ANNUAL REPORT FOR JULY 1, 1952 TO MARCH 31, 1953, Part 1

by

John ~;i~ Gruner .Lynn UarcU.tL r, .::..nd

Table of Contents

Abstract

5

Part I. l!'ield \~ork in 1952.

Introduction and Acknowledgments 6

White Canyon, Utah

6

San Rafae 1 S;vell, Utah

7

l!'lon-Over 1\rea 8

Lucky Strike JUne, Red1 _{s Canyon 12} Dirty Devil

116

mine,

l~uddy River 12 Part II. Uranium-Bearing Carbonaceous

and. Asphaltic 1,1aterials of the

Colorado Plateau. 14

References 19

Part III. Syntheses of Uranium Minerals.

U-V Minerals 20 Becquerelite 20 Uranopil1te 21 Johannite 22 Schoepite 22 Unlmown 23 Table I 24 Table II 26

Part IV. 1'he Changes from Red to Gray Shales and Silts in Uranium-Bearing Areas.

Introduction 28

Field and Laboratory Observations 28

Nine ralogical Changes 31

Processes Responsible for Color

Changes

31

Inorganic Assimilation of Red Oxide 32 Processes Dependent on Organic

C~o~s

33

Conclusions 34 References Pro~orty oi

35

,.." u

T omilnoon Ublllify JQoil , M®SS Stata Coll&gS ~ Grand Junction, CO 6150

Part I. Part

n.

Part III. l'art IV. Part

v.

Part VI. Distribution Field Work in 1952

Ura~ium-Bearing Carbonaceous and Asuhaltic !4aterials of the Colorado Plateau

Syntheses of Uranium lUnerals

The Changes from Red to GrayShales and. Silts in Uranium- Bearing Areas Primary and Secondary Sources of Uranium in the Colorado Plateau Syngenetic Versus Hydrothermal Hypothesis for the Origin of the Uranium Denosi ts of the ColoraCJ.o Plateau ·

AEC, Division of Pa1-r Naterials

Phillip L. l'Ie:rri tt~ Ne'liJ York . • • • • • 1 - 6 incl. AEC, Division of Exploration

RlW-ANNUAL REPORT FOR JULY 1, 1952 TO MARCH 31, 1953 PART I. PAR'l'

n.

PART III. PART IV. PART

v.

PAR'l' VI. FI:&~LD \1/0:Rl\ IN 1952

URANHJH-BKARING CARBONACEOUS AND

Jl.SPHALTIC !J!ATERCALS OF 'rHE COLORADO

PLATEAU

SYNTHE:BES OF URANIUM MINERALS

THE CHANGES FROH RED 1'0 GRAY SHALES AND SILTS IN URANiill•l-BEARING AREAS PRU!ARY AND SECONDARY SOURCEf:l OF

URANIUlil IN 'l'HE COLORADO PLATEAU

SYNGE!~ETIC VERSUS l!YDROTHE.R!-!AL HYPOTHESIS FOR THE ORIGIN OF 'l'HE URANim! DEPOSI'l'S OF 'l'HE COLORADO PLli.!l'EAU

by

John

vi.

Gruner, Lynn Gardiner, and Deane K. Smith, Jr., Parts I, II, and III.

John

w.

Gru11er, Parts IV, V, and VI.

University of r-linnesota (AT-30-1-610)

Part

v.

Primary and Secondary Sources of Uranium in the Colorado Plateau.

Introduction

36

Availability of Sec.ondary Uranium

37

References 40

Part VI. Syngenetic Versus Hydrothermal Hypothesis for the Origin of the Uranium Deposits of the Colorado Plateau.

Introduction 41

Statement of the '~uestion 41 F'acts Supported by Observations 42 Distribution of Trace Elements Lr? Some Chemical Considerations 50

Discussion and Conclusions 52

Table I

55

Table II

56

ABS'rRACT

'rhie report is divided into six parte, each indepen-dent of the other 'Hi th its ovm list of references. Since the main objective of the worll: is a stud.y of the mineralogy of the deposits, their origin, and experiments 11hich 1tiill support a plausible theory of the d.istribution of the ore and protore, these six divisions seem essential.

In Part I the results of the field llork are discussed as far as conclusions have been reached vii th regard to certain· features. I~or example, the .!!'lop-Over at •remple l•lountain is discussed in some detail. It d.oes not seem appropriate at this place to write about things that need more field observations to support them. It -v;ould only add volume.

Part II contains an account of uranium-bearing car-bonaceous materials which fall into four categories as far as we know no-v1. Part III deals 1tlith the syntheses of U-minerals: 1) carnotite, tyuyamunite, and rauvite in the presence of one of the reagents ln solict form at room

temperature and 100°0; 2) beoQuerelite from uranyl sulfate and Ca{HC03)2 solutions;

3)

uranopilite from uranyl hYdro-xide and uranyl sulfate or HzS04; 4) joha.nni te from uranyl and copper sulfates; 5) schoepite from uranyl nitrate in

the presence of copper nltrate. Numerous experiments are not yet completed.

Part IV the subject of color changes from red. to gray in'shales and silts associated with uranium deposits is discusserl. There e.re only two explanations: 1) 'Ehe change is caused by reduction of hematite, or 2) the very small amounts of hematite which cause the red color enter the hydromicas i'tith the result that the shales become gray. Part

V

is a. discussion, hypothetical by its very nature, of hoi-I much uranium is in sedimentary rocks of the Plateau and ho·w much of i t could have been available for making

the deposits. '!he balance is in favor of syngenetic con-tributions of uranium to the deposits. Part VI i'Jas vTri tten after attendance of' the symposium at Grand Junction. It 'I'Jas f'elt that the various observations that lead either

to a. syngenetic or hydrothermal hypothesis of the origin of the ores should be collected in one paper.

PART 1. FIELD WORK IN 1952 Introduction and Ackno·wledgments

:J.'he field. 1110rk during parts of June, July, August, and September consisted largely of a study of deposits in the general area of White Canyon and of the San Rafael Swell 111i th emphasis on U-Cu and U-aephal ti te deposits respectively. Several days -vmre spent in the l4onument Valley

fiZ

Mine and in the Lukachukai area. The newly discovered deposits between Laguna and {tallup, Nei•l 1•!exico, were examined. It is becoming more and more evident that the problem of the origin and formation of the deposits of the Colorado Plateau is not divisible into definite types but must be considered as a whole. That does not mean that the deposits are all alike and originated under identical conditions. On the other hand, it would be a mistake to think of the sulfide type of having been formed by solutions auite different in character from those of

the asphalti te type, or the lat.ter being very different from the vanadium type, including the Salt \'lash formation deposits. The investigator, therefore, must be familiar with all k.inds, thoug!1 he may want to study one area more thoroughly than another. 'fhis principle has been follo>ved in our field work. Vie have had the full cooperation of all the geologists and mining men we met in the several areas and exchanged ideas freely. We were d.ependent on them for much information that we could not possibly have collected in the short time -.1e had at our disposal compared with the time of their detailed areal geologic 1'/orJr. ~le relied largely on their knolvledge of structures which they had. carefully surveyed 111hile 111e specialized in mineralogical details and in those features which v1e thought could give us a clue to the chemical processes which must have been operative. 'l'he best defined 11_{structural channel" in the}

Moenkopi filled by Shinarump Conglomerate is of little value unlesfl there existed the proper chemical conc1itlons for the precipitation of uranium and unless uranium was present in

the waters which used this channel. b'ina1ly, i'Je 1vant to thank the officials and staff members of the Division ,of Exploration, Grand Junction Operations Office, for their

efforts to help and malte us comfortable in every way possible.

