Geological properties and ore deposits of the environment of the Esendal (Yusufeli̇-Artvin) village

This study was aimed to investigate the ore deposit potential of the region covering an area of approximately 30 km2 between Esendal, Boyalı and Bostancı villages of Yusufeli district of Artvin province. The area is located 76 km southwest of Artvin provincial center and approximately 16 km north of Yusufeli district. Olur and Oltu districts of Erzurum province to the east, Tortum, Uzundere and İspir districts of Erzurum province to the south, Çamlıhemşin and Ardeşen districts of Rize province to the west, and Artvin center and Murgul districts to the north. At the same time, the study area is located within the northern zone of the Eastern Pontides, which is among the tectonic units of Turkey. The study area is underlain by the Triassic aged Berta formation, a metamorphic stack consisting of sandstone, siltstone at the base and epiclastic sandstone-mudstone succession with basic volcanic interlayers at the top. Late Jurassic aged Mudurnu formation, which consists of epiclastic sandstone, siltstone, tuff interlayered, basaltic-andesitic composite lavas and pyroclasts, which are the products of active volcanism in the environment during the formation processes of this formation, overlies the metamorphic stack. Late Jurassic-Early Cretaceous aged Öğdem formation composed of crystallized limestones, volcanic interbedded pebbles and reefal limestones unconformably overlies the Mudurnu formation. Late Cretaceous aged Yusufeli formation, which includes andesitic-dacitic lavas and pyroclasts with basaltic lava intercalated andesitic-dacitic lavas and pyroclasts and felsic rocks such as rhyolite-rhyodacite, in which the effect of acidic and basic series is observed in the magmatic processes effective in its formation, is unconformable with the reefal limestones in the study area. Kaçkar granitoid, which developed in the Late Cretaceous-Paleocene interval and consists of igneous rocks such as granite, granodiorite, monzonite and monzodiorite, intrudes into the environment by cutting the Yusufeli formation. Quaternary aged alluvium, which unconformably covers all the preceding units, consists of unconsolidated sediments with a wide variety of materials such as gravel, sand, silt and clay. Within the study area, there are ore-forming minerals such as pyrite, chalcopyrite, hematite, molybdenite, digenite associated with the alteration that occurred during the intrusion of granitoids. The average values of SiO2, Al2O3, Fe2O3, MgO, CaO, Na2O, K2O, TiO2, P2O5, MnO, Cr2O3, 67.60%, 2.31%, 4.29%, 1.51%, 1.87%, 0.13%, 0.17%, 0.11%, 0.08%, 0.05% and 0.004% were determined from the analysis of samples taken from the Yusufeli formation. In addition, 139.5 and 212 ppm Cu was detected in two samples taken from the formation. According to the correlation analyses in the Yusufeli formation, positive correlation is observed between the Al, Fe, Mg, Ca and Mn components that provide the formation of plagioclase, alkali feldspars and pyroxenes from mafic minerals and it is determined that they act together. The group of components that provide the formation of rock-forming minerals is determined as the main components group. Hydrothermal alteration group was effective in the addition of some sulfide minerals to the environment during the alteration that provided more SiO2 to the environment than the amount of SiO2 contained in the rock-forming minerals, and the combination of SiO2 with components commonly found in medium-low temperature hydrothermal environments (Au, Ag, Sb, Hg) determined this alteration. The factors affecting the changes in the Yusufeli formation are potassic alteration, relative decrease in temperature and transition from potassic alteration to phyllic alteration, traces of skarn type mineralization at the granitoid intrusion boundary, decrease in hydrothermal temperature, propylitic alteration in the divergent regions of the granitoid intrusion and low temperature phases of propylitic alteration that provide Hg placement. The average values of SiO2, Al2O3, Fe2O3, MgO, CaO, Na2O, K2O, TiO2, P2O5, MnO, Cr2O3, % 52.35%, 5.28%, 7.30%, 3.59%, 6.64%, 0.10%, 0.09%, 0.37%, 0.08%, 0.15% and 0.0035% were determined from the analysis of samples taken from the Mudurnu formation. In addition, 349 ppm Cu was detected in the sample belonging to the formation taken from the vicinity of Söğütönü locality. According to the correlation analysis in the Mudurnu formation, it was determined that the main oxide components except SiO2 and K2O are positively correlated with each other. Cluster analysis shows that the components were evaluated as three main groups: Al-Ti-Mg-Cr group, Fe-Mn-Ca group and Si-K group. The fact that the main oxides Al2O3, Na2O, MgO, TiO2 and P2O5 are in the same group led to the formation of albite composite plagioclases containing Na and Al in the main. Group containing Au, Ag, Cu, Ba, V, Zn, Zn, NTE along with main oxides such as Fe2O3, MnO and CaO is explained by low temperature hydrothermal alteration that occurred as a result of the intrusion of granitoids after the Mudurnu formation. Hydrothermal solutions circulating in the volcanic rocks of the formation enabled the precipitation of the commonly observed silica instead of the weathered minerals and the Si-K group was active in this process. The factors affecting the changes in the Mudurnu formation are potassic alteration, phyllic alteration and secondary calcite formations due to contact metasomatism and sulphide mineralization. The average values of SiO2, Al2O3, Fe2O3, MgO, CaO, Na2O, K2O, TiO2, P2O5, MnO, Cr2O3, 56.50%, 3.52%, 7.06%, 2.49%, 4.11%, 0.12%, 0.13%, 0.328%, 0.280%, 0.103% and 0.001% were determined from the analysis of samples taken from the Kaçkar granitoids. In addition, 106.5 and 96.4 ppm Cu was detected in two samples taken near the center of Bostanci and Esendal villages. Correlation analyses of Kaçkar granitoids show that all main oxides except SiO2, K2O and Cr2O3 are positively correlated with each other. The major component group is represented by chlorites, clay minerals and secondary calcites formed as a result of rock-forming minerals and alterations. Hydrothermal alteration group determined the silicification and porphyry type mineralization formed as a result of side rock reactions during the intrusion of the crustal origin igneous mass. Potassic alteration and hydrothermal alteration were determined as the factors affecting the changes in Kaçkar granitoids. The average values of SiO2, Al2O3, Fe2O3, MgO, CaO, Na2O, K2O, TiO2, P2O5, MnO, Cr2O3, 60. 86%, 3.42%, 5.75%, 2.31%, 3.71%, 0.118%, 0.14%, 0.233%, 0.12%, 0.09% and 0.003% were determined from the analysis of samples taken from the alteration samples. Cluster analyses of the alteration samples showed that the components were divided into two main groups: the main component group and the hydrothermal alteration group, which includes SiO2, K2O and important trace elements that make up the ore. It was determined that the hydrothermal alteration group represents alteration belts starting from potassic alteration to propylitic alteration ending with sulfidic phases. Cu and Au values reaching up to 6.15% in some ore samples and Ag values reaching up to 45.6 ppm with 12.8 ppm Au show the porphyry-hydrothermal system that provides gold enrichment with porphyry Cu mineralization and Ag enrichment at points far from magma. As a consequence of the analysis of the ore sample taken from Esendal village center, it was determined that it contained 17.93 ppm molybdenum, 35.60 ppm lead and 2300 ppm (0.23%) zinc among the important trace elements and the averages with another ore sample evaluated were calculated as 9.76 ppm for molybdenum, 22.20 ppm for lead and 1747.5 ppm (0.175%) for zinc. There is a significant potential for metallic minerals (copper, gold, silver, etc.) in the study area. It would be appropriate to conduct detailed mining geology and geochemical studies in the regional units to evaluate the economic potential.