Abstract
Cherts are commonly found in alkaline saline lakes and have complex origins. This study investigates the deposition of sodium-rich chert in a Paleozoic alkaline saline lake located in the NW Junggar Basin, China, where reedmergnerite and searlesite occur. Comprehensive analyses of core sections, thin sections, micro-XRF, SEM, EDS, EMPA, and LA-ICP-MS were conducted to provide detailed characterization of reedmergnerite and searlesite within the sodium-rich chert, and to discuss the environmental significance of this evaporitic lithology. Furthermore, we propose that sodium-rich cherts may serve as precursors for the formation of reedmergnerite and searlesite within the sodium-rich chert. The transformation of sodium silicate into chert is controlled by meteoric freshwater leaching and other diagenetic fluids. Pseudomorphs of evaporite minerals such as trona and halite occur within the chert matrix, providing sites for diagenetic searlesite precipitation following their dissolution. Reedmergnerite is identified as a relatively stable mineral within the chert, while searlesite is recognized as filling material in evaporite pseudomorphs. Borosilicate, searlesite, sodium-rich cherts, and associated pseudomorphs suggest an “alkaline salt crust” environment, which is significant for identifying paleo shorelines in alkaline saline lakes characterized by intense evaporation, even though these shorelines may have migrated far from the locations of sodium-rich cherts due to rising lake levels during humid climatic periods.
Paper Information
Yu, K., Wang, Z., Cao, Y. and Du, S. (2025) Origin of reedmergnerite and searlesite in sodium-rich chert and their paleoclimatic implications from a late paleozoic marginal alkaline saline lake in China. Carbonates Evaporites, 40, 121. https://doi.org/10.1007/s13146-025-01158-1
