Apatite-rich hornblende clinopyroxenite from the Lillebukt Alkaline Complex, Stjernøy, has yielded Sm-Nd and Rb-Sr internal isochron ages of 540 ± 39 Ma (MSWD = 0.21) and 521 ± 22 Ma (MSWD = 0.00) respectively, interpreted as intrusion ages. ?NdtCHUR of +4.00 ± 0.55 and ?SrtUR of -11.21 ± 0.34 suggest a moderately depleted mantle source. The metagabbro host, which was deformed before emplacement of the horn blende pyroxenite dykes, gives Sm-Nd and Rb-Sr internal isochron ages of 517 ± 61 Ma (MSWD = 1.64) and 534 ± 8 Ma (MSWD = 4.60) respectively. Both probably date metamorphic recrystallization of the host metagabbro that took place before the initiation of the alkaline magmatism.
R. Cadow, Geologisk institutt, avd. A, Allégt. 41, 5007 Bergen - Universitetet, Norway.