Northern Euboea Research Articles

Mediterranean Wildfires’ Effect on Soil Quality and Properties: A Case from Northern Euboea, Greece

Mediterranean Wildfires’ Effect on Soil Quality and Properties: A Case from Northern Euboea, Greece

GIS-Based Assessment of Fire Effects on Flash Flood Hazard: The Case of the Summer 2021 Forest Fires in Greece

Greece, like the rest of the Mediterranean countries, faces wildland fires every year. Besides their short-term socioeconomic impacts, ecological destruction, and loss of human lives, forest fires also increase the burnt areas’ risk of flash flood phenomena, as the vegetation, which acted in a protective way against runoff and soil erosion, is massively removed. Among the most severe wildland fire events in Greece were those of summer 2021, which were synchronous to the very severe heat waves that hit the broader area of the Balkan Peninsula. More than 3600 km2 of land was burnt and a significant amount of natural vegetation removed. Three of the burnt areas are examined in this work, namely, Attica, Northern Euboea, and the Peloponnese, in order to assess their risk of future flash flood events. The burnt areas were mapped, and their geological and geomorphological features studied. Flash flood hazard assessment was accomplished through a Boolean logic-based model applied through Geographic Information Systems (GIS) software, which allowed the prioritization of the requirement for protection by identifying which locations were most prone to flooding. The largest part of our study areas is characterized by geomorphological and geological conditions that facilitate flash flood events. According to our findings, in almost all study areas, the regions downstream of the burnt areas present high to very high flash flood hazard, due to their geomorphological and geological features (slope, drainage density, and hydrolithology). The only areas that were found to be less prone to flood events were Vilia and Varimpompi (Attica), due to their gentler slope inclinations and overall geomorphological characteristics. It is known that vegetation cover acts protectively against flash floods. However, in this case, large areas were severely burnt and vegetation is absent, resulting in the appearance of flash floods. Moreover, imminent flooding events are expected to be even more intense in the areas downstream of the burnt regions, possibly bearing even worse impacts on the local population, infrastructure, etc.

Assessment of Fire Effects on Surface Runoff Erosion Susceptibility: The Case of the Summer 2021 Forest Fires in Greece

The wildfires of summer 2021 in Greece were among the most severe forest fire events that have occurred in the country over the past decade. The conflagration period lasted for 20 days (i.e., from 27 July to 16 August 2021) and resulted in the devastation of an area of more than 3600 Km2. Forest fire events of similar severity also struck other Mediterranean countries during this period. Apart from their direct impacts, forest fires also render an area more susceptible to runoff erosion by massively removing its vegetation, among other factors. It is clear that immediately after a forest fire, most areas are much more susceptible to erosion. In this paper, we evaluate the erosion hazard of Attica, Northern Euboea, and the Peloponnese that were devastated by forest fires during the summer of 2021 in Greece, in comparison with their geological and geomorphological structures, as well as land cover and management. Given that a very significant part of these areas were burnt during the major conflagrations of this summer, erosion risk, as well as flood risk, are expected to be very high, especially for the coming autumn and winter. For the evaluation of erosion risk, the burnt areas were mapped, and the final erosion-risk maps were constructed through GIS software. The final maps suggest that most of the burnt areas are highly susceptible to future surface runoff erosion events.

CO2 release to the atmosphere from thermal springs of Sperchios Basin and northern Euboea (Greece): The contribution of “hidden” degassing

