Limitations in Geophysical Processing and Interpretation: Three Canadian Case Studies

Abstract

With an increasing demand on natural resources, more efficient prospecting techniques need to be developed. One important tool is geophysical methodologies. As technology develops so do these methods and availability of high-resolution information; however if this information is not properly corrected biased results are achieved. This thesis intends to explore common limitations faced by modern geophysical surveys. Processing and interpreting of geophysical data is often accomplished in frequency domain due to speed and efficiency; however this often leads to non-geologically correct results. A spatial domain filter based on potential field signal curvature analysis is a proposed alternative. By isolating specific curvatures, one is isolating specific frequencies, which are generated by sources at particular depths. The method was applied to synthetic and real-world datasets. Following filtering two analytic routines were applied, which showed that the spatially filtered datasets provided cleaner results. Terrain corrections have always been applied to gravity datasets, but rarely are terrain corrections implemented as a pre-processing step in magnetic survey interpretation. Therefore, interpretations based on anomalies from non-corrected magnetic data may be of non-geological features. In a magnetic survey conducted in the mid-eighties, magnetic lows were associated with alteration; however, at that time of initial interpretation no terrain correction was applied. This dataset was revisited and terrain corrected, which showed that the magnetic lows were associated with unaccounted bathymetry. The Bathurst Mining Camp (BMC) is one of Canada's most important base metal mines, but is threatened by a fluctuating mineral resources market. By using high resolution geophysical surveys potential mineral reserves may be located. However, in order to do so a better understanding of geology is necessary, which is often difficult due to limited outcrops. Through the processing and interpretation of recent geophysical datasets, a revised geological map of a selected portion of the BMC has been developed.