White Canyon, Utah

The work in lvhite Canyon centered around the Happy Jack l4ine. All nevi workings {since 1951) are in uranini te-sul-. fide oreste-sul-. Occasionally a veinlet filled with sulfates is

seen which is a relatively late product of oxidation of the present groundwater circulation. It is amazing how rapidly

the transformation from uraninite and sulfides to sulfates proceeds after a vlOrl;:ing is opened~ In a span of about two months the U-sulfates uranopilite, zippeite, and

johanni te begin to appear. 'Ehe same observation has been made at the Prosnector lUne near Me.rysvale, Utah, in which acidic conditions exist 1,1herever pyrite is oxio.izing. In the deposlts of ·white and adjoining Bed Canyon there is

every evidence that given enough cover to lteep out oxidizing conditions the ore minerals should be uraninite and sulfides associated -vri th carbonized '\'rood. Whether the copper minerals in the nrocess of oxidation form sulfates or carbonates de-pends largely on the amount of

so4=

radical as compared to calcite in the sandstones. Where carbonate is plentiful as, for example, in the Shinarump #2 !Une, Seven Hile Canyon, north of Moab, Utah, oxiclation is very ~ahallow from the outcrop inward because the limey rocks were not only denser but they also neutralized the solutions rapidly.

In this respect these deposits are quite different from the strictly carnotite tyuyamunite ones in which sul-fate solutions play an unknown but subordinate role. At present we have little knovlledge of whether these U-V ores at one time were unoxidized or still are at depth where sufficiently covered. Geologists of the

u. s.

Geological Survey seem to have some evidence to this effect in the

discovery of the rilineral ooffini te in the Morrison formation ( \~eeks, A. D., verbal communication at several symposia).

san Rafael swell, Utah

They are best developed in the San Rafael S'l-;eel and are definitely the primary ores in the sense that the yellow oxidation products are formed from them at a later date. These ores were studied thoroughly in all mines open at present. ·The calix cores lying around on the surface at

the 1Uddle vlorkings of Temple l'1ountain viers also examined closely though the ore portions had been removed before our arrival. As pointed out in other places, the ore ex-tends as high as 30 feet above the Moenlcopi contact at 'remple Mountain but rarely is directly in contact with the

~ioenkopi. In this respect Temple Mountain is an exception -v1hen compared with all other deposits ·which practically alivays are directly on the contact. There are no channels of ore at Temple Mountain. On the other hand, this locality is impregnated with oil ;,rhich is also encountered in the vlingate sandstone about 300 feet above the Shinarumn. This is not ahrays evident l:lecause the rocll:s appear. bleached on the surface but are light bro'l'mish gray a fevr millimeters below the surface. 'Ehe details concerning the mineralogy of the asphaltic and oily Lnater;l.als is given in

Part

II, P•

14.

b"lat Top Mesa,

3

miles '!'rest of Temple I,1ountain, is very similar to the latter but the ore horizons are thinner and at 'Ghe 14oenkopi contact. '

Each of the hJo localities has associated with vihat, for '1'1ant of a better name, may be called a collapse area. The one at the -vrestern edge of the Flat Top .Mesa is more or less an equilateral triangle with sides about

JOO

feet long and one of its apices pointing into the center of the western slope of the Hesa. 'l'he bedding of the F'lat Top .Mesa is nearly,horizontal. The beds of the collapse area dip 20° tp 30° westtvard. If the bleached rock (white only on surface) is Shinarump Conglomerate, the minimum do'Wnward displacement at the eastern apex is 200 feet, and. the maxi-mum is about 300 feet at the western edge of the triangle.

'l'his small area is completely surrounded by brovm Moenkopi formation which is almost flat-lying except for the strata on the western side of the triangle which dip into the col-lapse at about 10° to 15°.

A smaller but very similar bleached collapse occurs half way between F'lat Top Mesa and South Temple Wash. It is again somevlhat triangular vli th its apex and minimum height of collapse southvlard. The bed.s of the collapsed sediments dip 20° tiorthvJard 'l·rhile the surrounding Moenkopi strata are flat-lying.

Flon-Over Area. Few places in the "uranium country" have been discussed more by geologists than the so-called Flon-Over betvmen Nort.t1 and. South Temnle Nountains. The first detailed account of i t was published by Frank Hess

(1922) and ever since i t has been geologically investigated. 'l'he present i~riter interpreted the structure erroneously as a double landslide t'lvo years ago ( 1952, p. 17) because there is evidence that slides are superimposed on the real structure vlhich is a collapse lying ;-;est of the ridge 'Hhich forms the connection bet-v1een the North and South Temple l'4ountains. The collapse on the vmstern edge of the

Flop-Over has a vertical displacement of about 200 feet. East->1ard it decreases and under the connecting redge between the North and South l1ountains it seems to be no more than a minor sag. This statement is based on the fact that the Shinarump formation here can be traced through from the north to the -south. This structure, therefore, causes the beds in the wedge-shaped collapse area to dip about 20° westward. There is, hotvever, no place where this can be seen.

On the east side of the Flop-Over there is no evidence of a break, and the beds can be seen in normal continuity from north to south except for a few hundred feet 1r1here they are covered by large roclt. falls. The true nature of the

structure became evident when the Atomic Energy Commission drilled a vertical hole into the extreme western edge of

the l"lop-Over vlhich here has been called tl:1..e tongue because the projection of the bleached 1t1hi te rock into the yellovJish brownish Moenlwpi resembles such an appendage when seen

from the air. The log as taken by the "lvri ter from the

cliamond drill cores is given belolti• As some portions of the core had become slightly displaced_ during transport some disorepancie s vri th earlier logging by other parties may exist.

Log of Diamond Drill Hole

112-31

ctrilled on t'iesternmost ex-tension of 11_tongue11 _{of I•'lop-Over; depth in feet.}

Depth

o.o-16

16-17

17-19..5

19.5-20.5

20.5-39·0

39-41.0

42-43

L~J-50'1 Shinarumn

50-53?

53?-6H

61-62.5

62.5-64.5

61+.

5-72

72-77

77-78

78-82

82-84.5

84.5-87

87-90

90-93

93-95

95-98

98-101

101-102

102-106

Light gray silty .SS to sandy silt. Some count; a little zeu.neri te.

Light gray

ss,

fine-grained.

Silt 11ith s<;>me horizontal(?) bedding. Gray, fine

ss.

Gray, fine SS l!Ii th brownish irregular layers (oil-bearing); dips

20°-40°.

Bil ty SS vii th zeune rite.

SS, appears brecciated and contains some gray clayey material.

Gray silt; horizontal bedding above; be-coming inclined gradually to

1.5°

totvard bottom.

Core may be out of place between

50-61.

Bad.ly brecciated SS + silt; like

42-43.

Very similar to denth

20.5-39

above except for brecciated chare,eter. ~

Coarse mottled 11 _{salt and nepner"}

ss.

Gray silty SS mixed with

a

little <J.Sphaltite v1hich does not count.

