2016 NGWA Groundwater Summit

Characterizing Lithium Enriched Brines As Mineral Resources and Reserves

Tuesday, April 26, 2016: 2:10 p.m.
Confluence Ballroom A (The Westin Denver Downtown)
Daniel S. Weber, PG , Montgomery & Associates, Denver, CO
Michael J. Rosko, PG , Montgomery & Associates Consultores Limitada, Santiago, Chile
Jonathan D. Whittier , Montgomery & Associates, Tucson, AZ

Unlike traditional mineral resources that are solid deposits, brine mineral resources are fluid deposits of variable density and mobility.  As an example, lithium enriched brines are hosted in porous- and fractured-rock aquifers, typically within closed hydrologic basins (salars).  Compared to hard rock deposits, the variable density and mobility of these brine deposits present challenges with respect to exploration, characterization, and quantification. The conceptualization and exploration of brine mineral resources, the mining plan, and definition of the mineral reserve for each deposit require not only an understanding of the spatial and temporal variability of brine densities and concentrations, but also the variability of the flow characteristics in the aquifer where the brine is stored.

As outlined by standards and guidelines for quantifying mineral resources and reserves, key variables such as brine volume and grade, aquifer geometry, hydrogeologic unit, effective porosity, specific yield, flow rate, and recoverability are used in order to meet the definition of reasonable prospects of economic extraction and to define the mineral resource.  Conversion of status from a mineral resource to a mineral reserve requires modifying factors ranging from mining methods, to processing strategies, to environmental, social, and permitting aspects of the project.  

Production wells in deeper deposits, or extraction trenches for shallower systems, are generally the mining methods for extraction of brine resources.  Hydrogeologic methods are thus critical to evaluating what portion of a defined mineral resource is economically extractable and can in turn be defined as a mineral reserve.  Consistent with industry guidelines, we use the technical reporting terms “Drainable” and “Extractable” as factors for evaluating and advancing project status from mineral resource to mineral reserve. These hydrogeologic modifying factors are in part supported using exploration results, aquifer testing, conceptual modeling, and hydrodynamic numerical modeling methods simulating wellfield or trench extraction for mining the lithium-enriched brine.

Daniel S. Weber, PG, Montgomery & Associates, Denver, CO
Daniel Weber is a senior hydrogeologist with Montgomery & Associates in Denver, Colorado. He has worked for Montgomery & Associates for 27 years, is a licensed professional geologist, and a long-term member of NGWA. Daniel earned a Bachelor of Science degree in geology from Bradley University and a Master of Science degree in hydrology from the University of Arizona. He has worked in salar environments in South America throughout his career and currently with his colleagues is involved in projects assessing brine-mineral resources and reserves for international mining clients.

Michael J. Rosko, PG, Montgomery & Associates Consultores Limitada, Santiago, Chile
Mike Rosko is a senior hydrogeologist with Montgomery & Associates. In addition to his current role as Operations Manager of the Santiago office, Mike has managed projects in Arizona, Bolivia, Chile, and Mexico. He has spent much of his career at Montgomery & Associates developing new water supplies and assessing aquifer conditions in arid environments, both in the southwestern U.S. and in the desert “salar” region of South America. Mike is a registered geologist in three states (Arizona, California, and Texas). A fluent Spanish speaker, Mike has published several professional papers and presented at both local and international conferences.

Jonathan D. Whittier, Montgomery & Associates, Tucson, AZ
Jon Whittier is a senior member of the Hydrologic Modeling team at Montgomery & Associates with over 14 years of experience characterizing complex hydrogeologic systems and modeling groundwater flow. He has developed models to design and manage wellfields, evaluate capture, simulate groundwater / surface water interactions, and evaluate impacts to environmentally sensitive areas. He has also designed and implemented models that predict the impacts to water resources both during and after the closure of open-pit mining operations. One current focus area is characterizing and modeling brine aquifers in Andean salars to support mineral resource / reserve estimates.