Supervisors info:
Τζάνης Ανδρέας, Καθηγητής, Τμήμα Γεωλογίας και Γεωπεριβάλλοντος, ΕΚΠΑ (Επιβλέπων)
Σταματάκης Μιχαήλ, Ομότιμος Καθηγητής, Τμήμα Γεωλογίας και Γεωπεριβάλλοντος, ΕΚΠΑ
Σακκάς Βασίλειος, Εργαστηριακό Διδακτικό Προσωπικό, Τμήμα Γεωλογίας και Γεωπεριβάλλοντος, ΕΚΠΑ
Summary:
The Methana Volcanic Complex is an inhabited volcano at the northeastern coast of the Argolis Peninsula with its latest eruption in the Hellenistic period, circa 238 BCE. It belongs to the South Aegean Volcanic Arc and it an active volcano in the Saronic gulf area. Thus, it constitutes an ideal target for geothermal exploration. Its geothermal potential has already been observed in fumaroles and thermal waters manifestations. Hydrothermal systems and their constituent parts, such as geothermal reservoirs, fluid circulation conduits, and magmatic body intrusions are interwoven with high conductivity anomalies, which can be efficiently located by the Magnetotelluric method.
The objective of this study is to provide a more definite imagery of the interior of the Methana Volcanic Complex, by re-evaluation and reinterpretation of legacy magnetotelluric data with advanced techniques. We attempted to shed light, or strictly speaking electromagnetic energy of frequencies quite lower than light, to the geoelectric structure, the functional characteristics, and the geothermal potential of the volcano.
The evaluation, quality check and correction of the data, are summarized at the test for the existence of the geoelectric structure that produces them, and which is based in the analytic representation of the impedance tensor with the Cauer expansion, and the basic physical principles of the magnetotelluric method (causality and passivity). Thereafter, 3-D inversions of MT data were conducted with topography, bathymetry, and the presence of seawater all taken into account.
Two resulting models are presented herein. One containing as input data only the off-diagonal elements of the impedance tensor (Model I) and one containing the full tensor (Model II). Both models revealed three main high conductivity structures, interpreted as geothermal reservoirs, one below the central part of the peninsula (C1), one at the southern part (C2), and one quite shallower at the northwestern part (C3). The results indicate that all structures are voluminous (especially C1 and C2 structures), are located at shallow depths, and are highly related to the area’s contemporary tectonics, namely the W-E R-shears (R), the NW-SE R΄-shears (R΄), and the WNW-ESE NE dipping normal faults (F1). R΄-shears appear to play a key role in the link between the springs of Palea Loutra and Nea Loutra, and the connection between the C1 and C3 structures. Finally, between the two models, Model II provides a better delineation of the geothermal fluids circulation and spreading along the R, R΄, and F1 faults and also enhanced former assumptions that the reservoirs have a common source of provision and replenishment of thermal waters.
Keywords:
Methana, Volcanic Complex, Geothermal Energy, Magnetotellurics, 3D-Inversion
