- -. - - Part 15. .DETAILED CHEMICAL AND MINERALOGICAL RELATIONS IN TWO
...... - :.' ...... ,. . FIGWE48. Sketch of the upper stope~of the Mineral Joe No. I mine-,; ______'______1______i--,l_____ .i 167 - .- ... . :., 49. Sketch of the Mineral Joe No. 1 mine wall ______- ______2: ______.'. 107 'i_I. - SO. Graph showing distribution of several elements across the Minerd 1 mine channel sample:------:---- 172 Joe Xo. ~. . . ~ ...... - + . . _.: .. 61. Distribution of uranium, vanadium, and organic carbon ___ _------__--____---...... ------I------.--- __--.~ ... .L-!73 L. - .- , ______--___------62; -Plot-- of-log- U agam$-log equivalent U; ------5 .%miquantitative apectrographia .-Sketch of the ,workings...... of the Pirgin,No;3 mine.:,; ...--i. ^c .%ineralo$a. &position of Bpeaime&'of ...... the ..,... =..-... Nc.3 mine channel sample,:.- ...... Virgin ....5&-&qiqunntitative epectrographic-.andy&s- ;;,,;,,,-;;,-,-;;-;,~-rr'_-~_~~~-~~~.~-.~--~~=---~~~~--~.~--182...... :...... :: i.7::. ..
Phllosopby. 165 / 166 - GCOCHEMISTRT IND MISERALOGT. COLORLDO PLATE-IU LR.LSIL-11 ORES
that iron is present as both Pe(I1) and Fe(III), the latter ABSTRACT believed to hare been present in the primary clays of the un- Channel snmDies from t,\.o mines on the Colorado plateau mineralized rock; and that some of the uranium is present as have heen studied in detail both mineralogicalig and chemically. U(1-I) in addition to the U(IV) in the cottinitc. All evidence -4 channel from the Mineral joeso. 1 mine, JI~~~~~~~points to weak oxidation of an ore once iiaviug a somewhat County, Colo., extends from unmineralized rock on one side, lower state- through a of mineralization, into onlp The channel samples from both the JIineral Joe 30..1 mine and the Virgin No. mine are believed to have been essentially . .. mineralized rock. The unmineraiized rock is a fairly clean 3 - . . quartz sand cemented with g)Tsum, and contains only minor -identical in minera10m prior to oxidation by Weathering: .. amounts of clay minerah. One boundary betmeen unmlneral- vanadium Was Present a V(II1) in montroseite and V(IV) in ked and mineraiixed rock is quite sharp and is nearly at right * the vanadium clays ; uranium mas present largely as n(lv)in angles to .the bedding. Vanadium minerals, chiefly mh& cofflnite and/or uraninite. The Mineral Joe No. 1 mine channel ’ .. ;. . ’.- -..- . . .. layer dca-montmorulonite and chlodte-montmofllodte, is now OXidhed. ;.. are abundant throughout the minerallzed zone. Escept In the .- :: Vanadium clays are unquestionably formed abundantly dnr- ,’-< dark “eye” of the channel sample, the vanadium clay minerals tng the primary mineralization. and they persist with a mini- ’. : :. are accompanied by hewettite, carnotite, Uuyamunite, and prob-:; _mum Of alteration during much of the weathering. They sug- ..:.:. .. ably unidentified vanadates. In the dark “eye,” pnrnmontrose :-gest-.that the vanadium is carried as F( IV) in tlie oreforming lte, pyrite, and marcasite are abundnnt, and are bordered- --fluids; it seems likely too ‘that the uranium Is carried as a on each side by a zone containing abundant con-usite. No recog- u(1’1) ion.
- ..nizable uranium minerals mere seen in the paramontroseite zone ...... I...... ,. . although uranium is abundant there. CoaIy materia1 la recog- ; ‘;:?: .. 1 - - -. . . . INTRODUmON .. -: . . I. . . . - I: . nimble throughout .all of the channel, but is most abundant In ,:- ;i. -:. .::..;.-.~ .---I-_. - -’*-. --..y-- - .. . P.:. . .. _i. and near the dark “eye.” .Detailed chemical studies ahom a gen- .;- i Uiltil the last fer-ye& uranium-vmadium-Ores . :. ernl increase in Fe, Al, U, and V, and a decrense in SO4= toward , .in the developed usan&.tonetypen,deposi~ of the cola- the ‘‘eye” .of the channel. --Reducingcapacitystudies indicate -.. mdo Plateau contained chiefly carnotite (or tyuyamun- . :.that V(IV) and Fe(II) are present in theFclay minerals :-.-. throughout the channel. but only in and near the “eye” are other : ite) and vanadium clays together a host Of minor .. v(Iv) minernis present (parmontroseite and corvusite). The -uranium and vanadium minerals. Escept in the clays, .. - ... . uranium is everywhere serivalent, although its state of combina- the uranium and vanadium were usually present in .. tion Is conjectural where it is associated with paramontroseite; their highe& oidation stateu(m) and V( V). . For ..Where ‘the ore boundary is sharp, the -boundary of introduced lGk of reason to tliink’otherivise, these rere commonly trace elements la equally sharp. Textural and chemical rela- - .- _. ..
’ . -.tions leave no doubt that the “eye” is a partially oxidized I- COnsidered ‘$rhaq”’ .ores and ideas of their Fnesis . remnant of a former lower-valence ore, and the remainder of -. were bssed on this concept. Recently, many so-~dkd .. . the chanuel is a much more fully oridlzed remnant. -.-“black ore” deposits, both large and small, hare been .. .-. A channel snmple from the Virgin KO. 3 mine, AIontrose . . discovered and developed; tilese share many cornon . . - County, Colorado, extends from weakly mineralized sandstone -; geologic characteristics with the carnotite-bearing ores -. .. i-on-bdhsides -through a~~iiilfi6rnlized.- - . - . .. . -tnt_r_al-zone. .-~e.weaklg.minernlized is a poorly sorted.sdndstone.~i~~nddiffer primarily iithe oxidation state of the con- .-.I:.-.. . . common detritnl ciny iirtin@Fcuijfite-iini mka ‘laper -mtca:---bined uranium, iron, and vanadium. . Insome deposits, . montmorillonite are abundant interstitial to the quartz grains. .: the carnotite Ores Eade at depth kt0 the %la& ores,” No distinct vanadium or uranium minerals are recognizable. and in othels fie two occur rn tile cq,lack although the clny minerals are vanadium-bearing. Euhedral ores” is common as uraninite and’cofhite, and ..--pyxite mins and .ee!eninn~nlen~-areqresentbuJ-rare. The .- U(IV) -ronq~y minernitzed-mk b-sepamted-from -the weakly min- .‘t’.(rf:+d-VWq .___:are ‘common in hydmted_.osides___.__-. -. .-. -. -.. - ud hydrosides as weU.G clays . . .. .: ernlized rock by a .narrow transition zone which only approxi-. . .L.-. :. . . . -_ :--_..- ,*-. - --. >. ..- mates the bedding planes. It contnine abundant vanadfum- &-‘deposib ‘contalGg lo ience meiaIs are - bearing..clny-mlnerals (predomlnantl;r .chlorite). .bterstittalto. b’ -- the-qunrtz”graiiis,-and apparently replncing them. --Panmont- thought be’ &~~~~Lp~~~fl-orefro& which the. . ..- mseite is mmmOn and is intergown with the chr minemh. carnotite depoGts kere derived by oxidationduring Pyrite and marcasite are present, chiefly in or nenr the abun- weathering (Garrels, 19%). Since some single deposits dnnt blebs and fragments 02 carbonaceons mnterinL Selentnn commonly contain figh-valence oms flint grade bto galena le rnrely present, nnd generally in or near carbonaceous :. low-vrrlenceores, we felt it be fruitful to dudy .- material. Cofenite la the only uranium mineral identfaed ; it is .. . detail the nature of the changes the mineralogy, extremely flnegrnlned nnd was identifled only In X-rn,V-dif: -.in in 4ractlon patterns of heavy separates. Dlstflbution of trace element distribution, valence state, and dationOf host elements Is not clear; some are consistently high in the strongly ::rock to mineralization in a channel samplecrossing from . - mineralized rock, and some are consistent4 low. .The trace 1.: one type’ of ore to the other. Bfomover, since much les~ -.:-element compasltlon of the unminernllzed rock la not hewn.- is knoffn about the lo&-valence or= and &eir.mlation Chemlcol etudles show a very abrupt rise In the .total U, V, . the and Fe from the weakly mineralized to strongly .minerallzed host r&k, we‘felt it desirab1e;to study th&k .;::rock. . Reducing capacity atudles indicate ‘that.,.most of the nme’way,but le= intewively.i:It wm hoped that these. vnnndium is present as V(IV). but some la present 88 V(V) ;= udies might lead to ‘a.more specific knowledge of the 3
.. - DET-IILED CHEUICAL ASD ~IISElMLOGICALRELATIOSS IS TWO \.;\NhDIU~I-UR.~~IUJIORES 167
