Theses and Dissertations

Advisor

Gabitov, Rinat

Committee Member

Cui, Huan

Committee Member

Dash, Padmanava

Committee Member

Paul, Varun

Date of Degree

8-7-2025

Original embargo terms

Embargo 2 years

Document Type

Dissertation - Open Access

Major

Geosciences

Degree Name

Doctor of Philosophy (Ph.D.)

College

College of Arts and Sciences

Department

Department of Geosciences

Abstract

This dissertation investigates how elemental signatures in calcite reflect the conditions of its crystallization. Calcite, a widespread calcium carbonate mineral, has the ability to incorporate various trace and minor elements into its crystal structure. This property forms the basis for developing paleoenvironmental proxies used to reconstruct past conditions, including seawater composition, temperature, and pH. These geochemical records preserved in marine carbonates are essential for understanding long-term geological processes, such as mid-ocean ridge spreading, weathering, and biogeochemical cycling. While an extensive database of element-to-calcium ratios (E/Ca) in marine carbonates exists and is widely applied in paleoclimatic studies, factors beyond temperature and (E/Ca)seawater such as crystallography, growth rate, and fluid chemistry can significantly influence elemental incorporation in calcite. Despite previous studies, uncertainties remain regarding how crystallographic orientations, calcium concentrations, and carbonate ion concentrations impact the incorporation of trace and minor elements. This study addresses these gaps through a series of controlled laboratory experiments designed to: (1) examine the effect of crystallographic faces on (E/Ca)calcite, and (2) assess how variations in calcium and carbonate concentrations in the fluid influence the uptake of elements. Unlike previous studies, this work maintains a constant fluid composition throughout the overgrowth process by regularly replacing the growth medium. This allows for accurate in situ characterization of newly formed calcite layers. Experimental calcite overgrowths were grown on Iceland spar substrates in modified artificial seawater solutions. Microanalytical techniques, including LA-ICP-MS for depth profiling and SEM for morphological analysis, were used to investigate the chemical composition of the calcite. Results reveal how crystallography and fluid chemistry affect the incorporation of monovalent, divalent, and anionic species. The findings improve the understanding of element incorporation mechanisms in calcite, contributing to the development of more reliable paleoenvironmental proxies. Portions of this research have been published in Crystals, with additional findings under review in the same journal, and were also presented as an oral presentation at the Geological Society of America (GSA) conference.

Download

Available for download on Wednesday, September 22, 2027

Share

COinS