Sotirios Kokkalas

• Professor
• Professor at University of Patras

The structural style of the fold-and-thrust belt in the western part of the Hellenic foreland in an area offshore the Zakynthos Island is assessed on the basis of two lithoseismic profiles, earthquake data and field data in the broader area. The compressional deformation in the area is due to the late phases of subduction and collision between Aege...

In the Aegean area, distinct fault patterns with their associated stress regimes are evidenced along a curved convergent plate boundary. In this article, we analyze and review late collisional and extensional structures in five structural regions along the External Hellenides orogenic belt in order to define, primarily, the evolution of onshore bas...

The Aegean region constitutes the overriding plate of the Africa–Eurasia convergent plate system, in the eastern Mediterranean. To explain the fault kinematics and tectonic forces that controlled rift evolution in the Aegean area, we present fault-slip data from about 900 faults, and summarise the structural analyses of five key structural “provinc...

A distinct spatial relationship between surface faulting, magmatic intrusions and volcanic activity exists in the Aegean continental crust. In this paper, we provide detailed structural observations from key onshore areas, as well as compilations of lineament maps and earthquake locations with focal plane solutions from offshore areas to support su...

Submarine gravity flows on carbonate platform slopes lead to the deposition of calciturbidites and calcidebrites in adjacent deep-water basins. Under certain conditions, morphological highs can serve as sediment sources and influence sediment distribution. This study aimed to identify such gravity flow deposits within Lower Cretaceous–Eocene carbon...

The concealed Molai Zn-Pb±(Ag,Ge) stratiform deposit in southeastern Peloponnese is hosted in Triassic intermediate tuffs, ignimbrites and subaerial andesitic flows. The host rocks display trace element signatures of a Supra-Subduction Zone (SSZ) setting. Three ore-forming stages are recognized, with stages I and II related to formation of the epig...

The Patras Gulf Pockmark field is located in shallow waters offshore Patras City (Greece) and is considered one of the most spectacular and best-documented fluid seepage activities in the Ionian Sea. The field has been under investigation since 1996, though surveying was partially sparse and fragmentary. This paper provides a complete mapping of th...

The present study examines the imprint of salt tectonics on carbonate depositional patterns of the Ionian zone platform edge to slope transition. The study area is part of an overturned rim syncline adjacent to a salt diapir. The Ionian zone is made up of three distinct stratigraphic sequences (pre-, syn- and post-rift sequences) represented by eva...

The present figure shows an example of a naturally micro-fractured mud-dominated packstone from Wasia Formation in Ras Al-Khaimah (UAE) and its fracture aperture variation. https://rdcu.be/deGFg

The Fe-skarns from the Greek Island of Serifos in Cyclades is utilized only for the exploitation of magnetite ores while a significantly vast amount of red and yellow hematite ores remained unexploited as mining wastes. The main aim of this study is the effective utilization of such mining wastes, as active catalytic materials for various environme...

Two world-first examples of mangan oxide skarns were investigated in this study, namely the Panorama skarn of Drama and the Thapsana skarn of Paros Island, in the Rhodope and Attico-Cycladic Massifs, respectively. Transitional calcic-to-mangan exoskarn at Panorama is exposed in the garnet-epidote zone (Grt-Ep), proximal to the Panorama (micro-)gran...

Following the long-standing experience of the liquid exfoliation of graphite for the production of graphene, a number of analogous van der Waals 2D nanomaterials have been also produced and studied...

We present results from a systematic study to test whether variability in fracture properties correlates with depositional environment. The Kruja Unit forms part of the fold & thrust belt of W. Dinarides and includes a thrust-imbricate carbonate sequence overlain by Oligocene synorogenic turbiditic siliciclastics. The stratigraphic succession compr...

Anticlinal fold structures comprise common traps for hydrocarbons. Such structures are often influenced by faults and fractures that operate as either conduit to channel fluids into a reservoir or as pathways to disperse accumulated fluids out of a reservoir (Coward et al., 1998; Aydin, 2000). In order to generate reservoir scale fracture models re...

Background-Objectives. Targeting of permeable fracture horizons in hydrocarbon or geothermal fields can be aided significantly by outcrop analogue studies, which can improve the understanding of fracture characteristics and their impact on fluid flow. Most carbonate platforms show high variation in lithology, diagenetic evolution, and fracture abun...

