Geochemical and isotopic characteristics of stream and terrace sediments of the harsit stream, NE Turkey

The current study compares and contrasts the elemental concentrations and the Nd, Sr and O isotopic compositions of sediments collected from the Harsit Stream bed sediments (HSBS) and terrace sediments (HSTS). There are positive correlations between Al2O3 and SiO2, TiO2, Na2O and Fe2O3, K2O in HSBS and between Al2O3 and Fe2O3, MnO in the HSTS samples. Major element components of HSBS and HSTS are comparable to average upper continental crust. Both types of sediments are generally classified as greywacke, based on chemical composition and O–Sr isotopic compositions. TheɛNd(0) andɛSr(0) values range from −0.6 to −5.7 and from 7.1 to 45, respectively, in HSBS; and from −0.7 to −4.4 and from 20 to 54, respectively, in HSTS. The δ18O values range from 8.8 to 11.8 (average 10.8) in HSBS and from 11.3 to 13.3 (average 12.2) in HSTS, which are generally controlled by detrital or authigenic minerals in the studied samples. The average chemical index of alteration (CIA) and, plagioclase index of alteration (PIA) values are high in HSTS, whereas the index of compositional variability (ICV) and weathering index (WIP) values are high in HSBS. Several minor differences were observed between HSBS and HSTS in terms of geochemistry and isotopic compositions that reflect different processes involved in their sedimentation.