Overview of Results from the Greenstone ... - Geology Ontario

In Timmins, the first generation of folding and faulting with an associated fabric is a series of
stacked, south-over-north D2 thrust faults with hanging wall folds, located north of the PDDZ (Bateman
et al. 2005). The D2 event is post-Porcupine assemblage in timing (i.e., 2676 Ma), because the Timiskaming
unconformity truncates the D2 folds and thrust faults. Early ductile deformation, which is interpreted to
be synchronous with D2, is evident as C-S structures in the PDDZ indicating south-over-north thrusting
along a south-dipping zone, which was probably the root zone to the stacked thrusts to the north (Bateman
et al. 2005). A post-Porcupine age for early thrusting coincides with the age data from the Duparquet
Basin associated with the PDDZ in Quebec (Mueller et al. 1996).
Younger syntectonic intrusions (2680–2670 Ma) are small stocks, dikes and sills that are coeval with
the Timiskaming assemblage and are spatially associated with the PDDZ and LLCDZ. Broadly
synchronous with this magmatic event, syntectonic opening of the Timiskaming half-graben in a
dilatational jog, was followed by foliation and folding, only the late stages of which affected the
sediments. S3 foliation is strongly developed in Tisdale, Porcupine and Timiskaming assemblage rocks
proximal to the PDDZ in the Timmins area, and is axial planar to a series of en échelon folds with curved
axial surfaces along the PDDZ. The F3 fold axes do not affect the trace of the PDDZ, and do not extend
directly across it to its southern side. These facts are interpreted to indicate development of F3 during leftlateral
strike-slip movement along the PDDZ (Bleeker 1995). The magnitude of this sinistral displacement
appears to be about 13 km as indicated by the offset of both the Krist formation and the F2 Porcupine
syncline in Tisdale Township, eastward into Whitney and Cody townships. Here, the Krist formation
underlies the Porcupine assemblage sediments on the western limb of an F2 syncline within the Whitney
formation (see Figure 2). Therefore, it is hypothesized that both the Krist and Beatty formations and the
F2 Porcupine syncline have been offset across the PDDZ during D3. This D3 event in Timmins may be
correlative with early folding observed in Timiskaming assemblage wackes in Gauthier Township where
it has been designated as pre-D2 (see “Kirkland Lake–Larder Lake Subproject”).
The late tectonic intrusions (2670–2660 Ma) are minor, high crustal level intrusions which occur
both within the external batholiths and the supracrustal belt. Possibly synchronous with this magmatic
event, D4 folding created a syncline within the Timiskaming assemblage rocks in the Timmins area. Here,
S4 foliation crenulates S3 and is axial planar to F4 folds that commonly have Z asymmetry. Minor
structures suggest right lateral strike-slip along the PDDZ. The last significant event, D5, consists of an
intense constrictional strain seen in Tisdale assemblage pillows, clasts in Krist formation volcaniclastic
rocks and cobbles in Timiskaming assemblage conglomerates. The D4–D5 event represents the final stage
in transpressional deformation along the PDDZ. This structural event may be correlative with the D2
event identified in the Kirkland Lake–Larder Lake area in which S2 overprints Timiskaming assemblage
volcanic rocks with an age of 2670 Ma and is most strongly developed in proximity to the LLCDZ.
Kinematic indicators in Gauthier Township suggest a reverse-dextral sense of movement along the
LLCDZ during D2.
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