Calculating pressure with elastic geobarometry: A comparison of different elastic solutions with application to a calc-silicate gneiss from the Rhodope Metamorphic Province

Abstract Raman elastic geobarometry has increasingly been used complementary to metamorphic phase equilibria to estimate the conditions of recrystallization in metamorphic rocks. The procedure of applying Raman elastic barometry to host-inclusion mineral systems requires several steps that involve various assumptions. One of the most essential assumptions is that the mineral host-inclusion system behaves in an elastic and reversible manner. We discuss the discrepant results obtained by different authors employing different analytical solutions for elasticity and explore the assumptions lying behind each method. Furthermore, we evaluate numerically linear and non-linear elastic solutions and…

Provenance of sediments during subduction of Palaeotethys: Detrital zircon ages and olistolith analysis in Palaeozoic sediments from Chios Island, Greece

Abstract Detrital zircon geochronology and analysis of fossiliferous olistoliths from Chios Island, Greece, are used here to constrain terrane accretion processes and the provenance of crustal sources for sediments during the subduction of (a branch of) the Palaeotethys Ocean. U/Pb ages obtained by ion microprobe (SHRIMP-II) analyses of detrital zircons from a Carboniferous greywacke belonging to the tectonostratigraphic Lower Unit of Chios gave major age groups of 2150–1890 Ma, 640–540 Ma, 505–475 Ma and 365–322 Ma. Detrital zircons from a Permian–Triassic sandstone yielded prominent age clusters of 2200–1840 Ma, 1100–910 Ma, 625–560 Ma and 385–370 Ma. The lack of zircon ages between 1.8 a…

Geochemistry, petrogenesis and tectonic setting of the Samothraki mafic suite, NE Greece: Trace-element, isotopic and zircon age constraints

Abstract The Samothraki mafic suite in the north-eastern Aegean Sea, Greece, is an ‘in situ’ magmatic complex comprising gabbros, sparse dykes and basalt flows and pillows cut by late dolerite dykes. We have determined the age of the complex by SHRIMP zircon geochronology of a gabbro as 159.9 ± 4.5 Ma (i.e. Oxfordian; early Late Jurassic), which precludes any correlation with the so-called Lesvos ophiolite further south (253.1 ± 5.6 Ma; Latest Permian). Six distinct, hitherto unrecognised, geochemical groups have been identified among the basalts and dolerites of the Samothraki mafic suite on the basis of trace-element and Nd–Sr isotopic characteristics. All groups show the presence of an e…

PETROLOGY, GEOCHEMISTRY AND GEOTECTONIC SETTING OF THE TITAROS OPHIOLITE AND ASSOCIATED PELAGONIAN BASEMENT ROCKS IN THE AREA NW OF MT. OLYMPOS, GREECE

To οφιολιθικό σύμπλεγμα του όρους Τίταρος στην περιοχή ΒΔ του Ολύμπου βρίσκεται επωθημένο σε Περμο-Αιθανθρακοφόρους γρανιτικούς ορθογνεύσιους και άγνωστης ηλικίας αμφιβολίτες στο ανατολικό περιθώριο της Πελαγονικής μάζας. Αποτελείται από μανδυακό περιδοτίτη χαρτσβουργιτικής σύστασης με κατά τόπους εμφανίσεις χρωμίτη και ένα καλά ανεπτυγμένο μαγματικό θάλαμο με κυκλικές ενότητες σωρειτικών πετρωμάτων δουνίτη-λερζόλιθου-βερλίτη-πυροξενίτη που μεταβαίνουν σε συμπαγείς γάββρους με φωλιές πλαγιογρανιτών και διαβασικές φλέβες στα ανώτερα τμήματα τους. Χημικές αναλύσεις ορυκτών και ολικού πετρώματος φανερώνουν συνθήκες γένεσης του οφιόλιθου σε ένα καθαρά ωκεάνειο περιβάλλον επάνω από μία ζώνη κατά…

Mineral chemical and geochronological constraints on the age and provenance of the eastern Circum-Rhodope Belt low-grade metasedimentary rocks, NE Greece

