•'OO•,NALO• GEO•'IIYSlCAL
RESXAaCX
VOL. ?4, NO. IS, JULY IS, 1969
IsotopicAnalysesof Barium in Meteorites
and in Terrestrial Samples
O. EUGSTER,
F. TERA,ANDG. J. WASSERBURG
Charles Arms Laboratory o• the Division o• Geological Sciences
Cali•Jrnia Institute o• Technology,Pasadena,California 91109
Isotopic compos•tien and concentration of barium in six stone meteorites and the silicate
inclusionsof two iron meteorites and three terrestrial sampleswere measuredby use of a
'double spike' isotopic dilution technique in order to correct for laboratory fractionation. Any
differencesbetween the abundancesof the isotopesin meteoritic and terrestrial Ba were found
to be less than 0.1% for all isotopes.The per cent abundancesof Ba found in our work for
Ba'•s, Ba•, Ba•% Ba'•, BaTM,Ba•', and Ba'•ø are 71.699, 11.232, 7.853, 6.592, 2.417, 0.1012, and
0.1058, respectively. Because of the higher precision, these abundancesshould replace the
currently acceptedvalues. These results show the variations in the Ba isotopesreported by
S. Umemoto (1962) to be unsubstantiated.
Umemoto [1962] reported that the isotopic
composition
of Ba in the Bruderheimchondrite
INTRODUCTION
A comparison.of the isotopiccompositionof
various elementsin terrestrial samples,me-
and in the Pasamonte and Nuevo Laredo
achondrites were distinct from terrestrial Ba
teorites, and other materials of the solar system
is of fundamental importance in determin- and showeda pattern of uniform fractionation
relative to terrestrial Ba. The enrichments obing the early history of the solar system
served
by him correspondto a 2% enrichment
and the mechanismsof nucleosynthesis.
In adin
the
ratio Ba•ø/Ba• compared with terdition to effectsthat are a product of either
restrial
materials. Previously, Krummenacher
long-lived natural activity or cosmic-rayinteraction with meteoriticmaterial, isotopicabun- et al. [1962] found no anomaliesgreater than
dancesmay be distinct from terrestrial material 3% for the isotopesBa•'-• in the Richardton
becauseof isotopicfractionation or incomplete
isotopic homogenizationduring the formation
of the solar system. The only major variation
in isotopicabundancesobservedbetween terrestrial and meteoritic samples that is not
causedby nuclearprocesses
is found in the rare
gasesneon [Pepin, 1967], krypton [Eugster et
al., 1967], and xenon [Reynolds, 1960a]. The
only apparent exceptionsto the constancyof
the isotopicabundances,
with the exceptionof
the rare gases, are the elements lithium and
barium. Investigationsof lithium by Gradsztajn
et al. [1967] suggestthat there is a variation
of the abundance of lithium
in stone meteorites
of about 10%. These data have not yet been
confirmedby work in other laboratories.
x Contribution
1606 of the California
Institute
of Technology.
Copyright ¸
1969 by the American GeophysicalUnion.
chondrite.
Since the
established fractionation
patterns for Xe and the suggested
fractionation
of Ba reported by Umemoto were in the
same direction, it was of great interest to confirm or disprove the reality of this reported
effect. The mechanisms for fractionation
that
have been proposedfor Xe and Kr are far
from satisfactory,and it was conceivablethat
someunknownmechanismmight have also operated in fractionating the Ba isotopes.The
magnitude of the fractionation proposedby
Umemoto was significantly smaller than that
found for Xe, which is approximately4% per
massunit, whereasfor Ba Umemoto indicated
an effect of 0.25% per mass unit. It is well
known that isotopic fractionationmay be inducedduring massspectrometricanalysis,and
great care must be taken to avoid the production of this type of anomaly by laboratory
procedures.This is made quite evident by the
work of Wetherill [1964] on molybdenum,who
demonstrated that the variations in molyb-
3897
EUGSTER, TERA, AND WASSERBURG
3898
TABLE 1. Isotopic Composition of the Double Spike
Atom per cent abundances.
697
060
867
150
387
064
89.457
4-.070
1.646
4-.025
74.555
4-.058
0.660
4-.006
1.789
4-.018
0.8515
4-.0059
0.1290
4-.0030
4.080
4-.020
0.7995
4-.0040
0.0543
4-.0010
84.572
4-.200
14.398
4-.034
0.00119
4-.00005
0.0351
4-.0004
0.00695
4-.00008
0.00070
4-.00005
0.0115
4-.0003
0.00253
4-.00007
9.338
4-. 004
74.598
0.8500
4-. 0014
0.7967
4-. 0014
14.407
0.00690
4-. 00007
0.00251
4-. 00006
39.403
4-.010
44.020
4-.010
4. 2322
4-.0010
3.5990
4-.0010
8.641
4-.010
0.05260
4-. 00005
0.05270
4-. 00005
1. Enriched Ba•37,measured
2. Enriched BaTM,measured
3. Calculated compositionof
double spike based on com-
positions
of I and'2andon
the amounts
of Ba taken
from
the two salts *•
4. Measured compositionof
double spike, normalized to
Ba'37/BaTM = 5.178
5. Typical compositionof a
mixture of double spike plus
sample, not corrected for
fractionation (Nuevo Laredo)
Notes.
