Geochemistry of Daihai Lake sediments, Inner Mongolia, north China: Implications for provenance, sedimentary sorting, and catchment weathering

Abstract

To advance the understanding of sediment distribution, catchment weathering, hydraulic sorting, and sediment provenance in a tectonically stable basin, the geochemistry of surface sediment samples from Daihai Lake in north China is presented. Mud bulk sediments were analyzed for 10 major and 30 trace elements, organic carbon, and nitrogen and for 87Sr/ 86Sr ratios in silicate fraction (acid insoluble, AI) and carbonates (acid soluble, AS). Enrichment in Fe 2O 3, CaO, MnO, MgO, K 2O, and P 2O 5 and their positive correlation with Al 2O 3, Rb/Sr ratios, and bivariate discrimination diagrams of K vs. Rb and Th/U vs. Th suggest low chemical weathering intensity under semiarid conditions in the Daihai catchment. Accumulation of clays in deeper water sites by sedimentary sorting results in an evident distribution of sediment composition with the lake water depth. Although similar chondrite-normalized REE (rare earth element) patterns of lake sediment samples (with LREE (light rare earth element) enrichment, negative Eu anomalies, and an almost flat HREE (heavy rare earth element) pattern) may suggest similar sedimentary source rocks, original sediment provenance can be recognized on the basis of their distinctive 87Sr/ 86Sr (AI) ratios and immobile (Th, Zr, Ti, and Nb) trace element signature, separating from weathering and sedimentary processes as well as from grain size effect.