Early cretaceous magmatism during extensional deformation within the Antarctic Peninsula Magmatic Arc

Early Cretaceous plutonic rocks at Creswick Peaks in NW Palmer Land, Antarctic Peninsula show evidence of synmagmatic crustal extension and deformation during emplacement and cooling at 141 ±2 Ma. Deformation textures, ranging from sub-magmatic phenocryst alignment to ultramylonite, are preserved in granodiorite. Large volumes of gabbro were intruded late in the kinematic history. Crustal extension compensated by magma emplacement has occurred, and a close correspondence of ages between the shear zone, granodiorite and gabbro suggests a rapid phase of crustal growth. Extensional structures are partially overprinted by mid-Cretaceous thrusting and compression.