For I and 2 the total errors are basedon the errors for the uncertainty of the fractionation and on the
statistical errors. The total error equals [•i (ai)2]•t•..For 3 the errors are based on the errors of I and 2.
For 4 and 5 statistical
errors are shown.
* For the double spike the ratio of the total number of Ba atoms contributed by the enriched Baxs•
salt to the total number of Ba atoms contributed by the enriched BaTMsalt was 4.8929 as calculated from
the gravimetric data and from the atomic weights of the enriched Ba which was based on I and 2,
respectively.
denumisotopicabundances
reportedby Murthy
[1962, 1963, 1964] were most likely due to instrumental fractionation. In this light, the isotopic variations of Mo in terrestrial ore samples reported by Crouch and Tuplin [1964]
appear very doubtful. These authors seem to
be unaware
of the other work in this field and
the instrumentalproblemsthat invariably exist.
Chakraburtty et al. [1964] reportedthat no enrichment of Ag•ø•was found in seven iron meteorites, including Canyon Diablo for which an
anomalywas reportedby Murthy [1960], which
was most likely the effect of instrumental fractionation.
It is known [Shields,1966] that isotopicfracrionation effects can be minimized by very
standard operational procedures during analysis. It was deemed advisable, however, to
utilize a more reliable techniquesuch as an internal isotopic standard of two isotopes.This
technique,often called the double spiking technique, was recently used by Wetherill [1964]
in his study on molybdenum.To distinguishbetween laboratory effectscausedeither by chemistry or massspectrometry,an isotopicinternal
standard or double spike was added to the samples beforethe chemicalseparation.
EXPERIMENTAL
PROCEDURE
Chemical treatment. A 0.2- to 5-gram sample was mechanicallycleanedwith a dental burr
to remove any surface contamination,washed
with acetone,dried in an oven, and, after grinding and splitting, weighedinto a 100-ml teflon
beaker. The sample was dissolved in HC10,
and HF, 5 ml of each acid per gram solid sample, evaporated to dryness,and redissolvedin
2.5 N HC1. An aliquot correspondingto about
0.2 gram of solid samplewas taken, evaporated
to dryness,and then brought into solution in
2 ml of 2 N HC1 which was loaded onto a cat-
ion exchangecolumn (1 cm X 15 cm, packed
with Dowex 50 X 8, 200-400 mesh). After most
of the
other
elements
were
removed
with
4
column volumes of 4 N HC1, the barium was
collected in the following fraction of about 2
column volumes of 4 N HC1.
Blank determinations
showed that the barium
contamination introduced by the complete
chemical processingwas less than 5 X 10-g
gram. This blank contribution to the sample
was always less than 2%, which is negligible
insofaras the isotopicratios are concerned.The
Ba concentrationswere, however,correctedfor
this small blank.
ISOTOPIC
ANALYSES
Mass spectrometry. The sampleof approximately 10-6 gram barium was depositedas the
chlorideand analyzedby meansof the singlefilament (Ta) surfaceionization technique.A
single-focusing,
30.48-cmradius,60ø sectortype,
programmable
magneticfield massspectrometer
with digital output and with on-linedata processing[Wasserburg
ei al., 1968,1969] wasused
for most analyses.Some of the unspikedsamples were analyzedwith the samemassspectrometer by usinga recorderfor analogoutput.
The mass spectrometricdata were taken in
sets of ten completesweepsof the spectrum.
Becauseof the programmable
magneticfield device and the on-linedata processing,
one set of
data for all isotopes
includingzeroson eachside
of every peak couldbe taken within about 10
minutes. Systematicchangesin the isotopic
ratiosduringthis time werelessthan 2 parts in
OF BARIUM
3899
positionwas as shownin Table 1 for a typical
compositionof a mixture of doublespike plus
sample.The Ba•/Ba •85ratios were always be.:
tween 11 and 14. These ratios have been cor-
rected for the massspectrometerfractionation,
which was basedon the ratio Ba•/Ba •85.For all
four samplesthis ratio was between 1.17 and
1.18. Figure I showsthe variation of the ratio
Ba•37/Ba
• as a function of the Ba•7 ion current normalized to the value of this ratio obtained at about 0.4 volt. Below 12 volts the
104 for all ratios. We therefore assume the frac-
input resistor can be consideredto be linear
within 0.1%. In a few casesin which data were
taken at intensities over 12 volts, corrections
were applied for the nonlinearity.
