|Abstract||The Bonaparte Lake map area lies within the Interior Plateau of south central British Columbia and is within the zone severely impacted by mountain pine beetle infestation. To diversify the severely
impacted natural resource economy of this region, a regional till sampling and surficial geology mapping project has been implemented by the Geological Survey of Canada as part of the Mountain Pine Beetle Program of Natural Resources Canada. The
objective of this activity is to evaluate the mineral potential of the area which is characterized by a nearly continuous and thick cover of glacial sediments. It has been demonstrated within the Cordillera that evaluating till composition can be an
effective tool for mineral exploration, especially when used in combination with modern bedrock geology, geophysics and national geochemical reconnaissance (NGR) data sets (lake and stream sediments geochemistry).|
During the 2007 and 2008 field
seasons, till sampling was completed in the following map areas: 92P/1 west half, 2, 3, 6, 7, 8 west half, 9, 10, 14, 15 and 16 (outside Wells Gray Provincial Park boundaries). Till sampling was completed in the eastern halves of 92P/1 and 92P/8 by
the British Columbia Geological Survey in the late 1990s. Till samples (2-3 kg) were collected for geochemical analyses at a spacing of 2-3 km along forestry roads. A few glaciofluvial sediment samples were collected where till was unavailable. Large
bulk till samples (15 to 30 kg), for heavy mineral study, were taken on average at every second sample site except in regions of high mineral potential where they were collected at every site.
Geochemical analyses will be conducted on the matrix
portion of the smaller till samples (silt plus clay, and clay-sized fractions) and on the heavy mineral concentrates. The large samples are being processed for heavy mineral separations and identification. Till pebble lithologies will be examined for
evidence of mineralization or alteration and for assessing glacial dispersal distance and direction. In addition to the till sampling, surficial geology maps are being produced to reconstruct the glacial history of the region (Bednarski, in press;
Huscroft, in press; Plouffe, in press-a; in press-b). These will be of great importance for the interpretation of the till composition data
Glacial striations measured on bedrock outcrops during the 2007 and 2008 field seasons record changing
ice-flow directions which provide new insights to the history of the last glaciation. These observations make it possible to refine the glaciation model of central British Columbia originally proposed by Tipper (1971a; 1971b; 1971c) which was largely
based on the interpretation of macro-landforms (e.g. drumlins, flutings, crag-and-tails) observed on aerial photographs. At the onset of glaciation, ice accumulated over the Cariboo Mountains to the northeast of the area and advanced towards the
west and southwest over the Bonaparte Lake map area at least as far west as Loon Lake, Green Lake, and Lac la Hache. As the glaciation intensified, ice accumulated over the Interior Plateau, and a linear east-west trending ice divide developed north
of the Bonaparte Lake map area resulting in general south-eastward, southward, and south-westward ice movements. The net effect of these two phases of ice flow is that glacial transport within the Bonaparte Lake region generally results from two
general vectors: the first one generally to the west and southwest, and a second one to the southeast, south or southwest.
Preliminary results of till compositional studies are currently available. Gold grain counts in heavy mineral concentrates
are elevated in a region west and northwest from Little Fort where several gold occurrences are known. However, some of the samples with high gold grain content are not located close or down-ice from known gold occurrences in bedrock and warrent
further investigation. High thorianite (ThO2) grain counts and elevated percentages of felsic intrusive pebbles in till west of the Thuya Batholith are the result of the first phase of westward ice flow over the region.