10. What is partial melting compared to the complete melting of a rock? Why is it that rocks do not usually experience complete melting inside the Earth? When rocks partially melt underground, briefly describe what happens to the rocks as it partially melts and what happens to the magma that is formed.

Partial melting occurs when only a portion of solid is melted. It is thus enriched in the chemical components of minerals with lower melting temperatures and the remaining unmelted portion of the rock is composed of minerals with highest melting temperatures. Partial melting preferentially enriches melts with incompatible elements.

Partially melted rock do not usually experience complete melting inside the Earth, due to their different chemical composition and their melting points.

It is thought that partial-melting processes play a major role in generating more-defined liquids from less-evolved ones, so that many basalts may be the result of partial melting in the upper mantle, and many granites may have derived partly or completely from the partial melting of continental crust (anatexis).With increasing temperature and pressure, the subducted oceanic crust (of basic composition) first undergoes metamorphism and then begins to melt or release watery fluids; this material rises into the overlying mantle, which may also begin to melt, giving rise to intermediate magma.  

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