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PhD Dissertation Defense: Xikai Wang

June 25 @ 11:00 am - 12:00 pm

Potassium and Lithium Isotopes in Marine Carbonates: Implications for Biological Effects and Hydrothermal Activities

Marine carbonates serve as valuable archives for reconstructing past seawater chemistry, which is essential for understanding the evolution of Earth’s surface. This dissertation focuses on evaluating marine carbonates as archives for seawater potassium (K) isotopes and using carbonate lithium (Li) isotopes as a proxy for hydrothermal activity. Chapter 2 introduces an improved dual-column K chromatographic protocol for carbonate materials to achieve high-precision K isotope analysis. Chapter 3 applies the developed column method to investigate K isotope compositions in the cultured brachiopod Magellania Venosa. The results from elemental, isotopic and synchrotron radiation analyses suggest that physiological controls, rather than environmental factors, dominate the K isotope fractionation between brachiopods and their culture medium. Furthermore, Chapter 4 uses Li isotopes in micrite records to constrain Jurassic hydrothermal activity. A combined Monte Carlo and Li-Sr dynamic box model suggests a 10–40% increase in hydrothermal activity during the Middle Jurassic, coinciding with the onset of Pangea fragmentation. Such active hydrothermal systems may have a profound impact on ocean chemistry and biogeochemical cycle in the Mesozoic.

Join Webinar: 98551353259

Details

Date:
June 25
Time:
11:00 am - 12:00 pm
Website:
https://unc.zoom.us/j/98551353259