The RbSr age of the Hästefjorden granite and its bearing on the Precambrian evolution of southwestern Sweden |
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Authors: | Eric Welin Roland Gorbatschev |
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Institution: | 1. Department of Mineralogy, Swedish Museum of Natural History, Stockholm Sweden;2. Department of Mineralogy and Petrology, Institute of Geology, Lund Sweden |
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Abstract: | On the basis of a seven-point isochron, the RbSr whole-rock age of the Hästefjorden granite in southwestern Sweden is 1240 ± 30 Ma using a decay constant of 1.39·10?11 yr?1. The initial 87Sr/86Sr ratio is 0.712. This dating sets a lower limit for the beginning of the Dalslandian (Dal sequence) sedimentation and supports suggestions of a chronological diversity of the so-called Gothian Åmål—Kroppefjäll granite complex in western Sweden. It also invalidates correlation of the Åmål—Kroppefjäll complex as a whole with the Småland plutonics of southeastern Sweden. This proves that rocks previously considered as being formed during the “Gothian Cycle” are very different in age. |
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