Supervisor: Ronald Miletich (IfMK, University of Vienna), in collaboration with Anna Likhacheva, Sergey Rashchenko, and Anton Shatskiy (IGM, Siberian Branch of the Russian Academy of Sciences, Novosibirsk)

Funding Situation: supervisor has secured funding

Project outline: Evidence for the existence of alkali-containing carbonates in mineral inclusions and the presence of K-rich carbonatitic melts in the upper mantle raised the attention to the role of potassium within the Earth's deep carbon cycle. Following the possible models for the origin of mineral inclusions in diamonds, carbonate phases can either be entrapped as minerals crystallized syngenetically or alternatively represent daughter phases nucleated on cooling from melt inclusions. The Austrian-Russian joint research project, involving research groups in Vienna and Novosibirsk, aims at experimental in-situ investigations, which tackle the structural crystallography of binary and ternary key phases, prove the existence of non-quenchable subsolidus phase transitions, and determine the thermomechanical properties of the phases in order to establish phase-formation pathways in pressure-temperature space. Samples will be synthesized at high-pressure conditions using multi-anvil large-volume presses, and thus investigated by means of diamond-anvil cell technology using in-situ vibrational spectroscopy and X-ray diffraction methods. Synchrotron based investigations is complementary to extensive high-pressure-high-temperature investigations using laboratory-based equipment. In a wider context this study will prove, if potassium-bearing carbonates can be considered for the transport and storage of oxidized carbon species at mantle conditions.