Summary:
The Ohmgebirge Project is characterized by evaporite deposits within the Upper Permian Zechstein Group. These deposits originated from the Zechstein Sea, a basin in northern Europe with relict sea characteristics. The Zechstein Group comprises seven depositional cycles, with the South Harz district potash mineralization hosted in the second cycle, specifically the Kaliflöz Staßfurt horizon.
The main potash mineralization is hosted within the Kaliflöz Staßfurt unit of the Zechstein Group, exhibiting characteristics such as continuous layer-bound mineralization, including carnallitite and sylvinite.
There is very little variation in mineralogy or grade across Ohmgebirge. Sylvinite is dominant and attains an average thickness of 7.2m. A 15m thick Carnallite unit is seen underlying the Sylvinite in the south-east of the licence area. The potash seams on Ohmgebirge display gentle localised undulations with no obvious dip.
Potash minerals present include carnallitite and sylvite, with polyhalite and subordinate other minerals such as kieserite, langbeinite, glaserite, and anhydrite. Most deposits have been altered by reaction with percolating water. Faulting, folding and water intrusion have altered or partly dissolved potash, causing regional variability in potash bearing strata within the Zechstein Group.
Tectonic activities in the Mesozoic and Tertiary periods uplifted the Harz Mountains, affecting the Thuringian Basin. The basin's stratigraphy includes evaporite rocks of the Upper Permian Zechstein Group hosting potash mineralization.
The main potash-bearing horizon, Kaliflöz Staßfurt, consists of sylvinite and/or carnallitite. The mineralization shows variations horizontally and vertically, with undulating bedding and localized folding. Hydrogeological hazards, as well as potential influx of liquid and gaseous hydrocarbons, have influenced mining operations historically, necessitating safe operating management strategies.
Economic minerals include sylvite and carnallite for potash production, with variations in mineral composition affecting processing. Insoluble materials such as anhydrite, clay, and dolomite downgrade potash deposits. Sylvinite and carnallitite are the predominant economic rock types.
The potash-bearing target Zechstein Group consists of seven depositional cycles with the potash mineralisation of the South Harz Potash District hosted within the second cycle, the Staßfurt Formation (Z2). The Z2 is further sub-divided into horizons, of which the Kaliflöz Staßfurt (z2KSt) hosts potentially economic potash. The z2KSt is split into a Hanging Wall Group that has 11 to 19 horizons of finely layered potassium salts and a Footwall Group that has 1 to 10 coarsely layered potassium salts and thick halite layers. Mineralised z2KSt occurs across almost the whole of the Ohmgebirge mining licence, with an area to the west that is barren. The z2KSt is present in 35 drill holes used in the 2019 Ohmgebirge model, 12 of which exist within the licence area.
The mineralogy on Ohmgebirge is dominated by Sylvinite with carnallite intersected in only one hole within the licence area. The sylvite seam was modelled as one horizon, and was historically known as Sylvinite, and the carnallite seam was modelled separately.
A major graben has been historically mapped within the Ohmgebirge mining licence trending NNE-SSW with offsets of 150 m to 250 m. The results of the graben have been logged in the downhole geophysical logs of drill holes on Ohmgebirge with noted steeper bedding, dipping joints and deformation in the strata accompanied by gases. In the centre of the graben the Leine-Steinsalz through to the Aller-Steinsalz units have thickened whilst the rock salt units have thinned resulting in a weakened hanging-wall. No evidence of displacement in the z2KSt unit have been modelled.
Dimensions
The economic potash deposit covers almost the entire Ohmgebirge mining licence, with a small, oval-shaped barren zone in the west that continues approximately 1 km to the west of the mining licence. Based on interpretation of drill hole data and historical plan maps, the mineralised z2KSt continues to the north, south, east and west of Ohmgebirge.
The mineral resource has been restricted by a minimum grade cut-off of >5% K2O. The total mineral resource area for Ohmgebirge is approximately 21.7 km2 and the total Mineral Resources tonnage, with a 15% geological loss applied) is 377 Mt containing 46 Mt of K2O. The minimum depth from surface to the roof of the economic potash is ±565 m and the maximum depth to the base of the potash seam is ±922 m.