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TitleACE mineral property, B.C. - Soil and till geochemistry (NTS 093A014E)
AuthorLett, R E; Paulen, R CORCID logo
SourceBritish Columbia Geological Survey Geological Fieldwork Paper 2020-01, 2020 p. 145-165
LinksOnline - En ligne
Alt SeriesNatural Resources Canada, Contribution Series 20200534
PublisherGeological Survey of British Columbia
File formatpdf
ProvinceBritish Columbia
Lat/Long WENS-122.0000 -120.0000 53.0000 52.0000
Subjectsgeochemistry; Science and Technology; geochemical surveys; soil geochemistry; soil surveys; till geochemistry; sulphides; sulphide deposits; quartz veins; drift prospecting
Illustrationslocation maps; tables; plots
Released2021 01 09
AbstractA multi-media surficial geochemical survey was carried out by the British Columbia Geological Survey in 2000 to document the geochemical expression of massive sulphide and gold-quartz vein mineralization at the Ace mineral property, near Likely. Much of the bedrock on the property is concealed by lodgement (basal) till, which was deposited by a southeast to northwest ice advance, ablation till, and colluvium. Soil samples from the B-horizon soil and transitional B-C horizon, and lodgement till were collected from 85 sites and the <0.063 mm (-230 mesh fraction) was analyzed for more than 50 minor and trace elements and major oxides by three methods: modified aqua regia dissolution-inductively coupled plasma mass spectrometry; instrumental neutron activation; and lithium metaborate fusion-inductively coupled plasma emission spectroscopy. Samples were also analyzed for carbon, sulphur, and loss on ignition. Five size fractions ranging from 1-2 mm to 0.125-0.063 mm of selected till and soil samples were analyzed for 35 trace elements by modified aqua regia dissolution followed by ICP-MS. The commodity and pathfinder metals Au, As, Bi, Co, Cu, Pb, Se, and Zn are present in higher concentrations in the <0.063 mm fraction of the basal till than in the B-horizon soil, likely because the metal content in the silt- and clay-sized fraction of till more closely reflects the chemistry of bedrock after comminution and dispersal. However, Ag and Hg have higher concentrations in the B-horizon soil where they were likely captured and concentrated by organic matter during soil formation. Till and soil size fraction analysis for metals show that Au and Pb are present in soil and till as discrete mineral grains larger than 0.063 mm. Anomalous Co, Cu, Pb, Se, and Zn concentrations in till and soil define a ribbon-shaped dispersal train along the northern edge of the survey area. The train formed from glacial erosion of mineralized bedrock, that was then transported and deposited by an east to west ice flow. This train was then subjected to post-glacial modification by colluvial processes. The trace element dispersal profiles suggest a massive sulphide source for the anomalous metals in bedrock beneath the till at the east end of the dispersal train. Potentially, other till and soil Au and As anomalies in the western and southern parts of the survey area could have been derived from unmapped, northeast-trending Au-quartz veins.
Summary(Plain Language Summary, not published)
This is publication of a legacy dataset that the 2nd author (Paulen) worked on while employed with the British Columbia Geological Survey in 2000. This paper examines a paired set of data from till and soil samples over a dispersal train in central British Columbia, east of Quesnel. Selected pathfinder elements (relevant to mineral exploration) are discussed in this paper. The important part of this paper is to demonstrate the greater signal-to-noise ratio that can be detected by sampling till, and not just the soil. Soil sampling was a historical methodology used in exploration in the Cordillera.

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