Metasomatism and the tectonics of Santa Catalina Island: testing new and old models

Catalina_3_2012

Ripper’s Cove at the mouth of the Valley of Ollas

What: Petrology and geochemistry of subduction-related metamorphic rocks.

When: July 8-August 6

Where: Field work on Santa Catalina Island off the coast of Los Angeles California followed by some lab work in Oberlin, Ohio. Santa Catalina is a channel island located within Los Angeles County, approximately 20 miles offshore. Catalina is a nearly pristine island ecosystem with several species of plants and animals unique to the island. Most of Catalina is owned and managed by the Catalina Conservancy and is one of the only parts of coastal southern California that has never been developed..

Who: Six students, Zeb Page (Oberlin College), Emily Walsh (Cornell College), and Sarah Penniston-Dorland (University of Maryland)

Project Overview and Goals

The metamorphic rocks of Santa Catalina Island, California, have been used as a natural laboratory to study fluid flow and metasomatism in subduction zones for over 20 years. Many models of the metamorphic record left by subduction zones and the behavior of fluids along the slab-mantle boundry were developed on Catalina and depend on a tectonic interpretation of the island’s metamorphic rocks that has recently been called into question. We plan to test existing tectonic and geochemical models of subduction zones through six research projects on the island.

Potential Student Projects

We propose to focus our field efforts on two mélange zones on Catalina, one in the Valley of Ollas in the structurally highest amphibolite-facies unit, another along Cottonwood Canyon in the lower-grade blueschist-facies unit, although these locations are flexible based on our preliminary field observations. Students will work collaboratively on detailed mapping projects of these relatively small regions and identify promising blocks of metamafic and metasedimentary material for further study. Our preliminary plan is to have two groups of three students each working on parallel projects in different mélange zones. Two of the students from each group will focus on thermobarometry for their individual projects, whereas one student from each group will take on a more geochemical study that is complementary to the P-T work.

Logistics/Field Conditions

We will be camping on Catalina in relatively rustic conditions (no electricity/refrigeration) with cold nights and hot days. Field work will include hiking in steep terrain in a sensitive environment.

Recommended Courses/Prerequisites

Mineralogy, petrology, structural geology

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