Theses and Dissertations

Issuing Body

Mississippi State University

Advisor

Gabitov, Rinat I.

Committee Member

Kirkland, Brenda L.

Committee Member

Dash, Padmanava

Committee Member

Paul, Varun G.

Date of Degree

8-9-2022

Document Type

Dissertation - Open Access

Major

Earth and Atmospheric Sciences

Degree Name

Doctor of Philosophy (Ph.D)

College

College of Arts and Sciences

Department

Department of Geosciences

Abstract

Fluid-rock interaction causes an exchange of isotopes or elements through various reactions. The rate of these reactions strongly depends on temperature. The interaction involves dissolution precipitation, chemical exchange reactions, redox reactions, diffusion, and their combinations. The goal of studying fluid-rock interaction is to understand the change in mineral chemistry of the rock materials when in contact with an aqueous solution. These processes occur in all regions of the Earth where aqueous solutions are found. This work is comprised of three independent studies which provide an understanding about crystallization processes under multiple hydrothermal conditions with geological and environmental applications.

In the chapter 1, subsurface rock and CO2-saturated brine reactions were evaluated under laboratory hydrothermal conditions when injected carbon dioxide is in contact with sedimentary strata at a planned sequestration sites at Kemper County Mississippi. Five rock samples were taken from different depths using core cuttings for experimentation. The results reveal no reaction of clay particles and CO2-rich fluid; in contrast, in samples from the depth of the unconformity, significant formation of secondary minerals occurred by reaction with the rock sample at the unconformity.

The second study focuses on the incorporation of uranium (VI) into the crystal lattice of calcite at hydrothermal conditions. This study was designed to understand uranium (VI) behaviors in a calcite-fluid system at elevated temperatures due to decay of radioactive waste from nuclear power plants. The results showed uranyl hydroxide formation was preferred at hydrothermal conditions, 120 – 350 oC. The incorporation of U6+ in calcite lattices was evaluated, though the data showed a limited amount of U6+ entrapment.

The third study focuses on quantification of the retention of Mg/Ca, Sr/Ca, and d18O during the aragonite-calcite transformation process as well as evaluation of the transformation rate. The results show partial retention of Mg and Sr during aragonite transformation to calcite in Mg-, Sr-free solutions, but no retention of d18O. Aragonite oxygen isotope composition was erased during mineral transformation because fractionation was controlled by temperature and the d18O of the bulk solution.

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