Sphalerite from seven deposits in the Madan ore field shows a wide colour range related to variations in trace-element composition. Samples were analysed by EPMA and LA-ICP-MS to characterise major and trace-element composition. Marmatite from higher-temperature stages is enriched in Fe, Mn, Co, Cu, Ga, Ag and Pb, while cleiophane from later lower-temperature stages contains higher Cd, Hg, Sn and In. Colour is mainly controlled by Fe and Mn: at low Fe contents sphalerite may appear red or green, while increasing Fe causes progressive darkening through greenish brown and brown to black. Red occurs only in Fe-poor compositions with elevated Sn and Cu; green arises from combined low-to-moderate Fe and trace Co. Correlations indicate simultaneous competitive and coupled substitution processes. The colour reflects the chemical and paragenetic evolution of the ore-forming system.
An initial study on the phase-mineral composition and contents of 35 critical elements (CE) in industrial sunflower shells fly ash (SSFA) was conducted on the basis of mineralogical and chemical analyses, as well as leaching procedures. The phase-mineral composition of SSFA includes amorphous matter, arcanite, sylvite, K carbonate, and gypsum. Most CE in SSFA show lower concentrations compared to the Clarke values for lithosphere, sedimentary rocks or coal ash; however, Bi, Cu, Mg, and P in SSFA reveal contents higher than those above. The water-soluble fraction of SSFA has high concentration of Li. Hence, Bi, Cu, Li, Mg, and P (particularly Bi, Li, and P) could have industrial significance for their potential recovery. Additionally, the alkaline character and enrichment of nutrients and bioavailable elements such as K, P, Ca, Cu, Mg, Mo, and Zn in SSFA are promising for the production of soil fertilizers or conditioners.
The Alpine-Himalayan orogenic belt is one of the longest geological structures in the world. Along with several parallel or sub-parallel branches, the central structure extends from the Alps to the Himalayan peaks across SE Europe and the Near and Middle East to the Indian sub-continent. The focus of this article is the section from the Alpine Mts. to the Zagros Mt. Range, where karst aquifers' presence is much greater, and they are utilised more frequently than in the Indian sub-continent. The carbonates in the north-western "European sub-unit" as well as carbonate and evaporitic rocks in the "Asian sub-unit" in the south-eastern parts of the belt are widely present, extending over 20-30% of the land surface. Due to the wet climate and presence of highly karstified rocks, certain countries in the Alpine region are among the richest in the world concerning water availability: in Montenegro, approximately 21,000 m(3) of water per year is available to each citizen, while Bosnia & Herzegovina and Croatia utilise just 1-2% of their water resources. In contrast, because of the arid climate and extended periods of drought, many areas of the Zagros region, such as Iraq or southern Iran, where karst aquifers are sometimes even the sole source for local potable water supply and irrigation of fertile lands, experience water shortages.
The present paper is an enlarged version of the lecture of the author held on December 10, 2025, at the Jubilee Conference on the occasion of the 100 years since the foundation of the Bulgarian Geological Society. We discuss the role of the geopolitical background of the newly-established Third Bulgarian State after the liberation on the development of the Bulgarian society, economy, and sciences. The foundation and the evolution of the Bulgarian geosciences as a national system of education, scientific research, national geological survey, and establishment of the grounds for mining, geology, and hydrogeological research and public water supply are controlled both by the geopolitical background with the popular enthusiasm of the Liberation and the Unification, and the defeats in the Second Balkan War, the First World War, and the following deep cleavage and tumults in the society in the years 1918-1930. The other major factor for the evolution of the National Geoscientific System has been the evolution of the geosciences on the international scale. The economic development of the world and the four industrial revolutions are regarded as the basis for the evolution of the sciences, the geosciences in particular. The foundation of the Bulgarian Geological Society one hundred years ago by a few geologists, teachers, mining engineers, and naturalists, exactly in these turbulent times was a real achievement with a great importance for the geosciences in this country and added the last element to the national system-the active role of NGO. The evolution of Bulgarian geology passed through several stages determined by the political and economic development although not necessary coinciding with its principal moments. Other discrepancies exist between the establishment of the Bulgarian Geological Society and its evolution with the evolution of Bulgarian geology. A comparison between the two evolution lines is illustrated in the figure. These discrepancies are controlled to a great extent also by personal factors as the erudition of the rulers and statesmen (or their ignorance); the interests and knowledge of the leaders of the geological community and their influence in the political circles and the society; the outreach of the geosciences in feeding the common interests. The examples are numerous. Special attention is given to two major defeats in the newest history: the destruction of the geosciences' place in the secondary education more than 50 years ago and its gradual decline, and the liquidation of the Bulgarian National Geological Survey (Committee of Geology) in 1997. The restoration of these two pillars of the national geosciences are the major goals of the geological community united by the Bulgarian Geological Society. Other important aims concern the outreach in all forms; the work for the preservation and popularization of the geological heritage; the amelioration of the links with the other geological societies in the Balkans, Europe, and the World; a better publication policy coordinated with the addressees (the international community, the Bulgarian geologists, and the vast circles of society). The further studies of the regional geology of Bulgaria and the Balkans, the complex research and synthesis of the geological knowledge and its application in the practical research for the benefit of the country are another major task. The Bulgarian geologists are able to answer the needs of the society, and to contribute to the sustainable development of Bulgaria. Farewell!
