Tracing the origin of parental fluids and paleo-temperature distribution in fault zones: case studies from the Carboneras Fault (Spain) and Lemnos Island (Greece)

Multiple episodes of brittle deformation tend to increase the structural complexity of fault zones. This commonly results in the development of juxtaposed and non-coeval distinct Brittle Structural Facies (BSF) formed at different times, depths, and temperature. Indeed, these BSFs are characterized by an irregular distribution of inherited, syn-kinematic, and post-kinematic minerals, whose study provides useful information about the temperature conditions of (de)formation, and the origin of fluids circulating within faults. We combined X-ray diffraction (XRD) analyses and polytype determinations of whole-rock and several grain-size fractions (6-10 m, 2-6 m, 0.4-2 m, 0.1-0.4 m, and 160C). This multidisciplinary approach represents an innovative point of view for studying fluid circulation, mineral crystallization, and temperature evolution in complex fault zones, and it can be applied to both orogen scale faults and smaller fault systems.