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This paper focuses on the structural and finite strain analysis of the Pelagonian nappe, the HP/LT Ampelakia unit, and the Olympos-Ossa unit in the Olympos-Ossa mountainous area in order to better understand the exhumation history of the Ampelakia unit and the underlain Olympos-Ossa unit. Two main stages of Tertiary deformation were revealed, related to nappe stacking and exhumation processes. During the Paleocene–Eocene crustal subduction, HP/LT metamorphism, compression, and nappe stacking were developed progressively. This D1 stage was terminated with the final SW-ward emplacement of the Ampelakia and Pelagonian nappe on the Olympos-Ossa unit during the Eocene–Early Oligocene. The next stage of deformation, D2, was developed during the Oligocene–Miocene following the orogenic nappes stacking. D2 was considered an extensional event, related to metamorphic isothermal decompression, nappes tectonic denudation, crustal uplift, and final exhumation of the Ampelakia unit and the Olympos-Ossa unit as a tectonic window. The calculated finite strain ellipsoids indicate a main flattening type strain geometry and middle strain intensity, increasing along the nappe contacts. The quartz C-axes diagrams also reveal a flattening type of deformation and non-coaxial flow towards the southwest and northeast at the western and eastern flanks of Olympos-Ossa Mountain, respectively. The calculated Wk vorticity number ranges from 0.23 to 0.93.

Caves serve as time capsules, preserving significant markers of tectonic activity and offering insights into geological history. Fault geometries and past activations found in caves can be correlated with known deformational events in the broader area, temporally delimiting the speleogenesis. More specifically, cave passage formation is suggested to be affected by the regional stress-field. The Asprorema Cave in Northern Greece is a typical example of a fracture guided cave, with passage geometry influenced by relative sidewall movements, revealing these discontinuities as faults. This study constructs the timeframe and conceptual model of speleogenesis in relation to tectonic events, geomorphological evolution and hydrological zones, and verifies its relation to the stress-field. Active tectonics, mineralogy and cave geomorphology are investigated. Results suggest syntectonic speleogenesis under phreatic and epiphreatic conditions. The absence of corrosion on fault slip surfaces implies recent activations post cave’s shift to the vadose zone. Structural analysis identifies three main neotectonic phases: NNW-SSE striking faults (oldest group of structures), NE-SW striking faults with dextral strike-slip movement (post-middle Miocene), and NE-SW striking normal faults indicating extensional stress-regime (Quartenary). The last two phases affect cave passage shape causing wall displacement, highlighting passage formation along discontinuities perpendicular to the horizontal minimum stress axis.

The stibnite mineralization at Rizana (Kilkis ore district; Serbo-Macedonian metallogenic province; northern Greece) occurs along a NE–SW-trending brittle shear-zone, which transects a two-mica and an augen-gneiss of the Vertiskos Unit. Barren Triassic A-type granites and satellite pegmatites and aplites, as well as Oligocene-Miocene plutonic, subvolcanic and volcanic rocks that are variably hydrothermally altered and mineralized, outcrop in the broader region. The mineralization appears as veins, discordant lodes and disseminations. Veins and discordant lodes exhibit massive and brecciated textures. Historic underground mining (1930s–1950s) produced 9000 t of stibnite ore, grading 40% Sb on average. The main ore mineral assemblage includes stibnite + berthierite + sphalerite + pyrite + chalcopyrite + native antimony and traces of wolframite, galena, tetrahedrite, marcasite, pyrrhotite, arsenopyrite, realgar, native arsenic and native gold. Quartz, minor barite and ankerite are the gangue minerals. Sericitization and silicification developed along the shear-zone, forming hydrothermal halos of moderate intensity in the two-mica gneiss. Locally, valentinite, goethite and claudetite are present due to the supergene oxidation of the stibnite mineralization. Bulk ore geochemistry shows enrichments in specific elements including As, Au, Cd, Se, Tl and W. Fluid inclusion microthermometry showed that the mineralization was formed under a limited range of temperatures and salinities. The fluids had low to slightly moderate salinities (6.6–8.1 wt% equiv. NaCl) with low homogenization temperatures (217–254 °C, with a maximum at 220 °C).

The coastal area of the Kavala district, Northern Greece, is characterized by minerals enriched in rare earth elements (REE). The present study focuses on the mineralogy of the black sands from six different locations and the comprehensive mineral chemistry of the REE-bearing minerals, allanite-(Ce), epidote, monazite, thorite, zircon and titanite. Allanite-(Ce) is the most important carrier of light REE (LREE) in the studied black sands, reaching up to 23.24 wt % ΣREE. The crystal chemistry of allanite-(Ce) transitions into ferriallanite-(Ce), due to the significant involvement of Fe3+. High resolution backscattered electron (BSE) images were used to identify zoning that corresponds to variations in REE, Th and U. These modifications follow the exchange scheme: (Ca + (Fe3+, Al))−1(LREE, Y, Th, U + (Fe2+, Mg, Mn))+1. Epidotes may also contain up to 0.5 REE3+ apfu. Monazite and thorite are found as inclusions in allanite-(Ce) and are enriched in Ce, La and Nd, together with Th and U. Some zircons are enriched in Hf, while some titanites host Nb and V.