Lukas Benjamin Klose

• This PhD thesis focuses on the investigation of high-temperature hydrothermal vent fluids from multiple vent sites between the North-Eastern Lau Spreading Center and the Tofua arc. The sampling area is located in the northeastern part of the Lau Basin which is affected by some of earths’ highest subduction rate, a highly complex microplate tectonic, an influence of hot spot material from the Samoan mantle plume as well as the subduction of the Louisville Seamount Chain. This study extends our knowledge of high-temperature hydrothermal systems in the North-East Lau Basin, in that it reports for the first time on the chemical and isotopic composition of vent fluids from Maka volcano and Niuatahi volcano. This cumulative PhD thesis highlights the compositional variability of hydrothermal fluids associated with different geologic settings. The newly reported vent fluid data as well as systematic spatial distribution of trace metals and metalloids adds to our understanding of hydrothermal processes and in the future may help improve the estimates of element specific fluxes associated with seafloor hydrothermalism.