Grain size distribution, clay mineralogy and chemistry of bottom sediments from the outer Thermaikos Gulf, Aegean Sea, Greece

The Thermaikos Gulf constitutes the NW part of the North Aegean Sea and is limited eastward from the Chalkidiki Peninsula and westward from the Pieria Prefecture. Its plateau covers an area of 3,500 km2. The mechanisms responsible for the grain size distribution into the Gulf, the clay mineralogy and the chemistry of some bottom sediments from the outer Thermaikos Gulf, are examined. Source mixing during transportation, flocculation, differential settling processes and organic matter appear to be the main mechanisms for the distribution of clay minerals in shallow waters. All grain size fractions studied present a wide range of values confirming the extreme variations of the discharged load and the variability in marine processes. Plagioclases predominate over K-feldspars, while quartz is the most abundant mineral present. In addition, micas, chlorites, amphiboles and pyroxenes exist as primary and/or accessory minerals in all samples. Among clay minerals, illite predominates over smectite and smectite over chlorite (+ kaolinite). The ordered interstratified phase of I/S, with 30-35% S layers, is present in the 2-0.25µm fraction. The randomly interstratified phase of I/S, with 50% S layers, is present in the <0.25& micro; m fraction. On average the clay mineral content of the studied samples is: 48% I, 23% S, 17% Ch (+K) and 12% others for the 2-0.25µm fraction and 50% I, 30% S and 20% Ch (+K) for the <0.25 µm fraction. All these minerals are the weathering products of the rocks from the drainage basins of the rivers flowing into the Gulf, as well as of the Neogene and Quaternary unconsolidated sediments of the surrounding coasts. The terrigenous input, the water mass circulation and, to a lesser extent, the quality of the discharged material and the differential settling of grains, control the grain size distribution within the outer Thermaikos Gulf. The chemical composition of the analysed samples is generally in agreement with their mineral composition and signifies their terrigenous origin presenting discretely clastic character

Geology and geochemistry of the Eocene zeolite bearing volcaniclastic sediments of Metaxades, Thrace, Greece

The Eocene zeolite-bearing volcaniclastic sediments (Ca-rich clinoptilolite 51 % on average) of Metaxades, Thrace, Greece, are studied in terms of geology and chemical composition. The alternating formations along a vertical profile in the Metaxades main quarry face are: Discrete horizons of zeolite-bearing volcaniclastic tuffs, zeolite-bearing volcaniclastic tuffs including pebbles, zeolite-bearing volcaniclastic tuffs including thin silica-rich layers, and a calc-clayey horizon. A positive correlation is observed between MgO and CaO in the volcaniclastic tuffs including silica-rich layers. Sr, Rb and Ba are the most abundant trace elements in alllayers; among them, Sr is found to correlate positively with zeolite. The enrichment of sorne trace elements is mainly attributed to mineral abundances, mineral chemistry or leaching processes. The zeolite-bearing volcaniclastic sediments of Metaxades represent an inhomogeneous sequence, which was deposited in a shallow marine environment under turbulent to quiet sedimentary conditions.Los sedimentos eocenos volcanoclásticos con zeolita (51% de media de clinoptilolita rica en Ca) de Metaxades, Tracia, Grecia, se estudian desde el punto de vista geológico y de su composición química. Las formaciones alternantes que se pueden observar en un corte vertical en la cantera principal de Metaxades son: horizontes aislados de tufos volcanoclásticos con zeolita y con delgadas capas ricas en sílice, y un horizonte calco-arcilloso. Se observa una correlación positiva entre MgO y CaO en los tufss volcanoclásticos que presentan capas ricas en sílice. El Sr, el Rb y el Ba son los elementos traza más abundantes en todos los horizontes. Entre ellos, el Sr presenta una correlación positiva con la zeolita. El enriquecimiento en algunos elementos traza se atribuye esencialmente a las abundancias de los minerales, la química mineral, o a fenómenos de lixivinción. Los sedimentos volcanoclásticos con zeolita de Metaxades representan una secuencia inhomogénea, que fue depositada en un ambiente marino somero, bajo condiciones desde turbulentas hasta tranquilas

Distribution of surficial sediments in the Southern Evoikos and Petalioi Gulfs, Greece

A series of 123 surficial sediment samples from the Southern Evoikos and Petalioi Gulfs was studied for grain-size properties, carbonate content and mineralogical composition. Distribution of the sediments revealed two sedimentary provinces. The first concerns the Southern Evoikos Gulf, characterised by silty sediments with relatively low carbonate content. Quartz, feldspars, micas, clay and carbonate minerals are the major mineralogical components of the sediments. These sediments are the result of the Asopos River supply during Holocene and they contribute to the formation of smooth bottom morphology. The second province concerns the Petalioi Gulf (Northern and Southern), where the surficial sediments are mainly sandy and characterised by very high carbonate content. Their mineralogical composition reflects the lithology of the drainage basin. Since the modern terrigenous solid supply is limited, these sediments are not considered as products of recent sedimentation, but older deposits (relict sands). Their presence at such depths is justified by sea-level fluctuations and their preservation is due to the low sedimentation rate in the Petalioi Gulf, in combination with the strong hydrodynamic status of the area

