Petrology of serpentinites associated with the Romeral Suture Zone in the Central Cordillera (Colombia)

Serpentinized ultramafic bodies in the Romeral Suture Zone (Colombia) include lithologies from the Angelópolis Ultramafite (AU), Arquía Complex (AC) and Cajamarca Complex (CC). Serpentinites show evidence of three serpentinization events; AU serpentinites and partially serpentinized peridotites recorded a first hydration event within the ocean floor characterized by transformation of olivine to lizardite. A second serpentinization event is recorded in the AU, AC and CC serpentinites, which consist in the transformation of lizardite into antigorite during prograde metamorphism. A third alteration event led to the retrogression of antigorite to chlorite and antigorite to lizardite recorded in AU and AC serpentinites (450–320°C, <350°C). Pressure–temperature pseudosections show the following peak metamorphic temperatures: (i) 325–400°C at 10 kbar for AU serpentinites, (ii) 450–480°C at 15–20 kbar for AC serpentinites and (iii) 475–625°C below 28 kbar for CC serpentinites. AU and CC protoliths correspond to oceanic mantle peridotites (840°C, FMQ −0.4 to 0.19), whereas the AC represents mantle wedge peridotites (689°C, FMQ 0.6–0.8). We proposed that serpentinites from Angelópolis Ultramafite and Arquía Complex represent mantle from an ancient oceanic lithosphere and mantle wedge fragments, which were subducted and mixed in the subduction channel below the Early Cretaceous Quebradagrande Arc in NW South America, subsequently exhumed forming the Romeral Suture Zone.