THE LATE NEOPROTEROZOIC GREENDALE COMPLEX, AVALON TERRANE, NOVA SCOTIA: AN EXAMPLE OF FEEDBACK BETWEEN IGNEOUS AND TECTONIC PROCESSES

The ca. 607 Ma Greendale Complex (GC) Antigonish Highlands, Nova Scotia is a local representative of extensive arc-related magmatism in the Avalon Terrane of the Appalachian orogen. The complex is a roughly semi-circular body with a diameter of ca. 5 km and is located between the Hollow and Greendale Faults, which were active during its emplacement. GC, which displays many of the characteristics typical of appinite suites, is primarily composed of steeply dipping, intrusive sheets of ultramafic, mafic and felsic composition which define a distinct layering that ranges from centimetres to metres in width. There are also abundant roof pendants and xenoliths of (Georgeville Group) host rock. GC is heterogeneous on all scales with abundant evidence for mixing and mingling. The ultramafics sheets are commonly discontinuous, occurring as boudins derived from early-formed layers. Felsic rocks occur in veins as either conjugate sets or networks and typically terminate in pegmatitic lenses. The mafic or intermediate rocks, which dominate the complex, are composed mainly of amphibole-rich porphyritic gabbros. Structural analysis indicates that the sheets were emplaced during dextral shear on the bounding faults. Each type of intrusive sheet has a geochemical equivalent in the Georgeville Group host rock, implying that active movement along the bounding faults tapped arc-related magmas of diverse compositions thereby facilitating the mixing and mingling of these magmas.