U-Pb and Rb-Sr isotopic data on an Ordovician volcanic-subvolcanic complex from the Tjopasi Group, Köli Nappes, Swedish Caledonides

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Abstract
U-Pb and Rb-Sr whole-rock isotopic data for an albite trondhjemite in northernmost Jämtland, Swedish Caledonides, are presented. Four zircon fractions, three of them almost concordant, define a discordia line with the upper intercept age 488±5 Ma. This age, which is considered to date the volcanic-subvolcanic complex, is consistent with the inferred stratigraphical age. The Rb-Sr system in the rock has been disturbed, probably during predeformational alteration (spilitization), and does not provide any chronological information.