Open this publication in new window or tab >>Show others...
2022 (English)In: Precambrian Research, ISSN 0301-9268, E-ISSN 1872-7433, Vol. 372, article id 106613Article in journal (Refereed) Published
Abstract [en]
To constrain the tectonothermal evolution of the type locality for iron oxide-apatite deposits, we have obtained U-Pb zircon, titanite, and apatite age data for the Kiruna mining district in northernmost Sweden. The results indicate that the host basin initiated in an overall extensional regime as indicated by the deposition of alluvial conglomerates and greywackes. A volcanic intercalation in a conglomerate unit northwest of the Luossavaara iron oxide-apatite deposit yields a U-Pb zircon age of 1887 ± 3 Ma representing the timing of the earliest Orosirian volcanism in the central Kiruna mining district coinciding with the onset of basin development. In-situ analysis of titanite on hydrothermally altered fracture planes within a cataclastic fault damage zone (c. 270 m from the fault core system associated to the Luossavaara iron oxide-apatite deposit) yields complex U-Pb data. Applying a strict discordance filter yields a 207Pb/206Pb age of 1889 ± 26 Ma. The age implies that the fault probably has a syn-volcanic origin and that syn-volcanic faults may have played an important role during iron ore emplacement. The mineralized basin was subsequently buried and metamorphosed under upper greenschist-facies conditions and later tectonically exhumed and cooled below the apatite closure temperature at 1805 ± 26 Ma indicated by apatite from the Nukutus iron oxide-apatite deposit. Basin inversion is temporally constrained by syn-tectonic titanite as part of sodic-calcic + Fe + Cl hydrothermal alteration along a brittle-ductile reverse shear zone to the east of the study area. Titanite grains that show sector and oscillatory zoning yield an age of 1812 ± 3 Ma, which we interpret as the onset of basin inversion. Homogeneous (relatively unzoned) titanite in the same sample yields an age of 1802 ± 8 Ma, tentatively indicating that the tectonothermal activity lasted up to c. 20 m.y.
Place, publisher, year, edition, pages
Elsevier, 2022
Keywords
Geochronology, Kiruna, IOA, basin development, basin inversion
National Category
Geology
Research subject
Ore Geology; Centre - Centre for Advanced Mining & Metallurgy (CAMM)
Identifiers
urn:nbn:se:ltu:diva-87738 (URN)10.1016/j.precamres.2022.106613 (DOI)000807894300001 ()2-s2.0-85125532558 (Scopus ID)
Funder
EU, Horizon 2020, 776804
Note
Validerad;2022;Nivå 2;2022-03-31 (hanlid);
Funder: Centre of Advanced Mining and Metallurgy (CAMM) (2450-2009); Science Foundation Ireland (SFI) (13/RC/2092 and 13/RC/2092_P2)
2021-11-032021-11-032023-09-05Bibliographically approved