Coarse "salt and pepper" SS with some clay galls.

Shaly rock + SS vJith much pyrite; dip may be

20°.

Coarse SS + pyrite.

Mixed silty SS

+

SS; bedding obscure.

Fine SS + some silty +pyrite; dip

10°-15°.

!Hxed coarse + fine SS + fine pyrite.

Shaly + silty rook ivi th bro'lmish and red

specks. '

Flne gray SS + silty SS + patches of pyrite. The same bu.t slightly coarser; dip

5°-10°,

Fine SS i'ii th some pyrite areas. ·

SS w:!. th almost black areas.

Asphaltite + asph(\tltic

ss;

high count.

I!'ine SS 'l'li th pyrite nodules; vJhi tish except for pyrite areas.

De nth

106-125

. 125-134

13!f-146

14<''-158

146-166 •

.5

166.5-172

172-190

Moenkopi

'190-193

195-201

201-202

202-21.5

21.5-227

227-273·.5

Strati~raphic

00-19.

19.5-.53

or to

61

61-166 • .5

166 •

.5-190

190-273·5

!\tedium SS >vi th patches or nodules of coarse clark

ss;

some of the dark has U; pyrite nodules common. These may be surrounded by asphalti te •

Conglomerate + SS ':Jith large dark areas; some asphaltite

+

much pyrite; ~ ~·

The same but less radioactivity.

Light gray SS

+

conglomerate

+

pyrite. Conglomerate

+

coarse darlc SS

+

pyrite patches.

:inmost white fine to medium

ss;

din not

over

10°

at most. ·

Conglomerate, much like Shinarump; no red pebbles, but gray ones

+

pyri.te.

Somewhat conglomeratic SS·

+

pyrite. Light gray; sandy silt; dip

5°.

The srune with pyrite nodules.

Silt

+

fine Ss light gray; some dark pyrite bands, almost horizontal. l·1edium gray, ail ty

ss.

Silty 88 interstratified with silt; all light to medium gray. Borne very thinly bedded; all contains disseminated pyrite. Classification:

Doubtful as to its origin; it could be \Vingate or Chinle.

Chinle. Shinarump.

Doubtful, perhaps !>l:oenll:opi but could be Shinarump.

J.loenll:opi.

'rhis core is entirely unoxidized and. except for the top

20

feet did not undergo alteration caused by near surface conditions. All core except the upper 64 feet contains considerable pyrite. Some contains very much. ~'his in

i tsel:t' ex-plains the light to dark gray colors.

It is, of course, impossible to te.~:l whether the drill hole stayed in 'Ghe collapsed mass or perchance entered the undisturbed Moenkopi at a depth of about 160 to 180 feet •·rhere the dip of the beds is low. It is extremely doubtful

that a block of the Shinarump could have subsided vrithout the same having happened to the underlying ~ioenl<.:opi.

The structure as interpreted by the· writer t.rould be a triangular block elongated in E-W direction pointing toward the east and ending somewhat beyond the cliffs of the

Shinarump ivhich, as mentionect above, can be seen to continue throug,.VJ. from north to south with a sag of perh.:;1ps 20 to 40 feet. The i'Iest side of the triangle is about 400 feet long and must have dropped about 180 to 200 feet through the l'ioenkopi "VJhich surrouno.s the bloclt completely. The general dip of these undisturbed rocks is about

5°

to 10° B. I~. ·while the l·!oenkopi near the western contact 1t1it.h the blocl~ has assumed dips to-v;arcl it which reach

15°

to 20°, b11t only locally. In other v/Ords, this structure :i.e in every respect similar to that on the v1es'G edge of Flat Top !·1esa but it is more elon-gated. It is so conspicuous because the high cliffs on both sides of the block set i t off, Also, the rock fal1.s have added to the color contrast of vlhite, bro1rm ana. reo.. It was mentioned in previous papers by the 1r1riter that the 'ilhite results from the removal of hydrocarbons from the surfaces of the sandstones, either Shinarump or \!Jingate. l.J:uch of the red. is causerl by the oxidation of sideritio sandstone of the Chinle and W:tngate formations at· the contact of the t'l'lo.

As all the formations contain e.t least some pyrite, oxidation of' it probably contrilmted to the contrasting colors.

It is· undoubteCl.ly true that in the Flop-Over area fis-sures exist \·lhich paros from the loloenkopi to tho ~lingate

but whether they are continuous e.nd how fe.r they are associ-ated with the block which subsio.ed is unknm·m. It is also

unkno;-m vlhether these fissures ivere responsible for the very small U-V deposits vlhich occur near the bottom of the VJingate on both sides of' the Flop-Over. The ore is also as13ociated '"ith plant r-emains in the Wingate, and i t ;1ould seem strange that solutions coming from belovJ ;wuld pick exactly this plan'c horizon in the vlingate to deposit their loads v1hen they could have found other equally favorable beds on the way up at a lo·wer level.

In this Flop-Over, particularly on the east side, one :t'inds locally a very peculiar stain in the \'!hi te \vingate sana.-stone. It is a very light bluish green color. It does not react for Ou, Fe, or Cr ancl probably is caused by

v.

It grades into a yello~iish brovm near the surface of the rocl.!:s. Since i t is but a s);ain we have been unable so far to obtain a satisfactory chemical test.

From the foregoing description of the drilling, i t is obvious that the asphal ti te depoai ts '11ere in existence be-fore the collapse. ¥Jhat caused these subsidences in the nature of a collapse is unlmmm and any att.empted explana-tion is conjectural. The vlri ter would suggest that salt or gypsum plugs or masses were removed by leaching, if there is any reason to believe that salt beo.s existed in this

part of the Plateau as they do further east in the Salt Valley Anticline. The leaching might cause solutions to

rise through the overlying sedimentary rooks but they 'I'IOUld be quite different from magmatic emanations. And as pointed out before (Gruner, 1951, P• 17) there is .nothing that

suggests thermal waters, certainly the gypsum, asphaltites, oils, and other carbonaceous materials do not.

Lucl~:v Strike Mine, Red 1 _{s Cani£Qlli_ This mine has been}

considerably enlarged since

vie

sa'VJ it last in 1951. It has cteveloped into an asphaltite ore body. Almost all

zippeite and other secondary minerals have been removed. :l'here are in places two. conglomerate lenses or horizons, one directly on the Moenkopi which is the best ore and an-other separated by 1 to 4 feet of sandstone from the lower. The pebbles are quartz and chert. The latter are full of fissures filled >vith asphaltite which is secondary. Judg-ing by microfossils in similar pebbles they are Permian

in age. Much of the ore is concentrated in irregular asphal-ti te masses associaterl Hi th trees. I'he ore values are ex-tremely irregular and unpredictable, but, v1ith the great thickness of sediments overlying the deposit, nothing

llli!

asnhal ti te ore shou1(1 be expec tea. Galena in almost micro-scopic cubes is scattered through the conglomerate. Cobalt sulfate (at one time bieberite before dehydration) forms a conspicuous efflorescence above 'Ghe upper· ore lenses at one of the portals.

