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Natural Radioactive Disequilibrium of the Uranium Series

GEOLOGICAL SURVEY BULLETIN 1084-A

This report concerns work done on behalf of the U. S. Atomic Energy Commission and is published with the permission of the Commission

Natural Radioactive Disequilibrium of the Uranium SeriesBy JOHN N. ROSHOLT, Jr.

CONTRIBUTIONS TO GEOCHEMISTRY

GEOLOGICAL SURVEY BULLETIN 1084-A

This report concerns work done on behalf of the U. S. Atomic Energy Commission and is published with the permission of the Commission

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON ~. 1959

UNITED STATES DEPARTMENT OF THE INTERIOR

FRED A. SEATON, Secretary

GEOLOGICAL SURVEY

Thomas B. Nolan, Director

The Geological Survey Library has cataloged this publication as follows:

Rosholt, John Nicholas, 1923-Natural radioactive disequilibrium of the uranium series.

Washington, U. S. Govt. Print. Off., 1959.

iii, 30 p. diagrs., tables. 25 cm. (U. S. Geological Survey. Bul letin 1084-A. Contributions to geochemistry)

Bibliography: p. 29-30.

1. Radioactivity. 2. Uranium. i. Title. (Series: U. S. Geo logical Survey. Bulletin 1084-A. Series: U. S. Geological Survey. Contributions to geochemistry)

553.493

For sale by the Superintendent of Documents, U. S. Government Printing Office Washington 25, D. C. - Price 15 cents (paper cover)

CONTENTS

PageAbstract_______________________________________________________ 1Introduction._____________________________________________________ 1Acknowledgments _________________________________________________ 4Method of measurement and definition of units______________________ 4Comparisons of equivalent uranium with uranium-__-_---------_--__-- 6Classification of disequilibrium patterns._____________________________ 7Some interpretations of causes of disequilibrium.______________________ 9Summary____________________________________________ 29References..-.____________________________________________________ 29

ILLUSTKATIONS

FIGUKE 1. Classification of natural radioisotopes into groups__________ 32. Anomalies in comparison of ell to U_______________________ 53. Types of disequilibrium classified by ratios of radioisotopes__ 84. Age of uranium deposition in years as a function of the ratios

ePa23» to U, eWo to U, and eRa"8 to U.._ ~-_~ ~_ 11

TABLES

TABLE 1. Age determination based on ratio of equivalent isotope touranium__________________________________________ 12

2. Uranium-series disequilibrium analyses.____________________ 14

m

CONTRIBUTIONS TO GEOCHEMISTRY

NATURAL RADIOACTIVE DISEQUILIBRIUM OF THE URANIUM SERIES

By JOHN N. ROSHOLT, JR.

ABSTRACT

Many radioactive samples show radioactive disequilibrium because of the numerous geochemical processes affecting ore deposits. As it is difficult to interpret disequilibria by simply comparing radiometric and chemical assay values of uranium, analyses should be made of the abundance of Pa231, Th230, Ra228, Rn222, and Pb«°.

Uranium-series disequilibria, as shown by radiochemical studies of samples representing a cross section of most of the significant present-day radioactive deposits in the United States, can be classified according to six basic types. Interpretations of the geochemical history of these types indicate that it may be possible to date uranium deposition within a theoretical range of 2,000 to 200,000 years. Ages ranging between 6,000 and 30,000 years have been calculated for several specific samples.

INTRODUCTION

In the greatly expanded search for uranium in the last 10 years, disequilibrium in radioactive ores has presented a difficult problem to geologists and prospectors. The magnitude and frequency of disequilibria have been generally underestimated, although the im portance of disequilibrium in field and laboratory counting measure ments has begun to be realized.

Very few complete studies concerning disequilibrium in radioactive deposits have been published. Variations in the protactinium: uranium ratio have been reported by Schumb, Evans, and Hastings (1939) and Wildish (1930). Ratios of Th230 to uranium in coral limestone have been reported by Barnes, Lang, and Potratz (1956). A few results of analyses of Ra226 and U in mine-dump material have been given by Phair and Levine (1953). T. W. Stern and L. R. Stieff (1959) have reported several analyses of Ra226 and U in carnotite ores. Kuroda (1955) has provided a number of ratios of Ra223 to Ra226 in high-grade uranium minerals. Urry (1948) has reported several analyses of varved-clay samples containing radium. Other reports primarily on radium isotopes have been written by Armburst

1

2 CONTRIBUTIONS TO GEOCHEMISTRY

and Kuroda (1956), Koczy (1954), and Chlopin and Vernadsky (1932).

The purposes of this paper are to tabulate and discuss the results of a number of complete analyses of disequilibrium samples, to illus trate a proposed classification of disequilibrium patterns, to study these patterns as clues to the understanding of the geochemical history of the samples and of the deposits, and to point out some of the difficulties when simply comparing radioactivity and chemical analyses of uranium for interpreting equilibrium or disequilibrium in samples.

