Jeoloji Mühendisliği Bölümü Koleksiyonu
https://hdl.handle.net/11436/921
2024-03-28T18:38:05ZFluid evolution of the Fe-Zn skarn deposits in the Çiftehan (Ulukışla-Niğde) area, south-central Turkey
https://hdl.handle.net/11436/8767
Fluid evolution of the Fe-Zn skarn deposits in the Çiftehan (Ulukışla-Niğde) area, south-central Turkey
Sunkari, Emmanuel Daanoba; Lermi, Abdurrahman; Demir, Yılmaz
This study investigated the compositional variations of fluid inclusions in the different stages of mineralization at the Esendemirtepe and Horoz Fe-Zn skarns, south-central Turkey. The skarn zones in the study area consist of volcano-sedimentary sequences intruded by intrusive bodies and marble–schist in contact with granitoids. The primary ore minerals in both locations are magnetite and hematite, with subordinate sphalerite, chalcopyrite, pyrite, and pyrrhotite. The Esendemirtepe Fe-Zn skarn deposit is a typical deep exoskarn characterized by irregular disseminated hematite and magnetite assemblages with blebs of chalcopyrite, accompanied by calcite, quartz, and epidote at the contact between the volcano-sedimentary units and the skarn. The Horoz Fe-Zn skarn deposit is also a relatively deep endoskarn characterized by massive garnet crystals. Rhythmic banded crystallization of sporadic nodular-shaped sphalerite, quartz, and calcite developed along with the marble–schist skarn contact. Two-phase liquid-rich (L + V) fluid inclusions were observed in garnet, epidote, quartz, calcite, and sphalerite mineral assemblages. The average homogenization temperatures and calculated salinities in all stages of mineralization range from 155 to 600 °C and 0.53 to 23.1 wt.% NaCl equ., respectively. The eutectic temperatures also range from −66.2 to −21.2 °C, implying that the early stages were dominated by fluids that reflect an H2O-NaCl-CaCl2 system and become an H2O-NaCl system in the later stage. The continuous evolution history of the fluids reveals a gradual change from early high-temperature-salinity magmatic fluids to late relatively low-temperature-salinity mixed magmatic fluids due to interaction with meteoric-derived fluids.
2023-01-01T00:00:00ZRecently-discovered Bahçecik Au±Ag mineralization in the Eastern Pontides, Gümüşhane-NE Türkiye: geological and geochemical implications on the intermediate sulfidation epithermal deposit
https://hdl.handle.net/11436/8744
Recently-discovered Bahçecik Au±Ag mineralization in the Eastern Pontides, Gümüşhane-NE Türkiye: geological and geochemical implications on the intermediate sulfidation epithermal deposit
Revan, Mustafa Kemal; Demir, Yılmaz; Uysal, İ̇brahim; Özkan, Mustafa; Dumanlılar, Özcan; Şen, Cüneyt; Kara, Rasim Taylan; Hamzaçebİ, Semi; Göç, Deniz; Müller, Dirk; Tokoğlu, Mustafa
Intermediate sulfidation epithermal deposits represent significant reservoirs of precious metals, playing a crucial role in global mining operations. The Anatolian Peninsula, predominantly characterized by relatively young (Tertiary) lithologies, hosts numerous occurrences of epithermal base and precious metal mineralization. Within the realm of research in Northeastern Anatolia, several hydrothermal alteration zones have emerged as indicators of concealed epithermal mineralization, with the Bahçecik mineralization standing out as a recent focal point. The Bahçecik mineralization represents an intermediate sulfidation epithermal Au-Ag system, hosted by Late Cretaceous andesitic rocks, as well as Eocene dacitic lava and tuffs. Employing U-Pb LA-ICP-MS zircon dating of the dacitic host rocks, the mineralization is estimated to have occurred during the Lutetian epoch (43.61 ± 0.35 Ma) or later. The genesis of the Bahçecik deposit is believed to be linked to postcollisional regional extensional tectonics, primarily controlling its structural arrangement. Comprising pyrite, chalcopyrite, low-Fe sphalerite, galena, tetrahedrite/tennantite, enargite-luzonite, and gold-silver minerals, the deposit is accompanied by prominent gangue minerals such as Mn- and Ca-carbonates, quartz, and barite. Microprobe measurements have identified a majority of Au-Ag minerals (krennerite, buckhornite, and nagyagite) closely associated with sulphide minerals. Fluid inclusion data reveal that mineralization and fluid transportation occurred at temperatures ranging from 153 to 327°C, with solutions exhibiting salinity levels consistent with those of intermediate sulfidation deposits (1.7–7.3 wt.% NaCl). This study unequivocally classifies the Bahçecik mineralization as an intermediate sulfidation deposit, contrary to the conclusions drawn in previous research. Moreover, our investigation has unveiled the presence of a substantial ore resource, totalling 7.84 million tons, featuring 1.76 g/t Au and 2.24 g/t Ag. As an intermediate-type deposit, it shares characteristics with other subtypes within the epithermal class, bridging the realms of both high and low sulfidation systems.