Dirty Devn 'It£~. l~uddy River. This deposit is very similar to the Lucky Strike in mineralization, though

5

to 10 miles distant from 1 t. Its conct,lomerate lenses reach thicknesses of 10 feet. 1'rees aredcommon. They have as usual much pyrite associated ,,lith them. Gray clay lenses ·and galls are very common. At the contact of the !•loenkopi

and Shina.r11mp a large chert lens (at least

5

x

6

feet and

6

inches thick) occurs which has considerable asnhaltite and a 1:1. ttle chalcopyrite in it. At first this ~1as thought of some possible genetic significance, but these lenses have been found in other places;< entirely in the Hoenkopi but near its contact. They are a bro~mish yello'l't to pinkish chert vihich is a replacement of original calcite lenses. No organisms have been founcl in 'chem. They are geologically very unusual and perplexing where they are found directly at the Hoenlcopi contac'c as here. A large fault striking NW passes about

50

feet southwest of the deepest mine imrlc-ings. At one time it was thought that i t might have had some connection ;·rith the introdnction of the ore, but the ore gets poorer towarcl it. 'l:he ':Jriter is practically certain that the ore is prefaulting in age.

It is not intended here to give a description of the various c1eposi ts visited, though this has been rlone for the

*South •remple Wash, Pay Day Mine, ana. in several places of the Green Vein Mesa.

mineral associations (Part III. Annual Report July 1, 19.51 to June

JO,

1952; see references in Part

VI

of the present report). Home have not been opened. up sufficiently to form a :picture of their primary setting. The accounts, hmvever, that have been given in the preceding pages should help in watching for criteria in exploration and development. At present it appears that uranium might be found. almost in any formation on the Plateau provic'Ied enough prospecting is done, but we know that this is not true. vie have some cri-teria as, for example, fossil '1-IOod and discoloration of shales and silts. Can we find any others as good as these'<

PART II. URANIID~-Bll:ARING CARBONACEOUS AND ASPHALTIC l4ATERIALS

m'

THE COLORADO PLATEAU

The present investigations on carbonaceous materials are confined to those in the Shinarump Conglomerate. The most suitable areas for study probably are in the San Rafael Swell, Utah. Practically all of the important U-bearing material in the Shinarump is probably v1ithin a stratigraphic distance of 30 feet of the !>1oenkopi con-tact and is not found in the underlying r'!oenkopi :forma-tion itself. Jv!ost uranium is usually very close to the contact, though in the Temple Mountain area some may be as high as 20-30 feet above the contact.

Temple Mountain, the Flat Top !vies a (which is also called the Shinarump Mesa), the Green Vein Mesa 10 miles further 11est, and the Red Canyon {v;i th the Lucky Strike mine) are best suited for study of U-bearing carbonaceous deposits. Still further west are the Dirty Devil Claims on the !4uddy River which are of the same type as the 'remple Hountain deposits. In the northern part of the San Rafael S<;ell are such claims as the Dexter group and. the Lone Tree which are very similar.

In all places in the Swell more than one kind of car-bonaceous stuff, if hydrocarbons are included, may be observed. These are:

1) carbonaceous ligni tic plant material in general.

2) asphaltite, or as it has also been called, thucolite, though this material does not contain thorium, for v:hich thucoli te v1as named originally.

3) gilsonite and similar hydrocarbons vlhich are a kind of asphaltic material and used to be named jet in the past.

4)

liquid hydrocarbons.

The third and fourth are the only ones readily soluble in ordinary organic solvents.

The presence of' liquid hydrocarbons under

4)

con-fuses the question of origin in several respects. They have been in the Shinarump for geologic ages '\vi thout having become appreciably polymerized. Being closely associated vli th radioactive material, they should have been polymerized if the ideas of Davidson and Bowey ( 1950) are to be acceptecU The liquid hydrocarbons give off a strong odor and are easily distilled out of the rock. They do not contain any appreciable uranium, at least,

not any that can be found i'Ji th the ordinary t',e iger in-strument. The liquid hydrocarbons are not restricted to any particular ·area in the Swell but are found in

many including the ones already mentioned. In the Temple Mountain area they are found not only in the Shinarump Conglomerate but also locally in the vlingate Sandstone 300 to 400 feet above the Shinarump.

-'

The liquid hydrocarbons stain and penetrate the sandstones along definite texturally pervious bedding planes. 'l'he saturated sandstone has a dirty greyish broi'Jn to dark bro~m color and banding. If, as at the Temple Mountain Flop-Over, for example, the roclt is exposed to some oxidation, the hydrooarj)tms on the sur-face are removed and the roclt assumes a whitish appear-cmce ~;hioh is a few/ milimeters thiolt and which has been in the past mistaken for a sign for hydrothermal leaching by some geologists. such whitish 11_oxidized.11 _sandstone may contain small amounts of uranyl minerals, for example, zeunerite and carnotite or tyuyamunite.

The hardened hydrocarbons mentioned under

3)

which look like gilsonite or jet are commonly found in joints and fissures and are derived from the liquids and like

them contain no appr€ciable uranium. The consistency of this material differs widely, ho'lvever. It looks

usually 11_{pure 11 , that is, free of minerals, and is easily} soluble in organic liquids.

The most puzzling substance is the asphaltite or thucolite mentioned under 2). It is unlike any of the other carbonaceous materials. It occurs almost free of impurities, that is, vzi thout any visible inclusions of sandstone or any other contamination by the sediments. From these purer masses ,it grades into areas in which it is present as fillings between the sand grains, that is, only interstitially, in very small amounts. The purer the asphaltite the lower is its specific gravity and the better conchoidal fracture it has. It is practically opaque to transmitted light. In polished "sections i t may show a certain amount of anisotropism.

Chemically it is a very complex substance. Some of the chemical data given here are those of Dr. Thos. 01_{Brien of the School of Chemistry ocf the University of}

l4innesota v:ho 'lv-orks on this problem for the Atornio Energy Commission. He found, for example, that not enough hydrogen is present for the material to be a hydrocarbon in the usual sense of the ;.:ord. - The excess of carbon is great. Several per cent of vanadium oxide are present but not as

v

₂

o5.

The highest gracte mate,rial

has several to seven or more per cent of U308• Spectro-graphic analyses sho-vJ many other elements. This asphaltite is slightly soluble in chloroform, more in complex solv€mts in autoclaves at elevated temperatures. '~he asphalt:!. te can be oxidized completely in concentrated nitric acid in about 21+ hours after· 1vhich the solution may be decanted and the clastic material by this method removed. From such solu-tions colloidal Si02 may be obtained. 'I'he 1-1riter determined the non-clastic S:l.Oz in one of the 11_pure11 _{masses as about}

3

per cent. 1'his SiOz may be chemically combined. 1'he asphaltite looks very interesting when viewed in polished. or thin sections unrlsr high po¥Jer. Strange as it may seem, the asphaltic material replaces the grains of the sand leaving highly corroded remnants of quartz. 'l'he question has been raised v1hether the quartz grains could have been a:t;taclwd and dissolved by some earlier inorganic solution.and the asphaltite later deposited in the voids. There is no evidence of such an earlier nrocess. Under the microscope it looks as if the quartz grains had been corroded from the borders inward until all or most of the quartz.had been consumed where the action was most intense. The action in the sandstone decreases outward from the almost pure asphaltite areas and the quartz grains shovJ less and less corrosion till the asphalti te prao tically vanishes, leaving only sandstone. All shapes of such re-placements are found.. Host of them folloi·l more or less a particular sand.stone or conglomerate lens. The asphaltic ore, that is, the cemented material, seems considerably tougher than the surrounding porous roclt. The miners Jrnovl this property very well, of course, and have mentioned it in every instance.

