The Kalahari Manganese Field (KMF) of the Northern Cape Province of South Africa hosts about 74% of all known minable manganese ores globally. It represents the largest known land-based Mn deposit. More than 90% of the resource can be best described as mangano-lutite, e.g., a microcrystalline, ovoid-rich, finely laminated chemo-sedimentary rock containing between 30-40 wt.% Mn. Despite its great geological age (2.42 Ga), the mangano-lutite and its surrounding volcano-sedimentary host rock succession (Transvaal Supergroup) have not experienced any significant metamorphic overprint. Owing to its exceptionally fine-grain size and unusual composition, the mineral paragenesis and diagenetic microfabric of the mangano-lutites remain poorly documented. This contribution aims to show that modern SEM-EDS-based image analysis platforms, such as the TESCAN TIMA instrument, can not only provide quantitative mineralogical data, but can also reveal unprecedented insight into diagenetic microfabric and a complex succession of mineral assemblages in the mangano-lutites. The instrumental approach developed for this application is of extreme industrial and economic importance due to increasingly complex ores and a mandatory need to beneficiate by-products in the shift to sustainable mining. It can be easily transferred to other applications on fine-grained rocks (e.g. carbonate mudstones, fault gouges), ores (e.g. nickel laterites, bauxites) or anthropogenic solid materials (e.g. tailings, flue dusts).

Li extraction as a byproduct in deep geothermal power plants is a promising option for the upcoming challenges in Li supply chains. In Germany, regions in the North German Basin and Upper Rhine Valley are suitable for these kind of operations as Li concentrations reach up to 375 mg/l in deep formation waters [1]. To provide further insights on the occurrence of Li in deep formation waters, its geochemical behavior and possible release reactions of Li from mineral dissolution or surface exchange in deep geothermal systems, experiments at in situ conditions (100 – 160 °C, 370 bar) with drill core material of reservoirs rock were conducted in Au capsule and flexible Dickson-type Au-Ti cells. In addition, rock samples were investigated by petrographic and geochemical analysis in order to identify the main Li-bearing mineral phases and their respective Li concentrations. Results of fs-LA-ICP-MS measurements identified chlorite and biotite to be the main Li-bearing minerals, but low Li concentrations were also found in multiple other mineral phases. Batch experiments revealed that a near-equilibrium concentrations for Li are attained rapidly in 3 to 6 days of experimental run time.

[1] Alms, K., Jagert, F., Blömer, J., & Gehrke, I. (2022). Co-production of geothermal energy and lithium from geothermal waters. In European Congress.

Der Terminus „kritische Rohstoffe“ erlangte als Gegenstand der „Mitteilung der Kommission an das Europäische Parlament, den Rat, den Europäischen Wirtschafts- und Sozialausschuss und den Ausschuss der Regionen – Grundstoffmärkte und Rohstoffe: Herausforderungen und Lösungsansätze“ in Europa 2011 erstmals größere öffentliche Aufmerksamkeit.

Eine damals 14 Positionen umfassende Liste wurde seitdem mehrfach erweitert und umfasst derzeit 34 Rohstoffe. Ergänzend wurden im Jahr 2023 „strategische Rohstoffe“ definiert, welche zum größten Teil „kritische Rohstoffe“ beinhalten.

In diesem Vortrag wird der Frage nachgegangen, inwieweit die derzeit bekannten Rohstoffvorkommen Sachsens auch die von der EU definierten kritischen Rohstoffe beinhalten. Weiterhin werden exemplarisch ausgewählte Herausforderungen betrachtet, welche einen entscheidenden Faktor darstellen, ob derartige sächsische Vorkommen (z.B. von Cu, In, REE etc.) auch tatsächlich kurzfristig zur Sicherung der Rohstoffversorgung genutzt werden können.

Für die aktuell funktionierende ökonomische Basis Sachsens ist eine sichere Versorgung mit wesentlich mehr Rohstoffen erforderlich, als derzeit in Form der EU-Liste kritischer Rohstoffe im Fokus der Aufmerksamkeit stehen. Dazu gehören beispielsweise Baurohstoffe. Aber auch die stetige Erweiterung der als „kritisch“ definierten Rohstoffe lässt es sinnvoll erscheinen, für eine langfristige Sicherung der Rohstoffbasis weit vorausschauende Planungen vorzunehmen und nicht zu warten, bis ein Rohstoff offiziell als kritisch erklärt wird. Demgemäß sollten auch derzeit noch als unkritisch betrachtete Rohstoffe bereits jetzt vorsorgend erkundet und zumindest planerisch für eine eventuelle spätere bergbauliche Gewinnung gesichert werden.

