THE GEOCHRONOLOGICAL FRAMEWORK OF THE IRUMIDE BELT: A PROLONGED CRUSTAL HISTORY ALONG THE MARGIN OF THE

ABSTRACT. Ion microprobe U-Th-Pb analyses of zircon from 40 granitoid rocks collected from the late Mesoproterozoic Irumide Belt in Central Southern Africa, along the southern margin of the Archean to Paleoproterozoic Bangweulu Block, provide a comprehensive set of age data for this complex orogen. The data indicate that the Irumide Belt is constructed on a basement of principally Paleoproterozoic (ca. 2.05–1.93 Ga) age with a subordinate Neoarchean (ca. 2.73 Ga) component, which is overlain by a platformal quartzite-pelite succession known as the Muva Supergroup. Previously published U-Pb detrital zircon data for the Paleoproterozoic Muva Super-group, which show age populations that match all of the pre-1.9 Ga basement components identified within the Irumide Belt, suggest that the pre-Muva basement was assembled as a coherent block by 1.8 Ga, which we refer to as the Bangweulu Craton. The southern margin of the Bangweulu Craton was then intruded by a previously unrecognized suite of biotite-bearing granitoid rocks between 1.66 and 1.55 Ga, not recorded elsewhere in the region, and was later the site of emplacement of voluminous granitoid magmatism during the Irumide Orogeny at between 1.05 an