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Geological sketch-map of NW Almopia Basin (based on Mercier et al. 1988); inset maps: Greece with the Almopia Basin depicted (upper left corner); Almopia Basin and Speleopark (upper middle); 3D view of the geology of the Almopia Speleopark broader area (upper right corner, vertical exaggeration 1.5).

Geological sketch-map of NW Almopia Basin (based on Mercier et al. 1988); inset maps: Greece with the Almopia Basin depicted (upper left corner); Almopia Basin and Speleopark (upper middle); 3D view of the geology of the Almopia Speleopark broader area (upper right corner, vertical exaggeration 1.5).

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Article
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Morphological features and formation conditions of The Almopia Speleopark caves (Loutra Almopias, N. Greece) The Almopia Speleopark caves are located at the Almopia basin in northern Greece, at the foothill of Voras Mountain, and are formed in the Maestrichtian limestones of the Pelagonian zone. They are studied on the basis of their meso-and micro...

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Context 1
... Speleopark is located at the Almopia basin in northern Greece, at the foothill of Voras Mountain (Kato Loutraki village). The area under study belongs to the Pelagonian zone of the Hellenides and is situated not far from the geological boundary with the Almopia zone (Fig. 1). The area consists of alpine metamorphic rocks, Mesozoic carbonates and flysch deposits of Upper Cretaceous-Palaeocene age. Volcanic rocks of intermediate composition and high potassium character intrude the Almopia zone (Vougioukalakis 2002). The volcanic activity is dated between 5 Ma (million years) at the eastern and 1.8 Ma at the ...
Context 2
... years) at the eastern and 1.8 Ma at the south-eastern part of the Voras Mountain ( Kolios et al. 1980). The caves were formed in the Maestrichtian limestones of the Pelagonian zone. Geological formations are dominated tectonically by the ENE-WSW striking Loutraki Fault and the NNW-SSE striking overthrust of Almopia zone onto the Pelagonian (Fig. 1). Ore-bearing faults (filled with pyrite, Mn-and Fe-oxides) occur north and north-west of the Kato Loutraki village (Mountrakis 1976). The Loutraki Fault bounds the Voras Mt. against the Almopia basin, which is due to the Neogene extensional tectonic regime (Chatzidimitriades 1974;Mountrakis 1976;Eleftheriadis ...
Context 3
... Varathron Cave is located at the northern slope of the Thermopotamos valley (Fig. 1). The two lower entrances of the cave are located at 500 m of altitude and the third one at 520 m. The solutional morphology of the cave is typical for the Almopia Speleopark caves. The higher entrance is connected to the cave with an inclined passage, whose walls are covered by phreatic calcite (subaqueous coatings) forming cave clouds ...
Context 4
... results from the fluid inclusions are depicted in Fig. 10. At room temperature, only two phase liquid-vapor inclusions were identified. Inclusions that were analyzed, ranged in diameter between 8 and 95 μm and homogenized into the liquid state. The primary ...
Context 5
... % vapor). The variability in homogenization temperature data may be due to real variability in the FIAs or to post-entrapment processes such as thermal re-equilibration or undetectable necking-down (Gold- stein 2003). Homogenization temperatures of all but seven of sixty-nine fluid inclusions range from 120 ºC to 189 ºC, with a peak around 150 ºC (Fig. 13). The other eight inclusions, possibly secondary, homogenized between 68 ºC and 104 ºC. Eutectic temperatures (Te) of fluids range from −20.5 ºC to −21.5 ºC, suggesting that salts in the fluids are dominated by NaCl (Crawford 1981;Shepherd et al. 1985). The final ice melting temperatures in the same inclusions range from -0.1 ºC to -0.6 ...
Context 6
... along linear trends that do not cross cleavage or growth boundaries. FIAs showed restricted temperature ranges such as 131 ºC to 148 ºC, 148 ºC to 163 ºC, 153 ºC to 161 ºC and 154 ºC to 166 ºC, showing that the assemblages are true FIAs and, therefore, that these ranges probably represent primary Th. In contrast, the low Th fluid inclusions (Fig. 10) were affected by secondary processes, such as necking-down and ...

