Exploitable results Chemical transport in deep-crustal shear-zones and their country rocks monitored by stable isotopes The aim of this project is to trace the conditions and extent of fluid-rock interaction in deep-crustal shear zones using oxygen isotope data. This includes specification of fluid behaviour at different stages of shear-zone formation. The relevant geological material from East Antarctica, the Limpopo-Belt, the Baltic Shield and some other regions were subjected to main- and trace-element analysis (XRF, micro-probe) and oxygen isotope measurements (whole-rock samples and mineral separates). The combined chemical, mineralogical and isotope data allow the fluid-rock interaction at different metamorphic stages in the formation of the shear-zone to be modelled. The results show, that the main difference in fluid behaviour between the unaltered (granulite facies) gneisses and the retrogressed rocks is best explained in terms of the scale of fluid-rock exchange: the former are characterised by closed-system exchange (sample scale), while the latter, especially in shear-zones, underwent open-system fluid interaction (at least, tens of meter scale) with concomitant re-equilibration. Only the whole-rock (but not the mineral) systems generally preserve isotopic signatures acquired during large scale fluid interaction at peak conditions. The obtained data on different high-grade terrains allow discrimination of the fluid regime during several metamorphic events. For example, three stages of fluid-rock interaction are recognised in the Proterozoic Rayner Complex (East Antarctica). The first granulite-facies overprint with temperatures of about 180°C, is characterised by the evolved 18O/16O ratios, suggesting a sedimentary origin of the fluid rather than a mantle derived source. The second event, also under granulite-facies conditions (ca. 735°C) was accompanied by a pervasive flow of fluids with low 18O - content, implying a mantle source. The third, amphibolite-facies event (ca. 560°C) is developed in shear zones, but caused only scale mineral-mineral re-equilibrium in the country rocks. The isotopic data point to an inherited nature of the fluids. In concordance to the results from the Rayner complex the data from the Southern Marginal Zone of the Limpopo Belt point to a magmatic component in the shear-zone samples and to a slightly more enriched magmatic-metamorphic fluid in the country rocks. This succession from the rock-controlled (closed-system) fluid regime during the primary metamorphic event followed up by the externally-controlled (open-system) style of fluid-rock interaction during the second high-temperature event might be characteristic of the fluid regime in the lower continental crust. Searching for OpenAIRE data... There was an error trying to search data from OpenAIRE No results available