Because of the wide range (up to 103) in
ion currents of the different isotopes,it was
necessaryto eliminate errors causedby the incomplete dischargeof the high input resistor
and the amplifier system. Time intervals be-
tionation during each set to be constant.One
tween data acquisition were established by
analysisof a doublespikedsampleconsisted
of
making a time study of normal potassium,so
six to ten sets taken at different intensities
that any errors due to these sourceswere less
than I part in 104for all isotopes.This effect
volts for Ba• with a 10•-ohm input res;stor. was also minimizedby a scanningsequencein
The linearity of this resistorwasexaminedcare- which a high-abundanceisotope did not imfully up to 42 volts.Four differentsamples
were mediately precedea rare isotopein the detector.
used for this examination. Their isotopic corn- In the chosenscanningsequenceBaTMusually
rangingin most casesfrom about 0.5 to 12
q
4.002
4DO0
0.998
0.996
_
0.994
_ q:[Ba5'Ba35]/[Ba3Ba35]at,,,O.4
Volt
0.992
I
o.5
I
I
I
2
5
!
I
20
,/
50
VOLTSBa157
IONCURRENTBa137(10
-IAMPS)
Fig. l. Voltagedependence
q of the 10S-ohm
resistorusedas • functionof ion current.
The B•=7/B•• r•tios are corrected
for changes
in fraction•tion.Eachpoint represents
the
mean of • set of ten r•tios. Errors shown are the mean deviations.
3900
EUGSTER, TERA, AND WASSERBURG
followed Ba•". This sequencerepresentedthe
greatest differencebetween a high- and lowintensity isotope.The ratio Ba•/Ba •8' was always about 68. The isotopeBa•" was measured
twice successively,integrating both times at
least 12 seconds(includingthe zero lines). So
we were able to detect any possibleerrors due
to incompletedischargeof the input system.
DOUBLE SPIKE
Highly enriched and precisely weighed
Ba•'(N08),. and Ba•'(N08),. obtainedfrom Oak
Ridge were used to prepare standard solutions
of BaTMand Ba• in 2.5 N HC1. The isotopic
compositionof these two solutions were determined and are given in Table 1. The data as
tabulated are uncorrectedfor massspectrometer
spike and analyzed.The fractionation was de-
terminedfor this analysisby the doublespike
techniqueas described
below.The isotopiccompositionof the doublespike was as given in
Table 1 (measuredcomposition)and lhe concentration of Bas' in the double spike was
0.6257 X 10-9 mol/g solution as determined
from gravimetry and from the measuredisotopic composition
of Ba in the separatenitrates
(Table 1). The isotopiccomposition
of normal
Ba was as reportedin this work. The concentration of Ba • in the normal Ba standard cal-
culatedby two independentisotopicdilution
experiments
were2.819and 2.822 X 10-9mol/g
solution,respectively.The differencesbetween
thesevaluesand the gravimetricallydetermined
concentration of the normal Ba standard are
fractionation. The relative abundance of Ba •'
in the enriched Ba • and that of Ba •' in the
well within the errorsfor the gravimetryand
the stochiometryof the salts, the gravimetry
enriched BaTMwere each less than 2%. The
of the aliquotstakenand the analyticalerrors.
atom fraction of the principal isotope (Ba•'
The doublespikewas addedto the sample
and Ba•, respectively)in the two solutionsis beforethe chemicalseparationin sucha way
considered to be accurate to within 0.3 and
that over 85% of Ba•' and Ba•, respectively,
0.1%, respectively.The absolutestochiometric originatedfrom the doublespike,whereasover
compositionof the salts used was not demon- 85% of the other isotopesoriginatedfrom the
strated; however, cation impurities were esti- sample.A typical compositionof a mixture of
mated to be below 0.1% basedon ORNL spec- the double spike plus sample is included in
troscopicanalyses.
Table 1. Any subsequent
fractionation,either
By assumingthe saltsto be stochiometricand in the chemicalseparationor in the massspecusing the measured isotopic abundances,a
trometrie analysesis therefore corrected for in
doublespikewasprepared
by mixingaliquots this procedure.The proportionsof doublespike
of the two solutionsto give a calculatedratio
Ba•/Ba •' = 5.178. The measured isotopic
compositionof the double spike correctedfor
discriminationusingBa•¾BaTM-- 5.178is given
in Table 1 and is compatible with the results
givenfor the compositions
of the separatespikes
within the errorsgiven..
A normal Ba standard (BaCO• spec.pure,
Johnson,Mathey, and Co.) with a gravimetrically determinedconcentrationof 2.816 X 10-9
tool Ba•/g solutionwas mixed with the double
and sample were kept constant in most cases
to within 10% to minimize error propagation.
In addition,the samemassspectrometricmeasurements permitted a determination of the Ba
concentrationin the sample since the use of
a, doublespikeis essentially
an isotopedilution
with two spikeisotopes.
The mixture of sample barium and double
spike was analyzedon the massspectrometer,
and the difference
in the fractionationfactorper
massunit was determinedfrom the equation
(137,•
•
•(138•
• [1 -1-•/.•,•,.
