South Harz, Germany
The South Harz Potash District, in the northern part of the German Federal State of Thuringia, Central Germany, has a history of producing Muriate of Potash (MOP) from both Sylvinite and Carnallitite ores. Historically, potash ores have been mined by both conventional underground and solution mining operations. Prior to the re-unification of Germany, the former German Democratic Republic produced approximately 3.3 million tonnes of K2O annually.
Davenport’s South Harz Project comprises two exploration licenses covering a total area of approximately 457km2. The Küllstedt license covers an area of 241km2, and the Gräfentonna license covers an area of 216km2, with both licenses granted in January 2015. Under the German Mining Law the exploration licenses are granted for a term of five years with an option to renew for a further three years.
Map of licence location
The project lies within the Thuringian Basin that contains a potash-rich evaporite sequence of Permian age. These so-called Zechstein evaporites have historically been an important source of salts, potassium fertilisers and hydrocarbons in the region. Due to the extensive mining and exploration history in the area, the geology of the project area and potash mineralisation is reasonably well known. The evaporite sequence containing the potash seams within the South Harz area occur at a depth of between 500m and 1,000m below surface. The overlying rocks consist of a marine sequence of sandstones, mudstones, marl, dolomite and siltstones.
Within the Küllstedt license the potash mineralisation is hosted by the Permian Stassfurt Formation which ranges in thickness between 32m and 255m. Within the Stassfurt Formation the Kalifloez Stassfurt unit (z2KSt) contains the potash seam which underlies the entire Küllstedt license area. The potash unit is up to 58 metres thick, and appears to be richer in Carnallite potash mineral in the north and Sylvite mineral in the south. The base of the Stassfurt Formation is a dolomite unit (z2D) that has been of interest to hydrocarbon explorers in the past.
Past mining and exploration within the Küllstedt license has included three vertical shafts which operated up to 1924 (excised from the tenement), as well as potash exploration drill holes and oil wells that have drilled through the potash formations of interest.
Geological data and some assay data for the drill holes has been used to develop a 3D geological model of the potash seam. An Exploration Target for potash within the license is 4,055 million tonnes to 5,141 million tonnes with a grade ranging between 7.2% K2O and 25% K2O. The potential quantity and grade of the Exploration Target is conceptual in nature, there has been insufficient exploration to estimate a mineral resource and it is uncertain if further exploration will result in the estimation of a mineral resource. (replacement Prospectus p30, 19 Jan 2017)
Although less geological information is available on the Gräfentonna license, the stratigraphy is broadly similar to the Küllstedt license. Based on preliminary data there appears to be a sylvinite-dominated seam running down the central part of the license area and carnallitite-dominated seam towards the eastern side of the license.
A detailed geological review and geological model of the potash seam underlying the Gräfentonna licence using the available drilling and geological informationhas allowed an Exploration Target to be calculated of between 2,678 and 3,396 millio tonnes grading between 4.3% and 25% K2O. The potential quantity and grade of the Exploration Target is conceptual in nature, there has been insufficient exploration to estimate a mineral resource and it is uncertain if further exploration will result in the estimation of a mineral resource.
The next phase of the exploration program is to drill confirmation holes on the Küllstedt license twinning existing exploration holes that have intersected potash. This will allow validation of the detailed information from past exploration with the aimupgrading the existing Exploration Target on the Küllstedt license to a JORC-compliant Resource. Davenport is working with regional mining authority to meet the requirements to get approval to commence drilling.