The Pelican Thrust Zone: basal detachment between the Archean Sask Craton and Paleoproterozoic Flin Flon – Glennie Complex, western Trans-Hudson Orogen

Abstract

The Pelican Thrust Zone is a 3-7 km-wide recrystallized mylonite zone, along which Paleoproterozoic arc volcano-plutonic and derived sedimentary rocks of the Flin Flon -Glennie Complex were thrust over an Archean package (Jan Lake Complex) consisting of ca. 3.1 Ga calc-alkaline orthogneisses, pelitic migmatites, and a ca. 2.45 Ga tholeiitic charnockite-norite intrusive suite. A regional northeast-plunging stretching lineation and a variety of kinematic indicators imply southwesterly transport, matching that of other coeval shallower crustal-level structures observed throughout the northern Flin Flon Domain and southern flank of the Kisseynew Domain (e.g., Sturgeon-Weir and Annabel Lake shear zones). Subsequent east-side-up displacement on the Tabbernor Fault, together with domal fold interference, has exposed the Pelican Window and mantling mylonite zone, where it has been seismically profiled along Lithoprobe transects. Tectonic windows also expose Archean rocks in the Glennie Domain to the west, where similar southwest-verging, recrystallized mylonite zones have been documented. Together, these zones record collision and underplating of the Flin Flon -Glennie Complex by the Archean Sask Craton during prolonged protocontinent-continent collision over a minimum 1826-1805 Ma interval.Résumé : La zone de chevauchement Pelican est une zone de mylonite recristallisée, d'une largeur de 3-7 km, le long de laquelle des roches volcano-plutoniques d'un arc datant du Paléoprotérozoïque et des roches sédimentaires dérivées du complexe de Flin Flon -Glennie ont été chevauchées par-dessus un ensemble archéen (le complexe de Jan Lake) qui est composé d'orthogneiss calco-alcalins et de migmatites pélitiques (âgées d'environ 3,1 Ga) ainsi que d'une suite intrusive charnockite-norite tholéiitique (âgée d'environ 2,45 Ga). Une linéation régionale d'étirement, à pendage nord-est et divers indicateurs cinématiques correspondent à un transport vers le sud-ouest, rejoignant celui d'autres structures contemporaines de niveaux crustaux moins profonds observées à travers tout le domaine de Flin Flon nord et le flanc sud du domaine Kisseynew (p. ex. les zones de cisaillement de Sturgeon-Weir et d'Annabel Lake). Un déplacement subséquent, le côté est vers le haut, le long de la faille de Tabbernor, avec une interférence de plis de dôme, a fait affleurer la fenêtre Pelican et la zone mylonitique qui la recouvre; elle a été déterminée par des profils sismiques le long des transects Lithoprobe. Des fenêtres tectoniques permettent aussi l'affleurement de roches archéennes du domaine de Glennie, vers l'ouest, là où ont été documentées des zones semblables de mylonites recristallisées à pendage sud-ouest. Ensemble, ces zones enregistrent la collision et le sous-placage du complexe de Flin Flon -Glennie par le craton archéen Sask au cours d'une collision prolongée entre le protocontinent et le continent au cours d'un intervalle d'au moins 1826 à 1805 Ma.[Traduit par la Rédaction] Ashton et al. 706

Petrogenesis of the 1.9 Ga mafic hanging wall sequence to the Flin Flon, Callinan, and Triple 7 massive sulphide deposits, Flin Flon, Manitoba, CanadaThis is a companion paper to DeWolfe, Y.M., Gibson, H.L., Lafrance , B., and Bailes, A.H. 2009. Volcanic reconstruction of Paleoproterozoic arc volcanoes: the Hidden and Louis formations, Flin Flon, Manitoba, Canada. Canadian Journal of Earth Sciences, 46: this issue.

“…1.87 Ga by intraoceanic accretion of the Snow Lake arc assemblage, the Amisk collage, the Hanson Lake block, and the Glennie Domain (Lewry and Collerson 1990;Lucas et al 1996). Tectonostratigraphic assemblages of the complex are fold-repeated, thrust-stacked, and tectonically overlie the Archean to earliest Paleoproterozoic Sask Craton above a basal décollement that was active as early as about 1.84 Ga (Ashton et al 2005).…”

Logan Medallist 2. Geophysics and Geology: An Essential Combination Illustrated by LITHOPROBE Interpretations–Part 1, Lithospheric Examples

“…23, 19). Ashton et al (2005) suggested that this may indicate reactivation of an early pre-existing tectonic discontinuity in the underlying Sask craton. Subsequent northeasttrending folds, which were likely caused by post-collisional shortening between the Hearne and Superior cratons, resulted in the domal structure that exposes the Pelican tectonic window.…”

“…The new geochronological dates from Ashton et al (2005), plus those from earlier work, and the detailed structural studies enabled Ash- (Figs. 23, 19).…”

“…However, understanding of the relationships was not strong, so further geological investigations were undertaken in the region of the Pelican Thrust zone to better elucidate the structural geology and tectonic development of the zone. Ashton et al (2005) described this work. Early workers had misidentified mylonite in the Pelican Thrust zone because mylonitic textures were rarely preserved due to widespread dynamic crystallization.…”

“…21a, b). The field studies enabled preparation of a detailed geological map of the area of the Pelican Thrust zone that showed structural relationships (figure 3 of Ashton et al 2005). For example, kinematic indicators such as winged δ-porphyroclasts (Fig.…”