Unlike traditional spinel deposits, spinel was discovered in a technogenic agglomerate within a hydrogen production reactor, where natural gas is converted into hydrogen. The facility is located at LUKOIL Neftochim Burgas AD and was constructed in 1982. The last catalyst loading with SK-201-2 (Haldor Topsoe) was performed in 2005. In 2015, the unit was mothballed. In 2023, it was restarted with the feedstock partially replaced by LPG. In 2025, scheduled reloading of the reactors was carried out. MgAl2O4 and CuAl2O4, together with quartz, were identified via XRD analysis in druses removed from reactor 303, resembling natural mineral formations.
The Permian S-type granites in the Gemeric Unit of the Western Carpathians have no analogues in the basement of the nearby Eastern Alps and Bohemian Massif. Their initial position should be searched in the south and southwest before the large Tertiary eastward shifting of the Western Carpathians along with Alps and Pannonian within the ALCAPA megaunit. The age, specific crustal character, metallogeny of the Gemeric granites prompt regional-scale search of granite analogy with close in age, geochemistry and metallogeny in other fragments of the Variscan orogen elsewhere in Europe and North Africa (e.g. Marocco, West Europe, Balkans). A possible origin of Gemeric granites on continental arc is presented and discussed.
A quantitative phase analysis of an original yellow paving stone from the city center of Sofia has been conducted based on various chemical analyses and powder X-ray diffraction in combination with the data processing using the Rietveld method. Considerations regarding phase formation processes occurring during the manufacturing process have been presented. The obtained data were used as a benchmark in subsequent studies. Laboratory syntheses of ceramic products with Bulgarian marls as the main raw material have been carried out. The results were compared with the reference values. The influence of various parameters such as: temperature, duration and additives on the mass transfer, directions of chemical reactions and phase composition of the final products has been demonstrated and discussed. Evidence has been obtained for the suitability of Bulgarian marl raw material for the production of high-quality ceramics of the "yellow" paving type.
Earthquakes are viewed as a disaster that brings destruction, suffering, and death. The actual seismic event, however, occurs at the hypocenter, where the movement of rock blocks or layers along a friction surface produces friction, seismic waves, and temperature and pressure quickly reach very high values. The energy generated in the earthquake zone deforms, fragments, disintegrates and melts the rock material, which after the movement stops recrystallizes into new rocks, an example of which are eclogites. The S- and P-seismic waves propagating outside the zone also cause, but weaker deformations, of a rhythmic nature, reflected in petrographic textures and surface features changes in the relief. The triad: movement - friction - seismic waves is a strong energy factor that transforms and renews the earth's matter and characterizes the earthquake as an evolutionary process - destructive and creative.
This study presents a comparative characterization of greisen-like hydrothermal alteration zones at the Babyak deposit and the rare-metal pegmatite exposed at the Vishteritsa quarry in the Western Rhodopes, Bulgaria. Both systems formed during the early Eocene (similar to 50-53 Ma) and are spatially proximal (similar to 21 km), allowing a meaningful genetic and geochemical comparison. Greisen zones at Babyak occur as quartz-muscovite-fluorite veins and irregular bodies, hosting molybdenite and pyrite, with muscovite enriched in W, Sn, Sc, Ba, Ga, Nb, Ta, Ti, Li, B, Zn, and Rb. Vishteritsa pegmatites exhibit complex internal zoning, with muscovite showing elevated Li, B, whereas the Vishteritsa micas are more homogeneous. Both systems show potential for critical and strategic elements, including Li, B, Nb, Ta, Sn, W. These findings provide a basis for future exploration and resource assessment in the region.
