Carbonatites are rare igneous rocks that occur worldwide and represent the primary source for niobium (Nb) and rare earth elements (REE), both of which are in increasing demand for their use in emerging eco-efficient technologies [1,2]. Apatite is a common accessory mineral in carbonatites and is capable of hosting a broad variety of (trace) elements, hence playing an important role in controlling the budget of these elements during carbonatite evolution [3,4].

This study provides further constraints on the partitioning behavior of trace elements between fluorapatite and carbonatite melt [5]. Piston-cylinder experiments were performed at 1250 °C and 1 GPa using four different starting material compositions with varying silica concentrations. Trace element concentrations of fluorapatite crystals and carbonatite melts were measured using LA-ICP-MS, and partition coefficients for a total of 41 trace elements were calculated.

First analyses show that silica in the system has a significant effect on the apatite/carbonatite melt partitioning of trivalent REE and the tetravalent trace elements.

[1] Simandl, G.J. & Paradis, S. (2018) Applied Earth Science 127, 123–152. [2] European Commission (2023) Study on the critical raw materials for the EU 2023: Final report Publications Office. [3] Hughes, J.M. & Rakovan, J.F. (2015) Elements 11, 165–170. [4] Chakhmouradian, A.R. et al. (2017) Lithos 274-275, 188–213. [5] Klemme, S. & Dalpe, C. (2003) American Mineralogist 88, 639–646.