Thermal Histories and Critical Mineral Systems in the Bergslagen Ore Province, Fennoscandian Shield

The Bergslagen ore province, part of the Swedish Fennoscandian Shield, hosts the largest rare earth element (REE) reserve in the EU and significant base metal deposits, highlighting its critical raw material potential. The EU-funded Marie Skłodowska-Curie project "CRITTER: Strengthening the Critical Raw Material Independence of the EU through Thermochronology" (ID: 101154535) aims to reconstruct the thermal history of Bergslagen, focusing on cooling, reheating, and ore mobilization over the past 1.8 Ga.

We apply high-temperature Rb-Sr thermochronology on mica at the University of Gothenburg and low-temperature U-Th-He thermochronology on zircon and rutile at the University of Göttingen. This interdisciplinary approach targets minimally altered granites and pegmatites near key mineral deposits, including Bastnäs (REE) and Håkansboda (Cu-Co).

Preliminary Rb-Sr results reveal two distinct age groups (~1700–1500 Ma and ~1050–1350 Ma), suggesting episodic thermal activity linked to regional tectonics. Results from Blötberget (Grängesberg) and I-Edda (Örebro) cores reveal biotite Rb-Sr ages around 1.6-1.5 Ga.

These findings suggest that far-field tectonic events, even within stable cratons, can influence thermal evolution and ore remobilization, advancing our understanding of mineral systems. This study contributes to refining exploration criteria by integrating thermochronology and geochemical techniques for efficient mineral exploration.