A Conceptual Overview of Surface and Near‑Surface Brines and Evaporite Minerals

Although few of us will personally experience the arid environments discussed in this book, these terrains cover nearly 20% of the continental surface of the Earth. They form in response to a combination of arid or semi-arid climate and a topography that results in the pervasive formation of brine and associated mineral deposits. The salts originate as dissolved solids in the rainfall and from the weathering of minerals as the rain infiltrates in the uplands and flows as groundwater to discharge in the lowlands where salt accumulates. The story sounds simple but understanding the formation of the mineral species and solutes within the hydrologic landscape is complex. The minerals that develop are a function of the input of dissolved constituents, leakage of solutes from the basin, thermodynamic state of the brines, water vapor content of the atmosphere, and the dynamic interplay between hydrology and thermodynamics with varying temperature driving the resulting mineral assemblages.