Abstract: The research on chemical characteristics of salt lake mud water in inland arid area is of great importance on understanding water-rock interaction during early diagenesis of mud sediment in arid area deeply. The present study took Xiao Qaidam salt lake mud water in arid area of northwest of China as the research object and analyzed the chemical characteristics of mud water, indicator of which to water-rock interaction during early diagenesis was discussed. The results indicate that the each chemical component content of mud water in different depth is generally higher than that of overlying salt lake water, which is different from that of marine mud water. The rising of salinity for salt lake mud water is owing to intense evaporation near surface and redissolution of salt precipitation in lakeshore. The Na⁺、K⁺、Li⁺ and Cl^- content of mud water in different depth varies little, while the varying ranges of Mg²⁺、Ca²⁺、Sr²⁺、SO^2-₄、I^-、TOC and TNb are relatively large and the of Br^- and B³⁺ content exhibits moderate decrease with increasing depth. The water-rock interaction and biochemical action have occurred to some degree during early diagenesis of mud sediment. The possible main processes include extensive evaporation in shallow surface, precipitation of evaporite mineral, cation exchange, desulphidation and organic matter degradation.

Key words: mud water, hydrochemistry characteristic, water-rock interaction, Xiao Qaidam Lake