Clastic and chemical sedimentary sequences, Woodburn Lake group, Amarulik Lake to Tehek Lake, western Churchill Province, Northwest Territories (Nunavut)

Abstract

In the Amarulik-Tehek lakes area, the Archean Woodburn Lake group comprises psammitic greywacke interlayered with iron-formation and amphibole hornfels, the latter interpreted as metamorphosed rocks of mixed chemical and clastic sedimentary parentage. Amphibole hornfels extends northward to the Meadowbank gold deposits and includes rocks previously mapped as intermediate volcanic rocks. New mapping implies that a reported age of ca. 2.8 Ga for volcanic rocks is invalid, as the area is underlain by greywacke, albeit with volcanogenic components. A structural dome, centred on Amarulik Lake, is defined by outward-dipping bedding and schistosity, and encompasses smaller scale structural complexities such as concentric dip reversals. Orthoquartzite and metacarbonate lie near the eastern margin of the dome and the distribution of units suggests fold interference patterns. Mineral assemblages are typical of amphibolite-facies metamorphic grade, whereas to the north, chloritoid-bearing greenschist-facies assemblages prevail, suggesting that the Meadowbank gold deposit lies near the greenschist- amphibolite transition.