Türkiye Jeoloji Bülteni

Abstract: In recent years, artificial intelligence(AI) models have become routine in geoscience applications ranging from earthquake early warningsystems to landslide susceptibility mapping, subsurface resource modeling, and stratigraphic classification. Out performing traditional methods for predictiveaccuracy, these models increasingly mediate between observation and inference. However, this technical success raises a critical question: does high predictive accuracy reflect true geological understanding` Thispaper draws attention to the risk that the growing predictive capacity of data-driven models may overshadow the interpretive nature of geoscience andthe elucidation of actual geological conditions. Indomains where observations are sparse, uncertainty is structural, and ground truth is limited—such assubsurface interpretation and hazard assessment—models can achieve seemingly high classification accuracy by relying on mechanistically irrelevant proxies. This undermines model transferability andgeological consistency under changing environmental / tectonic conditions. Without rejecting predictivemodeling, this perspective aims to propose a conceptual and semi-formalized "assistant" framework— not introducing a new algorithm but rather a guidingstructure—that integrates geological constraints, interpretable modeling, and post-hoc geological validation to ensure that predictive performance doesnot override geological reasoning. 

Abstract: Listvenite-type silica–carbonate metasomatic alteration in the Vezirler ophiolitic mélange (northeastern Kula, western Türkiye) was screened using a lithology-masked Selective PCA workflow and complementary band ratio indices applied to a cloud-free Landsat-7 ETM+ image. Masking reduced spectral mixing from vegetation, alluvium, and non-target lithologies and increased anomaly contrast within a field-verified ROI. Ferric-iron–sensitive PC2 anomalies cluster along carbonatized/silicified serpentinites (CS-Srp) and Fe-oxide-stained silica–carbonate caps (Fscc/Cnz), consistent with hematite coatings documented in the field. Ferrous-iron responsesare comparatively subdued, indicating limited preservation of surface-expressed Fe²+ signatures under pervasive oxidation and overprinting. Hydroxyl-related patterns delineate alteration halos but weaken over strongly silicifiedcaps where diagnostic OH absorption is suppressed. Band-ratio maps (Fe³+: B3/B2; silica: B7/B5; OH-: B5/(B5+ B7)), statistically segmented using μ ± σ thresholds, reproduce first-order PCA patterns and support repeatable anomaly ranking. The results demonstrate a rapid regional screening approach relevant to alteration targeting and natural mineral carbonation analogues, while recognizing inherent limitations of the 30 m resolution, such as false positives in shaded valleys due to topographic effects and spectral dilution from mixed-pixel responses along slope transitions. Future work may integrate ASTER TIR and archival ASTER SWIR scenes acquired prior to 2008, ormodern SWIR/hyperspectral datasets, to improve mineral discrimination.

Abstract: This study presents a comparative investigation of the emplacement conditions for gabbroic intrusion sexposed on Dee and Cecilia islands, located along the South Shetland Islands to the north of the Antarctic Peninsulain Western Antarctica. Crystallization temperatures and emplacement pressures were calculated using two-pyroxene geothermobarometry, and oxygen fugacity conditions were additionally constrained based on Fe–Ti oxide pairs. Petrographically, the Dee intrusions are characterized by fine-grained, holocrystalline porphyritic textures composed of plagioclase, clinopyroxene, orthopyroxene, olivine, and opaque minerals. The Cecilia intrusion displays broadly similar mineral assemblage but coarser-grained holocrystalline granular textures. Plagioclase in the Deeintrusions predominantly exhibits normal zoning, whereas plagioclase crystals in the Cecilia intrusion commonlyshow oscillatory and locally reverse zoning, together with sieve textures and embayment structures. Two-pyroxene geothermobarometric calculations suggest that the Dee intrusions crystallized at temperatures of approximately1,030–1,090 ºC and pressures of 2.5–3.5 kbar, corresponding to relatively shallow upper-crustal emplacement.In contrast, the Cecilia intrusion yields crystallization temperatures of 1,000–1,170 ºC and pressures of 4.5–6.5kbar, consistent with deeper emplacement at mid- to lower-crustal levels. Fe–Ti oxide barometry indicates that bothintrusions crystallized under oxidizing redox conditions, with the Cecilia intrusion recording systematically higheroxygen fugacity values relative to the Dee intrusions.When field, petrographic, and mineral chemistry data are evaluated together, the Dee and Cecilia intrusionsare interpreted to represent mafic magmatic bodies emplaced at different crustal levels within the South Shetland Arc magmatic system. Future geochronological studies will lead the investigation of the timing of emplacementand further assess the relationship between the crustal evolution of these mafic intrusions and the regional tectonic framework.

