Title

The Uranium-Lead Geochemistry of the Mount McRae Shale Formation, Hamersley Basin, Western Australia

Date of Award

Fall 12-2012

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Geosciences

First Advisor

W. Crawford Elliott

Second Advisor

Gerald D. Pollack

Third Advisor

Daniel M. Deocampo

Abstract

The late Archean Mount McRae Shale of the Hamersley Basin in Western Australia may record the presence of oxygen in the atmosphere before the Great Oxidation Event (2.4-2.3 Ga). Several prior studies (Anbar et al., 2007; Blum and Anbar, 2010; Duan et al., 2010; Kakegawa et al., 1998; McManus et al., 2006) have used isotopic systems to analyze the Mount McRae Shale and conclude that there was a presence of oxygen before the Great Oxidation Event. The purpose of this study is to determine if the U-Pb system can be used to see through later events to the initial conditions. The uranium-lead values of the Mt McRae Shale provide evidence of the mobilization of U and Pb gain. The geochemical disturbances have been linked to the tectonic activity (460 Ma) in the neighboring Canning basin, which could have possibly opened the geochemical system. In terms of the depositional environment the U-Pb data gathered here do not point to oxygenation of the atmosphere.

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