GY202: Introduction to Petrology — Block #5

THE ISLAND ARC PROJECT

THE PROJECT:

         You will investigate the igneous, sedimentary and metamorphic systems in an island arc setting (Figures A & B) by following the mass incorporated in a parcel of oceanic crust through an island arc system. The parcel will be subducted; some of its mass will transferred to the mantle wedge overlying the down-going slab; that mass will be incorporated into magma which will rise into the crust; some of the magma will erupt, be eroded, reworked as sediment and deposited in a forearc basin; and some of the sedimentary rocks will get deformed and incorporated into the accretionary prism. Your investigation of this island arc system will involve geological relationships, hand sample observations, petrographic observations, simple theoretical calculations (based on fundamental principles of chemistry and physics), phase diagrams and analysis of geochemical data.

PURPOSES:

1)     To illustrate and apply petrologic techniques and approaches to natural rock systems.

2)     To become familiar with the anatomy and physiology of island arcs.

3)     To recognize the seamless connections between igneous, metamorphic and sedimentary systems and processes.

4)     To hone your ability to integrate large amounts of information and present a synopsis in a clear and organized fashion.

FORMAT:

         The project will be completed in the ten steps shown on the following page in Figure B. The steps will be divided into related segments as follows:

IGNEOUS SEGMENT:                                                         steps 4-7                                                     week 1 &2

SEDIMENTARY & VOLCANIC SECTION:          steps 8 & 9                                                week 2 & 3

METAMORPHIC SEGMENT:                                          steps 1-3 & 10                                         week 3

Each step is a discrete set of exercises, focusing on the processes operating in a limited part of the island arc system that is designed to be completed separately. However, because we are dealing with a system, each discrete step is related to the preceding steps, as well as the steps that follow.