nature of the alteration of the ores, at least for the deposits studied. Results of the study of two cliannel samples are reported below. We are indebted to John C. Hathaway, Jr., and Jlargaret D. Foster, for discussions on the character of the vanadium-bearing clay minerals. Horard T. Evans, Jr., and A. E. Flint assisted Garrels in select- ing and collecting the channel sample from the Mineral Joe No. 1 mine. John C. Chandler assisted with the chemical laboratory mork. Lillie B. Jenkins was of great help in selecting a consistent and reliable method for the determination of reducing capacity. ... _.... _- ..'..a.. _F.- :2,..:. c:.;:I .':f .:-j:j :: ... I: '.., .... '.? ...... MINERAL JOE NO. 1 MINE CHANNEL SAMPLE ... .- . _...... - ...... --SAMPLING :- .. After a reconiiaissaiice of n number 'of mines an ore occurrence at the Mineral Joe No. 1 mine, Jo Dandy group, Montrose County, Colo., mas selected for de- tailed work. -;"lie location of the sampling site is shown in figure 48, and a sketch of ,$he ore .occurrence, to- gether with the sampling pattern, in figure 40. The site was chosen because it appeared possible to collect a continuous channel snmple- from unmineralized snnd- 16s GEOCHEMISTRY ASD JIISERALOGT, COLORADO PLATE.iG GRAXICY ORES representing differences in oxidation state. It was not At the sampling site in the Mineral Joe No. 1 mine a possible to get a continuous set of samples that crossed mineralized zone cuts across the flat-lying sandstone at from unmineralized rock on one side of the mineralized a steep angle. The sandstone is overlain by a greenish zone to unmineralized rock on tlie other side. but field shale bed which is irregularly mineralized. Figure 49 observation suggested that one end of the channel shows the geileral appearance of the ore in relation to sample was in unmineralized rock, and the other end the channel taken. The followingis a description of ..... of the channel was in weakly mineralized ground prob- the spechens along the channel : ...... - ...... ably low in vanadium and uranium, but that all of the ...... ' -.... Bpecimen ... Dwcriptfon more highly mineralized zone was included in the chan- ...... i A,-,------l-White -&&.tone;'fairly well cemented; un&- nel. It was hoped that detailed study of the min- ...... :...... eralized. ' ...... I,. eralogy, oxidation state, and distribution of major and ... B _____::-I;-_,;:-~-.-Xeakly cemented sandstone; tan with brownish . i .... minor elements all in relation to the host rock, would ..- ..... : .. :<:;.-speckles;'unminer3lized. .. provide more concrete data with which to consider the .: C ____- ______Same as B, but with thin c '1 rr;. .I base of specimen. ;+;: I i.' . geochemical history of the ore. Before collecting the b... r-
gpsum. Calcite is present only as very rare grains and Carnotite becomes abundant in specimen IC. It is not at all as matrix. Patches and seams of coalified quire erratically distributed, solile parts of the rock mood can be seen in some sections. Evidence of es- being essentially unmineralized and showing strong de- :remely weak mineralization is in flakes of "vanadium velopment of quartz overgroKths and others shoKing clay" mliich can be seen wrapping around quartz grains ; marked corrosion of the quartz grains accom- this material has a variable reddish brown color, mean panied by carnotite. The carnotite commonly hugs the index of refraction near 1.61, and high birefrigence quartz grains, and appears to replace the clay irregu- typical of the clays in the mineralized portion of the larly; it also spreads into areas of sandstone where channel. Evidence of weak mineralization is also shown clays are absent. It forms small haloes around many by the faint yellowish stain which developed on the sur- of the isolated grains of coaly material present. The face of the samples after they were originally collected irregularly mineralized patches are in places bounded and air dried. A few tiny patches of carnotite are pres- by a thin band of a very hegrained opaque mineral, ent on someof thespecimens. .,?.!- ;-;:.. ' ' . . . which seems to be largely replaced by carnotite; the Evidence of mineralization begins abruptly in the mineral is unknown. Gypsum, abundant in the unmin- channel in specimen F. Part of this sample is typical eralized areas, continues as an important interstitial of the unmineralized rock, made up largely of detrital component in the strongly mineralized patches. Hem- quartz and interstitial gypsum, with a very minor ettito and metnliewettite form a few thin seams in amount of reddish brown clay forming coatings around narrow fractures across the rock; they appear to be some of the quartz grains. . Verjabruptly, along a line definitely later than all of the other minerals. nearly at right angles to the general bedding, reddish- Specimen L is basically similar, but has carnotite brown vanadium clay becomes abundant as an inter- more uniformly distributed through the matris. . stitial component. In one thin section cut across this Corvusite and small amounts of pyrite, marc'asite, and boundary, the gradational zone between essentially un- paramontroseite appear in specimen M. The corvusite mineralized rock and that more or less typically min- is in irregular patches, in places completely filling the eralized rock is only 0.2 to 0.3 mm across. The vsha- matrix between the quartz grains. Elsewhere it irreg- dim clay forms rims on many of the quartz grains and ularly replaces vanadium clay minerals and penetrates has clearly replaced and encroached on the interstitial along gypsum cleavages as long hgers. Carnotite is avsum, and to a much lesser extent corrodes the quartz abundant in areas bordering cormsite, and in one place grains. The clay is erratically distributed, being absent a microscopic veinlet of carnotite cuts corvusite. Hew- in parts of some slides, forming thin films around quartz ettite and metahewettite are rare as l3lings in late hc- grains, or occupying the entire interstitial volume be- tures, in one place bordering a late gypsum veinlet. Py- tween--.hedetrital grain+ Isolated ragged plates of the -rite and marcasite grains, mostly small and anhedral clay are commonly-scattered through the gypsum.--The -but -including a few larger euhedral crystals, are lo- sedimentary clay aggregates are only slightly replaced cally rather abundant and are limited to areas where by shreds of the vanadium clay. Limonitic aggregates corvusite is absent. A few of the pyrite grains are cor- (presumably goethite) are considerably more abundant roded remnants of larger grains, and are surrounded by in the clay-mineralized portions ;they are highly irrey- goethite ( P), but most show no evidence of corrosion. Iar+routline-m& -itcqn+~~ypess-thsttlleprty-The p-pite andmarkite clearly were introduced at the - derivedfromosidationofpyrite. ..; ;..-:..-::.:: . I...... time of mineralization. Paramontroseite is very spm- 'This generally typifies the -channel simple betwein ingly present as prisms radiating from quartz grains specimens F-and J;--Carnotite-first is-seen as more tliait -and ns minute rosettes; it is present in areas near traces in specimen H. It is erratically distributed as pyrite and away from cormsite. smnll patches or very fine grained aggregates appar- Specimen N comprises the black heavily mineralized ently replacing the clays and gypsum. "eye" of the ore zone. Parts of the sample contain An unidentified mineral, perhaps a vanadate, is com- abundant corvusite, similar to specimen M. Most of mon, but not abundant, in most of the mineralized sec- the sample has abundant euhedml pyrite and marcasite tion of the channel; it is in tiny lath-shaped grains, crystals, mostly in the interstitial space between quartz light yellowish brown across the length and dark brown grains, and commonly replacing parts of quartz pins. to nearly opaque parallel to the length; it has a rela- The two sulfides occur side by side, with pyrite some- tively high index of refraction .and a strong bire- what in excess of marcasite. Where they occur near fringence. -.Itappears to replace both interstitial gyp- corvusite the crystals show evidence of corrosion and sum and the vanadium clays. 'We have so far been limonitic material is present. Associated with the py- unable to isolate tho mineral for further study. rite and marcasite is abundant paramontroseite; it 170 GEOCHEJIISTRT ASD MIXERALOGT, COLORADO PLITE-IU CR-WIUM ORES forms prisms and mnsaire areas betveen the quartz origin are present arid commonly accompany micro- grains, growing into both clay and gypsum; pnramont- scopic seams of coalified organic material. The quart.z roseite too is absent near corvusite areas. Carnotite grains shorn little corrosion. is abundant where pyrite and paramontroseite are ab- d smnll amount of organic matter (coalified wood) sent. No uraninite or cofinite have been found. Car- is present in nearly all of the specimens. JIost of it notite does not seem sufficiently abundant to account forms microscopic rounded or worm-shaped grains ; for the amount of uranium in the sample, and it seems under crossed nicols in polished section the material likely that uranium is distributed colloidally in the ranges from isotropic to that showing a grating struc- matrix material containing the pyrite and paramont- ture similar to microcline ; no cellular woody structures roseite. It seems likely, also, by comparison with oc- were seen. Only h specimens P and Q are continuous currences in other mines, that uraninite was originally seams of coaly material common; these were not studied
