Calculating Rb-Sr Isochrons
Indiana University~Purdue University, Indianapolis Author Profile
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This is a spreadsheet that I use in petrology to walk students through calculating Rb-Sr isochrons and talking about isotope heterogeneity and sampling at various scales. The example exercise is the Tuolumne intrusive series.
This activity is designed for a sophomore or junior level required course in petrology.
Skills and concepts that students must have mastered
How the activity is situated in the course
This is a stand-alone exercise.
Content/concepts goals for this activity
This activity is designed to help students understand how to calculate Rb-Sr isochrons and addresses isotope heterogeneity and sampling at various scales.
Higher order thinking skills goals for this activity
Other skills goals for this activity
Description of the activity/assignment
This is a spreadsheet that I use in petrology to walk students through calculating Rb-Sr isochrons and talking about isotope heterogeneity and sampling at various scales. The example exercise is the Tuolumne intrusive series. The file, available for download below, contains workbooks (see different tabs) with example isochrons and a spreadsheet of data for the homework problems.
Determining whether students have met the goals
Students have successfully met the goals of this exercise if they answer the homework problem set completely and accurately.More information about assessment tools and techniques.
Teaching materials and tips
Teaching Notes to Accompany Calculating Rb-Sr Isochrons (Microsoft Word 75kB Oct21 08) -- directions on how to calculate slopes and intercepts from the Excel spreadsheet, and how to use the slope to calculate an age.
Rb-Sr Isochron Examples and Homework (Excel 52kB Sep7 08) - this file contains examples and homework data for the exercise. Each example and homework data set is a separate tab in this Excel spreadsheet.
Cathedral Peak Granodiorite Graph (PowerPoint 2007 (.pptx) 39kB Sep29 09)
- graph of problem solution. As an alternative to SLOPE and INTERCEPT, the student can get this information by making a scatter chart of the data, and then inserting a linear trendline with equation displayed on the chart....this is pretty visual and helpful for many students.