A puzzling feature is the occurrence of globules.and balls of asphaltite ranging in size from pinheads to large marbles. These also are rich in uranium. Stteh snherical bodies are numerous in a fe1•J places and look as if they had been asphaltic pebbles originally that had rolled into place 11here they are found now, an interpretation given

to them by Frank Hess (1922). It is, however, not impossible that the spherical boclies are replacements. This phase of the investigation is still in its early stages.

The uranium in the asphaltite is present in at least two forms. One of these is uraninite. 'l'his mineral is visible under high magnification in polished sections. The largest particles are about 10 microns in cUs.meter; the smallest cannot be resolved with oil immersion. Pyrite of similar dimensions always is associated vii th the uranini te. 'l'he arrangements of the particles suggest some structural • or textural control (Rosenzweig, Gruner, and Gardiner,

G.s.A.,

bodies. ~'here are also some fan-sllaped outlines i:thich suggest organic structures. In one 'section the uranini te particles may follm·J the boundaries of former quartz or other clastic grains. These uraninite particles do not accoun'G for all the uranium present. Preliminary tests by Dr. Thos.

o•

Brien ino.ica.te the presence of' organic complexes containing uranium. For example, some speci-mens 'tvhen heated to about 200° in the absence of air de:posi t

a

yelloiv sublimate on a cool surface itJhich is highly radioactive and. contains uranium. ~l'his sublimate can hs.rdly be. derived f'rom uraninite. The volatility suggests an uranium compound which might be classified as an organo-metallic one.

The amount of' uranium in asphaltite, of course, varles Lsrea'cly and. in places may be altogether absent

excep'G for traces. Carbonized material which. is definitely of plant origin because i t shoviS ce1·1 structures carries little or no uranium if' asuhal'Gi te is associated with it. If no asphaltite is present, carbonized material may be ouite rich. l!'or exanmle, we have a specimen from the Small Spot mine on the Calamity Mesa, ·colorado, which by actual analysis contains

33%

of

UJ08•

We

investigated

this material by x-ray but could get no pattern except in one or two small areas where ~1e found the mineral called coffinite by the United States Geological Survey. This is a nevE uranium sllicate•

It is kno-.m, of course, that near the surface on oxidation asphaltite as well as the carbonized wood dis-appear. In some cases ·t;he 'ltJood becomes sllicif'ied, as shm-m especially well at the Honument Valley No. 2 mine. 'l'he uranium in 'Ghat case forms uranyl compounds, ·which

with any vanadium also derived from the wood or asphaltite, may form carnotite or tyuyamunite or some of the lesser known uranium vanadates. In some cases i t wlll go to torbernlte, zeunerite or their meta minerals respectively. If the vanadium is in large excess, as is common, the

excess of' vanadium has a teno.ency to be centrifugal in l ts behavior. We find, for example, at l'!onument No. 2 mine, f'lonument Valley, that the concentratlons of' uranium are high in the centers of' the lltrees11 _{and decrease aviay}

from those places. Vanadium then is commonly found, if it is in great excess, in the very bottom of the Shinarump and in the underlying DeChelly sandstone which i t seems to have replaced in part.

The writer believes that the separation of uranium and vanadium may also occur under other conditions. ];"or example, vanadium salts are ~ soluble in reduced form, probably ln the state of' tetravalence. Under these

soltlble. If reduction occurred, let us say by HzS or other compounds derived from the organic matter, the

uranium vJould be deposited as uranin:!. te vJith the sulphides of iron and copper while the vanao.ium, being soluble,

would be carried in solution to a new environment. Such behavior o ould account for the almost complete absence of vanad:l.um in such sulnhide-:-uranium deposits as the Happy Jaolc mine. Of course, as long as the vanadium and uranium 1;ere tied up organically there could be no separation under these conditions.

FtEFERENCES

'Davidson,

c.

F., and Bo;vie,

s.

H.

u.

(1951), On thuoho-lite and related hydrooarbon-uraninite complexes: Bul. Geol. Survey Gt. Britain, No.

J,

p. 1-19.

• Hess,

FrankL. (1922), Uranium-bearing asphaltite

sedi-ments of Utah: Engineering and lUning Journal, vol. 114, p. 272-276.

PART III.. SYNTHESES OF URP .. NIUJ:! MINERALS

u-

V !Une rals

Since the publication of 11_{New Data of Syntheses of}

Uranium !Unerals11 _{(Part I. Annual Report for July 1,}

1951 to June 30, 1952, A.E.c., RM0-983) a considerable number of nevi experiments ·have been set up. Some of them are completed, others are still runnlng. one series cteals vii th the reactions and products that re-sult when uranyl sulfate solutions* come into contact with chemically pure vanadium oxide, V205, or minerals like m.etahewet.tite (CaO•JV205•9HzO) which is found as fairly good crystalline natural material. Vlith the appropriate additions of K+ or

ca.++

i t ~Jas exPected that carnotite or tyuyamunite would result. As may be seen in Tables I and II this ha:opened in some ex-perimen'Gs but not in others. Only- those experiments

of this series are listed vJhich producecl compounds

corresponding to natural ones. Some resulted in unknown crystalline materials.

After the experiments had been prepared, they v1ere

occasionally shaken and their pH1_{s and x-ray patterns}

determined. These intermediate detenninations are not recorded in the tables. Exoeriments of Table I were

put on a steambath to speed~up the reactions. The others :;,Jere kept at room temperature: at which reaction is

naturally very slov1 and still incomplete in some. In all the experiments the pH1 _{s decreased fairly rapidly.}

This was caused by the withdravml of cations from the solutions to make insoluble compounds. The only exception was Exp. A49 in ·tvhich, as \vas e:li."].Jected, an in -soluble precipitate formed at once. Even after 325 days no crystalline substance had separated, though the solu-tion was less basic than at the start and all the brovm V205 had disappeared.. 1'he conclusion that one may dra~l

is that in a basic environment a reaction beti'leen U and Vis so slowthat it is beyond the range of experimenta-tion. It is of considerable interest that rauvi te or uvanite are intermediate products in those experiments in which carnotite or tyuyamuni te are the end products. This is contrary to the belief of some investigators that rauvite is a decomposition product of tyuyamunite.

Becquerelite, 2U03•JH2

o

Exo. J-229 and J-2.30 v1ere dunlicates. Solutions of 0.01 M uranyl sulfate (pH 2.9) 'l'rere treated -v.;ith saturated

Ca(HCOJ)z solution which was added dropwise for an hour a day. After about a week a precipit~te began to form at a uH of 5.0. In the next 90 minutes about 90 more drops- of Ca(HCOJ)2 were added. The pH was 5.6. After standing J weeks and 7 weeks respectively, samples were v1i thc1rawn and x-rayed. They were typical becquereli te. More of this type of experiments are in progress to find out the influence of concentration on the uroducts. It is quite certain that the earliest precipitate, which 'Nas 'lvithdra-vm vJithin a clay after it had formed, is prac-tically amorphous. An important point we woulct like to establish is the exact pH at vJhich precipitation begins. This cannot be done unless the pH is changect very slowly, which results in a large volume of Ca(HCOJ)2 solution

that must be added. ·

Ura.nopilite, (U02)6804(0H)lo

This mineral and zippeite (2UOJ'

so

_{1 ·nH2 0) commonly} are early products of oxidation on uranlnite in places where pyrite is also plentiful. It is found at Ha.rysvale, Utah, and at the Happy Jack mine, White Canyon, Utah,

where it forms very rapidly after exposure of the vrorkings to air. It would seem. that there vmuld be no difficulty in synthesizing it by simple' fiydrolysis of uranyl sulfate. 'l'here are some difficulties involved, however, as numerous experiments have shovm. Some qualitative experiments

have given the mineral but the reactions did not go to completion except in one case.