.. f ...... present. '.'-. '. . . . ,.:.: :...... '...I . . . polished section: :~~'?ci!.+!::: ;' .. in . .. . Specimen 0 is heavily mineralized with corvusite and The clay fractions from specimens JI and P have carnotite, and in this way is similar to specimen M on been studied by John C. Hathaway and are considered the opposite side of the "eye" of the channel. .In irreg-' in detail in Part 1l.l1 These clays appear to hrebeen uhr areas, corvusite forms nearly all of the matris be- introduced during mineralization. Briefly, the clays tween the quartz grains, and the quartz grains are in each sample are chiefly mised layered mica-mont- rounded and corroded. Elsewhere the corvusite clearly morillonite and chlorite-montmorillonite, and are simi- lar to vanadium clays other deposits. : . -. -replacesparts of the gypsum and vanadium clay matrix.. in .. . Some 'areas show only minor mineralization and strong Summary of the minerd sequence. euhedral overgrowths of quartz so that little interstitial to mineralization was a fairly clean quartz sand with volume remains. A small amount of pyrite, in what relatirely little clay7-a very small amount of coaly appears to be remnants of larger grains, and very small material, and was cemented with gypsum; specimens marcasite grains, are present in the protected quartz P and Q contained more abundant clay and organic only material. . Prior do mineralization, euhedral .over-- areas, and rarely are near cormsite. Carnotite - and metatyuyamunite (the latter predominating) are growths developed on a portion of the quare -ips. abundant and widespread; they replace corvkite, and Mineralization commenced with the introduction of commonly form a band between the corvusite areas and vanadiferous clays, which replaced gTpsum and in part quartz. Perhaps simultaneous with the clay, but prob- the less mineralized areas. ..-.. ': . . Carnotite, metatyuyamunite, .and vanadium clay are ably later, was the deposition of pyrite, marcasite, and abundant in specimen P. Mineralized clay is abundant, montroseite; the relatire ages of these latter three min- .- . -. - . - - -. __._.- ._ - __ . ___ __-erals-am--not clearj-but they appear to be nearly con- ...... - replacing gypsum. In addition, prunary clay is com- - . .- . .- . .. - . &mporaneouiThe montroseite since oxidized --L..mon as pellets and less so as thin cliy seams-and XriiigY : has pseudomorphously --paramontroseite (Evans and ers; this clay has a much lower index of refraction and .,to Mrose, 1955). The clay minerals were widespread in low absorption as compared to the vanadium clay, and is of sedimentary origin. The carnotitelike minerals the channel sample, but the others were largely limited totheareasinth --- are-spottily distributed, and are abundant in large , ...... -___.__ ._. . - __ - - --ne1 sample. .- . patches; they appear to replace chiefly the clay min-.. The corvusitelike minerals are distinctly later; they .. erals. The-quartz grains are largely embayed and cor- replace clays, gypsum. and the. other matrix minerals . .. roded. :%oalified organic remains are abundant -and .and apparently were simultaneous 6th or later than form .thin 'streaks that emphasize the bedding. "me - the oxidation of pyrite and marcasite. Widespread de- mineralization does not seem to have been influenced in velopment of carnotite and mehtyuyamunite followed detail by the organic material. unidentified reddish An comite. Eren later was the formation of hewettite brown mineral, perhaps goethite, appears as irregular and metahewettite, ggpsum, in open cracks. streaks and bands associated with strong carnotite min- with .- -. . . -,~ . .. enlization...... CHENXSTBY .OF !l!HE CHANNEL SA.MPLE . -. Evidence of mineralization is weak in specimen Q. . Preparation of sam&s.-The specimens were hand Carnotite is limited to a few ,mall specks seen in hand crushed to -40 mesh, with special care taken to avoid specimen. Gypsum comprises most of the matrix mate- loss of material and contamination. Ab rial. Vanadium clays fontthin films around many of the quartz grains, and in patches fill the interstices. Fairly large sedimentary clay'pellets are -present but ~QpeclmensIf and P are eocled by Hutl1:twny ILB P-1-U-53 and not abundant. BIicroscopic clay seams of sedimentary P-l-P-XX rwpectlrely. due to disc:rrded material contaminated during the ant1 SO,; tlie results are sliown in table 1 and plotted labeling of tlie samples. For most of tlie clieiiiicnl in figure 50. In figure 50, inste:d of showing values as n-orli 1/-gram samples mere prepared by careful hand percent by wight of each element in tlie specimen they splitting. Duplicate samples checked well during vari- are sliown as millimoles of each eleinent per 100 grams ous determinations, indicating that the sampling pro- (except U, which is slion-n as millimoles per 1,000 cedure and sample size tlppareiitly were satisfactory. grams). Tlius, each plotted value is proportional to Nujor constituents.-.A sample of each specimen in the number of atoms of each element present, rather the channel was analyzed for Ca, AI, Fe, V, U, total S, than to the weight of each element. -- - .- . TABLE1.-Chemical analyses of specimens of fhe Mineral Joe mine channe sample .. , ..I
eU 2 1 Add 1 In- I Tot?I a , I Add 4 1 Acid 4 In- 1 Total a Total4 Add+In- &&ate4 Cad AI’ soluble U soluble Fe soluble Fe V 8 1 soluble 9 1 --.8 I . an 3.50 -L37 22 - -4.16 4.97 Ll coo 4.2 1.9 3.90 4.37 22 3. M 3.83 4.55 1.2 .m7 .oooo5 .81 262 257 ’ 3.27 4.3 .aBJ .0010 .e4 246 2 21 2 91 LQ .23 .0014 .BB LU L38 a55 28 .63 .m .03 L63 LSO - 200 4.1 e.34 ‘ i.oop .91 2xl 243 3.27 27 LO i‘.ooQJ .b6 238 230 288 4.1 .m .am 1. 18 1.41 L38 L97 4.7 1.3 . .o050 LW L63 L95 269 LO 1.0 .0112 4.40 a31 223 236 20 1.6 .0113 .68 1.84 L68 236 3.3 1.2 .w2 .83 LP LOQ L65 a9 2 47 243 3 17 ai
* Wyxt: Carmen Johnson, U. 9. Oeoloslc31 Sumy. bold Wluble U deter- 4 Analpit. L. B. Jenklru. U. 9. oeOlo@cd Survey. Add-coluhle and 3cId.lawluble mlfled after hChlng srrrnole 24 hours In cold 1 N HtSOc. dues deterrmaed after lahlng sample 5 rtsp In hot 33H percent BYSOL 1 Analya: B. A. McCd, 0.9. Oeologicsl Survey. 1 AmIpt: C. 8. Annell. V. 8. Oeologlcal Survey. Qu3ntltiulve spectogmphlc I hnalyst: W. B. Tucker, 0.8. Oeologleal Survey. I determinatl0ns. -- - .? -__ - I. - The data cleirly reflect the mineralogy- The plots in small part form- limonitic material and in larger for Ca and S coincide, within the limit of determina- part is combined in the clays; in specimen N, and to a tive error, except in samples Bf and N, and represent much lesser extent to 31, it is abundant as pyrite and gypsum; in specimen N the excess sulfur is present as marcasite. pyrite and marcasite and is accompanied by an ap- Organic carbon, a memre of the coalified mood -propriite-increase in total-FeXlie-values for SO,; as --present, is plotted for some of the specimens in weight distinct from total S, mere not plotted because they so percent in figure 51; total uranium and vanadium are nearly coincide with Ca throughout. The unusually also shown for comparison: Uranium and vanadium high Ca and S values for specimen H reflect an 8 mm are highest in and near the organic-rich part of the thick gypsum seam in the specimen; this depresses the channel. -values of most of the other elementsfor that specimen. The-analytical data reflect the sharp boundaries of Tlie AI vdtie is~~r~po~~t~a~-re~f-tfie~‘claS”--ainernlizatiolr;-~early U, -V, Fe, and 81 have been minerals present; it is roughly complementary to the . introduced, and Ca and S (as SO,) have been removed. Ca values, representing gypsum. Tlie unusually high Uranium and epivalent-uram’um relations.-The - AI content in specimens P and Q reflects ab-undant -analytical results for U and equivalent U are plotted sedimentary clay. in figure 52. Inspection shows differences only of the Clay and gypsum comprise the bulk of the material order of magnitude of the espected determinative error. interstitial to the detrital grains except in specimens The ore is essentially in radioactive equilibrium, and it M, N, and 0, where pyrite, marcasite, and vanadium can be concluded that there has been no appreciable mi- osides bulk large. Uranium (which is exaggerated by gration of tlie uranium for many thousands of years; a factor of 10 in figure 50) is everywhere far subordi- in all probability none during Quaternary weathering. nate to V, with which it combines in n 1: 1 ratio to form (See Stieff and Stern, Part 13, p. 152.) Tlie only espla- carnotite or metatyuyamunite or both. The excess of nation of the observed relations, if recent migration V above that comlhned with uranium in carnotite large- had taken place, would be that the transporthgmedium ly follows the AI in the clay minerals, but in samples had exactly the same solvent capacity both for uranium M, N, and 0 it occurs also as separate vanadium oxide - and for its daughter products-a most unlikely coinci- minerals (corvnsito and paramontroseite) . The iron dcncc. 173 GEOCIIEJlISTRY -LYD MISEE;\LOCT, COLOR-%DO PLATE-LC' UR;'LSIUU ORES
SPECIMEN
. ._ ...... INCHES FROM LEFT (NORTHWEST) EDGE OF CHANNEL SAMPLE ...... ---...... Fioom 50.4raph showing dlstributlon of reveral elements acrosr the~IUlnera1Joe No:l mlne channel sample. Values . *. : ... .:... _. ...ln mlllImoles per 100 grnms of sample. except aranlum whlch Is la m!.Ulmolee per 1,OOO pamr of afmwle. Data derived ..: ...... _. i...... __:from table 1. . __ ., ..,.=...... ~. I ...... - ...... c .... DETAILED CI-IEJIIC.LL ASD MINER4LOGIC.IL RELATIOSS IS TWO V-LXJADIL?\L-CL1SITl OPJZS 1’73
I I I I I I I EXPLANATION I I 0 Carbon ? Carbon not determined I 5.0 - -x Uranium .... - *AVanadium I
I I 4.0 2 n U I Z I >U A a -1. - 3.0 E I rI- .c3- I W -L 20 2 + Z W U U W n 1.0
. .- - . -- ...... __ ...... EN -- ...... - ... ______~ ...... - . . - . - .._ ...... - -XPECIM, _____._ ___ ..__-.____ ...... Fmnaa (Il.-DLtrlbntion o! uranium, ranadlnm, aad or@c carbon In rpedmena acrom the Weral Joe No. 1 mlne-channel.
