STRUCTURAL CORRELATION WITHIN THE KAPUSKASING UPLIFT

Comparison of progressive deformation and metamorphic history within a nd between the tectonic domains of the Kapuskasing uplift indicates si gnificant variation in age and style of deformation across this large segment of the central Superior Province; multiple stages of tonalite and granitoid intrusion, melt generation, polyphase diachronous deform ation, and likely rapid deep burial of supracrustal rocks collectively produced the complex character of this example of Archean mid to deep crust. At least four Archean deformation phases are recognized, altho ugh not all are of regional extent. Dated structural chronology sugges ts that the locus of the earliest recorded deformations migrated to de eper crustal levels with time. Pre-2680 Ma deformation (local D-1-D-2) within high-level tonalites is correlated with deformation in the Mic hipicoten supracrustal belt. The apparent earliest deformational fabri cs at deeper crustal levels in the granulite terrane of the Kapuskasin g structural zone occurred between 2660 and 2640 Ma. Archean third and fourth phase deformation phases (similar to 2667 to similar to 2629 M a) are present at mid-crustal and deeper levels and deform post-2667 M a metaconglomerate; these resulted in large-scale folding and subhoriz ontal ductile shear zones, which seem to represent an important transi tional zone that separated a passive upper crust from continued ductil e strain at deeper levels. Subsequent uplift of the high-grade rocks w as accomplished in multiple stages, initiated prior to 2.45 Ga and lik ely culminated around 1.9 Ga, although continued movement occurred as late as 1.14 Ga. The Ivanhoe Lake fault zone, along which much of the uplift must have occurred, exhibits some evidence of ductile deep-thru st-related fabrics, but most of the observed structures are brittle to brittle - ductile and steeply inclined. A broad zone of pervasive cat aclasis and brittle - ductile shear zones is a characteristic feature of the fault zone throughout its length, and both dextral and sinistra l offset are locally present. Clear ground evidence for major transcur rent or thrust displacements, however, has not been recognized.