Exp. J-258. Some U02(0H)2 V~as spread on a large glass slide and a. fevJ drops of 0.1. N HzS04 11ere put in contact with U hydroxide. Another glass slide was used as cover. In this way it was possible to examine any

changes under the polarizing microscope. The whole assell)bly vTa.s put under a bell jar with a dish of vrater to keep the humidity at value corresponding to the temperature of the laboratory. After 10 weeks. three greenish yellovJ circular aggregates of crystals had formed among the remaining

hydroxide which i'Jere highly fluorescent. The pH· of the acid had increased from about 1 to J (hydrion paper). The x-ray pattern of this new grovJth is that of uranopilite. The optics also check fairly <Jell this mineral. Another experiment, J-257, in >vhich the acid was a.boLtt

5

N resulted in the conversion to ordinary U02S04 vihich dissolved. on the glass plate.

artificial compound, is wetted vlith dilute H2S04 (1:)).

The sample is left to dry. After this, it is kept just 'tvet vJith distilled water. All of the hydroxide had been converted to uranopili te in 4 v1eeks as checked by x-rays and optically. Also, uranopilite is highly greenish yellow fluorescent, while the hydroxide has a very dull fluorescence. If too much acid is used, i t is converted to the soluble uranyl sulfate. No zippeite was obtained as an intermediate product in these experiments.

Exp. A-76 and J-250 were quantitative. To 2g. of UOz ( OH) 2 enough uranyl sulfate solution ( o. 20 J,l) '11as

added to make the ratio

u:so4""

6:1. The amount of solu-tion '<Jas 6. 6 co. After 4 days the PH was

J, 9·

On fre-quent stirring, two different yello~l colors c auld be seen after about a month, iis both remained, a sample Wls

:x-rayed. It sho't'ieCJ. uranopilite and the original hydroxide in perhaps equal amounts; pH = .3· 9· For the next

.3

weelcs about .30 co of -v;ater '<las kept on the material and. a few drops of H2S04 were added to keep the pH at

3.7.

The former high fluorescence disappeared gradually and an x-ray sho'l'led that all of the sample had gone back to the hydroxide. Apparently the concentration of solution to solid is more important in this case than the pH. 'i'he solutions are no~J gradually evaporating and sorne;;here a point should be reached where uranopili te 'l'lill appear again. 'l'his 'l'lill be reported at some later date.

Johanni te, ( Cu, Fe) 0•

uo

_3•

so

3

•

L~H

2

o

Expo

J-261A and J-261B. To 10 co of 0.20 M uranyl

sulfate solution Tf.as added 0,5g. of CuS04'.5HzO. This gave a ratio UOz

+ :

Cu "' 1: 1. A piece of an aragonite crystal was aCJ.decl to A and a cleavage piece of iceland spar to B. The underlying thought -v1as that aragonite might react more rapidly than calcite; pH at start 1.9. 'i'he reao.tion 'tvas very slow but gradually greenish hair-like crystals began to form. 'l'hey were in spherical aggre-gates about 1-2 mm. in diameter. Also, thin hairs of gypsum developed. The pH at this stage was .3·9· After .35 days the green crystals were x-rayed e.nd examined optically. They are johanni te; pH = 4.

05

for A and .3.

65

for B.

Sohoepite, 4uo

₃

_·9H2

o ·

EXP. J-264A and J-264B '1-lere set UP to find out whether

U and

Cu

would combine in the absence of S04"". To .5 co of

Cu(N03)z•3H2 o dissolved .in 10 cc HzO; pH of' solutions

2.95.

To experiment A ,,,as ad.Cl.ed a cleavage piece of iceland spar, to B a. fragment of aragonite. After some time aggregates of rouncted gr~:cins from 0. 1 to

o.

3 mm. in diameter formed in both solutions. ~l'hese t1ere yellovl in .color and non-fluor-escent. After a month they ;-;ere x-rayed and proved to be schoepi te; pH =

5.

20 for .A and 4. 6Lr for B. '.Chis shmvs that Cu does not enter into hydroxides of

u.

The absence of fluorescence suggests, ho-v;ever, that traces might be present. Blue green crystals of a copper compound formed gradually after the schoepite had started to precipitate.

Unknown

Two experiments J-263A ancl J-263B contained solutions of uranyl sulfate and cupric nitrate; 10 co 0.20 ~·1 sulfate and

o.

24g. of Cu(N03l2• 3Hz0 which gave a ratio

uo

_{2 ++:cu} =

1: 1; pH "' 2. 2. Icelancl spar and aragonite respectively v1ere added. After a. -v:eek pistachio green moss-like aggre-gates began to form. :J.'hese were. x-rayed after 4 vieeks and gave a gooct but unlmown pattern; pH for both

4.65.

A

number of' attempts vJere made to precipitate Pb-U-phosphates but they were failures because the Pb-phosphates appear to be more insoluble than the <'iouble salts. Therefore, these experiments will not be a.escribed.

All described experj.rnents shovl clearly, as also dis-cussed in Part VI, that these reactions tal1:e place easily in acidic solutions and that the minerals are stable in some cases even at lo>·i pH1 _{s. This, of course, does not}

prove the.t they cauld not form in a. somewhat basic environ-ment, but since U is practically insoluble in neutral or slightly basic solutions, the solutions could not carry more than infinitesimally small amounts of the metal. As natural carbonates of U are extremely scarce, for ex-ample, such mineralri as vogJ.ite e.no. liebif;ite, it must be concluded that they originate under very unusual conditions which eould be basic ones.

TABLE

r.

Exneriments with uranyl sulfate solutions and V compounds at 100°0 ..

Exper. Initial l!"inal l'ime Temp.

Number Constituents Ratio of Cations· pH pH 'Days)

oc

Products Remarks A-40 l•letahe'l'le tti te

U02S04•JH2o

u

:ca ~v 1.75 1.3J

4J

100° rauvite Yellow

preci-H2

o

2.5: 1 :6 pi tate.

A-41 Hetahewetti te

Le3

100° rauvite

U02S04•3H20

u

:ca

:v

3.12 1. 89 and and after 16 Yellow

preci-Gaco₃ 1. 2: '1 :4 210 room days. pi tate.

temp. re.uvi te. H2

o

A-42 ~1etahewetti te

. Uo

₂

so

_{4• 3H2 0} u .: Ca

:v

tK

1. 89 lol7 1-J-3 100° carnotite Yellow

preci-KHCo₃ 2.5: 1 :6

: o.

5 pi tate.

H2

o

_. .

-A-43 _v2o5

uo2so4•3H2

o

u

:v

:K

·1.37 1.12 43 100° carnotite Yellow

preci-K2

co

₃ 2.75:2 :1 pi tate.