Background The Paramythia anticline is a well-exposed structure in Epirus, NW Greece, a region intensively affected by the westward compressional deformation, acting in a continental collision setting (Kokkalas et al., 2006). The study area belongs to the Ionian zone, which is considered to comprise three distinct stratigraphic sequences: a) a pre-...

This study access the manganese mobility and its possible sources in the Thapsana Mangan Skarn deposits, in Paros, by using mass balance modelling at constant volume over distance and the Isocon method. There is an overall increase of the MnO content in the skarns over distance which is coupled with a decrease of the MnO content in the Thapsana leu...

One of the most critical stages in fault-slip data stress analysis is separating the fault data into homogeneous subsets and selecting a suitable analysis method for each subset. A basic assumption in stress tensor computations is that fault activations occur simultaneously under a homogeneous stress regime. With that rationale, this work aims to a...

Numerical, geochemical, hydraulic and thermodynamic modeling is combined with fluid inclusion and fluid chemistry analyses to shed light on the mechanisms of hydrothermal circulation, alteration patterns and ore formation of the fossilized stringer ore of the Upper Cretaceous, “Mafic-Pelitic”-type VMS hydrothermal system of Ermioni (Karakasi mine)....

A highly accurate (2-3 cm resolution) geomorphological 3D laser mapping of the Cave of Lakes was conducted in order to assess the cave’s geomorphology and its connection with the regional tectonic setting. The cave is located in north Peloponnese and its natural entrance lies at 820 m altitude. It is considered among the most aesthetic Greek caves...

This study presents a Holocene multi-proxy record from Lake Vouliagmeni, eastern Gulf of Corinth, Greece. The lake is subjected to intense climatic and tectonic forces causing stratigraphic variations with laminated sediments frequently interrupted by homogenous sections and event deposits. Lamination couplets consist of aragonite layers alternatin...

The age, type and geotectonic setting of the Ermioni VMS are explored. Although obscured by post-ore deformation and metamorphism, the Ermioni VMS is genetically and spatially related to hydrothermally altered volcaniclastic rocks and arkoses at the footwall, and turbidites at the hangingwall. The Ermioni VMS deposits occur at Karakasi, Roro and Ca...

Published heterogeneous fault-slip data inverted by Federico et al. (2014) with the best-fit stress inversion methods provided by FSA (Celmer, 1999) and Win-Tensor (Delvaux, 2011) software are re-examined and analyzed with theTR method (TRM) (Tranos, 2015) for defining crucial differences in unraveling the paleostress history of a polyphase deforme...

The Monte Carlo method simulates the optimal conditions of ore formation. The results suggest that the predicted pressure and chlorine contents are almost identical with the ones observed. Temperature is predicted to be higher by ~30ºC whereas salinity and CO2 are predicted to be lower (~3 wt. % equiv. NaCl, ~2.5 moles %). The main tectonic trend i...

The Kallianos Au-Ag-Te deposit in Evia Island (Greece) comprises sixteen syntaxial veins that intersect the schists and marbles of the Cycladic Blueschist Unit. The veins are filled with quartz-I and quartz-II, contain two hypogene ore stages (stages I and II), and are surrounded by infrequent muscovite-chlorite alteration zones. A magmatic origin...

Although previous exploration in Lavrion included the Pb-Zn-Ag carbonate-replacement deposits, future targeting in Lavrion may focus on the world-class mineralization “Filoni 80”. These ore deposits are temporarily and spatially related to the 10 to 8 Ma “Plaka’s” granodiorite, as well as its associated sills and dikes. “Filoni 80” epithermal, Pb-Z...

Amfilochia Bay (Eastern Amvrakikos Gulf, Western Greece), a complex marine area affected by tectonism, was investigated for seabed seepage manifestations and for possible inter-relationships between shallow gas accumulations and hypoxia. For this purpose, an integrated research methodology that combined geophysical, geochemical, and hydrographic su...

The Semail ophiolite located in the eastern part of the Arabian platform preserves remnants of ocean plate stratigraphy and related metamorphic sole. To understand the petro-tectonic evolution of a metamorphic sole during subduction to obduction process, here we investigate the garnet metagabbros from the metamorphic sole and the tonalites which in...

