Sipahi, Ferkan; Akpınar, İbrahim; Eker, Çiğdem Saydam; Kaygusuz, Abdullah; Vural, Alaaddin; Yılmaz, Meltem

The Eğrikar Fe–Cu skarn type mineralization is located approximately 100 km NW of Gümüşhane in NE Turkey. Geochemical analyses of diorite, which is thought to cause skarn, indicate medium K calc-alkaline (1.3 to ~ 2.3 wt% K2O), metaluminous to peraluminous (A/CNK = 0.76 to 1.13) and resembles a continental arc granite. The age of U–Pb zircon obtained from diorite is 42.3 ± 1.0 Ma, which reflects the age of skarn metasomatism after intrusion into Late Cretaceous sandy carbonates. Skarn formation zones are recognized as endo- and exoskarn. The endoskarn zone mainly consists of pyroxene with hedenbergite (Di4.31–28.14Hd59.29–80.82Jo5.0–35.55) at prograde stage. Mn content of pyroxene increases a slight from endo to exoskarn. Pyroxene is replaced by epidote and hornblende at the retrograde stage. The exoskarn zone comprises garnet with andradite (Ad91-99Gr01–07) and grossular-andradite (Ad44-95Gr05–54), epidote and quartz as silicate minerals, and magnetite and hematite as ore minerals. Magnetite is the abundant ore mineral and is accompanied by chalcopyrite and minor pyrite at retrograde stage. On the basis of fluid inclusion values of minerals, the temperature range for hedenbergite in endo-exoskarn is 350 °C–425 °C, for epidote in exoskarn is 365 °C–376 °C, and for quartz in exoskarn 200 °C–380 °C. NaCl equivalent salinity for hedenbergite 6.88–10.73 wt% and for quartz is 3.9–15.38 wt. The δ18O values of hedenbergite is 4.1 to 4.7‰ and for garnet 3.4‰ at prograde stage, for epidote 7.9–9.2‰, for magnetite 1 to 4.4‰, for hematite − 2.9 to − 1.6‰ and for quartz range between 8.5‰ and 15.2‰. The δ18O value of epidote suggests that oxygen is a magmatic fluid whereas hedenbergite, garnet, quartz and magnetite show the mixing of magmatic and meteoric fluids. In addition, the C isotope values (− 3.2 to 2.8‰) of calcite and marble in Eğrikar Fe–Cu skarn reflect those of metamorphic, and skarns. Based on oxygen isotope data from mineral pairs, the retrograde skarn formation is characterized by epidote–magnetite assemblage formed at 255 °C–438 °C. Fluid oxygen isotope compositions of magnetite and epidote pairs of the exoskarn skarn zone indicate a mixing of magmatic and meteoric fluids with narrow δ18O values between 7.17‰ and 8.9‰. The δ34S values of the pyrites exhibit a narrow range of 3‰ and 4.4‰, thereby indicating that sulfur were probably leached from magmatic rocks. Based on the field and laboratory observation, mineral chemistries, fluid inclusion studies and isotope composition analysis, it is suggested that the Eğrikar Fe–Cu skarn mineralization occurs in a magmatic origin fluids being initially under reduced conditions, subsequently under oxidized conditions, and at shallow depth.

Yaylali-Abanuz, Gülten; Tüysüz, Necati; Akaryali, Enver

The Arzular gold mineralization is located at the southern part of the Black Sea Tectonic Unit in northern Turkey. This belt hosts several high-potential epithermal gold deposits and it is highly probable that there are a number of undiscovered occurrences in the region. The presence of intensely altered areas, suitable structural elements and acidic intrusions indicates that the region has an important potential for epithermal gold. Soil geochemistry surveys are widely used for the exploration of buried mineral deposits. In this work the applicability of soil geochemistry surveys for exploration of buried mineral deposits was tested using various statistical methods. In this respect, concentrations of 16 elements have been assayed in about 50 soil samples collected from the Arzular area. Soil samples were taken from the B horizon. The data revealed elevated concentrations for gold (0.20-259.2 μg/kg), silver (23-26,972 μg/kg), arsenic (1.7-301.8. mg/kg), copper (54.09-170.7. mg/kg), zinc (5.1-261.3. mg/kg) and lead (2.6-385.45. mg/kg). Gold is significantly correlated with elements such as Sb, Cd, Pb, Ag, As, Cu and Mo. Relatively high anomaly contrasts between Au, As, Ag and Sb and their coinciding anomalies along an E-W trending fault at the eastern part of the field might indicate that As, Ag and Sb could be used as a pathfinder element for exploration of gold deposits. Factor analysis was applied to elements in soil samples and then distribution diagrams were prepared using the factor scores obtained. In a distribution diagram for mineralization-associated factor score, two anomaly fields along the E-W trending fracture line and one anomaly field at the eastern part were distinguished. The largest anomaly in an ellipsoidal shape with long axis of 350. m was obtained from the southeast part of the area. Anomaly patterns show that factor scores might yield suitable and net results for the exploration. NE-SW trending fracture system is not related to mineralization and is younger than E-W trending fracture line. However, the E-W trending fault system controls the mineralization; therefore, the eastern extent of this fault zone needs to be investigated.