Katharina Schier

• The topic of this PhD Thesis is the application of trace elements such as rare earth elements and yttrium (REY), neodymium (Nd) isotopes and gallium (Ga) in combination with its geochemical partner Aluminum (Al) as geochemical proxies in various types of marine chemical sediments from Precambrian to modern formation ages. The marine chemical sediments investigated comprise Precambrian (banded) iron formations ((B)IFs), manganese formations (MnFs) and stromatolitic carbonates, and modern authigenic carbonates from methane seep sites and hydrogenetic ferromanganese (Fe-Mn) crusts. Trace element systematics of these potential geochemical archives can provide valuable insights into the physico-chemical conditions under which their formation occurred and allow conclusions regarding the trace element budget of the precipitating fluid. REY distributions and Nd isotope compositions were determined for Paleoproterozoic marine chemical sediments from the Transvaal Supergroup in South Africa to allow insights into (i) the physico-chemical conditions that prevailed during their formation and (ii) the dominant REY sources to the early ocean prior to the Great Oxidation Event (GOE). Trace element systematics of modern seep carbonates from the Northern Norwegian continental margin show that REY also represent a powerful tool for screening a sample set of marine chemical sediments for detrital components and, thereby, identifying the purest and most reliable geochemical archives. Gallium-Aluminum systematics of modern marine hydrogenetic Fe-Mn crusts were also investigated in order to better understand the geochemical behavior of the Ga-Al pair in the modern marine environment, especially in the presence of Fe(III)-oxyhydroxides.