= \l-•/mix
[1-- 3(a" a')]-[137•
•
x
4(a"
(381
i
[1--
ISOTOPIC
ANALYSES OF BARIUM
where a' is definedby
•--•/.•
•./
= 1 q- 3a'
and a" by
130•
•'
(130•
• [1 q- S(a" --
3901
example of the calculationfor the case of the
ratio Ba'•ø/Ba•'. The ratios for the mixture of
the doublespike plus sample (subscriptmix)
originate from the same particular analysisas
for equation1.
a')]
.')](2)
where (130/138),,mp•o
isdefined
by
137h
z/ (137•
Here a' and a" are the fractionation
(130•
"' /(130•
"uø
=1--8a'
factors
per massunit for the spikeanalysisand for the
The second term in equation 2 was for all
mixture of double spike plus sample, respecsample ratios of Table • approximately 10%
tively. The superscript M always represents of the first term
measuredvalueson the massspectrometerand
the superscriptstrue represent the absolute
ratios. The ratios indicated by the subscript
spike are the ratios in the pure doublespike;
thoseindicatedby the subscriptsampleare the
ratios in the sample; those indicatedby the
subscriptmix are the ratiosin the mixture of
doublespikeplus sample.
The spiking was done so that the second
term in equation 1 was always less than 2%
of the first term; i.e.
137'•
'•
(137,•
•
The differencea" -- a' was calculateddirectly
or by an iterative procedureby usingthe experimentalresultsfor each run and the independently measured spike compositionrun
(Table 1). The error in a" -- a• contributed
by an uncertaintyin the absoluteabundances
of 1% per mass unit would be less than 1%
of a" -- a'. The valuesof a/' -- a' were always
lessthan 2 parts in 10".
The knowledge of the difference a" -- a'
allows the calculationof isotopic ratios in the
sampleas if they had the same fractionation
a' as that for the analysisof the pure double
spike as given in Table 1. Equation 2 is an
130'•"' (130]
•]
\138/,•mr•o
•'• 1.1\•--•/.i•
Theratio (130/138)
•'
is the isotopic
ratio
sample
of Ba•*ø/Ba
•'8 in the sampleas if it had •dergonethe samefractionationper massunit a' as
the pure doublespike.The other isotopicratios
• the sample as tabula•d (Table 4) are aH
calculatedsimilarly.
Beturning to a considerationof the error
propagationfor this procedurefrom the calibration of the nomal Ba salt with the doublesp•e,
it follows that the possiblegravimetric errors
in the doublespikesolutionare only constrained
by (•/8) -- (4•/8) < fractional error in the
Ba • calibration •2
X 10-•.
Here
and
[C,•]-..
where [C •] is the concentrationof BaTMin the
doublespike.The superscriptassrepresentsthe
assumedconcentrationbasedon the gravimetry
of the salts.
EUGSTER, TERA, AND WASSERBURG
3902
Because of the lack of knowledge of the there were no Ba•* added, we would obtain
absolute stochiometry of the salts composing false fractionorion difference
the double spike, it is not possibleto draw any
proximately
strong conclusionsabout the absolutefractiono-
a* --a •-- a• •- 3 X 10-4-- a•
rion a' from these data.
To demonstratethe sensitivity of the double
and would thus attribute
spiketechnique,the ratio (137/134)•sp,•eof the
doublespikewas changed,addingto the original
an inherent
(3)
fractiona-
tion of 3 parts in 104 per mass unit to the
sample.Inspectionof theseequationsshowsthat
this is equivalent to measuring a sample that
was chemically fractionated by this amount.
This correspondsto a sample fractionation for
Ba•ø/Ba• of
amount of Ba•7 in the double spike 9 parts in
104of pure fissionproducedBa•7. This enriched
double spike was mixed with an aliquot of the
Forest City sample (Table 4) and analyzed.
The ratio of (137/134)•sp,•e.in the slightly enriched double spike would thus be a factor of
(1 + 0.0009) greaterthan in the originaldouble
spike, all other ratios being essentially unchanged.Returning to equation 1, which determines the massspectrometerdiscrimination,we
= (1 q- 8 X 3 X 10-4)
fractionated
.(130h
•'
(4)
\138/•m.•
have
unf ract
ionat
ed
Table 2 shows the results for the enrichment
137•
•
(137•
•
experiment compared with the results for an
•-•/..ke*-(1-+-9X 10
-4)
aliquot of the samesamplewhosedoublespike
has not been enriched. The measured differences
(137•
•
-- [1-- 3(a"-- O•')]\-•/mi
x+ R
where R is unchangedfrom the original double
spike. To the necessaryaccuracy
1-•/•,•-- [1-- 3(•"-]-3X 10
-• --
(137•
• +
-- 9 X
Here a" and a' are again the true instrumental
fractionorion
factors. If we were to cal-
culate the discrimination
difference in the ex-
periment with the enriched double spike as if
are in good agreement with the differences
calculatedaccordingto equations3 and 4.
This experiment showsthat a true fractionorion of 3 parts in 104 per massunit can clearly
be detectedby the describedtechnique.