2023-01-01T00:00:00ZGeochemistry of the Lake Sediments on Robert Island, South Shetland Islands, Antarctica: implications for weathering processes in Polar areas
https://hdl.handle.net/11436/8715
Geochemistry of the Lake Sediments on Robert Island, South Shetland Islands, Antarctica: implications for weathering processes in Polar areas
Özyurt, Merve; Demir, Yılmaz; Özkan, Korhan; Kandemir, Raif
The preliminary results of geochemical analyses of the surface sediments from 4 lakes on Robert Island, South Shetland, Antarctica, are presented herein. The samples were collected during the Turkish Antarctic Expedition (TAE-II) in 2018. Sediment samples were obtained from the littoral zone (approximately 20 cm) of 4 different lakes exposed on the glacier-free land area on Robert Island. The lake sediments predominantly consist of fine-grained sand, clay, and silt particles. These particles include Fe-shale and graywacke geochemical characteristics. Their plagioclase index of alteration, chemical index of weathering, chemical index of alteration, and other weathering index values, suggest that the studied sediments have likely undergone low to moderate weathering and alteration processes. The Th/U ratios generally indicated a lower distribution relatively to the upper continental crust, and they displayed slight enrichment in alkali elements, indicating a low degree of chemical weathering that has slightly influenced the sediment chemistry. Moreover, the Gd/Yb, Zr/Y, and La/Yb ratios exhibited similarities with the surrounding volcanic rocks on Robert Island. Additionally, their chondrite-normalized rare earth element (REE) patterns exhibited a similar trend, implying that the REE composition of the sediments is predominantly controlled by the local source rocks. Nevertheless, there were slight differences in the Y/Ho ratios and heavy REE (HREE) contents, suggesting the presence of additional sources contributing to the REE supply in the lake basins. The Co/ Th, La/Sc, Th/Sc, and Zr/Sc ratios mostly resembled those of basic volcanic rocks, while the Rb, K, HREE, and Ni values dominantly indicated basic rocks with a minor input from felsic magmatic or quartzose sedimentary rocks. Considering the geomorphology and location of the basins, which are mostly situated along the coast where foehn winds have a limited influence over ice-free areas, it is likely that locally resuspended materials have had a significant impact. This factor may mask any potential signals of modern dust fallout and accumulation. However, possible dust sources include nearby or distant areas, such as exposed rock and sediment within the immediate vicinity of the lakes, including dry lakebeds, glacial outwash plains, or exposed moraines. Based on multiproxy element analyses, including REEs, high field strength elements, and lithophile elements, the geochemistry of the studied sediments, the overall geochemical characteristics cannot be fully explained by the local sources, suggesting that weathering processes and minor contributions from dust materials have played a nonnegligible role in shaping their chemistry.
2023-01-01T00:00:00ZThe petrogenesis of analcime in the coppermine formation on Robert Island, South Shetland ıslands, Antarctica
https://hdl.handle.net/11436/8714
The petrogenesis of analcime in the coppermine formation on Robert Island, South Shetland ıslands, Antarctica
Kandemir, Raif; Demir, Yılmaz; Şen, Cüneyt; Yağcıoğlu, Ufuk Celal
The South Shetland Islands were shaped by island arc volcanism that occurred from the Jurassic to the Quaternary. Robert Island is located in the center of this archipelago, and Coppermine Peninsula, located on the southwestern part of Robert Island, exposures significant rock outcrops of basalts and andesitic-basaltic agglomerates of the Coppermine Formation. The investigated samples were collected during Turkish Antarctic Expedition 2 (TAE-II), in March–April 2018, from the area northeast of Triplet Hill. The volcanic rocks exhibited an amygdaloidal microlithic-porphyritic texture. Subhedral to anhedral phenocrysts of labradorite, augite, and olivine were observed with holocrystalline groundmass composed of plagioclase, pyroxene, and opaques. Petrographic studies revealed that the vesicles were initially coated with clay minerals, and X-ray diffraction studies showed that mostly analcime and carbonates, and less amount of zeolites filled the vesicles. Herein, it was aimed to discuss the analcime formation. Fluid inclusion studies performed on the analcime revealed homogenization temperatures ranging from 83 to 268 °C. The eutectic temperatures of the fluid inclusions suggested that these minerals were formed from NaCl-dominated solutions that contained a limited amount of MgCl2 and CaCl2. The salinity of these inclusions ranged between 0.2–2.9 wt.% NaCl equivalent, and exhibited final ice melting temperatures of –1.7 to –0.1 °C. These salinity values, which are lower than the average salinity values of seawater, suggest that the formation of the analcime and the fibrous zeolites (thomsonite and stilbite) was closely associated with meteoric solutions. Consequently, the salinity values of the fluid inclusions suggest the mixing of meteoric waters form from glaciers and seawater at different rates.
2023-01-01T00:00:00Z