Geothermic Status of Thermopylae - Anthili Area in Fthiotida Prefecture

Μεταξάς, Α.; Varvarousis, G.; Karydakis, G.; Ḏotsika, Elissavet; Papanikolaou, George

doi:10.12681/bgsg.11426

Cited by 5 publications

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“…The geothermal gradient measured from geothermal exploration boreholes in the Sperchios basin, approx. 50 km west of Arkitsa, is 35 °C/100 m (Metaxas et al, 2010). Similar measurements at Kamena Vourla indicate 46 °C at 200 m depth (Mendrinos et al, 2010).…”

Section: Geology and Tectonic Settingsupporting

confidence: 57%

“…This interpretation results in the following parameters: k0 = 2.514 x 10 9 μm 1 n ⁄ s -1 , 1/n ≈ 3 and H = 173.6 kJ mol-1 (Covey-Crump, 1997). To assess the potential for fluid-assisted post-seismic grain growth due to the ambient temperature at depth, we consider the borehole temperatures from the outcrop areas (Metaxas et al, 2010;Papoulis et al, 2013;Lambrakis et al, 2014). We assume a geothermal gradient of 65-75 °C/km and a typical seismogenic crustal depth of 3-5 km (Scholz, 1988) resulting in an ambient temperature of about 300 °C.…”

Section: Nanostructuresmentioning

confidence: 99%

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Nanomechanics of hydrous, seismogenic crustal faults

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Samenvatting General introduction ReferencesChapter l: Mechanisms of fault mirror formation and fault healing in carbonate rocks Abstract 1.1 Introduction 1.2 Geological Setting 1.3 Methods 1.4 Results 1.5 Discussion 1.6 Conclusions Acknowledgements References Supplementary material Chapter 2: Crystal-plastic deformation in seismically active carbonate fault rocks Abstract 2.1 Introduction 2.2 Geology and tectonic setting 2.3 Methods 2.4 Results 2.5 Discussion 2.6 Conclusion Acknowledgements Supplementary material References Chapter 3: Fluid-induced phase transformations explain weakening in crustal carbonate faults Abstract 3.1 Introduction 3.2 Methods and materials 3.3 Results of high-velocity experiments 3.4. Results of low-velocity experiments 3.4 Discussion 3.5 Conclusion References Chapter 4: Formation of a silicate fault mirror under hydrous conditions -The Dixie Valley fault Abstract 4.1 Introduction 4.2 Geological setting 4.3 Methods 4.4. Results 4.5 Discussion 4.6 Conclusion References

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Section: Geology and Tectonic Settingsupporting

confidence: 57%

Section: Nanostructuresmentioning

confidence: 99%

Nanomechanics of hydrous, seismogenic crustal faults

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“…Subduction-related back-arc volcanism, combined with extensional tectonics caused by rollback of the Hellenic subduction zone (Thomson et al, 1998), results in a high geothermal gradient across the Aegean region (Lambrakis et al, 2014;Papachristou et al, 2014). The geothermal gradient measured from geothermal exploration boreholes in the Sperchios basin, ∼50 km west of Arkitsa, is 35 °C/100 m (Metaxas et al, 2010). Similar measurements at Kamena Vourla indicate 46 °C at 200 m depth (Mendrinos et al, 2010).…”

