Regional geology and tectonic framework of the Southern Indian domain, Trans-Hudson Orogen, Manitoba

The collaborative federal-provincial Southern Indian Lake project in north-central Manitoba covered an area of more than 3500 km2 of the Trans-Hudson orogen. Regional-scale geological mapping, sampling, and lithogeochemical, isotopic and geochronological studies resulted in the identification of distinct assemblages of supracrustal rocks and varied episodes of plutonism. A granodiorite gneiss dated at ca. 2520 Ma is interpreted to represent the basement of the Southern Indian domain and is considered a separate crustal domain, named the Partridge Breast block. The Churchill River assemblage is composed of juvenile pillow basalt with intervening clastic sedimentary rocks, possibly a reflection of plume magmatism related to initial rifting of the Hearne craton margin. The Pukatawakan Bay assemblage consists mainly of massive to pillowed, juvenile metabasaltic rocks and associated basinal metasedimentary rocks. The Partridge Breast Lake assemblage is dominated by continental-arc volcanic and volcaniclastic rocks associated with basinal metasedimentary rocks. The Strawberry Island assemblage, consisting of arenite and polymictic conglomerate, is interpreted to have been deposited in a foreland-basin basin or intra-orogen pull-apart basin environment. The Whyme Bay assemblage is characterized by fluvial-alluvial orogenic sediments and is temporally linked to the Sickle Group rocks in the Lynn Lake greenstone belt. Granitoid rocks, dominantly monzogranite and granodiorite, range in age from ca. 1890 to 1830 Ma and occur throughout the Southern Indian domain, and intermediate and mafic intrusions of similar ages are also present. In this paper we integrate these new data into a tectonic framework for the Southern Indian domain of the Trans-Hudson orogen in Manitoba.

Crustal structure of the metasedimentary Kisseynew domain and bounding volcanic–plutonic domains, Trans-Hudson orogen, Canada

The Kisseynew domain (KD) is the largest component of the Paleoproterozoic Trans-Hudson orogen (THO) in Saskatchewan and Manitoba. It is bounded to the north by the Lynn Lake – Leaf Rapids (LL-LR) domain and to the south by the Glennie – Flin Flon (G-FF) complex. The THO was the focus of one of the study areas of Lithoprobe, Canada’s national Earth science research project (1984–2005). To further investigate the crustal structure of the KD and its bounding domains, this study reprocesses reflection line S3a across its northern boundary, analyses four 2.5-D gravity profiles, carries out 3-D gravity inversions for two areas, and replicates results from reflection lines 7 and 10 across the southern boundary of the KD. The reprocessed seismic section enhances the continuity of reflections within the crust. The reflectivity is representative of the complex tectonic development of the boundary zone and clearly identifies a subsurface deformation zone consistent with the boundary. The reflection section also shows that a lower plate (at about 30 to 50 km depth), interpreted as remnant lower crust of the G-FF complex, extends 30 km further northward than in the original section. Lines 7 and 10 illustrate the complex nature of the transition from the KD to the G-FF complex. The gravity analyses show that the variability and complexities of the boundary region between the LL-LR domain and KD, and the G-FF complex and KD, as indicated by the geological and Bouguer gravity maps, extend at depth throughout the crust.