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Pseudotachylyte at teh base of the Perry Sound Allochthone
Fresh rock cuts created recently during selective upgrading of Highway 522 in Golden Valley village and its vicinity facilitate the detailed study of Grenvillian structures. In western outskirts of Golden Valley village, pseudotachylite veins and breccias are discernible on clean outcrop surfaces of highly strained granodiorite-tonalite gneiss marking the basal contact of the Parry Sound allochthon (Davidson et al., 1982; Culshaw et al., 1997; Wodicka et al., 2000). As at various localities along the Georgian Bay shore, eastern Lake Huron (Tony Davidson and Rebecca Jamieson, written communications), the presence of pseudotachylite veins and breccias attests to seismic failure and friction melting near the basal contact of the Parry Sound allochthon, at middle to shallow crustal levels

Davidson, A., Culshaw, N.G., Nadeau, L., 1982. A tectono-metamorphic framework for part of the Grenville Province, Ontario. Geological Survey of Canada Paper 82-1A, 275 – 290.
Culshaw, N.G., Jamieson, R.A., Ketchum, J.W.F., Wodicka, N., Corrigan, D., Reynolds, P.H., 1997. Transect across the southwestern Grenville Orogen, Georgian Bay, Ontario: polystage convergence and extension in the lower orogenic crust. Tectonics 16, 966 – 982.
JSG Photograph of the Month

Wodicka, N., Ketchum, J.W.F., Jamieson, R.A., 2000. Grenvillian metamorphism of
monocyclic rocks, Georgian Bay, Ontario, Canada: implications for convergence
history. Canadian Mineralogist 38, 471 – 510. PhotoID161

Pseudotachylyte at teh base of the Perry Sound Allochthone
Fresh rock cuts created recently during selective upgrading of Highway 522 in Golden Valley village and its vicinity facilitate the detailed study of Grenvillian structures. In western outskirts of Golden Valley village, pseudotachylite veins and breccias are discernible on clean outcrop surfaces of highly strained granodiorite-tonalite gneiss marking the basal contact of the Parry Sound allochthon (Davidson et al., 1982; Culshaw et al., 1997; Wodicka et al., 2000). As at various localities along the Georgian Bay shore, eastern Lake Huron (Tony Davidson and Rebecca Jamieson, written communications), the presence of pseudotachylite veins and breccias attests to seismic failure and friction melting near the basal contact of the Parry Sound allochthon, at middle to shallow crustal levels

Davidson, A., Culshaw, N.G., Nadeau, L., 1982. A tectono-metamorphic framework for part of the Grenville Province, Ontario. Geological Survey of Canada Paper 82-1A, 275 – 290.
Culshaw, N.G., Jamieson, R.A., Ketchum, J.W.F., Wodicka, N., Corrigan, D., Reynolds, P.H., 1997. Transect across the southwestern Grenville Orogen, Georgian Bay, Ontario: polystage convergence and extension in the lower orogenic crust. Tectonics 16, 966 – 982.
JSG Photograph of the Month

Wodicka, N., Ketchum, J.W.F., Jamieson, R.A., 2000. Grenvillian metamorphism of
monocyclic rocks, Georgian Bay, Ontario, Canada: implications for convergence
history. Canadian Mineralogist 38, 471 – 510. PhotoID161

Photograph: Fried Schwerdtner