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Archean block rotation in Western Karelia: Resolving dyke swarm patterns in metacraton Karelia-Kola for a refined paleogeographic reconstruction of supercraton Superia

2020; Elsevier BV; Volume: 368-369; Linguagem: Inglês

10.1016/j.lithos.2020.105553

1872-6143

Sarah Davey, Wouter Bleeker, Sandra L. Kamo, Jouni Vuollo, Richard E. Ernst, Brian Cousens,

Hydrocarbon exploration and reservoir analysis

Rifting, breakup, and subsequent collision related to the ca. 1.92–1.79 Ga Svecofennian orogeny fragmented and deformed the western margin of the Archean Karelia-Kola craton into four crustal blocks: Pudasjärvi, Iisalmi, Kuhmo, and Taivalkoski. Detailed quantification of Svecofennian deformation is limited due to poorly exposed basement geology and an as yet incomplete dyke swarm record. New U-Pb ID-TIMS geochronological results on baddeleyite and zircon are presented for three key mafic dykes from the Pudasjärvi block, namely the Uolevinlehto, Myllykangas, and Sipojuntti dykes. The age of the 325°-trending Uolevinlehto dyke is estimated at ca. 2400 ± 12 Ma from discordant multigrain baddeleyite fractions, showing it to be younger than ca. 2450 Ma dykes across Karelia. The 350°-trending Myllykangas dyke has a minimum age of 2135.2 + 3.6/−3.7 Ma based on chemically abraded zircon. Results from single baddeleyite grains provide a precise upper intercept age of 2128.9 ± 1.2 Ma for the 320°-trending Sipojuntti dyke. Our new U-Pb ages are integrated with those from the literature to define six major dyke swarms in the Pudasjärvi block: the NNE-trending ca. 2.45 Ga Pääjärvi, NW-trending ca. 2.40 Ga Uolevinlehto, NW-trending ca. 2.13–2.10 Ga Tohmajärvi, WNW-trending ca. 2.07 Ga Palomaa, NNW-trending ca. 1.98 Ga Paukkajanvaara, and undated “East-West” dykes. Trends of contemporaneous dyke swarms in the Taivalkoski and Kuhmo blocks, however, are systematically offset by 35°. With subvertical dips, offset dyke swarms record 35° clockwise vertical-axis rotation of the Pudasjärvi block relative to the interior of Karelia, consistent with dextral transpression during the Svecofennian orogeny. Structural restoration of the Pudasjärvi block improves the constraints on regional dyke swarm patterns, and these are used to revise the position of the Karelia-Kola craton within the context of the paleogeographic reconstruction of supercraton Superia.