drite, and the abundance and isotopic composition of xenon and krypton are reported in the gases released by ... Many clues of early geologic events have been.
und gravimetrischen
24:
Stimmung d e r E r g e b n i s s e m a c h t d e u t l i c h , d a ß f r ü h e r für 2 5 ° C veröffentlichte Werte v o n
Z)n = 1 , 0 - 1 0 ~ 6 c m 2 s _ 1
10~20 Messungen
mit
Messungen
mit Tritium
phischen
und
leichtem
gravimetrischen
Durchtrittshemmungen 24
Wasserstoff. als a u c h
die
Sowohl
- 1
auf
10~9 oder
den Einfluß v o n
gar
Grenzflächen-
reaktionen zurückzuführen sind.
röntgenogra-
Methoden
unabhängig.
die
cm2 s
sind
Die
von
Überein-
E. WICKE U. A. OBERMANN, Z. Physik. Chem. N.F. (im Drude). — A. OBERMANN, Diplomarbeit, Münster 1970.
H e r r n P r o f . D r . E . WICKE möchten wir an dieser Stelle f ü r wertvolle H i n w e i s e und a n r e g e n d e Diskussionen herzlich d a n k e n . — D e r Deutschen Forschungsgemeinschaft d a n k e n w i r f ü r die Unterstützung unserer A r b e i t mit Personal- u n d Sachmitteln.
Mass Fractionation and the Isotopic Anomalies of Xenon and Krypton in Ordinary Chondrites E . W . HENNECKE a n d 0 . K . MANUEL Department of Chemistry, Universiy of Missouri, Rolla, Missouri (USA) (Z. Naturforsch. 26 a, 1980—1986 [1971] ; received 7 August 1971) The abundance and isotopic composition of all noble gases are reported in the Wellman chondrite, and the abundance and isotopic composition of xenon and krypton are reported in the gases released by stepwise heating of the Tell and Scurry chondrites. Major changes in the isotopic composition of Xe result from radiogenic Xe 129 and from variations in the isotopic mass fractionation pattern in the different temperature fractions. The isotopic composition of trapped krypton in the different temperature fractions of the Tell and Scurry chondrites displays smaller fractional changes than xenon, but the isotopic composition of these two gases covary in the manner expected from mass dependent fractionation. Many
clues
of
early
geologic
events h a v e
been
n o t e d that a c o m p a r i s o n o f t h e e a r t h ' s i n v e n t o r y o f
Kr
n o b l e g a s e s w i t h the s o l a r a b u n d a n c e s o f t h e s e ele-
and X e . T h e chemical inertness and volatile nature,
ments s h o w s preferential loss f r o m terrestrial mate-
e v e n at r e l a t i v e l y l o w t e m p e r a t u r e s , r e s u l t e d in al-
rial o f
most
w o r k o n n o b l e gases in terrestrial sediments
r e c o r d e d in t h e s t a b l e n o b l e g a s e s , H e , N e , A r ,
complete
condensable
loss
of
material
these
when
elements
solid
from
planetary
f o r m e d in o u r s o l a r s y s t e m . M a n y i s o t o p i c
more
the g a s e s l i g h t e r t h a n k r y p t o n .
Subsequent
h i g h c o n c e n t r a t i o n s o f x e n o n w h i c h , w h e n a d d e d to
anoma-
the a t m o s p h e r i c i n v e n t o r y o f n o b l e g a s e s , s h o w that
lies o f these e l e m e n t s h a v e b e e n g e n e r a t e d in s o l i d
the e a r t h ' s f r a c t i o n a t i o n
p l a n e t a r y m a t e r i a l s u b s e q u e n t t o this s e p a r a t i o n , b y
the h e a v i e s t
induced
g a s e s in s t o n e m e t e o r i t e s d i s p l a y a s i m i l a r
active
nuclear
decay
of
reactions more
and
by
abundant
natural
radio-
elements.
stable n o b l e
gases b y
nuclear
processes
of noble gases extends
stable gas, x e n o n .
