JORC-Compliant Exploration in South Harz Potash District: A Historical Review

The South Harz Potash District, nestled in Germany’s heartland, stands as a testament to over 120 years of Muriate of Potash (MOP) production, positioning it among the premier global MOP sources.

It was in 1888, near Kehmstedt in northern Thuringia, that potash exploration, destined to meet JORC standards, took root in the South Harz Potash District. Initial drill results not only confirmed the presence of potash-rich salt rocks in the Harz Mountains’ southern reaches but also spearheaded expansive potash exploration throughout the region. By 1897, the legacy was solidified with the establishment of the Sondershausen mine, marking the inauguration of potash mining in the district.

The South Harz Potash District’s legacy lies in its historical approach to mining potash ores. Conventional underground room and pillar mining techniques were the method of choice, a practice that underscores its longstanding mining tradition.

 

In the heart of the South Harz District, two potent economic potash-bearing rock types emerge as industry standouts: carnallitite and sylvinite. The dominant player in terms of area coverage is carnallitite, a mineral makeup defined by:

• Carnallite – KMgCl3∙6(H2O); and
• Sylvite – KCl.

While carnallitite presents with a modest percentage of K2O compared to sylvinite, it comes with its unique challenges. Its brittle nature demands rigorous safety standards, necessitating backfilling of underground shafts to combat the critical issue of subsidence.

Sylvinite, colloquially termed ‘Hartsalz’ by seasoned miners, is distinguished by its distinct hardness during drilling, a trait attributed to the composite of sulphate minerals.

The South Harz Potash District’s historical footprint is monumental. During its peak operations, the GDR notched its position among the world’s top three potash producers. Tracing back the timeline, the district recorded an impressive surge in K2O tonnage, from 1,336 kt K2O in 1950 to a peak of 3,510 kt K2O by 1988. Accounting for an impressive 43% of the GDR’s total production in 1985, the region’s mining legacy is rooted in traditional underground techniques.

Today, the South Harz Potash District’s legacy endures with the BWE Kehmstedt operation. Through advanced solution mining techniques, it proudly delivers over 100,000 tonnes of MOP annually.

Geological Insight into the JORC-Recognized South Harz Potash Deposits

Origins and Settings: The South Harz Potash District, a JORC-acknowledged project, takes its geological seat within the expansive Thuringian Basin, renowned for its potash-enriched evaporite sequence stemming from the Permian era. These deposits owe their genesis to the Zechstein Sea, a saline expanse that once sprawled from England’s northern tips, through central Poland, reaching eastern France. These iconic Zechstein Evaporites, primarily developed along the sea’s peripheries, have, for generations, been a prolific source of salts, potassium fertilisers, and hydrocarbons.

Geological Comparisons and Depth: What’s intriguing is the geology bolstering the South Harz Potash District isn’t singular to this region alone. This geological DNA also underpins the renowned Sirius Minerals’ Woodsmith Mine, ICL’s Boulby Mine in England, and the K+S’s potash mines scattered across Germany’s heartland. Thanks to a robust history of mining and exploration, the geological intricacies of this project, especially its potash mineralisation, are meticulously documented. In the South Harz domain, the potash-rich strata dwell at depths spanning 500m to 1,200m. Crowning these depths are marine layers composed of sandstones, marl, mudstones, dolomite, and siltstones.

Potash Mineralisation Details: The Permian Stassfurt Formation graciously hosts the potash mineralisation evident throughout the South Harz Potash District. Nestled within this formation, the Kaliflöz Stassfurt unit (z2KSt) accounts for the lion’s share of potash seams across the expanse. Exhibiting a thickness of up to 58 m, the Kaliflöz Staßfurt’s core reveals a transition in mineralisation—shifting from a sylvinitic character to a dominant carnallitic composition.

Geological cross section through the South Harz Potash District

 

In-depth Overview of JORC-Compliant SHP Licences

Portfolio Composition: SHP’s esteemed project portfolio proudly holds three perpetual potash mining licences: Ebeleben, Mühlhausen-Nohra, and Ohmgebirge. Additionally, it houses two potash exploration licences, namely Küllstedt and Gräfentonna, cumulatively spanning an area close to 659km². These JORC-acknowledged licences encapsulate five historic underground potash mines, which ceased operations in the 1990s.

Historic Exploration and Data: Historical exploration stands as testimony to the district’s rich potash deposits. Both the three perpetual mining licence zones and the exploration domain of Küllstedt have undergone rigorous potash exploration. This was conducted by the state mining corporation of the erstwhile GDR, resulting in an invaluable database of drillholes and technical examinations that endorse the prevailing geological model. The Gräfentonna licence saw an intense hydrocarbon exploration, with much of its data now being redirected to appraise potash potential within the South Harz Potash District.

Mining Prospects in the 1990s: Turning the pages back to 1991, the Volkenroda mine was on the brink of eastward expansion into the Ebeleben Mining Licence territory. Notably, the foundation for a new ventilation shaft was already in place, nearing its completion. Parallel explorations were also on the anvil to either stretch the Volkenroda mine westwards or to inaugurate a fresh, independent mining operation within the Mühlhausen-Nohra Mining Licence precinct, an area now under SHP’s jurisdiction.

