Integrating Research and Education > Crystallography > Cpx Geobarometer > Teaching Notes

Teaching Notes


Audience: Mid to upper level undergraduate petrology course.

Skills and concepts that students must have mastered: This activity assumes students have already had a course in mineralogy and are familiar with the crystal structure of clinopyroxene. Students should also know how to use Excel.

How the activity is situated in the course: This activity is a stand-alone exercise and could supplement class lectures on crystallization of magma, basaltic magmas, alkalic magmatism of continental interiors, or igneous geothermobarometry.


Content/concepts goals for this activity: Students who complete this exercise should be able to:
  1. Use the American Mineralogist Crystal Structure Database to obtain crystal structures of natural clinopyroxenes from a suite of alkalic mafic rocks in Victoria, Australia.
  2. Use a crystallographic visualization program (such as CrystalMaker or XtalDraw) to dentify which crystallographic sites contain various elements within clinopyroxene.
  3. Use downloaded clinopyroxene compositions and the Excel program CpxBar to determine depths of clinopyroxene crystallization within the samples.

Higher order thinking skills goals for this activity: This exercise requires students to decide which calibration of the clinopyroxene geobarometer is the most appropriate for a suite of samples, based on the whole-rock compositions of the samples. Students are also asked to think about the effects of intensive variables (such as T and XH2O) on pressure estimates from the clinopyroxene geobarometer.

Other skills/goals for this activity: Students gain practice in (1) using crystallographic and petrology software to solve geologic problems, (2) using an Excel program to generate data, and (3) writing answers to open-ended questions.

Outcomes and Evaluation

This activity is formatted as a self-paced exercise where students can check their own answers by clicking on "Show answer" tabs. The exercise could be reformatted as a normal homework assignment without the answers given.