Greece is a region characterised by intense geodynamic activity that favours the circulation of hydrothermal fluids in the crust transporting volatiles from either the deep crust or the mantle to the surface. Elevated heat flow values are detectable at Sperchios Basin and North Euboea (central Greece), two areas defined by a system of deeply rooted extensional faults and Quaternary volcanic activity. This setting contributed to the formation of numerous hydrothermal systems, which are mostly expressed as CO2-rich thermal springs with intense bubbling.The CO2 output from six bubbling pools has been determined by flux measurements with the use of the floating chamber method. The highest bubbling CO2 output has been found at Thermopyles and Psoroneria (0.6 and 0.84 t/d, respectively), where the outgoing channels have an elevated flow (>250 l/s) of gas-charged water (>15 mmol/l of CO2). Although no bubbling is noticed along the stream, the CO2 content decreases by an order of magnitude after few hundreds of metres, indicating an intense degassing from the water. Taking into account the water flow and the amount of CO2 lost to the atmosphere, the CO2 output of the outgoing channels is quantified in 12.5 t/d for Thermopyles and 9.23 t/d for Psoroneria. Output estimation has also been made for the other springs of the area. The diffuse CO2 release from the outgoing channels has always been higher respect to that of the visible bubbling, suggesting that most of the degassing is “hidden”. Furthermore, the loss of CO2 from the water has determined a shift in dissolved carbonate species as demonstrated by the pH increase along the channel that led eventually to an oversaturation in carbonate minerals and therefore travertine deposition.The total CO2 output to the atmosphere of the study area is estimated at ~27 t/d, with the major contribution deriving from the degassing along the outflow channels of the thermal springs. Such output is comparable to that of the single active volcanic systems along the South Aegean Active Volcanic Arc and highlights the importance of “hidden” degassing along CO2-oversaturated streams.

Radiological and hydrochemical study of thermal and fresh groundwater samples of northern Euboea and Sperchios areas, Greece: insights into groundwater natural radioactivity and geology.

A radiological and hydrochemical study has been conducted on thermal and fresh groundwater samples of northern Euboea Island and eastern central Greece. Both areas are characterized by complex geology and are renowned since antiquity for their hot springs, that are exploited for therapeutic spa purposes until today. The aim of the study was to combine radiological and hydrochemical data in order to achieve a holistic water quality assessment with insights into the geology of the study areas. All samples were characterized with respect to their major and trace ion and element composition, as well as activity concentrations of 222Rn, 226Ra, 228Ra, 228Th, and 40K. The samples demonstrated elevated natural radioactivity and U concentrations, especially in some locations of the Kamena Vourla area, reaching 179 Bq/L 222Rn, 2.2Bq/L 226Ra, 2.9Bq/L 228Ra, and 17μg/LU. The estimated circulation depth of thermal groundwater ranges between 250m in central Greece and 1240m in north Euboea study area, whereas the calculated water residence times range between 27 and 555years. Our data suggest the possible presence of an unknown until know U-rich plutonic rock formation in Kamena Vourla area and immiscibility of the fresh and thermal groundwaters in the studied areas.

GEOCHEMISTRY OF THE GAS MANIFESTATIONS OF GREECE: METHANE AND LIGHT HYDROCARBONS

Greece has a very complex geodynamic setting deriving from a long and complicated geological history being characterized by intense seismic activity and enhanced geothermal gradient. This activity, with the contribution of an active volcanic arc, favours the existence of many gas manifestations. Depending on the prevailing gas species, the latter can be subdivided in three main groups: CO2-, N2- and CH4- dominated. In the present work, we focus on methane and light hydrocarbons (C2-C6) to define their origin. CH4 concentrations (<2 to 915,200 μmol/mol) and isotopic ratios (δ13C -79.8 to +16.9 ‰, δD -298 to +264‰) cover a wide range of values indicating different origins and/or secondary post-genetic processes. Samples from gas discharged along the Ionian coast and in northern Aegean Sea have a prevailing microbial origin. Cold and thermal gas manifestations of central and northern Greece display a prevalent thermogenic origin. Methane in gases released along the active volcanic arc is prevailingly abiogenic, although thermogenic contributions cannot be excluded. Gases collected in the geothermal areas of Sperchios basin and northern Euboea are likely affected by strong secondary oxidation processes, as suggested by their highly positive C and H isotopic values (up to +16.9‰ and +264‰ respectively) and low C1/(C2+C3) ratios.

