Sharbot Lake terrane and its relationships to Frontenac terrane, Central Metasedimentary Belt, Grenville Province: new insights from U–Pb geochronology

Abstract

The Sharbot Lake terrane of the Central Metasedimentary Belt in Ontario comprises marbles, minor tholeiitic basalts and siliciclastic rocks, metamorphosed at low to moderate degrees, and is intruded by several suites of mafic to felsic plutons. Gabbroic and associated monzogranitic phases of the Lavant complex in northwestern parts of the terrane yield ages of 1224 ± 2 Ma for zircon and monazite, and 1221–1211 Ma for titanite. The Wolf Grove structure, a gneissic domain in the northeastern part of the area, was migmatized and intruded by granites at 1168 Ma prior to its tectonic juxtaposition on amphibolites and marbles of the Sharbot Lake terrane. Correlative events recorded by gneiss, quartzite, and marble from Carleton Place farther east stress the strong affinity of the Wolf Grove structure with rocks of the Frontenac terrane. The 1156 ± 2 Ma posttectonic Maberly stock intrudes rocks near the boundary zone between the Frontenac and Sharbot Lake terranes, suggesting that the two terranes were linked by 1156 Ma. The distribution of U–Pb ages for titanite, monazite, and rutile throughout the area emphasizes the distinctive metamorphic evolution characterizing different domains of the region, documents the lack of 1168 Ma metamorphic overprint in western domains, records the main 1168 Ma high-grade event and slightly younger subsidiary events in eastern domains, and indicates local resetting events. The combined data underline the geological complexity of the eastern Central Metasedimentary Belt, confirming the existence of significant compressional and metamorphic events in the period 1170–1160 Ma.