Geochronological constraints on late Archean magmatism deformation and gold–quartz vein mineralization in the northwestern Anialik River greenstone belt and igneous complex, Slave Province, N.W.T.

Abstract

Three phases of the Anialik River igneous complex (ARIC) give U–Pb zircon ages in the range −2705–2683 Ma, and three units from the adjacent northwestern Anialik River greenstone belt (ARGB) give ca. 2678 Ma ages. Titanite from unsheared ARIC rocks crystallized during localized metamorphism and deuteric alteration between 2693 and 2683 Ma. Hydrothermal titanite in wall rocks to gold-mineralized shear zones crystallized during early shear zone development (2670 ± 1 Ma) and was subsequently locally altered to rutile, with gold occurring within the rutile-bearing assemblage. Unaltered second-generation hydrothermal titanite, overgrowing the rutile assemblage, crystallized during later brittle–ductile movement (2656 ± 2 Ma) and provides a minimum age for gold mineralization. Relatively high 207Pb/204Pb ratios of Pb in gold-associated galena suggest that it was partly derived from significantly older crustal material, possibly underlying the igneous complex and greenstone belt. This interpretation is consistent with other evidence for the existence of > 3.0 Ga crustal rocks to the west of the study area. A late crosscutting granite gives an age of [Formula: see text] and is therefore part of the Pan-Slave tectono-thermal event. These results, and other data for the Slave Province, indicate temporal variations in the development and deformation of predeformational greenstone belts. The new ages show that regional deformation and metamorphism in the northwestern Slave Province followed shortly after major magmatism, and that gold mineralization might have occurred during the late Archean accretion of the greenstone belt and igneous complex to an older crustal domain to the west.