Ground-water control of evaporite deposition

Economic Geology
By:  and 

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Abstract

Topographically closed basins may be hydrologically open as a result of seepage losses to underlying or surrounding ground-water systems. In such cases, these losses can have a substantial control over the suite and the thicknesses of evaporite minerals formed in the basin. The ratio of ground-water outflow to inflow (flux ratio) in hydrologically open basins is as important in determining the mineralogy and thicknesses of evaporite deposits as the solute composition of the inflow water. Attainment of steady state flux ratios permits large thicknesses of two or three minerals to form rather than thin veneers of many minerals. The presence or absence of glauberite, mirabilite, halite, bloedite, polyhalite, and hexahydrite, caused by subtle changes in the ground-water seepage is illustrated using an example from the Southern High Plains of Texas and New Mexico. However, the model is general and is applicable with any solute composition including that of seawater and the use of surface rather than ground water. An analytical, lumped parameter, solute mass balance model is developed to define the concept of a ground-water flux ratio as it applies to topographically closed basins in which evaporation exceeds precipitation. Diffusion, advection, and density-driven flow are proposed as mechanisms by which solutes can escape to the ground water from these closed basins. The geochemical reaction computer program PHRQPITZ is used to document the effects of various flux ratios on the mineralogy and thickness of deposits. Solute analyses used in conjunction with the model can be used to screen prospective basins as well as to provide insights for exploratory drilling program.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Ground-water control of evaporite deposition
Series title Economic Geology
DOI 10.2113/gsecongeo.85.6.1226
Volume 85
Issue 6
Year Published 1990
Language English
Publisher Society of Economic Geologists
Contributing office(s) Toxic Substances Hydrology Program
Description 10 p.
First page 1226
Last page 1235
Country United States
State Texas, New Mexico