SHP’s Pioneering Efforts in JORC 2012 Compliant Resources

1. Objectives and Focus (2017-2020): Over the span of these crucial years, SHP intensely delved into their expansive archive of exploration drillhole data and technical research. The primary goal? To define resources compliant with the JORC 2012 guidelines and to lay down robust technical and economic blueprints for every licence zone.

2. Ebeleben – The Initial Findings (April 2018): SHP made its first major announcement about the Ebeleben area, introducing a JORC 2012 Inferred resource approximation of 557 million tonnes, having a 12.1% K2O grade.

3. Expanding Horizons – Mühlhausen-Keula (October 2018): SHP broadened its resources spectrum with a declaration about the Mühlhausen-Keula sub-domain. This added a massive Inferred resource of 1.13 billion tonnes, with an average 11.1% K2O grading.

4. Insights from Nohra-Elende (November 2018): A detailed insight from the Nohra-Elende Sub-Area brought into light another Inferred resource addition of 1,698 million tonnes, rated at 9.7% K2O.

5. Küllstedt Exploration – A JORC Masterstroke (February 2019): SHP’s Küllstedt Exploration Licence revealed an additional 1.54 billion tonnes of JORC 2012 Inferred resources, marked at 10.7% K2O.

6. Ohmgebirge – The Finale (December 2019): Closing the year, SHP unveiled an enhancement to JORC 2012 resources for its Ohmgebirge Mining Licence – a whopping 325 million tonnes at a 13.1% K2O grade.

7. Expert Insights from Micon International: In a partnership with Micon International Co. Limited, SHP discerned another segment of the Nohra-Elende sub-zone as a potential Exploration Target. This was due to the extensive drill spacing which prevented the determination of an Inferred resource. In January 2019, the target specifics were released, estimating between 638 to 1,162 million tonnes at a 9.2 – 11.1 % K2O* grade.

SHP now oversees more than 5.25 billion tonnes with an average grade of 10.8% K2O under the JORC Inferred Resource category. This includes 1.85 billion tonnes of Sylvinite with a grade of 13.2% K2O. The total contained K2O across the Ebeleben, Mühlhausen-Nohra, and Ohmgebirge Mining Licences, as well as the Küllstedt Exploration Licence, now surpasses 566 million tonnes.

SHP Inferred Resources (JORC 2012) – Ebeleben, Ohmgebirge and Mühlhausen-Nohra Mining Licences (including Mühlhausen-Keula and Nohra-Elende sub-areas) and Küllstedt Exploration Licence

 

Exploration Target (JORC 2012) – Nohra-Elende sub-area, part of the Mühlhausen-Nohra Mining Licence*

*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.

Magnesium Sulphate Resource

In September 2020, SHP unveiled a JORC 2021 compliant resource estimate for Magnesium Sulphate (MgSO4), specifically Kieserite, in the Nohra-Elende Sub-area. The revealed resource stands at an impressive 768Mt with an average grade of 8.1% magnesium sulphate, showcasing intersections reaching up to 20%.

This valuable magnesium sulphate is primarily derived from the mineral Kieserite (MgSO4.H2O). From the extensive database encompassing 92 drillholes located in the Nohra-Elende licence vicinity, a significant 72Mt of Kieserite has been identified.

Germany’s K+S Group leads the extraction of natural Kieserite, but with the ore reserves nearing exhaustion, the need for an alternative source is evident. Outside of Germany, China emerges as a dominant player, producing magnesium sulphate via a synthetic approach involving hot acids.

The versatility of magnesium sulphate is evident in its diverse applications. It can be marketed in its pure form, amalgamated with potash (MOP) to curate high-quality fertilizers, or combined with MOP to produce potassium sulphate (SOP).

Location of the JORC 2012 mineral resources within the SHP Project Portfolio (May 2021)

 

Exploration Potential

Küllstedt Exploration Licence

The Küllstedt exploration licence boasts a rich history of mining and exploration activities, including three vertical shafts that remained operational until 1924 (these have since been removed from the tenement). Additional exploration within this licence encompasses potash-focused drill holes and hydrocarbon wells that penetrated the potash strata of interest.

Utilizing the geological and assay data from these drill holes, a comprehensive 3D geological model of the potash seam was formulated, culminating in a JORC Inferred resource announcement on 19th Feb 2019. This covers nearly 44% of the total area under the Küllstedt exploration licence. Past explorations led by SHP established that the majority of the Küllstedt area is underpinned by potash. Further, the area showcases a substantial Exploration Target, as outlined in the Davenport Resources replacement Prospectus on 19th Jan 2017. This target presents an opportunity to enhance the potash volumes within SHP’s JORC resource ledger.

Gräfentonna Exploration Licence

The Gräfentonna licence, in comparison to Küllstedt, has limited available geological information. However, its stratigraphic profile aligns closely with the Küllstedt licence and is especially akin to the Ebeleben Mining Licence. Initial data indicates that Gräfentonna houses a sylvinite-rich potash seam extending through its central region, while a carnallitite-heavy potash seam characterizes its eastern portion.

An in-depth geological analysis, combined with the existing drill and geological insights, enabled the derivation of an Exploration Target for the Gräfentonna licence. This target ranges from 2,678 to 3,396 million tonnes, with a K2O grade oscillating between 4.3% and 25% as per the ASX announcement dated 22nd May 2017.

SHP Exploration Target (JORC 2012) – Gräfentonna Exploration Licence (May 2017)*

*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.