Abstract

The distribution patterns of four types of garnet in surficial materials of southeastern Gaspé Peninsula are interpreted in terms of the glacial history of the area, the lithostratigraphy of the bedrock, and mineral occurrences. Each type is derived from a distinct source, and all have undergone at least some southeastward glacial dispersion. Type 1 garnets, anhedral Ca-garnet fragments, are from the McGerrigle granite metamorphic aureole and were brought into the region by the same ice flow that caused the well-documented southward dispersal of granite debris. Their distribution within the study area depicts the southern part of this important dispersal train with an improved degree of precision. Type 2 garnets, Ca-garnet crystals, seem to be related to skarns within the boundaries of the study area; some patterns cannot be linked to any known source, thus providing challenging exploration opportunities. Type 3 garnets, colored pyralspite garnet crystals, are related to a tectonic breccia within the Maquereau–Mictaw contact zone. Type 4 garnets, Grenville-type anhedral garnets, were not brought into the region by Laurentide ice, as one might suspect, but rather seem to be related to specific horizons within the Silurian Lower Chaleurs Group. On the basis of a palinspastic reconstruction of southern Gaspé Peninsula and a plate tectonic model for the Paleozoic of eastern North America, we propose that these garnets were derived from the erosion of a metamorphic Grenvillian terrane, which presently forms the Northwestern Highlands Zone of Cape Breton Island. The distribution data for this garnet type also lends support to the concept put forth in a previous study whereby a local Late Wisconsinan ice mass penetrated some 5–6 km into the region from the southeast near Saint-Godefroi.

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