The garnet-epidote zone in the Xanthi Fe-skarn at the Rhodope Metallogenetic Massif, northern Greece, includes noteworthy cerium mineralization manifested by the presence of epidote-(Ce) containing up to ~130,000 ppm ΣREE and ~ 87,000 ppm Ce. The REE skarn represents a late evolutionary phase of the Xanthi's Fe-skarn in a collisional setting.- The...

Summary- The porosity and permeability structure of fractured reservoirs is highly heterogeneous, however typical subsurface data are unable to quantify this heterogeneity across scales of analysis that are most relevant for fluid flow. Comprehensive analysis of outcrop analogues can provide detailed, quantitative characterisation of the fracture n...

Most carbonate fractured reservoirs show high variation in lithology, diagenesis, fracture intensity, orientation and connectivity. This high degree of heterogeneity can have a significant impact on reservoir quality and sustainability of production. Outcrop analogues are key elements in the understanding of reservoir architecture and heterogeneity...

Abstract The Kallianos deposit at south Evia in the northern part of the Attico-Cycladic Metallogenetic Massif, compose of carbonate-replacement and vein-type ores. The Au-Ag-Te vein mineralization associates with sixteen ore-bearing syntaxial quartz-I and -II veins that intercept the schists and marbles of the Cycladic Blueschist Unit. The veins c...

Several types of felsic granitoid rocks have been recognized, intrusive in both the mantle and the crustal sequence of the Semail ophiolite. Several models have been proposed for the source of this suite of tonalites, granodiorites, trondhjemites intrusions, however, their genesis is still not clearly understood. The sampled Dadnah tonalites that i...

Mn-skarn ore deposits are relatively infrequent worldwide. A typical example of a Mn-skarn in the Attico-Cycladic Metallogenetic Massif is located at the mining area of Thapsana, Paros Island. The skarn occurs adjacent to the Thapsana, highly sericitized, biotite-garnet-tourmaline-lepidolite leucogranite apophyses of the Paros granitoid and related...

Plagiogranite intrusions are common in the Khor Fakkan block of the Semail ophiolite, where the mantle sequence is predominant. Several models have been proposed for the source of these leucocratic intrusions, but their genesis is still under debate. The examined plagiogranites are characterized by 68 wt. % SiO and display volcanic-arc granite affi...

The 1934 Ms 6.6 Hansel Valley, Utah, earthquake produced an 8-km-long by 3-km wide zone of north-south–trending surface deformation in an extensional basin within the easternmost Basin and Range Province. Less than 0.5 m of purely vertical displacement was measured at the surface, although seismologic data suggest mostly strike-slip faulting at dep...

The 1934 Ms 6.6 Hansel Valley, Utah earthquake produced an 8-km-long by 3-km-wide zone of north-south trending surface deformation in an extensional basin within the easternmost Basin and Range province. Less than 0.5 m of only vertical displacement was measured at the surface, although seismologic data suggest mostly strike-slip faulting at depth....

A good understanding of orientation, densities and size of fractures in hydrocarbon reservoirs is very important in optimizing drilling and production strategies. Because of the increasing importance of horizontal drilling and hydraulic fracturing in recent years, extensive studies are being conducted for locating subsurface fractured zones and obt...

Clay minerals in shallow fault rocks are increasingly recognized as key to the mechanical and seismogenic behavior of faults and fluid flow circulation within the fault core and the surrounding damage zone. We therefore studied faultgouge mineralogy from samples derived from the ENE-trending Arkitsa fault zone, in east-central Greece, in order to t...

The aim of this study is to improve our understanding on the mechanical interaction and linkage process between normal fault segments. Faults grow by the process of radial propagation and the linkage of segments, as strain increases, evolving to large fault systems. For this purpose we conducted a combined field and photogeological study on two maj...

The area of Lavrion constitutes the westernmost part of the Attico-Cycladic massif where the allochthonous Cycladic Greenschist-Blueschist unit overthrusts the para-authochthonous Basal unit. The tectonic contact of these units forms a crustal scale thrust zone which is the continuation of the Evia thrust. Our research was focused on quartz-rich sc...

