Geochemical constraints on the Zola-Chay river sediments, NW Iran: Implications for provenance and source-area weathering

The Zola-Chay River is one of 14 permanent rivers feeding Lake Urmia in northwestern Iran, and a significant amount of material eroded from surrounding rocks has entered this lake. In this study, mineralogy and concentrations of major and trace elements of the Zola-Chay river sediments were measured on a 26 km-long NE–SW trending section with the aim of evaluating the provenance and source-area weathering. Quartz, orthoclase, plagioclase, and muscovite are the principal constituents accompanied by some minor accessory minerals, such as illite, kaolinite, calcite, dolomite, pyrite, hematite, apatite, rutile, epidote, ilmenite, zircon, and monazite. Values of the index of compositional variability (ICV) in the studied samples range from 0.99 to 1.21, indicating that these sediments are immature. The chemical index of weathering (CIW) (54.04 to 61.10), plagioclase index of alteration (PIA) (55.66 to 66.20), and chemical index of alteration (CIA) (62.50 to 72.51) values of the sediments, together with geochemical proxies, such as the K2O/Rb and Rb/Sr ratios, reveal a weak to intermediate chemical weathering in the study area. Multivariate plots of major oxides and trace elements, along with geochemical indicators, such as Al2O3/TiO2, Ti/Zr, Cr/Th, Th/Co, La/Co, La/Sc, Cr/Ni, Th/Sc, Ce/Sc, Zr/Sc, Eu/Eu*, (La/Sm)N, (Gd/Yb)N, (La/Lu)N, and LREE/HREE ratios, imply that the Zola-Chay river sediments probably originated from a felsic–intermediate precursor. Combining the results obtained from field observations and geochemical investigations show that Neoproterozoic rhyolites–rhyodacites along with Precambrian–Paleozoic rhyolites–granites–diorites are the probable provenance of the Zola-Chay river sediments.