HYDROTHERMAL CAVES IN ATHOS MT. (AGION OROS) Lazaridis, Georgios 1,a, Zhalov Alexey 2,a, Makrostergios Lampros 3, Genkov Anton 2,b, Gyorev Vanyo 2,c, Stoichkov Konstantin 2,d, Radulescu Antonis1,b, Agapov Ilia 4,a, Kaminskiy Sergey 4,b 1
School of Geology, Aristotle University of Thessaloniki, Greece, a geolaz@math.auth.gr, b fenderman4tele@gmail.com Speleo Club “Helictit”, Sofia, Bulgaria, a alex.1953@abv.bg, b TheLastGuard@gmail.com, c vanjobg@gmail.com, d danailspeleo@abv.bg 3 Mountaineering-Speleological Community, Karditsa, Greece, info@lmakro.com 4 Russian Geographical Society, St. Petersburg, Russia, a agapov_ilya@mail.ru, b intuzazist@mail.ru
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A newly identified field of hydrothermal caves in Athos Mt. (Agion Oros) is described here for the very first time. The cave pattern and the meso- and micro-scale morphology is given and discussed. Mineralogical evidence is preliminarily presented.
1. Introduction Hypogene-hydrothermal Speleogenesis has already been known in Chalkidiki Peninsula, northern Greece, from the caves of the Petralona area (Lazaridis, 2009; Veni et Al., 2009; Lazaridis & Melfos, in preparation) and the caves of Aghia Paraskevi (Lazaridis et al., 2011). However, there is no evidence that these two cases represent a single and contemporaneous speleogenetic stage in a particular uniform geothermal and geological regime. At the moment they are studied as distinct examples and further investigation of possible interrelation awaits further data. In the rest part of the Chalkidiki (apart from Athos Mt.) there is a large amount of caves, mostly explored and surveyed during the expeditions of the Hellenic Speleological Society, Department of Northern Greece in the summer season of 2012. Although some of these caves present morphological features resembling those with hypogene origin, there are not enough mineralogical or other evidence for their classification (Lazaridis, pers. observation). In particular the Peninsula of Agion Oros was systematically explored by the international project “The caves of Holy Mountain Athos” (Alexey, et al., 2011 & XXXX; https://sites.google.com/site/athosmistery/home) and three expeditions have been completed so far. During the third expedition of this project a new field with hydrothermal caves was identified. In these caves as well as in small fractures phreatic calcite crystals are formed at an altitude of about 1000 m above sea level (a.s.l.) up to almost the peak of the Athos Mt. (2033 m a.s.l.). The area is located at the south-central part of the Athos Mt. and especially at the steep slopes above the “Krya Nera” location where the morphological gradient of the mountain increases and the forest ends as well as at the surroundings of the Panagia Church. The caves are located in Triassic recrystallized limestones and marbles of the Circum-Rhodope belt (e.g. Georgiadis et al., 2007 and references therein). In the present study we present description of the newly identified hydrothermal cave-field as well as the cave
pattern and the meso- and micro-scale dissolution morphological features found in these caves.
2. Cave Location-Morphology-Mineralogy The location and the description of the caves studied at Athos Mt. are given below. Typical cave pattern is given in ground plans, longitudinal and cross sections in Fig. 1.
1. A small cave, at 1476 m a.s.l., is located at an almost vertical wall of carbonate rocks (marbles) (N40 08 58.3, E24 19 38.1) south of the Panagia Church. The shape of the cave entrance is almost circular and quite symmetrical. The internal morphology is similarly symmetrical and its dimensions are gradually decreasing. Few meters inside the entrance the horizontal part turns upward to a passage (Fig. 2a) of “outlet” morphology (sensu Klimchouk, 2007). The most internal horizontal part and the vertical outlet are lined with scalenohedral calcite crystals up to few centimeters long. Their color is yellow to brown due to impurities. Lateral pockets inside the horizontal part are also lined with these phreatic crystals (Fig. 2b). Furthermore, small curved wall pockets, which end to a flat ceiling, regardless of the geological structure, found at the cave-walls and resemble to the ”Kempe facets” (Laügdecke of Kempe et al., 1975; corrosion bevels of Ford and Williams 2007) a morphology that is characteristic for speleogenesis by water convection.
