6 research outputs found
An Alternative Georoute: Approaching the Geological Heritage of the SE Part of Milos Island, Greece, via Hiking, Kayaking and Snorkeling
No full textMilos Island is located at the southwest edge of the Cyclades island complex, in the central part of the Aegean
archipelago. It is part of the modern South Aegean Volcanic Arc (SAVA), which belongs to the Hellenic subduction
zone. This on-going process has resulted in the coexistence of complex geological formations and geodynamic
phenomena with sceneries of incomparable natural beauty, in many areas along the arc. Among them, Milos Island
is widely known to be a place of astonishing geological and natural wealth, combined with a cultural heritage that
dates back to the 8th millennium BC.
As geotourism has been rapidly evolving worldwide over the last years, Milos Island was among the first places
in Greece that developed a network of geotrails and featured many sites of special interest in terms of geology,
volcanology and geoarchaeology. This study proposes an original georoute through land and sea, which aims t
emerge both overland and underwater areas of special interest. It is a novel way to approach the geological and
cultural wealth of Milos and focuses on the Aghia Kiriaki area, at the South part of the island. This alternative
georoute includes hiking, kayaking and snorkeling, and anyone who follows it, can be guided to a significant
number of important geological, volcanic, morphological and geoarcheological sites, in a relatively narrow area,
combining athletic activities as well. The proposed georoute has a total length of 3,2 km and an estimated time
of completion of about 4 hours. It starts from Aghia Kiriaki area, where visitors can see remnants of one of
the island’s collapsed calderic domes in a panoramic view towards the East. In the same site, volcanic emanations
create impressive scenery, which introduces the participants to aspects of the island’s geologic and volcanic history.
After about 800 meters of hiking, throughout an area that is dominated by products of phreatic eruptions, Aghia
Kiriaki beach is the next stop. Impressive findings of roman pottery can be observed in this site. At this point,
hiking alters to kayaking eastwards along the coastline until the third stop, Psarovolada beach. Extended outcrops
of the metamorphic basement of the island, along with submerged hot springs are also observed in the area, while
not far away from this point, the most daring participants can dive and enjoy the underwater view of the hot springs
at the bottom of the sea. The kayaks are used for further 150m until the unique site of the pre-volcanic formations
of the island. From this point, georoute continues and visitors have again the opportunity to dive and approach
another submerged hot springs location, just by swimming approximately 20 m eastwards. The sea trip ends at
Sirocco, which is located in the center of the Paleochori Beach, where visitors can evaluate their experience.
The proposed georoute aims to highlight that preservation of the geological heritage fosters values that promote
society and geotourism is an excellent motivation of implementation
On the Color and Genesis of Prase (Green Quartz) and Amethyst from the Island of Serifos, Cyclades, Greece
No full textThe color of quartz and other minerals can be either caused by defects in the crystal structure or by finely dispersed inclusions of other minerals within the crystals. In order to investigate the mineral chemistry and genesis of the famous prase (green quartz) and amethyst association from Serifos Island, Greece, we used electron microprobe analyses and oxygen isotope measurements of quartz. We show that the color of these green quartz crystals is caused by small and acicular amphibole inclusions. Our data also shows that there are two generations of amphibole inclusions within the green quartz crystals, which indicate that the fluid, from which both amphiboles and quartz have crystallized, must have had a change in its chemical composition during the crystallization process. The electron microprobe data also suggests that traces of iron may be responsible for the amethyst coloration. Both quartz varieties are characterized by isotopic compositions that suggest mixing of magmatic and meteoric/marine fluids. The contribution of meteoric fluid is more significant in the final stages and reflects amethyst precipitation under more oxidizing conditions
