Work

Comparative Hydrochemistry of Brines in Cambrian-Hosted Aquifer Systems: Evidence from Six Representative Regions

Year: 2026

Type: article

Abstract: Comparisons of Cambrian-hosted brines across sedimentary basins are complicated by differences in initial salinity, host lithology, hydrogeological setting, and later fluid circulation. We compiled TDS, major-ion concentrations, stable water isotope values (δ18O and δD), and available 87Sr/86Sr ratios for 164 published hydrochemical records from the Sichuan and Tarim basins, Siberian Platform, Illinois Basin, St. Lawrence Lowlands, and Baltic Basin. The records were assigned to nine basin or sub-basin comparison groups. Total dissolved solids (TDS), Cl− concentration, the ρ(Cl−)/ρ(Br−) mass ratio, and the n(Ca2+)/n(Mg2+) molar ratio differed significantly among the groups. Aggregation by well or identifiable hydrogeological unit retained significant differences in all four variables, while aggregation by source publication preserved the principal regional rankings (Spearman ρ = 0.85–0.98). Among records with complete major-ion data, Na–Cl facies characterized the plotted records from Sichuan, Tarim, Illinois, and the Baltic Basin, whereas Ca–Cl facies characterized most plotted records from the St. Lawrence Lowlands and the Siberian Platform. ρ(Cl−)/ρ(Br−) relationships in Tarim, central Sichuan, Illinois, and some Siberian records were compatible with an evaporated marine component. Elevated ρ(Cl−)/ρ(Br−) ratios in the St. Lawrence Lowlands and northeastern and eastern Sichuan were consistent with additional halite-derived chloride and later fluid modification, while the lower salinity of eastern Sichuan indicated additional dilution. Stable water isotope values indicated regional differences in meteoric-water influence and oxygen-isotope exchange, while available 87Sr/86Sr ratios distinguished basin-specific solute contributions. Together, the major-ion and isotope patterns organize regional brine chemistry along four interpretive dimensions: salinity acquisition, host–rock reactions, burial and hydrogeological confinement, and later fluid circulation. By integrating six Cambrian and Cambrian-connected aquifer systems within a comparative framework in which each record was traced to its original source, this study distinguishes shared hydrochemical characteristics from region-specific pathways of brine evolution.

Source: Water

DOI: 10.3390/w18202504

Authors: Zuping Zhang, Pingheng Yang, Wenjing Guo

Institution: Southwest University

Language: English

Topic: Groundwater and Isotope Geochemistry

Subfield: Geochemistry and Petrology

Field: Earth and Planetary Sciences

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $3,137

Funder: National Natural Science Foundation of China