A new terrestrial active mineralizing hydrothermal system associated with ore-bearing travertines in Greece (northern Euboea Island and Sperchios area)

The northwestern Euboea Island and the neighboring part of the mainland in eastern Central Greece, i.e. Sperchios area, contain several hot springs and active thermogenic travertine deposits, which are the surface manifestations of an active hydrothermal system, controlled by active tectonics, and supplied with heat by a 7–8km deep magma chamber, with surface manifestation, the Plio-Pleistocene trachyandesitic volcanic center of Lichades. This hydrothermal system is fueled by a mixture of seawater and deep magmatic fluid with only limited meteoric water contribution. Thermal water samples show extreme pH, temperature and Electrical Conductivity values, with maximum values always recorded in two locations (Aedipsos and Ilia). The observed similarities in fluid compositions for most of the analyzed anions, major and trace elements, suggesting a stronger hydrothermal signature for the Northern Euboea area, perhaps reflecting greater proximity to the heat source of the hydrothermal system. The hydrothermal fluids collected and analysed were found to be highly enriched in a number of metallic and non-metallic elements e.g. up to 100μg/L As, up to 1.1wt.% Fe, up to 340μg/L Ba, up to 65μg/L Cu, up to 2.1wt.% Cl, up to 3700mg/L SO42−, up to 390μg/L Se. Some of the enrichments are reflected directly in the travertines lithogeochemistry and the metallic mineral phases found inside the travertines. A number of mineral phases including sulfides (such as pyrite, arsenopyrite, galena, chalcopyrite, sphalerite and stibnite), native elements (such as Pb and Ni), alloys (such as Au±Cu-Ag) fluorite and REE-bearing phases (such as Ce-, Nd- and La-bearing members of hydroxylbastnäsite, cackinsite, lanthanite and sahamalite) were identified syngenetically enclosed as clastic grains within the pores of all studied travertines; the ore grade concentrations of some iron-rich travertines (up to 28.9wt.% Fe and up to 1.83wt.% As), as well as the high concentration of precious and base metals at the hydrothermal fluid, strongly suggest active mineralizing processes throughout the studied system. Travertines containing elevated Fe±As and consisting of ferrihydrite in addition to aragonite/calcite, were deposited on the surface, most likely after mixing of ascending reducing hydrothermal fluids with cool seawater. The high REE content in the Fe±As-rich travertines (up to ~465mg/kg ΣREE) is caused by adsorption of REE-bearing phases by iron oxyhydroxides. Mineralogical and geochemical evidence (such as the presence of elements in their native form, of alloys such as Au±Cu-Ag, the enrichment of metalloids and the abundance of REE) may indicate magmatic contribution to the hydrothermal system and accordingly to the studied travertines. We support the hypothesis that metals and metalloids were mainly derived from magmatic fluids, which successively mixed with heated-, and with oxygenated, cool seawaters at depth and on the surface respectively, resulting in the deposition of carbonate-hosted sulfide mineralization at depth, and of Fe±As-rich travertines at the surface. The northwestern Euboea Island and Sperchios area hydrothermal system represents the first documented active terrestrial mineralizing hydrothermal system associated with ore-bearing travertines in Greece.

ORACLES ON FAULTS: A PROBABLE LOCATION OF A “LOST” ORACLE OF APOLLO NEAR OROVIAI (NORTHERN EUBOEA ISLAND, GREECE) VIEWED IN ITS GEOLOGICAL AND GEOMORPHOLOGICAL CONTEXT

At a newly discovered archaeological site at Aghios Taxiarches in Northern Euboea, two votive inscribed stelae were found in 2001 together with hellenistic pottery next to ancient wall ruins on a steep and high rocky slope. Based on the inscriptions and the geographical location of the site we propose the hypothesis that this is quite probably the spot where the oracle of “Apollo Selinountios” (mentioned by Strabo) would stand in antiquity. The wall ruins of the site are found on a very steep bedrock escarpment of an active fault zone, next to a hanging valley, a high waterfall and a cave. The geomorphological and geological environment of the site is linked directly to the regional geodynamical context of Central Greece, a region of tectonic turmoil throughout the Pleistocene and Holocene, characterised by distinct landscapes produced by the activity of active fault zones, intense seismicity, and in part, volcanism and hydrothermal activity. The geomorphological and geological similarities of the Ag. Taxiarches site with those of the oracle at Delphi, seem to provide further support to the hypothesis that the former site can well be that of an ancient oracle, given the recently established connections between the geological environment at Delphi and Apollo’s oracle there. Definitive verification of our hypothesis can only be obtained by further, detailed archaeological study, whereas geological/geomorphological, geochemical, and geochronological studies would be necessary to clarify the connection that the cave lying next to the wall remains may had with the site’s function.

