[S-IT16] Deep Earth Sciences

[SIT16-P15] Determination of the liquidus temperature of the pyrolitic lower mantle

*Shuhei Mita¹, Yoshiyuki Okuda¹, Kei Hirose¹ (1.The University of Tokyo)

Keywords:high pressure, diamond-anvil cell, melting, magma ocean, pyrolite

The liquidus temperature of the mantle is of great importance to understand the solidification of a magma ocean (MO). In addition, core-forming metals may have reached chemical equilibrium with silicate at the base of the MO where temperature should be on the silicate liquidus. Determination of the liquidus temperatures of multi-component mantle materials in a diamond-anvil cell (DAC) has been challenging because of a relatively large temperature gradient in a laser-heated sample; as long as the temperature at the outer portion of the laser-heated sample is below the liquidus, the chemical composition of a melt pool formed at the hottest part is not of a fully molten starting material and therefore the liquidus temperature is not obtained. Indeed, the liquidus temperatures of mantle materials have been examined by a couple of previous studies but their results are inconsistent with each other (Fiquet et al., 2010; Andrault et al., 2011). Here we performed DAC melting experiments on the flakes of a pyrolitic mantle material originally prepared from gel. The size of the sample flakes was smaller than that of a laser beam, which enables complete melting of an entire sample piece. Because the mantle peridotite material is semitransparent, we covered the sample with laser absorbing materials such as graphite. Complete melting of the pyrolitic material was observed by ultrafast synchrotron X-ray diffraction measurements using a cadmium telluride (CdTe) detector at BL10XU, SPring-8. We have successfully determined the liquidus temperature of pyrolite at 35 and 51 GPa so far, and will discuss more details at the meeting.