Evaporites and brines – geological, hydrological and chemical aspects of resource estimation

Abstract

Modern salt lakes are complex systems which are exploited for a variety of minerals, including solid and dissolved phases (brines). Phases commonly exploited include lithium, potassium and boron minerals, mainly from brines, and solid minerals including halite and gypsum. Resource estimation and successful exploitation of either solid minerals or brines require good understanding of the complex interactions within these systems. This includes careful definition of climate, geology, hydrogeology (hydrology), fluid flow dynamics and lastly chemical ion concentrations. Therefore estimation involves multidisciplinary team work. Brines are mobile resources which change through time, sometimes seasonally, so estimators must understand the climatic, hydrological and geological factors governing flows of both water and salts into and out of the system. Commercial extraction of brines involves brine collection (usually by pumping from wells) at rates that make the extraction economic, so brine resources should include only extractable brines, which are those in accessible aquifers available for pumping. Estimators must take into account potential limits on sustainable extraction rates when assessing the prospects for eventual economic extraction to determine whether a resource is present. Drilling on salt lakes can present significant challenges in safe access, and in recovery of uncontaminated samples of host rocks, which are often unconsolidated, and of brines. The merits of various…