Transport and Storage of Potassium in the Earths Upper Mantle and Transition Zone: an Experimental Study to 23 GPa in Simplified and Natural Bulk Compositions

We have investigated the stability and composition of potassiumamphibole and its high-pressure breakdown product phase X insynthetic peralkaline and subalkaline KNCMASH (K₂O–Na₂O–CaO–MgO–Al₂O₃–SiO₂–H₂O)and natural KLB-1 peridotite bulk compositions between 10 and23 GPa at 800–1800°C. In the KNCMASH system, potassiumamphibole reaches its upper pressure stability limit at 13–15GPa at