Date of Award
5-1-2025
Degree Name
Master of Science
Department
Geology
First Advisor
Hummer, Daniel
Abstract
The crystallization of iron sulfides, such as pyrite and pyrrhotite, is of great significance due to their common association with most ore deposits around the world. Understanding the formation of these iron sulfides can give as insight into the genesis of the associated ore deposits. This study examines some of the factors influencing the crystallization of these iron sulfides from acidic hydrothermal solutions, with a focus on variations in solution composition and temperature. Under a well-controlled laboratory environment, the effect of variations in concentration and temperatures were studied. Analytical methods such as Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were employed to measure crystal sizes and track morphological changes under various circumstances. The stability zones and crystal growth rates of pyrite and related minerals were determined through the application of the Scherrer equation. The results indicated that generally there was a strong correlation between the average pyrite crystal size and concentration of Fe in solution, but no strong correlation was observed in the average pyrrhotite crystal size and Fe concentration. It was observed that even for the pyrite, the correlation was strong in the lower temperatures (180⁰C and 200⁰C) for my studies but was moderate for the highest temperature(220⁰C). In contrast, the correlation between size and concentration for the pyrrhotite was very weak at the highest and lowest temperatures (180⁰C and 220⁰C) but was moderate at 200⁰C. This shows that concentration has an influence on the crystallization of the pyrite crystals but might not have a strong influence on the pyrrhotite. The findings in this work also suggested that, in general, lower concentration and higher temperature favored the formation of pyrite over pyrrhotite. These discoveries advance our knowledge of ore-forming settings and could be useful in mineral exploration, especially for deposits rich in iron sulfide. This research not only seeks to understand the influence of concentration and temperature on the crystallization of iron sulfides but also aims to serve as a launching pad to explore other parameters affecting their formation. Such insights could significantly benefit the geological and mining industries, as iron sulfides are commonly associated with ore deposits worldwide.
Access
This thesis is Open Access and may be downloaded by anyone.