URANIUM AND RARE EARTH ELEMENT (REE) RESOURCES IN NORTHERN ARIZONA BRECCIA-PIPE OREBODIES

A unique, polymetallic, uranium-rich, solution-collapse, breccia-pipe (BP) district lies beneath the plateaus and canyons of NW Arizona. It contains large reserves of high-grade U (ave. grade of 0.65% U₃O₈ - Wenrich & Titley, 2008, AGS Digest 22). The Arizona Geological Survey is updating USGS OFR-89-550 which shows 1294 collapse features, some of which are known uranium-bearing breccia pipes (BP), with >2100 additional solution-collapse features. This update is needed to produce a more accurate estimate of uranium resources. Previous resource estimates include the following: (1) A U resource endowment for the 1050 mi² “mineralized corridor” of the BP district has been made by Spiering and Hillard (2013 SME abstract). They inferred a “mineralized corridor” containing most of the mineralized pipes, and calculated U resources at (a) 270 million lbs. of U₃O₈ using VTEM Airborne Geophysics results and (b) 269 million lbs. U₃O₈ using pipe density known from drilling_. (2) USGS Circular 1051 (1990) calculated the U endowment of the entire BP pipe district. Spiering and Hillard (2013) applied these calculations to the “mineralized corridor” with a result of 375 million lbs. of U₃O₈. (3) Using a control area of published detailed surface mapping of solution-collapse features, some with mineralized rock (USGS map I-2440) on the NE portion of the Hualapai Reservation, we calculated 260 million lbs. of U₃O₈ in the “mineralized corridor”. These 3 independent resource estimates average 302 million lbs. of U₃O₈. The estimate by Spiering and Hillard, and that by us, using completely different types of data within different geographic regions of the district (drilling vs. mapping), have come to remarkably similar resource endowment estimates—270 vs. 260 mil lbs of U₃O₈. Using an approach based on USGS OFR-89-550, Reasonably Assured Resources (RAR) are calculated to be 206 million lbs.; comparing this to the RAR for the U.S. of 539 million lbs., the BP district has 38% of the U.S. resources (RAR). REE analyses of BP uraninite ore showed the total REE content of the uraninite to be around 0.43%. Hence, using the U RAR and maximum endowment calculations, between 471,000 and 860,000 lbs. of LREE and 405,000 and 737,000 lbs. of HREE could be produced from the raffinate fluids during processing of the district’s uraninite.