Abstract
Abstract. New U-Th-Pb zircon data (SIMS) from three intrusive phases of the Palaeoproterozoic Viterliden intrusion in the western Skellefte District, central Fennoscandian Shield, dates igneous emplacement in a narrow time interval at about 1.89 Ga. A locally occurring quartz-plagioclase porphyritic tonalite, here dated at 1889 ± 3 Ma, is considered the youngest of the intrusive units, based on the new age data and field evidence. This supports an existing interpretation of its fault-controlled emplacement after intrusion of the dominating hornblende-tonalite units, in this study dated at 1892 ± 3 Ma. The Viterliden magmatism was synchronous with the oldest units of the Jörn type early-orogenic intrusions in the eastern part of the district (1.89–1.88 Ga; cf. Gonzàles Roldán, 2010). A U-Pb zircon age for a felsic metavolcanic rock from the hanging-wall to the Kristineberg VMS deposit, immediately south of the Viterliden intrusion, is constrained at 1883 ± 6 Ma in this study. It provides a minimum age for the Kristineberg ore deposit and suggests contemporaneous igneous/volcanic activity throughout the Skellefte District. Furthermore, it supports the view that the Skellefte Group defines a laterally continuous belt throughout this "ore district". Tentative correlation of the 1889 ± 3 Ma quartz-plagioclase porphyritic tonalite with the Kristineberg "mine porphyry" suggests that these units are coeval at about 1.89 Ga. Based on the new age determinations, the Viterliden intrusion may equally well have intruded into or locally acted as a basement for the ore-hosting Skellefte Group volcanic rocks.
Highlights
The Skellefte District (Fig. 1) is one of the most important mining districts in northern Europe with numerous VMS deposits and a large potential for future discoveries (Carranza and Sadeghi, 2010)
A U-Pb zircon age for a felsic metavolcanic rock from the hanging-wall to the Kristineberg VMS deposit, immediately south of the Viterliden intrusion, is constrained at 1883 ± 6 Ma in this study. It provides a minimum age for the Kristineberg ore deposit and suggests contemporaneous igneous/volcanic activity throughout the Skellefte District
This study presents new U-Th-Pb zircon data from four different igneous units in the Kristineberg area in the western part of the Skellefte District: three compositionally different intrusive units of the composite Viterliden intrusion and one volcanic unit within the stratigraphic hanging-wall to the Kristineberg deposit
Summary
The Skellefte District (Fig. 1) is one of the most important mining districts in northern Europe with numerous VMS deposits and a large potential for future discoveries (Carranza and Sadeghi, 2010). Besides constraining the emplacement history of the composite intrusion, dating several intrusive units from a geographically small area aims at investigating the consistency of igneous zircon crystallization ages within different magmatic components of this plutonic complex. The latter is especially important because of the relatively old published age of the Viterliden intrusion with respect to the other early-orogenic intrusive units in the district The obtained age data will be interpreted and discussed with respect to the evolution of igneous activity in the Skellefte District, with special emphasis on the timing of VMS mineralization at Kristineberg
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