Section: Geology and Tectonic Settingmentioning

confidence: 60%

Crystal-plastic deformation in seismically active carbonate fault rocks

Ohl

Nzogang

Mussi

et al. 2021

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Seismic slip and aseismic creep commonly occur in distinct portions of the lithosphere due to the different dependencies of the underlying deformation mechanisms on conditions such as pressure and temperature (Scholz, 1998). Frictional failure involves dilatant processes facilitated by low confining pressures at shallow depths (Sammis & Ben-Zion, 2008;Sammis et al., 1987), whereas viscous deformation occurs by thermally activated processes promoted by higher temperatures at greater depths (Bürgmann & Dresen, 2008;Sibson, 1982). However, the temperature increase through shear heating during seismic faulting (Rice, 2006) challenges this strict separation by potentially activating temperature-dependent deformation mechanisms, such as crystal plasticity and diffusion creep (Nielsen, 2017). Depending on the material, melting, or decomposition reactions can also occur at high temperatures, leading to severe microphysical changes that severely alter the mechanical behavior of faults (Di Toro et al., 2011;Niemeijer et al., 2012). The main factor limiting the operation of crystal plasticity in the brittle regime is the extremely short duration of the temperature increase during and after fault slip. Thermal models predict a temperature drop through thermal diffusion within one second after sliding ceases to a value similar to the background temperature (Demurtas et al., 2019;Di Toro & Pennacchioni, 2004). Therefore, a key objective of earthquake geology is to assess the extent to which thermally activated processes impact fault structure and properties e.g., modifying the microstructure or activation of deformation mechanisms, during the short interval of coseismic slip.Deformed carbonates from principal slip zones of natural and experimental faults commonly exhibit crystallographic preferred orientations (CPOs) (

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“…Subduction‐related back‐arc volcanism, combined with extensional tectonics caused by rollback of the Hellenic subduction zone (Thomson et al., 1998), results in a high geothermal gradient across the Aegean region (Lambrakis et al., 2014; Papachristou et al., 2014). The geothermal gradient measured from geothermal exploration boreholes in the Sperchios basin, ∼50 km west of Arkitsa, is 35 °C/100 m (Metaxas et al., 2010). Similar measurements at Kamena Vourla indicate 46 °C at 200 m depth (Mendrinos et al., 2010).…”

Section: Geology and Tectonic Settingmentioning

confidence: 99%

Crystal‐Plastic Deformation in Seismically Active Carbonate Fault Rocks

et al. 2021

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The spatial separation of macroscopic rheological behaviors has led to independent conceptual treatments of frictional failure, often referred to as brittle, and viscous deformation. Detailed microstructural investigations of naturally deformed carbonate rocks indicate that both frictional failure and viscous mechanisms might operate during seismic deformation of carbonates. Here, we investigate the deformation mechanisms that were active in two carbonate fault zones in Greece by performing detailed slip‐system analyses on data from automated crystal‐orientation mapping transmission electron microscopy and electron‐backscatter diffraction. We combine the slip‐system analyses with interpretations of nanostructures and predictions from deformation mechanism maps for calcite. The nanometric grains at the principal slip surface should deform by diffusion creep but the activation of the (0001)<1¯21¯0> slip system is evidence for a contribution of crystal plasticity. A similar crystallographic preferred orientation appears in the cataclastic parts of the fault rocks despite exhibiting a larger grain size and a different fractal dimension, compared to the principal slip surface. The cataclastic region exhibits microstructures consistent with activation of the (0001)<1¯21¯0> and {101¯4}<2¯021> slip systems. Postdeformational, static recrystallization, and annealing produce an equilibrium microstructure with triple junctions and equant grain size. We propose that repeated introduction of plastic strain and recrystallization reduces the grain size and offers a mechanism to form a cohesive nanogranular material. This formation mechanism leads to a grain‐boundary strengthening effect resulting in slip delocalization which is observed over 6 orders of magnitude (μm‐m) and is expressed by multiple faults planes, suggesting cyclic repetition of deformation and annealing.

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Geothermic Status of Thermopylae - Anthili Area in Fthiotida Prefecture

Abstract: The purpose of this study was the discovery, identification and evaluation of directly exploitable geothermal fields, in the Thermopylae -Anthili area (100km 2 ).

Cited by 5 publications

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Nanomechanics of hydrous, seismogenic crustal faults

Nanomechanics of hydrous, seismogenic crustal faults

Crystal-plastic deformation in seismically active carbonate fault rocks

Crystal‐Plastic Deformation in Seismically Active Carbonate Fault Rocks

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