Abstract In north-eastern Greece the mid-greenschist facies Makri Unit and the anchizonal Melia Formation belong to the eastern Circum-Rhodope Belt that forms the uppermost tectonostratigraphic unit of the Rhodope metamorphic nappe pile. The two metasedimentary successions had different source areas, although they now lie in close proximity in the Rhodope Massif. The U–Pb isotopic ages of detrital zircons from a metasandstone of the Makri Unit analysed using LA–SF–ICP–MS and SHRIMP-II gave age clusters at ca. 310–290 Ma and at ca. 240 Ma for magmatic zircons, which may have been derived from Carboniferous–Permian basement rocks of the Thracia Terrane (Lower Tectonic Unit of the Rhodope Mass…

Triassic rift-related meta-granites in the Internal Hellenides, Greece

AbstractThe Serbo-Macedonian Massif is a basement complex in the Internal Hellenides of northern Greece, situated between the Vardar Zone to the west and the Rhodope Massif to the east. The Serbo-Macedonian Massif comprises several distinct basement units interpreted as terranes, the largest of which is the Gondwana-derived Vertiskos Terrane in the northwestern and central parts of the massif. A series of leucocratic meta-granites intrude the Silurian orthogneiss basement of the Vertiskos Terrane. No similar granites are found in any of the other units of the Internal Hellenides. The meta-granites have a pronounced crustal within-plate signature which is visible in lithology, major- and tra…

Late palaeozoic magmatism in the basement rocks Southwest of Mt. Olympos, Central Pelagonian zone, Greece: Remnants of a permo-carboniferous magmatic arc

We dated basement rocks from several localities southwest of Mt. Olympos, as well as from a locality near the top of the mountain using the single zircon Pb/Pb evaporation technique. For the samples southwest of the mountain, the ages obtained range from ca. 280 to 290 Ma, with only a few zircon grains being around 300 Ma. By contrast, the sample from near the top of the mountain appears to be slightly younger, with ca. 270 Ma. These ages imply that the granitoids crystallized during Late Carboniferous - Early Permian times, and are therefore younger than the basement gneisses of other regions of the Pelagonian zone, which yielded zircon ages of around 300 Ma (e.g. Yarwood & Aftalion 19…

Serbo-Macedonian revisited: A Silurian basement terrane from northern Gondwana in the Internal Hellenides, Greece

Abstract New geochronological and geochemical data on basement orthogneisses from the Vertiskos Unit of the Serbo-Macedonian Massif (SMM), Internal Hellenides, northern Greece, are used in order to constrain the pre-Alpine tectonic history of the basement units in the metamorphic hinterland of the Hellenides. The prevailing rock types in the Vertiskos crystalline basement are coarse-grained biotite augengneisses with subordinate leucocratic muscovite gneisses and two-mica gneisses. Zircon Pb–Pb and U–Pb ages on 20 samples range from 425.9 ± 4.2 Ma to 443.4 ± 5.5 Ma with a mean of 432.2 ± 3.2 Ma and are interpreted as primary crystallisation ages of the basement granites on the basis of the …

Pliocene tourmaline rhyolite dykes from Ikaria Island in the Aegean back-arc region: geodynamic implications

Very rare rhyolite dykes cross-cutting a Miocene I-type biotite-granite were discovered on Ikaria Island in the Aegean back-arc region. Their intrusion postdates exhumation of the granite to brittle crust at about 6.0-3.6 Ma; hence a Pliocene age is inferred. Petrological, geochemical and isotopic arguments indicate an origin through melting of crustal lithologies (tourmaline greywackes/semipelites) with no detectable contribution from asthenospheric sources. Strontium isotope ratios are relatively low unlike values for sediments entering the Hellenic trench but similar to those for certain Miocene Cycladic I-type granites and low-Rb Permo-Carboniferous Cycladic basement acid orthogneisses.…

Geochemical constraints on the provenance and depositional setting of sedimentary rocks from the islands of Chios, Inousses and Psara, Aegean Sea, Greece: implications for the evolution of Palaeotethys

The provenance and depositional setting of Late Palaeozoic and Early Mesozoic clastic sediments from the eastern Aegean archipelago are examined here for the first time using whole-rock geochemistry and composition of detrital chrome spinel. Major- and trace-element data for Late Palaeozoic and Permo-Triassic clastic sediments from the Lower and Upper Units of Chios are compatible with an acidic to intermediate source, minor input of (ultra)mafic detritus and recycling of older sedimentary components. Chondrite-normalized REE profiles are uniform with light REE enrichments (La N /Yb N c . 7.7), negative Eu anomalies (Eu/Eu* c . 0.67) and flat heavy REE patterns (Gd N /Yb N c . 1.5), indicat…

