Elizabeth King

Illinois State University

This activity is designed for a sophomore or junior level required course in petrology.

Students should have a basic understanding of how to use Microsoft Excel.

This is a stand-alone exercise.

This problem set reinforces quantitative problem solving skills using a spreadsheet and has the students think about mineralogical controls on magma evolution.

This problem set introduces some of the more advanced uses of Excel to not only calculate how the chemistry of a magma changes with crystallization but also to see how the liquidus assemblage can drastically change the evolution of the remaining magma. Once they have their calculations complete, students plot the results and answer questions on the geochemical trends observed through the crystallization sequence. This problem set reinforces quantitative problem solving skills using a spreadsheet and has the students think about mineralogical controls on magma evolution.

This exercise is modified from one that Clark Johnson assigned at University of Wisconsin. I find this exercise to be more instructive for some of the tricks and tools in Excel, but there are some interesting questions that can derive from it. This assignment is often the first time the light goes on that you can end up with different composition magmas depending on what minerals are crystallizing, and that depends on the pressure of crystallization. There are many more questions that could be asked, such as where does this model fall short? What could be added or considered to make this a more realistic simulation of fractionation (more trace elements or REE).

Students have met the goals of this activity if they thoroughly and accurately complete the problem set.