The origin of a suite of ultrabasic and basic rocks from the Letovice crystalline complex in the eastern part of the Bohemian massif, Czechoslovakia, is discussed on the basis of new geological and geochemical data. Strongly serpentinised spinel peridotites, plagioclase peridotites and pyroxenites, together with metagabbros, amphibolites and minor dykes of metadolerite, make up about 70% of the complex; metasediments, mainly mica schists, make up the remaining 30%. The ultramafic and mafic rocks constitute parts of a dismembered ophiolite considered to have been formed in the Cadomian episode. They show effects of polyphase deformation and were variously metamorphosed under conditions of greenschist to garnet amphibolite fades at 400–600°C and 2–5 kb. Geochemical features of the ultrabasic suite are similar to those of other ophiolite complexes, such as those of Bay of Islands, Oman, Papua, Pindos, Sarmiento and Troodos and are likely to be products of a marginal sea environment.