H2

o

Number Constituents Ratio of Cations pH

pH

(Days)

oc

Products Remarl\:s

-

--A-44

_Vzo5

UOzS04• 3Hz0

_u

:v

:K

1.6o 1.13 43 100° carnotite Yellow

preci-KJIC03

5

:4 :1 pi tate.

HzO

A-'?5

vzo5

UOzSOI.j.' 3Hz0

u

:v

:ca

3.20 l. 87 17 100° tyuyamunite Yellow

preci-CaC03 2.75:2 :1 pi tate.

HzO

Number

A-39

A-49

I

A-.50

A-.51

A-52

I

Constituents Ratio of Cations pH pH 'Days) Products Remarks !

" Blue, black

AE-446

has no

def-V mineral

AE-446

ini te fon:nula.

_1J.9.5

_1•9+

210 carnotite

UOzS04•3H,O

u:

K ~

1: 1

KzCOJ HzO i' _:_

v

₂

o

₅

_{8 • .58}

UOzS04•JH20

lr

:v

_:K

_after

_7·3.5

_32.5

_{amorphous Like}

_A-69,

_but

KzCOJ

1'-.4:1

:5

46

da. more

K.

HzO

v2o.5

U02S04"3Hz0

lr

:v

...

•1?'

_2.7

1.4)

₃₄₀

_{uvanite Bro-vmish ye llo'l·i}

KzS04

. 4:1

:.5

precipitate.

H20

tahe;.;e t ti te

U02S04•3Hz0

tJ

: Ca

:v

:K

_{1 • .59}

0.3.5

33.5

a potassium Light chocolate

KCl fLl : 1

:6

:48

uranyl van a- precipitate.

HzO

date.

He tahe11e t t i te Some fluorescent

U02S04• 3H2o

J '

:ca

:v

:·K

_{1. 68}

₃₃₅

_{a potassium green crys te.ls}

KzSOLy 0 : 1

:6

:37

uranyl sul- of potassium

HzO

I

fate. uranyl sulfate.

UOzS04•KzS04•2H20

N

Ch

Number

Constituents

Ratio of Cations

pH

pH

days)

Products

Remarks

A-66

11etahewe tti te

Uo2

so

4•JH2o

u

:ca

:v

1. 75

1.10

290

rauvite

Yellov;

preci-H2

o

2.5: 1

:6

pi tate.

A-67

Metahewettite

UOzS04•.3H20

_u

:ca

:v

_.3·

₁₂

1.55

)00

rauvite

Golden yellow

CaCOJ

1. 2: 1

:4

precipitate.

H20

A-68

l·ie tahe;sre tti te

1290

U02S04•JH2o

u

:ca

:v

:K

1.89

1.05

rauvite

+

Yellow

preci-KHC03

2.5: 1

:6

:0.5

carnotite

pi tate.

I

H,Q

_...

A-69

_v2o5

_uvanite

₊

U02B04• JH2

o

u

:v

:K

1.,37

0.90

310

carnotite(?) Yelloi·l

preci-K2COJ

2.8:2

:1

+

unlm o

vr.a

pi tate.

I

H2

o

-A-70

_V2o~

U02 04•JH20

u

:v

:K

l. 60

0.9

290

uvanite

Golden yellow

KHCOJ

5

: l~ :1

precipitate.

H 0

₂

-PART IV. '!'HE CHI1.NGES FRO!" RED TO GRI\.Y SHALES AND SILTS IN URI\.NIID<!-BEARING ARF.AS

Introduction

The relationshiu to one another of certain red and gray shales of the Colorado Plateau is a problem closely tied uu with the distribution of uranium in this region (Fischer, R. P., and Blackman, D., 1949; Fischer, R.

P.,

1950). For this reason in particular, it has been studied lately to a considerable extent. A paper by A. D. \'leeks

(1951) deals 'IIlith the reo. and gray clays in the ore-bearing sand.stones of the l4orrison formation of Western Colorado. '.rhe study may be extended geograuhicalb[ to include parts of Utah, Arizona, and Ne11 Mexico as well as arid regions in other continents. Stratigranhicall;r it reaches from the Upper Paleozoic to the bottom of the Cretaceous. In the present investigation we are chiefly concerned with the Triassic roclcs though there is some mention of others.

'.t'he upper fev; feet of the Moenkopi formation at the contact of the Shinarump conglomerate deserve our attention because here a change of the sediments from red to gray is very common, almost the rule, in uranium areas. The Shina-rump itself, while made up largely of conglomerate and coarse sandstone, contains also numer~us lenses, blebs, balls, and other shapes of clay or shale which are greenish gray 'tvhere uranium and fossil plants are found .• - The over-lying Chinle formation does not have a sharp contact with the Shinarump but grades into it. In places it may be difficult to find the Shinarump conglomerate because it is very thin. 'l'he Chinle has red and gray silt and shale beds or mottled red and gray strata. In uranium areas the Chinle shales just above the ore bodies are usually gray. As this gray color is much more widespread than the immedi-ate ore areas according to E.

v.

ReinharCI.t (1952, p. 12), it is not certain that any change from red to gray or to grayish green is tied up vJith the immediate presence of uranium. It is a fact, however, that in ms.ny places a conspicuous color change has taken place 'tvhich is not for-tuitous but in some r;;ay connected with the solutions ~vhich

brought the uranium.

Field and Laboratory Observations

Anyone familiar ivith the sedimentary formations of the Colorado Plateau knows that the removal of red colora-tion is a phenomenon not solely associated vii th areas of uranium-concentrations (Moulton, 1926, ana_ Van Houten, 1948),

though i t has been studied more :i.n these places. Where, for example, itlhite bcmds and lenses vlith blunt and rounded. terminations occur in reddish sandstone of the Entrada, it may be seen under the microscope that the red hematite is in such minute amounts that it is almost imoossible to observe it in thin sections• In other words, a thin section from medium-grained red.dish sandstone is apparently identical to one of adjacent white rock~ The little bit of hematite 'Vhich can be seen is usually in extremely small o.usty aggregates around and between the quartz grains and the micaceous cement~ It can hardly be more than a small fraction of one per cent by volume. Such widespread, large-scale discoloration is usually ascribed either to primary deposition or diagenetic processes having

follo-v:ed soon after (l•!acCarthy, 1926, P• 35; Van Houten, 1948, P• 2122).

A more difficult case to explain is the bleaching of sandstones along almost vertical fissur-es vihich out across nearly flat-lying beds for distances of hundreds of feet. 'l.'he width of discoloration may be as much as

50

feet but varies consiclerably. The best example knovm to the "VIriter is just south of the highway about 3 miles northwest of the Happy Jaoli: mine in White Canyon, Utah.

vie

lmov! that something like a solution must have move~t along such fis-sures but 't·Jhy the contacts should be sharp in the porous roclt and v1hat had the power to dispose of the hematitic dust, even though there vias not very much, is not clear.

l'loulton (1926, p. 306) gives some similar large scale examples outside of the Colorado l>la teau in l'lontana.

It has been shown by Keller ( 1929) that the following reactions may occur: Hematite is reduced by J:J₂

s.

