Olivine-rich veins in high-pressure serpentinites: A far-field paleo-stress snapshot during subduction

Field observations within the Atg-serpentinite domain of subducted ultramafic massif from Cerro del Almirez (SE Spain) reveal existence two generations abundant olivine-rich veins formed as open, mixed mode and shear fractures during prograde metamorphism. Type I were synchronous with development serpentinite main foliation (S 1 ) shearing, whereas II post-date S surfaces. These structural relationships indicate that, while Atg-serpentinites underwent ductile plastic deformation at temperatures 450°-600 °C pressures 0.7–1.7 GPa, they also experienced punctuated brittle behaviour events. The most likely due to fluid overpressures by release H 2 O brucite breakdown reaction for case (2 vol % O) a combination minor dehydration reactions related continuous compositional changes in antigorite (0.3 veins. failure well-defined paleo-stress field not significantly deformed after their formation. Comparison principal orientation inferred those peak metamorphic conditions rocks shows relative switch maximum minimum axes. can be attributed cyclic evolution stress, pressure fault-fracture permeability allowing stress reversal. • Two types Ol-rich fractures. coetaneous . Di faults Brittle reactions.