M.Sc. Thesis Late-stage B-bearing fluid circulation in the Kavala pluton: Evidence from mineralogical, spectroscopic and geochemical data in tourmaline-rich fault-related rocks
No full textΤα τουρμαλινικά πετρώμτα της Καβάλας είναι προϊόντα κρυστάλλωσης υδροθερμικών ρευστών, εμπλουτισμένων σε Βόριο, που διαχωρίστηκαν από γρανιτικό μάγμα.Το μάγμα που δημιουργήθηκε με διαδικασίες τήξης του φλοιού, κατά τη διάρκεια της εκταφής του συμπλέγματος μεταμορφικού πυρήνα, διαφοροποιήθηκε και απελευθέρωσε μέσω βρασμού μια ρευστή φάση πλούσια σε B. Κατά το βρασμό η υδροστατική πίεση,ξεπέρασε την λιθο-στατική σε περιβάλλον ανώτερου τεκτονικού ορόφου, όπου επικρατεί η θραυσιγενής παραμόρφωση.Πολλαπλά στάδια υδραυλικής ρωγμάτωσης έλαβαν χώρα κατά μήκος των ΒΑ-ΝΔ αξονικών επιπέδων της φύλλωσης και πτύχωσης του γρανοδιορίτη, σε μεγάλες γωνίες κλίσης. Η διαδικασία αυτή πιθανόν να επαναλήφθηκε τουλάχιστον δύο φορές, ύστερα από επιπλέον διαφοροποίηση και απόμειξη. Η κυκλοφορία των υδροθερμικών ρευστών, είχε ως αποτέλεσμα την μετασωματική εξαλλοίωση του γρανοδιορίτη και τη δημιουργία τουρμαλινικών πετρωμάτων. Οι τουρμαλινίτες, στους οποίους το ποσοστό συμμετοχής του τουρμαλίνη ξεπερνά το 50% κ.ο., δημιουργήθηκαν σε υψηλούς λόγους αντίδρασης ρευστού/πετρώματος, ενώ τα τουρμαλινικά λατυποπαγή σε μικρότερους. Τα τουρμαλινικά λατυποπαγή, αποτελούμενα από γωνιώδεις κλάστες του περιβάλλοντος πετρώματος και κύρια μάζα από κρυπτοκρυσταλλικό τουρμαλίνη,υπερέχουν, και δείχνουν πως η διαδικασία ήταν υψηλής θερμοκρασίας και αλατότητας. Σταδιακός εμπλουτισμός σε βόριο και άλλα οξείδια συμβατά με τον τουρμαλίνη, σε συνδυασμό με την απόπλυση σε REE, παράγουν το γεωχημικό αποτύπωμα της τουρμαλινώσης, υποδεικνύοντας πολύ χαμηλό pH, κατά τη συνολική διαδικασία, το οποίο ίσως αποτελεί κύριο αποτρπετικό παράγοντα για την παρουσία μεταλλοφορίας θειούχων μέσα στα λατυποπαγή.The tourmaline-rich rocks in Kavala are the products of juvenile late B-rich hydrothermal fluids exsolved from a granitic magma. In other words, this granitic magma that generated after anatectic processes in a thickened crust, during its emplacement in an ascending core-complex margin was fractionated leading to the exsolution through boiling of an immiscible volatile B-rich phase. The boiling pressure of the fluid exceeded the relatively low lithostatic pressure as it happened in a brittle setting of upper tectonic floors. Hydraulic, almost vertical, fracturing of various degrees and in dispersed places occurred, which mostly located along the NE-SW axial planes of the foliated and folded granitic pluton. This process may have occurred at least two times after further magmatic fractionation and exsolution. Hydrothermal fluid infiltration, triggered metasomatic alteration of the host granodiotite, resulting in the formation of tourmaline-rich rocks. Tourmalinites, in which tourmaline exceeded 50% vol, were formed at high fluid/rock ratios, while tourmaline breccias formed at lower ones. The latter, which comprise abundant angular to sub-rounded clasts of country rock infilled mostly by cryptocrystalline tourmaline, prevailed, indicating that the process was of high temperature and salinity.Progressive enrichment in Boron and other oxides compatible in tourmaline, coupled with depletion in REE’s produced a geochemical signature of typical toyrmalinization, suggesting an acidic pH, for the overall procces, which is maybe a dominat factor for the absence of sulfide mineralization within the breccias.
Phosphorus-rich pyroxene in mantle xenoliths
No full textNumerous recent reports of detailed crystal zoning
patterns and anomalous enrichment in phosphorus (P) have
focused mainly on olivine from various settings [1-4]. P
enrichment and zoning in olivine have been attributed to
rapid crystal growth and development of disequilibrium as
well as to growth from P-rich melts. Here we report the
comparatively novel observation of elevated P in pyroxenes
from glass-bearing veins and pockets in a previously
undescribed xenolith from Cima Volcanic Field-CVF,
California; H.G. Wilshire (sample Ci-1-105) and in newly
collected mantle xenoliths from the Middle Atlas, Morocco.
Analytical techniques included optical microscopy, electron
microprobe and laser-ablation Inductively Coupled Plasma
Mass Spectrometry. We examine whether the P
concentrations in pyroxene (Px), although unusual, are in fact
anomalous compared to the adjacent glass concentration,
consider possible mechanisms for P enrichment, and correlate
the P enrichment in Px with indicators of metasomatism.