nation pattern 4'
A l t h o u g h the g e n e r a t i o n o f i s o t o p i c a n o m a l i e s o f all t h e
5
SIGNER a n d
duction
by
n e o n and a r g o n in planetary material. T h e y
of
a covariance of A r 3 6 / A r 3 8 , N e 2 0 / N e 2 2 and
simple
isotopic
anomalies
masä
of
noble
fractionation
gases
at t h e t i m e
the s e p a r a t i o n o f t h e s e f r o m m o r e c o n d e n s a b l e m e n t s . I n 1 9 4 9 SUESS
1
a n d BROWN
2
ele-
ratios
independently
NUEL
Reprint requests to Prof. Dr. O. K. MANUEL, Department of Chemistry, University of Missouri-Rolla, Rolla/Missouri 65401, USA.
4
6
1
H . E. SUESS, J. Geol. 5 7 , 6 0 0
2
H. BROWN, The Atmosphere of the Earth and the Planets, University of Chicago Press, Chicago 1949.
[1949],
3
R . A . CANALAS, E . C . ALEXANDER, JR., a n d O . K . M A N U E L ,
5
7
in 7
generating
the r o l e o f
fractionation
isotopic
fractio-
atmospheric
and
re-
104 — 105.
SUESS 6 d i s c u s s e d
in
to
noble
w i t h the x e n o n p r e f e r e n t i a l l y
tained o v e r n e o n b y a f a c t o r
is
The trapped
well d o c u m e n t e d , there is also e v i d e n c e f o r the p r o of
found
3
matter
isotopic
meteoritic
mass
anomalies
Ne20/Ar36
gases.
r e p o r t e d v a r i a t i o n s in t h e t r a p p e d
of
noted MA-
Ne20/Ne22
J. H. REYNOLDS, Phys. Rev. Letters 4, 351 [1960]. O. K. MANUEL and M. W. ROWE, Geochim. Cosmochim. Acta 28. 1999 [1964]. P. SIGNER and H. E. SUESS. in: Earth Science and Meteorites, North-Holland Publ. Co., Amsterdam 1963. O. K. MANUEL, Geochim. Cosmochim. Acta 31, 2413 [1967].
J. Geophys. Res. 73, 3331 [1968].
Unauthenticated Download Date | 9/24/15 11:39 PM
and
Ne21/Ne22
ratios
in
the
different
temperature
d e r to o b t a i n a d d i t i o n a l d a t a w i t h w h i c h to e x a m i n e
f r a c t i o n s o f the F a y e t t e v i l l e m e t e o r i t e a n d s u g g e s t e d
the current
that t h e s e v a r i a t i o n s r e s u l t f r o m i s o t o p i c m a s s f r a c -
n o b l e g a s a n o m a l i e s in m e t e o r i t e s . S a m p l e s o f t h r e e
tionation.
o r d i n a r y c h o n d r i t e s w e r e u s e d f o r this i n v e s t i g a t i o n .
However,
PEPIN a n d
coworkers8-10
re-
framework
of
ideas
on
the
origin
of
p o r t e d t h a t t h e r e is n o s i g n t h a t d i f f u s i v e f r a c t i o n a t i o n is r e s p o n s i b l e f o r a n y o f t h e i s o t o p i c v a r i a t i o n s of
meteoritic
neon.
Recent
results
on
the
c o m p o s i t i o n o f t r a p p e d m e t e o r i t i c H e , N e a n d A r in the
laboratories
at
Minnesota,
Chicago
and
have been attributed to nuclear reactions other
authors15-17
served variations
have
maintained
result f r o m
Rice
~14, but
10
that
the
simple isotopic
obfrac-
tionation. F o r the h e a v y n o b l e gases, a s i m i l a r
divergence
o f o p i n i o n s h a s d e v e l o p e d . SRINIVASAN e t a l . 1 8 first suggested
that
spontaneous
fission
of
superheavy
elements m a y b e responsible f o r the enrichment heavy
xenon
isotopes
in
ANDERS a n d HEYMANN conclusion isotopes
by
carbonaceous
comparing
with
the e x c e s s
the c o n t e n t
carbonaceous
chondrites,
of
chondrites.
h a v e a r r i v e d at a s i m i l a r
19
of
volatile
and
heavy
xenon
elements
in
EBERHARDT e t al.
h a v e i n t e r p r e t e d the i s o t o p i c c o m p o s i t i o n
20
of
solar-
t y p e x e n o n as e v i d e n c e f o r l a r g e a m o u n t s o f
fissio-
genic xenon
in c a r b o n a c e o u s
KURODA a n d MANUEL
15
chondrites.