Late Proterozoic and Silurian basement units within the Serbo-Macedonian Massif, northern Greece: the significance of terrane accretion in the Hellenides

The oldest rocks of Greece: first evidence for a Precambrian terrane within the Pelagonian Zone

The Pelagonian Zone in Greece represents the westernmost belt of the Hellenide hinterland (Internal Hellenides). Previous geochronological studies of basement rocks from the Pelagonian Zone have systematically yielded Permo-Carboniferous ages. In this study we demonstrate, for the first time, the existence of a Precambrian crustal unit within the crystalline basement of the Pelagonian Zone. The U–Pb single-zircon and SHRIMP ages of these orthogneisses vary from 699 ± 7 Ma to 713 ± 18 Ma, which identify them as the oldest rocks in Greece. These Late Proterozoic rocks, which today occupy an area of c. 20 × 100 km, are significantly different from the neighbouring rocks of the Pelagonian Zone.…

Age and origin of granitic rocks of the eastern Vardar Zone, Greece: new constraints on the evolution of the Internal Hellenides

The Vardar Zone is an integral part of the Internal Hellenides and has long been regarded as an ophiolite-decorated suture zone separating two distinct continental blocks, namely the Pelagonian Zone to the west and the Serbo-Macedonian Massif to the east. Several bodies of granites, gneisses and volcanic rocks are associated with the ophiolitic rocks and can provide additional constraints on the evolution of the suture. Single-zircon and monazite dating of felsic rocks yields accurate ages for the processes of accretion of the suture. The igneous formation ages obtained range from 155 to 164 Ma, suggesting an important magmatic phase in the Late Jurassic. The chemical and isotopic compositi…

Rutile chemistry and thermometry as provenance indicator: An example from Chios Island, Greece

Abstract In the present study we focused on detrital rutile separated from 12 psammitic samples that belong to three different sedimentary successions (Carboniferous, Permo-Carboniferous, Permo-Triassic) occurring on Chios Island, Greece. The Ti, Cr, Al, Fe, Nb, Zr, Si, and V contents of the rutiles were obtained by electron-microprobe analyses to trace their provenance. The Cr and Nb concentrations of the analysed rutile grains show a wide range and indicate that this mineral in the Carboniferous succession is mainly derived from metamafic rocks, whereas in the Permo-Carboniferous and Permo-Triassic successions stem from a metapelitic source. The calculated formation temperatures using the…

Geochemistry, provenance and stratigraphic age of metasedimentary rocks from the eastern Vardar suture zone, northern Greece

Abstract Uppermost Palaeozoic and Mesozoic sediments from the Vardar suture zone in northern Greece record a cycle of Neotethyan oceanic basin opening and closure and their analysis places tight constraints on the geotectonic evolution of the area. The oldest post-Carboniferous sedimentary unit in the study area is the Examili Formation, which comprises mainly metaarkoses and metaquartzites, and was deposited in an intracontinental rift-related sedimentary basin in proximity to the Vertiskos Terrane during the Permian–Triassic. The Melissochori Formation (former Svoula flysch) comprises predominantly metasandstones with significant carbonate content and was deposited in front of a Carbonife…

Geochemical constraints on the provenance and depositional setting of sedimentary rocks from the islands of Chios, Inousses and Psara, Aegean Sea, Greece: implications for the evolution of Palaeotethys

The provenance and depositional setting of Late Palaeozoic and Early Mesozoic clastic sediments from the eastern Aegean archipelago are examined here for the first time using whole-rock geochemistry and composition of detrital chrome spinel. Major- and trace-element data for Late Palaeozoic and Permo-Triassic clastic sediments from the Lower and Upper Units of Chios are compatible with an acidic to intermediate source, minor input of (ultra)mafic detritus and recycling of older sedimentary components. Chondrite-normalized REE profiles are uniform with light REE enrichments (LaN/YbN c. 7.7), negative Eu anomalies (Eu/Eu* c. 0.67) and flat heavy REE patterns (GdN/YbN c. 1.5), indicating an up…