Cutting Edge > Petrology > Teaching Activities > Major Element Fractionation During Differentiation

Major Element Fractionation During Differentiation

Elizabeth King
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Illinois State University
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This activity was selected for the On the Cutting Edge Reviewed Teaching Collection

This activity has received positive reviews in a peer review process involving five review categories. The five categories included in the process are

  • Scientific Accuracy
  • Alignment of Learning Goals, Activities, and Assessments
  • Pedagogic Effectiveness
  • Robustness (usability and dependability of all components)
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This page first made public: Jul 17, 2008

Summary

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.

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Context

Audience

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

Skills and concepts that students must have mastered

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

How the activity is situated in the course

This is a stand-alone exercise.

Goals

Content/concepts goals for this activity

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

Higher order thinking skills goals for this activity

Other skills goals for this activity

Description of the activity/assignment

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).

Determining whether students have met the goals

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

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