HP-HT behavior of ankerite as a function of Fe content and cation disorder

Carbonates are the most important C–bearing minerals and key phases in the Earth’s carbon cycle. Their complex stability fields at HP – HT conditions are strongly influenced by both chemical composition and cation ordering. As in the lower mantle the carbonates composition is supposed to be enriched in Fe, the importance of a deep knowledge of the behaviour of (dis)ordered Fe-bearing carbonates at non-ambient conditions is evident. However, the stability of (dis)ordered ankerite Ca(Mg1-xFex)(CO3)2 (0≤x≤0.7) and its polymorphs at HP – HT is a poorly explored field. The present proposal is aimed at studying the crystal structure evolution of both ordered and disordered ankerites from room conditions up to 70 GPa and 800 K, by means of high-resolution SC-XRD experiments. The obtained results will allow to cover P – T conditions from (cold and hot) subducting slabs towards the Earth's mantle, integrating the phase stability of ankerite with the effect of cation disorder.