Reactions of sub-arc mantle melt with mantle wedge and lower crust
Most volcanic arc magmas form from the partial melting of.mantle wedge above subducting.oceanic plates. The melts must migrate through the mantle wedge to reach the arc crust. However, little is known about chemical changes along melt migration pathways. This gap is explored by conducting melt-rock reaction experiments at 1.5 GPa pressure (depth ~50 km), and 1200 ⁰C & 1150 ⁰C. We used the synthetic primary mantle melt derived from partially melting phlogopite-pyroxenite source rock.
The peridotite rock does not melt at 1200 ⁰C at 1.5 GPa, but partial melting occurs in phlogopite-pyroxenite components of the mantle. The experiments simulated the flow-through of the partial melts by using a three-layer setup, including a glassy carbon trap at.the topmost portion of.the capsule, the starting melt at the bottom, which reacts with the peridotite and/or gabbro above it and eventually accumulates within the vitreous carbon trap. This is a novel addition to past experimental designs, improving our ability to analyse the melt composition after reactions with the rock.
Our study aims: (I) to understand the key sub-arc melt-rock reactions, (II) to evaluate geochemical trends resulting from melt-rock interaction under volcanic arcs and determine changes in melt composition, and (II) to compare experimental results with volcanic glass compositions from primitive arcs.