ND ISOTOPIC EVOLUTION OF THE TALTSON MAGMATIC ZONE, NORTHWEST TERRITORIES, CANADA - INSIGHTS INTO EARLY PROTEROZOIC ACCRETION ALONG THE WESTERN MARGIN OF THE CHURCHILL PROVINCE

The Taltson magmatic zone is a north-trending belt of Early Proterozoic granitoids exposed over an area exceeding 18,000 km2 in the Northwest Territories of Canada. Three petrologically and geochronologically discrete intrusive suites comprise the Taltson zone. These are the 1986 Ma Deskenatlata suite, the 1955 to 1925 Ma Slave suite, and the 1935 Ma Konth suite. The Deskenatlata suite is composed of biotite-hornblende diorite to granite and displays a more mafic geochemical character relative to the other two intrusive suites. Initial epsilon(Nd) values for the Deskenatlata suite range from -2.7 to -3.6. The Slave and Konth suites are compositionally heterogeneous to homogeneous leucocratic granitoids that contain numerous xenoliths of dominantly pelitic high-grade paragneiss and display a peraluminous granite mineralogy and geochemistry. Initial epsilon(Nd) values for the Konth suite cluster within -4.7 and -5.5 and are completely overlapped by the -4.1 to -6.0 range of the pelitic xenoliths. The Slave suite has initial epsilon(Nd) values ranging from -4.4 to -8.6, overlapping with part of the Nd isotopic evolution path of gneisses of the 2.0-2.3 Ga Buffalo Head terrane and western Archean Rae Province. Similar to its northern extension (the Thelon orogen) the Taltson zone is considered to be a composite pre-collisional continental arc (Deskenatlata suite) and a continent-continent collision orogen (Konth and Slave suites). Collision between the Buffalo Head terrane to the west and the Rae Province to the east would have caused tectonic thickening and melting of pelitic metasediments, Rae Province and possibly Buffalo Head terrane crust manifested as the Konth and Slave suites.