Sulfur isotope evolution and changing redox conditions in a mesozonal orogenic mineral occurrence in the lower Paleozoic rocks of the Anglo-Brabant fold belt, Belgium

摘要

A recently discovered mesozonal orogenic vein occurrence in the lower Paleozoic rocks of the Anglo-Brabant fold belt in Belgium has been the subject of a detailed sulfur isotope investigation. Based on the sulfur isotopic composition, a distinction can be made between sedimentary pyrite with a bacteriogenetic origin and hydrothermal pyrite that formed during tectonism and metamorphism. An increase in δ~(34)S values has been determined for pyrite during the main vein-forming stage. Thermodynamic calculations, based on chlorite geochemistry and fluid inclusion microthermometry, indicate that this increase could be due to more reducing conditions during sulphide mineral precipitation.