Anomalies in insect nest structures at the Garden Well gold deposit: Investigation of mound-forming termites, subterranean termites and ants

Previous research has demonstrated that small mounds of the termite Tumulitermes tumuli (Froggatt) can successfully be used as a geochemical sample medium for detecting Au mineralization concealed beneath transported cover. This finding is in contrast to the use of large mound forming species typically targeted for exploration in northern Australia and Africa. Large areas of Australia not only have small mound forming termites present but also have subterranean termites and ants. Subterranean termites can have large nests hidden subsurface. When foraging they sheath their food sources with soil in order to create a microclimate. Here we investigate the use of this material along with nest material from an ant species as sampling media for geochemical exploration in the Yilgarn Craton, Western Australia. Samples were collected along a transect at the Garden Well Au deposit in the Duketon Greenstone Belt of the Yilgarn Craton in Western Australia. Elevated Au concentrations (above a background level similar to 2 ppb) were found in all 3 nest structure types over the mineralization. The mound forming termite (T. tumuli), which forms structures to 60 cm in height, had up to 7.4 ppb Au. The subterranean termite (Schedorhinotermes actuosus) had up to 8.4 ppb, in the sheath material, and an ant species (Rhytidoponera mayri) recorded Au up to 24.4 ppb, in the nest material. Vertical movement of Au, Cu and Zn from at least 1.4 m deep is supported by evidence in the form of XRD studies and mineral grain counts of nests. These show vertical movement of calcite-rich fragments associated with elevated Au. This is the first investigation of the suitability of subterranean termites for use in geochemical exploration and results suggest that they and ants in the same area represent a potentially useful sample media. (C) 2014 Published by Elsevier B.V.