Granitic intrusions are common in the Khor Fakkan block of the Semail ophiolite, where the ophiolitic mantle sequence is dominant. At present, it is considered that the formation of the majority of peraluminous granitic bodies is related to the anatexis of subducted Arabian passive margin marine sediments, i.e. Hawasina and Haybi complexes, as well...

Terrestrial laser scanning (TLS) has been used extensively in Earth Science for acquisition of digital outcrop data over the past decade. Structure-from-motion (SfM) photogrammetry has recently emerged as an alternative and competing technology. The real-world performance of these technologies for ground-based digital outcrop acquisition is assesse...

The 1934 ML 6.6 Hansel Valley, Utah, earthquake produced an 8-km-long by 3-km-wide zone of north-south trending faults and fractures at the southern end of Hansel Valley in the easternmost Basin and Range Province. Surface-rupture observations indicate less than 0.5-m of vertical displacement, possibly of secondary (shaking-related) origin. In cont...

https://library.seg.org/doi/10.1190/ice2016-6512978.1

Good analogues for calibration of reservoir models should contain representative fracture properties across a wide range of scales. Capturing fracture data across multiple scales requires a range of different methods and appropriate technologies. In this study we illustrate a number of these methods, through field examples, comparing their advantag...

Datatypes from the sub-surface are often fundamentally limited, either because they are extremely sparse (e.g. borehole image logs, core, well tests), or too low resolution (e.g. seismic), and hence unable to image the vast majority of fractures that constitute most naturally fractured reservoirs. Quantitative analysis of fracture systems in outcro...

Natural fractures are increasingly recognized as an important factor in the exploration and production of hydrocarbons. Fracturing increases the porosity and, more importantly, the permeability in otherwise tight reservoirs, and also enhances the connectivity between different reservoirs units within a field. To successfully predict fracture orient...

This study investigates the tectonic evolution of the Omalos transverse zone, which served as a crustal-scale oblique ramp in the External Hellenides thrust belt on Crete island. The Omalos oblique ramp developed above an inherited Mesozoic fault zone that strikes NE-SW, oblique to the regional SSW-directed tectonic transport. During the Early Mioc...

The previously unknown Nisi Fault in NW Peloponnese was ruptured during the 2008 Movri Mountain earthquake attaining a maximum offset of 25 cm. The fault is interpreted as a branch of a flower structure above a blind strike-slip fault. We investigate the Nisi Fault seismotectonic evolution using morphotectonic analysis in order to determine whether...

Detailed geological mapping, structural investigation and amphibole chemistry analyses in southern Evia (Aegean Sea, Greece) allow us to place new constraints on the internal structural architecture and tectonic evolution of the Cycladic Blueschists. We show that the early deformation history was related to ESE directed thrusting resulting in the s...

New structural, petrofabric and palaeostress data from the Beotia area (central Greece) were used to investigate the tectonic evolution of the suture zone between the External (Parnassus microplate) and Internal Hellenides (Pelagonian microplate). Petrofabric studies of ultramafic rocks were done using conventional U-stage analysis and the electron...

In the central Aegean, the Cycladic island of Amorgos consists of two high-pressure (HP) units, the marble-rich Amorgos unit, which is correlated to the Mesozoic ‘cover’ sequence of the Menderes Massif, and the Cycladic Blueschist unit. New structural data show that the deformation history of the Amorgos HP-rocks was principally governed by early O...

The Movri Mt earthquake: understanding active deformation of the NW Peloponnese): The Mw 6.4 June 8 th 2008 Movri Mountain earthquake struck NW – Peloponnesus, Greece, caused widespread deformation and damage in buildings, as well as extensive ground hazards. Three surface ruptures were triggered by the earthquake, with the most promising for paleo...

Microstructural, petrofabric, strain and vorticity data from quartz-rich tectonites were used to investigate the kinematics of rock flow in the Evia and Ochi ductile thrust zones, formed during exhumation of the high-pressure nappes of the Attico-Cycladic Massif. The Evia thrust zone defines the base of the Styra nappe while the Ochi thrust zone de...

Combined kinematic, structural and paleostress analyses were performed to reevaluate the tectonic evolution of the southern Hellenides in western Crete. Our work shows that the structural architecture of the study area was mainly established by two contractional deformation phases. SSW-directed thrusting from Oligocene to lower Miocene times (D1 ph...

