Physical Sciences and Mathematics Commons^™

Sulfur Isotope Variations In The Elk Creek Carbonatite Complex, Southeastern Nebraska, Usa, Emily Campbell

Department of Earth and Atmospheric Sciences: Dissertations, Theses, and Student Research

The Elk Creek Carbonatite Complex (ECCC) comprises eight different units of carbonatite and silicate rocks, including a magnetite-dolomite carbonatite that hosts the largest niobium deposit in the United States. This study focused on interpreting the first set of sulfur isotopes from this system to decipher between magmatic and secondary processes. Using sulfur isotope variations I was able to discriminate between hypogene and supergene mineralization, and measure (1) formation temperatures (2) possible sulfur source (3) degassing effects on isotopic composition, and (4) post-magmatic alteration. The groundwork for mapping and interpreting iron oxide alteration is also laid out in this thesis.

Hypogene …

A New Method For Ultra-Low Sulfate Extraction And A Pilot Study In Arid Soils, Marisela Montelongo

Open Access Theses & Dissertations

Sulfur in soils is a crucial nutrient for all organisms including plants. Sulfate (SO42-), a water soluable anion, is a good source of this important element. Because of the importance of sulfur for agriculture, the use of sulfate has been well studied in temperate climate zones, and it is generally accepted that microbes play a critical role in controlling the availability of sulfate. Organically bound sulfur, such as sulfate esters and carbon-bonded sulfur, compounds that are generated and decomposed by microbes, are essential sulfur sources for plants under these conditions. For arid environments, knowledge of sulfate turnover in soils by …

Evaluation Of Cryptic Sulfur Cycling In Marine Sediments, Michael Ngari Mathuri

Open Access Theses & Dissertations

Despite the importance of marine sediments as a carbon sink and many efforts to integrate microbiological with geochemical and geological data, the understanding of microbial organic carbon mineralization processes in marine sediments remains incomplete. There is growing evidence for the existence of an unrecognized oxidative sulfur cycling (cryptic sulfur cycling) above, within and below of the main sulfate reduction zone. For example, sulfate exists in supposedly sulfate-free methanogenic marine sediments from the Aarhus Bay and Black Sea. This implies that sulfur cycling is an ongoing process in the deep biosphere. Quantification of cryptic sulfur cycling is a major challenge because …