RESULTS AND DISCUSSION
Isotopic ratios of barium. The resultsfor the
analysesof three unspiked meteoritesare shown
in Table 3. Sincetheseanalyseswere carried out
when the automatic digitized data acquisition
system was still in an early stage of completion, someof the data had to be taken by the
usual analogtechniqueby measuringthe peak
heightson a strip chart.
TABLE 2. Resultsfor Two Runs of the Forest City ChondriteDouble Spikedwith BsTMsnd Bs
The doublespikeof run B hsd sn sdditionMenrichmentof 9 psrtsin 10• of pure fissionproduced
BalaO/Ba
138
X 104 Bs's•/Bs
m X 104 Ba,
la•'/Ba,
la8X 104 Ba,
laø/Ba,
TM
X 104
A
B
Forest City
Forest City
(spike enriched)
1095.4 4- .3
1096.0 4- .9
919.5 4- .4
920.6 4- .8
14.12 4- .02
14.14 4- .03
14.76 4- .02
14.81 4- .05
Fractional differences between run A •nd B
(p•rts in 10a)
Fractional
5.5
12
14
34
6.0
9
18
24
differences c•lcu-
l•ted •ccording to (3)
and (4) (p•rts in 104)
ISOTOPIC
•o
•'•
o
o
o
o
o
o
o
ANALYSES
OF BARIUM
3903
3904
EUGSTER, TERA, AND WASSERBURG
TABLE 4. IsotopicRatios of Barium in the InvestigatedSamplesafter Correction
for Fractionation by Means of a Double Spike of BaTMand Ba•a7
These data are taken with an integrating digital voltmeter.
Ba•6/BaTMX 104 Ba•5/Ba•sX 104 Ba•a•'/Ba•s
X 104 Ba•ø/Ba•s X 10*
Reagent Ba
Terrestrial Samples
1094.5 q- . 8
*
*
14.76 q- . 1
Terrestrial standard W-1
1095.3 q- .7
1095.2 q- .7
*
*
14.75 q- .04
14.75 q- .04
Average and mean deviation
1095.0 q- .3
919.6 q- .7
919.1 q- .5
919.4 q- .3
14.75 q- .003
Chondrites
Bruderheim a
b
1095.0 q- .3
1095.3 q- .9
919.3 q- .3
919.4 q- .9
*
*
14.76 q- .02
14.74 q- .04
Leedey
Forest City
1096.7 q- 1.5
1095.4 q- .3
919.2 q- 1.4
919.5 q- .4
*
14.12 q- .02
14.74 q- .05
14.76 q- .02
Abee
1094.5 q- .8
919.1 q- 1.4
14.11 q- .05
14.75 q- .04
*
q- .02
14.74 q- .05
14.77 q- .02
A chondrites
Pasamonte
Nuevo Laredo
1095.6
1095.1
E1 Taco
Weekeroo
1095.8 q- .6
1095.6 q- 1.2
919.7
919.4
q- .6
q- 1.0
14.14 q- .09
14.13 q- .02
14.77 q- .09
14.79 q- .03
1095.4
919.4
q- .1
14.12
14.76
q- 1.0
q- .4
919.5
919.4
q- 1.3
q- .6
14.12
Silicate Inclusionsof Iron Meteorites
Station
Average for all meteorites
and mean deviation
q- .4
q- .01
q- .01
* No data taken.
For the individual analyses tabulated, the
mean deviations
three terrestrial and nine meteoritic samples
after correction for the mass spectrometer
of 10 ratios are shown. The
fractionation
data taken with a strip chart recorder have
mean deviationsup to four times greater than
for the data taken in the digital mode. Furthermore,all valuesobtainedin the analogmode
have an additional error of about 0.05% due to
the uncertainty in the correction for the recorder nonlineartry. Because each analysis is
normalized to Ba•/Ba • -- 0.09194 (the average for nine doublespikedsamplescorrectedfor
fractionation, see Table 4), the scatter for the
.otherratios is enlarged.
The total spreadof the isotopicratios for all
six terrestrial and meteoritic samplesin Table 3
is less than 0.2% for the isotopesBa•3•-• and
about 0.8% for the lessabundantisotopesBaTM
and Ba•'. The averagesfor the terrestrial Ba
agreewell with thosefor the meteoriticBa; the
differencesare 0.2% or less and they are well
within the experimental errors. Thus, we can
conclude,so far, that there are no anomalies
causedby nuclear processes
in thesemeteorites
at any particular massposition.
Table 4 shows the isotopic ratios of Ba in
and
of
the
contribution
Ba•ø'•3•'•' •' • • by the doublespike using
equations1 and 2. All data in Table 4 are taken
with a single-focusing
massspectrometerwith a
programmablemagneticfield and a digital voltmeter for ion beam integration [Wasserburg
et al., 1968, 1969].
