Geometallurgical Characterization of Sandstone-Hosted Vanadium Ore from the Colorado Plateau

The La Sal District in the Four-Corners region of the United States is a major domestic resource of vanadium ore. The vanadium occurs in a variety of minerals impregnating sandstones of the Jurassic Morrison Formation. Detailed mineralogic and textural characterization of six ore samples in parallel with beaker-scale acid-leach tests provide insight into potential considerations for metallurgical recovery of vanadium from this ore type. Scanning electron microscopy (SEM) and Tescan TIMA automated mineralogy reveal substantial degree of locking of soluble vanadium-hydroxides in quartz-overgrowths and vanadium-clay particles at -850 μm grind size. Electron microprobe (EPMA) analyses of the ore mineral compositions reveal four primary vanadium hosts – montroseite, duttonite, V-illite and V-chlorite and accessory ore phases uvanite and an unidentified Ti-V hydroxide. Beaker-scale leach tests in dilute H2SO4 and NaClO3 resulted in 14 – 54% vanadium recovery. Comparison of V-illite compositions from heads and tails indicate moderate solubility of this phase – with the average composition of V-illite being reduced from an average of 16.4% V in the head analyses to 10.5% V in the tail analyses in one experiment. Through comparison of vanadium deportment in the heads and the maximum recoveries from the leach experiments it is suggested that V-chlorite is less soluble than V-illite under the study conditions

The process mineralogy of leaching sandstone-hosted uranium-vanadium ores

In the United States, sandstone-hosted ore deposits of the Paradox Basin (Colorado Plateau) are major resources of uranium and vanadium, two metals important to green energy among other applications. Despite historic and current mining interest, and their significance as major domestic resources of critical elements, the geometallurgy of these deposits has received little study. This article documents the geometallurgy and process mineralogy of the U-V ores and identifies the principal barriers to optimal recovery by acid leaching. Most of the metals occur as pitchblende (mixed uranium oxide-silicate), V-hydroxides, V-bearing phyllosilicates, and diverse vanadates of U, Pb, Cu, and other metals. Commercial extraction is by two-stage heated tank leaching with H2SO4 and NaClO3, yielding high U but lower V recovery (70–75% in the industrial operation). Laboratory leaching experiments coupled with comparisons of head and residue mineralogy indicate that the unrecovered U consists of micron-scale pitchblende grains locked within quartz and other insoluble minerals. The principal cause of suboptimal V recovery is the V-phyllosilicates, which show variable but generally poor solubility at room temperatures. An ancillary cause is locking of a small amount of fine-grained V-hydroxide and pitchblende by authigenic quartz and V-phyllosilicates. Comparison with other global V resources suggests that variable solubility of V-phyllosilicate ore minerals may also diminish recovery from more common ore deposit types, such as V hosted in black shales or stone coal, particularly in heap leaching of low-grade ores at coarse grain sizes.National Science Foundation24 month embargo; available online: 29 August 2022This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Petrology and geochronology of Mesoproterozoic basement of the Mount Rogers area of Southwestern Virginia and Northwestern North Carolina: implications for the precambrian tectonic evolution of the Southern Blue Ridge Providence

Results from new geologic mapping, SHRIMP U-Pb geochronology, and petrologic studies indicate that Mesoproterozoic basement in the northern French Broad massif near Mount Rogers consists of multiple, mostly granitic plutons, mapand outcrop-scale xenoliths of pre-existing crustal rocks, and remnants of formerly overlying meta-sedimentary lithologies. Zircon and titanite ages demonstrate that these rocks collectively record nearly 350 m.y. of tectonic evolution including periods of igneous intrusion at ca. 1190 to 1130 Ma (Early Magmatic Suite) and ca. 1075 to 1030 Ma (Late Magmatic Suite) and three episodes of regional metamorphism at ca. 1170 to 1140, 1070 to 1020, and 1000 to 970 Ma. The existence of ca. 1.3 Ga age crust is indicated by (1) orthogranofels of ca. 1.32 Ga age in a map-scale xenolith, (2) inherited zircons of ca. 1.33 to 1.29 Ga age in Early Magmatic Suite plutons, and (3) ca. 1.36 to 1.30 Ga age detrital zircons in meta-sedimentary lithologies. Mineral assemblages developed in amphibolites and granofelses indicate that metamorphism during both Mesoproterozoic episodes occurred at upper amphibolite-to lower granulite-facies conditions. Syn-orogenic Early Magmatic Suite plutons emplaced at ca. 1190 to 1145 Ma are characterized by high-K, variably magnesian, dominantly calc-alkalic compositions, and have trace-element characteristics indicative of continental-arc magmatic origin involving melting of thick continental crust. In contrast, ca. 1140 Ma age quartz syenite displays A-type features indicating derivation from depleted crustal sources with increased mantle input during waning stages of regional contraction. Plutons of the compositionally bimodal Late Magmatic Suite include (1) ca. 1060 Ma meta-granite with geochemical characteristics transitional between silicic rocks of arc systems and post-collisional granites of A-type lineage, and (2) ca. 1055 Ma monzodioritic rocks with A-type compositional characteristics that likely reflect derivation from fertile, mafic sources in the lower crust. Collectively, these data suggest that Mesoproterozoic rocks of the study area preserve evidence of multiple orogenic episodes that likely involved continental-arc development and deformation at ca. 1150 Ma followed by crustal thickening at ca. 1060 Ma. Field relations and geochronologic data indicate that regional uplift and sedimentation occurred at ca. 1100 Ma between the two episodes of overlapping magmatism and orogenesis. The nature and timing of Mesoproterozoic events recorded in basement rocks of the study area illustrate significant differences in the lithologic assemblages and geologic history preserved by Mesoproterozoic basement of the adjacent Shenandoah and French Broad massifs, suggesting that the Blue Ridge massifs occupied different locations within the regional Grenville-age orogen until about 1070 Ma when the effects of Ottawan-age tectonics began to affect both areas. The near ubiquity of Ottawan- age orogenic activity recorded in Mesoproterozoic rocks of the Blue Ridge, other Appalachian inliers such as the New Jersey Highlands, and the Grenville province of Canada, including the Adirondacks, suggests that these formerly disparate terranes were amalgamated to form a common, regional orogen by this time.This study was supported by awards from the Educational Geologic Mapping Program administered by the U.S. Geological Survey (USGS) to George Washington University (GWU). The research also benefited from additional support provided by the USGS Appalachian Landscape Project