Use of Surface Lithogeochemistry to Estimate Magnitude of Blind Uranium Mineralization in Northern Arizona Collapse Breccia Pipes
Lawrence D. Turner, CPG-11408 Irving L. Turner
Abstract
DIR Exploration, Inc., has established a geochemical technology that permits pre-drilling estimation of the magni- tude of uranium resources present in northern Arizona collapse breccia pipes by surface sampling the primary metal leakage surrounding these structures. The accuracy and reliability of the meth- od is sufficient to serve as a rapid and very cost-effective substitute for much of the exploration drilling historically applied in the search for buried brec- cia pipe uranium ore bodies. To date, the surface sampling-based exploration method has been documented to work quite well at the 300 to 400 meter burial depths characteristic of Arizona breccia pipe uranium ore bodies.
Judging by the uranium-mineralized breccia pipe case study reported here, adaptation of the same geochemical approach to the exploration for other ore body types could rapidly and cost- effectively improve the rapidly declin- ing economic mineral deposit discovery rate that is now plaguing the entire metals exploration and mining industry (Schodde 2014), and also reverse the markedly declining utility of exploration geochemistry as an ore body discovery tool (Schodde 2014). In both of these regards, DIR Exploration, Inc., has more recently adapted the same geochemical surface sampling-based method to explo- ration for Carlin-type gold deposits and for bonanza grade low-S precious metal vein deposits, and anticipates eventu- ally doing the same for porphyry- and Mississippi Valley-type metal deposits.
The uranium exploration geochemical method described here was established by early 2010, at the end of a long search for a practical, inexpensive means of distinguishing between economically- mineralized, uranium-bearing collapse
breccia pipes and similar looking barren geological structures located in northern Arizona west of the Navao Reservation. As Figure 1 shows, the drill-hole-free prospect evaluation method described in this report is highly predictive of the amount of uranium ore in any given mineralized collapse breccia pipe.
Three main factors have been deter- mined to govern the extent of uranium and metal sulfide mineralization in col- lapse breccia pipes during the breccia pipe mineralization process. These fac- tors are: (1) timed existence of bacterial feedstock (oil); (2) upwelling, metal-rich brines; and (3) consequent generation of two proximal and coeval geochemi- cal reduction barriers capable of pre- cipitating metal sulfides and uraninite from upwelling mineralizing fluids. See Figure 2.
Four independent geochemical parameters found in metal leakage val- ues from bulk surface rock chip samples serve as numerical proxies for the brec- cia pipe mineralization-controlling fac- tors ust described. Multi-variable linear regression of these four parameters against published uranium reserves- plus-production figures from each test case produced a linear equation that predicts 97.95% of the variation in log value of the uranium resource present in the sampled cases. The statistical nature of the defined linear equation is such that its application to hitherto undrilled brec- cia pipe targets in northern Arizona is very strongly ustified. Test application of the equation to twenty-three unmined breccia pipes with appreciable explora- tion drilling already completed verifies the results of the statistical tests of the linear equation.
A detailed explanation and discussion of the newly established exploration geochemical method, and the original
northern Arizona surface geochemical data, can be found in the AIPG’s E-news in July. Watch for details on AIPG web- site,
www.aipg.org.
Reference
Schodde RC, 2014, “The Global Shift to Undercover Exploration - How fast? How effective?” Keynote paper for the September 2014 Society of Economic Geologists Conference, Keystone, Colorado: http://www.
minexconsulting.com/publica- tions/Schodde%20presentation%20 to%20SEG%20Sept%202014%20 FINAL.pdf
Larry D. Turner, CPG-11408, is a second- generation mineral exploration geologist. He graduated from Eastern Washington State College in summer 1975 with a BS in geology, and thereafter began employment as a ura- nium proect geologist and program manager for Minatome Corporation, working through- out the western US. Following completion of an exploration geochemistry-focused MS geology degree at Eastern in 1981, he briefly worked in petroleum exploration geochemis- try for CITGO and then returned to mineral exploration as Energy Fuels Nuclear’s chief geochemist in northern Arizona breccia pipe uranium exploration. In 1987, he, his father (co-author Irving L. Turner), and his MS thesis advisor, Dr. Mohammed Ikramuddin, formed DIR Exploration, Inc., in order to man- age a breccia pipe uranium exploration oint venture between DIR and the Japanese com- pany, PNC Exploration (USA), Inc. This JV ended in 1993 with the continued and chronic uranium price level slump. DIR worked until 2006 as a mineral exploration contractor and as proect generator. Over 1998-2000, Larry completed an MS in mineral economics at the Colorado School of Mines: some of the skills obtained in this graduate study led directly to the exploration innovation described in the current report. In 2006, DIR oined Takara
www.aipg.org
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