RECOGNITION OF SHEAR ZONES WITHIN THE WESTERNMOST FROTENAC TERRANE OF THE CENTRAL METASEDIMENTARY BELT, GRENVILLE PROVINCE, ONTARIO

In the Central Metasedimentary belt of the Grenville orogen, we recognize two shear zones that cut across Christie Lake in the westernmost portion of the Frontenac terrane. The shear zones are steeply dipping and strike to the northwest. Both shear zones are oriented at a high angle to the Maberly shear zone, the boundary between the Sharbot Lake and Frontenac terranes, which is mapped ~ 6 km northwest of Christie Lake. The eastern shear zone parallels the lake's northeast shore. The western shear zone was previously mapped as a ~ 10 km long lineament extending from a ~ 1.08 Ga syenite pluton in the southeast to the Maberly shear zone to the northwest (Wynne-Edwards, 1967). Asymmetric feldspathic porphyroclasts in the western shear zone record west side – up shearing. This shear zone defines the contact between metagrabbro, exposed to the west, and paragneisses exposed to the east across the north shore of the lake. Detailed geologic mapping on Christie Lake reveals intact packages of sedimentary rocks metamorphosed under upper amphibolite-facies to granulite-facies. These rocks are subdivided into three shear zone-bounded lithostratigraphic domains: the western, central and eastern. Domains are characterized by uniform composition and similar attitudes. The western domain exposes quartzo-feldspathic gneiss and marble. The central domain exposes steeply dipping east-west trending quartzo-feldspathic gneiss, marble, and amphibolite. The eastern domain is characterized by quartzo-feldspathic and garnet-bearing gneisses. Although preliminary, our mapping efforts suggest the presence of the previously unrecognized eastern shear zone which cuts across Christie Lake.