Parallel zu diesen Bemühungen gewinnt die Beantwortung der Frage an Aktualität, inwieweit das derzeit prognostizierte weitere Wachstum des Bedarfes an Primärrohstoffen mit einer nachhaltigen Existenz des globalen Ökosystems Erde vereinbar ist.

The Sora Ni-Cu-(PGE) sulfide mineralization is associated with a ~400 x 40 m dike-shaped gabbroic intrusion that is exposed in a dimension stone quarry about 5 km SW of Bautzen (Saxony/Germany). The Sora dike is one of several Ni-Cu-(PGE) sulfide-bearing gabbroic intrusions (e.g. Angstberg, Dahrener Berg, Sohland-Rožany, Kunratice) that occur in the Lausitz and Šluknov region on both sides of the German-Czech border. The gabbroic intrusions are part of interconnected magmatic plumbing systems that intruded Cadomian granodiorites of the Lausitz Block (northern Bohemian Massif) in the Middle to Late Devonian (~390–370 Ma). The Sora dike represents a composite intrusion with olivine gabbronorite, gabbro and diorite as major lithologies. The magmatic sulfide mineralization comprises blebby disseminated sulfides in the olivine gabbronorite and variable-shaped massive sulfide patches that locally occur along both contacts of the gabbroic dike to the granodioritic country rock. Subordinately, larger sulfide patches are also hosted by pegmatitic albite-amphibole-enriched schlieren within the olivine gabbronoritic part of the intrusion. The mineralization represents a typical magmatic sulfide mineral paragenesis with dominating pyrrhotite, pentlandite and chalcopyrite, variable amounts of Fe-Ti oxides and trace amounts of PGE-, Au-, Ag- and TABS-bearing minerals. The PGE mineral assemblage is dominated by Pd melonite. The magmatic sulfides are characterized by relatively high Ni tenors (metal content in 100 % sulfide) and variable Cu, Co, Pt, Pd and Au tenors (~0.3–9.0 wt.% Ni, ~0.2–7.0 wt.% Cu, ~0.1–0.4 wt.% Co, ~20–1210 ppb Pt, ~40–1400 ppb Pd and ~20–1230 ppb Au).

The eastern part of the Erzgebirge region hosts an exceptional abundance of greisen- and vein-hosted Li-Sn-(W) deposits (e.g., the Zinnwald-Cínovec district), located across the eastern part of Germany and the northwestern part of Czech Republic. However, only a few of those deposits have been reliably age-dated (e.g., the Sadisdorf district), leaving the timing of hydrothermal mineralization on the regional scale widely unconstrained.

Here, we report new U-Pb LA-ICP-MS ages of cassiterite from Li-Sn-(W) mineralization at Zinnwald, Altenberg, Niederpöbel, Schmiedeberg, Bärenfels, Lauenstein and Krupka. The new ages of the different localities span between 315.1±3.7/4.4 and 306.6±1.5/3.5 Ma. Therefore, greisen- and vein-hosted cassiterite ages constrain hydrothermal mineralization's timing, on a regional scale, to a narrow time window of ~10 Ma years and are significantly younger than previously proposed ages between 325 and 318 Ma. The new ages are consistent with recent zircon ages of (sub-)volcanic rhyolite units (315 to 313 Ma), which are the host rocks of some of the Li-Sn-(W) granites. Greisen formation and associated cassiterite crystallization thus temporally coincides with the formation of the 315-310 Ma ring dykes linked to the collapse of the Altenberg-Teplice caldera.

The Erzgebirge hosts numerous stratiform tin occurrences, which are located along the same structural level within the Variscan orogenic belt. One of these tin deposits, the Bockau tin occurrence, is located in the area between Aue-Bad Schlema – Bockau – Zschorlau with alternating sequences of quartzite and metaschist. This layered sequence records geochemical signatures of intensely weathered sedimentary rocks. Their protolith probably formed during the Ordovician at the passive continental margin of Gondwana. The mineral assemblage consists of quartz + biotite + garnet + muscovite + andalusite + chlorite + cassiterite + accessory-phases. Cassiterite grains are concentrated in layers concordant to the foliation plane, occur as inclusions within foliation parallel biotite, and are overgrown by garnet blasts. These textures indicate that cassiterite has been present prior to the Variscan continental collision. The frequent occurrence of cassiterite also correlates with the high Sn-contents of the tin bearing metasediments (mainly ranging from < 50 to 2000 ppm). Different methods of conventional thermobarometry and pseudosection modelling were applied to reconstruct the regional metamorphic overprint at 550 ± 50 °C / 8 - 9 kbar and a subsequent thermal peak of at least 600 °C. These results are characteristic for the regional metamorphic conditions reached along the north-western border of the Erzgebirge, though the maximum temperatures reached are slightly higher than previously thought. There is a lack of evidence for a post-magmatic / metasomatic history of the Bockau tin occurrence by the applied methods and petrographic observations.