Structured analyses at strained lithotectonic boundaries in ancient orogens

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The Canadian Shield includes ancient orogens (deeply-eroded mountain belts) replete with economic mineral deposits. In most orogens, sheared contacts between large rock masses, also called lithotectonic boundaries (LTBs), have attracted much interest by research geoscientists and economic geologists. The interest stems mainly from the fact that LTB walls contain important geological information, and are a preferred locus of gold-bearing veins and other kinds of ore deposits. LTB walls have therefore been studied to gain a better understanding of ore-emplacement processes and geological deformations such as LTB-parallel (tangential), ductile shear. Information about the wall-rock shear may also furnish valuable clues as to the displacement between structurally separated parts of ore deposits, and provide new insight into the nature of ductile deformation at deep-crustal levels in ancient orogens. Together with research students and a British colleague, I developed more powerful techniques for investigating the tangential ductile shear of well-exposed LTB-wall segments. We propose to refine the techniques in 2006-2010, and demonstrate, in detailed case studies, that the conventional methods of tangential-shear analysis may give erroneous results. The case studies require independent knowledge of LTB-dip angles, and will therefore be sited in shield areas with high topographic relief. Research students will participate in all case studies, designed to contribute to the training of highly qualified personnel.