Question: where do volatiles cause partial melting of the mantle

title: Partial melting
text: Partial melting is an important consideration in geology with respect to the chemical differentiation of crustal rocks . Virtually all rocks on Earth derive from material from the interior of the earth that has been partially melted . The main places where partial melting occurs are subduction zones , mid-ocean ridges and hotspots . In all these places partial melting is often associated with volcanism , although some melts do not make it to the surface . Partial melts are thought to play an important role in enriching old parts of the continental lithosphere in incompatible elements . Partial melts produced at depth move upwards due to the compaction of the surrounding matrix .