- GeoRef, Copyright 2006, American Geological Institute. Abstract, Copyright, Society of Economic Geologists
A well-exposed area representative of the Archean volcanic-plutonic assemblage centered on Kakagi Lake, northwestern Ontario, has been sampled for the determination of background gold content. The area lies toward the western end of the Wabigoon belt. One hundred sixty-six gold analyses by neutron activation methods show that the major rock groups including mafic volcanics, felsic volcanics, metasedimentary rocks, mafic-ultramafic intrusions, and felsic plutonic stocks contain average background gold levels of about 1 to 2 ppb. The maximum range in average values is from a low of 0.78 ppb in mafic-ultramafic intrusions to a high of 1.75 ppb in mafic volcanics.Several anomalous gold occurrences (greater than 10 ppb) associated with quartz veins, carbonate zones, shear zones, small felsic intrusions, and felsic stocks were investigated. Some analyses of separated sulfide minerals were also carried out.Primary gold abundance levels in igneous rocks do not correlate significantly with lithology. In particular, there is little if any correlation of gold with chemical differentiation indexes for the mafic and felsic volcanic rocks. Much of the secondary dispersion of gold occasionally leading to concentration to the ppm level cannot obviously be correlated with lithology of the host rock but appears more closely related to structures that permit fluid circulation, to hydrothermal alteration, and to the presence of sulfides. In general, process-related factors rather than background gold content of host rocks are apparently more important in the generation of anomalous gold levels.