Date of Graduation

5-2023

Document Type

Thesis

Degree Name

Bachelor of Science in Geology

Degree Level

Undergraduate

Department

Geosciences

Advisor/Mentor

Potra, Adriana

Committee Member/Reader

Dumond, Gregory

Committee Member/Second Reader

Coridan, Robert

Abstract

A simple two-way stochastic mixing model is presented for analysis of the lead (Pb) isotope compositions of the North American Mississippi Valley-Type (MVT) districts of East Tennessee, Central Tennessee, and Central Kentucky. Four distinct mixing scenarios were run to critically evaluate the stochastic model and examine different hypotheses regarding the genesis of Central Tennessee and Central Kentucky MVT deposits. Additionally, Pb isotope analysis was conducted on sphalerite samples from the Central and East Tennessee MVT districts. Model and sampling results suggest that Central Tennessee and Central Kentucky ores likely formed by mixing of three fluids. In contrast to conclusions from previous workers, our results suggests that Central Tennessee and Central Kentucky deposits may have formed via mixing between Appalachian Basin brines and a unique source that is distinct from the Upper Mississippi Valley and Illinois-Kentucky trend. The possible third source has a composition lying along the Ozark Pb isotope trend and may have also contributed metals to the Central Tennessee ores. Alternatively, Pb isotope observations can be explained if Upper Mississippi Valley ore metals were derived from a single fluid which evolved over time.

Although it is still unclear whether these model results can be relied on for analysis of MVT ore compositions, the methods employed here present a promising means for Pb isotope analysis of sulfide ores. Stochastic generation of hypothetical ore deposits as the result of mixing between different sources of Pb has the potential to allow researchers to test their hypotheses regarding the nature of the mineralizing fluids in a more rigorous and semiquantitative manner. Nonetheless, further sampling is required before confidence regarding the origin of Central Tennessee and Central Kentucky ores is warranted.

Keywords

plumbotectonics; economic geology; strategic metals; numerical modeling; geochemistry

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