The errorsin Table 4 were evaluatedby calculating new ratios
(Ba-/Ba•s)•'
usingvaluesfor the ratios in equations1 and 2
differing by one mean deviation from their
averagemeasuredvalues and in the direction to
give the maximum spread in the two calculated
ratios
(Ba•/Ba•as•
•'
,• •ampl
e
Figure 2 showsthe values of 3•
plotted
versusmassnumbers (m) obtained for the data
givenin Table 4.
Here 3• is definedby
m
1•8
a Jmeteorite
,
.
,,, [Ba"'/B
,as, m -/Ba'1,,,..,.,,,:.
,o,,•.,.r
.ampi..
x 10,•
138[Ba
(•138•
of
ISOTOPIC
ANALYSES OF BARIUM
3905
•,
is the fractional differencein parts per
thousandof the isotopicabundancerelative to
alies [Murthy, 1960, 1962, 1963; Umemoto,
1962; $hima and Honda, 1963].
a terrestrial standard.
We would clearly see an effect of 0.2% in the
The total spread of the corrected isotopic average Ba•8øor Ba•8• abundance. For chonratios for all isotopesof the twelve terrestrial drites this correspondsto a measurable differand meteoritic samples is in most cases less ence of 3 x 10•ø atoms per gram. This is
than 0.2%. The averages for the meteorites equivalent to the number of excess atoms of
agree with those for the three terrestrial sam- Xe TMwhichis typically found [Reynolds,1960b]
pleswithin much lessthan 0.1% for all isotopes and attributed to I • decay.
and the agreementbetweenthe spiked and the
Our data excludethe productionof Ba•ø and
normalizedunspikedsamplesas well within the BaTMby a radioactiveprecursorwith an abunsmall experimentalerrors. By using the lower dancecomparableto that of I TM,which enriched
extremeof the terrestrialaverageand the upper the meteoritic Ba relative to the terrestrial
extreme of the meteoritic average for the ratio Furthermore, upper limits can be placed on
Ba•8ø/Ba
TM,an upper limit for the fractionation differencesin integrated high-energy proton
of the meteoritesversusthe terrestrial samples fluxes for uniform irradiation conditions in the
can be estimatedas being lessthan 2 parts in early history of the solar system.If an average
10' per massunit.
target concentrationof 5 ppm at about mass
It is evidentthat thesedata showthe previous 140 and an effective spallation crosssectionof
resultsof Umemoto [1962] to be spurious.The
10 mb are assumed,a high-energyproton flux
effectshe reportedare most probablythe result of about 5 x 10•9 protons/cm"is required to
of instrumentalfractionation,which appearsto enrichBa•ø or Ba• in chondritesby 0.2%. This
be characteristic of the so-called La Jolla anomis oneorder of magnitudehigherthan the upper
Bruderheim
a (4)
Bruderheimb (4)
O
(•)
Bruderheim(::5)
Pasamonte(4)
Pasamonte
(:5)
Leedey(4)
Leedey(:5)
[]
A
A
ForestCity(4)
Abee (4)
EI Taco (4)
<:•
•
+
Nuevo Laredo(4)
V
Weekeroo(4)
X
AVERAGE FRACTIONATION
OF UMEMOTO
AX
v+
+
A
-2
d54
mass
'!:55
456
'1:57
'158
m
Fig. 2. B•rium •"xssvalues for the investigated meteorites. The numbers (3) and (4) •fter
the meteorite names refer to the correspondingt•ble in this work.
The fractionation line to be expected from the work of Umemoto [1962] is showa for comparison.
3906
EUGSTER, TERA, AND WASSERBURG
'•
TABLE 5.
Concentration of Barium in the Investigated Samples
Metallic iron wasmagneticallyremovedfrom the Leedeyand Abeesamples,but not from all other
samples.
Ba Concentration, ppm
Sample
Class
This Work
LiteratureValues
Bruderheim
L chondrite
3.37
3.4/
Leedey
ForestCity
L chondrite
It chondrite
3.85
3.37
3.76"
3.65%4. I a, 9e
Abee
Enstatite
2.41
2.41"
Pasamonte
Nuevo Laredo
E1 Taco
Eucrite
Eucrite
Ni-poor ataxite
Weekeroo
Octahedrite
Station
chondrite
28.2
39.3
2.37
28.6", 26 c
39.4", 40%46a
8.70
Terrestrial standard W-1
158
158 b
Tera, Burnett, and Wasserburg,to be published.
Schnetzleret al. [1967].
Duke and Silver [1967].
Hamaguchi ½tal. [1957].
Pinson et al. [1953].
Wyttenbach and Dulakas (private communication,1965).
limit of 3 X 10•8 particles/cm• for •500-Mev
particles calculated by Burnett et al. [1966]
based on isotopicanalysesof potassiumin terrestrial and meteoritic samples.The latter experiment is of coursemuch more sensitivefor
the determinationof an upper limit for the flux
of an early irradiation of the solar system.
Barium
concentrations.
