The paper describes preliminary results from the 120sqkm Volvi mafic complex within the Greek Serbo-Macedonian Massif. We conclude from published information and isotopic ages that the central and eastern part of the Massif (basement and Triassic/Jurassic cover) were affected by an amphibolite-facies regional metamorphic and deformational event in the Late Jurassic-Early Cretaceous. Delayed uplift from this same event may explain Tertiary ages from Kerdilion migmatites. The Volvi complex may thus be A: pre-Mesozoic 'basement', or B: an in situ Mesozoic rift complex or C: a Mesozoic collisional suture remnant. Field, microprobe and XRF data appear to fit model B best. Though deformed, the complex has recognisable 100% sheeted-dyke tracts and substantial areas of undeformed gabbro at lower structural levels. Deformation began before the end of magmatic activity: late sheets of pegmatic gabbro cut deformed dykes; late dykes cut sheared gabbro. Assemblages are of high-grade amphibolite facies and give garnet-hornblende temperatures of 750~ significantly higher than inferred for staurolite-garnet schists outside the complex. Geochemically, the basaltic rocks show LIL enrichment and are intermediate between 'alkalic' and 'above-subduction-zone' in character. The complex may relate to Mesozoic rift-basins identified in E. Serbia, but is not thought to be a Palaeotethyan remnant.

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Well-preserved Radiolaria have been discovered in calcareous silt turbidites and mudstones intercalated with basic extrusives of the Guevgueli Ophiolite, northern Greece. The mudstones contain terrigenous silt, probably derived from adjacent continental basement of the Serbo-Macedonian and/or Paikon units. Volcanic quartz and rare volcanic glass were probably derived from an active continental margin arc (Paikon volcanic arc) to the west. The radiolarian sediments were deposited within fault-controlled hollows in the ophiolitic extrusives, and then covered by massive and pillowed extrusives. The radiolarian assemblage is indicative of an early Late Jurassic (Oxfordian) age, which therefore dates the genesis of the Guevgueli Ophiolite. Our data are consistent with the age of the intrusive Late Jurassic Fanos Granite, believed to be contemporaneous with the Guevgueli Ophiolite. In general, the Guevgueli and related ophiolites of northern Greece are thought to have formed within a transtensional intra-continental marginal basin, generated in response to oblique eastward subduction of older Tethyan oceanic crust (Almopias ocean).

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