Search Results (7)

Northwestern Türkiye (Biga Peninsula, Edremit Gulf, Saros Bay) is a highly seismically active region at the convergence of the Anatolian, Eurasian, and Aegean tectonic plates. It features numerous active faults, including the Yenice–Gönen and Edremit fault zones, in addition to offshore segments of the North Anatolian Fault Zone (NAFZ) in Saros Bay. Earthquakes here exhibit various mechanisms: the 2017 Ayvacik earthquake sequence (Mw 5.4) near the Tuzla Fault featured NE–SW normal faulting, reflecting regional extension. Other moderate events display strike–slips with minor normal components, indicating transtensional forces. These findings enhance our understanding of the area’s complex seismotectonic activity and stress the critical need for continuous seismic monitoring and hazard assessment in this geologically complex and densely populated part of Türkiye. Full article

The Tuzla area, located in the Ayvacık district of Çanakkale (Biga Peninsula, northwestern Türkiye), hosts a Oligocene-Miocene volcanic system comprising andesitic, dacitic, rhyolitic lavas, trachyandesite, pyroclastics, and ignimbrites, and the Kestanbol Pluton. Petrographic and X-ray diffraction (XRD) analyses indicate that the altered volcanic units are dominated by porphyritic dacitic/rhyodacitic and trachyandesitic rocks, with silicification, iron oxide formation, and opacification. XRD results reveal smectite, smectite–illite/mica, illite–mica, kaolinite, cristobalite–opal, K-feldspar, plagioclase, dolomite, hematite, and quartz as the principal mineral phases. Geochemical data, including rare earth elements (REEs), suggest that fractional crystallization of primary mineral phases played a major role in controlling magmatic evolution. Chondrite-normalized REE patterns display enrichment in light REEs relative to heavy REEs, indicating derivation from a common magma source. K₂O–Na₂O and (Na₂O + K₂O)–FeOᵗ–MgO (AFM) diagrams show high-K calc-alkaline, calc-alkaline, and tholeiitic affinities, with most rhyodacite/dacite and all trachyandesite samples plotting in the tholeiitic field. Tectonic discrimination diagrams indicate formation in both volcanic arc and intraplate tectonic settings. Moderate enrichments in Ba and Sr reflect magmatic evolution and source characteristics, whereas the highest concentrations are attributed to post-magmatic fluid–rock interaction. Overall, the Tuzla volcanic rocks originated from a collision-related enriched lithospheric mantle source and subsequently evolved through fractional crystallization and assimilation processes, accompanied by crustal contamination and variable hydrothermal overprint. Full article

The Tuztaşı low-sulfidation epithermal Au–Ag deposit (Biga Peninsula, Türkiye) records a multi-stage hydrothermal history that can be interpreted through the trace and rare-earth-element (REE) chemistry of quartz. High-precision LA-ICP-MS analyses of five representative quartz samples (23 ablation spots; 10 analytically robust) reveal two fluid stages. Early fluids were cold, dilute meteoric waters (δ¹⁸O₍H₂O₎ ≈ −6.8 to +0.7‰), whereas later fluids circulated deeper, interacted with felsic basement rocks, and evolved in composition. Mineralized quartz displays marked enrichment in As (raw mean = 2854 ± 6821 ppm; filtered mean = 70 ± 93 ppm; one spot 16,775 ppm), K (498 ± 179 ppm), and Sb (57.8 ± 113 ppm), coupled with low Ti/Al (<0.005) and elevated Ge/Si (0.14–0.65 µmol mol⁻¹). Chondrite-normalized REE patterns show pronounced but variable LREE enrichment ((La/Yb)_n ≤ 45.3; ΣLREE/ΣHREE up to 10.8) and strongly positive Eu anomalies (δEu ≤ 9.3) with slightly negative Ce anomalies (δCe ≈ 0.29); negligible Ce–Eu covariance (r² ≈ 0.05) indicates discrete redox pulses. These signatures indicate chemically evolved, reducing fluids conducive to Au–Ag deposition. By contrast, barren quartz is characterized by lower pathfinder-element contents, less fractionated REE profiles, higher Ti/Al, and weaker Eu anomalies. A composite exploration toolkit emerges: As > 700 ppm, As/Sb > 25, Ti/Al < 0.005, Ge/Si > 0.15 µmol mol⁻¹, and δEu ≫ 1 reliably identify ore-bearing zones when integrated with δ¹⁸O data and fluid-inclusion microthermometry from earlier studies on the same vein system. This study provides one of the first systematic applications of integrated trace-element and REE analysis of quartz to a Turkish low-sulfidation epithermal system, offering an applicable model for vectoring mineralization in analogous settings worldwide. Full article