However,
recently pointed out
the e n r i c h m e n t o f h e a v y x e n o n i s o t o p e s in aceous and gas-rich meteorites enrichment of
heavy
neon
that
carbon-
is p a r a l l e l e d
isotopes. These
by
an
authors
c o n c l u d e d that the enrichment o f the h e a v i e r
isoto-
pes o f b o t h gases result f r o m i s o t o p i c mass f r a c t i o nation. Additional
evidence
f o r the p r o d u c t i o n
isotopic anomalies of meteoritic xenon and
of
krypton
b y fractionation have been reported f r o m noble gas analyses
of the
LEOVILLE
21
and
chon-
POTTER22
drites. T h i s s t u d y o f the i s o t o p i c c o m p o s i t i o n
Measurements
isotopic
of
noble
gases in ordinary chondrites was undertaken in
or-
8
R. 0 . PEPIN, Earth Planet. Sei. Letters 2 , 1 3
9
R. 0 . PEPIN, Origin and Distribution of the Elements, Pergamon Press, Oxford and New York 1968.
[1967].
10
D. C. BLACK and R. 0 . PEPIN, Earth Planet. Sei. Letters 6,
Relatively l a r g e meteorite s a m p l e s , w e i g h i n g a b o u t 10 g r a m s each, w e r e used in this study. T h e s e w e r e purchased f r o m the A m e r i c a n M e t e o r i t e L a b o r a t o r y ( A M L ) . T h e n a m e and type of each meteorite, the s a m p l e weight and the A M L c a t a l o g u e n u m b e r of the s p e c i m e n f r o m which o u r s a m p l e s were taken are as f o l l o w s : T h e W e l l m a n , T e x a s olivine bronzite chondrite, 1 0 . 8 8 8 g r a m s f r o m s p e c i m e n # H 1 2 . 5 6 ; the T e l l , T e x a s olivinie hypersthene chondrite, 8 . 4 7 4 g r a m s , f r o m s p e c i m e n # H 2 4 . 6 7 ; and the S c u r r y , T e x a s olivine bronzite chondrite, 7 . 9 0 9 g r a m s , f r o m s p e c i m e n # H 65.25. T h e s a m p l e s w e r e m o u n t e d in side-arm c h a m b e r s of a quartz extraction bottle. T h e s a m p l e s w e r e heated to ~ 6 0 ° C o v e r n i g h t to r e m o v e s u r f a c e c o n t a m i n a t i o n , the m o l y b d e n u m c r u c i b l e was d e g a s s e d at 1 8 0 0 ° C and the pressure of the system r e d u c e d to 5 x 1 0 - 8 T o r r . T h e extraction bottle and preliminary " g e t t e r s " w e r e then isolated f r o m the rest of the system b y metal b e l l o w s valves, the s a m p l e to b e analyzed w a s then d r o p p e d m a g n e t i c a l l y into the m o l y b d e n u m c r u c i b l e which was heated b y a r a d i o f r e q u e n c y i n d u c t i o n heater. A n o p t i c a l p y r o m e t e r was used to estimate the extraction temperatures. Each extraction temperature was m a i n tained f o r 3 0 minutes, and the evolved gases w e r e c l e a n e d in the extraction system b y titanium at 8 5 0 ° C and b y c o p p e r - o x i d e at 5 5 0 ° C . A f t e r these p r e l i m i n a r y " g e t t e r s " w e r e c o o l e d to r o o m temperature, the g a s e s w e r e then p u m p e d through the metal valve into a seco n d clean-up system b y adsorption on charcoal c o o l e d witl l i q u i d N 2 or solid C 0 2 . A f t e r isolating the g a s e s in the second c l e a n - u p system, they w e r e driven f r o m the charcoal at 2 0 0 ° C and e x p o s e d to a s e c o n d s u r f a c e of titanium s p o n g e at 8 5 0 ° C . In the case of parated into f o u r on c h a r c o a l ; the H e and N e , the 17
D . C . BLACK, M e t e o r i t i c s 4 , 2 6 0
[1969].
