EARLY CRETACEOUS MAGMATISM DURING EXTENSIONAL DEFORMATION WITHIN THE ANTARCTIC PENINSULA MAGMATIC ARC

Early Cretaceous plutonic rocks at Creswick Peaks in NW Palmer Land, A ntarctic Peninsula show evidence of syn-magmatic crustal extension and deformation during emplacement and cooling at 141 +/- 2 Ma. Deformati on textures, ranging from sub-magmatic phenocryst alignment to ultramy lonite, are preserved in granodiorite. Large volumes of gabbro were in truded late in the kinematic history. Crustal extension compensated by magma emplacement has occurred, and a close correspondence of ages be tween the shear zone, granodiorite and gabbro suggests a rapid phase o f crustal growth. Extensional structures are partially overprinted by mid-Cretaceous thrusting and compression. Copyright (C) 1996 Elsevier Science Ltd & Earth Sciences & Resources Institute