Teaching with the EarthChem Geochemical Database
Integrating Research and Education > EarthChem > Igneous Rocks and Tectonics > Step-by-step instructions > Part 3 - Graph the data

Part 3- Graph the data

With your group only, compare the three localities of the same tectonic setting:
  1. Plot MgO and K2O vs. SiO2 variation diagrams and a total alkalis-silica (TAS) diagram [(Na2O + K2O) vs. SiO2] that includes all of the data from the three localities. Create your charts so differences between localities are clear (i.e., use different colors or shapes for the different localities).
  2. Check if any of your spreadsheets contain a significant number of plutonic rock samples. For the locality with the most plutonic rock data, prepare another set of plots similar to those you made in step 1, but this time separate out the volcanic and plutonic rock samples (i.e., use different symbols or colors).
  3. Choose 10 samples from each of your dataset for graphing on a chondrite normalized rare earth element (REE) variation diagram. Be sure to plot abundances against atomic number so you don't introduce any kinks in the patterns where elements are skipped, and choose the x-y plot type that connects the datapoints (from each sample) with lines. Use chondrite normalizing values from Anders and Grevesse (1989); these can be obtained from the GEOROC database–click on "Chemistry" from the menu at the top-left of the page.

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