Various morphological types of thermogenic travertines in Northern Euboea and Eastern Central Greece

In the northern part of Euboea Island and the neighbouring part of the mainland in eastern central Greece, many hot springs exist and some of them create travertine deposits. The objectives of the study were to identify and describe the various morphological types of the thermogenic travertine deposits. The samples were studied at the lab with optical microscopy, X-Ray Diffraction, Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS), in order to verify their main mineralogical composition and their mineral chemistry. The studied travertine deposits consist mainly of aragonite and calcite, but in some cases, as main mineral phase, an amorphous hydrous ferric oxyhydroxide (ferrihydrite), was also identified. The morphological types that were identified were of great variety (mounds, travertine caves etc) and some of them were quite rare (cascades, remora etc). Morphological data and field observations suggest possible inorganic and organic controls on carbonate precipitation. Similar morphological types have been recorded at large travertine systems like Mammoth hot springs, Yellowstone National Park in USA and at Rapolano Terme, Italy.

Predicting time-windows for full recovery of postfire regenerating Pinus halepensis Mill. forests after a future wildfire

A regeneration predictor (RP) has been elaborated to forecast the minimal inter-fire period, required for full recovery (assumed at 1,000 mature stems ha−1, a typical value for a dense pine forest) of an even-aged, postfire regenerating Pinus halepensis population after a subsequent wildfire, in the future. The study has been conducted in three Aleppo pine forests of northern Euboea Island, Greece. Postfire field surveys of sapling growth, sapling density and reproductive dynamics (cone-bearing population fraction, annual cone and seed production per sapling, canopy seed bank build-up) were carried out for three, consecutive growing seasons (years). Additional postfire parameters, with values estimated from literature data, have been also included in order to devise the RP. In the cases of the three populations studied, the application of this RP provides time-windows for full recovery after a recurrent fire, as short as 10–15, 8–11 and 7–11 years, respectively (values corresponding to best and worst scenarios). It is suggested that in even-aged, postfire regenerating Aleppo pine populations, the minimal inter-fire period required for full recovery can be predicted by monitoring a few selected variables, namely (a) sapling density, (b) vegetative to reproductive shift dynamics, and (c) cones/sapling and germinable seeds/cone, for at least 2 years (either consecutive or 2–3 years apart) at a postfire age of 7–12 years.

Distribution, lithotypes and mineralogical study of newly formed thermogenic travertines in Northern Euboea and Eastern Central Greece

Abstract In the northwestern part of Euboea Island and the neighbouring part of the mainland in eastern central Greece, many hot springs exist. We collected and analysed the newly formed material around the hot springs. The samples were studied at the lab with X-Ray Diffraction, Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). In all cases the studied materials were thermogenic travertine presenting many different lithotypes. The studied travertine deposits consist mainly of aragonite and calcite, but in some cases, as the main mineral phase, an amorphous hydrous ferric oxyhydroxide, probably ferrihydrite (creating a laminated iron-rich travertine deposit), was identified. The lithotypes that were identified were of great variety (spicular, shrubs, etc). Some of them (pisoliths, rafts and foam rock types) are quite rare and one of them (framework type) is described for the first time. Morphological data and field observations suggest possible inorganic and organic controls on carbonate precipitation. Similar lithotypes have been recorded at Mammoth hot springs, Yellowstone National Park in USA and at Rapolano Terme, Italy.

