ΤΗE PELAGONIAN NAPPE PILE IN NORTHERN GREECE AND FYROM. STRUCTURAL EVOLUTION DURING THE ALPINE OROGENY: A NEW APROACH

The geometry of kinematics and the deformation history of the Pelagonian nappe pile during the Alpine orogeny have been studied in Northern Greece and FYROM. Deformation was started in Middle-Late Jurassic time and was initially associated with ocean-floor subduction followed by ophiolites obduction, nappe stacking and duplication of the Pelagonian continent. The footwall Pelagonian segment from top to bottom was metamorphosed under greenschist to amphibolit facies conditions and a relative high pressure (T = 450o to 620o C and P = 12,5 to 8 kb). Blueschist facies metamorphic assemblages of Late Jurassic age are immediately developed between both hangingwall and footwall Pelagonian segments. Transgressive Late Jurassic-Early Cretaceous neritic limestones and clastic sediments on the top of the obducted ophiolites are maybe related to extension and basins formation simultaneously with the nappe stacking and metamorphism at the lower structural levels of the Pelagonian nappes. Contractional tectonics and nappe stacking continued during the Albian-Aptian time. Simultaneously retrogression and pressure decreasing taken place at the tectonic lower Pelagonian footwall segment. Low grade mylonitic shear zones, possible related to extension, are developed during Late Cretaceous time simultaneously with basins formation and sedimentation of neritic Late Cretaceous to Paleocene limestones and flysch. Intense shortening and imbrication under semi-ductile to brittle conditions occurred during Paleocene to Eocene time resulting the onset of the dome like formation of the footwall Pelagonian segment. The next stages of deformation from Oligocene to Quaternary are related to brittle extension and the final uplift and configuration of the Pelagonian nappe pile

The Mesohellenic trough and the Thrace Basin. Two Tertiary molassic Basins in Hellenides: do they really correlate?

Με βάση τη λιθοστρωματογραφία, την τεκτονική ανάλυση και τη γεωλογική χαρτο- γράφηση συγκρίθηκαν μεταξύ τους, οι μολασσικές λεκάνες της Θράκης (ThB) στη ΒΑ Ελλάδα (συμπεριλαμβάνονται οι Παλαιογενείς αποθέσεις της λεκάνης Αξιού) και της Μεσοελληνικής Αύλακας. Αμφότερες οι λεκάνες χαρακτηρίζονται από μια παχειά, μολασσικού-τύπου ιζηματογενή ακολουθία (3-5 km πάχος) Τριτογενούς ηλικίας, που καλύπτεται ασύμφωνα από Νεογενή και Τεταρτογενή ιζήματα. Η μολασσκή ιζηματογένεση αρχίζει σχεδόν ταυτόχρονα και στις δύο περιοχές κατά τη διάρκεια του Μέσου- Άνω Ηωκαίνου όμως σταματάει σε διαφορετικούς χρόνους, στο Μέσο-Άνω Μειόκαινο για τη ΜΗΤ και στο Άνω Ολιγόκαινο για τη ThB. Η ιζηματογένεση στη ThB συνοδεύτηκε επί πλέον από έναν ασβεσταλκαλικής και τοπικά σωσωνιτικής σύστασης μαγματισμό, Ηωκαινικής-Ολιγοκαινικής ηλικίας. Ερμηνεύσαμε τη ΜΗΤ ως μια πολυιστορική οριζόντιας μετατόπισης, piggy-back λεκάνη, που αποτέθηκε επάνω σε οφιόλιθους και στο Πελαγονικό κάλυμμα κατά την προς τα δυτικά τοποθέτησή τους πάνω στο κρύο πρίσμα επαύξησης των Ελληνίδων. Αντίθετα, η ThB αναπτύχθηκε ως μια Παλαιογενή λεκάνη, πάνω σε ρήγμα διαφυγής και στις γεωλογικές ενότητες των εσωτερικών Ελληνίδων, κατά τη διάρκεια της Ηωκαινικής-Ολιγοκαινικής έκτασης των Εσωτερικών Ελληνίδων. Ο σύγχρονος με την ιζηματογένεση μαγματισμός, πιθανόν, συνδέεται με τις ορογενετικές διαδικασίες υποβύθισης του ωκεανού της Πίνδου ή του Αξιού. Σε κάθε περίπτωση ΜΗΤ και ThB αναπτύχθηκαν κατά τη διάρκεια πλάγιας σύγκλισης της Απουλίας πλάκας και των Εσωτερικών Ελληνίδων.Based on lithostratigraphic and structural data, as well as geological mapping, the mollasic Thrace Basin (ThB) in NE Greece (including the Paleogene deposits of the Axios Basin) was compared with the Mesohellenic Trough (MHT) in NW Greece. Both basins are characterized by a thick sedimentary sequence of molassic-type strata (3-5km thickness) of Tertiary age, overlain unconformably by Miocene- Pliocene and Quaternary deposits. Molassic sedimentation started almost simultaneously in both areas during the Mid-Upper Eocene but it finished in different time, in the Mid-Upper Miocene for the MHT and the Upper Oligocene for the ThB, respectively. Sedimentation in ThB was also linked with an important calc-alkaline and locally shoshonitic magmatism of Eocene-Oligocene age. We interpreted the MHT as a polyhistory strike-slip and piggy-back basin, above westward-emplacing ophiolites and Pelagonian units on the cold Hellenic accretionary prism. In contrast to MHT, the ThB evolved as a Paleogene supra-detachment basin above the strongly extended during the Eocene-Oligocene Hellenic Hinterland. The syn-depositional magmatic products, linked possibly with subduction processes in Pindos or Axios ocean(s). In any case, MHT and ThB are related to inferred oblique convergence of the Apulia plate and the internal Hellenic units