---Tr&e-eZement reZutions.-Semiqu~ti~titatirespectro- --thebarren sandstone of the Salt Wash member of the graphic analyses of the specimens were obtained, and Morrison formation except for small uranium and vana- tlie results are plotted in figure 53. These data, plus tlle dium anomalies (see Part 3, p. 32). Furthermore, the data in table 1, show definite strong anomnlies anomalies are all positive; there is no indication of re- for uranium, lead, vanadium, and iron; probable moval of any minor element during the mineralization anomalies for barium, strontium, aluminum, and molyb- process. .. denum; and a doubtful anomaly for copper. The defi- The channel sample selected is a representative one nite and probable anomalies, with the exception of that in its minor element content; the unmineralized sand- for barium, appear initially in specimen F and are stone is uniform, and typical of barren sandstone of maintained across the profile; that for barium occurs the Salt Wash member; the mineralized zone contains initially in specimen G. The first five specimens, cld- additions of the elements that are enriched in “average fied as “unminernlized” in the field, are remarkably uni- ore,” as determined from many ore pulps (sea Part 3, form in trace-element content, and they appronch closely p. 32). The most remarkable features of the minemli- 174 GICOCNEIIIS'I'RT .LYD NISEItiLOGT, COLOR.iD0 PLATEAU URXXIUJI ORES
G
. -2 . _.
...... __ .. I ...... - /. .. - .. ._ __.. -- --
-3 -2 -I 0 +I
..... - ...... - ...... -...... -EQUIVALENT URANIUM .. - . - XOG ... -.. .- . FIouaa 52.-Plot of log U against log eqnlvalent U of specimens from the Aflneral Joe No. 1 mlne channel &le. .. -. - ...... -zation-'hre :-(1) the 'abrupt-'cut-off of . %ll-introduced -- iron, mniuxi~,vanadium, and sulfur are present in any elements at a zone no more tlinn a fen- inches wide, and sample in mounts exceeding 0.05 percent. Sulfur is perhaps only a few tenths of an inch wide if the min- present as &de and as sulfate; these can be readily eralized clay is an iiidicat.or; and (2) t,he lack of any separated by their dative solubilities, and arc reported negative trace element anomalies in the mineralized separately in table 1. Gypsum, and probably n minor zone, suggesting tlint no minor constituents have been amount of barite, represent the sulfate; pyrite and removed during or after mineralization. marcasite, tlie sulfide. Uhnium can be present both as U(IV) 3nd as A-.i. STATES OF OXIDATION..OF THE SPECIXEXS U(VI). Of the U(IV) minerals, uraninite is essen- -.-. ----?.Itis desirable to know the proportion of each ele- tially insoluable in cold lN HSO,, but C0ffinit-e is appre- ment present in each of its oxidation (valence) states. ciably -soluble. In the .channel sample speche* - Of the elements likely to be present in unknown vdenco practically all of the uranim' is readily soluble (see states, spectrographic and chemical data show that only table 1). Neither cofinite nor uraninite could be DETAILED CHEBIIC.IL .LSD MISER~\LOGICAL1
Ca 5-10 1 Mn 0.01-0.05 1-5 0.005-0.01 B D FG H ' J L MNO PQ
Ba 0.05-0.1
-_ 0.01-0.0 ~ .- - .,
i : .- 'Z ! -. . . , .: .:...:..-...... - . I .. .: . ...,.:: ..,...... -.-..-...... _- . .- K 0.1-0.5 Cr 0.001610051. _.- .. - . : . ' . ' I 0.05-0.1 0.0005-0.00
... -ACEGIKMOQ ACEGIKMOQ
Mg 0.54 7 - -I ...... 0.0005-o.ooi . 0.1-0.5 . >.... -...... ~.:..AC I -K 0 ..... _-I..&. .-.IS.._ .. A C E G . l--K M 0 Q ...... E G M 0 . - ...... -...... __ ...... I ...... 1. ... ; .~ 0.1-0.5 .. : ,...... ' Na ..'0.05.0.1 0.01-0.0
.. 0.01 4.05 Mo o.oo~.oi ---...... -...... - - -. 0.001-9.00 ...... - .... - ... .. - .-.-.-e -L--L=;.:...... -r-:..i --A C E G I K M 0 Q : --T-:I --::-' , A C E 0 1 K M ,O Q
-IOWB& 53.-Semlquantltntlve spectrographic analysee of speclmeM from the Mlnernl Joe mlne channel sample. _--__--_____IBongerr are in percent. - Eorizontal lettern delagnate specimens Analyst. C A. Annell.