To make a detailed investigation of the state of radioactive equi librium in ore-grade geologic samples, several key decay products must be measured and their relative abundances evaluated. Figure 1 shows the parent isotopes and decay or daughter products of the three principal naturally occurring radioactive decay series: the U238, U235, and Th232 series. Equilibrium is attained in a radioactive series when all the daughter products decay at the same rate that they are produced from the parent isotope. Thus, at equilibrium each of these daughter products would be present in a constant proportion to its parent isotope. The loss or gain, by geologic processes, of any of certain important isotopes during the more recent part of the existence of a mineral causes disequilibrium in the proportions of the parent isotope to its daughter products. Even though a series is not in complete equilibrium, many of the immediate short-lived daughter products will be in equilibrium with their long-lived parents. Where significant disruption of equilibrium occurs the natural radioisotopes can be separated into the following major isotopes and groups of established equilibrium shown in figure 1: the uranium group, Th230 isotope, Ra226 isotope, Rn222 group, Pb210 group, and Pa231 group in the uranium series. U235 itself will remain in constant abundance with U238 (Senftle and others, 1957); thus the U235 content is determined from the uranium analyses, which includes the isotopes U238, U235, and U234 which are assumed to be present in constant abundance to each other. In addition to these, the Th232 group may be present in some rocks and ores and add to the radioactivity.

To describe adequately the long-term state of equilibrium of the uranium series, the abundances of the long-lived isotopes, U, Pa231 , Th230, and Ra226 should be known. Analysis for Rn222 and Pb210 , as well as for uranium, is desirable for investigating radioactivity anomalies, for checking the accuracy of uranium and radioactivity analyses, and for investigating emanation properties. With the exception of a few important samples, the results on ores containing significant quantities of Th232 are not included in this paper. Radiochemical assays by the author are given in table 2 at the end of the paper.

RADIOACTIVE DISEQUILIBRIUM OF THE URANIUM SERIES 3

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ACKNOWLEDGMENTS

Practically all the later analyses, which include the determination for Pa231 , were made by using continuously operating automatic count ing systems for parts of the alpha-activity measurements. These sys tems were designed and maintained by J. R. Dooley, without whose assistance much of this work could not have been completed at this time. This work is part of a program being conducted by the U. S. Geological Survey on behalf of the Division of Raw Materials of the U. S. Atomic Energy Commission. A preliminary summary of this paper (Rosholt, 1957a) was presented at the Second Nuclear Engineer ing and Science Conference, Philadelphia, Pa., March 11-14, 1957.

METHOD OP MEASUREMENT AND DEFINITION OP UNITS

All the daughter-product analyses were made by alpha-particle measurements after radiochemical separations of the specific elements were made with the aid of inactive carriers. The abundance of the isotopes Pa231 , Th230 , Ra226, Rn222 , and Pb210 was determined. The methods used for these analyses have been described by Rosholt (1954; 1957b).

Equivalent uranium, expressed in percent ell, is the ratio of the radioactivity of the sample to the radioactivity of a uranium-ore standard which is in equilibrium with all of its decay products. Uranium is expressed as U, in percent, and Th232 as Th232, in percent. All the decay products are expressed in percent equivalent and thus do not represent the actual amounts of these daughter products. Percent equivalent is defined as the amount, in percent, of primary parent, under the assumption of radioactive equilibrium, required to support the amount of daughter product actually present in the sample. This amount of primary parent may or may not be present in the sample. For the Th232 series, the daughter products are calculated as equivalent to Th232 and not to U.

Some graphic examples of the definition of percent equivalent are shown in figure 2. The hypothetical sample in equilibrium is one showing 1 percent uranium, 1 percent eU, and 1 percent equivalent of all of the daughter products; that is, 1 percent ePa231, 1 percent eTh230, 1 percent eRa226, and so on. Sample 143 (Texas soil) has 0.65 percent U and 0.96 percent eTh230 . This eTh230 is present in excess of the uranium content and if equilibrium were to exist between U238 and Th230, then 0.96 percent U would be required in the sample.

RADIOACTIVE DISEQUILIBRIUM OF THE URANIUM SERIES

485002 59 2


Other units which could be used to express this type of result are compared below with the equivalent units. As can be seen, the use of equivalent units simplifies recording and interpreting the data.

Isotope

U238 plus U235Pa231Th230Ra22<>Rn222Pb2io

Percentequivalent

1.01.01.01.01.01.0

Percent

1. 03. 37X10-'1. 70X10-*3. 39X10-72. 15X10-124.28X10-"

10-' curiesgrams of sample

3.55. 16

3.393.393.393.39

The use of percent equivalent has other advantages besides that of illustrating or permitting direct comparison of uranium and daughter- product abundances in the sample. It also demonstrates that an overall material balance of parent isotopes and daughter products must exist in theoretical equilibrium concentrations, although not necessarily in the concentrations of parent and daughter products found in the samples selected for examination. Stated again, percent equivalent is defined as the amount, in percent, of primary parent, under the assumption of radioactive equilibrium, required to support the amount of daughter product actually present in the sample. This amount of parent does not necessarily have to be present in the disequilibrium sample; actually more or less than that amount of uranium may be present. Thus the deficient amount of uranium or the deficient amount of daughter product, in relation to its immediate parent, must exist elsewhere than in the sample analyzed. To illustrate this principle with sample 143 (fig. 2), 0.96 percent eTh230 shows that there is a deficiency of 0.96 0.65 or 0.31 percent uranium which must exist somewhere else unaccompanied by Th230 ; also, the sample is deficient of 0.76 0.24 or 0.52 percent eRn222 and 0.76 0.25 or 0.51 percent ePb210 which must exist elsewhere, unaccompanied by Ha226.

