Lessons Worth Highlighting¶
Prior to the discovery of the Albany Graphite deposit, the area had been largely unexplored in the past due to thick overburden and Phanerozoic cover rocks overlying the prospective Archean basement rocks. The ability of modern AEM systems to penetrate the cover has played an important role in further exploring the area. Arguably, had it been a nickel sulphide deposit, with a strong magnetic and EM correlation, it might have been discovered sooner. Instead, despite its large size and favourable high conductivity, the Albany Graphite airborne TDEM anomaly is distinguished by a weak magnetic low response that is consistent with diamagnetic graphite. This resulted in a lower ranked geophysical target relative to other neighbouring anomalies. Regardless, the presence of a strong AEM anomaly inside a favourable geologic and geophysical structure resulted in it being drill-targeted for nickel sulphides but which instead led to the discovery of these rare igneous-related, hydrothermal graphite deposits. Ground TDEM follow-up was used to constrain the outline and depth extent of the mineralized ore bodies, as well as in directing the diamond-drilling. The 3D AEM and ground EM inversion resulted in more accurate and useful models of the targeted breccia pipes. This blind discovery in an under-explored region below extensive cover is testament to the importance of well defined geologic target model and the use of deep penetration airborne and ground-based EM systems.