CH9 Exploration for Gold – Epithermal – Toodoggone Area, British Columbia

In the Toodoggone River area, Early-Middle Jurassic quartz-bearing dacite-latite flows and pyroclastic rocks host broad argillic zones (adularia-sericite dominant) and quartz veins containing gold and silver concentrations1. To support ongoing provincial geoscience programs2 and active exploration in the Toodoggone area, BC, helicopterborne gamma ray/magnetic surveys were completed in 20073. Results were better than expected. Potassium alteration associated with mineralized (Au-Ag and Cu- Au) epithermal and related underlying porphyry systems in the Toodogone area produce strong airborne high-K and low eTh/K anomalies.  Areas with low K, low U and low Th define carbonate-hosted, intrusion-related skarn deposits. In combination with the magnetic data these features can be used to detect, and distinguish between, the three different deposit types (epithermal Au-Ag, porphyry Cu-Au, skarns).  Portions of the K and eTh/K maps are shown below. GamX CH9 Toodoggone K Maps





Potassium (right) shows known epithermal-style prospects have high-K airborne signatures. In contrast, Castle skarn occurs within low-K responses. These patterns apply throughout the survey over many occurrences (right), including the past-producing Kemess South copper-gold porphyry deposit, which produced ~3 million ounces Au and ~800 million pounds Cu.

GamX CH9 Toodoggone eTh-K Maps













eTh/K ratio (right) significantly reduces effects of topography (geometry, aircraft terrain clearance) and geology (unrelated to alteration), by normalizing potassium to thorium concentrations. Thus increased K related to alteration within the epithermal systems in the area, appear as lows. More than 100 “epithermal-type” showings listed in BC Minfile within the survey area displayed this response.







These results were used to locate and delineate new areas of alteration. Obviously, not all alteration contains economic mineralization, but the vectoring provided by the airborne patterns greatly reduces the search area, especially in combination with magnetic and geochemical information4.  Ground spectrometry conducted within these targeted areas provides in-situ assay information in real-time which are combined with geology specific observations to generate exploration targets. The ground data supports reduced geochemical sampling costs through better sampling focus, placement of overburden or bedrock trenches, and commonly, drill targets.





1. Diakow, L.J., Panteleyev, A. and Schroeter, T.G. (1993): Geology of the Early Jurassic Toodoggone Formation and Gold-Silver Deposits in the Toodoggone River Map Area, BC Ministry of Energy, Mines and Petroleum Resources, Geoscience Map 2001-1, 1:50 000 scale


2. Diakow, L. J. (2006): Geology between the Finlay River and Chukachida Lake, Central Toodoggone River Map Area, North-central British Columbia (Parts of NTS 94E/2, 6, 7, 10 and 11); B.C. Ministry of Energy, Mines and Petroleum Resources, Open File Map 2006-4, 1:50 000 scale


3. Shives, R.B.K., Carson, J.M., Dumont, R., Ford, K.L., Holman, P.B. and Diakow, L. (2004): Airborne multisensor geophysical survey, Toodoggone River Area, British Columbia (Parts of NTS 94D/15, E/2, 3, 5, 7, 10, 11): Geological Survey of Canada, Open File 4613, 1 CD-ROM


4. Shives, R.B.K., Buckle, J., Carson, J.M., Thomas, M., Anderson, R.G. and Schiarizza, P. (2007). New airborne gamma ray spectrometric and magnetic surveys in the Bonaparte Lake area (NTS 92P): New models, targets, discoveries. GSC Poster.