Gondwanan Neoproterozoic tectonothermal events (Pan-African
and Brasiliano) are represented in northern mainland of Nova Scotia
by volcanic and sedimentary rocks assigned to the Jeffers and
Georgeville groups and by gabbroic to granitoid plutons. These rocks
comprise part of Avalonia, an exotic terrane in the Appalachian
orogen that was deposited in an arc-related environment along the
periphery of Gondwana prior to accretion to Laurentia. Lavas sampled
in the basal units of the Jeffers and Georgeville groups yielded
slightly discordant U–Pb zircon and monazite data that fall on
chords with upper intercept ages of 628 Ma and 617.7±1.6 Ma,
respectively. Syntectonic to late syntectonic plutons intruded into
these groups yielded U–Pb zircon ages of 606.6±1.6 Ma
and 603+9−5 Ma. The former intrusion
also yielded a concordant titanite age of 607±3 Ma. When
combined with previously published ages, these data indicate that the
back-arc deposition recorded in these groups lasted 10–15
million years (628–613 Ma) and was closely followed by
c. 613–595 Ma metamorphism, intrusion and
heterogeneous strike-slip related deformation. Assuming no
significant shuffling of fault blocks, the relative locations of the
Cobequid–Antigonish back-arc basin and the southern Cape Breton
Island volcanic arc are consistent with their genesis above a
north-west-dipping subduction zone. The age range of arc-related
magmatism in Nova Scotia is similar to that of Avalonian rocks in
southeastern Newfoundland and Britain, lending support to hypotheses
of Neoproterozoic linkages.