The influence of oxygen fugacity and chlorine on amphibole–liquid trace element partitioning at upper-mantle conditions

Abstract. The recycling of volatile and incompatible elements through the entire Earth's history is one most important processes for chemical evolution lithosphere. In this context, amphiboles are hydrous minerals playing a key role in differentiation crust–mantle system. We carried out amphibole–liquid partitioning (Amph/LD) experiments starting from alkali basalt with variable chlorine content doped 37 trace geochemical interest. Experiments were conducted an end-loaded piston cylinder apparatus at fixed pressure 1.4 GPa, temperature 1015 to 1050 ∘C, two different oxygen fugacity conditions (fO2; ΔFMQ ≈-2.6 (log fO2 [experiment] − log [FMQ buffer]) ≈+ 1.7). These approach those upper mantle chemically metasomatised by subduction-derived agents that may occur several geological settings. All runs show Ti-pargasites kaersutites, either as individual crystals or replacing former clinopyroxenes, equilibrium alkali-rich (4 wt %–6 %) silica-intermediate (52 %–59 melts. A comprehensive element dataset (LLEs – light lithophile elements, LILEs ion REEs rare Earth HFSEs high field strength actinides, transition metals, chalcophiles) has been determined glass amphibole laser ablation inductively coupled plasma mass spectrometer (LA-ICP-MS). Although melt polymerization major influence on Amph/LDs, we provide evidence changes both system Cl (up 0.88 also affect Amph/LDs their ratios. particular, higher lower Amph/LD values U Mo observed likely relation low capability incorporate more oxidized forms these cations. Amph/LDTh/Amph/LDU ratio positively correlated amphibole, while opposite behavior shown ratios other same charge ionic radius (e.g., Gd / Yb, Nb Ta, Pb Ba). Dimensional modification structure incorporation O(3) site origin variations. General implications our results discussed.