12
D. C. BLACK, Geochim. Cosmochim. Acta 34, 1 3 2
13
E . ANDERS, D . H E Y M A N N , a n d E . M A Z O R , G e o c h i m .
[1970].
E . M A Z O R , D . HEYMANN, a n d E . ANDERS, G e o c h i m .
B . SRINIVASAN, E . C . ALEXANDER, JR., O . K . M A N U E L , a n d
19
E . ANDERS a n d D . H E Y M A N N , S c i e n c e 1 6 4 , 8 2 1
20
P . EBERHARDT, J. GEISS, H . GRAF, N . GRÖGLER, U .
D. E. TROUTNER, Phys. Rev. 179,1166 [1969].
HENBÜHL,
Cosmo-
15
16
P. K . KURODA
and
0.
K . MANUEL,
21
Nature London
1113 [1970]. 0 . K. MANUEL, Meteoritics 5, 207 [1970].
H . SCHWALLER,
[1969].
J. SCHWARZMÜLLER,
KRÄ-
and
A.
STETTLER, Geochim. Cosmochim. Acta Supp. 1, 2, 1037 [1970].
Cosmo-
chim. Acta 34, 781 [1970].
Com-
18
chim. Acta 34,127 [1970]. 14
B . SRINIVASAN a n d O . K . M A N U E L , O n the I s o t o p i c
position of Trapped Helium and Neon in Carbonaceous Chondrites, Earth Planet. Sei. Letters, in press [1971].
395 [1969]. 11
W e l l m a n , the n o b l e gases w e r e sef r a c t i o n s f o r analysis b y adsorption b o i l i n g temperature of N 2 released sublimation temperature of C 0 2 re-
O . K . M A N U E L , R . J. W R I G H T , D . K . MILLER, a n d P .
K.
KURODA, J. Geophys. Res. 75, 5639 [1970].
227, 22
O. K .
M A N U E L , D . K . MILLER, R . J. W R I G H T , a n d P .
K.
KURODA, Solar Type Krypton, submitted to J. Geophys. Res. [1971].
Unauthenticated Download Date | 9/24/15 11:39 PM
leased A r , the f r e e z i n g p o i n t of H g released K r , and finally the X e w a s released f r o m the charcoal at 1 5 0 ° C . F o r T e l l and S c u r r y the n o b l e gases were p u m p e d into the s e c o n d c l e a n - u p system b y adsorption on charcoal c o o l e d with solid C 0 2 , and those gases not retained o n charcoal at this temperature ( H e , N e and A r ) were p u m p e d f r o m the s e c o n d clean-up system p r i o r to the final s c r u b b i n g on hot titanium ( 8 5 0 ° C ) . T h e k r y p t o n and x e n o n weTe let into the mass spectrometer as separate f r a c t i o n s b y selective adsorption of the x e n o n on charcoal at the freezing point of m e r c u r y . T h e g a s e s w e r e analyzed statically in a R e y n o l d s ' type 4 . 5 inch 6 0 ° sector mass spectrometer 2 3 . T h e mass s p e c t r o m e t e r w a s calibrated b e f o r e and after each s a m p l e b y analyzing small v o l u m e s of air ( ~ 0 . 0 1 c c S T P ) b y the same p r o c e d u r e of analysis as u s e d f o r the s a m p l e . T h e sensitivity of the spectrometer f o r each n o b l e g a s and the mass discrimination a c r o s s the isotopes of each gas w e r e c a l c u l a t e d b y c o m p a r i n g the p e a k heights with the a t m o s p h e r i c a b u n d a n c e s of n o b l e g a s e s 2 4 and the isotopic c o m p o s i t i o n of atmos p h e r i c n e o n 2 5 , a r g o n 2 6 , k r y p t o n 2 7 and x e n o n 2 8 . N o c o r r e c t i o n f o r mass discrimination was applied to helium. T h e errors reported in the isotope ratios are one standard deviation ( a ) f r o m the least squares line t h o r u g h the o b s e r v e d ratios as a f u n c t i o n of residence time in the mass spectrometer. Results f r o m b l a n k
analyses, w h e r e the identical p r o c e d u r e s w e r e f o l l o w e d f o r g a s e s evolved f r o m a hot m o l y b d e n u m c r u c i b l e , s h o w e d no significant c o n t a m i n a t i o n e x c e p t at m a s s 78. D u e to variations in the sensitivity of the mass spectrom e t e r the g a s c o n t e n t has much larger errors than the i s o t o p e ratios, such that the content of each n o b l e gas h a s an estimated e r r o r of + 2 0 % .
