JOURDAN Anne-Lise.pdf

This thesis evaluates the occurrence of sector zoning of oxygen isotopes and trace elements in natural α-quartz crystals from Alpine veins, aiming to identify the reasons for such zoning and its implications for fluid-mineral interactions during Alpine metamorphism. The study found that most quartz samples are strongly zoned in cathodoluminescence (CL) and exhibit corresponding zonations in trace element content, with aluminium, lithium, and germanium showing distinct distributions between growth sectors. Differences in δ18O values were measured between different faces, particularly in aluminium-enriched growth zones, but aluminium concentrations were found not to significantly affect oxygen isotope fractionations at 300°C. The results suggest that sector zoning in quartz crystals is real but not universal, and its occurrence may be related to kinetic processes and structural effects. In situ measurements revealed fine-scale δ18O zonations along growth paths, which can constrain fluid-rock interactions during Alpine metamorphism and provide insights into changes in fluid composition and origin.