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TitleAn integrated approach to boulder tracing: an example from south central British Columbia
AuthorPlouffe, AORCID logo; Anderson, R G; Gruenwald, W; Davis, W JORCID logo; Bednarski, J M; Paulen, R CORCID logo
SourceJoint annual meeting of the Canadian Quaternary Association and the Canadian Chapter of the International Association of Hydrogeologists, abstracts volume; 2011, 1 pages
LinksOnline - En ligne (Full program/Programme complet, PDF 150 MB)
Alt SeriesEarth Sciences Sector, Contribution Series 20100338
MeetingGeoHydro 2011, joint annual meeting of the Canadian Quaternary Association and the Canadian Chapter of the International Association of Hydrogeologists; Québec city; CA; August 28-31, 2011
ProvinceBritish Columbia
AreaLittle Fort; Bonaparte Lake
Lat/Long WENS-122.0000 -120.0000 52.0000 51.0000
Subjectssurficial geology/geomorphology; economic geology; ice movement; ice flow; ice movement directions; ice transport directions; dispersal patterns; erratics; boulders; tills; gold; mineralization; Cenozoic; Quaternary
ProgramMountain Pine Beetle, Geoscience for Mountain Pine Beetle Response
AbstractIce-flow history, geochronology, geology, and geophysics is integrated to enhance the effectiveness of boulder tracing in glaciated regions affected by multiple ice-flow events. Mineralized felsic granitic 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), south central British Columbia. Although the boulders have yielded significant gold concentrations (up to 4.15 g/tonne), their bedrock source remained unknown. 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. The boulders might have been transported by two dominant ice-flow movements: a first movement to the west derived from the Cariboo Mountains and a second movement generally to the south when an ice-divide formed around the 52nd parallel in south central British Columbia. 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. This corresponds to glacial transport of the boulders of less than one but probably not more than five kilometres.

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