Mineralogy and geochemical environment of formation of the Perama Hill high-sulfidation epithermal Au-Ag-Te-Se deposit, Petrota Graben, NE Greece

The Perama Hill deposit is a high-sulfidation Au-Ag-Te-Se epithermal system hosted in silicic- and argillic altered andesitic rocks and overlying sandstones, which were emplaced on the eastern margin of the Petrota graben, northeastern Greece. The deposit evolved from an early stage silica-pyrite rock and argillic alteration followed by the deposition of sulfide-, sulfosalt- and telluride-bearing quartz-barite veins and stockworks. Early ore formation is characterized by a high-sulfidation-type enargite-galena-bearing ore assemblage (consisting of enargite, watanabeite, Fe-free sphalerite, covellite, kesterite, bismuthinite, selenian bismuthinite, lillianite homologues, kawazulite-tetradymite, goldfieldite, and native gold), followed by the formation of an intermediate-sulfidation-type tennantite-bearing assemblage characterized by ferrian/zincian tennantite, tellurobismuthite, tetradymite, melonite, native tellurium, Au-Ag-tellurides (calaverite, krennerite, sylvanite, hessite, petzite, stützite), altaite and electrum. Quartz, barite, kaolinite, sericite and minor aluminum-phosphate-sulfate minerals are gangue minerals. Fluid inclusion data demonstrate that the ore system evolved from an initial high temperature (up to 330°C) and low salinity (up to 4.9 wt.% NaCl equiv.) fluid towards a cooler (200°C) and very low salinity (0.7 wt.% NaCl equiv.) hydrothermal fluid suggesting progressive cooling and dilution of the ore fluid. The ore minerals at Perama Hill reflect variable fS2 and fTe2 conditions during base and precious metal deposition. Early ore deposition took place at ~300°C, at logfS2 values between ≈-8.2 and -5.5, and logfTe2 from -11.8 and -7.8. Late ore deposition occurred at logfS2 = -11.8 to -9.8 and logfTe2 of ≈-9.2 and -7.8. These data and paragenetic studies indicate a shift towards higher logfTe2 and lower logfS2 and logfSe2 values for the mineralizing fluids with time. The kawazulite/tetradymitess-gold association at Perama Hill suggests that it formed from a sulfide melt in the Bi-Au-Se-Te system as Au was scavenged from the hydrothermal ore-forming fluid at elevated temperatures. The presence of tellurides, and Bi- and Sn-bearing minerals in the ore system is compatible with direct deposition of metals from the vapor phase of a degassing magmatic (porphyry) body. © 2011 Springer-Verlag