The delineation of graphite deposits of former mines in Lower Austria using the transient electromagnetic method

Abstract

Geological cross-sections (GCs) are valuable tools for understanding the subsurface, but their limitations become evident in the interpretation of deep mineral deposits, such as graphite. Typically, GCs are built based on near-surface observations and rely on the interpolation of the data; thus, also limiting the spatial resolution of the structures defined. Geophysical methods can play a crucial role in extending the interpretation of GCs both horizontally and vertically. This study investigates the effectiveness of the transient electromagnetic (TEM) method for graphite exploration in Lower Austria. We conducted TEM soundings to map large areas of difficult access and identify high electrical conductivity values (i.e., conductive anomalies) associated with potential graphite deposits. Our results demonstrate the strength of TEM as an efficient tool for graphite prospection, particularly suitable for abandoned mining areas and previously unexplored regions. We identified high-conductivity anomalies at depths of around 40 m, which correspond to surface areas where paragneiss and marble units are in contact, suggesting a high potential for flake-type graphite deposits. These anomalies align well with known graphite occurrences documented in geological maps. We also evaluate the abilities of the TEM method to map graphite-rich zones using numerical experiments.