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TitleIntegrating ice-flow history, geochronology, geology, and geophysics to trace mineralized glacial erratics to their bedrock source: an example from south-central British Columbia
AuthorPlouffe, A; Anderson, R G; Gruenwald, W; Davis, W J; Bednarski, J M; Paulen, R C
SourceNew insights in Cordilleran Intermontane geoscience: reducing exploration risk in the mountain pine beetle-affected area, British Columbia; by Haggart, J W (ed.); Canadian Journal of Earth Sciences vol. 48, no. 6, 2011 p. 1113-1129, (Open Access)
Alt SeriesEarth Sciences Sector, Contribution Series 20100079
PublisherCanadian Science Publishing
Mediapaper; on-line; digital
File formatpdf
ProvinceBritish Columbia
AreaBonaparte Lake; Little Fort
Lat/Long WENS-122.0000 -120.0000 52.0000 51.0000
Subjectssurficial geology/geomorphology; geochronology; ice flow; ice movement directions; ice movement; ice retreat; ice transport directions; erratics; erratics trains; dispersal patterns; boulders; tills; gold; mineralization; Thuya Batholith; Cenozoic; Quaternary; Mesozoic; Jurassic
Illustrationssketch maps; photographs
ProgramMountain Pine Beetle, Geoscience for Mountain Pine Beetle Response
AbstractThis study demonstrates how ice-flow history, geochronology, geology, and geophysics may be integrated to enhance the effectiveness of boulder tracing in glaciated regions affected by multiple ice-flow events. Mineralized felsic granitoid boulders (erratics) were discovered 18 years ago on a claim block located 10 km northwest of Little Fort, in the Bonaparte Lake map area (NTS 092P), in south-central British Columbia. Although the boulders have yielded significant gold concentrations (up to 4.15 g/t), their bedrock source is not known. The till near the boulders contains up to 1382 gold grains per 15 kg of bulk material with 75% of the grains having pristine morphology, suggesting a short distance of glacial transport. A U--Pb zircon crystallization age of 198.1 ± 0.5 Ma on one mineralized boulder indicates derivation from an Early Jurassic intrusion. Using a vector addition model based on regional ice-flow patterns, the most recent and detailed bedrock geology map, and recently acquired airborne radiometrics and magnetic data, the northeast sector of the Thuya Batholith (195--205 Ma) is interpreted as the most likely bedrock source of the mineralized boulders.