SUITABILITY OF THE KOZANI 'S AREA (NW MACEDONIA, GREECE) CARBONATE ROCKS FOR THE CEMENT INDUSTRY AND AS AGGREGATES IN CONSTRUCTIONS

The suitability of Kozani's broader area carbonate rocks for use in cement production and as aggregates, is studied in terms of their mineralogical, chemical and mechanical characteristics. The studied carbonate rocks belong to the Pelagonian zone and are represented mainly by pure limestones with subordinate dolomites and dolomitic limestones. Examination concerning their insoluble residue, organic matter and milling behavior, together with their mineralogical and chemical composition showed that all carbonate formations of Kozani's broader area, except the dolomitic ones, fulfill the requirements for use as raw material in the cement industry and all the carbonate formations meet the specifications for their use as aggregates in various constructions

Unconventional hydrocarbon resources of Greece

Intensive exploration of probable conventional hydrocarbon reservoirs in Greece is taking place, through the interpretation of seismic profiles and of abundant surface geological data. The unconventional hydrocarbon potential of the country is unknown, as detailed investigations are lacking. The most important rock formations which may contain shale gas are found in the land and offshore basins of northeastern, north-central, and western Greece. A re-evaluation of the data from all boreholes is needed, on the basis of new information, with the aim of identifying possible reserves of unconventional hydrocarbons retained in highly compacted fine-grained strata. Methane hydrates have been detected in the submarine Anaximander Mountains, east of Rhodes Island. They cover an area of about 46 km2 and the volume of methane is estimated at 2.6–6.4 trillion m3. The low content of the Greek lignites in gaseous hydrocarbons and the widespread tectonics in the Hellenic Peninsula are the main factors which prevented large gas accumulations in its 14 main coal deposits. However, additional research is needed to evaluate the coal-bed gas potential of the country

GENESIS AND PHYSICAL CHARACTERISTICS OF THE NEOGENE RED BEDS FROM THE CEDAR HILLS OF THESSALONIKI, MACEDONIA, GREECE

ABSTRACT The genesis and the physical characteristics of the Neogene red beds of the cedar hills surrounding Thessaloniki are studied in this paper. The peri-urban forest, which covers these hills, has a 3,022 ha area. The topographic relief is smooth and is divided in eight small drainage basins, tapped through small creeks. The elevation of the surrounding hills varies between 85 and 560 m. The dominant land slopes vary between 20 and 55%. All the samples are coarse grained, poorly sorted and friable and present earthy lustre and red colour because of the extensive presence of iron oxides. Angular to sub-angular rock fragments derived from the metamorphic bedrock are very common. Petrographically, the studied red beds belong to the clayey sands. The extended presence (41-66%) of coarse silt and sand size grains (&gt;20 µm) in the samples suggests a mild intensity of in situ weathering of the bedrock. X-ray diffraction analysis of the coarsest fractions 250-20 µm and 20-2 µm revealed in decreasing abundance the presence of quartz, feldspars, epidote, micas, chlorite, pyroxenes, amphiboles, and talc. These fractions contain the 2M polytype of mica, while in the fraction &lt;2 µm the 1Md polytype of illite predominates. In the clay fraction (&lt;2 µm) illite, smectite, and chlorite predominate. The presence of mixed-layer minerals is limited, testifying the almost complete character of hydrolysis of the primary minerals. The formation of red beds took place on low relief land under alternating wet and dry seasons, which prevail in the eastern Mediterranean region since Neogene. The clay minerals are the in situ weathering products of the primary minerals of the greenschists, gneisses and gabbros predominating in the studied area. The extensive presence of clay size grains (11-26%) in the samples, their poor sorting, and their sub-angular morphology, indicate that the red beds are texturally immature. In addition, the abundance of feldspars and Fe-Mg minerals reflects mineralogical immaturity. The low relief and the long-lasting tectonic stability in the Thessaloniki district were essential for the significant thickness of the red beds. The oxygen isotope data of the &lt;0.2 µm fraction (+18.2 to +18.8‰) confirm the pedogenic origin of the clay minerals present. The red beds studied present low plasticity with liquid limit (Wl) 26.9 to 33.4% and plasticity index (Ip) 9.1 to 17.3%. In addition, they have high consolidation index (Ic) values (1.03 to 2.28). The swelling potential is low to medium and the activity varies between 0.5 and 1.0. The consolidation and induration degree of the samples analyzed is low, because of the great range of their mineralogical composition and the mild conditions of pressure and temperature to which they have been submitted. The studied red beds are not considered problematic for the foundation of various constructions on them