Hi William, thanks for your hard work. Just wondering if you can make a lesson about REE spidergram and the behaviour of REE during magmatic evolution. That would be awesome.
Fantastic video! One question: for the fractional crystallization example, how can the entire system change in composition from beginning to end? In other words, if a 80% forsterite magma cools fully during fractional crystallization, how can the entire resulting rock be a different composition?
Hi Henry, thanks! This is because the evolution focuses on the liquid line of descent - liquid being the keyword. If we have a magma that crystallises olivine, yet through the process of fractionation, olivine is removed from the system as a cumulate (e.g., a dunite) - then the evolution of the liquid essentially 'restarts'. It is through processes such as this we can get sills that have olivine at the base and quartz at the top, despite the two phases never co-existing during batch crystallisation!
