Age and significance of radiolarian sediments within basic extrusives of the marginal basin Guevgueli Ophiolite (northern Greece)

Abstract

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).

Middle Jurassic age of basalts and the post-obduction sedimentary sequence in the Guevgueli Ophiolite Complex (Republic of Macedonia)

“…The newly obtained radiolarian age is significantly older than the previously determined Oxfordian age which was also based on radiolarians (Danelian et al 1996). The terrigenous admixtures in the calcareous silt turbidites from which Danelian et al (1996) extracted radiolarians may suggest that in the Oxfordian, the Guevgueli backarc basin was already in the closing stage.…”

“…The Guevgueli Ophiolite Complex is located in the border region of the Republic of Macedonia and Greece and is one of the largest ophiolite complexes in the the village of Platania in northern Greece where Oxfordian radiolarians were determined (Danelian et al 1996). Our study at Demir Kapija (Republic of Macedonia) documents the existence of older, i.e., Bathonian-Callovian, radiolarian cherts as the direct sedimentary cover of basalts.…”

“…The Guevgueli ophiolitic sequence extends over 500 km 2 and consists of: (1) intrusive complex: ultramafic cumulates, gabbros, Fe-gabbros, Fe-diorites; (2) sill complex (various lithotypes showing calc-alkaline affinity); (3) volcanic sequence (back-arc basalts, calc-alkaline basalts, basaltic andesites, andesites, dacites and rhyolites); and (4) radiolarian cherts (Bébien et al 1986;Danelian et al 1996;Saccani et al 2008Saccani et al , 2011Božović et al 2013).…”

“…Danelian et al (1996) reported an Oxfordian age of a radiolarian assemblage found in calcareous silt turbidites at a single locality in northern Greece. These turbidites contain admixtures of terrigenous material indicating that the ophiolite formed in a near-continental setting (Danelian et al 1996).…”

East Vardar Ophiolites Revisited: A Brief Synthesis of Geology and Geochemical Data

“…Spray et al [55] reported 40 Ar/ 39 K ages on biotite and kaersutite mineral separates from gabbros and diorites between 149 ± 3 Ma and 163 ± 3 Ma. Danelian et al [56] studied radiolarians from the overstep sequence and determined Oxfordian age (161.2-155.7 Ma). Zachariadis [38] studied zircons from plagiogranite found in gabbros of the Skra complex and reported an intrusion age of 166.6 ± 1.8 Ma.…”