Abstract

The structure of the Flin Flon area (Manitoba and Saskatchewan) has been examined through mapping of mesoscopic and macroscopic structures in both the ca. 1900 Ma Flin Flon arc assemblage volcanic basement and the unconformably overlying (or fault juxtaposed) ca. 1845 Ma Missi Group continental sedimentary cover sequence. The Flin Flon and Callinan volcanogenic massive sulphide orebodies occur within the basalt-dominated basement. The contact between the basement and the cover rocks was investigated in detail during this study. The cover sequence records three principal fold- and foliation-forming events. All deformation observed within the cover sequence is correlative with deformation observed within the volcanic basement. Significant low-angle overlap of basement on cover is attributed to development of a D1 north-verging nappe and subsequent thrust displacement on the overturned basement–cover contact. North-verging D1 structures provide evidence for a distinct post-Missi Group deformation event that preceded regional, southwestward D2 thrusting at peak metamorphic conditions across the southeastern Trans-Hudson Orogen. D2 deformation produced closed to tight, west-verging overturned folds with a well-developed axial planar cleavage and a pervasive extension lineation. D3 deformation generated open folds of the S2 and a weakly to moderately developed spaced axial planar S3 cleavage. D3 and D4 deformations produced sinistral-oblique, brittle–ductile reverse faults that offset all older features.

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