Teaching notes


Audience: undergraduate- or graduate-level petrology or isotope geochemistry course.

Skills and concepts that students must have mastered: The students should be familar with the theory and practice of whole-rock isotopic data, particularly the Rb-Sr system. They should also know how to copy and sort data in Excel spreadsheets. Some familiarity with the geologic provinces of the western United States would also be helpful for this exercise.

How the activity is situated in the course: This activity could be used fairly late in an igneous petrology course to introduce links between mafic magmatism and mantle sources. Within an isotope geochemistry course, the activity could be used as an exercise to complement lecture material on using Sr isotopes as tracers for magma sources.


Content/concepts goals for this activity: Students who complete this exercise should be able to:
  1. use the radiogenic decay equation to solve quantitative problems related to the Rb-Sr system
  2. use the NAVDAT database to obtain and plot Sr isotope data on a regional map of the western United States and on a scatterplot
  3. interpret regional isotopic maps to infer information about the mantle sources of basaltic magmas

Higher order thinking skills for this activity: This exercise requires students to formulate hypotheses based on whole-rock isotopic data, and to compare/contrast data. Students are also required to apply the radiogenic decay equation for the Rb-Sr system to solve quantitative problems.

Other skills/goals for this activity: Obtaining and using data from online databases like NAVDAT informs the students about the powerful resources that have recently become available to the scientific community via the creation of digital cyberinformatics and cyberinfrastructure. Carefully guiding students into these databases, through the various steps required to screen, download, import, and use their data, empowers the students to think and act like scientists in a tangible, practical way.


The exercise is written so that questions the students must answer are highlighted. It is up to the instructor how the students' answers are evaluated.