CALCITE-GRAPHITE THERMOMETRY OF MARBLES IN THE SHARBOT LAKE DOMAIN (GRENVILLE PROVINCE, ONTARIO)

Carbon isotope analysis was done on graphite and calcite from marbles in the Sharbot Lake domain of Ontario to quantify metamorphic temperatures of a package of Mesoproterozoic supracrustal rocks. Sampling was concentrated in the Carleton Place quadrangle where isograds have been mapped in marbles by Goodwin-Bell (CJES 2008). Preliminary data from ten samples have carbon isotope fractions between calcite and graphite averaging 3.30±0.46‰, consistent with high-temperature metamorphism. The samples analyzed to-date are from high-grade marbles with coarse graphite, and work is underway on separating minerals from low-grade marbles with fine-grained graphite. In the vicinity of the Wolf Grove structure (Carleton Place quadrangle) calcite-graphite temperatures average 767±85°C (n=6). In the southern Sharbot Lake domain samples average 782±85°C (n=4). Future work will concentrate on lower-grade marbles near the Lavant Gabbro and correlating calcite-graphite temperatures with mapped isograds.