27A: alteration bleached, no significant Zn mineralization or Pyrite-content, resistivity larger than 40 ohm.mB: brecciation, matrix Pyrite rich ( 5 – 10 % Pyrite), less than 1% Zn content, resistivity between 15 and 40 ohm.mC: strong brecciation, often more than 5% Zn content, resistivity less than 15 ohm.m.
28Inverse Modeling Strategy VRP pseudo section as starting modelSharp inversion of only VRP data (Initial model is the main constraint)Build a model from the two sharp inversion modelsFix the near borehole properties and let the tomography inversion work on the resistivity in the central region. The resistivity values can be fixed, semi-fixed (fixed in a narrow range) or completely floatingFine tuning the inversion model with different geological / petrophysical constraints
29ConclusionsDetect conductive zones within 30 m range around the boreholeProvide independent estimate of bulk ( m) resistivity datafor calibration / interpretation of other EM datasetsMap conductive zones between the boreholes 180 m apartWorks for all conductivity contrastsVery easy field operation procedures
30Outlook Field test 3D tomography methodologies Develop IP data interpretationMove towards simultaneous data acquisition in multiple boreholesBuild cables to deploy in deeper boreholes
31Acknowledgement Nash Creek, Slam Exploration Sudbury, Camiro, NSERC, CVRD, Xstrata, First Nickel