Structural variation of proterozoic dikes in central Superior Province: A possible reflection of post-Archean shield deformation

Preliminary work is reported on the use of two structural parameters, dike dip and thickness, as possible depth-of-exposure indicators in the Central Superior Province. The data demonstrate systematic variations in the dip and thickness of 2.6 and 1.14 Ga. dikes across the Central Superior Province and are tentatively interpreted to result from post intrusion deformation. Combination of these results with additional structural and paleomagnetic data from dikes of all gas may permit detailed mapping both spatially and temporally of crustal deformation in this part of the Canadian Shield. Although dike dip and thickness data apparently reflect crustal exposure level as given by host rock metamorphic grade (ranging from subgreenschist to granulite), these post-orogenic dikes themselves are at most only weakly metamorphosed. This requires that regional isotherms dropped dramatically after the Kenoran orogeny (2.65 Ga.) and prior to emplacement of the earlist post-orogenic swarm (Matachewan-Hearst) at 2.6 Ga.