Open File Report 1993-08

Open File Report 1993-08

OFR 1993-08

Evaluation of the Economic Mineral Potential in the Andrew Lake-Charles Lake Area of Northeast Alberta

The Alberta Geological Survey (AGS) assessed 88 mineral occurrences in the Andrew Lake Charles Lake area of northeastern Alberta as part of the Canada-Alberta Partnership Agreement on Mineral Development. These mineral occurrences are related to gold, uranium, base metals, iron and rare earth elements. A complete database has been gathered which contains field observations, analytical results and a compilation of assessment reports archived by the Alberta Geological Survey. Groups of mineral occurrences, which hold significant mineralization are described in detail as mineral showings. The description of these 17 mineral showings provides details of past exploration, local geology and mineralization.

The 1992 investigation demonstrated the gold and base metal potential of the metasedimentary and metavolcanic belts of northeast Alberta. Geochemical analysis of grab samples collected on deeply weathered sulfide horizons in the Potts Lake, Waugh Lake and Pythagoras Lake areas have indicated anomalous values of up to 770 parts per billion (ppb) gold. A deep trench at the north end of Selwyn Lake showed structures and textures similar to volcanogenic massive sulfide deposits. Geochemical analysis of samples from the trench yielded values of 294 parts per million (ppm) copper with some gold. Previous exploration work on the area had reported 0.1% copper. The deeply weathered rock exposures found at the location of other mineral occurrences hosted in the metasedimentary-metavolcanic belts, which contain elevated base metal values, are thought to represent the same geological setting as the one observed at Selwyn Lake.

Quartz-tourmaline veins intruding granite and metasediments (east of Andrew Lake) are the second geological environment shown to be favorable for gold mineralization. Geochemical analysis of grab samples have returned anomalous gold values of up to 147 ppb, in association with elevated arsenic, molybdenum and tungsten values. These results suggest the possibility for Archean lode gold deposits similar to some Abitibi belt gold deposits.

Uranium showings account for nearly half of the showings described in this report. The majority of the uranium mineralization is hosted in pegmatite and related granitoids. Their average grades are sub-economic, and it is unlikely that pegmatite hosted occurrences hold much potential in present day market conditions. However, the uranium showing located at the West Arm of Andrew Lake has molybdenum values of up to 0.15%, associated with 0.25%.uranium. At this showing, Godfrey (1958) reported values of 1.40% molybdenum. Along with numerous molybdenite occurrences in the area, these values confirm the potential for molybdenum deposits in the high grade metamorphic terrains. Some radioactive occurrences are associated with anomalous amounts of thorium and rare earth elements. In the South Potts Lake showing, a sample returned a content of over 1% of the rare earth elements lanthanum, cerium, neodymium and samarium combined.

Two intriguing iron-rich pegmatitic breccias have been discovered in the area. They contain 25 to 29% iron expressed as magnetite and hematite, which form the breccia matrix. Vanadium values up to 381 ppm are associated with the high iron values.

The results obtained from the 1992 AGS investigation indicate that further study of the area is warranted. Other metasedimentary belts in northeast Alberta should receive closer examination in order to complete the mineral inventory. It is recommended that field examination be performed in areas such as the Ashton Lake, Potts Lake, Alexander Lake, Split Lake and Swinnerton Lake metasedimentary belts. Lithogeochemistry on samples stored by the Alberta Geological Survey could be used in conjunction with the field program. Airborne geophysics could also be considered, if funding is available. Geophysics could provide a depth investigation of the metasediment belts and help in the investigation of the numerous shear zones present in the area. These shear zones are considered to have good potential for gold mineralization, but are relatively unexplored.