Tolga Oyman

Efemçukuru B-rich epithermal gold deposit (İzmir, Turkey)

Efemcukuru, located in the Aegean Region, Turkey, is an example of vein-type epithermal gold deposit with related stockwork and replacement mineralisation. The veins are hosted by Late Cretaceous‐Paleogene flysch facies rocks of the Izmir‐Ankara zone, which were intruded by rhyolites from of Neogene volcanism. Gold mineralisation is associated with late pulses of magmatic hydrothermal activity and is present in zones of hydraulic brecciation adjacent to veins or stockwork zones around a dome-shaped small intrusion. The intrusion and later epithermal mineralisation are both controlled by NW‐SEtrending faults, and mineral deposits occur along strike with dips 60j to 80j to the northeast. Individual quartz veins associated with sulphide minerals and mineralised hornblende facies hornfels are other important ore-bearing formations. The alteration associated with mineralisation is represented mainly by rhodonite, rhodochrosite, axinite, quartz, calcite and adularia in veins and stockwork zone and chlorite, sericite, illite and kaolinite in the wall rock. Homogenisation temperatures of 200‐300 jC reflect emplacement of ore distant from inferred magmatic heat in epithermal environment. Due to wide range in salinity of the fluids (0‐9 eq.wt.% NaCl), sulphide diversity in the deposit is rather rich than the low-sulphidation epithermal systems. The fluid inclusion data indicate that a complicated geothermal system existed. Both the gas data and the microthermometry data indicate that there was fluid mixing. Each type of mineralisation has been studied with the aim of clarifying the paragenetic relationships among the different minerals. Arsenopyrite, pyrite (marcasite), sphalerite, galena and chalcopyrite are the main minerals with pyrrhotite, fahlore group, sphene, rutile and gold occurring as accessories. Pyrolusite, limonite (goethite, lepidocrocite), covellite‐chalcocite, malachite and azurite are of secondary origin. D 2003 Elsevier Science B.V. All rights reserved.

The influence of the abandoned Kalecik Hg mine on water and stream sediments (Karaburun, İzmir, Turkey)

This study covers the geochemical investigations on water and stream sediments to evaluate the influence from the abandoned Kalecik Hg mine. The groundwater samples (S5, S8, S9, WW10) are neutral, slightly alkaline waters which have pH values varying between 7.3 and 7.5. Electrical conductivity (EC) values of groundwaters for spring samples are low (250-300 microS/cm). However, groundwater obtained from a deep well has a higher EC value of 950 microS/cm. Hg concentrations of groundwater samples vary between 0.01 and 0.13 microg/l. Hg concentrations of other water samples taken from mining area from surface waters and adits are between 0.10 and 0.99 microg/l. Adit water (A4) collected at the mine has the highest Hg content of 0.99 microg/l and a pH of 4.4. Trace element concentrations of mine water samples show variable values. As is observed only in MW1 (310 microg/l). A4 was enriched in Cd, Co and Cr and exceed the Turkish drinking water standards (Türk Standartlari Enstitüsü, 1997). Cu concentrations vary between 6.0 and 150 microg/l and are below the Turkish water standards. Mn concentrations in mine waters are between 0.02 and 4.9 mg/l. Only for sample A4 Mn value (4.9 mg/l) exceeds the standard level. Ni was enriched for all of the mine water samples and exceeds the safe standard level (20 microg/l) for drinking water. Of the major ions SO(4) shows a notable increase in this group reaching 650 mg/l that exceeds the drinking water standards. Stream sediment samples have abnormally high values for especially Hg and As, Sb, Ni, Cr metals. With the exception of sample Ss6 of which Hg concentration is 92 mg/kg, all the other samples have Hg contents of higher than 100 mg/kg. Pollution index values are significantly high and vary between 69 and 82 for stream sediment samples.

Long-term exhumation of an Aegean metamorphic core complex granitoids in the Northern Menderes Massif, western Turkey

The Eğrigöz, Koyunoba, and Alaçam plutons are located in the northern portion of the Menderes Massif, a region characterized today by large-scale extension. To gain a better understanding of their exhumation history, we acquired zircon ages, geochemical analyses, and cathodoluminescence (CL) images to search for evidence of micro- to macro-scales of deformation. The combination is a powerful means to decipher their tectonomagmatic history. In situ ion microprobe 238U/206Pb zircon ages of the granitoids range from 30.0 ± 3.9 Ma to 14.7 ± 2.6 Ma (±1σ) and indicate the plutons crystallized over ∼15 m.y. The dated zircons show CL zoning consistent with igneous crystallization and are only located adjacent to or as inclusions in biotite grains. The youngest ages are dominated by a blue color in CL, whereas a majority of older zircons are yellow. Higher Th/U contents are typically shown by zircons with black or dark green colors in CL. Most of the samples of these granitoids indicate they are magnesian, calc-alkalic and peraluminous granite to granodiorites, but variations exist, likely reflecting heterogeneity caused by magma mixing, partial melting, crustal contamination, and post-emplacement fluid interactions as evidenced by the CL images. CL images show that all samples experienced magma mixing, multiple episodes of brittle deformation, and fluid-mediated alteration. Sources for the generation of Northern Menderes Massif granitoids include simple slab induced upwelling from the subduction of the African plate along the Hellenic arc, adiabatic decompression as the northern edge of Turkeys Anatolide-Tauride block delaminates, and upwelling asthenosphere as the continental lithosphere thins during extension. We present a model in which western Turkey is an amalgamation of stacked subduction zones that transition from north to south over time. Northern Menderes Massif granitoids document their complex geologic history in their ages, chemistry, and textures.