Mid-Mesoproterozoic granitoid rocks in the North Bay area, Grenville Province, Ontario; Radiogenic age and isotopic studies: Report 14

Granite from the Powassan and Mulock batholiths, both lying within the parautochthonous part of the Central Gneiss Belt of the Grenville Province, have U-Pb zircon ages of 1270 ±3 and ca. 1250 Ma, respectively. These and other coeval metaplutonic rocks in this belt have A-type affinity and thus contrast with coeval, predominantly calc-alkaline plutonic rocks in the Central Metasedimentary Belt some 200 km to the southeast. The difference in character may be accounted for by their relative positions with respect to the pre-Grenvillian margin of Laurentia. If true, this relationship supports the interpretation that subduction polarity in the Mesoproterozoic, preceding closure at 1.2 Ga, was toward the present-day northwest. INTRODUCTION T paper reports new ages for granitoid rocks in the northwestern part of the Grenville Province in Ontario, and compares these rocks with coeval plutonic rocks some 200 km to the southeast. The names used for lithotectonic divisions within this part of the province have been drawn from several 2001-F8 A. Davidson and O. van Breemen 1 CURRENT RESEARCH RECHERCHES EN COURS 2001 Article Article Titles Titres Purchase Information Information pour acheter