ContextAudience: 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.
GoalsContent/concepts goals for this activity: Students who complete this exercise should be able to:
- Use the American Mineralogist Crystal Structure Database to obtain crystal structures of natural clinopyroxenes from a suite of alkalic mafic rocks in Victoria, Australia.
- Use a crystallographic visualization program (such as CrystalMaker or XtalDraw) to dentify which crystallographic sites contain various elements within clinopyroxene.
- 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.