Superimposed Deformations in the Missi Meta-sedimentary Rocks near Flin Flon, Manitoba

Abstract

Within the Flin Flon Basin, Precambrian meta-sandstones and conglomerates belonging to the Missi Group have been complexly deformed as a result of three periods of deformation. The first two periods (P1 and P2) involved folding but no apparent faulting, the last (P3) involved both folding and faulting. Progressive metamorphism (M2), within the greenschist facies, occurred during the second phase (P2) and aided in the formation of a pronounced axial-plane foliation (S2). Small-scale folding and retrograde metamorphism (M3) occurred along faults formed during the last phase (P3).The faults in this area all appear to be high angle, oblique-slip reverse faults and can be interpreted as having formed during a single orogenic event (P3) although there is sequence in their initiation. The net-slip directions of different faults are approximately the same, and plunge moderately to the southeast, with either the east or south side upthrown, depending on the attitude of the fault.

Structural relations between the polydeformed Flin Flon arc assemblage and Missi Group sedimentary rocks, Flin Flon area, Manitoba and Saskatchewan

“…The authors correlated the fold generations established by Stauffer and Mukherjee (1971) with those observed in the older volcanic rocks of the Flin mon arc assemblage.…”

“…Stockwell (1960) identified numerous macroscopic fold and fault structures but did not discuss the deformationa1 sequence in detail. Stauffer and Mukherjee (1971) presented a detailed summary of the structural history witliin the Missi Group at Flh Flon. By examining the relationship between the pewasive fabric and numerous macroscopic folds, they identified three deformation events.…”

“…2 Ambrose (1936a) and developed further by Stauffer and Mukherjee (1971) and Stauffer (1990). At Flin Flon, Missi Group conglomerates and sandstones were deposited at Ca.…”

“…Table 1 presents four structural models (Stauffer and Mukherjee, 1971;Baiies and Syme, 1989;Thomas, 1992Thomas, , 1994Fedorowich et al, 1995) and compares them with the deformation sequence from this Bailes and Syme, 1989 (1989) identified an early generation of folds which they interpreted to predate deposition of the Missi Group. They describe the Burley Lake syncline (Stockwell, 1960), located in the southwestern corner of the field area, as a fold which is tmncated at the unconformity (Figure 2.5).…”

“…In another area, the contact is a thmst fault, with volcanic rocks situated structurally above the sedimentary rocks. Previous studies ( Stauffer and Mukherjee, 1971;Bailes and Syme, 1989;Thomas, 1992Thomas, , 1994 have not focused on the basement-cover contact, and particularly, its dual role as both an unconformity md a thmst fault. Previous structural research (Stauffer and Stockwell, 1960;Bailes and Syme, 1989;Syme et al, 1993;Thomas, 1992Thomas, , 1994.…”