Recognition of pre-Sveconorwegian cooling ages in the Eastern European Craton, Central Poland: new 40Ar–39Ar dating in the 1.8 Ga Kampinos Complex

In central Poland, the metamorphic Kampinos Complex underlies a thick sedimentary cover of the East European Craton. Previous K–Ar ages from drill cores of this complex were interpreted as indicative of an early Sveconorwegian (ca. 1.23 Ga) overprint. New laser step-wise 40Ar–39Ar dating of biotite from a 1.8 Ga granitic orthogneiss at the Okuniew borehole provides an age of 1306±16 Ma. This age brackets amphibolite facies deformation and metamorphism in the Kampinos Complex between 1.3 and 1.8 Ga, indicating pre-Sveconorwegian cooling of the complex.