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Some Chemical Experiments Bearing on the Origin of Certain Uranium-Vanadium Ores

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Some Chemical Experiments Bearing on the Origin of Certain Uranium-Vanadium Ores SOME CHEMICAL EXPERIMENTS BEARING ON THE ORIGIN OF CERTAIN URANIUM- VANADIUM ORES. FRANK B. 1N]'OTESTEIN. Carnotite is found in many geologicalenvironments and is probablyformed in severalways. At Radium Hill, near Olary, Australia,• it is associatedwith minerals which were probably depositedby hot solutions. In thesedeposits it fills cavitiesand coats the walls of crevicesand may have been formed by sec- ondary processesfrom the associatedprimary minerals. In the United States it is found far removed from igneousrocks, and its ores are supposedto have been depositedby cold ground water solutionsor to be alterationproducts, in place,of vanadium and uranium bearing sediments. The secondary character of carnotiteis practicallyundisputed, although the primary minerals from which the American depositsare derived are uncertain. The relative importanceof the two suggestedmodes of origin is still in doubt. This report deals with an investigationof cer- tain natural solventsand precipitantsof vanadium and uranium, which are believedto throw somelight on possibleprocesses in- volved in at least one of the suggestedmodes of origin.2 • Crook, T., and Blake, G. S., "On Carnotites and an Associated Mineral Complex from South Australia." Min. Mag., Vol. I5, p. 27I, I9IO. 2 Some of the more important publications are: Hillebrand, W. F., and Ransome, F. L., "Carnotite and Associated Vana- diferous Minerals in Western Colorado," U.S. Geol. Survey Bull. '262, pp. 9-3I. Boutwell, Jl M., "Vanadium and Uranium in Southeastern Utah," U.S. Geol. Survey Bull. 260, pp. 2oo-2m. Gale, H. S., "Carnotite in Rio Blanco County, Colorado," U.S. Geol. Sur- vey Bull. 315, pp. IIO-Xt7. Gale, H. S., "Carnotite and Associated Minerals in Western Routt County, Colorado," U.S. Geol. Survey Bull. 340, pp. 257-262. Moore, Richard B., and Kithil, Karl L., "A Preliminary Report on Uranium, Radium, and Vanadium," U.S. Bureau of Mines Bull. 7o. 5 ø ORIGIN OF UR,•NIUM-V,•N,•DIUM ORES. Carnotiteis essentiallya vanadateof uraniumand potassium. Other bases,especially calcium and barium, and severalof the metals,are thoughtto replacepart of thepotassium in somecases. I-Iessa givesthe formulafor carnotiteas K20'2UOa'V2Os-XH•O. It is usually'associated with and probablyforms isomorphous mixtures with tyuyamunite,4 CaO-2UOa.V•O'5.XH•O. The carnotitesare nearly always associatedwith amorphousores of vanadiumcontaining minor amountsof uranium. The compo.- sitionof theseores is uncertain,but theyare probably oxides and silicates. The principal carnotite depositsof the United States are located in the plateau country of southwesternColorado and southeasternUtah. Of thesethe most productiveoccur in or near the Paradox Valley, Colorado. Others are worked at sev- eral points in southernUtah. Minor depositshave been dis- coveredin northwesternColorado. A depositso far of no com- mei-cialimportance islocated near Mauch Chunk, Pa. Carnotite alsooccurs as an accessorymineral in the roscoelite5 deposits near Placerville, southwestern Colorado. Fleck, Herman,'and Haldane, William G., "A Study of the Uranium and VanadiumBelts of SouthernColorado," Report of the State'Bureauof Mines, Colorado, x9o5-•9o6. Wherry, Edgar T., "Carnotitenear MauchChunk, Pennsylvania," Bull. U. S. Geol. Survey No. 58o, pp. •47-•5x. Hess, F. L., "A Hypothesisfo.r the Origin of the Carnotitesof Colorado and Utah," EcoN. G•or..,Vol. 9, PP. 675-688. Hess,F. L., "Noteson the VanadiumDeposits near Placerville, Colorado," U.S. Geol. Survey Bull. 530, pt. •, pp. •42-I56. Hess,F. L., "Vanadiumin theSierra De LosCaballos, New Mexico,"U.S. Geol. Survey Bull. 530, pt. •, pp. •57-•6o. Hess,F. L., "Carnotitenear Green River, Utah," U.S. Geol.Survey Bull. 530, pt. •, pp. •6•-I64. Lindgren,Waldemar, "Copper, Silver, Lead, Vanadium, and UraniumOres in Sandstoneand Shale,"EcoN. GmL., Vol. 6, pp. 568-58•. Emmons,W. H., U.S. Geol.Survey Bull. 625,pp. 43o•-435. Crook, T., and Blake, G. S., "On Carnotite and an AssociatedMineral Complexfrom South Australia," Min. Ma#., Vol. •5, p. 27•, •9Io. a Hess,F. L., "A Hypothesisfor the Origin of the Carnotitesof Colorado and Utah," Ecoa. GF•oL.,Vol. 9, PP.675-688. • Idem. 5Hess, F. L., "Noteson theVanadium Deposits near Placerville, Colo.," Bull. U.S. Geol.Survey No. 530,Pt. I, pp. x4•-I56. 