U-PB GEOCHRONOLOGY OF THE EASTERN ABITIBI SUBPROVINCE .1. CHIBOUGAMAU-MATAGAMI-JOUTEL REGION

U-Pb zircon, titanite, and baddeleyite ages are reported for 20 volcanic and plutonic rock units in the Chibougamau, Matagami, and Joutel areas of the northern Abitibi belt. Pretectonic magmatism occurred in three main pulses. Volcanic rocks of the Obatagamau Formation in the Chibougamau area were erupted at 2759 Ma. Following a possible hiatus in igneous activity, volcanism, accompanied by the emplacement of layered mafic intrusions, occurred in the Chibougamau, Matagami and Joutel areas in the period of 2730-2722 Ma. In the Chibougamau area, a slightly younger period of plutonism between 2720 and 2712 Ma is thought to be comagmatic with felsic volcanic rocks in the uppermost part of the Roy Group. Syntectonic intrusive rocks in the northern Abitibi belt range in age from 2701 to 2693 Ma. These ages are broadly comparable to ages obtained for syntectonic plutons elsewhere in the Abitibi belt, suggesting that tectonism associated with the Kenoran orogeny occurred at approximately the same time throughout the belt.