Gustavson Associates, LLC (Gustavson) was commissioned by USA Rare Earth LLC (USRE) to prepare an updated Preliminary Economic Assessment (PEA) for the Texas Mineral Resources (TMRC) Round Top Rare Earth Element Project (Round Top Project or the Project). The Project is located in Hudspeth County, Texas. This technical report presents the results of the PEA in accordance with Canadian National Instrument 43-101 Standards of Disclosure for Mineral Projects (NI 43-101), June 24,2011, and Canadian Institute of Mining, Metallurgy and Petroleum (CIM) “Best Practices and Reporting Guidelines for Mineral Resources and Mineral Reserves”, November 23, 2003. The effective date of this report is July 1, 2019.
The Round Top Project consists of a Tertiary rhyolite intrusion that is enriched in both heavy and light rare earth elements (REEs) and other incompatible elements such as Li, Be, F, U, Th, Nb, Ta and Hf. The stratigraphy is relatively simple, with Tertiary rhyolite laccoliths cutting Tertiary diorite dikes and intruding Cretaceous marine sedimentary rocks. The Project is located in the Trans-Pecos region, and has been structurally affected by Laramide thrusting and folding, subduction magmatism, and Basin and Range crustal extension. The main structures on the property are landslide and slump faulting, and north-northwest-trending normal faults.
Round Top rhyolite is enriched in Heavy Rare Earth Elements (HREEs). Statistical review of the geochemical data shows that an estimated 70% of the total REE’s grade being HREEs. REE mineralization occurs primarily as disseminated microcrystals of varieties of fluorite (such as yttrium-rich yttrofluorite) where HREEs have substituted for calcium, and as other REE-bearing accessory minerals. REE minerals occur mainly in vugs and as crystal coatings, suggesting late-stage crystallization from an incompatible element-rich fluid. Other incompatible elements were concentrated in these late magmatic fluids. Uranium occurs as fine disseminated grains of uraninite
and coffinite. Niobium-tantalum bearing columbite is relatively abundant. Zircon also is relatively abundant and is the mineral containing the zirconium and hafnium.
Several unidentified tin minerals are present, and thorium is contained in thorite and within zircon. Other petrographic elements are also present, some of which will be recovered during a sulfuric acid leach, and which are expected to produce economic minerals. The Round Top rhyolite was divided into five different alteration phases based on the intensity of hematitic and hydrothermal alteration: gray rhyolite, pink rhyolite, red rhyolite tan rhyolite and brown rhyolite in the order of least to most altered. Hematitic alteration is a replacement of the magnetite by hematite and gives the rhyolite a red to pink color. Hydrothermal alteration was late and gives the rhyolite a tan to brown color. Mostly unaltered, gray rhyolite was also documented.
Also see company website: http://tmrcorp.com/projects/rare_earths/
Master's Thesis: https://digitalcommons.utep.edu/cgi/viewcontent.cgi?article=2627&context=open_etd
2013 Version of the NI43-101 Report: http://tmrcorp.com/_resources/pdf/TRER_NI43-101_PEA_FINAL_10Jan2014.pdf
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