If a large enough sample is represented, the parent and all the daughter products will be present in equilibrium. However, this sample may have to be so large that it could not be collected. It also follows that the smaller the sample collected, the greater the proba bility of increasing the amount of disequilibrium found in the sample. This seldom considered assumption may be important in collecting samples.

COMPARISONS OF EQUIVALENT URANIUM WITHURANIUM

Although it is common practice to compare a sample's actual uranium content determined chemically with its equivalent uranium


(eU), misinterpretations can be made in comparing these two values alone. Radon loss is the most common anomaly and may present some misleading conclusions. Figure 2 shows some examples. Two Colorado Plateau samples (Nos. 68 and 69) in relatively good equi librium with the exception of some radon loss show eU:U ratios very similar to two other plateau samples (Nos. 22 and 24) which have a deficiency of Th230 and Ra226 together with a lesser radon loss. Thus the comparison of eU and U will not always indicate whether the sample is deficient in radon products alone or deficient in long-lived daughter products also. Some samples may even be deficient in uranium and still show a low eU:U ratio. Sample 143, of soil from Karnes County, Tex., illustrates this extreme case. The extremely high radon loss completely masks the presence of the long-lived daughters that are actually in amounts in excess of the uranium. The eU:U ratio would indicate major disequilibrium with deficient amounts of daughter products, whereas actually it is the amount of uranium that is deficient.

A routine eU analysis will not indicate the presence of low-energy alpha emitters when beta-emitting daughter products are not present in the sample. Sample 122, a marl from the Nebraska-South Dakota border, illustrates this phenomenon. The large excess of Th230 and Pa231 is not indicated at all by the eU value because of the much lower eRa226 and eRn222 content. Sample 1 (table 2) exhibits a somewhat similar isotope distribution with a large excess of Th230, but a lower excessive content of Pa231 . The eU analysis will not reveal the high Pa231 content which is evident in many samples, because of the lack of sufficient intensity of beta emission from this group.

In a routine eU analysis the radon loss may completely mask the additional radioactivity created by the presence of Th232 and its daughter products, as shown by two samples from Prince of Wales Island, Alaska. Only one is shown in figure 2, for they have very similar analyses; neither is listed in table 2 because they are primarily thorium ores, and complete disequilibrium analyses were not made on them. The eU:U ratio seems to indicate good uranium-series equilibrium, but actually the amount of Th232 and the percent equiva lent of its daughter products are greater than those in uranium. Equivalent Ra226 is also in excess of the uranium content.

CLASSIFICATION OF DISEQUILIBRIUM PATTERNS

Study of the isotope-abundance ratios of samples exhibiting signifi cant uranium-series disequilibrium shows that the various types seem to represent certain patterns. With the use of the analyses of the key isotopes U^+IJ235 , Pa231, Th230, and Ra226 it is proposed that practically all disequilibrium samples can be classified according to six

00

Equiv

ale

nt-

abundance

ra

tios

Da

ug

hte

r- p

roduct

d

eficie

ncy

Tim

e-r

ela

ted

daughte

r-pro

duct

defic

iency

O

O

FIG

URE

3. T

ypes

of d

iseq

uilib

rium

cla

ssifi

ed b

y ra

tios

of ra

dioi

soto

pes.


different types that can result from the most recent major process of alteration. The classification is shown in figure 3. The second column shows the number of samples that were analyzed and found to fall in each type; the equivalent-abundance ratios are the average values for the indicated number of samples. The first four rows of equivalent-abundance ratios, (types 0-3) show the comparison of equivalent daughter-product content to uranium content where the U:U ratio is automatically 1. The first row (type 0) represents the hypothetical sample of perfect equilibrium.

The first three types of disequilibrium have values of U in excess of eRa226 . Type 1, daughter-product deficiency, is represented by samples in which the generalized relationships are U^>ePa231!>eTh230!> eRa226 . Type 2, time-related daughter-product deficiency, is a very special kind of type 1 disequilibrium in which each of these daughter abundances must retain a specific relation with each other. This relation must be such that the amount of growth of each isotope from pure uranium, represented by the ratios of ePa231 to U, eTh230 to U, and eRa226 to U, would require the same interval of time. Type 3, Th230 deficiency, is represented by samples in which generally ePa231 5^U>eRa226!>eTh230, the key isotope being the anomalously low Th230 .