The resulting ferrous iron may then be removed by -vraters high in carboo dioxid.e in the form of a soluble iron bicarbonate. The equations could be written:

l"e 2

o

3

+

3HzS ----::? FeS

+

}"es2

+

3H2

o

Ittes

₊

_HzCOJ

_----7

_Feao

3

+

HzS

1'

Feco3

+

_H2co3

----?1

Fe(Hco_{3) 2}

'I'

soluble in water in absence of air.

l'hese reactions locally are of importance, as organic matter does generate sulfide ions in considerable amounts and COz is also found under these conditions. · I t is doubt-ful, hov1ever, that these charged solutions could have diffused

through dense shales to any great extent. After all, solutions or gases travel the road of least resistance, which is, if possible, through sandstones and £!!:ound shale lenses. Any changes, however, from red to gray at contacts or in fissures of shales could, be explainect by such reactions. Proof for the movement of some kind of solution and diffusion is seen, for exar~le, at the li'rey 114 mine in I"rey Canyon, Utah. Here many small fissures may be observed in the silty shale >vhich forms the top of the l•!oenkopi and bottom of the 11 _{ore ohanne 1}11_•

The shale is reddish brovm except for a f'e'l'l millimeters on both sides of' fissures or joints itihere the color is light gray. The contacts are sharp. 'l'he discoloration along the fissures does not reach ('town into the Hoenkopi more than perhaps a f'oot. A little meta'corberni te vias found in these cracks.

As already mentioned there are vast masses of Chinle formation in the ar'8as under consideration which consist of alternating brownish red, gray and greenish gray beds of silts and shale. But there are also thick beds in which a mottling of red and gray occurs. In some places

the gray predominates and surrounds irregular bleb- to boulder-like masses of red. In others the color scheme is reversed. Except for color there is no other physical distinction discernable in the f'ielc1. 'l'his mottling has been observed in drill holes and mine drifts. 'l'herefore, it is

!lQ1

just an expression of i'leathering and oxidation. l,lany geologists may agree with the author that these

rock masses are so vast in scale that diagenetic processes more likely than not produced this variegated color pattern.

The color changes from red to gray in the Shinarump and top of the Moenkopi, however, had a different geolo-gical history, though chemically and mineralogeolo-gically they are closely related. The change from red to gray in the 11oenkopi at the contact with the Shinarump is ctefinitely

later than J,!oenkopi. Since· it parallels the channels 'Vihich the Shinarunm cut into the r4oenltopi it cannot be any older. Most geologists, including the writer,

associ-ate the color change vJi th the solutions that 1t1ere instrumental in concentrating U deposits. As these solutions, probably sulfate ones vihich may also have carried colloids of organic origin, were more widespread than the areas of present work-able uranium concentrations, the bleaching of the !v!oenlwpi contact reaches beyond these limits.

It is probable that in the Shinarump Conglomerate some of the gray lenses and irregular bodies, of shale and shaly silt so prominent in and near plant fossils and

uranium concentrations were changed from red. by the same kinds of sulfate solutions. Since the shales of the Shinarumv were associated with l'lant material from the

~ of deposition, a portion of them, hO'IJever, may have been gray from the start. Other1>fise, in many respects

these changes from red to gray should. be identical in origin to those in the !JI:orrison mineralogically described by vleeks \1951).

Mineralogical Changes

As tvas shovm by Weeks (1951) for the shales of the Morrison, the compositional changes are not very signifi-cant. '!here is no notetvorthy increase in ferrous iron in going from red to gray. In both shales FeO averages belotv one per cent.;< 'J!here is, however, more Fez03 in the red rocks than in the gray, on an average by a factor of 2. •rhe average of 8 red shales (\'leeks, p. 13) is

Fe203

=

3·39 and of the gray ones Fe203

=

1.67 per cent. :L'here are no other chemical differences that point to any particularly significant chemical reactions. Mineralogically all the shales under consideration, whether Triassic or

Jurassic, consist largely of hydro-micas, quartz, and a little carbonate. These hydro-micas contain considerable amounts of ~'e₂03 in their structures. The montmorillonite clay group is present, but its contribution may be small, albeit this is hard. to ascertain. Hematite is chiefly a coloring agent and very rarely appears as faint lines in x-ray diagrams. Pyrite is observed only in those gray shales -v;hich are associated with plant remains.

Processes F.esponsible for Color Changes

As there is no~Jhere any evidence that the gray shales might have been changed to red unless i t 111ere by 1-Jeathering >·;here they contained considerable iron carbonate or iron sulfide, the change ~ have proceeded from red to gray. It is believed by the majority of observers (Moultont 1926; Keller, 1929; Van Houten, 1948, P• 2120; \'leeks, 19511 that the change is causea. by the reduction of the ferric iron of hematite to ferrous compounds, though the amount of' such change would not have had to affect more than a fraction of the total iron present. ·

-'£his would probably be acceptable provided one over-looked those minerals of ferric iron ·which are not red.

1_{' Van Houten ( 1948, p. 2093) shov;s this also for other}

These have been listed, for example, by l4acCarthy (1926, P• 19). Glauconite, a hydro-mica structurally nearly

the same as illite, vihich makes UD the bulk of the shales,

is n'Ot"'redthough largely ferric." Illite itself contains consid.erable FezOJ, and nontronite, a member of the mont-morillonite group, is all ferric and d.ull greenish yello;1 as a rule. Another mineral commonly found in the shale areas is jarosite, K Fe3 ( S04) 2 ( OH)6, v1hich is ferric but yello1" in· color, It is associated with other sulfates like gypsum which are plentiful in the rocks under dis-cussion.

1'he only inorganic reducing material we might have in this environment :Ls some ferrous iron contained in pyrite or marcasite. But i t is perfectly obvious that

it can reduce hematite only by being itself oxidized, which is thermodynamically impossible. Rea.uction by organic pro-cesses, however, is not excluded and is one of two proposed below to explain the change from red to gray. In all pro-cesses, diffusion, v1hich is slow, v1ould have had to take over the role of flow of groundwater, as the shales are too dense for flow. Base exchange reactions would also have been important, as the shales are largely layer

struc-tures of silicates.

Inorganic assimilation of red .9.29:de. In the first process or mechanism proposed, only inorganic constituents ·would talte part, and UQ. reduction of the ferric iron 1-10Uld. occur. Instead,· the finely divided hematite would be dis-solved and the ferric ions incorporated into the silicates by base e-xchange or filling any vacant structural positions in the hydro-mica. ·A necessary assumption in this process is that sulfate,, or other highly ionized waters \·.ere the medium in which the reaction could take place. 'fhe grain boundaries in the shales offer enormous surfaces to inter-stitial solutions for specific ionic exchange reactions. Any so-called "primary" clay or mud. colored red by hematite

would have been in a metastable equilibrium if it had come in contact 'Hi th such solutions. '.Phe latter >-muld have be-come acidic because or ad.sorntion of cations like those of potassium by the clays and 'l'iould have slo1vly dissolved the otherviise almost insoluble red oxide. 'fhe ferric ions were .mad.e a part of the newly forming mica layers as fast as they

became available. 'l'he reaction proceeded to1rmrd the mica product because the hydro-mica is almost insoluble in acids and there was a large excess of those constituents necessary to shift the equilibrium in the direction of j.lli te. ifhere the shales are still red today there may be two or more reasons for this fact: First, and most important, there were· insuffi-cient amounts of sulf.ate solutions, and second, there v:as more