Widespread occurrence of aquifers currently undetectable with the MRS technique in the Grenville geological province, Canada

Abstract

In the summer of 2003, a series of field tests were made over aquifers within or next to the Grenville geological province, Canada. Twelve sites distributed within three general areas of the province and nearby to its southern border were surveyed with the MRS (Magnetic Resonance Sounding) technique. Each site was characterized by saturated shallow water bearing layers of high effective porosity. The tests were planned to evaluate the MRS technology in such environments for groundwater resources quantification and aquifer/aquitard media characterization. A priori, the environmental conditions in Eastern Canada were assumed favorable for MRS work such as low to moderate ambient noise, earth's field value above 55,000 nT, targets consisting of shallow and high porosity aquifers. Despite such conditions, no clear MRS responses were observed. Following supplementary investigations, this is now attributed to the wide-scale occurrence of disseminated magnetite within the aquifers which shorten the signal decay time. Although the lack of MRS response over aquifers has been reported before, this was not the case for such widespread occurrence. This also supports the adaptation of the MRS technology to conditions similar to those observed in the Grenville province.