The last three types of disequilibrium have values of eRa226 in excess of U, and as the uranium content is so small, it and all the equivalent daughter-product abundances are compared to eRa226 instead of uranium, as in the first three categories. Type 4, daughter- product excess, is represented by a low uranium content. The remaining longer lived daughter products are often present in approx imately equilibrium amounts with one another. In some samples, however, the equivalent amounts of the daughter products vary con siderably from one to another. Type 5, Ra226 excess, as shown in dump material is a special case of type 4, daughter-product excess, where generally eRa226>ePa231>eTh230 which is much >U, the key isotope being the significantly excessive Ra226. Type 6, the occurrence of radium isotopes exclusively, is a peculiar and not too uncommon type of deposit in certain localities. Here Ra228, a daughter product of Th232, is commonly found with Ra226 . The radioactive components are radium isotopes and then- immediate decay products, and there is very little or no U, Th230, Pa231, or Th232.

SOME INTERPRETATIONS OF CAUSES OP DISEQUILIBRIUM

The study of the distribution of the radioactive decay products in the types of samples listed is still in its first stage; nevertheless it is


possible to explain, or at least to postulate, some of the causes of disequilibrium.

Two primary processes can be involved in the type 1 ores. Uranium may have migrated to its present location at a time less than that required by its daughter products to reach approximate equilibrium, that is, less than 300,000 years ago. The alternative is that there has been preferentially greater leaching of daughter products than of uranium. The latter explanation is the more probable in carnotite and other types of deposits where uranium fixative agents such as vanadium or phosphate are also present. Samples of this kind (type 1) that do not follow the normal U>ePa231>eTh230>eRa226 pattern (with eRa226 nearly equal to or only slightly less than eTh230) indicate that some leaching of daughter products has taken place. This kind of deficiency in daughter-product distribution is shown by samples 21, 23, 40, 60, 62, 74, 81, 86, 87, 93, 104, 108, 112, 121, 142, and 144 (table 2). Ra226 has been found to be the most common, and, in most samples of this type, the only long-lived daughter product which can be leached. Deficiencies of Rn222 and Pb210 are not considered major causes of long-lived disequilibrium. When the isotope abundance is similar to that in type 2, considerable weight is thrown to the first explanation (recent deposition of uranium). This distribution is common in many of the pitchblende-type ores such as that at the Happy Jack mine. Samples 20, 22, 24, 35, 45, 47, 52, 57, 60, 61, 62, 73, 86, 87, 104, 107, 118, and 142 may represent this kind of alteration. Some of the samples may represent more recent uranium deposition than is indicated by the abundance of the isotopes (see fig. 4). That is, they may actually be type 2 material that was deposited where some older uranium minerals already existed, or uranium may have subsequently been leached out after the original, relatively recent, uranium deposition. Samples 60, 62, 86, 87, 104, and 142 could result from the combined effect of recent uranium deposition and leach ing of Ra236.

Type 2 ores are of special significance because the isotope abun dances are such that each isotope indicates nearly the same age for the uranium deposition. The required isotope abundances must match the time intervals when compared to figure 4. For the results of testing of these samples actually to represent the age of the ura nium mineral, three conditions must be met: (a) uranium free of all decay products must have been deposited in nearly nonradioactive host rock, (b) there must have been no significant leaching of uranium or long-lived daughter products after deposition, and (c) the rate of deposition must not have been too slow compared to the rate of growth of daughter products. Evaluation of the effect of some of these conditions has been made (Rosholt, 1958). Table 1 shows the

RADIOACTIVE DISEQUILIBRIUM OP THE URANIUM SERIES 11


isotope ratios and the possible age of the uranium for all the samples represented by this category. Some anthropological evidence and carbon-14 measurements (Wendorf, Krieger, and Albritton, 1955) for the same stratigraphic location from which sample 141 was obtained support the premise that the age given in table 1 is of the correct order of magnitude. Type 2 disequilibrium is not very common, but increasing knowledge of favorable geochemical and geological en vironments is now providing a greater probability of locating ores of type 2 disequilibrium. Eadiochemical data and field evidence are now being accumulated for a paper devoted primarily to geochemical interpretations based on this kind of disequilibrium.

TABLE 1. Age determination based on ratio of equivalent isotope to uranium

Sample No. 1

13 14... _ 38. _ 39 53 64 _ .55-. - 66-.. 68 141

Isotope ratio

ePa2«U

0.24 .39 .10 .088 .27 .10 .45 .25 .37 .33

eTh^o ~U~

0.13 .26 .053 .022 .15 .045 .18 .15 .26 .18

eRa2*i» U

0.13 .27 .053 .021 .13 .034 .16 .10 .22 .10

Age (years) on the basis of

Pa23i

14,000 25,000 5,000 4,500

16,000 5,000

30,000 14,000 23,000 20,000

Thzso

16,000 35,000 6,000 2,500

18,000 5,000

23,000 19,000 35,000 23,000

Ra^»

18,000 38,000 9,000 4,500

18,000 6,000

22,000 15,000 31,000 15,000

' See table 2 for description of sample.