Ba found in the meteorites
The concentration of
and in the diabase
standard W-1 is given in Table 5. A small
laboratory blank contribution of less than 2%
was corrected. The analytical error in these
figuresis lessthan 1%. The differences
between
these values and the results obtained by other
authors are most probably due to inhomogeneitiesof the meteorites.
Isotopiccomposition
o/ natural barium. The
values in Table 6 given for this work represent
the averagesfor both meteoritesand terrestrial
samples,sinceno differences
in the isotopiccom-
positionhave beenfound.The ratiosBa•/Ba •
and Ba•/Ba • representthe averagesof the six
unspikedsamples(Table 3), whereasthe other
ratios representthe averagesfor the data tabu-
TABLE 6. Isotopic Compositionof Barium
The errorsof this work equal 3• .... = 3[• /Xx?/n(n - 1)]• calculatedfrom the mean valuesfor each
massspectrometeranalysisas given in Tables 3 and 4. Nier believeshis ratios to be correctwithin 2%
exceptthe onesfor Ba•aøand Ba•a•,whichmay be in error by 4%. The errorsgivenby us for the valuesof
Umemoto have been recalculatedby us from his data to correspondto 3• .... for six analyses.
Ba•/Ba,•S
X 104
Ba•/Ba•S
Ba•/Ba•S
X 104
X 104
Ba•4/Ba•S
Ba•/Ba•S
X 104
This work
1566.54-0.5
1095.34-0.5
919.44-0.2
337.1
1580
1090
920
337
13.6
14.1
1547.94-3.0
1086.84-2.7
908.04-2.4
331.974-1.0
13.7124-0.05
14.2154-0.06
1554.4
1095.9
919.4
337.5
14.06
14.69
Ba•/Ba•
o. 09194
14.12
4-0.02
X 104
Nier [1938]
Umemoto [1962]
Values of
Umemoto
normalized
4-0.3
Ba•0/Ba•S
X 104
14.76
to
=
4-0.02
ISOTOPIC ANALYSES OF BARIUM
TABLE
7.
3907
Percentage Abundances of the Isotopes of Barium
Mean
of Atomic
Weight of Ba
Ba•
Ba•7
Ba•6
Ba•
Ba•4
Ba•2
137.9050
136.9055
135.9043
134.9056
133.9046
131.9051
71.699
11.232
7.853
6.592
2.417
0.1012
0.1058
4-.007
4-.004
-•.004
q-.002
-•.003
q-.0002
q-.0002
71.66
11.32
7.81
6.59
2.42
0.097
0.101
4-1.4
4- .2
4- .16
4- .13
4- .05
4- .004
4- .004
C •'- -- 12 Scale
Atomic weight C •'- •- 12 scale
[Matranch et al. 1965]
Atom per cent abundance,
this work
Statistical
error
Atom per cent abundance
(Nuclear data tables U.S.
Atomic Energy Commission,
compiled by G. H. Fuller,
1959. Data from Nier [1938])
lated
in
Table
4.
The
error
for
the
ratios
Ba•O,•8,,•5, •/Ba• introducedby the correction
of the contribution of the double spike is less
than 0.1%.
The given errors do not include the uncertainty of the gravimetrically determined value
of Ba•/Ba •' on which the correction of the
laboratory fractionation is based. These data
represent our best estimatesof the absolute
ratios, although it should be clear that the
purpose of this work was to searchfor isotopic
variations and not to establish absolute ratios,
which require better gravimetric procedures
than
used here. The
data in Table
6 are all
self-consistent
to within the precisiongivenwith
a fixed fractionation per mass unit.
In Table 6 the isotopiccompositionobtained
in this work is compared with the terrestrial
compositiongiven by Nier [1938] and by
Umemoto [1962]. If we normalize Umemoto's
values to Ba•5/Ba• -- 0.09194 and extend the
errorsthat he reportsto a 99% confidence
limit,
his results are compatible with the data reported here.
The abundancesgiven by Nier [1938] are,
as usual, confirmed to be correct within the
error limits that he quotes. The results presentedhere shouldsupersedethesedata as they
are more precise and significantly revise the
abundancesof the light isotopesBa•ø and Ba•
for which we obtain about 4% higher abundances.The percentageabundanceswhich correspond to the abundanceratios found in our
work are givenin Table 7. With isotopicweights
accordingto the C• = 12 scale [Mattauch et
al., 1965] one calculatesan atomic weight of
137.327 for Ba.
129.9062
137.327
Acknowledgments. We wish to thank D. S.
Burnett for valuable discussionsand suggestions
and D. A. Papanastassiou for his support in the
mass spectrometry. We are indebted to our colleagues who supplied meteorite samples used in
this work: Pasamonte, Leedey, Forest City, and
Weekeroo
Station
were
obtained
from
the
Nininger Meteorite Collection at the Arizona
State University through the aid of C'. W. Moore.
E1 Taco was obtained from YI. Hintenberger,
M.P.I., Mainz, Germany. Bruderheim was given
to us by L. T. Silver from a sample provided to
him by R. E. Folinsbee. Nuevo Laredo was given
to us by L. T. Silver. Abee was provided by
J. A. V. Douglas, Geological Survey of Canada.
This work was supported by the National
Science Foundation (grants GP 9114 and GP
7976).
