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.

Mazatzal–Labradorian-age (1.7–1.6 Ga) ductile deformation of the South Range Sudbury impact structure at the Thayer Lindsley mine, Ontario

“…The darker colour and higher U concentrations of these fractions may indicate primary igneous titanite, as described for samples elsewhere by Verts et al (1996), Stone (1998), andFrost et al (2000). However, Abraham et al (1994) suggested that Th/U ratios of -1 were characteristic of metamorphic titanite. Primary igneous titanite has not previously been documented in the norite of the SIC and is uncommon in mafic rocks in general (Frost et al 2000).…”

Late Archean regional deformation and structural controls on gold-quartz vein mineralization in the northwestern Slave Province, N.W.T., Canada

“…2) comprises rocks of the ca. 2.71 -2.68 Ga (U-Pb zircon ages; Abraham et al 1994) ARIC and the northwestern arm of the Anialik River greenstone belt (ARGB). This area is covered by the Hepburn Island map area (76 M) and has been the subject of a number of reconnaissance and lithostructural mapping projects (O'Neill 1924;Fraser 1964;Tirrul and Bell 1980;Yeo et al 1984;Jackson et al 1985), the most recent being a 1 : 30 000 scale Geological Survey of Canada MDA-NATMAP project (Relf 1993 and references therein).…”

“…The general geology of the Arcadia Bay area (Fig. 3) has previously been described (Abraham 1989), and a brief description of the major lithologies is given below; ages are quoted from Abraham et al (1994).…”

“…Abraham (1989 (Abraham et al 1994). The age of the dike also raises the possibility that some of the Sheeted Zone dikes might have been feeders to the felsic volcanics.…”

“…This deposit has been described as a system of simple quartz veins in shear fractures within the borders of the intrusion and associated with co-structural felsic dikes (Abraham 1989;Padgham 1992); it has since become evident that it lies within a major system of regionally controlled shear zones, hosting gold-quartz vein mineralization, and should be included in the shear zone type group. Abraham et al (1994) have provided precise U-Pb age constraints on the timing of gold mineralization and deformation in the Arcadia Bay area. They have proposed that the Kangguyak gneiss belt (McEachern 1993), which contains a regional-scale ductile high-strain zone, is a major crustal break (see also Relf et al 1994), and that deformation and gold mineralization in the Arcadia Bay area are temporally related to the development of this high-strain zone.…”