Agpaitic magmatism at Norra Kärr? RbSr isotopic evidence |
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| Authors: | Alan B Blaxland |
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| Institution: | Alan B. Blaxland, Isotope Geology Division, Scottish Universities Research and Reactor Centre, East Kilbride, Glasgow G75 0QU, Scotland |
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| Abstract: | RbSr isotopic analyses of 10'whole-rock samples from the controversial peralkaline Norra Kärr complex of southern Sweden suggest an age (1580±62 m.y.) considerably older than had previously been anticipated, and indicate an initial 87Sr/86Sr ratio of 0.7072±0.0035 (errors at 2σ). The isotopic data are consistent with a primary magmatic origin for the Norra Kärr agpaites, but data from 8 mineral separates show that they have experienced at least one period of metamorphic disturbance since the original intrusion; the last episode of isotopic readjustment must have occurred after 1250 m.y. before present, and is attributed to the Sveconorwegian (Grenville) metamorphism. |
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