Geology and Mineral Occurrences of the Aphebian Waugh Lake Group, Northeastern Alberta

An area underlain by the Waugh lake group in Northeastern Alberta was mapped on a scale of 1:10,000. Sedimentary and volcanogenic features are preserved in parts of the succession and consequently in the Waugh Lake Group could be divided into sedimentary and volcanic units, which will help in better understanding the tectono-stratigraphic history of the package of rocks, as well as the origin of the mineral occurrences in the area. An unconformity at the base of the Waugh Lake Group has not been found and consequently its basement is unknown.

Volcanic rocks are mainly exposed in the central part of the area and include both mafic and felsic components. Massive flows can be distinguished from thinly laminated tuffs, Units with mafic an felsic fragments are interpreted as explosive rhyolitic pyroclastic flows and thick units with smaller fragments (previously larger mapped as phyllonites) are interpreted as accumulations of lapilli tuffs. A related more mafic unit shows structures that resemble trough cross-bedding, indicating that they might be water reworked lapilli tuffs.

Sedimentary rhymites of graded sandstone, siltstone and mudstone are mainly exposed on the east side of the Waugh Lake area, but can also be recognized on the west side. They are associated with an extensive matrix supported conglomerate which could correspond to debris flows. Near the conglomerates, minor volcanic extrusions are present.

After the Waugh Lake Group deposition, large stocks of granite to diorite and associated pegmatites intruded the sequence. Deformation is expressed by extensive folding and mylonization and resulted in a large scale synformal structure of the Waugh Lake Group. Deformation is associated with greenschist facies metamorphism. Late phase shearing with a steep stretching lineation has left a strong imprint on all rock formations on the Waugh Lake Group. A final event is indicated by the post orogenic intrusion of the Andrew Lake porphyritic granite.

Gold mineralized zones, which are hosted in gossaneous metasediments (rhythmites), occurring near the East shores of Waugh Lake, extends as far north as Doze Lake. Additional mineralized zones are mainly of the quartz-tourmaline type with gold and tungsten associated. Although no significant base metal mineralization was discovered in the Waugh lake area, the presence of bimodal volcanism associated with a succession of fine grained sediments indicates the possible presence of massive sulfide deposits.