MAPPING MINERAL DISPERSAL IN SUBGLACIAL TILLS FROM REMOTELY PILOTED AIRCRAFT SYSTEMS

Recent advances in Remotely Piloted Aircraft Systems (RPAS) provide a platform for versatile, maneuverable, and cost-effective airborne surveys with a range of small geophysical payloads. The miniaturization of geophysical sensors allows them to be mounted on remotely piloted aircraft and flown at an intermediate scale between traditional airborne and ground-based surveys. This study outlines the basic parameters for collecting magnetic, radiometric, and LiDAR data using an RPAS for Quaternary geology mapping in British Columbia, Canada.

A commercially available, terrain-following, exchangeable payload RPAS collected data over subglacial tills of British Columbia’s Interior Plateau, a region known to host significant alkalic and calcalkalic porphyry systems. Thick glacial sediment cover, with limited exposed outcrop, largely obscures this region, requiring alternative prospecting techniques including airborne geophysics and drift prospecting. Data collected using an RPAS for each survey location is compared to traditional airborne and ground-based methods to determine its applicability and resolution constraints. The RPAS uses a radar altimeter, allowing pilots to plan missions that actively follow the terrain and keep the aircraft at a set altitude above ground. LiDAR and photogrammetric payloads produce data to build bare-earth digital elevation models and large-scale surficial geology maps. Detailed contacts on these maps delineate tills produced by different depositional processes.

Elevated signatures in RPAS magnetic data result from magnetite, an accessory mineral within magmatic bodies and porphyry systems, preserved in the subglacial till matrix. Radiometric anomalies are caused by many factors including the presence of K-bearing minerals in the till matrix, potentially related to hydrothermal alteration minerals associated with the emplacement of a fertile porphyritic intrusion. Anomalous RPAS magnetic and radiometric signatures in subglacial tills may be used to subdivide till units based on mineral potential or combined with ice-flow data and surficial geology mapping (i.e., the principles of drift prospecting) to identify prospective bedrock-source locations.