Coupling georadar field data with numerical modeling to increase the effectiveness in the exploration of crystallized mineral cavities

Abstract

Demand for mineral specimens which are naturally occurring in crystallized mineral cavities in rocks (or Mineral Specimen Cavities – MSCs) is currently on the rise. Predictions indicate that this trend will most probably be maintained at least for the forthcoming years. In order for the supply to satisfy the demand, the prospecting process, i.e., the activity of discovering and extracting these mineral specimens, needs to be accordingly adapted. One possible way for this to be achieved is to employ geophysical exploration methods. Past surveys have demonstrated that the georadar (or Ground Penetrating Radar – GPR) could be a suitable method to locate MSCs. However, various reasons such as geological complexity, unrealistic expectations and/or ambiguities in the produced imagery have resulted for the method to be generally disregarded. Despite that fact, it is believed that appropriate optimization of the georadar can provide multiple benefits. In this direction and within this thesis, actual georadar field measurements from an area known to host MSCs were coupled with Finite-Difference Time-Domain (FDTD) numerical modeling simulations. The main observations can be summarized in 3 key points. 1) Boundary delineation between the host and target lithological units is an effective technique to categorize subsurface reflections according to their possibility of being MSCs. 2) Different georadar antenna orientations can potentially provide imagery that more closely represents the actual geometry of the reflector. 3) Indications regarding the filling material of subsurface features (e.g., clay, air) can be extracted by examining the recorded signal polarity and/or by plotting the spectrums at the areas of interest. Under the appropriate circumstances, the aforementioned observations can be particularly useful and increase the overall effectiveness of the georadar when prospecting for MSCs.