Geological significance of U-Pb and Rb-Sr ages for two pre- tectonic granites from the central metasedimentary belt, Ontario.

The geological history of two pre-tectonic granitic rocks from the CMB was investigated by comparing U/Pb zircon and sphene and Rb/Sr whole-rock ages determined using samples collected from the same site. The emplacement ages for the Tallan Lake granodiorite (1254 m.y.) and Methuen quartz monzonite (1242 m.y.) are recorded by the U/Pb zircon method, whereas the corresponding Rb/Sr whole-rock ages are too young and appear to have been disturbed. …