Djw. Piper et al., DEVONIAN-CARBONIFEROUS IGNEOUS INTRUSIONS AND THEIR DEFORMATION, COBEQUID HIGHLANDS, NOVA-SCOTIA, Atlantic geology, 29(3), 1993, pp. 219-232
Field relationships and regional distribution patterns of igneous rock
s in the Cobequid Highlands provide information on sequential styles o
f deformation during the later Devonian and Carboniferous formation of
the Magdalen Basin. New mapping and aeromagnetic data show that large
diorite plutons have orthogonal outlines, suggesting that they occupy
pull-apart space. Diorites both cut and are cut by granite plutons, w
ith magma intermingling relationships suggesting co-existing magmas. L
imited dating suggests that most plutonism occurred at about the Devon
ian-Carboniferous boundary and was preceded by mid to late Devonian vo
lcanism in the eastern Cobequids, younger ages reflect alteration and/
or deformation events. Granite veins in diorite plutons show strike-sl
ip syn-magmatic deformation. Ductile thrust deformation of the western
granite plutons and Fountain Lake Group was followed by brittle fault
ing and emplacement of dykes along zones of weakness showing east-west
pull-apart. Magnetic data reveal that rocks similar to the major dior
ite plutons underlie much of the central and western Cobequid Highland
s and the northeastern part of the Minas sub-basin. The diorite pluton
s may be an exposed representative of mafic magma that underplated muc
h of the extensional Magdalen Basin. The structure of the Cobequid Hig
hlands is dominated by east-west faults parallel to the Cobequid-Cheda
bucto Fault that at times acted as transfer faults for major extension
al structures in the Magdalen Basin.