Taltson basement gneissic rocks: U–Pb and Nd isotopic constraints on the basement to the Paleoproterozoic Taltson magmatic zone, northeastern Alberta

Abstract

The Taltson magmatic zone is a 300 km long, northerly trending belt of Archean to Paleoproterozoic granitic basement gneiss, amphibolite, supracrustal gneissic rocks, and voluminous Paleoproterozoic magmatic rocks underlying northeastern Alberta and the southwestern portion of the Northwest Territories. Taltson basement gneissic rocks exposed in the southern Taltson magmatic zone in northeastern Alberta are composed of a lithologically diverse suite of banded gneissic rocks, including amphibolitic gneiss, paragneiss, and metaplutonic gneiss. Metaplutonic gneissic rocks are predominant; six new U–Pb ages range from 2.4 to 2.1 Ga. Taltson basement also contains tectonic slices and layers of Archean gneissic rocks dated at 3.2 Ga, 3.1 Ga, and 2.6 Ga. εNd(2.2 Ga) values of –1.6 to –14.3 and TDM ages of 2.59–3.73 Ga from Taltson basement rocks (27 new analyses) overlap with values for the western Churchill Province and are interpreted to represent Paleoproterozoic recycling of the latter. The similarity in U–Pb ages and partial overlap in Nd isotopic compositions of the Taltson basement gneissic rocks and the Buffalo Head terrane are consistent with the two domains representing a single Paleoproterozoic crustal entity, which evolved from variable contributions of depleted mantle and preexisting Churchill Province crust. Greater contributions from a depleted mantle component in the Buffalo Head terrane are suggested by the Nd data. Taltson basement gneissic rocks and Buffalo Head terrane may represent earliest Paleoproterozoic magmatism associated with breakup of the western Churchill Province prior to Thelon–Taltson orogenesis.