Anders Scherstén

Upper-intercept U-Pb ages (TIMS) of two non-foliated I-type granites are 1887 ± 20 Ma (part of a granodiorite-granite sequence) and 1881 ± 2 Ma (leucogranite with transitions into pegmatite). A non-foliated S-granite, which according to field observations, is younger than the two I-granites, occurs within the same composite pluton. Zircons of this granite are heterogeneous and contain abundant cores. A ²⁰⁷Pb/²⁰⁶Pb–²³⁸U/²⁰⁶Pb concordia age of 1786 ± 23 Ma (Tera-Wasserburg diagram) using the LA-ICP method is consistent with the reported age of nearby LCT-pegmatites. The age range of non-foliated Svecofennian granite intrusions in this part of the Baltic Shield is thus of the order of 0.09 (Formula presented.) 10³ Ma. A major part of this pluton is made up of several intrusions of S-type granite. Mapping, γ-radiation maps, and published chemical analyses give evidence of differences among these intrusions. No data exist on their age span.