Near-Surface Geophysical Investigation of Historic Mines in Ore Mountains, Czechia

Keywords: Historic mines, Near-surface geophysics, Montan-archaeology, Mining heritage The Ore Mountains are known for a considerable number of mineral deposits that have played an important role in the development of human activities at least from the early Bronze Age to recent times. This long period of prospecting and mining led to the creation of a unique mining landscape, recognised today as a UNESCO World Heritage Site. The underground mining relics, which have often been disused for hundreds of years, are an interesting target for mining archaeology and can often be converted into a mining museum. Many historic mines have an uncertain or unknown location, which, combined with the complicated relief of the mining landscape, makes excavation and further investigation a challenge. In one of the tin mining districts in the village of Hřebečná, we have investigated several sites where shallow mines from the early modern period are suspected, using a range of near-surface geophysical methods, the evaluation of historical sources, and terrain analysis. We have used microgravity survey in combination with electrical resistivity tomography and ground penetrating radar. We describe the entire process from the planning phase, including the evaluation of prior historical and geological knowledge, through to processing of observed field data. Then we discuss general capabilities of each geophysical method for the detection of voids in different states of preservation. Special attention is paid to complex interpretation in the case of conflicting results from different methods and to the determination of the most likely locations of the structures. In addition, we examine the possibility of creating density models through different modelling strategies and the reliability of models in case of significant measurement errors. The modelling includes forward modelling of the response from different scenarios with added noise according to our measurement error to estimate the detection chances for the empty, partially filled and filled mining adit, as a feasibility study, and interpretation modelling based on observed data as well.