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Citations

... Furthermore, we compared the rose diagram pattern of the passage orientation in Asprorema Cave with those from the caves of the Almopia Speleopark ( Figure 5), located in proximity to Asprorema Cave and formed by hydrothermal hypogene speleogenesis [49][50][51]. Asprorema Cave displays a major passage with a NE-SW orientation and a minor one striking ESE-WNW. Among the Almopia caves, Varathro cave, the largest one, also displays a NE-SW major passage orientation and an ENE-WSW secondary one, parallel to the large neotectonic Aridea fault [20,32]. ...
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Caves serve as time capsules, preserving significant markers of tectonic activity and offering insights into geological history. Fault geometries and past activations found in caves can be correlated with known deformational events in the broader area, temporally delimiting the speleogenesis. More specifically, cave passage formation is suggested to be affected by the regional stress-field. The Asprorema Cave in Northern Greece is a typical example of a fracture guided cave, with passage geometry influenced by relative sidewall movements, revealing these discontinuities as faults. This study constructs the timeframe and conceptual model of speleogenesis in relation to tectonic events, geomorphological evolution and hydrological zones, and verifies its relation to the stress-field. Active tectonics, mineralogy and cave geomorphology are investigated. Results suggest syntectonic speleogenesis under phreatic and epiphreatic conditions. The absence of corrosion on fault slip surfaces implies recent activations post cave’s shift to the vadose zone. Structural analysis identifies three main neotectonic phases: NNW-SSE striking faults (oldest group of structures), NE-SW striking faults with dextral strike-slip movement (post-middle Miocene), and NE-SW striking normal faults indicating extensional stress-regime (Quartenary). The last two phases affect cave passage shape causing wall displacement, highlighting passage formation along discontinuities perpendicular to the horizontal minimum stress axis.
... Εικόνα 1. Απλή σχηματική αναπαράσταση σε κατακόρυφη τομή για τις σχέσεις που έχουν μεταξύ τους τα μικρομορφολογικά γνωρίσματα που βρίσκονται σε υπογενή σπήλαια (από Lazaridis and Melfos, 2021). ...
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Thesis
This thesis is based on fieldwork research for identifying hypogene caves in Greece. Specifically, 33 caves studied in the following 21 locations: Mavros Vrachos Quarry Cave (MVQ) in Sidirokastro, caves in Falakro Mountain, caves in the Loutra Eleftheron area, Theohari Cave in Menoikio, Retziki Cave in Thessaloniki, caves on Mount Athos, Maroneia Cave, Kagiali Cave, and Koufovouno cavew in Evros, Petralona and Nychteridon caves in the Petralona region, Aghia Paraskevi Caves in Chalkidiki, Almopia Varathron cave, Polycarpi Quarry caves, Lesvos caves, Routsi Cave in Rapsani, Orliakas pothole, Ymittos caves, Ikaria Caves, Kryas Vrysi Cave in Karditsa, and Kounoupeli and Anygridon Nymphon caves in the W. Peloponnese region. These caves were initially identified as hypogene based on geomorphological criteria and were further explored to locate cave formations associated with speleogenesis, such as the speleothems spar and mammillaries. Samples from these deposits were collected and studied using various methods, including mineralogical, geochemical, and isotopic analyses. Scanning electron microscopy was employed to investigate their structure. A fluid inclusions study aimed to measure the homogenization temperatures of calcite crystals and determine the origin of fluids. The minerals identified in this research include calcite, aragonite, gypsum, alunite, pickeringite, tamarugite, barite, orpiment, goethite, quartz, manganese oxides, amorphous siliceous, and alluminosilicate minerals. Iron and manganese oxides and hydroxides were studied for the first time in Greek caves, with the unique case of a deposit bearing microbial bio-signatures in the goethite of the MVQ. Quartz was discovered for the first time in Greek caves. Specifically, calcite, Fe and Mn oxides, and sulfates were extensively studied based on their chemical and mineralogical composition, stable isotopes of oxygen, carbon, and sulfur, as well as fluid inclusions. These data, combined with geological, tectonic, hydrological, and other regional information, were used to draw conclusions about the speleogenesis of each cave or cave group. The speleogenesis is attributed mainly to dissolution by carbonic acid and, in some cases, sulfuric acid. The fluids that formed the caves were predominantly meteoric in origin. The peaks of homogenization temperatures measured in calcite crystals were high, ranging from 90°C to 280°C. Subsequently, all cases were examined and discussed in relation to the geological structure and evolution of the Greek orogeny. Based on the research results, the hypogene caves studied in Greece can be classified into two categories: endogenous hypogene caves and those formed in aquifers communicating laterally with the sea, where speleogenesis depends on the presence of hydrogen sulfide in the fluids. In the case of Agia Paraskevi Caves, a complex speleogenesis combining both categories of sulfuric acid and carbonic acid speleogenesis are observed. Based on the cave types, a close relationship was found with hydrothermal fluids and the presence of an extensional geodynamic regime, the collapse of the orogeny accompanied by faults that can favor the rise of fluids. The intrusion of plutonic bodies, the formation of basins, and consequently conditions for geothermal anomalies and geothermal fields have interacted in the occurence of hypogene speleogenesis.
Chapter
Many hypogene caves have been recognized in several locations in Greece in the last decade. Their identification is mostly based on morphological criteria and in some cases on geochemical evidence, including mineral and water chemistry. Several patterns of cave development have been recorded along with various small-scale morphological features. In this chapter, hypogene caves are presented per region in terms of different geotectonic units. These caves cover the whole Greek mainland and some islands of the Aegean archipelago. Their altitudinal distribution ranges from the sea level up to about 2000 m elevation. Nowadays, most caves are uplifted relicts of hydrothermal systems. The dissolution was caused mainly due to CO2-rich water, and in a few cases speleogenesis was driven by H2S. Speleogenesis in most cases took place below the water table in a deep phreatic setting, by slowly convecting waters. However, there are water-table caves, commonly related to H2S speleogenesis. It is demonstrated that hypogene speleogenesis in Greece is strongly related to the hydrothermal regime. Cave morphology, stratigraphy, hydrogeology, volcanism, tectonics, mineralogy and geochemistry are briefly discussed with respect to the structure of the Hellenic alpine orogene and its evolution.