A case study of soil gases as an exploration guide in glaciated terrain: Crandon massive sulfide deposit, Wisconsin

The Crandon massive sulfide deposit is covered by as much as 65 m of glacial drift. Soil gas was sampled at a depth of 0.5 m along several traverses over the deposit. Gases showing anomalies that correlate with the underlying deposit include CO ₂ , CH ₄ , and O ₂ . CO ₂ and CH ₄ show positive anomalies with a background/anomaly ratio as high as 1 to 25, whereas O ₂ shows negative anomalies. Oxidation of the sulfides with the production of sulfate is the probable chemical reaction producing some of the gas anomalies. The CH ₄ anomalies may result from thermal cracking of hydrocarbon precursors. These results indicate that measurement of soil gases should provide a useful exploration tool in glacial terrain.