In this study, the facies and degrees of hydrothermal alteration related to the low-sulfidation epithermal Kestanelik Au deposit in the Biga Peninsula metallogenic province are identified through petrographic studies and analysis of geochemical characteristics, such as mass changes, molar element ratios, and alteration indices. The gold mineralization is located in silicified zones containing veins and stockwork veinlets of silica. In the Kestanelik Au deposit, common hydrothermal alteration is mainly found in the Permian-Upper Cretaceous Çamlıca basement metamorphics and the Eocene granodiorite, and less often in the Eocene Şahinli volcanic rocks of the Karabiga Massif on the Peninsula. Based on mineralogical and geochemical studies conducted on altered samples, four different alteration facies are defined as silicic, sericitic, argillic, and propylitic, which show remarkable differences in the behavior of REEs, Si, K, Al, Na, and Ca elements. The hydrothermal fluids that caused alteration in the Kestanelik Au mineralization and host rocks had low REE contents because of REE mobilization. In addition, the kaolinization of feldspars and micas, and the chloritization of biotite and feldspars, may have caused negative Eu anomalies. The characterization of rocks subjected to hydrothermal alteration that are most influenced by diverse K-metasomatism with the largest K gains and losses in Na–Ca is illustrated by molar element ratio plots. Depending on the intensity of K-metasomatism, gold mineralization increases with increasing K trends toward gold ore veins. In the Kestanelik Au field, the argillic, sericitic, and propylitic alteration types from the zones enclosing the Au ore veins are revealed using the Ishikawa alteration index and chlorite–carbonate–pyrite index. Mass changes in the altered rocks indicate that there are gains in Si, K, and Al, and losses in Na and Ca with the increasing intensity of alteration toward the ore veins. The results confirm the presence of silicic and K–metasomatic (sericite and argillic) and propylitic (Fe-rich chloride) alteration zoning extending from the inner regions to the outer regions, which characterize the epithermal ore systems. Full article

The current study sought to investigate the physiochemical conditions and fluid evolution within the Yolindi Cu-Fe skarn mineralization located in the Biga Peninsula, NW Turkey. This was accomplished through a comprehensive investigation of geological and mineralogical data, along with isotopic analyses of sulfur (δ³⁴S), carbon (δ¹³C), and oxygen (δ¹⁸O) of sulfide and calcite minerals, respectively, as well as fluid inclusion data pertaining to various minerals (e.g., andradite, quartz, and calcite). The Yolindi area features a complex geological framework, including the Paleozoic Kalabak Group (which includes the Torasan, Yolindi, and Sazak formations) and the Triassic Karakaya Complex. These formations were subsequently intruded via Early Miocene Şaroluk granitoids and Hallaçlar volcanics. Skarn formation is zoned into endoskarn and exoskarn types (being categorized into proximal, intermediate, and distal zones), with distinct mineral assemblages indicating concentric and contact metamorphic alteration patterns around the western part of Şaroluk granitoid intrusion in contact with the Torasan formation. The ore mineralogy and paragenesis suggest three distinct stages of evolution: an initial phase of prograde metasomatism characterized by the formation of magnetite and pyrite alongside anhydrous calc-silicate minerals; a subsequent phase of retrograde alteration marked by the formation of epidote, actinolite, and scapolite, accompanied by the occurrence of chalcopyrite and specular hematite; and finally, a post-metasomatic stage involving oxidation processes that led to the development of secondary mineral assemblages containing cerussite, covellite, and malachite. Sulfur isotopes (δ³⁴S) of sulfides from endoskarn (from +0.27 to +0.57‰_VCDT) to intermediate exoskarn (from −9.44 to −5.46‰_VCDT) zones indicate a diverse sulfur source, including magmatic, sedimentary, and possibly organic matter. δ³⁴S values in hydrothermal fluids suggest a magmatic–hydrothermal origin, with endoskarn and proximal zone fluids showing a slight negative signature and intermediate zone fluids indicating a strong influence from organic-rich or metamorphic sulfur reservoirs. Carbon and oxygen isotopic compositions (δ¹³C and δ¹⁸O) of calcite revealed a progression from marine carbonate signatures in marble samples (from +1.89 to +2.23‰_VPDB; from +21.61 to +21.73‰_VSMOW) to depleted values in prograde (from −6.0 to +0.09‰_VPDB; from +6.22 to +18.14‰_VSMOW) and retrograde skarns (from −3.8 to −2.25‰_VPDB; from +0.94 to +3.62‰_VSMOW), reflecting interactions with high-temperature magmatic fluids and meteoric water mixing. The fluid inclusions in prograde minerals generated under the conditions of fluid boiling exhibited high temperatures, reaching up to 412 °C, and salinities up to 26 wt.% NaCl equivalent. Conversely, the fluid inclusions in retrograde minerals, which were generated due to fluid mixing, exhibited lower temperatures (with an average of 318 °C) and salinities with an average of 4.9 wt.% NaCl equivalent. This indicated that the cooler and more diluted fluids mix with meteoric waters and interact with organic materials in the host rocks. This suggests a multifaceted origin involving various sources and processes. Therefore, this study concluded that the skarn mineralization in the Yolindi area resulted from complex interactions between magmatic, metamorphic, and meteoric fluids, reflecting a dynamic ore-forming environment with implications for the regional metallogeny of Cu-Fe skarn deposits. Full article

