The high PT stability of apatite and Cl partitioning between apatite and hydrous potassic phases in peridotite: an experimental study to 19 GPa with implications for the transport of P, Cl and K in the upper mantle

摘要

High PT experiments were performed in the range 2.5-19 GPa and 800-l,500°C using a synthetic peridotite doped with trace elements and OH-apatite or with Cl-apatite + phlogopite. The aim of the study was (1) to investigate the stability and phase relations of apatite and its high PT breakdown products, (2) to study the compositional evolution with P and T of phosphate and coexisting silicate phases and (3) to measure the Cl-OH partitioning between apatite and coexisting calcic amphibole, phlogopite and K-richterite. Apatite is stable in a garnet-lherzolite assemblage in the range 2.5-8.7 GPa and 800-l,100°C. The high-P breakdown product of apatite is tuite y-Ca_3 (PO_4)_2, which is stable in the range 8-15 GPa and 1,100-1,300°C. Coexisting apatite and tuite were observed at 8 GPa/l,050°C and 8.7 GPa/l,000°C. MgO in apatite increases with P from 0.8 wt% at 2.5 GPa to 3.2 wt% at 8.7 GPa.