Tectonometamorphism at ca. 2.35 and 1.85 Ga in the Rae Domain, western Churchill Province, Nunavut, Canada:: insights from structural, metamorphic and in situ geochronological analysis of the southwestern Committee Bay Belt

New constraints on the Paleoproterozoic evolution of the Rae domain, western Churchill Province, Nunavut, are provided through a linked structural, metamorphic, and in situ geochronological investigation of the southwestern part of the Archean Committee Bay belt. Within D-2 strain shadows proximal to a ca. 2.72 Ga synvolcanic pluton, S-1 is recognized as a northward-striking, cast-dipping foliation associated with west-vergent D-1 folds and possible thrusts. The D-1 structures are variably overprinted by a northeast-striking, southeast-dipping S-2 foliation associated with shallowly northeast-plunging, northwest-vergent F-2 folds. Whereas some textural observations suggest a cryptic, pre-D-1 thermal event that may be related to widespread ca. 2.61-2.58 Ga granitic plutonism, porphyroblast-fabric relationships in metapelitic rocks demonstrate that two main metamorphic events occurred, syn- to post-D-1 (M-1) and syn- to post-D-2 (M-2). Thermobarometric data and quantitative phase diagrams indicate relatively low-P, clockwise P-T-t paths culminating in post-tectonic growth of andalusite during both M-1 and M-2. Monazite inclusions in late- to post-D-1 garnet and staurolite yield a 2344 +/- 6 Ma age population that, on the basis of microtextural features, effectively dates M, metamorphism at a late stage of D, strain. Monazite growth occurred between 520 and 560 degrees C. Event M-2 is dated by matrix monazite that forms a 1838 5 Ma age population. The absence of magmatic rocks of appropriate age that could provide heat, together with clockwise P-T-t paths and porphyroblast growth at a late stage of both D-1 and D-2 contractional strain events, collectively point to metamorphism as a consequence of crustal shortening and thickening. The compressional forces that drove modest thickening events across the Committee Bay belt at ca. 2.35 and 1.85 Ga (average belt-wide ages) are considered to reflect far-field, upper-plate reworking during two orogenic events. The first event may have involved ca. 2.35 Ga collisional orogenesis (the "Arrowsmith" orogeny) following a period of continental arc magmatism on the western Rae margin. The second event is considered to be related to an early accretionary stage of the Trans-Hudson orogeny involving ca. 1.88-1.86 Ga collision of microcontinents located in the vicinity of Hudson Bay.