Tectono-stratigraphy and evolution of the Mesozoic Pindos ophiolite and related units, northwestern Greece

Abstract

The northwest Pindos Mountains expose Mesozoic and Tertiary thrust sheets, which include the Jurassic Pindos ophiolite, composed of ultramafic and mafic oceanic crustal rocks. The tectono-stratigraphy of these units is: (i) mainly ultramafic ophiolitic thrust sheet and basal metamorphic sole (Dramala Complex and Loumnitsa Unit); (ii) Late Cretaceous platformal limestones (Orliakas Group); (iii) dismembered intrusive and extrusive ophiolitic rocks (Aspropotamos Complex): (iv) tectonic melange and olistostromes, dominated by Triassic-Jurassic volcanic and sedimtntary rocks (Avdella Melange); (v) coherent thrust sheets of Late Jurassic-Late Cretaceous deep-water sediments (Dio Dendra Group);(vi) Early Tertiary flysch (Pindos Flysch). Immobile trace-element studies indicate that Triassic and Jurassic extrusives of the volcanic-sedimentary melange formed mainly at within plate and/or mid-ocean ridge settings. By contrast, structurally overlying ophiolitic extrusives include boninitic volcanin and island arc tholeiites, of supra-subduction zone origin. Initial ophiolite displacement (c. 165 Ma) is recorded in metamorphic sole formation, including basal peridotite mylonite, amphibolites and greenschists. The sole rocks have MORB and WPB chemical affinities. In our favoured model, the Pindos ophiolite formed above a Mid-Jurassic westerly-dipping intra-oceanic subduction zone, accompanied by accretion to form melange, followed by cnllision and emplacement with the Pelagonian margin. Final suturing of the Pindos ocean, however did not take place until Early Tertiary times.

Polyphase evolution of Pelagonia (northern Greece) revealed by geological and fission-track data

“…Alternative reconstructions claim that these Vardar s.l. and Vourinos-Pindos ophiolites represent two oceans: the Pindos ophiolites obducted from the southwest and the Vardar ophiolites obducted from the northeast (Smith et al, 1979;Jones and Robertson, 1991;Clift and Dixon, 1998;Smith and Rassios, 2003). In any case, plate Fig.…”

Chromian Spinel Composition and Platinum-Group Element Mineralogy of Chromitites From the Milia Area, Pindos Ophiolite Complex, Greece

“…1) and corresponds to a piece of Middle to Upper Jurassic oceanic crust (Rassios & Smith 2000) that tectonically lies over the autochthonous Maastrichtian-Eocene Pindos flysch. The Pindos ophiolite complex is subdivided into four principal tectonic units: the Dramala complex, the Loumnitsa unit and the Aspropotamos complex, all structurally overlying the Avdella mélange (Jones & Robertson 1991). The Dramala unit consists of large masses of variably depleted harzburgite-dunite (>1000 km 2 ), which may host small bodies of chromitite (Pefki, Milia, Korydallos, etc., Fig.…”

“…The Loumnitsa unit represents the basal metamorphic sole of both Dramala and Aspropotamos complexes, comprising low-grade amphibolite-and greenschist-facies meta-igneous and metasedimentary rocks that have yielded 40 Ar-39 Ar ages of 169 ± 5 and 165 ± 3 Ma (Whitechurch & Parrot 1978, Spray & Roddick 1980. The Avdella mélange, about 1 km thick, contains blocks of various rock-types in a tectonized matrix and mappable thrust-sheets (Jones & Robertson 1991).…”

On the Metamorphic Modification of Cr-Spinel Compositions From the Ultrabasic Rocks of the Pindos Ophiolite Complex (Nw Greece)

“…1) and corresponds to a piece of MiddleUpper Jurassic oceanic crust (Rassios and Smith 2000), which tectonically lies over the autochthonous MaastrichtianEocene Pindos flysch. It can be subdivided into three principal tectonic units: the Dramala Complex, the Loumnitsa Unit and the Aspropotamos Complex, all structurally overlying the Avdella mélange (Jones and Robertson 1991). The Dramala unit is comprised of large, variably depleted harzburgite-dunite masses (> 1000 km 2 ) (EconomouEliopoulos and Vacondios 1995), which may host small chromitite bodies (Pefki, Milia, Korydallos etc.)…”

“…The Loumnitsa Unit represents the basal metamorphic sole of both the Dramala and Aspropotamos complexes, comprising lower amphibolite and greenschist facies meta-igneous and meta-sedimentary rocks that have yielded Ar-Ar ages of 169 ± 5 and 165 ± 3 Ma (Whitechurch andParrot 1978, Spray andRoddick 1980). The Avdella mélange is about 1 km thick and comprises blocks of various rock types in tectonised matrix and mappable thrust sheets (Jones and Robertson 1991).…”