What the ca. 1.83Ga gedrite-cordierite schists in the crystalline basement of Lithuania tell us about the late Palaeoproterozoic accretion of the East European Craton

In the western East European Craton (EEC), southern Lithuania, a suite of fine-grained, thinly bedded rocks of unusual composition has been shown to have originally comprised intermediate and felsic volcanic rocks. They extruded at ca. 1.83Ga and were hydrothermally altered prior to metamorphism, which converted them into garnet-, gedrite-, anthophyllite-, staurolite- and cordierite-bearing schists. After the rocks have experienced a 630 degrees C and 7kbar metamorphism, they were uplifted to 15km (5kbar) probably at ca. 1.73Ga. They were reheated to 640 degrees C at ca. 1.50Ga (monazite age). The monazite age of ca. 1.50Ga is coeval with the emplacement of the neighboring 1.50Ga Anorthosite-Mangerite-Charnockite-Granite (AMCG) Mazury complex. The ca. 1.83Ga volcanic suites in Lithuania and northern Poland, together with the Oskarshamn-Jonkoping belt (OJB) in south-central Sweden, may belong to the same chain of volcanic island arcs, and thus provide information on the evolution of the entire western EEC. The ca. 1.50Ga metamorphic reworking and the replacement of the Mazury AMCG suite may have been triggered by the Danopolonian orogeny further west and, at a larger scale, accretion of the continental margin of Columbia.