Superior Craton - Southeastern Superior Province

Southeastern Superior Province

The southeast part of the Superior province is divided into the following subdivisions: to the north is the E-W oriented Opinaca subprovince located between the La Grande and Ashuanipi, and to the south is the Opatica Subprovince.

Detrital zircons from the Opinaca metasediments give ages between 3.3 and 2.7 Ga indicating that they were deposited prior to 2.7 Ga. To the east is the Hublet Group composed of detritic metasediments and some metavolcanic rocks. The Hublet Group is a lateral equivalent of the Rossignol-Laguiche Group to the west. The Joubert Suite to the east is dated at 2.7 Ga. The Gamart suite, composed of monzogranite, is dated at 2.647 Ga. The Lataignant Suite is composed of megaporphyric granite and dated at 2.645-2.638 Ga. The Opinaca/Ashuanipi contact is constrained by the Nichicun Fault, presenting a mylonite zone that reveals a southward vergence of Ashuanipi. The LaGrande/Opinaca contact is marked by the Dalmas Fault. The Duhesme Group is located near this contact and consists of tholeiitic and calc-alkaline volcanic rocks and polygenic conglomerates deposited during a period of extension on the sides of a volcanic arc that was formed around 2.735 Ga. They are thought to represent the base of the Opinaca now interpreted like a large sedimentary basin deposited in a rift environment. (Caderon, 2000).