Volcanology lecture 7: fractional crystallisation

What is magma differentiation?

A melt evolves into many different but related compositions

Where does magma differentiation most commonly take place?

In a magma chamber

As the temperature of a basaltic melt decreases, what mineral crystallises first?

Spinel

As temperature decreases in a basaltic melt, what mineral crystallises last?

Plagioclase

Explain gravity setting during fractional crystallisation

As the melt cools, minerals will crystallise and solidify at different times. When a specific crystal mineral forms, it will be more dense than the melt and sink due to gravity. The process will repeat

Name the law which controls the settling velocity of the crystal

Stokes law

What is assimilation?

A xenolith has a lower melting point than the melt so melts and becomes incorporated into the magma