GROUNDWATER SAMPLING METHODOLOGY FOR MINERAL EXPLORATION IN GLACIATED TERRAIN USING REVERSE CIRCULATION OVERBURDEN DRILLING

A technique to sample groundwaters in the basal sediment aquifers of regions characterized by thick glacial sediments using reverse circulation drilling has been developed together with a methodology for carrying out detailed groundwater hydrogeochemical surveys aimed at discovery of sub-outcropping and deep-seated ore deposits. The method consists essentially of five steps, namely: (1) overburden drilling using a stable tracer dye to monitor the effects of drill water input into the basal aquifer, (2) removal of the tricones from the drill bit to allow emplacement of the piezometer unit and injection of filter sand packs and bentonite seals, (3) development of groundwater in the basal aquifer to remove drill water inputs, (4) emplacement of the piezometer unit and injection of the filter sand pack and bentonite seal, and (5) further development of the piezometer installation followed by sampling of basal aquifer groundwater and measurement of piezometric heads. The piezometer installation and sampling procedures can be performed with a minimal amount of training by geological technicians either employed by mining companies or more generally by overburden drilling management companies as part of their contractual agreement with a mining company.