No description available.

No description available.

Regional mapping of the Livadi area, lying west of Mt. Olympos in N.E. Greece, has revealed that the present tectonic juxtaposition of the Livadi Mafic - Ultramafic Complex and the metamorphic lithologies of the Pelagonian basement, results from an involved history of deformation and metamorphism. The Pelagonian basement comprises a sequence of psammitic and pelitic clastics, frequently of arkosic composition, and probably of Palaeozoic age. Granitic and, less commonly, amphibolitic intrusives are widespread, and the largest, the Livadi Granite, has been designated an Upper Carboniferous age by analogy with the Kataphygion Granite to the north (Yarwood, 1976). This igneo-sedimentary sequence is overlain by neritic carbonates of presumed Triassic-Jurassic age (Godfriaux, 1968). During Lower Cretaceous time, these lithologies were subjected to an upper greenschist-lower amphibolite grade metamorphism which resulted in the paragenesis of biotite, phengite, epidote, garnet hornblende, oligoclase and albite. It was associated with flattening, and the development of mylonitic zones and a strong L-S tectonite fabric. The shape of clastic pebbles deformed at this time indicate that the dominant strain was one of flattening, but that the greatest amount of finite distortional strain is located within the shear zones, where the deformation is constrictional. Subsequent to this event, but prior to the emplacement of the Livadi Mafic - Ultramafic Complex, deformation of the L-S tectonite fabric occurred about major fold axes oriented sequentially NE-SW and NW-SE, and resulted in the production of kilometre-scale interference patterns. Estimates of shortening across folds of the earlier phase vary between 40% and 45%. Fabrics associated with these fold periods are only locally important. The broadly cumulate stratigraphy of the Livadi Mafic - Ultramafic Complex comprises serpentinite and metamorphosed dunite, harzburgite, lherzolite and gabbro, which tectonically overlie the Pelagonian metamorphics in a number of small thrust klippen. The thrust surface that originally connected these mafic-ultramafic 'outliers' is essentially horizontal and truncates the above described structures of the Pelagonian basement. The history of the Livadi Mafic - Ultramafic Complex prior to this final emplacement is similar to that of the underlying metamorphics. An early period of isochemical serpentinization that was associated with an initial emplacement phase, occurred at the expense of most primary minerals. Continued tectonic movement of the Complex led to the development of a major overturned structure and was followed by a period of metamorphism of similar grade, and probably similar age, to that described above. Parageneses included ferrichromite, metamorphic olivine, talc and tremolite in the ultramafics, and epidote group minerals, tremolite, oligoclase, albite and quartz in the gabbros. Emplacement of the Livadi Complex into its present position was associated with cataclastic deformation and non-isochemical serpentinization that took place under lower greenschist conditions as evidenced by the paragenesis of low-Al2O3 tremolite, chlorite, and muscovite in the gabbros. A retrograde metamorphism of similar grade is also present in the underlying metamorphics, and the two events are believed to be associated. The orientation of linear features developed during emplacement, together with regional considerations, suggest that the Complex reached its present position from the SW., while a lower Tertiary age may be indicated by analogies with the Olympos thrust to the east (Barton, 1975a). Subsequent to its emplacement, the Livadi Mafic - Ultramafic Complex and its metamorphic basement were tectonically overridden by the Pelagonian lithologies of the Pieria allochthon along the E-W Mavroneri thrust. The orientation of linear structures, thrust surfaces, asymmetrical folds and imbricate slices associated with this movement are consistent with emplacement towards the south. Petrological and mineralogical data, together with regional considerations, suggest an ophiolitic origin for the Complex, and may imply its derivation from the Mesozoic Othris ocean.

- / -

Cette thèse est centrée sur la ceinture orogénique Attico-Cycladique formée durant l'orogénèse Alpine. Par une approche multi-méthodes et multi-échelles combinant géologie structurale, pétrographie, thermobarométrie des assemblages minéraux, géochimie élémentaire et isotopique, et données PVTX des inclusions fluides associées, ce travail vise à caractériser et comprendre les relations entre circulations fluides, interactions fluides/roches, déformation, et mobilisation-transport-dépôt des métaux. Les marbres et schistes de la péninsule du Lavrion et de l'île d'Eubée témoignent d'une évolution orogénique complexe marquée par une phase d'enfouissement à l'Eocène suivie par deux phases d'exhumation successives syn-et post-orogéniques. Les minéralisations de type Cu-Pb-Zn-Fe-Ag de la région du Lavrion sont synchrones de l’activation du détachement post-orogénique et de la mise en place de plutons de granodiorite. Leurs positions structurales témoignent d’un piégeage depuis un régime de déformation ductile jusqu'à fragile. Les minéralisations mises en place durant le régime de déformation ductile à ductile-fragile (skarn et remplacement de carbonate) sont associées à la décarbonatation des niveaux de marbres et à la circulation des fluides magmatiques. L'exhumation progressive de la racine orogénique se traduit par la transition des roches depuis une déformation ductile vers un régime fragile associé à l’ouverture du système aux fluides de surface et notamment aux fluides météoriques. Cette circulation est responsable d’une remobilisation des métaux des minéralisations primaires permettant alors une seconde phase de précipitation dans un régime cassant (veines épithermales) / This thesis is focused on the Attico-Cycladic orogenic wedge formed during the Alpine orogeny. From a multi-method and multi-scale approach using structural geology, petrography, mineral thermobarometry, element and isotope geochemistry, and PVTX data of associated fluid inclusions, this study deciphers the relationships between fluid circulation, fluid-rock interactions and mobilisation-transport-deposits of metals. Marbles and schists from the Evia Island and the Lavrion peninsula testify to a complex orogenic history marked by an Eocene burial phase followed by syn- and post-orogenic exhumation. Cu-Pb-Zn-Fe-Ag mineralisations from the Lavrion area are synchronous with the formation of the low-angle post-orogenic detachment and the emplacement of granodioritic magmas. The structural position of the deposits attests of an emplacement during ductile to brittle deformation conditions. Deposits associated with ductile to ductile-brittle deformation (skarn, carbonate replacement) are related to a marble decarbonation and magmatic fluid circulation. The progressive exhumation of the orogenic wedge allows the transition toward brittle conditions and opens the system to surficial meteoritic fluids. This meteoritic fluid circulation is responsible to remobilisation of metals from primary deposits allowing thus a second phase of deposition in a pure brittle deformation (epithermal veins)