University of Nevada, Reno The Impact of Geological Environment on the Lithium Concentration and Structural Composition of Hectorite Clays A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Hydrology By Claude Lamy Morissette Dr. Lisa L. Stillings/Thesis Advisor May, 2012 © by Claude Lamy Morissette 2012 All Rights Reserved THE GRADUATE SCHOOL We recommend that the thesis prepared under our supervision by CLAUDE LAMY MORISSETTE entitled The Impact Of Geological Environment On The Lithium Concentration And Structural Composition Of Hectorite Clays be accepted in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Lisa Stillings, Advisor John McCormack, Committee Member Jonathan Price, Committee Member Mark Coolbaugh, Graduate School Representative Marsha H. Read, Ph. D., Dean, Graduate School May, 2012 i Abstract Hectorite is a Li-rich trioctahedral smectite with reported concentrations varying from 0.16% to 0.74% Li, where Li can occur both in the octahedral and the interlayer sites of the mineral structure. It forms either authigenically or as an alteration product under both low temperature and hydrothermal conditions. The objective of this research is to characterize the Li concentration and structural composition of hectorites from 4 sites in the western USA believed to have formed under different geological environments. The hypotheses are: (1) the clay structure will be dependent on its formational origin, and the lithium content will be positively correlated with temperatures of formation; (2) the layer charge and cation exchange capacity will be proportional to the structural lithium content of the clay. A suite of 18 samples was collected for this research: 6 samples from the Esmeralda Formation in Clayton Valley NV, believed to have formed under low temperature conditions (<100°C); 1 sample from Fish Lake Valley NV, 1 sample from Hector CA and 9 samples from the McDermitt Caldera NV, believed to have formed under elevated temperature conditions (>100°C); and 1 sample of synthetic hectorite. All samples were cleaned using a 2-step method of size separation and carbonate dissolution to concentrate the clay fraction and remove the non-clay minerals. The samples were analyzed using X- ray diffraction (XRD) to determine their structure, major and minor element chemistry to determine their composition, cation exchange capacity (CEC) and layer charge to ii evaluate the effect of lithium concentration and clay structure on both properties, and scanning electron microscopy (SEM) to determine the morphological characteristics of the clays. The rock samples were also examined under a petrographic microscope and with the XRD to identify the associated minerals and their textural relationships. Random XRD profiles indicate that the cleaning procedure was effective at removing impurities from the samples. These profiles, along with basal-oriented XRD profiles (air- dried and glycolated) show the majority of the clays to be hectorite, with a few of the McDermitt samples having an illite signature consistent with the mineral tainiolite. The Clayton Valley samples were a mixture of illite and smectite, with the smectite component too small to be clearly identified. These results are consistent with the chemistry and the formulas calculated for all samples. The Li concentration of the purified clay samples varies from 0.1% Li in Clayton Valley to 1.2% Li in McDermitt. Most samples, excluding Clayton Valley, are Mg rich (>10% Mg) and Al poor (<3% Al) and have high fluorine concentrations (up to 6.5% F). The high lithium and fluorine contents of the clay samples indicate the deposits from Hector, McDermitt and Fish Lake Valley formed under hydrothermal conditions. Clays at Hector formed through the alteration of volcanic ash by hydrothermal fluids, the degree of alteration being recognized by the purity of the clay and the absence of zeolites. Clays in Fish Lake Valley most likely formed through direct precipitation from hydrothermal fluids, given the close relationship with calcite in the groundmass. Clays at iii McDermitt most likely formed through alteration of pre-existing sediments, given layering visible in all samples. Furthermore the presence of tainiolite could confirm the hydrothermal origin, since tainiolite has previously only been identified in pegmatites and in rocks that were hydrothermally altered. Clays from the Esmeralda Formation in Clayton Valley most likely formed through direct precipitation from low temperature pore fluids, given the dioctahedral structure, low lithium and fluorine concentration, and close relationship between the clay and calcite in the groundmass. These results are consistent with the proposed model for lithium-rich clay deposits. The 1st hypothesis is supported by the results of this work and we can conclude that clay structure and lithium content are dependent on the formational origin and positively correlated with temperatures of formation. The 2nd hypothesis is partly supported by the results, as a positive correlation can be determined between lithium content and octahedral layer charge, but the relationship with the CEC is inconclusive, as the CEC is dependent on the type and expandability of the clay. iv Acknowledgements This work would not have been possible without the support of the companies whose deposits are the subject of this thesis. Dennis Bryan from Western Lithium has provided samples, access to their Kings Valley lithium deposit in McDermitt and financial support as well as being a member of my thesis committee. Joyce Fitzerald from Elementis Specialties and everyone at the Hector Mine have provided access to the mine and allowed us to collect samples from the mine. Melissa Jennings and Joe Dunn from Chemetall Foote have provided access to Clayton Valley and allowed us to collect samples. Derek Amen from American Lithium Minerals has provided us with a sample from their Borate Hills property in Fish Lake Valley. Finally, Don Eisenhour from American Colloid has provided a sample from their hectorite deposit in McDermitt. Thanks to all of you for sharing information about your property and about the formation of the deposit. Of course, I thank my advisor, Dr. Lisa Stillings, for suggesting lithium as a topic, allowing me to work up such an interesting project, and for the support, both moral and technical, as I went through the ups and downs of graduate school. The U.S. Geological Survey, Mineral Resources Program has provided ample resources, both material and financial. This project is also financially supported by the Society of Economic Geologists through a student research grant from the Hugh E. McKinstry Fund. Finally the Department of Geological Sciences and Engineering, the Graduate Program of v Hydrological Sciences, both at the University of Nevada Reno, and the Desert Research Institute have provided financial support through teaching and research assistantships. The faculty members of my committee, Dr. Jonathan Price, Dr. Mark Coolbaugh and Dr. John McCormack, have provided good advice throughout this process and have always been available when I needed help. Last but certainly not least, my friends and family, for providing all the moral support I needed throughout this process. vi Table of Content Abstract........................................................................................................... i Acknowledgements ...................................................................................... iv Table of Content .......................................................................................... vi List of Tables ................................................................................................ ix List of Figures ................................................................................................ x Introduction .................................................................................................... 1 Conceptual Framework ....................................................................................................... 2 Objectives and Relevance of Research ............................................................................... 5 Geological Settings ......................................................................................... 6 Hector, CA .......................................................................................................................... 6 Clayton Valley, NV .......................................................................................................... 11 Fish Lake Valley, NV ....................................................................................................... 17 McDermitt, NV ................................................................................................................. 20 Methods......................................................................................................... 25 Sample Acquisition ........................................................................................................... 25 Cleaning Procedure ........................................................................................................... 26 Size Separation ............................................................................................................. 26 Removal of Carbonate Phases ...................................................................................... 29 Chemistry .........................................................................................................................