Hydrogeochemical characteristics and genetic implications of Edipsos thermal springs, north Euboea, Greece

Abstract Edipsos area, situated in northern Euboea, has been well known since ancient times for the existence of thermal springs. In order to assess the hydrogeochemical conditions, thermal and cold water samples were collected and analyzed by ICP method for major and trace elements. The results revealed the direct impact of seawater, a process which is strongly related to the major tectonic structures of the area. Seawater impact was confirmed by the Cl/Br and Na/Cl ionic ratios, as well as from statistical processing and graphical interpretation of the analytical results, which classified the sampled waters into three groups (two for cold waters and one for the thermal ones). Trace element ranges for thermal waters are: As (44–84 ppb), Pb (23–154 ppb), Ag (1–2 ppb), Mn (31–680 ppb), Cu (61–97 ppb), Cs (66–244 ppb), Se (0–76 ppb), Li (732–3269 ppb), Fe (0–1126 ppb), Sr (14000–34100 ppb), B (4300–9600 ppb). Compared with the chemical composition of other thermal springs from the Hellenic Volcanic Arc, Edipsos thermal waters are enriched in Ca2+, Na+, Cl−, SO4 2−, Li, B and K+, reflecting the influence from seawater. Cold waters are free of heavy metals compared with other natural waters and are characterized by good quality based on the major element chemistry. Finally, several geothermometers were applied in order to assess the reservoir temperatures, but none of them appear to be applicable, mainly due to the impact of seawater on the initial hydrogeochemistry of the geothermal fluids.

An almost complete skeleton of Metailurus parvulus (Carnivora, Felidae) from the late Miocene of Kerassia (Northern Euboea, Greece)

We describe a partial skeleton of Metailurus parvulus from the Turolian site of Kerassia 1 (Northern Euboea, Greece). The material, which consists of a mandible, the anterior and posterior limb-bone elements, some sternal bones and some vertebrae, is the most complete known of this species. The dental material is compared to specimens from Pikermi and Chomateri (Greece), and China. The limb-bones available offer us the possibility to discuss the status of some previously described specimens from Pikermi. The limb proportions indicate that M. parvulus had elongated posterior limbs relative to the anterior ones, which reflects developed jumping skills. M. parvulus had moderately developed cursorial abilities, intermediate between open and closed habitat felids, and probably frequented primarily relatively open woodlands.

Late Miocene horned rhinoceroses (Rhinocerotinae, Mammlia) from Kerassia (Euboea, Greece)

Recent systematic excavations near the village of Kerassia (Northern Euboea) have yielded a diverse mamm al fauna of Late Miocene age. Among the most complete and prominent findings are a juvenile skull and an adult mandible that belong to two different homed rhinoceros species. The juvenile skull from the site Kerassia-3 (K3) is assigned to Ceratotherium neumayri, while the adult mandible from the plausibly isochronous site Kerassia-4 (K4) belongs to Dihoplus pikermiensis. These new specimens are compared with the known Eastern Medi­ terranean rhinocerotid record, which is briefly reviewed and updated. The potential interspecific interaction of both species is discussed. Most Eastern Mediterranean localities have yielded only one tandem-homed rhino. In localities with ample material (Pikermi, Samos ), where both species are present, one of them is more abundant, signifying a clear interspecific dominance. D. pikermiensis must have preferred temperate forested habitats, whereas the more specialized C. neumayri more open habitats. For the cases of sympatry, a marked resource partitioning is suggested, not excluding some territorial interaction by water resources or at the boundaries of mixed habitats. A partial dietary competition in these eases cannot be excluded, as well.