The Gulf of Corinth in Greece and especially its southeastern part is dominated by a series of step - like north facing normal faults hosting strong earthquake events. The Kenchreai fault zone, located along the Gulf's southeastern coast, is a key fault for analyzing how a north facing fault accommodates N - S extension in the back - arc region. Th...

The aim of this study is to improve our understanding on the mechanical interaction and linkage process between normal fault segments. Faults grow by the process of radial propagation and the linkage of segments, as strain increases, evolving to large fault systems. For this purpose we conducted a combined field and photogeological study on two maj...

The Movri Mountain earthquake (Mw 6.4), western Greece, was likely caused by dextral‐slip along a blind high‐angle fault, and generated a complex pattern of co‐seismic surface ruptures southwest of the Gulf of Corinth. The mapped Nisi, Michoi, and Vithoulkas rupture segments have similar lengths (5–6 km) and vertical offset on the order of 25, 10,...

Many fault surfaces are noticeably nonplanar, often containing irregular asperities and more regular corrugations and open warping. Terrestrial laser scanning (light detection and ranging, LIDAR) is a powerful and versatile tool that is highly suitable for acquisition of very detailed, precise measurements of slip-surface geometry from well-exposed...

Monitoring of active faults in urban areas is of great importance, providing useful information to assess seismic hazards and risks. The present study concerns the monitoring of the potential ground deformation caused by the active tectonism in the cities of Patras and Pyrgos in Western Greece. A PS interferometric analysis technique was applied us...

The study of paleoseismological and archaeological excavations provide clues for the evolution of Helike Fault, located along the westernmost end of the Gulf of Corinth, that displays high activity and exerts control on the landscape. In this study we present evidence from paleoseismic trenches which revealed well defined fault strands and clear co...

The Gulf of Corinth, Greece, is a 110-km-long by 30-km-wide active graben displaying strong seismicity hosted both on north and south dipping normal faults. This complex fault pattern consists of two fault populations, offshore and onshore. The offshore fault population is investigated by densely arranged seismic reflection profiles during the last...

The Gulf of Corinth, in central Greece, is a 110-km-long by 30-km-wide active graben displaying strong seismicity hosted both on north and south dipping, offshore and onshore normal faults. We made an attempt to examine and correlate the scalar properties of both populations along the gulf. We investigated the offshore fault population using alread...

The Kaparelli Fault was activated during the 1981 Gulf of Corinth earthquake sequence, producing extensive ground deformation. The main purpose of this work was to identify and date previous Late Quaternary faulting events and to resolve slip on the main trace of the Kaparelli normal fault prior the 1981 seismic event by means of paleoseismological...

The island of Crete is situated at the SE part of the high-pressure (HP) belt of the External Hellenides. It has been considered as a classical area where HP-rocks exhumed in the footwall of a shallow-dipping extensional detachment due to syn- and/or post-orogenic extension. Extensional models are primarily based on the observed metamorphic break b...

We applied terrestrial laser scanning (ground-based LiDAR) in the Arkitsa fault zone, an area of active extension along the North Evia Gulf in Central Greece. The study area includes well exposed fault surfaces with large accumulated slip and this allowed detailed measurements of the geometry of the fault planes to be acquired. Laser-scan data enab...

Petrofabric, finite strain and kinematic vorticity data were used to investigate the heterogeneous nature of ductile deformation along a 1.5-2 km thick extruding shear zone in the south Peloponnese, that formed under blueschist-facies conditions. Asymmetric quartz c-axis fabrics confirm westward thrust movements on an east-dipping shear zone and pr...

Potassium-rich volcanic rocks of the shoshonite suite are common features of postorogenic extensional settings inboard from subduction zones. Various petrogenetic processes and tectonic settings have been proposed for their origin. Early Miocene volcanic rocks of Limnos, part of the northeast Aegean shoshonite belt, show distinctive geochemical fea...

Existing failure criteria for rocks typically assume that fractures are planar and there is little available theory to explain the mechanics of fracture surfaces that are curved. This is at odds with field observations of naturally occurring fracture systems, in which individual surfaces are often observed to be significantly non-planar. Our observ...

