Mapping and Modeling Geochemical Dispersion Above a Till ......Cv Cv Cv Cv Cv Cv Cz Av GFb Av GFb Tb...

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Mapping and Modeling Geochemical Dispersion Above a Till Concealed Polymetallic VMS Deposit Bodnar, M.M and Winterburn, P.A. IAGS 28 / RFG, Vancouver, 21 June 2018 EGI
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  • Mapping and Modeling Geochemical Dispersion Above a Till Concealed Polymetallic VMS Deposit

    Bodnar, M.M and Winterburn, P.A.IAGS 28 / RFG, Vancouver, 21 June 2018

    EGI

  • Felix Ng

    Content

    • Rationale• Location and Setting• Methodology• Results• Integration and Interpretation• Implications and Recommendations

  • The Reality – the future is under cover

    • ~75% of the glaciated Canadian landscape is covered by quaternary sediments representing a challenge to discovery

    • Enhanced methods in exploration geochemistry, capable of detecting mineral deposits through complex cover, must be developed to satisfy global resource demands.

  • Geochemical Dispersion Mechanisms

    ? ?

  • Concealed Deposit - Lara VMS

    • Polymetallic massive sulphide• Well defined by drilling• Widespread glacial sediment

    cover

    • Minimal anthropogenic disturbance (undeveloped)

    • Heavily forested by mature 2nd growth

  • VMS in the Sicker Group

    Ice Flow Indicators

    Direction known

    Direction unknown

    Blyth and Rutter (1993)

  • Lara VMS - Geology

    Py – Cpy stringer zone

    Andesite

    Rhyolite

    Rhyolite

    Sandstone

    Andesite

    (Co, Se, Bi and Te) (As, Sb, Cd, Se, In, Mo, Hg and Ga)

  • Lara VMS - Geology

    (Photo: Barry Smee)Exposure of Pyrite Stringer Zone Lara Discovery Trench

  • Methodology• Upper B horizon soil (n=150)• Aqua regia digestion, ICP-MS (-180 μm)

    Py-CpyZone

  • Zinc

    B horizon, aqua regia, -180 μm Robust linear regression

  • Copper

    B horizon, aqua regia, -180 μm Robust linear regression

  • Cadmium

    B horizon, aqua regia, -180 μm

  • Residence - Sequential Extraction

    Sequence

    DIWAmmonium

    Acetate

    Cold 0.1M

    HA-HC

    Hot 0.25M

    HA-HC

    Na Pyro-

    phosphateAqua Regia 4-Acid

    Clastic signatureHydromorphic signatureOrganic matter

  • ResidenceSequential Extraction

  • High Zn residual

    B horizon, 2 - 6.3 mm fraction, Kappameter KT-10

    High Zn residual

    (>55 ppm)

    (>38 ppm)

    (>22 ppm)

    (>5.3 ppm)

  • Landscape and Surficial Material IntegrationTb

    Tb

    Tb

    Cv

    Cv

    Cv

    Cv

    Cv

    Cv

    CzAv

    GFb

    Av

    GFb

    Tb

    GFv GFv

    GFb

    Tv

    Tv

    Steep slope

  • Geochemical Dispersion Vectors

    • Establish clastic and hydromorphic geochemical dispersion pathways

    Lara Adit

  • ICE FLOW

  • Summary of Geochemical ResponsesPyrite Horizon Stringer Zone• Thin cover • strong response of Zn, Cu,

    Cd, Mo, Se, Hg, Te• clastic dispersion of bedrock

    Lara VMS • Thick cover• strong response of Zn• clastic dispersion of exotic

    mafic rock, not VMS

    Alluvial Basin • displaced clastic

    signature due to erosion and redisposition of till

    • Zn and Cu response from primary minerals in till

    • More labile elements collect in alluvial basins (Cd, etc.)

    • No evidence of metal migration from VMS

  • Mineral Exploration Strategy

    Surficial material and landscape mapping is strongly recommended to be completed as an integrated component of:

    • Sampling survey design• Geochemical data interpretation• Drill target selection

    When exploring in recently glaciated terrain,

    must ESTABLISH:

    • Pathways of paraglacial and modern erosion / re-deposition

    • Pathways of surface runoff drainage • Characterization of bedrock units using same digestion

    and analysis as soil program

    Acquire Lidar or HR-DEM as EARLY as possible!

    Rhyolite

    Andesite

    Gabbro(altered)

    Gabbro(fresh)

    Till A (early)

    Over Lara

    High Zn Residuals

    Surficial Material

    Over pyrite

    Till D (late)AlluviumColluvium

    Ga (ppm) - aqua regia

    Cr

    (ppm

    ) -

    aqua r

    egia

  • Thank-You

    Chris BennConsulting

    Smee & AssociatesConsulting Ltd.

    Colin DunnConsulting

    Landscape Integration of archived data:B Horizon soil geochemistry completed in1979,Aqua Regia, -180 μ[email protected]

    Contact:

    Mapping and Modeling Geochemical Dispersion Above a Till Concealed Polymetallic VMS Deposit ContentThe Reality – the future is under cover Geochemical Dispersion MechanismsConcealed Deposit - Lara VMSVMS in the Sicker GroupLara VMS - GeologyLara VMS - GeologyMethodologyZincCopperCadmiumResidence - Sequential ExtractionResidence�Sequential ExtractionSlide Number 15Landscape and Surficial Material IntegrationGeochemical Dispersion VectorsSlide Number 18Summary of Geochemical ResponsesMineral Exploration StrategyThank-You