The current work investigates the impact of magmatic fluids and metasomatic processes on the Yolindi Cu-Fe skarn deposit in the Biga Peninsula, Turkey. It traces the stages of skarn evolution, from prograde to retrograde alterations, and investigates findings within a broader geological, mineralogical, and geochemical framework. Additionally, it assesses the evolutionary history of the Yolindi deposit in relation to calc-alkaline magmatic activity in an island-arc environment and compares its mineral compositions and genesis with other global and regional Cu-Fe skarn deposits. The Yolindi Cu-Fe skarn deposit in the Biga Peninsula was formed by the intrusion of Şaroluk quartz monzonite pluton into Upper Paleozoic Torasan Formation rocks such as phyllite, schists, hornfels, marble, and serpentinites. During skarnification, reactions between the magmatic fluids from the Şaroluk quartz monzonite pluton and the Torasan Formation produced skarn minerals associated with metals such as Fe and Cu. Initially, these reactions formed prograde skarn minerals such as augite-rich pyroxenes and andradite garnets with magnetite and pyrite. As the system cooled, these initial minerals underwent retrograde alteration, leading to the formation of minerals such as epidote, actinolite, and chlorite, as well as other copper and iron minerals including chalcopyrite, bornite, secondary magnetite, and specular hematite. Therefore, four main stages influenced the formation of the Yolindi Cu-Fe deposit: metamorphic bimetasomatic, prograde metasomatic, and retrograde metasomatic stages. Later, oxidation and weathering resulted in supergene minerals such as cerussite, malachite, and goethite, which serve as examples of the post-metamorphic stage. The mineralogical shifts, such as the andradite–grossular transition, reflect changing hydrothermal fluid compositions and characteristics due to the addition of meteoric fluids. Importantly, the formation of magnetite after garnet and clinopyroxene during the retrograde stage is evidenced by magnetite crystals within garnet. The mineral associations of the Yolindi Cu-Fe skarn deposit align with the global skarn deposits and specific Turkish skarns (e.g., Ayazmant Fe-Cu and Evciler Cu-Au skarn deposits). The Yolindi Cu-Fe skarn deposit, in association with ore-bearing solutions having magmatic origins, developed in an island-arc setting. Full article

We study the tectonic deformation from the February 2017 shallow earthquake sequence onshore Biga Peninsula (NW Turkey, NE Aegean region). We use InSAR interferograms (Sentinel-1 satellites) to identify the seismic fault (striking N110°E) and seismological data (parametric data and Moment Tensor solutions from NOA and KOERI catalogues) so as to refine its geometry and kinematics using inversion techniques. Despite the moderate magnitudes of the main events of the sequence (5.0 ≤ M_w ≤ 5.2), the total surface deformation is 2.2 fringes (or maximum 6.2 cm along LOS) and it is well visible with InSAR because of the shallow depth of the four main events (6–8 km) and the good coherence of the signal phase. Our geodetic inversion showed that the fault has normal-slip kinematics, dimensions of 6 by 6 km (length, width) and dips at 45°. The InSAR data are fitted by a uniform slip of 28 cm. In addition, 429 earthquakes were relocated with the HypoDD software and the use of a 1-D velocity model. The dip-direction of the fault is not retrievable from InSAR, but a south-dipping plane is clear from seismology and the aftershocks distribution. The spatial distribution of relocated events indicates the activation of one fault with a rupture zone length of about 10 km, a result of the occurrence of off-fault aftershocks along strike the main rupture. A stress inversion using 20 focal mechanisms (M ≥ 3.6; NOA solutions) indicates that faulting accommodates a N196°E extension. It is confirmed that moderate (5.0 ≤ M ≤ 5.2) shallow events can be traced in InSAR studies and can produce surface displacements that provide useful data in fault inversion. Full article