REFERENCES
Burnett, D. S., I-I. $. Lippolt, and G. $. Wasserburg, The relative isotopic abundance of K 'ø in
terrestrial and meteoritic samples, J. •eolrhys.
Res., 71, 1249, 1966. (See also; Correction, J.
•eophys. Res., 71, 3609, 1966.)
Chakraburtty, A. K., C. M. Stevens, H. C. Rushing, and E. Anders, Isotopic composition of
silver in iron meteorites, J. •eophys. Res., 69,
505, 1964.
Crouch, E. A., and T. A. Tuplin, Isotopic composition and the atomic weight of naturally
occurring molybdenum: A possible reflexion of
the creation process,Nature, 202, 1282, 1964.
Duke, M. B., and L. T. Silver, Petrology of
eucrites, howardites, and mesosiderites, Geochim. Cosmochim.Acta, 31, 1637, 1967.
Eugster, O., P. Eberhardt, and J. Geiss, The
isotopic composition of krypton in unequilibrated and gas rich chondrites, Earth Planetary
$ci. Letters, 2, 385, 1967.
Gradsztajn, E., M. Salome, A. Yaniv, and R.
Bernas, Isotopic analysis of lithium in the
Itolbrook meteorite and in terrestrial samples
with a sputtering ion source mass spectrometer,
Earth Planetary Sci. Letters, 3, 387, 1967.
3908
EUGSTER, TERA, AND WASSERBURG
I-Iamaguchi, I{., G. W. Reed, and A. Turkevich,
Uranium and barium in stone meteorites, Geochim. Cosmochim. Acta, 12, 337, 1957.
Krummenacher, I)., C. M. Merrihue, R. O. Pepin,
and J. tI. Reynolds, Meteoritic krypton and
barium versus the general isotopic anomalies in
meteoritic xenon, Geochim. Cosmochim.Acta,
26, 231, 1962.
Mattauch, J. t{. E., W. Thiele, and A. H. Wapstra,
1964 atomic mass table, Nucl. Phys., 67, 1, 1965.
Murthy, V. R., Isotopic compositionof silver in
an iron meteorite, Phys. Rev. Letters, 5, 539,
1960.
Murthy, V. R., Isotopic anomalies of molybdenurn in some iron meteorites, J. Geophys.
chondrites and some ultramafic rocks, Geochim.
Cosmochim.Acta, 4, 251, 1953.
Reynolds,J. I{., Determination of the age of the
elements,Phys. Rev. Letters, 4, 8, 1960a.
Reynolds, J. tI., Isotopic composition of primordial xenon,Phys. Rev. Letters, 4, 351, 1960b.
Schnetzler, C. C., I-I. tI. Thomas, and J. A. Philpotts, The determination of barium in G-1 and
W-1 by isotope dilution, Geochim. Cosmochim.
Acta, 31, 95, 1967.
Shields, W. R., ed., NB$ Tech. Note 277, 1966.
Shima, M., and M. tIonda, Isotopic abundanceof
meteoritic lithium, J. Geophys. Res., 68, 2849,
1963.
Umemoto, S., Isotopic compositionof barium and
cerium in stone meteorites, J. Geophys. ReRes., 67, 905, 1962.
search, 67, 375, 1962.
Murthy, V. R., Elemental and isotopicabundances
of molybdenum in some meteorites, Geochim. Wasserburg, G. J., I). A. Papanastassiou, E. V.
Nenow, and C. A. Bauman, A programmable
Cosmochim.Acta, 27, 1171, 1963.
magnetic field mass spectrometer with on-line
Murthy, V. R., Stable isotope studies of some
data processing(abstract), Trans. Am. Geophys.
heavy elements in meteorites, in Isotopic and
Union, 49, 350, 1968.
Cosmic Chemistry, edited by I-I. Craig, S. L.
Wasserburg, G. J., D. A. Papanastassiou, E. V.
Miller, and G. J. Wa•erburg, 488 pp. North
Nenow, and C. A. Bauman, A programmable
Holland, Amsterdam, 1964.
magnetic field mass spectrometer with on-line
Nier, A. O., The isotopicconstitutionof strontium,
data processing,Rev. $ci. Instr., 40(2), 288, 1969.
barium, bismuth, thallium, and mercury, Phys.
Wetherill, G. W., Isotopic composition and conRev., 54, 275, 1938.
centration of molybdenum in iron meteorites,
Pepin, R. O., Trapped neon in meteorites,Earth
J. Geophys. Res., 69, 4403, 1964.
Planetary $ci. Letters, 2, 13, 1967.
(Received January 24, 1969;
Pinson, W. I-I., L. I-I. Ahrens, and M. L. Franck,
revised April 1, 1969.)
The abundancesof Li, Sc, Sr, Ba, and Zr in