2.70-2.58 Ga plutonism and volcanism in the Slave Province, District of Mackenzie, Northwest Territories

Abstract

New U-Pb zircon age dates are reported from eleven plutonic and seven volcanic rocks sampled in five greenstone belts in the Slave Province. Three of these belts are in the northwestern Slave Province (High Lake greenstone belt, Anialik River volcanic belt, and Napaktulik Lake volcanic belt) and the other two are located in the central Slave Province (Winter Lake supracrustal belt, Courageous Lake volcanic belt). Locally, the volcanic and plutonic rocks help constrain structural and depositional history within a belt, define the age of metallogenesis and allow for inter-belt correlation of units. Regionally, the age data support previous data sets, with the ages of volcanic rocks from greenstone belts falling between 2705 Ma and 2671 Ma. Plutonic rocks are in accord with general evolution from predeformational 2.70-2.64 Ga tonalites and diorites to 2.62-2.59 Ga K-feldspar megacrystic granites and finally to postdeformational 2.60-2.58 Ga two-mica granites. A distinct break in magmatic activity between 2.640 and 2.625 Ga remains evident in the data set for the plutons. The data also highlight inconsistencies in the time of formation of deformational fabrics recorded by plutonic rocks, suggesting that local strain regimes play a major role in fabric development, even within a single belt.