Geochemistry, Depositional Conditions and Provenance of the Late Devonian Carbonates, in the Gölboğazı-Hadim-Konya Area, Southern Turkey

Abstract

Twenty-five carbonate samples selected from the four sections notation as A, B, C, and D of the Late Devonian Gölboğazı Formation in the Gölboğazı-Hadim-Konya area, Southern Turkey were analyzed for major, trace and rare earth element concentrations to evaluate depositional conditions and source of rare earth elements. The Gölboğazı carbonates show non-seawater-like slightly MREE enriched relatively LREE and partially HREE depleted, weakly fractionated, more or less flat shale-normalized REE+Y patterns. They have partially high (Pr/Yb)SN ratios from pure marine carbonates, almost entirely chondritic or sub-chondritic Y/Ho ratios, and generally strong positive correlation of ΣREE with Y, Al, Zr, Th, K, Ti, Fe, Na, Si, Hf, and Nb that are in response not only shale contaminant but also the incorporation of near-shore colloids including Feoxyhydroxides. However most of the limestone samples from the A, B, C, and D sections have seawater-like some REE+Y signals like slightly negative Ce, and also positive shale-normalized (Y/Ho)SN anomaly and LREE depletion referred to as (Pr/Yb)SN. The (Y/Ho)SN ratios of the Gölboğazı carbonates do not show a clear correlation with (Pr/Yb)SN and (La/La*)SN ratios and also Zr concentration that is probably resulted from freshwater input into the prototethyan seawater. The MgO contents of the Gölboğazı carbonates show a strong negative correlation with ΣREE, and no correlation with (Pr/Yb)SN, Ce/Ce*, La/La* and Y/Ho values, suggesting that REE distribution in the Gölboğazı carbonates have not been influenced from the dolomitization process, which was most probably mediated by seawater-like fluids diluted by freshwater inputs. Although ΣREE, Al, Fe, K, Na, Si, and Ti concentrations of the sample groups have a strong positive correlation with Eu concentrations, no correlation with Eu anomaly that may be related to the presence of feldspar rather than hydrothermal events, diagenesis, and also metamorphism. Some critical ratios, La/Sc, La/Co, Th/Sc, Th/Cr, Th/Co, and Cr/Th, for the origin of the REEs indicate that the terrigenous materials in the Gölboğazı carbonates have probably been sourced from intermediate to felsic igneous rocks. Geochemical data reveal that the variable extents of four-component mixing of seawater are characterized by authigenic carbonate, which inherited seawater-like Y, Ce, La, and Gd anomalies and LREE depletion patterns, dolomitizing fluids with low REE, terrigenous materials including Fe-colloids and fluvial freshwater with HREE depleted, MREE enriched characters.