The petrology of Archean and Proterozoic rocks at Cross Lake, Manitoba and the effects of the Hudsonian orogeny

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Rousell, D. H.
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The Cross Lake Group, consisting of basalt, conglomerate, and sandstone, lies unconformably on the basement biotite granodiorite gneiss. The area probably underwent two periods of folding and these likely correspond to the Kenoran and Hudsonian orogenies. The only recognizable effects of the Kenoran orogeny are the north northeasterly and north northwesterly - trending cross folds. The Cross Lake Group was folded, metamorphosed, and granitized during the Hudsonian orogeny. The major structural features were produced during the Hudsonian orogeny. These consist of a southwesterly-trending syncline and a northwesterly-trending syncline which merge and continue as one to the southwest and a major anticline situated between the two arms of the synclines. Numberous small-scales folds and lineations are present. Structures, in general, plunge steeply. Gabbro and anorthosite in the form of a sill at Pipestone Lake and a batholith south of the Minago River intrude the Cross Lake Group. These bodies were emplaced before or during the early stages of the Hudsonian folding... Previous writers suggest that the Churchill and Superior provinces in northern Manitoba are separated by a gneissic zone. This study indicates that the contact between the Cross Lake sedimentary - Volcanic belt ("Superior" province) and the gneissic zone is a gradational one. Rocks south of the contact consist of those of the Cross Lake group and migmatites and rocks north of the contact are migmatites and those of the gneiss complex. Evidence is presented which suggests that the Cross Lake area lies within the Churchill province and that the Churchill-Superior boundary lies south of Cross Lake. The contact is likely a gradational one where effects of the Hudsonian orogeny face into the Superior province.