HR: 0830h
AN: ED41C-1176    [PDF]
TI: Teaching contact metamorphism, isograds, and mixed-volatile reactions: A suite-based approach
AU: * Peck, W H
EM: wpeck@mail.colgate.edu
AF: Department of Geology, Colgate University, Hamilton, NY 13346 United States
AB: An important goal of teaching Introductory Petrology is to demonstrate how different kinds of approaches are integrated in studying petrologic problems. Depending on the goals of the study data used can be from the field, hand-sample, microscope, electron beam instrument, or mass spectrometer. A suite of samples with a known geographical and geological context can help students in drawing connections between different petrologic approaches, as the `geologic story' of the samples becomes a unifying theme. For teaching a unit on calc-silicates I use a suite of siliceous dolomite samples collected from the Ubehebe contact aureole (Death Valley, NV) as well as published data (Roselle et al., 1997; 1999) in a linked series of laboratory exercises and problem sets. The geology of the contact aureole is introduced in a three-hour laboratory exercise, where students identify the appearance of tremolite, forsterite, and periclase/brucite and the disappearance of quartz as the intrusion is approached. A concurrent problem set uses simplified mineral assemblage maps from the aureole. In the problem set students delineate isograds and determine the balanced metamorphic reactions by which the metamorphic minerals formed. Lecture material during this unit focuses on the physical properties of fluids in the crust and the mineralogical evidence for fluid-flow (with an emphasis on mixed-volatile reactions and T-XCO$_{2}$ diagrams). A concrete field example helps focus student attention on the interrelation of disparate approaches by which petrologic problems addressed. The Ubehebe suite then becomes a unifying theme throughout the course: the specimens or regional geology are used in subsequent laboratories and lectures when introducing concepts such as grain nucleation and growth, reaction overstepping, and replacement textures. A virtual field trip of the Alta aureole, UT (using field photographs, maps, and photomicrographs) concludes the unit. The geology of the Alta aureole is similar to that of Ubehebe, and the virtual field trip acts as a review that emphases the general usefulness of the approaches discussed.
DE: 1749 Volcanology, geochemistry, and petrology
DE: 3660 Metamorphic petrology
DE: 6605 Education
SC: Education and Human Resources [ED]
MN: 2003 Fall Meeting