Travertine Deposition Environment and Influencing Factors of the Erdaohai Unit, Mounigou Vally, Eastern Margin of Qinghai-Tibet Plateau, China

Mounigou Vally is a typical karst travertine scenic area located on the eastern margin of the Qinghai-Tibet Plateau. It is an important part of the Huanglong World Natural Heritage site and is divided into two independent sub-scenic units: Zaga Waterfall and Erdao Hai. Erdao Hai primarily showcases its stunning natural landscape through a series of interconnected travertine lakes. This study analyzes the current water quality through statistical methods, and identifies the hydrochemical types using Piper trilinear diagram. The sources of the main ions in the surface water of the Erdaohai Unit and their influencing factors are discussed using Gibbs diagram and ion correlation analysis. The results show that the pH of the surface water in the Erdao Hai unit ranges from 6.29 to 8.33, and the total dissolved solids (TDS) range from 160 to 1400 mg L–1. The main contributors to TDS are Ca2+, Mg2+, and $${\text{HCO}}_{3}^{ - }$$ . The dominant cation is Ca2+, and the dominant anion is $${\text{HCO}}_{3}^{ - }$$ . Further analysis using the Gaillardet model reveals that most ions are influenced by the weathering and dissolution of carbonate rocks. The hydrochemical type is $${\text{HCO}}_{3}^{ - }$$ –Ca2+. The water chemistry composition is primarily controlled by water-rock interactions and weak ion exchange, with CO2 degassing promoting an increase in the Calcite Saturation Index (SIc) and water pH. The findings of this study reveal the environmental conditions and influencing factors of travertine deposition in Erdao Hai, providing insights that contribute to the scientific management of water resources and the local economic and social development.