In this work, we present data for the geometry of the epithermal vein system in the Krumovgrad ore field, combined with 3D modelling of the metamorphic foliation of the NE-flank of the Kesebir-Kardamos dome. The structure of the flank is characterized by an asymmetric anti-and-synformal pair, suggested to be the product of exhumation in the footwall of a corrugated detachment fault. The epithermal vein system reveals an architecture consistent with partitioning of deformation during exhumation and detachment faulting.
The study presents new data on the behavior of more than 40 elements in zones of hydrothermal alteration with increasing intensity at Sharlo Dere exploration area, Chelopech high-sulfidation deposit. Based on the main mineral assemblage, petrographic and geochemical signatures the following alteration zones were distinguished in the diorite porphyry host rock: "hematitic", propylitic, propylitic-sericitic, quartz-sericitic and advanced argillic (AAA). The weakly altered "hematitic" rocks are characterize with preserved primary plagioclase and hornblende, whereas with increasing intensity of alteration these minerals are replaced by sericite, carbonates, chlorite, sulphides, dickite and clay minerals. Whole-rock geochemistry reflects the increasing intensity of alteration with relative enrichment of Pb and Sr and depletion of Cs, Rb, K, Y, MREE-HREE. The most altered AAA zones are characterized with strong depletion of MnO, MgO, CaO, Na2O, MREE-HREE and HFSE. Indicative element ratios of the AAA zones are Rb/Sr, Y/Sr, Sr/P2O5 that can be used as pathfinders in geological exploration.
During the XXXII Bulgarian Antarctic Expedition (2024-2025), a geological sampling of the ocean floor was carried out for the first time on board of the research vessel NAVAL RSV 421 "St. St. Cyril and Methodius" through a gravity tube in the deep-sea waters of the Bulgarian base on Livingston Island, Antarctica. With the logistical support of the ship's crew, the first geological sample of deep-sea sediments was obtained through a gravity tube from the board of NIK_421. In parallel, a biological grab sample from the same site revealed the presence of abundant infaunal polychaete tubes constructed from agglutinated clay particles, along with a few sessile tunicates, indicating a close link between the fine-grained depositional setting and the benthic community structure.
During XXX Bulgarian Antarctic Expedition, a detailed ground magnetic survey was conducted of the area around the Bulgarian Antarctic Base "St. Kliment Ohridski" on Livingston Island, South Shetland Islands, which aimed to continue the previously conducted ground magnetics from 1997 and 2002. The magnetic method was used at investigating the physical properties of the geological formations under a thick ice layer and linking the obtained results with the geological observations along the coastline in the immediate vicinity. The results outlined clearly three isometric magnetic anomalies that are most likely related to intrusive bodies. In the northernmost observed magnetic anomaly, smaller magnetic lineaments radiate outward which are with hypothetical dyke origin. The 3D model distinctly isolates a deep root of the anomalies, possibly related to the shallow magma chamber. The outlined anomalies correspond well with the dyke bodies in the vicinity associated with precious metals mineraliza-tion in the area around Sinemorets peak.
The interpretation of numerous photographs and videos in the high mountainous area of the peak Vihren (with its 2914 m the third on the Balkans) allowed the author to reveal the presence of a carbonatic clastic formation unknown up to now. It covers considerable areas previously mapped as amphibolite facies marble occupying the highest parts of the Rhodopian metamorphic complex. The carbonatic clastics cover the whole granulometric range from megabreccia to calcarenite. The big fragments are built of different calcitic and dolomitic marbles sometimes forming olistoliths. The formation suffered intense ductile (mostly in shear zones) and brittle deformations, the strongly sheared calcarenites and conglomerates transformed into calcareous schists. The carbonatic clastic formation has a supposed thickness of about 500 m and is widespread also in the eastern limb of the Sinanitsa Antiform the peak of the same name included. The age of the carbonatic clastic formation could be most probably Paleocene- early Eocene or pre-Paleocene.