Type 3 disequilibrium is believed to be the result of rather recent deposition of uranium contaminated with significant amounts of daughter products other than Th230 , and with silica and salts. This type of disequilibrium is often the result of evaporation of solutions containing some of the long-lived isotopes, along with silica and vari ous salts. The low Th230 content must reflect the relative deficiency of this isotope in the solutions. Sample 67, a hyalite-opal, appears to have this mode of origin. Samples 78, 79, and 80, stratigraphically below three samples (75, 76, and 77) of other classes, are most prob ably of this mode of origin (R. G. Coleman, oral communication).

Many samples with anomalously high radioactivity are of type 4. In general, disequilibrium of this type, found in samples taken from an oxidized environment, is the result of leaching of uranium. Daugh ter products may possibly have been added to the host rock, but it is difficult to select samples definitely showing that this occurred. A few samples (4, 36, 37, 42, and 82) have an abnormally low eTh230 content, which may indicate daughter-product addition when one considers that type 3 samples also have a low eTh230 content. A few samples (1, 46, 49, 71, and 72) have a low ePa231 content which may have resulted because sufficient time was available for a greater frac-


tion of Pa231 than Th230 to decay after the uranium was leached. The fact that there is little eRa226 in many samples of this type does not appear to be too significant, for radium is easily leached in many different environments.

One very significant anomaly present in many samples of type 4, especially some of the high-grade black uranium minerals, is the high Pa231 content and near equilibrium abundances of U, Th230, and Ra226 . Samples 41, 59, 61, 65, 66, 68, 69, 89, and 144 show this anomaly. One explanation seems most plausible uranium and the other decay products are preferentially leached to a greater degree than protac tinium. This may be due to the greater ability of protactinium to become hydrolized and reprecipitated immediately from the leaching solutions (Elson, 1954). Additional possible evidence of this high Pa231 content in many uranium minerals is furnished by Kuroda (1955). The high ratios of Ra223 to Ra226 that are characteristic of many of the uranium minerals he analyzed may reflect a high Pa231 content.

Most of the samples represented by type 5 disequilibrium occur in pyritic ores or ore dumps and are the result of differential leaching of all components. Sulfates formed in these materials would retain the radium even though it might migrate somewhat, whereas the sul- furic acid formed would leach and remove uranium. Further dis cussion of this type of disequilibrium is presented by Phair and Levine (1953).

The occurrences of radium isotopes exclusively (type 6 disequi librium) are commonly associated with oil- and gas-field brines. Radioactive hot-spring deposits also show this type of disequilibrium. These sometimes highly radioactive deposits are the result of copre- cipitation of radium with barium sulfate, strontium sulfate, and occasionally iron hydroxide from large volumes of water. It is also believed that the reason for the deposition of radium isotopes, essen tially free of other radioactive isotopes, is that the water contained only radium as a significant radioactive component. The radium is believed to come from the pore space of the country rock from which the water is flushed. Materials containing significant amounts of Ra228 (without Th232) must be of very recent origin, less than 30 or 35 years old. Samples 28, 127, 129, and 133-140 are of materials with recent additions of radium. Further evidence that many of these materials are of recent origin is the low Pb210 content. Sample 128 is a drill cutting from a depth of 2,530 feet and was obtained from rock below a well which was first drilled approximately 25 years ago (A. P. Pierce, oral communication). The well was deepened recently when the sample was collected. The ratio of Pb210 to Ra226 yields an age of 24 years. Further work describing many of the other aspects of oil-field radioactivity is presented by Gott and Hill (1953).

485002 59 3

TAB

LE 2

. U

rani

um-s

erie

s di

sequ

ilib

rium

ana

lyse

s ar

rang

ed b

y ge

ogra

phic

al l

ocat

ion

of t

he s

ampl

es

Sam

ple

num

ber:

Sam

ples

col

lect

ed o

r su

bmit

ted

by t

he f

ollo

win

g:

(U.

S. G

eolo

gica

l Su

rvey

unl

ess

othe

rwis

e in

dica

ted)

: E

. R

. L

andi

s, 1

; R

. U

. K

ing,

3-5

; F.

B.

Moo

re,

6-S;

B.

F.

Leo

nard

, 9,1

0; A

very

Dra

ke,

11,1

2; E

. W

. G

rutt

, Jr.

, AE

C,

13,1

4, 8

1-83

, 87

, 89

, 91

, 93

-98,

119

; C

. T

. Pi

erso

n, 1

8, 1

9; R

. A

. L

avor

ty,

AE

C,

20, 2

1, 9

9; C

. M

. T

scha

nz.

27, 2

9-32

; Hel

en C

anno

n, 2

8; R

. D

L

ynn,

Ana

cond

a C

oppe

r C

o.,

33, 3

4; S

. R

. A

usti

n, A

EC

, 35

-42;

H.