found mineralogically, and the abundance of oxidized parts of the channel sample. If such an assemblage mineral species in all samples suggests (by analogy of redox-active l2 elements is taken into solution in air- with other deposits) that any U(1V) minerals would free sulfuric acid (where no over-all oxidation or re- not have persisted. It is therefore assumed that the duction will take place), the vanadium and iron ions uranium is present entirely as U(VI). formed will promptly reach an equilibrium state in The valence states in which vanadium and iron are which the valences of the ions are a function of both present cannot be directly determined, and yet these the pH of the solution and the cumulative interactions largely control the variable oxidation state of the ore. of all the redox-active elements present. Thus, the From the mineralogy, it is known that vanadium is valences of the metals_- in solution need not be the same present 119 V(1V) and V(V), and that the iron is =Bedox-actlve elements are those that change thelr valence atate present as both Fe (11) and Fe (111), at least in some with naturnl chnnps In mluclng or oxicllzlng envlroninent. 176 GEOCIIEMISTRY ASD MISEKILOGT, COLORADO PLdTEAU UR.\SIUM ORES as they were in the minerals dissolved. However, the In the unniineralized portion of the channel (speci- reducing capacity of the solution should be the same. mens A through E), the reducing capacity is low but The reducing capacity of a sample refers to the ranges between about '/3 and :$ of the sum of ranadium amount of oxidant the sample can reduce, and can be plus iron: this is the amount of mnadium or iron: or expressed in milliequidents per 100-gram sampie. both. which is in a reduced state-that is, V(1V) or The reducing capacity expressed in this unit is given Fe(I1) ; the remainder must be V(V) or Fe(1II) or by the number of ml of a 1 N solution of oxidant both. It has been shown mineralogically that small (ICJhO, in this case) reduced by a 100-gram sample. amounts of carnotite (or tyuyamunite) and ferric hy- For direct comparison, it is convenient to state compo- droxides are present, accounting for part of the V(V) sition of the sample in milliequivalents per 100 grams. and the Fe( In). The reduced vanadium and iron If the equivalent weight of the oxidant is defined as the must be present in the clays. amount necessary to oxidize one mole of any ion by The reducing capacity rises abruptly at the boundary removal of a single electron, one milliequivalent of an of mineralization (specimen F) and continues at element is equal to one millimole of that element. roughly the same level through specimen L. Basing To determine the reducing capacity of each part of interpretation on the mineralogy, the bulk of the re- the channel sample, about 100 mg of each was digested ducing capacity is due to the vanadium (IV) and the for five days in hot 33.3 percent H,SO, in a carbon ferrous iron contained in the clay minerals; this con- dioxide atmosphere. Quantitative tests showed that forms to the chemical study of vanadium clays by essentially all of the redox-active elements, except iron Foster, reported in Part 10 of this volume. The clays in the sulfides, were taken into solution. The solution may also contain a small amount of vanadium (V) and mas then titrated with 1 N RJLnO,. Tho reducing considerable iron (ID). The iron staining observable txpxcity of each specimen, together with the concen- in the samples may account for some iron (III). It tration of vanadium and iron in solution, expressed in seems likely that more vanadium (V) is present than milliequiralents as defined above, are given in table 2. can be accounted for by the carnotite and hewettite re- Pyrite and marcasite are insoluble under the treat- ported mineralogically; probably other vanadates not ment noted above. Therefore, the sulfur present as identified under the microscope are dispersed through sulfide and the iron combined with the sulfide are not the finepained matrix. reflected in the value of the reducing capacity obtained. The reducing capacity of specimen If, which con- Sulfides were present in chemically si,pificant amounts tains a small amount of lower-valence oxides, appears only in sample N. to result largely from the vanadium (IV) and iron The coaly material contained in the specimens may (E) in the clays and to a much smaller degree to the have reduced sorne-af the redox-active elements during -paramontroseite and cornsite. The increase in acid digestion (see Part 14, p. 162)-; we have no measure of soluble iron probably rdects the oxidation products the amount of such reduction, but we feel it was not of pyrite and marcasite. The large amount of vana- great enough to distort the conclusions appreciably. dium (V) is present chiefly in hewettite, metahemettite, carnotite, and perhaps other unidentified vanadate TABLE2.-Reducing capacities and vanadium and iron con&& of minerals, as well as comite. - - -acid extracts1 qf specimens from the Mineral Joe No. I mine channel sample. - --€n specimen N, the black "eye" of the channel sample, [All valua are tn mlllloqulvalentsper 100 grnms of gamplel the reducing capacity is very high and approaches the sum of the vanadium plus iron in milliequivalents, so ...... -- -that most of both the iron and vanadium must be present in reduced minerds as V(IV) and Fe(II). This conforms with the mineralogy, in that vanadium 22 3.0 20 23 clays and paramontroseite are the dominant vanadium 1. s L4 20 1.4 minerals, with smahamounts of cornsite. The fully ... 20 21 . n.4 13.0 oxidized elements present in minor amounts, make up n.7 11.4 7. I carnotite, perhaps unidentified vanadates, and corn- IS. 17. , site; iron (III) is present in oxidation products of py- 9. 1 19. 1 rite and marcasite. __ .. 61.0 27.7 ' 81.4 43.8 Specimen 0 is nearly as heavily mineralized as speci- . _... 04.0 , , 121 -r ' " "M.3 13.0 men N, but has only half the latter's reducing capacity. :-: ::i . . 0.3 Here pnmmontroseits is lacking, but considerable va- nadium (IV) is present in the corvusits as well as in tlie clays. Carnotite, corvusito, and perhaps unidenti- I
DET,lILE D CIiEJIIC.1L XX D JICSERLLOGIC.lL REL-ITIOSS IS TWO VAN AD I UJI-UR.Ih-I~Jf ORES 177 fied ranadates account for the abundant vanadium (V). 3. Except in the dark “eye” of the channel sample A small amount of iron (111) may be present as a re- (specimen N and parts of 31 and 0), the vanadium sult of alteration of pyrite and marcasite; the remain- clays are associated with vanadates, uranyl ing iron: mostly as iron (11) , is in the clays. vanadates, and traces of ferric oxides, and repre- Specimen P is comparable to specimens on the op- sent an assemblage largely in equilibrium under posite side of the bIack “eye” of the channel sample. osidizing conditions. The reducing capacity appears to result wholly from 4. In the dark central “eye” of the channel sample the abundant vanadium clays present. Some iron (111) (specimen N and parts of M and 0) the vanadium may be present as goethite; vanadium (V) is present clays are associated in part with vanadates, uranyl in uranyl vanadates, and probably in other unidentified vanadates, and traces of ferric oxides; and in addi- vanada tes. -...... tion, grading inward to the center of the dark The reducing capacity of specimen Q nearly ‘equals “eye,” with vanadyl vanadates, and ultimately with the sum of iron plus vanadium (in milliequivalents. iron sulfides and a vanadium (IV) oxide (para- per 100 g), so that most of these metals must be present . - montroseite). This gradational zone represents a as vinadium (IV) and iron (11); they are doubtless mineral assemblage out of equilibrium; part of the contained in the clay structures. Judging from the assemblage is in equilibrium under oxidizing con- petrographic study of this sample, these elements were ditions, and part is in equilibrium under mildly likely introduced into existing sedimentary clays. reducing conditions. To summarize, the entire reducing capacity, except 5. The relatively high percentage of vanadium and in the very highly mineralized “eye” of the channel uranium in the dark core of the channel coincides sample, can be accointed for by the vanadium (IV) with the relatively high organic content of the and iron (11) held structurally in ‘the clay minerals. - rock in that part of the channel. The presence of The remaining iron taken into solution as Fe(III), can iron sultides and of vanadium (N) oxides also accounted for by the clays in part and the rest by be _,.. - . coincides with this high organic content. hydrated ferric oxides. The remaining vanadium, as V(V), is present in the form of vanadates, some of VIRGLY NO. 3. MINE CHANNEL SAMPLE them probably unidentified mineralogically. Only in ... - . .. . LOCATION AND GEOLOGY . . . .- specimen N, and’to a much smaller extent in the ad- jacent specimens M and 0, does the reducini capacity The vir@’No- mine is in the Long Park area,’ result from the presence of vanadium oxides containing MOntrose COUtYj COlO. used for vanadium (IV) (chiefly paramontroseite). In these this study was collected T- w*Stern* The site same samples, the-low-valenceiron sulfides (pyrite and of the sampling and a sketch Of the Ore Occurrence is marcasite) hiso .fireieit;but -the@-$reynsolub;le-~a-;; shorn figure The Sample .Was removed Bs One do not affect the measured reducing capacity.- -There -- large piece as shorn by the shaded area in the sketch. . is no evidence, eitller from the reducing capacities or NO precautions were taken to prevent air- osidatiop from the mineralogy, tlint vanadium (III) or uranium after wm~ling. (IV) are present in any part of the channel sample. The locality sampled in the Virgin No. 3 mine is .. . .. -- - - .- . . . ___ --approximately 300 feet below the surface. The .min- BALIENT FEATUBES OF THE ~BALJOE NO. 1 eralized zone &CUI% in the Salt wash member’of the’-- ... .- CHANNEL SAXPLE : ... .?.:::::::’. 3IomiSn formation. The mine generally &OWS little
1.: One boundary between .mineralized.and .unmineral- megrrscopic .evidence of oxidation and the VOSSap- bed rock is nearly pencil-shirp,-anil Cuts acrog --enrance of the mineralized sandstone at the sampling-- the bedding at right-angles. The boundarg bears site suggests no alteration of the primary features. It no relation to sedimentary or other structures, or can be mimed that the position of the mineralized to changes in lithology. The unmineralized rock lens is essentially the same as it was just after min- contains appreciably more uranium and vanadium eralization and that the sample is fairly representa- than typical unmineralized sandstone of the Salt tive of rich primary ore in the Salt Wash member in mash member. that area. 2. Vanadium-bearing clay minerals are nbundant throughout the mineralized part of the channel PREPARATION OF THE SAIKPLE ..
