Fluid chemistry and fluid-rock interaction of Alpine veins, Central Alps

Metamorphic veins are one of the most important sources of information about fluid flow and fluid-rock interaction during orogenic processes and have been extensively studied from a structural, fluid inclusion and stable isotope perspective. It has been established that vein formation takes place in a continuum between fluid- and rock-buffered environments. Despite the considerable research, several important questions remain open, such as the chemical composition (solute inventory) of the fluids, the differences in solute content between aqueous and aqueous-carbonic fluids, the chemical similarities between typical metamorphic fluids and ore fluids responsible for gold mineralization, the lifetime of the fluid systems involved, and the relative importance of advective and diffusive processes in fluid-rock interaction and mineralization. The project will address these questions through combination of field and petrographic work, fluid inclusion analysis, geochronology and rigorous numerical modeling of geochemical fluid-mineral reaction. The work program will include the following tasks: (1) Generating a structural framework for the Alpine quartz veins from selected localities showing relationships of ductile deformation, faults and possibly multiple generations of massive and open veins. (2) Obtaining a comprehensive data set of the fluid chemistry of different fluid inclusion generations and assemblages preserved in the Alpine quartz veins (with emphasis on the differences between aqueous and aqueous-carbonic fluids) using LA-ICP-MS analysis of single fluid inclusions. (3) Generating new geochronological data for selected Alpine veins to constrain more precisely the formation age and the lifetime of the fluid systems. (4) Test the model that the Alpine quartz veins formed under rock-buffered conditions where diffusion processes were dominant, through novel numerical geochemical modeling. The results from the proposed study will significantly contribute to the understanding of the relative importance and scales of different mass transfer mechanisms in vein formation and metamorphic fluid flow in the upper crust.