G.

Stev

ens,

43;

R.

T.

Che

w a

nd A

. F

. T

rite

s, 4

4-66

; R

. G

. L

ewis

, 67

;A

. J.

Froe

lich,

70;

W. J

. C

arr,

71,

72;

H.

E. N

elso

n, 7

3, 7

4; R

. G

. C

olem

an, 7

5-80

; J.

G. S

teve

ns,

AE

C,

84-8

6; D

. F

. D

avid

son,

88,

90;

W.

N.

Shar

p, 9

2; W

. J.

Map

el,

100;

P.

L;

Wei

s, 1

01;

J. R

. G

ill,

104,

117

, 11

8, 1

20;

D.

E.

Peac

ock,

105

, 10

6; E

. G

. E

thim

ou,

107;

G.

B.

Got

t, 10

8,11

4-11

6; E

. V

Po

st,

109;

R.

S. J

ones

, 11

0-11

3; R

. J.

Dun

ham

, 12

1-12

4,F.

W.

Stea

d, 1

25; A

. P

. Pi

erce

, 128

-130

, 13

2-13

6; J

. W

. Hill

, 13

1; R

. T

. R

usse

ll, A

EC

, 13

7,13

8; H

. J.

Hyd

en,

139;

D.

H.

Ear

gle,

141

; F.

C.

Can

ney,

142

; and

P.

F. F

ix,

143-

145.

et

T (p

erce

nt):

The

equ

ival

ent u

rani

um (

eU)

assa

ys w

ere

perf

orm

ed b

y C

. G

. A

ngel

o, S

. P

. F

urm

an,

and

D.

L.

Scha

efer

, U

. S.

Geo

logi

cal

Surv

ey.

U (

perc

ent)

: T

he u

rani

um a

naly

ses

wer

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rfor

med

by

staf

f m

embe

rs o

f the

U.

S. G

eolo

gica

l Su

rvey

. P

a831

(per

cent

equ

ival

ent)

: P

a2'1

was

not

det

erm

ined

in

the

earl

y an

alys

es.

Sam

ple

No.

Lab

orat

ory

No.

Fie

ld N

o.D

escr

iptio

n an

d lo

catio

nD

is

equi

lib

ri

um

type

Per

cent

eUU

Th»

2

Per

cent

equ

ival

ent

Pa23

iT

h230

Ha

Rn22

2Pb

2">

Ha*

"

CO

LO

RA

DO

B

ent

Cou

nty

2250

91L

CR

-12

6fr

om s

ands

tone

rid

ge i

n va

lley

subj

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toco

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le w

eath

erin

g, s

ec. 3

2, T

. 27

S.,

R.

51 W

.

41.

40.

057

1.9

5.5

3.9

2.6

1.93

Las

Ani

mas

Cou

nty

223

9443

F 4

3770

ferr

ugin

ous

and

man

gano

us

subs

tanc

e;

Clif

f M

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ump sample of vein material showing tel- luride and radioactive material in altered

monzonite. X-ray mine,

ample of shear-zone quartz vein, 320 ft from portal. Host rock in mine is Ter tiary monzonite. Shirley mine, NWM,

sec. 19, T. 1 S., R. 73 W. 1^-ft.

ne-ft sample of shear-zone quartz vein,

480 ft from portal. Shirley mine,

hip channel of 6-in. vein material in Gold

Hill mining area,

^lected pieces of most radioactive material,

same location as No. 9.

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ne-fourth-inch pitchblende veinlet in foot- wall at level 6, east, 424 ft from shaft, Old Town mine,Central City district. Mine

drains through level 22 of Argo tunnel. Abundant pyrite has produced highly

sulfate acid waters,

ne-fourth-inch sample of pitchblende veinlet which extends 4 in. along dip length between hanging wall and foot- wall branches at shaft 20 ft above level 7.

Old Town mine.

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edium-grained dark-green to buff sand stone with abundant limonite specks from Browns Park formation at 80- to 82- ft depth of drill hole 5470-3020, Gertrude

claims, sec. 17, T. 7 N., R. 94 W.

ssentially same type of rock as no. 13, 82-

to 84-ft depth, drill hole 5470-3020.

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SULFIDE ZONE ContinuedChip sample, altered lower sandstone; near floor at station 0, 15 ft south of station M.

Chip sample, lower siltstone; near floor at

station P, 70 ft south of station O.

Chip sample, pitchblende lens; between sandstone beds, north wall at station R,

25 ft west of station P.

Thin-bedded siltstone; abundant jarosite and limonite along fractures; 1.2-ft chan nel nearest floor of station V, 140 ft south

of station R.

Pitchblende seam at base of gray siltstone bed; grab sample near floor of station BQ,

50 ft south of station R.

Silty sandstone highly impregnated and replaced by yellow sulfides; 0.2-ft chan nel, 2.7 ft above floor at station 9, 310 ft

south of station BQ.