*a‘ sample. ‘A large part of the vanadium in the clays The general shape and appearance of the channel ;!has a valence of 4. The vanadium clays are mostly sample is shown in plate 3. The sample was cut in . *: newly constituted minerals, and are not simply half vertically as marked and divided into ten parts “vanadated” sedimentary clays. based on the lithologic variations. The ten segments 17s
...... _, . . 1 Foot . ... '0 ' 50 Feet '. '. 0 . -I FIGUREM.-Skctch - of the workiogs of the Vlrgin No. 3 doe showlog location of sampling sit+ and nketch of sampling slte sllowlog relatlon of channel sample to ore nod sedimeotnry features. channel sample Is the shaded area...... , - . ....- - ...... -,- .. -.-...... on the left side of the channel sample were mound to exhibits markedcolor changes from &eddy mineralized pass through an 80-mesh sieve. These pulrerized9 por- rock into strongly minedized rock. The weakly min- tions were used for chemical and spectropaphic analy-. eralized portion is dark gray with a banding derived sis. A second slab, 1 inch thick,, w& cut from the from minor mineralization by vanadium clay minerals. right-hand portion of the channel sample and also The strongly mineralized zone is dark peen to black IT -divided into-10 .parts equivalent to-the left-hand por- and containsmaxv irregular patches of light-gray re- - __ tion:; These .parts in turn were. cut'in half and a .thin . -:crystallized quartz ;small black carbonaceous fragments -. . section and polished section were made of each -along. -.arerandom11 distributed throuihout tile-zone. . the mutually cut planes. The sections were ground and polished without using water to retain any water- WEAKLY MIh~ALIZEDROCK -. soluble miner& that might be present. The specimen Tho weakly mineralized rock contains no recognizable ---numkershenceforth.. refer to those shoi-n-inplate 3.-~--uranium-orL vanadium minerals, although minor ...... - ...... 1...... _.. ..amounts of vanadium are present within the clay min- XINEILALOGY OF THE'CHANNEL -LE . .- .. erals shown in plate 3. -*Thedetrital quartz is poorly -The discussion of tlie mineralogy is divided into two sorted and suthigenic orerpwths produce a manic parts : weakly mineralized and strongly mineralized testure. Clastic feldspar, both microcline and plagio- rock. This division is based on tlie chemical and min- clase, is present but never in excess of 2 percent. Clastic eralogical results. A point-count analpis was made on mudstone partings that roughly parallel the bedding each thin section to determine the relative abundance are common in specimens 2 and 3. These partings have of the constituent minerals, and the results were plotted been contorted by compaction, and along the upper and ih figure 55. A sharp cliange is noted between speci- lower surfaces strong pressure solution of the quartz mens 3 and 4 and a lesser one st specimen 10 ;specimens is apparent from the corroded grains and development 1,2,3, and 10 are here considered ns weakly mineralized of microstylolites. The mudstone partings retain their rock and specimens 4 through 9 8s strongly mineralized original particle orientation and contain mostly mixed rock. .The strongly mineralized zone is highly irregu- layer mica-montmorillonite, sericite, and quartz with lar and minoralogical continuity is lacking because of minor pyrite and mnrcnsite showing hmboidnl tex- discontinuous horizontal zones. The channel snmple tures. Wisps of carbonaceous f ra,ments are commonly
DETAILED CHEMICAL -1K D MISE RIL0 GICA L RE L.LTI 0 S S IS TWO V AS,lD I UX-GRAN ILX ORES 179
...... -...... : ~, ..~.._- .- ...... , . I. .-...... ------... --SPECIMEN NUMBERS -..~..~...... -. .- .... -~..-...... -...... FIouw 58.-Mlnernloglcal composltion, based on polnt-count .andpsls, of irpecfmens from the Vlrgln So. 3 mine chnnnel sample. Specimen Nos. are dlatrlbuted along the horlrontal base In proportlon to the thickness of each segment In the chnnnel sample.
present in the clastic mudstone partinp The inter- tourmaline, zircon, and apatite in decreasing order of - granular of the sandstone-contain mixed layer .. abund3nce . - ...... - ... -- -areas .. - .. __ .. mica-montmorillonite, chlorite, and kaolinite accom- .. =... . - f -:f.:BmONQLY MLXEl3ALIZED EOCX '-.:- .... panied by calcite and minor barite. Clear calcite forms anliedral patches replacing the quartz and it appears to - The boundary of strong mineralization is reflected by truncate the quartz overgrowth boundaries. Honey- an abrupt change inj$-oss mineralogy'of the rock. The yellow barite with weak pleochroism also forms an- upper boundary is marked visually by a dark-greenish hedrlrl patches which usually shorn a prominent inclu- coloration which cuts across the bedding planes and in sion band near the outer boundary. In specimen 10, the lower boundary there is a narrow transition zone euhedral pyrite forms inclusion bands in the barite. from black to gray. Within the mineralized zone the Possible evidence of weak oxidation of the sulfides is coloration is variegated and roughly follows the trend obser'ved in the polished sections along with limonitic of the bedding. Quartz, clay minerals, vanadium ox- stains around the outer boundaries of the clastic mud- ides, and carbonaceous material comprise the bulk of stone partings. - Several anhedral grains of galena- the rock. The relative abundance of these is shown in clausthalite were identified in specimen 3. The X-ray :figure 65; the color banding is due only to different .. .-- patterns of this mineral suggest that there is more proportions of minerals. ... selenium present 'than sulfur. Heavy mineral separa- - The quartz no longer mhintains its .detrital outline tions of the weakly mineralized rock samples contain within tho mineralized zone and is strongly corroded 180 GEOCHEMISTRY ASD MISER*ILOGT, COLOltADO PLITEAU UR-LYIUII ORES into cuspate forms. The corrosion appears to liave been and not be ictentified. No other vm:duin-bearing greatest normal to the bedding and the cuspate quartz minerals mere found in tlie channel sample. grains show elongation in tlie directions of the bedding Carbonaceous material is common Kithin the min- planes. MicrostyIolites are commonly developed where eralized zone and forms e1ong:ite stringers character- the quartz grains are in justaposition. Isolated elon- ized by a pitchy luster and subconchoidal fracture. gate patches of quartz grains within the mineralized Two distinct types of carbonaceous material can be zone, particularly in specimen 5, have not been corroded distinguished in thin and polished sections : (1) frsg- but rather shorn strong secondary overgrowths on the ments showing well preserved cell structure of woody detrital quartz grains. Clastic feldspar grains are also material. These particles conform to, or wrap around
scarce in the mineralized zone, although the feldspar contiguous detrital quartz grains and are translucent ’:
’. appears to be much more stable than the quartz and in thin section. (2) Kidney-shaped, opaque, carbona-
.- little or no corrosion of the feldspars was noted. Most , ceous blebs that cross-cut the bedding and replace the of the feldspars are orthoclase and microcline. .detrital and recrystallized quartz overgrowths. There Associated with the corroded quartz are green to is no recognizable wood structure present within these .- brown vanadium clay minerals that ‘fill the matrix blebs, although in polished section under polarized around the quartz. It appears that the clay minerals light, strong anisotropy is observed. This anisotropy .. have replaced the quartz and may have derived their is similar to the grid-iron twinning observed in silica from the breakdown of the quartz. The vanadium microcline. .. . ::-. clay minerals form extremely fine. aggregates with . These kidney-shaped blebs appear to have formed moderate birefringence and marked pleochroism. In from the’ detrital coalified wood of the first type, al- . .- .areas rich in vanadium clays, the clays have an nggre- though as yet the relationship is not clear. Autoradio- ’ gate structure with a strong preferred orielitation .graphs show that thcse carbonaceous fra-ments contain parallel to the bedding producing a “pseudo-flow a large part of the uranium, although no distinct urn-
. structure.” ,. ’ . nium minerals have been identified within the carbona- The fine clay aggregates have a mean index of refrac- ceous material. -- tion near 1.61; it was not possible to identify the clay . Coffinite is the only uranium mineral identified from minerals optically. X-ray diffraction studies, carried the channel sample. Cohite could not be identified in out by John C. Hathaway, indicate that chlorite is the polished section and was determined only by X-ray most abundant vanadium silicate and it is assumed -analysis of a heavy residue. Co5ite was also identi- . .. from previous chemical work that the chlorite contains fied in the clag-size fraction during the study of the .. appreciable amounts of vanadium. Accompanying the clay minerals. From the autoradiograph and X-ray --:-chlorite.. is a-mixed-layered.vanadi~--~c~~monforil~--~~.analysis the cohite is probably dispersed as colloidal - 1onite.- Kaolinite -also has been‘.identified-dthough it -size particles. -Uraninite may be present also as col- appnrently does not contain vanadium. loidal size particles but neither X-ray nor polished sec- Chlorite incre‘lses from the barren rock into the min- tion studies revealed its presence. Tlie chemical studies eralized zone with concomitant decrease in the mixed &ow that. there is little or no acid insoluble uranium 4ayer-mica-montmorillonite.;-. kaolinitdoes not present .-(inW.-HS04) and since uraninite is considered in- any dehib-trend ‘&om bafiKn-tc&efiiliz&-ra: As- -soluble--(-Phair-GXLevine, 1053) it can be concluded -; indicated above, it is not possible to distinguish the clay ‘.from the chemistry that most of the crystallized unr-