Results and Discussion 1. Noble Gases in Wellman T h e a b u n d a n c e s and i s o t o p i c c o m p o s i t i o n o f the n o b l e gases in W e l l m a n gether
with
the
noble
gases
in
are s h o w n in T a b l e
isotopic
composition
carbonaceous
of
chondrites
1 to-
trapped and
the
s o l a r - t y p e n o b l e g a s e s o b s e r v e d in g a s - r i c h m e t e o r i tes a n d
in the m o o n .
The isotopic composition
t r a p p e d H e , N e a n d A r in c a r b o n a c e o u s
of
chondrites
a r e t h e r a n g e o f v a l u e s r e p o r t e d in a c o m p r e h e n s i v e study
13'14
age values
and the t r a p p e d K r and X e are the aver29' 30
observed
in c a r b o n a c e o u s
tes. T h e i s o t o p i c c o m p o s i t i o n
chondri-
of solar-type He,
Ne
and A r are f r o m the Fayetteville gas-rich meteorite
7,
Table 1. Concentration and isotope composition of noble gases in the Wellman chondrite. Noble gases
Wellman observed
Trapped gas in carbonaceous chondrites
trapped
He 3 /He 4 He4
0.0253 ± 0 . 0 0 0 4 6.04 x 1 0 ~ 7 cc STP/gm
0.88x10- 4 5 . 2 5 x 1 0 - 7 cc STP/gm
Ne 20 /Ne 22 Ne 21 /Ne 22 Ne22
1.415 ± 0 . 0 0 3 0.876 ± 0 . 0 0 3 5.39 x 1 0 - 8 cc STP/gm
7.3 0.025 4.35x10-
Ar 38 /Ar 36 Ar 40 /Ar 36 Ar 36
0.450 ± 0 . 0 0 1 3143 ± 2 6 3.96 x I O " 9 cc STP/gm
0.23
Kr 80 /Kr 84 Kr 82 /Kr 84 Kr 83 /Kr 84 Kr 88 /Kr 84 Kr84
0.0423 ± 0 . 0 0 2 0.2048 ± 0 . 0 0 0 7 0.2045 ± 0 . 0 0 0 6 0.3058 ± 0 . 0 0 0 7 1.41 x l O - 1 0 cc STP/gm
Xe 1 2 4 /Xe 1 3 0 Xe 126 /Xe 130 Xe 128 /Xe 130 Xe 1 2 9 /Xe 1 3 0 Xe 131 /Xe 130 Xe 132 /Xe 130 Xe 134 /Xe 130 Xe 136 /Xe 130 Xe 130
0.0296 ± 0 . 0 0 0 2 0.0268 ± 0 . 0 0 0 2 0.508 ± 0 . 0 0 3 8.18 ±0.05 4.97 ±0.03 6.09 ±0.03 2.36 ±0.01 1.95 ±0.01 1 . 1 7 x 1 0 - " cc STP/gm
23 24 25
28
3.27x10