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Hyalite opal in sandstone from near base of Shinarump member of the Chinle formation; 10 ft from ore at Skyline mine, Monument Valley NWM, sec. 26, T. 43

S., R. 15 E., Salt Lake meridian.

Uranium-bearing sandstone from Deer

Flat,

.--.do... . ......._....-...-. .......... Mineralized carbonaceous material from

Hideout mine.

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RADIOACTIVE DISEQUILIBRIUM OP THE URANIUM SERIES 23

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Grab sample from ore zone in surface work ings; carnotite-type mineral in white sandstone host rock in Lakota sandstone; Damsite no. 1 claim, sec. 8, T. 8 S., R.

4E.

Sandstone with carnotite; Gould mine. sec.

12, T. 8 S., R. 3 E.

Radioactive barite _ ... .-.._ .... Ore pod in sandstone; sec. 11, T. 8 S., R.

3E.

Reaction zone around ore pod; same loca

tion as sample no. 110.

Clay; sec. 11, T. 8 S., R. 3 E.-. .... . Contact between clay and adjacent sand stone: same location as sample no. 112. Radioactive sandstone from Fall River

sandstone; light fraction; Red Canyon

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Heavy fraction of same sandstone as sample

no. 114.

Opal concentrate from light fraction of same

sandstone as sample no. 114.

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enclosed in basal part of weathered yellow shale, Niobrara formation, SEH, sec. 28,

T. 36 N., R. 46 W.


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Banded vesicular limestone, Arbuckle group; 2,529- to 2,530-ft depth, Magnolia-

Anderson no. 7, Augusta Field.

Dense vesicular limestone, Kansas City group; 2,027- to 2,037-ft depth; South

Anderson no. 1, Augusta Field.

Pipe scale from gas-well pipeline, Simpson formation SWH sec. 27, T. 9 S., R. 4 E. Scale collected from scrap pipe... __ ~ _

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Filter cake from no. 2 tank, Cities Service,

Avant Unit.

Sulfate scale from water trough, Avant 1-S

well.

Ferrifloc from waste-water pit, Avant Unit- Fresh scale from outlet valve on Avant

Unit 1-S well.

Freshly precipitated ferrifloc from lime-

ferrifloc precipitate, Avant Unit.

Sand used for road ballast, previously used for oil-field filter sand, sec. 24, T. 24 N.,

R. 11 E.

Concretionary limonite and BaSO« from salt-water drainage ditch grading from

New Boston Pool.

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TAB

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s di

sequ

ilib

rium

ana

lyse

s ar

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y ge

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phic

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ple

s C

onti

nued

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Mid

land

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nty

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to 00

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ple

No.

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ory

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d N

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catio

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is

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rium

ty

pe

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ent

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0.01

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0.00

230.

001

3i

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006

142

143

144

145

GX

-56-

45

GX

-55-

1258

GX

-55-

1272

GX

-55-

1277

56-1

PF

F-5

5-11

PF

F-5

5-23

PF

F-5

5-30

ium

min

eral

s; n

orth

tre

nch,

sou

th L

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or

e bo

dy.

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dire

ctly

ove

r sa

mpl

e 14

5, D

r.

Boz

ole

ase.

Mar

vin

Hac

bene

y ra

nch,

nor

thea

st

base

of T

ordi

lla H

ill.

Bla

ck s

ands

tone

; Dr.

Boz

o le

ase;

sou

thw

est

of n

os.

143

and

145.

leas

e.

1 4

lor

4 1

1.9 .41

.29

1.4

4.35 .65

.57

1.93

3.20 .66

.71

1.87

2.77 .96

.55

1.58

0.49 .76

.47

1.70

0.29 .24

.11

.97

0.33 .25

.10

.76

Duv

al C

ount

y

14fi

147

2280

87

2280

88

F-11

262

F-11

263

Whi

te

fria

ble

tuff

, C

ontin

enta

l O

il C

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ase.

One

-foo

t ch

anne

l in

car

bona

ceou

s lig

nitic

mat

eria

l; A

rans

as E

xplo

ratio

n le

ase,

nor

th

Duv

al C

ount

y.

Sam

ple

is fr

om D

ubos

em

embe

r of

Jac

kson

for

mat

ion,

ove

rlies

med

ium

to f

ine-

grai

ned

fria

ble

sand

ston

e.E

adio

activ

ity o

ccur

s in

low

er 6

in

to 1

ft

of li

gnite

mat

eria

l whe

rp it

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rlies

hig

hly

silic

ified

por

tion

of n

orm

ally

fria

ble

sand

st

one.

4 4

.062

.26

0.05

1

.075

1.9 .55

2.5 .62

1.5 .47

0.82 .32

1.0 .37

i Ind

epen

dent

Ea«

« an

alys

is p

erfo

rmed

by

J. R

. D

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y an

d D

. L.

