Geochemical exploration studies for uranium in Dadağı (Gülşehir-Nevşehir) vicinity

Rock geochemistry and stream sediment geochemistry studies was performed in this study near the villages of Dadağı and Ayhan in Nevşehir province. These geochemistry studies have been conducted to determine the geochemical characteristics of uranium mineralization. The study, although based on the interpretation of results in chemical analysis, was performed both chemical analysis and radiometric measurement. When compared with uranium concentrations in the silicified limestones and siltstones, it is understood that the uranium concentration was higher in the siltstones. Distribution of trace elements (U, Th, Ba, Cs, Ga, Hf, Nb, Rb, V, Zr, W, Y, Mo, Cu, Zn, Ni, As, Sb, Bi, Ag, Au, Hg and Tl) in the siltstones offers greater value from silicified limestone. In addition to between U and V, W, Zr and Y relationships were high positive due to granitoides which located south of the study area. This indicates that uranium and granitoides from the same origin. In addition to between U and Ba, Cu, Zn, As, Sb, Bi, Ag, Au, high positive correlation coefficients were calculated due to the same origin of hydrothermal fluids. The heavy REEs (Eu-Lu) concentrations were high (>1) in both studied lithological units (siltstones and silicified limestone). The mineralogical studies indicated that the uranium carbonate minerals were enriched in calcite filling fracture in the silicious limestone in alkalin environment as linking to fault zone. The used of D-factor determination of equilibrium state of the studied rocks were chemically analyzed uranium greater than the radiometrically determined uranium reflecting a disequilibrium state characterized by addition of uranium. The origin of uranium mineralization was mainly related to alteration of primary minerals by the action of oxidizing/reducing fluids, then redeposition in other forms. Redistribution by circulating origin of meteoric hydrothermal waters might have taken important role. The utilization of fault/fracture zones and clay-rich horizons in lake sediments may prove useful in the search for U resources. Rock geochemistry findings are evaluated together with lithological and mineralogical data. Consequently, source of carbonate in the environment is siliceous limestones in Kubaca (a) member; source of Fe in the environment is dissemineted pyrites in the siltstones; the source of phosphorus in the environment is apatites which has moved as a result of the decomposition of granitoids. These results depending on pH and Eh conditions in environment indicate that the enrichment of uranium in different forms. Uranium concentrations obtained by dissolving with strong acids and weak acids from stream sediments in the sedimentation basin. Uranium enrichments in compounds such as phosphate, vanadate, carbonate, arsenate indicate that mechanical transport is more effective than hydromorphic transport. Key Words: Geochemistry, Nevşehir, Dadağı, Uranium