www.arctic-geophysics.com - Geophysical prospecting for Placer Mining

By: Arctic Geophysics  09-12-2011
Keywords: Mining, Geophysics, magnetics

Placer Exploration with Geophysics

2D Resistivity
  1. Bedrock depth and topography: channels, reefs, terraces
  2. Sedimentary stratification: muck, gravel types, sand, silt, clay
  3. Permafrost and groundwater table
  4. Mining history: former pits, settling ponds, technogenic gravels

2D Resistivity is providing a model of the electrical resistivity of the different ground materials/zones. Because Resistivity is not a time domain method and measures a material property, the profiles can usually be well interpreted even in ground with disturbing influences such as discontinuous permafrost, large boulders, or clay etc. In 95% of our Resistivity profiles which have been proven by drilling, trenching or mining, the bedrock depth interpreted by our team has been confirmed.


Magnetics
Combination: Resitivity + Magnetics

In unknown areas it might be advisable to first use 2D Resistivity to detect potentially placer bearing features such as paleochannels, channel systems, and clay layers ("false bedrock"). Then it can be checked, if those features produce increased magnetic data. If this is the case, the placers can effectively be mapped with Magnetics along the valley. After this, the magnetogram indicating the possible course of gold placers can selectively be investigated with 2D Resistivity to reveal the depth of the placer deposits.

In areas where bedrock or "false bedrock" is known to be shallow and associated with magnetite, it makes sense to try Magnetics as primary geophysical method for finding gold placers.

Integrated Placer Prospecting
  1. Geophysical field measurements
  2. In-depth geological investigation
  3. Geochemical results
  4. Technological data (drilling, trenching, mining)
  5. Literary information
  6. Historical sources
  7. Etc.

Keywords: Geophysics, magnetics, Mining