In this article, paleoseismological studies carried out in the Aegean region during the past decade, mainly on faults occurring in mainland Greece, are reconsidered and their results re-evaluated. We focus on active normal faults and particularly on the principal seismotectonic parameters, such as the coseismic displacement associated with past eve...

In this article, paleoseismological studies carried out in the Aegean region during the past decade, mainly on faults occurring in mainland Greece, are reconsidered and their results re-evaluated. We focus on active normal faults and particularly on the principal seismotectonic parameters, such as the coseismic displacement associated with past eve...

Morphologic analysis of fault-scarps of known age, combined with data from palaeoseismological trenches, is used to determine the mass diffusivity (c) for central Greece. Seventeen scarp profiles were accurately measured, in areas ruptured during two strong seismic events: the Eliki and Kaparelli areas within the Gulf of Corinth. Application of the...

Results from palaeoseismological trenching for four active faults in Greece are presented. The main target is to determine palaeoearthquake slip and slip associated with events hosted on four active faults: two of them located with the Gulf of Corinth southern part of the Greece (Kaparelli and Eliki) and two in the northern Greece within the Mygdon...

Trench stratigraphy and morphotectonic analysis was used to examine the recent evolution of the Helike (Eliki) Plain and Eliki Fault. The entire alluvial plain of the Kerynites and Vouraikos Rivers, which cross the Eliki Fault, has subsided at rate of 1.4 mm/yr, resulting in the burial of the Late Hellenistic-Roman occupation horizons under ⩽3 m of...

Morphotectonic analysis using geomorphic indices has been developed as a basic reconnaissance tool in order to identify areas experiencing rapid tectonic deformation or estimate relative variations of tectonic activity in a specific area. We applied this analysis in Eliki fault zone, which is located in the western part of the Gulf of Corinth. Elik...

New kinematic and structural data from the tectonic windows of eastern Crete and the Dodecanese Islands combined with strain and quartz fabric analysis have enabled us to determine a detailed structural evolution of the region and to present a plate tectonic scenario for the southeast Hellenides. During the Early Mesozoic, the southeastern part of...

Morphotectonic analysis using geomorphic indices has been developed as a basic reconnaissance tool in order to identify areas experiencing rapid tectonic deformation or estimate relative variations of tectonic activity in a specific area. We applied this analysis in Eliki fault zone, which is located in the western part of the Gulf of Corinth. Elik...

In this study, we present structural, fracture orientation and fracture density (FD) data in order to quantify the deformation pattern of a damage zone that form around the slip plane of a large scale thrust fault which is located on the Ionian zone (External Hellenides) in northwestern Greece. Structural analysis showed at least two major deformat...

The kinematic similarities of small-scale structures in the Rhenohercynian Zone and the external zones of the Hellenides are illustrated. Both orogenic domains comprise asymmetric folds verging toward the foreland and are affected by extensional joints (ac and bc) associated with hybrid joints as well as with shear fractures (hkOa and hkOb). Joints...

Structural, kinematic and strain-path analyses were used to elucidate how strain was accommodated at deep tectonic levels during the exhumation of high-pressure/low-temperature (HP/LT) units of the Attico-Cycladic-Massif (ACM), which are exposed on Evia Island (West Aegean Sea, Greece). These analyses are combined with data from the structural evol...

The Kerynitis River course is critical for understanding the evolution of the East Eliki fault, the tectonostratigraphy along the fault scarp and the geoarchaeology of ancient Helike. Trench stratigraphy and morphotectonic analysis were used to examine the recent evolution of the Helike (Eliki) Plain and Eliki fault. The entire alluvial plain of th...

Synmagmatic and solid-state structures within the Naxos pluton and its rim may provide insight into the interplay between plutonism and regional deformation at upper-crustal level. Within the hornblendeSW- and NS- (Ikaria pluton) or NE- (Tinos, Serifos and Delos plutons) trending faults.

The roughly E-W trending Kaparelli-Plataees Fault is an on-shore normal fault segment located at the eastern end of the Gulf of Corinth Rift. The fault is a segment of the greater Plataees-Avlon fault zone (Beotia-Attica). It was activated during the third event of the February- March 1981 Alkyonides seismic sequence (Ms 6.7; 6.6; 6.4). The ground...