Scha

efer

usi

ng th

e ra

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trai

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ery

low

.3 I

nsuf

fici

ent s

ampl

e,

KADIOACTIVE DISEQUILIBRIUM OF THE URANIUM SERIES 29

SUMMARY

Radioactive disequilibrium is a fairly complex phenomenon, and it is not an easy task to provide simple and straightforward explanations for the various daughter-product abundances. An approach through multiple hypotheses whose possible acceptance or rejection will be based on further interpretations provided by geological, geochemical, and chemical evidence will undoubtedly be necessary. The initial goal of this study was to investigate the complexity of disequilibrium and the distribution of its types. Unfortunately many of the early samples that were analyzed did not have adequate enough descriptions to permit more detailed interpretations.

Some of the many possible explanations of the causes of disequilib rium have been presented here although some of these may have to be revised when further evidence is available. Even without accept ance of an hypothesis, radioactive-disequilibrium studies provide important clues to the geological and geochemical history of deposits.

REFERENCES

Armburst, B. F., Jr., and Kuroda, P. K., 1956, On the isotopic constitution ofradium (Ra224/Ra228 and Ra228/Ra226) in petroleum brines: Am. Geophys.Union Trans., v. 37, no. 2, p. 216-220.

Barnes, J. W., Lang, E. J., and Potratz, H. A., 1956, Ratio of ionium to uraniumin coral limestone: Science, v. 124, p. 175-176.

Chlopin, U. G., and Vernadsky, V. I., 1932, Radium-und mesothoriumbaltigenaturliche gewasser [Radium and mesothorium content in natural waters]:Zeitschr. Elektrochemie, Band 38, nr. 8a, p. 528-530.

Bison, R. E., 1954, The chemistry of protactinum, in Seaborg, G. T., and Katz,J. J., eds., The actinide elements (Natl. Nuclear Energy Ser., Div. IV, v.14A): New York, McGraw-Hill Book Co., p. 117.

Gott, G. B., and Hill, J. W., 1953, Radioactivity in some oil fields of southeasternKansas: U. S. Geol. Survey Bull. 988-E, p. 69-122.

Koczy, F. F., 1954, Geochemical balance in the hydrosphere, in Faul, Henry, ed.,Nuclear geology: New York, John Wiley and Sons, Inc., p. 120-127.

Kuroda, P. K., 1955, On the isotopic constitution of radium (Ra^/Ra229) inuranium minerals and recent problems of geochronology: New York Acad.Sci. Annals, v. 62, art. 8, p. 177-208.

Phair, George, and Levine, Harry, 1953, Notes on the differential leaching ofuranium, radium, and lead from pitchblende in H2SO4 solutions: Econ.Geology, v. 48, p. 358-369.

Rosholt, J. N., Jr., 1954, Quantitative radiochemical method for the determinationof major sources of natural radioactivity in ores and minerals: Anal. Chem istry, v. 26, p. 1307-1311.

1957a, Patterns of disequilibrium in radioactive ores, in Dunning, J. R., and Prentice, B. R., eds., Advances in nuclear engineering, v. II, pt. 2: New York, Pergamon Press, p. 300-304.

1957b, Quantitative radiochemical methods for the determination of thesources of natural radioactivity: Anal. Chemistry, v. 29, p. 1398-1408.


Rosholt, J. N., Jr., 1958, Radioactive disequilibrium studies as an aid in under standing the natural migration of uranium and its decay products: United Nations Internat. Conf. on the Peaceful Uses of Atomic Energy, 2d, Geneva, 1958, Proc., paper QIC 183, U. N. 772.

Schumb, W. C., Evans, R. D., and Hastings, J. L., 1939, The radioactive deter mination of protactinium in siliceous terrestrial and meteroric material: Am. Chem. Soc. Jour., v. 61, p. 3451-3455.

Senftle, F. E., Stieff, Lorin, Cuttitta, Frank, and Kuroda, P. K., 1957, Comparison of the isotopic abundance of U235 and U238 and the radium activity ratios in Colorado Plateau uranium ores: Geochimica et Cosmochimica Acta, v. 11, no. 3, p. 189-193.

Stern, T. W., and Stieff, L. R., 1959, Radium-uranium equilibrium and radium- uranium ages of some Colorado Plateau secondary minerals, in Garrels, R. M., and Larsen, E. P., 3d (compilers), Geochemistry and mineralogy of the Colorado Plateau uranium ores: U. S. Geol. Survey Prof. Paper 320.

Trites, A. F., Jr., and Chew, R. T., 1955, Geology of the Happy Jack mine, White Canyon area, San Juan County, Utah: U. S. Geol. Survey Bull. 1009-H, p. 238.

Urry, W. D., 1948, The radium content of varved clay and a possible age of the Hartford, Connecticut, deposits: Am. Jour. Sci., v. 246, p. 689-700.

Wendorf, Fred, Krieger, A. D., and Albritton, C. C., 1955, The midland discovery, a report on the Pleistocene human remains from Midland, Texas, with a description of the skull by T. D. Stewart: Austin, Texas, Univ. of Texas Press, 139 p.

Wildish, J. E., 1930, The origin of protactinium: Am. Chem. Soc. Jour., v. 52, p. 163-177.

O