The geochemical nature of the igneous rocks of the Sharbot Lake domain, Central Metasedimentary Belt, Ontario.

Two bimodal mafic-silicic suites of igneous rocks, the Sharbot Lake volcani c rocks and the Lavant Igneous Complex, are identified geochemically in the Sharbot Lake domain of the Central Metasedimentary Belt in Ontario, and th eir genesis and thermotectonic environment are evaluated. The Sharbot Lake volcanic rocks comprise a series of basalts characterized by light rare-ear th element (LREE) depletion and relatively high concentrations of Sigma Fe2 O3, TiO2, MnO, V, and Y, together with rhyolites and silicic pyroclastic ro cks. They are intruded by rocks of the Lavant Igneous Complex, which compri ses tholeiitic gabbros characterized by LREE enrichment and low concentrati ons of Sigma Fe2O3, TiO2, MnO, V, and Y, and granitoid rocks. The trace ele ment signatures of the mafic rocks of the Sharbot Lake volcanic sequences a re most like those of back-arc tholeiitic basalts, and those of the Lavant Igneous Complex are comparable to those of low-K tholeiitic basalt suites. The trace element signatures of the silicic rocks associated with both suit es are typical of those formed by crustal melting. Volcanic sequences with trace-element signatures very similar to those of the Sharbot Lake suites h ave been previously described in the Belmont and Grimsthorpe domains of the Central Metasedimentary Belt, suggesting that the three domains all belong to the Bancroft - Elzevir - Mazinaw - Sharbot Lake superterrane. The litho logical, structural, and igneous characteristics of this superterrane sugge st that it represents part of a complex back-arc basin underlain by areas o f rifted and attenuated continental crust and oceanic crust.