Geophysical modelling of the Neoarchean Woodburn Lake and Paleoproterozoic Ketyet River groups, and plutonic rocks in central Schultz Lake map area, Nunavut

Abstract

Uranium exploration in the Thelon Basin has been has been revitalized by developments and discoveries reported by AREVA Resources Canada and Cameco Corporation in structurally intercalated metasedimentary and metavolcanic rocks of the Neoarchean Woodburn Lake group and early Paleoproterozoic Ketyet River group south and east of the Aberdeen Subbasin. This study integrates geophysics and geology to model a proposed basement klippe located south of Schultz Lake in central NTS map area 66A. Orthogonal high-resolution ground gravity transects were acquired in 2010, based on initial definition of the structure by a published 2004 geological map. These were integrated with high-resolution aeromagnetic and electromagnetic data from Forum Uranium Corporation, CanVec topographic data, and initial detailed geological observations in 2010 to 2011 by parallel studies under the Northern Uranium for Canada Project, part of the Geomapping for Energy and Minerals (GEM) Program The subsurface geology was computed by integrating surface geological contacts, unconstrained geophysical inversions and forward models. The unconstrained magnetic inversions defined several dyke arrays and suggest a deep seated mafic-to-felsic pluton tentatively assigned to the 2.6 Ga Snow Island Suite. High-resolution electromagnetic data provide strong constraints on near-surface lithology and steeply dipping faults, discriminating between Paleoproterozoic quartzite, Paleoproterozoic grey schist, and Neoarchean arkosic metagreywacke. The forward models, primarily constrained by generic rock properties and the clear gravity signal, support the klippe hypothesis. Further improvement could be achieved with a detailed gravity grid and more site-specific rock properties, and through collaborative integration and feed-back analysis of the full structural mapping data set.

Basement geology beneath the northeast Thelon Basin, Nunavut: insights from integrating new gravity, magnetic and geological data

“…) extends 80 km southeast to almost the TF, which was modelled by Tschirhart et al . (c). At the north end of section , the multiple‐fold Amer Group and RA (density 2.74 g/cm 3 ) are unconformably overlain by undivided Amarook and Thelon Formations.…”

“…Similar demagnetization effects characterize the Kiggavik camp that is also intersected by numerous hydrothermally altered, reactivated faults, has a markedly decreased magnetic susceptibility toward the Thelon Fault, and is at surface (Tschirhart et al . c; Fuchs et al . ).…”

“…Integrated geological–geophysical mapping of the northeast portion of the Amer Belt has identified four stratigraphic sources of strong linear aeromagnetic anomalies: Five Mile Lake, Three Lakes, Showing Lake, (Tschirhart et al . b; Calhoun et al . ), and upper Itza Lake formations (Jefferson et al .…”

“…The Hudson Suite forms thick, gently west‐dipping slabs of the magnetically intense Schultz Lake Intrusive Complex (SLIC; Miller and Peterson ; Scott et al . ; Tschirhart, Morris, and Jefferson c) that intrudes the Neoarchean Marjorie Hills assemblage on the southeast side of the sub‐basin (Jefferson et al . ).…”

“…a). Gravity and magnetic modelling suggest the magnetic SIS bodies are deep‐rooted cylindrical plutons (Tschirhart, Morris, and Jefferson a). Most of the SIS at surface is however non‐magnetic, weakly foliated granite.…”