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Volcanic hosted epithermal gold: NEVADA
Paradise Peak, Ketchup Flat deposits, 3D E-SCAN mapping, 1989
A post-discovery test case for 3D E-SCAN

The Paradise Peak orebody discovery was the result of a prospecting program that used old mercury operations as focal points. Evidence of the mineralization outcropped,- no geophysics was needed or used.

Following discovery, FMC Gold Company tried various state-of-art geophysical techniques, both ground and airborne, in attempts to obtain a geophysical signature for the orebody. The hope was to establish a viable geophysical method for exploring adjacent covered ground, in search of additional silver-gold mineralization.

Despite having a large volume orebody lying virtually at surface, no geophysical techniques were successful in "seeing" the orebody. Geophysics was abandoned, and exploration of the surrounding area proceeded by the only available option, - stepout drilling.

Five years of continuous exploration drilling brought results: the Ketchup Flat orebody, hidden from view all that time by just a couple of metres of cover. At about the time that the Ketchup Flat orebody was being stripped for mining, FMC heard about E-SCAN, and brought it in for a test that included the operating Paradise Peak deposit site, and the new Ketchup Flat discovery. Premier Geophysics applied E-SCAN on a 300 foot square grid spacing to generate one of the first true 3D DC resistivity field data sets ever acquired in Nevada. These field data were processed some time later with the first DC resistivity 3D inversion program, developed with FMC's co-operation at the University of British Columbia.

This is what was seen as a result of the 3-week field survey, followed by 3D inversion processing:

               plan views, at absolute elevations      | |      plan views, draped on topo      | |      section views facing Southeast      | |      section views facing Northeast

Additional controls are embedded in the displays - you can speed through by clicking on either the left or right third. For pause and resume, click anywhere in the middle.

The 3D E-SCAN survey was wired right through the operating mine, at the stage of mining shown here, in order to ensure accurate capture of the orebody's 3D signature.
These results are deliberately not contoured, in order to show the unedited values of the 3D inversion model cells, exactly as delivered by the inversion algorithm.

Contouring can reveal subtleties that are not able to be seen with just 18 or so color bar levels, but contouring (and prerequisite data gridding) introduces subjective elements to the data. Sometimes, like here, we want to view the data first in their primary, least-processed form.

FYI - the data views were generated in 1997 from a very crude 3D inversion run... today we would see four times the grid element density in every plan and section view.