.. minerals optically, although strong color variations :hium...I - is contained within the white dich is appreci-. .. -- ‘.mer0noted. -Tlie-clay matris is a reddish br&& near .ably soluble in 1N H,SO,. . .. carbonaceous fragments and a strong greenish color Calcite is common in the barren sandstone and also where associated with vanadium oxides. Tile greatest in the mineralized zone within the recrystallized quartz corrosion of the detrital quartz takes place in the lenses. No calcite was found in the mineralized zone vanadium clay rich layers, but in those isolated string- nssociated with vanadium clays and corroded detrital ers carrying qllnrtz overgromths, vmadium clay is -quartz. Honey yellow barite (bet3=1.63&.01) is hbsent. common in specimen 5 in the recrystallized quartz Paramontroseite is intimately interleaved with the lenses. The irregularity shown in the quartz content, vanadium clay minerals and forms opaque elongate figure 55, results from the fact that specimen 5 has mom
.I Iirystals in minute rosettes. The abundance of para- .,quartz overgrowths than the other specimens. ,-. . , , . montroseite roughly parallels that ‘of vanadium clay. __ . Pyrite and marcasite are irregulnrly distributed in X-ray determinations have indicated only paramont- the mineralized zone and are closely associated with the rosoite, but tho poor quality of the X-ray patterns was carbonaceous fragments. Tlie iron sulfides form ne& such that moiitroseite could be present in smaII amounts the fra,gnents and in some cases impregnate tlie wood cell cavities. The iron sulficlcs in specimen 7 form a min:itioiis at rnlues :IS high :is most of these are not marked stringer par:illel to the bedding and coincide usually considered accurate. There is no other evidence with a high concentration of uranium. Marcasite and Gf movement of elements after mineralization. pyrite are commonly intcrgon-n in framboidal clots. Semiqunntitatire spectrographic analyses of minor Euhedral cubes of pyrite are common particularly in and trace elements -cere made: and the results are shown specimen 7. Sphalerite was identified in the recrystal- in figure 56. Al, Sr, Zr, Be, Pb, and Jfg shom a s1igh.t lized quartz lenses and appears to be a late mineral; i: to marked increase from weakly mineralized rock into truncates the quartz overgrowths. Patches of a solid strongly mineralized rock. These anomalies for the solution misture of galena-claustlialite are common in most part maintain a remarkably uniform level across and around the carbonaceous.'fra,ynents and in one iso- the strongly mineralized zone. Ba shows no ordered lated spot sphalerite was seen to have replaced this lead -trend across the channel sample and appears to con-
selenium mineral. ' The scattered nature of the sulfide i centrate in the areas of strong quartz overgromths. Ca minerals precludes the establishment of a complete maintains a constant level across the channel. Negatire paragenetic sequence. -.. .- -. - . . - anomalies.. coinciding with the mineralized zone are ap- The heavy detrital minerals remain tlie same in the Parent for K7 JhcU7 and Ni. 53x1 and Cr sllow strongly mineralized zone except for apatite. The ab- no trend. The potassium anomaly in specimens 3 and sence of apatite suggests the possibilitr of leaching by 4 and the lack of alkali metals in the strongly min- the ore solutions. In polished sections, strong corrosion eralized zone suggests a selective mmnd during x~&- was observed on zircon.".'The negative 'anomalies eralization. Truly unmineralized rock was not in .. some of the minor elements (fig. 56) suggest the possi- .__arailablefor analysis-
. . . and Pb Can be bility of differential leaching of heat?. detritnl- minerals- - - . - The Positire armdies for u, v, during mineralization. - . .. construed as definite additions---Although there is evidence of extensire moGement of silica in the strongly CHE~T~%YOF THE C~ELSAMPLE .:.-:._ . mineralized zone, and we have no adequate data on A portion of each of the channel sakpiew*M . the silica balance, it is not likely that sufficient silica analyzedfor uranium, and totaliron. . The I. was removed to account for the other. ... positire anomalies by weight.-;:me----by residual enrichment. Some of the anomalies, hom- are dVen-intable 3 in __ - be due Pad to irreP1arPlacer concen- relatively sharp boundaries of mineralization types am 1 ever, in apparent. The high vanadium content of specimen 5 trations Of and not to . . .- . suggests that the percent of paramontroseite, and per- mineralization- ._ ]laps ranadium clays (fig. 551, was not representative meminor element composition of the weakly miner- , . . in .the-tlli1l.-sect.iol1 ~~~,Ji&'-A~~dant wrbnamow .-slized-portionof the channel sample is not similar to . ----.. . .-. -typical unmineralized Salt Wash sandstone (see Part material. coincides with tlie strong -pineralizstion. -. - . ... .- - .- ...... of this volume). The most striking feature of the Chemical uranium and equivalent uranium shom in. minor element distribution is the sharp boundary, table 3 appear to be close to radioactive equilibriuni, coin- ciding with the boundary of strong mineralization, although there is some suggestion of different.ia1 move- of the positire and negatire anomalies. .. - ... . --rnen~di~ugliterproducts.- .. ._ . Equivalent .- uranium.deter--...... -...... _I-- -- . .. -.. ..-..,. ... :. :.,., . .-...... STA"E-OF-OXtDATION THE -. S-LE - - - ...... _. .__- ____ - --._- 1 OF CHANNEL 3.-Analyses of specimens from fhc virgin No. 3 mine : TABLE mle valencedabs of the specimens from the channel channel sample . I .. - *. .._. .. - . :- - ...... _., :': 11s - (mwelnhrpeickntl --.-'--.L--.:. . .. sample were studied in the Mineral Joe No. 1 milie -. - .. . - channel sample, described previously. The reducing Pcrccnt U Percent Pwcent U PercentFe Percent V capacity of the acid-soluble fraction of each sample, Bpcchen Totall, h1.1 Torall Toralr .. . I 1 I I I and the acid-soluble Fe, V, and U (the only soluble I 1 redox-active species present in significant &mounts), all expressed in milliequivalents per 100 grams, is given in table 4. Essentially all of the V, U, and nonsulfide Fe are acid soluble. Milliequivalents of vanadium and iron nre used in the sense that one milliequivalent equals one millimole ; ~~ for uranium, two milliequivalents equal one millimole, 1 Analyst: noosavelt Moore. U. 8. Oeologlml Survey. Add-Insoluble U deter- mined alter leacbly,sample 24 hours In cold 1 N HtBO4. - :. , ; . 7 .- because two electrons must be removed to oxidize *hlyst: o.A.. ccau u 8 omlo ca18urve a Analysts: L. B. Jenkd idk. €I.~elevaux. 8.8. Oeolwld Survey. . uranium from IV) to 4 Analyst: L. 0. Jcnklns. U. 9. Oedoglcal Survey. U( U (VI). 152 GEOCIIEMIS~RTASD BIINERALOGT, COLORIDO PLATEAU URAXIU31 ORES
Ti Si 0.1-0.5 Ni -10.0 0.05-0.1 0.005-0.01 1.0-10.0 0.01-0.05 0.00 1-0.005 13579 13579 13579 2 4 6 010 2 4 6 .0 10 246010' AI Mn Cr . 0.01-0.05 0.005-0.01 0.001-0.005 ,. 13579 13579
Ca Na . .:,:I.. 0.5-1.0 1 I 0.05-0.1 1 I Ga 0.1-0.5 0.01-0.05 0.001-0.005 1 . 13579 13579 13579
Sr MO - . .. , .. Mg ...... __ .. . 0.05-0.1 0.01-0.05 . 0.5-1.0 0.01-0.05 0.005-0.01 0.1-0.5 0.005-0.01 0.001-0.005 I 3 5 '7 '9 135 79 13579 Zr K 0.01-0.05 Be
-. 0.51.0 0.005-0.01 0.0005-0.001 ... . ~ ...... 0.1-0.5 . 0.001-0.005 0.0001-0.0005 13579 " 1 .3 5 7 Q As -13579 Ba Pb .: 0.5-1.0 0.1-0.5 0.1-0.5 ----. .-- .- :. 0.05-0.1 -. .... ~...... - - ... . 0.01-0.05
13 579 13579.. 13579
cu Sn .~ ------*.0!5-0.1- 0.005-0.01 ---_. - 0.01-0.05 0.001-0.-00-5 i3579 -13579 ...... 13579
_. Fmnnm 50.-Semfquantftative rpeetrographfc analyses of spedmens from tbe VIrgin No. 3 mine cbannel sample. Bangen are in percent. - Horizontal 5gares denlgnate npeclmenn. Joseph Hallty. analyst. --
From the mineralogjcal character of vnnadium, it is Garrels (1955, p. 1014-1019, particularly his figure known that it occurs in the clay minerals, probably as 7) discusses the theoretical (and partly hypothetical) vanadium (IV), and in paramontroseite as vanadium pH-Eh stability fields of some major minerals and (IV) ; it is not certain that montroseite is absent, so mineral "Ss"mb1aFs from the Colorndo Plateau. The that some vanadium (In) may be present. The acid strongly mineralzed portion of the channel sample soluble iron is believed to be entirely present in the corresponds mheralogiccrlly to his "Field 2" in that it clay minerals, and in this nssemblage of low valences contains paramontroseite, pyrite, and sphalerite ; cof- is probably present as Fe(I1). At least part of the finite is also present and probably has a stability field uranium is present in coffinite, ns uranium (IV) ; the near that of uraninite. The stability relations of the valence state of any additional uranium may be (IV) vanadium-bearing clays nre not known, but work by or (VI). Foster (Part 10 of this volume) suggests that in this mine chaicnei sanrple [All valucs nre rnilliequiv cnts pcr 10 of sample] rock.
I 1ron.l acid Rcducinc! 3. Vanadium - bearing clay minerals are present soluble Uranium 2 V+ Fe+U CnpaCItY.’ (meqI100g) (mcq/lWc!) (meqllWx) acid soluble throughout the cliannel sample. In tlie more (meq/IWg) strongly mineralized portions, the vanadium-bear-.
