Synchronous vertical and horizontal tectonism during the late stage of Archean cratonization: An important process in gold mineralization?

Abstract

Both vertical and horizontal tectonism played an impor- tant role in Archean tectonic evolution. These two processes have independent driving forces and should not be mutually exclusive. In the Superior Province in Canada, there is convincing evidence for synchronous vertical and horizontal tectonism at the late stages of Archean cratonization, and horizontal shearing (a result of hori- zontal tectonism) is concentrated in synclinal keels (a result of ver- tical tectonism). The Timiskaming-type sedimentary rocks were de- posited in the keels during this process. The synclinal keel-shear zone association provided a link between the upper crust and the lower crust or mantle, and might have served as a conduit for min- eralizing fluids and magma that were generated in the crust and/ or mantle during the process. Such a process in the late stage of Archean cratonization can readily explain the common association of gold deposits with greenstone belts in synclinal keels, shear zones, late felsic to intermediate intrusions and Timiskaming-type sedi- mentary rocks.