Program > Browse abstracts by speaker > Flemetakis Stamatis

Phosphorus (P) plays a crucial role in mantle geochemistry, influencing elemental partitioning and redox processes. In peridotitic mantle compositions, P, affects the stability of phosphate minerals impacting the mobility of volatiles and trace elements [1]. Its oxidation state is controlled by oxygen fugacity (ƒO₂), which governs its speciation and distribution between silicate, phosphate, and metal melts [2]. Variations in ƒO₂ not only impact P mobility but also influence the onset of redox melting in the mantle. The redox transition from P⁰ to P⁵⁺ will strongly influence partitioning with mantle-derived carbonated silicate melts [3] and may exert some influence on their generation and composition.

Previous studies on P partitioning between metal and silicate melts demonstrated its dual lithophile or siderophile behavior [4], linked to redox-driven changes in its oxidation state. However, the conditions at which this transition occurs, and how it affects melt compositions, remain poorly constrained. To address this, we conduct high-pressure, high-temperature experiments across a range of ƒO₂, pressures, and melt compositions to investigate P behavior during mantle melting. Experiments were performed from 1 atm to 8 GPa at supra-solidus temperatures and a range of ƒO₂. Since P is highly soluble in metal melts, its release during the oxidation and breakdown of metal phases at the redox front results in its incorporation into silicate melts. This progressive transfer of P makes it a potential tracer of redox melting, linking oxidation processes to mantle-derived magma evolution.

Our results provide new constraints on the role of ƒO₂ in governing P mobility in the mantle and investigate its use as a geochemical tracer for redox melting and the formation of intraplate alkaline magmas. 

[1] Konzett et al., (2012), CMP; [2] Mallmann & O'Neill (2009), JPet; [3] Rohrbach & Schmidt (2011), Nature; [4] Gu et al., (2019), PEPI