Date of Award

4-2020

Degree Name

Master of Science

Department

Geological and Environmental Sciences

First Advisor

Dr. Joyashish Thakurta

Second Advisor

Dr. Johnson Haas

Third Advisor

Dr. Peter Voice

Keywords

Sulfur, Michigamme, isotopes, Paleoproterozoic, paleoceanography

Access Setting

Masters Thesis-Campus Only

Restricted to Campus until

4-30-2021

Abstract

In the Upper Peninsula of Michigan, the Paleoproterozoic Michigamme Formation is composed of a thick package of metasedimentary rocks derived from foreland basin sediments which were deposited during the 1.8Ga Penokean Orogeny. These rocks contain significant, but variable amounts of texturally distinct sulfide minerals such as pyrrhotite and pyrite. We report a systematic relationship between δ34S values from sulfide mineral occurrences, and their stratigraphic locations regardless of texture and mineral composition. We suggest the sulfide minerals within the Michigamme Formation have inherited δ34S values from early sedimentarydiagenetic sulfides, therefore preserving primary isotopic signatures. The observed stratigraphic variation in δ34S values may indicate changes in δ34S values of the dissolved seawater-sulfate of the ambient Paleoproterozoic ocean coupled with periodic changes in the depositional basin during an episode of tectonic convergence.

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