6.6 0.03 8.6 3.4 ing clays clearly replace clastic quartz grains. 8.8 .03 14.8 17. I .?8 37.8 3!:! 4. Paramontroseite, coffinite, pyrite, marcasite, and 27.0 8.4 165.9 P9 42. 0 181.9 168.4149. vanadium clap minerals characterize the strongly 25.1 33.6 182 2 22.0 40.2 113. a 158.117.8 I mineralized portion of the channel sample. Much 16.4 3s. 2 il.9 12.3 10.1 46.7 46.285.0 of the uranium is probably present as amorphous . 10.0 - 1.10 17.6 16. 6 UO,. These minerals constitute an assemblarre in I * Extracted for 5 clays on stenm bnth In 33 I percent II iO4. equilibrium under mildly reducing conditions. I Essenttnlly all V and U were soluble In ie extnctlc : value3 given are total V and total U rccnlculntcd from table 3. In thl pnpcr. 8 Analyst: M. E. Delevnux. 0.9. OWIOR $1 Survey. a Annlyst: L. I). Jenklns. U. S. Oeologlcn1 iurvey. SUJIJL44RY AND CONCLUSIONS mineral association. the vanadium contained in tllc The two channel samples reported on support a num- clays should all be V(1V) and the iron largely Fe(I1). ber of generalizations concerning the nature of the If it is assumed that all of the uranium is U(IV), all primary ore and its course of alteration. Most of the of the vanadium is V(IV), nnd all of the acid-soluble generalizations hnre been recognized previously by iron is Fe (11),then the measured reducing capacities other workers. should equal the sum of (U + V+ Fe) , nll expressed in 1. The boundary between mineralized rock and un- milliequivalents. .. mineralized rock can be sharp and independent of The measured reducing capacities of the specimens any observable sedimentary or other structures from the channel sample are significantly less than the and of any changes in original lithologic charac- sum of (U+V+Fe), with the exception of samples 3, ter. .. The Mineral Joe No. 1 mine channel sample 4, and 9. These latter samples appear to fall ideally . demonstrates this clearly. - : . in Garrels’ “Field 2”. In the remaining samples, the 2. The mineralized rock is enriched by a somewhat deficiency in reducing capacity is believed to be due variable suite of minor and trace elements. The to the presence of Fe (111) (and possibly some V (V) ) most important added elements are U, V, Fe, Pb, in the clays and to some U(VI). Specimens 1 and 2, Ba, and Sr. Most of the trace elements originally the weakly mineralized part of the channel sample, -: present in the unmineralized rock have not been must coKtaiiTa considerable amount-of Fe (111) , prob- -- - . removed by the mineralizing process. .- .- . --- - -. ably in the sedimentary clays of the original unminer- 3. Vanadium-bearing clay minerals have been .intro- alized rock; such sedimentary clays probably persist to duced in the mineralized portions of the Mineral some estent throughout the channel sample. A con- Joe No. 1 mine channel sample. Sedimentary siderable part of the uranium is believed to be present clay minerals in the Virgin No. 3 mine channel
-a.-U(VIkthis assumption is based on analogy with -- sample have- .been ...... recrystallized, . .- ...... -. - and -vanadium ...... - uraninite, which invariably --&&ins -considembIc- --. introduced -into-theirstructures; additional vana- amounts of U(VI). Although analyses of coffinite do dium-bearing clay minerals have been introduced. not show any npprecinble U(V1) (Stieff and others, 4. The principal vanadium clays are mixed-layered 195G), coffinite is believed to osidize early and though --.--mica-montmorillonite and chlorite-montmorillo- much the same coiirse as uraninite (Part G of this nite. The vanadium is present largely in a valence volume). The belief that much of the uranium is pres- of (IV). The vanadium clays persist without ent as U(V1) is consistent with the mineralog of the evident alteration during weathering. channel sample in that coffinite was identified only in 5. The Mineral Joe No. 1 mine channel sample repre- a few concentrates, and yet uranium values are rela- sents 3 section through an ore ranging from domi- tively’ high. Tlle uranium is probably dispersed as nantly vanadates, uranyl vanadates, nnd van%- amorphous UO,. dium clays to a dark core of paramontroseite, SALIENT FEATURES OF TEE VIRGIN NO. 3 =E pyrite and marcasite, and vanadium clays; the CHANNEL SAMPLE state of combination of much of the uranium is not 1. The boundary between weakly mineralized and known. This dark core is actively oxidizing, with strongly mineralized rock is sharp. This bound- destruction of the sulfide and the formation of ary rouylily follows a ser1inicnt:iry Louncl:rry. vanadium (1V)-(V) minerals, vanadates, and GEOCIIEJIISTRY ASD JIISER-\LOGY, COLORADO PLITE-IC URISIEJL ORES uranyl van:idates. The p:irnniontroseite indicates Colorado Plateaii. The Xiicral Joe So. 1 niiiic cliaii- that montroseite Iras originally present (Evnns ne1 sunple tjpifics iri:iny sucli deposits. 111 the "pri- and Nrose, 1955! and Part 7 of this volume) and mary" ore. tlie great hulk of vanadium \vas in the clays, that much of tlie vanadium must hare been pres- with tlie vtui:iclium at vtilencc (IV); accompanying it ent previously as vannclium (111). The present was a sniall bnt conunercially import:int content of assemblage is markedly out of chemical equi- uranium! probably present as uraninite or cofiiite, or librium and must be moving toward a higher state both, and probably predominantly locnted in or near of oxidation. Tlie primary assemblage, assuming scattered coalified wood fra,ments. Actually, rnoiit- equilibrium, must have contained montroseite, va- roseite (or parmontroseite) is rare in most ore of this nadium clays, a uranium (IV) mineral (uraninite type. Only where tlie organic matter is abnormally i.:...or cobite), -and pyrite and .marcasite.. . abundant do the rich patches of montroseite ore de- 6. The Virgin No. 3 mine channel sample is in n lower velop, but even here the vanadium clay minerals are state of oxidation than the Mineral Joe No. 1mine abundant. It seems probable that the nature of the ore- channel sample, _..Itcomprises an equilibrium as- bearing fluids may be better defined by the vanadium semblage of piramontroseite, co5nite (and addi- clays than by the vanadium oxides. Speculation at this tional uranium as amorphous UO,),pyrite and stage leads to the guess that the vanadium was original- ...... I:.:. marcasite, and vanadium clays in which the va- ly carried as a V(1V) ion and precipitated with the ,.: : nadium is present largely as vanadium' (IV). clays without tlie need of n markedly reducing environ- '...! ment; tlie uranium may well have been carried as a -.,. Montroseite must have been the precursor of para- montroseite. Thus the original ore must have been U(VI) ion (probablF complesed) and precipitated .. .: a more reduced assemblage consisting of mont- locally diere reducing conditions were adequate-such '' roseite, coffinite (nnd periiaps uranihite), pyrite as near coaly remains. and marcasite, and vanadium clays. This is essen- REFERESCES tially identical to tlie original assemblage proposed Evnns, H. T., Jr., and JIrose. M. E., 1935, A crptnl rhemicnl ... for the Mineral Joe 1mine channel sample. KO. study of montroseite and pnrnrnontroseite: Am. Yin- 7. Both channels studied show unequivocal evidence of '-. ernlogist. v. 40, p. 8614i5. ___ - ____ -
: .I partial oxidation of an original low-valence is- Garrels, R. AI., 1955, Some thermodpnmic relntions nmong the 'semblage. * .. nrnnium oxides and their relntion to the oxidation states of the uranium ores of the Colorado Platenus: Am. ?din- Tlie vanadium clay minerals are not yet completely ernlogist, v. 40. p. 1004-1021. defined and the role in them of vanadium in its various Phnir, George, nnd Levine, Harry, 1953, Sotes on the differen- valence states is' still somewhat uncertain. Little is tial lenching of urnnlum, rndium. niid lend from Ditch- -uKdef- vs~ifig- Ell=-- -=-blende -In-HISO, solutions : Econ. Geology, v. 48, p. 3% - known of their fields, of .. . 369...... -pH conditions,'except that they are-resistant to. osida-:. . S;ieff. L R., Stern, T. m.,and Shem&od, 9. y., 1956, Coaite,. tion. "And yet they' are .the dominant carrier of vana- a uranous silicate with hydrorj.1 substitution: II ne+ min- dium in many of the so-called "primarf" ores on the era1 :Am. Mineralogist. v. 411 p. 675-688...... , .,. .. -- ...... - ...... _ - -...... - - ...- .... - ...... - .- ...... - ...... - ..: ...... - .._ ...... -__...... - ......
I...... _.-......
...... - ... !. . I ...... - :, . ~......
. _. ~ ...... 'rr ...... I . < - L . .,. .:- ...... , e.--. .-. .. .-.- ...... , .. ... '. -. : .. ,i ...... _.. ..