The metamorphic Precambrian basement in the western part of the East European Craton (EEC) has previously been considered to be Archaean in age. Recent U-Pb and Sm-Nd studies in Estonia, Poland and Belarus have, however, revealed a vast area of Palaeoproterozoic crust. In order to survey the crustal ages in Latvia and Lithuania, and to establish the relationships of these territories with adjacent regions of the EEC, particularly those exposed in the Baltic and Ukrainian Shields, three new U-Pb zircon age determinations and 21 epsilon (Nd) whole-rock analyses were performed. In Latvia, a granodiorite yielded an intrusion age of 1816 +/-5 Ma and a felsic metavolcanic rock an age of metamorphism at 1810 +/-2 Ma, with indications of a minimum protolith age of ca. 1840 Ma. In Lithuania, a metasediment yielded a multigrain U-Pb zircon age of 2302(-100)(+200) Ma, very similar to multigrain zircon ages of Svecofennian metasediments in Scandinavia. The epsilon (Nd) survey of various rock types demonstrated relatively little variation, with depleted-mantle model ages between 2.4 and 1.9 Ga for the igneous rocks and between 2.5 and 2.0 Ga for the metasedimentary ones. This indicates only minor influence of Archaean crust but close isotopic similarity to rocks of the same lithologies in the Svecofennian Domain of Sweden and Finland. Together with recent U-Pb and Sm-Nd results from other parts of the EEC, the present study suggests a close relationship between the Palaeoproterozoic crust in Estonia, western Latvia and western Lithuania, and the southern part of the Svecofennian Domain within the Baltic Shield. All these regions have U-Pb zircon ages of rock formation between 1.90 and 1.82 Ga, and were subjected to a major metamorphic event between 1.83 and 1.81 Ga. These ages contrast with ages between 2.0 and 1.9 Ga for similar rocks farther cast and southeast, i.e. closer to the Ukrainian Shield. Altogether, the current results reaffirm an accretionary character of the Palaeoproterozoic crust in the western part of the EEC, as previously concluded by other investigators. In addition, there is basis to suggest that the crust in western Latvia and Lithuania was formed during the late stages of the Svecofennian orogeny and thus can be correlated with juvenile late Svecofennian crust in southeastern Sweden. (C) 2001 Elsevier Science B.V. All rights reserved.
