The Utility of High-resolution Geophysical Data for Assessing Geoscientific Suitability of Crystalline Rock

Abstract

The Nuclear Waste Management Organization (NWMO) is currently conducting initial field studies in a number of communities participating in a site selection process to find an informed and willing community to host Canada’s deep geological repository for used nuclear fuel.Initial field studies involve activities such as high resolution airborne geophysical surveys and direct geological mapping observations. These field activities are designed to further advance the geological understanding of the areas being studied, building on previously conducted desktop studies. Consistent with NWMO’s approach, all field activities are planned and conducted with the involvement and collaboration of the communities and Aboriginal peoples.This paper provides a description of how high resolution airborne magnetic and gravity geophysical surveys are used to extract and interpret the geological and structural characteristics of crystalline rocks over large areas.A description of the site evaluation process and the geological mapping to ground-truth remotely-sensed geological interpretations areprovided in twocompanion papers.Interpretationof high-resolution airborne magnetic and gravimetric data relies on relative contrasts to identify the spatial patternsover large areas. The collected data can be integrated in conjunction with other remote sensing data (e.g. aerial imagery, digital elevation model)to identify potential structural lineaments such as fractures, faults and dykes. Lineament interpretations require professional expertise, and follow established structural rules. In order to ensure consistency between assessments, a systematic three-step workflow for lineament interpretationswas developed, which included: (1) lineament interpretations being completed by two interpreters; (2) interpreted lineaments were integrated to determine reproducibility between the two interpreters; and (3) integration of lineament interpretations for the surficial data sets followed by integration of the combined surficial data set with the magnetic data set. Over the course of these three steps, a comprehensive list of attributes for each lineament was compiled (e.g. certainty, reproducibility, coincidence, length, and orientation).