Géologie et structure de la roche en place
Authors: St-Onge M R , Baragar W R A , Henderson I 
Published: March 2017

OF 4930 - This Open file contains: (1) a geological bedrock compilation (1:500 000 scale); (2) planar and linear structural point data; (3) lithology and mineral assemblage data; (4) sample number, radiometric age, interpretation, dated material, and method for
geochronology samples; (5) a comprehensive tectonostratigraphic legend for all Archean, Paleoproterozoic, and Neoproterozoic units and structures in the map area; (6) an up-to-date reference list for larger-scale source maps; and (7) key hydrographic features for the Cape Smith, Cap Wolstenholme,
Cap de Nouvelle-France, and Joy Bay region, northern Ungava Peninsula, Quebec. The purpose of this Open File is to provide a complete, analogue and digital, internally consistent, and georeferenced collection of spatial data that will assist interested parties in mineral exploration, environmental
studies, land use planning, and other investigations requiring up-to-date earth sciences information. The Open File map was compiled, modified and generalized from previously published Open File maps, A-series maps, and reports produced by the Geological Survey of Canada for the eastern, northern
and extreme western portion of the Ungava Peninsula and adjacent islands, and SIGEOM maps published by the Ministère des ressources naturelles du Québec for the western portion of the peninsula. The map shows a variety of units of Archean to Neoproterozoic age, which can be grouped into
the following bedrock tectonostratigraphic assemblages. In the southern portion of the map area, the lower-plate Archean Superior craton comprises dominantly felsic orthogneisses and plutonic units ranging in age between 3220+32/-23 - 2737±2 Ma. Unconformably overlying the felsic basement is a
suite of parautochthonous basal clastic sedimentary units, carbonatitic volcaniclastic rocks, and continental tholeiitic flood basalt and rhyolite (Povungnituk Group) associated with initial Paleoproterozoic rifting of the northern Superior craton. These units have yielded ages between 2038+4/-2 -
1959+3.1/-2.7 Ma. Stratigraphically overlying the initial-rift sedimentary and volcanic rocks is a younger succession of predominantly komatiitic to tholeiitic basalts (Chukotat Group) accumulated during renewed rifting along the northern continental margin and dated between 1887+37/-11 -
1870±4 Ma. The ages of the younger volcanic succession indicate that ca. 150 Ma elapsed between the onset of initial continental rifting and the subsequent rifting event. A south-verging tectonic boundary or crustal suture (Bergeron suture) separates the northern Superior margin strata from
allochthonous crustal elements of the Churchill plate to the north. Associated with and sitting in the hanging wall of the Bergeron suture are the crustal components of an obducted Paleoproterozoic ophiolite (Watts Group) dated as 1998±2 Ma. North of the Watts Group, a magmatic arc terrane
forms the leading edge of the Churchill plate and includes: fore-arc clastic deposits (Spartan Group), a dominantly volcanic sequence (Parent Group), and a dominantly plutonic assemblage (Narsajuaq arc). The volcanic and plutonic units of the arc terrane can be grouped into two temporally and
petrologically distinct, suites. The older suite includes calc-alkaline layered diorite-tonalite gneiss and tholeiitic to calc-alkaline basaltic andesite to rhyolite, and is dated between 1863±2 - 1845±2 Ma. It is interpreted as an island-arc assemblage built on Paleoproterozoic oceanic
crust (Watts Group above) and a rifted sliver of Archean continental crust. The younger suite comprises crosscutting, gneissic to massive, monzodiorite to granite plutons. It is bracketed between 1842+5/-3 - 1820+4/-3 Ma and is interpreted as having been emplaced in an Andean-type continental arc
setting. Archean and Paleoproterozoic units are intruded by massive, non-metamorphosed diabase dykes of Neoproterozoic age.