Energy Drive for the Kiruna Mining District Mineral System(s): Insights from U-Pb Zircon Geochronology

• Published in: Minerals
• Main Authors: Leslie Logan, Joel B. H. Andersson, Martin J. Whitehouse, Olof Martinsson, Tobias E. Bauer
• Format: Article in Journal/Newspaper
• Language: English
• Published: MDPI AG 2022
• Subjects: Kiruna; mineral system; U-Pb zircon geochronology; IOA; IOCG; Mineralogy; QE351-399.2
• Online Access: https://doi.org/10.3390/min12070875; https://doaj.org/article/77d180b6479a4ce7b1eb74183ea055dd

The Kiruna mining district, Sweden, known for the type locality of Kiruna-type iron oxide–apatite (IOA) deposits, also hosts several Cu-mineralized deposits including iron oxide–copper–gold (IOCG), exhalative stratiform Cu-(Fe-Zn), and structurally controlled to stratabound Cu ± Au. However the relationship between the IOA and Cu-systems has not been contextualized within the regional tectonic evolution. A broader mineral systems approach is taken to assess the timing of energy drive(s) within a regional tectonic framework by conducting U-Pb zircon geochronology on intrusions from areas where Cu-mineralization is spatially proximal. Results unanimously yield U-Pb ages from the early Svecokarelian orogeny (ca. 1923–1867 Ma including age uncertainties), except one sample from the Archean basement (2698 ± 3 Ma), indicating that a distinct thermal drive from magmatic activity was prominent for the early orogenic phase. A weighted average 207 Pb/ 206 Pb age of 1877 ± 10 Ma of an iron-oxide-enriched gabbroic pluton overlaps in age with the Kiirunavaara IOA deposit and is suggested as a candidate for contributing mafic signatures to the IOA ore. The results leave the role of a late energy drive (and subsequent late Cu-mineralization and/or remobilization) ambiguous, despite evidence showing a late regional magmatic-style hydrothermal alteration is present in the district.