It is believed that the Devene fault in northwest Bulgaria is a seismogenic fault. However, this belief contrasts with the lack of known historical earthquakes and doubtful tectonic landscape. In order to contribute to the solution of this apparent contradiction, we performed a site-specific study on the Skat floodplain, using electrical resistivity profiling with multiple electrode arrays for improving data quality. On the basis of modeled resistivity distributions in the shallow depth, we found implicit evidence for fault movements during the late Quaternary, recorded in disturbed fluvial layers together with differences in fluvial deposition on both sides of the fault.
Apatites from several potassic-alkaline plutons-Svidnya, Sedamte Prestola, Lutskan, Shipka melasyenites and Shipka have been studied. Apatites from peralkaline varieties were analyzed and the results showed that they can serve as potential raw materials for several trace elements and namely Sr and REE. There is a marked correlation between the trace elements and the peralkalinity of the rocks, but also there is a variance in apatite composition from the different magmatic bodies. The most enriched in strontium and rare earth elements are the strongly peralkaline dykes of quartzsyenite and granite porphyries of the Svidnya pluton. In some pegmatoid zones and metasomatic varieties the Sigma REE2O3 and SrO in apatite reach up to 3 and 9 wt% respectively.
The new mineralogical and geochemical study shows that the manganese mineralization from the area of Kochash village, Eastern Rhodopes, is deposited as concentric layers of different sizes and crystallinity. It is com-posed of intergrowths of pyrolusite, ramsdellite, and "groutellite" as pyrolusite dominates. EMPA and LA-ICP-MS analyses show increased contents of Cu, Zn, As, Sr, Mo, Sb, Ba, W, Tl, and U, part of them being important criti-cal elements. XRF maps show that Mn, Fe, and to some extent Ca have relatively uniform distribution along the individual layers. Other elements as Si, P, Ti, Ba, and Ce are deposited in some concentric zones like undetected small grains of silicate, phosphate, titanium, and barium phases. Our study shows that the Kochash manganese oc-currence has good potential for prospecting and new assessment for certain critical elements.
Allanite from magmatic pegmatites from the Vacha River Valley, Madan Lithotectonic Unit (Rodope Massif, Bulgaria) show complex textures and chemical zoning that reflect crystallization in different parageneses and conditions. The allanite characterises by highly fractionated REE patterns, large negative Eu anomalies and high Th/U ratio, while the REE-rich epidote shows weak or absent Eu anomaly and lower Th/U ratio. On La/Sm vs Th/U diagram the allanite compositions plot in the field of magmatic allanite, while the REE-rich epidote scatter towards the metamorphic allanite. The observed wide range of Th/U from single samples makes the studied allanite suitable for U-Th-Pb dating.
Gravity inversion method, previously developed for density mapping of the basin's basement, is applied along with other geophysical techniques and geological data with the aim to improve geological interpretation of gravity data. The technique combines linear gravity-density inversion with forward modeling, while the basic application requires the accessibility of gravity anomaly and depth-to-basement data. Lateral density distribution inside the basement, presented as a profile or a map, is the result of gravity inversion. Density map is the base for mapping of different geological formations that constitute the basement. The boundaries dividing the formations of different densities were defined using semi-automatic procedures, commonly applied in the potential field analysis, and then adjusted based on available data on age and lithology of the basin basement rocks. Simplified geological map of the pre-Cenozoic basin's basement is composed for an area in the Pannonian basin nearby the city of
The Rossen monzonite to syenite pluton in the eastern Srednogorie is a part of the Late Cretaceous Apuseni-Banat-Timok-Srednogorie magmatic and metallogenic belt. Besides the multiple aplite and pegmatite dikes, the pluton hosts numerous miarolitic cavities containing diverse mineral assemblages indicative of a transition from late-magmatic to hydrothermal conditions. The formation of K-feldspar was followed by crystallization of graphic quartz-feldspar intergrowths, albite, smoky quartz, epidote, prehnite, chabazite, and late calcite and barite. Geochemical patterns reveal significant enrichment in incompatible elements: K-feldspar and albite contain Sr, Ba, Rb, Cs and Ga; epidote-group minerals incorporate Sr, Ti, LREE and Sc; titanite and apatite are enriched in Y, Nb, Ta, Zr, Th, U, and REE. The Rossen miarolitic cavities thus represent small-scale geochemical reservoirs, demonstrating the capacity of magmatic-hydrothermal systems to concentrate critical elements during late-stage crystallization and fluid evolution.
