Geochemical differences between bed and terrace sediments of the Harşit Stream (NE Turkey): Implications for mixed source rocks, weathering and mass transfer

There are minor geochemical differences between Harşit Stream bedandterrace sediments, and these can be owing to the impacts of climatic differences and chemical weathering rather than source rock composition. The bedsediments have lower average SiO2, Al2O3, Fe2O3, K2O, TiO2and MnO concentrations than terrace sediments, but higher concentrations of MgO, CaO and Na2O. The rare earth element (REE) distributions, Eu/Eu*, (Gd/Yb)N, La/Th and (La/Yb)N ratios of the bedand terrace sediments indicate that they derived from a mixture of 3% granodiorite + 50% gabbro + 47% felsic tuff and 5 %granodiorite + 37% gabbro + 58% felsic tuff, respectively. The CIA, PIA, WIP values and ICV, Rb/Sr ratios indicate that the bedsediments are lowly weathered and terrace sediments are lowly tomoderately weathered. The distribution of C-values and Sr/Cu ratios indicate an arid to semiarid climatic conditions for the bedsedimentsand an arid to semi-moist climatic conditions for terrace sediments. During weathering of the mixed source rocks, Na indicates the greatest loss for the bedand the terrace sediments, and P shows the lowest loss for both of sediments. The average of Si, Al, Na, K and Mn exhibits more loss in bedsediments than terrace sediments, the Fe, Mg, Ca and P exhibits less loss in bedsediments than terrace sediments.