2. The cave of Pachoumios Kelli (Fig. 2c,d) is located at 1074 m a.s.l. (N40 08 54.8, E24 20 02.2) and may be considered the most typical hydrothermal cave of the area. It is mostly vertically developed and can be considered as a relict outlet. The lower part of the cave is divided in to two partial chambers which are meet upwards. Its side-walls are covered with scalenohedral calcite crystals longer than in the above mentioned cave, exceeding 5 cm in length. They are “island spars” in their core and yellow to brown calcite. Inside the cave three different floor levels were found. Based on historical data it is very probable these floors were artificially constructed by the monk Pachoumios and his
students, during their living inside this cave. The absence of calcite crystals or the presence of broken ones in these floors is in agreement with this suggestion. Wooden columns, stairs and constructions were placed into artificial pockets on the cave-walls.
Figure 1. Typical morphology of the Athos Mt. caves (Pachoumios Kelli cave and the “small cave) in ground plans, longitudinal and cross-sections.
3. In the same area, at 1076 m a.s.l. (N40 08 55.1, E24 20 05.3), a small cavernous place was discovered that present wall-pockets with the ”Kempe facets” (Fig. 2e).
4. About 100 m east of the Pachoumios Kelli cave, another “Small Cave” (Fig. 2f) is located at 1083 m a.s.l. (N40 08 54.0, E24 20 03.8). Two entrances lead to a small chamber in which partitions (a form of speleogens) occur. The cave is small but its morphology is similar with those that display calcite crystals.
5. The Athos Cave, (Fig. 2g), as it has been called by previous visitors, is located at 1128 m a.s.l. (N40 08 57.2, E24 20 04.7) and is the largest known cave in the whole peninsula. There is a large chamber with two entrances, and it is separated by a bedrock bridge. The upper most parts of the chamber continues to a passage of much smaller dimensions and a vertical part that ends to an outlet as far as can be seen. The latter was partially explored during this project. The “outlet” morphology of this cave is in accordance with the rest of the area. Speleothems were found only at the deepest parts of the cave, far from the entrances, and they are in general
intensively corroded and covered by a layer of weathered material. However, in many places (especially in small pockets) some speleothems are not weathered. Flowstones, cave corals, stalactites, stalagmites, columns, thick helictites, and bottlebushes on tiny stalactites that are few centimeters long found in this cave in contrast to the rest caves where in general speleothems are scarcely developed. Photoluminesence of one broken calcite crystal on the cave-wall of the Pachoumios Kelli cave was tested in situ and contemporaneously videotaped by using an external flash-light and a digital camera (see Shopov, 1997 and references therein). From the analyses of the video it is shown that the “iceland spar” in the core of the crystal was emitted a red light for about one fifth of a second (Fig. 3) whereas the most external yellow layer was emitted a light blue light that lasted about one second. Similar results observed for the yellow calcite crystals found at the small cave close to Panagia Church even though “iceland spar” did not found. Similar luminescence has been observed in hydrothermal calcite crystals which formed at > 60 oC (Dublyansky, 2000).
3. Conclusions The newly identified hypogene morphologies of the caves at Athos Mt. is a significant addition to our previous knowledge in the area of the Chalkidiki Peninsula and the broader central Macedonia in N. Greece. They are relict caves that mostly represent outlet morphology. Typically their side-walls are covered with calcite crystals.
Morphologically they are mostly ascending passages, resembling outlets, with “kempe facets�, cupolas, blind passages, bedrock ridges, partitions and similar speleogens that are typical in hydrothermal caves. A photoluminescence survey of these crystals inside the caves revealed their hydrothermal origin, which confirms a speleogenesis due to ascending thermal water in a convectional geothermal regime. Geochemical analyses in
Figure 2. Athos Mt. (Agio Oros) hydrothermal caves. a: outlet ceiling formation in the small cave close to Panagia Church; b: sidewall pockets in the small cave close to Panagia Church; c: the entrance of the Pachoumios Kelli Cave; d: upwards view of the Pachoumios Kelli Cave (outlet morphology); e: small cavernous form with Kempe facets; f: the interior of the small cave easterly of the Pachoumios Kelli Cave; g: the large chamber of the Athos Cave.
future studies will provide evidence that can be compared to those of previous studies in the Chalkidiki Peninsula in order to construct a regional speleogenetic model for the whole area.
We wish to express our thanks to the Assistant Professor Vasilios Melfos, Department of Mineralogy, Petrology, Economic Geology, School of Geology, Aristotle University of Thessaloniki, Greece, for his corrections on the manuscript that improved this paper.
Acknowledgments
Figure 3. Phreatic calcite crystals in a wall-pocket at the Pachoumios Kelli Cave in Athos Mt. Agio Oros and frames (inlet) of videotaped photoluminescence showing the duration of the emitted red and light-blue light after the flash-light.
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