THE LANDSLIDE IN THE AREA AGIA-ANNA OF THE SOUTHERN PART OF EUBOEA

On 20th February of 2003, an extensive landslide took place at the southern margins of the Agia-Anna village, in the northern Euboea. It caused a lot of material damages (buildings, cemetery and provincial road) and agony in the people of the village, as well as a lot of problems to their properties. In this paper it is described the phenomenon, the form of the landslide and the reasons which caused it, and the mechanism of the breaking and movement are also dilated. The main and secondary breakings of the earth, are extended in an area of 85-90 acres. Their direction is about N-S and the movements are generally directed to the eastern with a resultant ASA. The breakings depth must be not more than 3-4 meters. Most of them are of the order of 0,50-1,5 m and they are not continuous but interrupted. The breakings are usually in a straight line and are arrangement in steps like gravity faults. The length of a continuous breaking is between of 1 to 30 m. In the area where the breakings are noticed, the morphological dip of the soil, before the landslide had been happened, was of the order of 13 to 14%. The drainage basin in the same area is not big enough to concentrate substantial amount of water. Therefore, additional factors, must have also influenced it. It is estimated that these factors are: a. The imperfect drainage of the rain waters and soil saturation through the fissures, because of small landslides and creeps. b. It is possible that small faults (small metaneogenic gravity faults) with parallel direction to the slope, to have acted as sliding surface. The small faults (gravity faults of some cm) are not visible in the argillo-marlaceous material, but it is rumoured to be, comparatively with the obvious tectonic character of the area. c. The mineral constituents of the argillo-marlaceous neogenic sediments, especially the montmorillonite, chlorite, illite, kaolinite and swelling chlorite, as well as their mechanical features, have contributed substantially to the development of landslide. d. The possibility that the neogenic formations are supplied sideways with water, by the adjoining and underlying carbonate rocks, it is also examined.

Boundary problem in carbon emission decomposition : Ang, O. and Choi, K.-H. Energy Policy, 2002, 30, (13), 1201–1205

The northwestern Euboea Island and the neighboring part of the mainland in eastern Central Greece, i.e. Sperchios area, contain several hot springs and active thermogenic travertine deposits, which are the surface manifestations of an active hydrothermal system, controlled by active tectonics, and supplied with heat by a 7–8 km deep magma chamber, with surface manifestation, the Plio-Pleistocene trachyandesitic volcanic center of Lichades. This hydrothermal system is fueled by a mixture of seawater and deep magmatic fluid with only limited meteoric water contribution. Thermal water samples show extreme pH, temperature and Electrical Conductivity values, with maximum values always recorded in two locations (Aedipsos and Ilia). The observed similarities in fluid compositions for most of the analyzed anions, major and trace elements, suggesting a stronger hydrothermal signature for the Northern Euboea area, perhaps reflecting greater proximity to the heat source of the hydrothermal system. The hydrothermal fluids collected and analysed were found to be highly enriched in a number of metallic and non-metallic elements e.g. up to 100 μg/L As, up to 1.1 wt.% Fe, up to 340 μg/L Ba, up to 65 μg/L Cu, up to 2.1 wt.% Cl, up to 3700 mg/L SO42 −, up to 390 μg/L Se. Some of the enrichments are reflected directly in the travertines lithogeochemistry and the metallic mineral phases found inside the travertines. A number of mineral phases including sulfides (such as pyrite, arsenopyrite, galena, chalcopyrite, sphalerite and stibnite), native elements (such as Pb and Ni), alloys (such as Au ± Cu-Ag) fluorite and REE-bearing phases (such as Ce-, Nd- and La-bearing members of hydroxylbastnäsite, cackinsite, lanthanite and sahamalite) were identified syngenetically enclosed as clastic grains within the pores of all studied travertines; the ore grade concentrations of some iron-rich travertines (up to 28.9 wt.% Fe and up to 1.83 wt.% As), as well as the high concentration of precious and base metals at the hydrothermal fluid, strongly suggest active mineralizing processes throughout the studied system. Travertines containing elevated Fe ± As and consisting of ferrihydrite in addition to aragonite/calcite, were deposited on the surface, most likely after mixing of ascending reducing hydrothermal fluids with cool seawater. The high REE content in the Fe ± As-rich travertines (up to ~ 465 mg/kg ΣREE) is caused by adsorption of REE-bearing phases by iron oxyhydroxides. Mineralogical and geochemical evidence (such as the presence of elements in their native form, of alloys such as Au ± Cu-Ag, the enrichment of metalloids and the abundance of REE) may indicate magmatic contribution to the hydrothermal system and accordingly to the studied travertines. We support the hypothesis that metals and metalloids were mainly derived from magmatic fluids, which successively mixed with heated-, and with oxygenated, cool seawaters at depth and on the surface respectively, resulting in the deposition of carbonate-hosted sulfide mineralization at depth, and of Fe ± As-rich travertines at the surface. The northwestern Euboea Island and Sperchios area hydrothermal system represents the first documented active terrestrial mineralizing hydrothermal system associated with ore-bearing travertines in Greece.

