Eker, Çiğdem Saydam; Arı, Uğur Volkan

The aim of this study is to determine the potential toxic element (PTE) content linked to the geochemical features of Berriasian–Aptian carbonate rocks commonly outcropping in Gümüşhane, along with the degree of pollution and possible sources of these toxic elements, and to compare dolomite with limestone in terms of toxic metal abundance. In the field, dolomite and limestone samples were collected by measuring stratigraphic sections around Yuvacık, Ünlüpınar, Çukutbaşı, Bağlarbaşı, Mescitli and Gülaçar (Gümüşhane). The samples were analyzed using inductively coupled plasma mass spectroscopy (ICP-MS). The mean values for Mo, Cu, Pb, Zn, Ni, As, and Co were 3.1, 23.8, 7.1, 14.5, 13.5, 30.9, and 8 mg/kg in Yuvacık; 6, 2.3, 1.1, 3.5, 8.1, 12.3 and 2.5 mg/kg in Ünlüpınar; 17.9, 1.8, 1.5, 8.6, 7.9, 13.9 and 1.7 mg/kg in Çukutbaşı; 3.7, 6.5, 31.7, 82.7, 9.5, 32.0 and 1.9 mg/kg in Bağlarbaşı; 0.7, 0.7, 7.1, 21.3, 2.6, 11.8 and 0.7 mg/kg in Mescitli; and 1.2, 1.1, 2.4, 5.2, 1.3, 4.0 and 0.2 mg/kg in Gülaçar, respectively. According to geochemical pollution parameters [geo-accumulation (Igeo), pollution index (Pi), and pollution load index (Pln)], the rocks were generally significantly polluted by Mo and As, without notable pollution by the other elements. Limestone samples from the Yuvacık, Ünlüpınar, and Çukutbaşı areas were more polluted in terms of Mo and As compared to dolomites. This pollution in Yuvacık and Ünlüpınar was identified to have geogenic sources (Pb–Zn–Cu mineralization) and in Çukutbaşı was identified to have lithogenic sources. Dolomites from the Bağlarbaşı area were more polluted in terms of As and less polluted in terms of Mo compared to limestones. In the Mescitli location, both dolomites and limestones were occasionally polluted in terms of As, while limestones were polluted in terms of Mo. In these two areas, the sources of As and Mo are geogenic (Pb–Zn mineralization), In Gülaçar, dolomites were more polluted in terms of Mo and less polluted in terms of As compared to limestones. In this locality, As and Mo are thought to have a geogenic source (Pb–Zn–Cu mineralization).

Sipahi, Ferkan; Zeybek, Halil İbrahim; Gücer, Mehmet Ali; Işık, Fatih

The carbonate rocks in the eastern part of NE Turkey are situated within the Pontide paleo-magmatic arc and are frequently in contact with granitoid formations, often hosting skarn mineralization in the region. These carbonate rocks, typically found on ridges and hillsides exhibit predominant orientations along east–west, northeast-southwest, and northwest-southeast directions. A part of limestone, named as biomicrite, metamorphosed and display a saccharoidal texture. Comprised mainly of calcite, with less secondary quartz and iron oxide minerals, these carbonate rocks are classified as Fe-poor calcio-carbonate and magnesio-carbonate, having higher CaO and LOI contents. Marble and recrystallized limestone with granoblastic texture mainly comprise of calcite, less quartz, magnetite, and hematite. Marble classification diagrams suggest calcic skarn mineralization, indicated by decreasing CaO (or CO2) and increasing MgO from limestone to marble (or skarn). Strontium contents deviate slightly from the lithosphere carbonate average, while low Rb contents, attributed to skarn metamorphism, indicate the absence of K-bearing minerals. The high Al2O3/SiO2 in the carbonate rocks can points out hydrothermal activity and carbonate disengagement can indicate to actualize at temperatures that can affect Ce and Al mobilities. The low authigenic U value, low U/Th and Ni/Co ratios in carbonate rocks have been implied that protolith constituents deposited under oxic conditions. Positive Eu anomalies in limestone and marble suggest the influence of hydrothermal fluids. Carbon and oxygen isotope values in marble are similar with those of metamorphic and skarn marbles, indicating a magmatic origin. Overall, mineralogical and geochemical analyses propose a uniform source and/or geological process for all studied marbles.

Gadirov, Vagif G.; Maden, Nafiz; Gadirov, Kamran V.

Local gravity and magnetic anomalies are employed to identify potential hydrocarbon reservoirs in the Middle Kura Depression (MKD) within the South Caspian basin in Azerbaijan. The MKD basin in Azerbaijan including the Yevlakh-Agjabedi trough covers a large part of the Kura intermountain basin between the Greater and Lesser Caucasus. In the study region, several local gravity and magnetic anomalies are discovered related to oil and gas deposits in the sedimentary depression whose thickness is 12–14 km. Gravity minima and maxima expressed by different wavelength anomalies are indicative of density variations within the basin. Local gravity minima with an intensity of 0.3–0.4 mGal identified in the study areas are related to the oil–gas deposits. While the local positive magnetic anomalies are associated with the volcanic formations, local negative magnetic anomalies appear over the productive parts of the buried structure within the sedimentary complex. Intense local magnetic minima anomalies with an intensity of 20–30 nT are evidence of oil and gas accumulations. The limitations of traditional methods for interpreting gravity and magnetic data to locate oil and gas fields have led to the use of gravity field gradients. This alternative approach has proven advantageous, as it confirms the results of gravity exploration and is useful for directly searching for hydrocarbons.

Eker, Çiğdem Saydam; Arı, Uğur Volkan

Samples from late Jurassic–early Cretaceous age limestones in five different areas in the Gümüşhane region (NE-Türkiye), were studied using TOC/Rock–Eval, and some trace elements analysis, to evaluate their organic material source, type, thermal maturity, and paleo-environment conditions. The studied carbonate rocks are characterized by 90 m thick in the Bağlarbaşı section, 420 m in the Gülaçar, 584 m in the Ünlüpınar, 375 m in the Mescitli, and 272 m in the Yuvacık. The carbonate rocks are generally represented by, from bottom to top, dolomite, oolitic, sparitic, sandy, micritic, clayey, and bituminous limestones. Average total organic carbon (TOC) values are 0.14, 0.16, 0.20, 0.12, and 0.20% in the Bağlarbaşı, Gülaçar, Ünlüpınar, Mescitli, and Yuvacık sections, respectively. Organic material in the limestones consists of Type II-III kerogen, indicating that a mixture of terrigenous higher plants–marine aquatic organisms was the main source. Average Tmax values and Tmax-based vitrinite reflectance values (Ro %) are calculated as 435 and 0.67, 444 and 0.83, 431 and 0.60, 442 and 0.79, and 437 °C and 0.70 in the Bağlarbaşı, Gülaçar, Ünlüpınar, Mescitli, and Yuvacık sections, respectively, indicating that the samples have generally reached thermal maturity. The limestones in the Gülaçar, Mescitli, and Yuvacık areas are probably well-drained rocks that were extracted and originated hydrocarbon efficiently from the limestone fractures. In general, a non-marine–sometimes marine deposition environment for the carbonates is indicated by total sulfur values. V/Ni and Sr/Ba ratios indicate a stratified water column with high–low salinity and anoxic–oxic bottom water circumstances and accordingly a transitional sedimentation environment.