ESS3605H – Selected Topics in Geochemistry

ESS3605H – Selected Topics in Geochemistry

Geochemical modeling of magmatic systems. 

This course is intended to provide students with a toolkit of methods for numerical modeling of magmatic processes.  The aim is that students will finish the course with the confidence that they can construct and apply simple geochemical models to test hypotheses about magmatic systems.  We will begin with a review of geochemical thermodynamics as a tool for the prediction of phase relations in magmas.  Spreadsheet-based models will be written to plot simple phase diagrams and calibrated against published experimental data. From there we will look at the role of various intensive parameters such as oxygen and sulfur fugacity in controlling the igneous geochemistry of sulfur, and the effects these have on the comportment of chalcophile elements in magmatic systems.  Subsequently we will see how the same principles can be applied in the use of a “black box” program like alphaMELTS to predict phase relations in complex magmatic systems. 

We will meet twice weekly, once for a 2 hour class and once again for a 2 hour practical session in which an assignment will be introduced.  Meeting times will be arranged at an introductory meeting during the first week of classes.  Readings will be assigned and students are expected to come to class with the readings already complete each week.

Grading will be based on weekly assignments and on participation in the practical sessions, where students are expected to show up ready to discuss the assigned readings and contribute to the development of the models we will use.

Topics, approximately by week and subject to revision:

1. Introduction to thermodynamics of igneous systems; Gibb’s free energy and the equilibrium constant
2. Acquiring and extrapolating data
3. Building a simple phase diagram (diopside-anorthite system)
4. Building a more complicated phase diagram (forsterite-fayalite system – Margules terms)
5. Empirical models of olivine crystallization from magmas (Roedder and Emslie)
6. Oxygen fugacity and the speciation of iron in magmas
7. Sulfur in magmas
8. Platinum-group elements in magmas – alloy solubility
9. Segregation of sulfide liquids from magmas – solubility of sulfide liquid in basalt
10. Distribution of chalcophile elements in sulfide-silicate systems
11. alphaMELTS