Accidental and long-term safety assessment of fission and fusion power reactors : Ciampichetti, A. et al. Fusion Engineering and Design, 2002, 63–64, 229–234

The northwestern Euboea Island and the neighboring part of the mainland in eastern Central Greece, i.e. Sperchios area, contain several hot springs and active thermogenic travertine deposits, which are the surface manifestations of an active hydrothermal system, controlled by active tectonics, and supplied with heat by a 7–8 km deep magma chamber, with surface manifestation, the Plio-Pleistocene trachyandesitic volcanic center of Lichades. This hydrothermal system is fueled by a mixture of seawater and deep magmatic fluid with only limited meteoric water contribution. Thermal water samples show extreme pH, temperature and Electrical Conductivity values, with maximum values always recorded in two locations (Aedipsos and Ilia). The observed similarities in fluid compositions for most of the analyzed anions, major and trace elements, suggesting a stronger hydrothermal signature for the Northern Euboea area, perhaps reflecting greater proximity to the heat source of the hydrothermal system. The hydrothermal fluids collected and analysed were found to be highly enriched in a number of metallic and non-metallic elements e.g. up to 100 μg/L As, up to 1.1 wt.% Fe, up to 340 μg/L Ba, up to 65 μg/L Cu, up to 2.1 wt.% Cl, up to 3700 mg/L SO42 −, up to 390 μg/L Se. Some of the enrichments are reflected directly in the travertines lithogeochemistry and the metallic mineral phases found inside the travertines. A number of mineral phases including sulfides (such as pyrite, arsenopyrite, galena, chalcopyrite, sphalerite and stibnite), native elements (such as Pb and Ni), alloys (such as Au ± Cu-Ag) fluorite and REE-bearing phases (such as Ce-, Nd- and La-bearing members of hydroxylbastnäsite, cackinsite, lanthanite and sahamalite) were identified syngenetically enclosed as clastic grains within the pores of all studied travertines; the ore grade concentrations of some iron-rich travertines (up to 28.9 wt.% Fe and up to 1.83 wt.% As), as well as the high concentration of precious and base metals at the hydrothermal fluid, strongly suggest active mineralizing processes throughout the studied system. Travertines containing elevated Fe ± As and consisting of ferrihydrite in addition to aragonite/calcite, were deposited on the surface, most likely after mixing of ascending reducing hydrothermal fluids with cool seawater. The high REE content in the Fe ± As-rich travertines (up to ~ 465 mg/kg ΣREE) is caused by adsorption of REE-bearing phases by iron oxyhydroxides. Mineralogical and geochemical evidence (such as the presence of elements in their native form, of alloys such as Au ± Cu-Ag, the enrichment of metalloids and the abundance of REE) may indicate magmatic contribution to the hydrothermal system and accordingly to the studied travertines. We support the hypothesis that metals and metalloids were mainly derived from magmatic fluids, which successively mixed with heated-, and with oxygenated, cool seawaters at depth and on the surface respectively, resulting in the deposition of carbonate-hosted sulfide mineralization at depth, and of Fe ± As-rich travertines at the surface. The northwestern Euboea Island and Sperchios area hydrothermal system represents the first documented active terrestrial mineralizing hydrothermal system associated with ore-bearing travertines in Greece.

