Microstructures of epidote-prehnite bearing damaged granitoids (northern Victoria Land, Antarctica): clues for the interaction between faulting and hydrothermal fluids

Exhumed faults in granitoids along the Lanterman Fault-Rennick Graben Fault system (northern Victoria Land, Antarctica) show superposed ductile to brittle deformation and pervasive hydrothermal fluid-rock interaction. These processes triggered multiple slip events producing crosscutting epidote prehnite-rich fault veins, ultracataclasites pseudotachylytes of crushing origin. Combined microstructural minerochemical investigations on damage zones three types alteration: (i) albitization K-feldspar Ca-plagioclase; (ii) crystallization prehnite calcite veins; (iii) alteration magmatic phases by secondary hydrous minerals (e.g. chlorite, white mica, prehnite). The experienced various episodes strain weakening hardening, due precipitation within ultracataclastic intervals, at decreasing temperature conditions (200 < T°C 450) varying CO2 fugacity fluids. Cyclic epidote/prehnite cores caused cementation locking faults, concentration weaker horizons a progressive broadening zone. Our results indicate that co-seismic syntectonic fluid flow very likely occurred prior Cenozoic reactivation inherited anisotropies northern Land crust underlines its high potential for polyphasicity.