Abstract: Rare earth elements (REEs) are critical raw materials used in strategic fields such as defense, energy, electronics, lasers, and sensor technologies, and particularly in the production of permanent magnets including NdFeB and SmCo types. Since the early 2000s, the global supply of rare earth elements has become dominated by China for mining, beneficiation, and separation processes, as non-Chinese producers have lost competitiveness due to high capital requirements and the costs imposed by environmental regulations. This review addresses the geological formation environments, deposit types, and global reserve–resource distributions of REEs within an integrated framework.

REE mineralization occurs within primary geological sources such as carbonatites, alkaline magmatic systems, and iron oxide copper–gold (IOCG) deposits, as well as in secondary sources including ion-adsorption clays, placers, and lateritic formations. Primary sources are generally enriched in light REEs and are characterized by high-cost production processes, whereas heavy REEs are predominantly obtained from secondary sources. Globally, REE reserves are estimated to be approximately 90–120 Mt, while potential resources are on the order of ~480 Mt, with China occupying a leading position in terms of both reserves and resources. In Europe, Greenland, Sweden, Finland, Norway, Germany, and Türkiye are among the regions with significant REE potential. In Türkiye, the principal REE areas defined at the deposit scale are the Eskişehir–Kızılcaören (Beylikova) and Malatya–Kuluncak districts. These districts are associated with alkaline magmatism and display enrichment particularly in Nd and Pr (beyond La and Ce), rendering them strategically important for NdFeB permanent magnet production. Recent studies conducted by Eti Maden indicate that the Eskişehir–Kızılcaören area hosts a large-scale resource of approximately 694 Mt with total REE grades of 1.5–1.8%. The Eskişehir–Kızılcaören area is related to the extensional tectonic regime of Western Anatolia, whereas the Malatya–Kuluncak area is associated with post-collisional alkaline magmatism of Late Cretaceous–Early Paleocene age developed within the Central Anatolian Crystalline Complex. The presence of similar alkaline systems across Türkiye indicates significant potential for REE exploration and critical mineral strategies.

This synthesis provides a comprehensive geological reference framework for the development of REE exploration strategies, the diversification of global supply chains, and evaluation of Türkiye`s REE potential.

Abstract: Türkiye`s first official seismic hazard map, entitled "Seismic Hazard Map", was published on July 12, 1945. Maps approved by the Council of Ministers and/or published in the Official Gazette are deemed "official", and compliance with the principles of the seismic zones specified on the map became mandatory in building processes.

Pursuant to the "Law on Measures to be Taken Before and After Earthquakes," which was implemented with publication in the Official Gazette dated July 22, 1944, this map was prepared by a commission established by the Ministries of Public Works and National Education. The map divides Türkiye in to three zones: areas that have suffered major damage, hazardous earthquake zones, and safe zones. Seismic zone maps and building earthquake regulations prepared in parallel with these maps play an important role in efforts to reduce earthquake risks.

Within the scope of this study, detailed information is provided about topics such as the need for creation of the first official seismic zone map, how it was prepared and what data was used, and its importance in terms of the national disaster/earthquake risk management system. This information is supplemented and integrated with data from studies conducted in Türkiye since the 1940s about seismic zone maps and building regulations. Thus, the aim is to provide a better understanding of the importance and background of the 1945 Türkiye Seismic Zone Map in terms of disaster risk management and to shed light on Türkiye`s history of earthquake mitigation.

Abstract: During the 17 August 1999 Marmara earthquake in Türkiye, the surface rupture became indistinct north of Aydınpınar village in the southeast of Düzce Basin at the eastern end of the rupture. The surface rupture of the 17 August 1999 earthquake propagated towards the west, but it also propagated towards the east reaching the southeast of Düzce Basin. Thus fault propagation after 17 August developed towards the east to cause the later Düzce-Kaynaşlı earthquake on 12 November 1999 where the surface rupture propagated reaching Asarsuyu valley in Kaynaşlı county. Although an İstanbul earthquake is expected in the near future, we aim to draw attention to the segment in the furthest east of this zone. In this area, increasing earthquake risk is indicated by the development of a series of tensional gashes in the north of the Bolu Basin and an M=4.8 earthquake that occurred in this region on 16 March 2023.