Geodynamics and evolution of the Miocene mineralization in the Cycladic - Pelagonian belt, Hellenides

The paper aims to provide a sound account of the type of Miocene mineralisations in the Cycladic – Pelagonian belt and their relationship with the geodynamic evolution of the area. Skarn and manto types, epithermal precious and base metals mineralisation, and vein magnesite in ultramafics are associated to distinct stages of the geodynamic evolution of the belt. Extensional tectonics favoured their generation. Late stages of extensional tectonics resulted in the formation of vertical to subvertical NW-SE trending fault zones, which were then used as conduits for ascending hydrothermal fluids. The relationship between the geodynamics and the metallogenetic evolution of the belt is discussed on the basis of available data on the geology of four critical areas: Tinos and Mykonos islands, Laurium and Northern Euboea.

Origin and emplacement of an inferred late Jurassic subduction-accretion complex, Euboea, eastern Greece

AbstractIn northern Euboea, central eastern Greece, an up to 3 km-thick polygenetic melange (Pagondas complex) is structurally interleaved between a Triassic–Jurassic carbonate platform (Pelagonian Zone) and an overriding harzburgitic ophiolite. The melange mainly comprises late Triassic shallow-water limestone and calciturbidites, radiolarites, Triassic–Jurassic tholeiites, alkaline basalts and minor andesites. The units concerned range from kilometre-sized thrust sheets, and detached blocks, to broken formation and structureless, or bedded matrix-supported conglomerates (diamictite). The melange includes remnants of Neotethyan oceanic lithosphere, overlain by radiolarites, hemipelagic carbonates and distal calciturbidites derived from a Mesozoic carbonate platform. Tholeiites were erupted at a Triassic–Jurassic spreading axis, whilst within-plate-type alkali basalts are interpreted mainly as seamounts. Kilometre-scale detached blocks of shallow-water coralline limestone are identified as collapsed atolls, formed within an ocean and/or along the rifted continental margin. Volcaniclastic sediments are locally interbedded with radiolarite, and reflect post-volcanic erosion of the ocean floor. Intra-oceanic convergence began, apparently in late early Jurassic time, giving rise to the Euboea ophiolite above an inferred westwards-dipping subduction zone. The Pagondas Complex then developed as an accretionary prism. The subduction trench later collided with the Pelagonian passive margin, driving the hot Euobea ophiolite over the accretionary complex, to produce amphibolites and greenschists of the metamorphic sole. Trench–margin collision then drove the entire supra-subduction zone complex, apparently eastwards, downflexing the Pelagonian carbonate platform to form a foredeep in which late Jurassic (Kimmeridgian–Tithonian) radiolarian sediments accumulated. During emplacement, the accretionary complex was disrupted and partly resedimented as debris flows, turbiditic volcaniclastic sandstone and shale in a foredeep, or foreland basin setting.

Late Cretaceous oceanic crust and Early Tertiary foreland basin development, Euboea, Eastern Greece

ABSTRACTIn northern Euboea (Eastern Greece), Late Cretaceous platform carbonates of the Pelagonian Zone pass depositionally upwards into Maastrichtian hemipelagic limestones, possibly reflecting a rifting event in the adjacent Neotethys. This is followed by a c. 1 km‐thick unit of siliciclastic turbidites, debris flows and detached limestone blocks. Thrust intercalations of ophiolitic rocks comprise altered pillow basalts and ultramafic rocks with ophicalcite. Calcite veins in sheared serpentinite contain planktonic foraminifera and the ophicalcite is directly overlain, with a depositional contact, by Globotruncana‐bearing pelagic limestones and calciturbidites of Maastrichtian age. The ophiolitic rocks are interpreted as Late Cretaceous oceanic crust and mantle, that formed at a fracture zone, or rifted spreading axis within a Neotethyan, Vardar basin to the east. During the Early Tertiary (Palaeocene–Eocene), the Neotethyan basin began to close, with development of a subduction‐accretion complex, mainly comprising sheared, trench‐type sandstones, associated with ophiolitic slices. In response to trench/margin collision, the Pelagonian carbonate platform foundered and limestone debris flows and olistoliths were shed into a siliciclastic foreland basin. Suturing of the Neotethyan ocean basin then resulted in westwards thrusting of oceanic units over the foreland basin, thrusting of slices of inferred Late Cretaceous Pelagonian carbonate platform slope and large‐scale recumbent folding.