origin of large igneous provinces and komatiites. Sci. Adv. 8, eabo1036, (2022).[1]

2     Pierru, R. et al. Solidus melting of pyrolite and bridgmanite: Implication for the thermochemical state of the Earth’s interior. Earth Planet. Sci. Lett. 595, 117770, (2022).

3     Andrault, D. et al. Deep and persistent melt layer in the Archaean mantle. Nat. Geosci. 11, 139-143, (2018).