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Distal Skarn formation and metallogenesis: Geochemical and isotopic evidence from distal carbonate replacement and skarn-hosted ore bodies

Author Aaron Hantsche
Director of thesis Dr. Kalin Kouzmanov
Co-director of thesis Robert Moritz
Summary of thesis This project is designed to examine the geochemical characteristics of skarn forming fluids that commonly precedes sulfide mineralization of carbonate hosted Pb-Zn deposits. Distal skarns are metasomatized rock bodies that have no spatial or temporal magmatic source for metals or metasomatizing fluids. One goal of this project is to examine trace element characteristics in fluid inclusions that are preserved from both before and after skarn genesis. In order to understand the fluid pathway that formed these distal skarns, it is critical to identify the trace element evolution of the fluid. Additionally, it is of scientific and economic interest to discern whether or not the skarn forming fluid has the same source as the Pb-Zn mineralizing fluid. In addition to the geochemical characteristics of the fluid, the geometric shape of the skarn bodies with respect to the fluid flow pathway is poorly understood. More precisely, controls on the skarn body geometry are hard to identify due to limited subsurface exposure. Using geochemical characteristics from three sample locations in this study (Madan, Bulgaria; Elba, Italy; Serifos, Greece), efforts will be made to better understand the chemical controls of these irregular deposit shapes. Lastly, in addition to the use of fluid inclusion geochemistry, stable isotope geochemistry, and radiogenic isotope geochemistry, which have all been established through preexisting research, this project aims to use high Zn minerals such as sphalerite, a common mineral in these deposits, as part of a pilot study into the use of zinc isotopes. Currently, sulfur isotopes are primarily used to identify the metal source for sulfide deposits. This is acceptable and appropriate, but there are some cases where the metal source is decoupled from the sulfur source. By investigating the scientific properties of the Zn isotopic system, this project aims to understand isotopic fractionation of the metal directly. This portion of the study could provide a new technique to examine the source of Zn in Zn-bearing fluids, minerals, and rocks.
Administrative delay for the defence