Magma production beneath mid-ocean ridges: Using numerical models to
evaluate the solidus
Abstract
Over 95% of volcanism on Earth occurs at mid-ocean ridges (MORs) where
tectonic plates diverge. How melt is produced depends on the mineral
composition and water content. However, it has proven challenging to
understand how melting changes when one or more minerals have completely
melted. This project examines differences on MOR melting that come with
different assumptions in solidus changes with exhaustion of one of the
component minerals, clinopyroxene (cpx). To do this, we constructed 2D
numerical models of temperature, mantle flow, and melt production at
MORs. We ran several models with different amounts of temperature shift
in the solidus with loss of cpx. Using zero shift as a baseline, melting
starts around 80km depth and peaks at 35km, exhausting cpx, lowering
melt output. A second smaller melting region develops more shallowly
where there is no cpx. Additional trials in changing the shift in
solidus with loss of cpx were done with varying amounts of mantle
hydration. For all trials, total melt decreases with larger shifts in
solidus. The shallower melting disappears as greater shifts are made.
Increasing hydration allows melting to start at deeper depths, but has
little effect on the total amount of melt production.