Shallow groundwater chemical evolution, isotopic hyperfiltration, and salt pan formation in a hypersaline endorheic basin: Pilot Valley, Great Basin, USA

• Published in: Hydrogeology journal Vol. 29; no. 6; pp. 2219 - 2243
• Main Authors: Mayo, A. L., Tingey, D. G.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.09.2021; Springer Nature B.V
• Subjects: Alluvial basins; Alluvial fans; Aquatic Pollution; Aridity; Bedrock; Boron; Brines; Capillarity; Carbonates; Chemical evolution; Clay; Clay minerals; Dry season; Earth and Environmental Science; Earth Sciences; Economics; Evaporation; Evolution; Flooding; Floods; Fractionation; Geology; Geophysics/Geodesy; Groundwater; Groundwater flow; Groundwater quality; Hydrogeology; Hydrology/Water Resources; Iodine; Isotope fractionation; Lithium; Magnesium; Metals; Mountains; Playas; Potassium; Salt; Salt flats; Salts; Sediment; Sediments; Sodium; Sodium carbonate; Sodium sulfate; Travel time; Tungsten; Valleys; Waste Water Technology; Water Management; Water Pollution Control; Water quality; Water Quality/Water Pollution; United States > US; Great Basin; Isotopic fractionation; USA; Fresh–salt water relations; Hyperfiltration; Geochemical evolution
• ISSN: 1431-2174; 1435-0157
• DOI: 10.1007/s10040-021-02371-7

Endorheic basin brines are of economic significance as sources of boron, iodine, magnesium, potassium, sodium sulfate, sodium carbonate, and tungsten, and they are a major source of the critical metal lithium. Although evaporation is the primary hypersalinization driver for evaporative water bodies, recent investigations have proposed more novel mechanisms for some subsurface brine. This investigation explores shallow groundwater hypersalinization. The chemical evolution and isotopic fractionation of shallow hypersaline groundwater in the clay-rich arid endorheic basin sediments of Pilot Valley, Great Basin (USA), were investigated. Groundwater evolves from fresh in the mountain bedrock and alluvial fans, to brackish and saline at the alluvial fan–playa interface, and to hypersaline in the upper 12 m of basin sediments. Alluvial fan systems are isolated from each other and have varying groundwater 3 H and 14 C travel times. Nonevaporative in-situ isotopic fractionation of up to −8‰ in δ 18 O is attributed to clay sequence hyperfiltration. Groundwater flow-path sulfate and chloride mineral dissolution is the primary driving mechanism for both interface and basin groundwater evolution. Evaporation only impacts the groundwater quality in a small portion of the basin where the groundwater is within ~1 m of the ground surface. Here capillary action carries dissolved soluble salts to the land surface. Episodic flooding redissolves and carries the precipitated salt to the annually flooded salt pan where it accumulates as a salt crust during the dry season. The Pilot Valley model may help explain the buildup accumulative layers of soluble salt that when remobilized becomes subsurface brine.