Value element distribution in the Sangerhäuser Kupferschiefer – Insights from old drill cores

Driven by the Critical Raw Materials Act and the associated search for raw materials in Germany, old Kupferschiefer mining districts are gaining the interest of research and exploration again. In the former Sangerhäuser district, the Kupferschiefer dips to the south and is dissected by faults separating different tectonic blocks. Consequently, the depth of the Kupferschiefer varies from bedrock outcrops immediately south of the Harz mountains to about 1000 m depth. Access to new sample material is difficult as the old mining fields are no longer accessible and have largely been flooded, but archived drill cores from before the 1960s exist.

Here, we report on examined drill cores from bore holes distributed over approximately 160 km². The data are used in order to better understand the lateral and vertical element distribution of critical elements such as vanadium, molybdenum, cobalt, nickel, and copper within the Kupferschiefer-type mineralisation. The element concentrations were determined using a portable X-ray fluorescence analyser.

The analyses of the drill cores clearly show that the mineralisation extends from the Kupferschiefer (T1) into the underlying footwall sandstone and the hangingwall Zechstein carbonate above. Based on preliminary data, the highest contents of copper are commonly found in the uppermost part of the sandstone or in the lowest parts of the Kupferschiefer. In some cases, however, the highest metal contents occur in the Zechstein carbonate. While vanadium appears to be mainly bound to the Kupferschiefer itself, measurable contents (<50 µg/g) of cobalt and nickel correspond mainly with areas of copper mineralisation.