U-PB GEOCHRONOLOGY OF THE EASTERN ABITIBI SUBPROVINCE .2. NORANDA - KIRKLAND LAKE AREA

U-Pb zircon ages for 15 volcanic and plutonic units in the Noranda and Kirkland Lake areas help constrain the history of volcanism, plutonis m, sedimentation, and deformation in the south-central part of the Abi tibi belt. Volcanism occurred over an interval of at least 50 Ma, begi nning with the deposition of the volcanic and volcaniclastic units wit hin the Pacaud Structural Complex at 2747 Ma. Following a period of ap parent quiescence, magmatism resumed at 2730-2725 Ma with the eruption of volcanic rocks in the Normetal and Lac Abitibi area. From 2715 unt il about 2698 Ma, volcanism occurred sporadically throughout much of t he area, culminating in the eruption of the Blake River Group from 270 3 to 2698 Ma. Several large intrusive bodies yield ages that indicate that they are plutonic equivalents of the Blake River Group. Plutons t hat are considered to have been emplaced during the Kenoran orogeny gi ve ages that are only slightly younger than the youngest volcanic unit s of the Blake River Group, emphasizing the very rapid onset of Kenora n deformation following the cessation of volcanic activity. The Cleric y syenite, dated at 2682 +/- 3 Ma, postdates the main period of Kenora n deformation in this area and intrudes sedimentary rocks of the Kewag ama Group which contain detrital zircons as young as 2687 Ma. These da ta suggest that the Kewagama Group is the same age as late sedimentary sequences such as the Timiskaming Group and may have been deposited i n a similar tectonic setting.