The petrogenetic history of each glassy region involves
melt intrusion, reaction with host minerals, cooling
accompanied by crystal growth, quench of glass, and possibly
later modifications. Secondary P-rich pyroxenes (P2O5 ~ 0.6
wt%) in a glassy pocket in the CVF xenolith are
homogeneous and surrounded by P-rich glass. They reflect
fairly slow near-equilibrium pyroxene growth after the melt
temperature became close to the host rock, with P
concentration in the melt buffered by apatite saturation. In the
Moroccan xenoliths, pyroxenes in a glassy vein exhibit
concentric zoning with P2O5 from 0.05 wt% (core) to ca. 0.3
wt% (intermediate) and then from 0.8 wt% (inner rim) to 1.2
wt% (outer rim). We attribute this to an accelerating rate of
crystal growth, with onset of a diffusive boundary layer pileup
effect and excess P incorporation near the pyroxene rim
Phosphorus interactions with Martian soil simulants
No full textPhosphorus (P) is an essential nutrient for plant growth. According to the vision of circular
bioeconomy, the management of nutrient-rich wastewaters should include both treatment and
utilization goals (Battista & Bolzonella, 2019). Consequently, the application of in-situ resources
utilization (ISRU), using typical Martian soil (e.g., Yen et al., 2005), is vital for the sustainability of
future long-term settlements on Mars.
Martian soil simulants, provided by The CLASS Exolith Lab from the University of Central Florida,
were tested for their phosphorus sorption capacity. Sorption of phosphate anions (PO4-P) from
aqueous solutions (AS) of KH2PO4 and sodium bicarbonate, as well as from hydrolyzed human
urine (HU) was examined at a preliminary stage, using three Martian soil simulants (MGS-1;
Rocknest soil, MGS-1S; M-WIP Reference Case B and MGS-1C; M-WIP Reference Case C; Cannon et
al. 2019). In particular, isothermal, kinetic, pH, temperature, initial sorbent concentration (5 g soil
simulant/L AS or HU, 10 g/L and 15 g/L) and desorption experiments were carried out, the duration
of which ranged from five days to three weeks.
The percentage of phosphorus removal was up to 60 % for the aqueous solutions and 24 % for the
hydrolyzed human waste. The sulfate-rich simulant (MGS-1S) exhibited the best results. The major
phases of MGS-1S are: gypsum, plagioclase, basaltic glass, pyroxene, and olivine. Temperature and
the initial pH seem to be the dominant factors affecting P sorption. Equilibrium between sorbent
and AS was achieved between five and seven days, as indicated by kinetic experiments. Isothermal
experiments at 25 0C with AS of different P concentrations displayed a linear correlation between
adsorption capacity (q) and P-concentration (r2=0.98). Maximum q was observed at 8.5 and 27
mg/g for AS and HU experiments respectively, when 5 g/L of initial sorbent concentration was
used. X-ray diffraction (XRD) of the sorbents treated with AS showed the presence of the newly
formed phases berlinite and brushite. Perhaps due to hydrolysis of the pre-existing illite,
aluminum bound with the solution’s phosphates, forming berlinite and buffering AS’s pH to lower
values. Formation of brushite is possibly indicative of gypsum (predominant phase in the raw
material) dissolution subsequently releasing sulfate anions. In a similar approach, XRD evaluation of the sorbents treated with HU revealed the newly formed phases calcite and hannayite.
Phosphate and ammonia ions were likely to bind to the sample and were precipitated within
newly formed calcium-bearing phases.
These experiments form a preliminary study of Martian soil simulants, and initial results indicate a
possible use of Martian soils as waste recipients or as fertilizers in future missions
Petrological and geochemical evidence for a hot crystallization path and a recharge filtering bypass at Antimilos, Milos volcanic field, Greece
No full textAntimilos volcano in the South Aegean Volcanic Arc, Greece, comprises an andesite–dacite suite that follows a distinct evolutionary path than the main edifice of the Milos volcanic field, despite their proximity. Petrographic and geochemical analyses reveal that basaltic andesite to low-Si dacite lavas have similar phenocryst assemblages that indicate crystallization from hot, relatively dry magmas in an upper crustal storage region. Rare antecrystic high-Mg# clinopyroxene cores with low Y, low Dy, and high Sr contents record the cryptic involvement of amphibole, a phase nominally absent from the erupted products, in the deeper parts of the plumbing system. Low temperature antecrysts with textures recording various degrees of disequilibrium suggest a protracted history of interaction between the upper crustal reservoir and deeper mafic melts, forming mobile hybrid magmas that consequently erupt as highly mingled, crystal-rich lava domes. Antimilos magmas seem to have escaped recharge filtering in the upper crust and prolonged stalling, which is the process that is probably responsible for the paucity of mafic eruptions in the rest of the Milos volcanic system. Large extensional structures offshore of Antimilos promote rapid ascent of mafic melts, inhibiting prolonged stalling and interaction with the arc crust. This model highlights the dominant role of the regional stress field in generating petrologically distinct suites in the marginal parts of some volcanic fields.</p
