Deciphering the Neoproterozoic history of the Hollow Fault, Avalon terrane, mainland Nova Scotia

Recognition and deciphering of the early history of fault zones is difficul t because younger fabrics commonly overprint and obscure older ones. The Ho llow-Greendale Fault system in the Avalon terrane of the northern Antigonis h Highlands in mainland Nova Scotia has suffered many episodes of motion in the Paleozoic during development of the Appalachian orogen. Field relation ship and petrographic observations indicate that its Neoproterozoic history is preserved as ca. 610 Ma NE- and NW-trending ductile shear zones within the Georgeville Group contact aureole of the intrusive syn- to late-tectoni c Greendale Complex. Kinematic indicators within the NE-trending shear zone along the southwestern contact indicate dextral shear and are compatible w ith dextral shear indicators within the Greendale Complex and with the orie ntation of coeval regional F-1 fold structures within the Antigonish Highla nds. The NW-trending shear zone along the northeastern contact represents e ither a step-over fault a within a dextral shear zone or a zone of localize d transpression associated with the emplacement of the Greendale Complex. L ocal preservation of Neoproterozoic shear zone fabrics within the Georgevil le Group host rocks is attributed to the shielding effects of the proximal Greendale Complex, which acted as a rigid unit during Paleozoic deformation so that subsequent motion along the Hollow Fault was partitioned along the northeastern and southwestern contact of the complex. The Neoproterozoic h istory combined with paleocontinental reconstructions, indicates that the H ollow-Greendale fault system was part of an important regional strike-slip fault zone within a volcanic are regime along the periphery of Gondwana (Mu rphy et al., 1999a,b). (C) 2001 Elsevier Science Ltd. All rights reserved.