52 FRANK B. NOTESTEIN. CHARACTER OF TtIE DEPOSITS. The Coloradoand Utah depositsare in white to buff, mod- erately coarse,cross-'bedded sandstones of Jurassicage. The bedsare usuallyflat or dip at low angles,but a few depositsare in bedswhich dip steeply. The productivebeds are hard and massiveenough to form the canyonrims and hogbacksso char- acteristicof western slope topography. Exposurestherefore are abundant. The carnotitein thesedeposits is an amorphous dusty coating on, or matrix between,grains of sand. It also coatsthe rock alongjoint planesand fractures,and fills openings causedby rock movements. The carnotitedeposits are small and lenticular, and conform to the beddingplanes of the rock. They are rarely over IOO feet in lateral extent and vary from a few inchesto severalfeet thick. Their distribution is very irregular. Many of the depositsare interbeddedwith thin beds containingdark colored amorphous ores of vanadiumwith only small amountsof uranium. Some, also, are found a'bove thin shales. Nearly all of the ore-bearingbeds are notably rich in fossil material made up largely of either petrifiedor carbonizedwood. Thin beds of carbonaceous material occur in which the fossils are indistinct but in which ferns and rusheshave been recog- nized. The carbonaceousmaterial is commonlyrich in vanadium, and petrified logs partly replacedby carnotitehave been found. The apparent abundanceof carbonaceousmaterial and plant fossilsin the ore-'bearingbeds is suggestivein view of the oc- currenceselsewhere of vanadium in coals,asphalts, and also in plant ashes.6 However the abundanceof carbonaceousmaterial in carnotitedeposits is not universal and may have no generic significance. The McElmo formatio.n, in which the Paradox Valley camoritedeposits occur, carries abundant petrified wood where exposednear Norwood, Colorado (between Placerville and Paradox Valley), but no carnotitehas yet beendiscovered in that locality. 6 Clarke, F. W., ",The Data of Geochemistry,"U.S. Geol. Survey Bull. 6•6, p. 705. ORIGIN OF URANIUM-VANADIUM ORES. 53 The ore-bearingsandstones are cementedby silica, calciteand gypsum,7 the cementprobably varying from place to place. It is, of course,probable that much original calcite has been re- placed by silica or convertedto gypsumby sulphateground waters. The carnotitedeposits typically occur in "rim rocks" along the sidesof canyons,and the ore almost universallydies out when followeda short distanceinto the hill. The depositsap- pear to be very superficial,a characteristicwhich was emphasized by Ransome,s who suggested,also, that the arid conditionof the dimate mighthave something to do with this surface.deposition. However, a few pocketshave beendiscovered which did not out- crop. There are also depositswhich occuron gently dipping mesa surfaces,the ore being so close to the surfac• as to be worked.by open cut. The shallow.overburden of manyof the depositssuggests that much might be learnedabout the extent and distributionof the depositsby systematicdrilling. Whether the apparentrelation to surfaceoutcrops along canyons is an es- sentialfeature or not canbe determined only by deeperand more systematicunderground exploration than has yet beendone. It has beenshown by severalwriters who have discussedthe subjectthat carnotiteis depositedalong fracture lines within the ore-bearingbeds even where the fracturesare very recen•and dueto slumpingon hillsides?This conditionpoints to solution by descendingground waters and to redepositionon exposure to air. The depositat MauchChunk, Pa., is in Pottsvilleconglom- erate just above its contactwith shales. The carnotiteis asso- ciatedwith lenses of blackvanadiferous shale. Wherry TM states that"the mineral presents the form of anamorphous tominutely crystallinebright yellow coating orimpregnation ina conglom- 7Hess, F. L., "A Hypothesisfor the'Origin oœ the Carnotitesoœ Colorado and Utah," Ecoa. G•t,., Vol. 9- 8 Hillebrand,W. F., and Ransome,F. L., op. cit. 9 Hillebrand,W. F., and Ransome,F. L., op. cit. x0Wherry, Edgar T., "A NewOccurrence of Carnotite," Am. Jour. Sci., 4th Ser., Vol. 33. 54 FRANK B. NOTESTEIN. erate, often penetrating cracks in quartz pebbles." He says further of this deposit"It is evidentlysimply a precipitatefrom the ground water and can be seenin the processof formation where water trickles out from the cracks in the rocks. "•x An analysisof this groundwater wouldbe of very great interest. ORIGIN OF TI-IE DEPOSITS. Becausethe principal carnotite depositsare distant from igneousrocks the possibilityof origin throughhydrothermal ac- tion hasgenerally been rejected. Hess,•' however,considers this hypothesisin connectionwith the southwesterndeposits. Threehypotheses of originhave been advocated, as follows: I. First, that minerals carrying vanadium and uranium were widely disseminated,by mechanicalsedimentation or chemical precipitationthrough the bedsnow, or formerly, overlying the ore-bearingrocks and that these minerals have been dissolved by ground waters and the metalscarried down and reprecipi- ratedat the positionwhere now foundthrough some such agency as calciteor organicmatter or throughoxidation near outcrops. Ransome•a statesthat "the recencyof the depositsand the fact that they are sometimesdirectly connectedwith faults
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