Trace element composition in tuite decomposed from natural apatite in high-pressure and high-temperature experiments

Tuite has been suggested as a potential reservoir for trace elements in the deep mantle, but no evidence confirms this supposition. By using a natural apatite as starting material, the trace-element-bearing tuite large crystals were obtained under high-pressure and high-temperature conditions (15 GPa and 1800 K). X-ray diffraction pattern and Micro-Raman spectrum of the run product confirm that tuite was synthesized. The concentrations of trace elements in tuite crystals were analyzed by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). The rare earth element patterns of tuite show enrichment of light rare earth elements relative to heavy rare earth elements. Tuite shows high concentrations of Th and Sr, and negative anomalies of Rb, Nb, and Hf. The results show that tuite can accommodate a large amount of trace elements. Tuite might be an important host to accommodate trace elements if there is much apatite subducted into the deep mantle.