J/ApJ/758/59 Nickel isotopes in meteorites (Steele+, 2012)
Neutron-poor nickel isotope anomalies in meteorites.
Steele R.C.J., Coath C.D., Regelous M., Russell S., Elliott T.
<Astrophys. J., 758, 59 (2012)>
=2012ApJ...758...59S 2012ApJ...758...59S
ADC_Keywords: Abundances ; Solar system
Keywords: astrochemistry; meteorites, meteors, meteoroids; methods: analytical;
nuclear reactions, nucleosynthesis, abundances; protoplanetary disks
Abstract:
We present new, mass-independent, Ni isotope data for a range of bulk
chondritic meteorites. The data are reported as
εg60Ni58/61, {x3b5}62Ni58/61, and
εg64Ni58/61, or the parts per ten thousand deviations from
a terrestrial reference, the NIST SRM 986 standard, of the
58Ni/61Ni internally normalized 60Ni/61Ni, 62Ni/61Ni, and
64Ni/61Ni ratios. The chondrites show a range of 0.15, 0.29, and
0.84 in εg60Ni58/61, {x3b5}62Ni58/61, and
εg64Ni58/61 relative to a typical sample precision of
0.03, 0.05, and 0.08 (2 s.e.), respectively. The carbonaceous
chondrites show the largest positive anomalies, enstatite chondrites
have approximately terrestrial ratios, though only EH match Earth's
composition within uncertainty, and ordinary chondrites show negative
anomalies. The meteorite data show a strong positive correlation
between εg62Ni58/61 and {x3b5}64Ni58/61, an
extrapolation of which is within the error of the average of previous
measurements of calcium-, aluminium-rich inclusions. Moreover, the
slope of this bulk meteorite array is 3.003±0.166 which is within
the error of that expected for an anomaly solely on 58Ni. We also
determined to high precision (∼10 ppm per AMU) the mass-dependent
fractionation of two meteorite samples which span the range of
εg62Ni58/61 and {x3b5}64Ni58/61. These analyses show
that "absolute" ratios of 58Ni/61Ni vary between these two samples
whereas those of 62Ni/61Ni and 64Ni/61Ni do not. Thus, Ni
isotopic differences seem most likely explained by variability in the
neutron-poor 58Ni, and not correlated anomalies in the neutron-rich
isotopes, 62Ni and 64Ni. This contrasts with previous inferences
from mass-independent measurements of Ni and other transition elements
which invoked variable contributions of a neutron-rich component. We
have examined different nucleosynthetic environments to determine the
possible source of the anomalous material responsible for the isotopic
variations observed in Ni and other transition elements within bulk
samples.
Description:
Nickel isotope data from suite of seven carbonaceous chondrites (CCs),
three enstatite chondrites, and seven ordinary chondrites (OCs) are
presented, see Table 1. The methods used to collect these data are
outlined in the Appendix and Steele et al. (2011GeCoA..75.7906S 2011GeCoA..75.7906S).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 125 37 Mass-dependent and mass-independent Ni isotope data,
reported relative to NIST SRM 986, for chondrites
and terrestrial materials
table3.dat 35 215 Analyses for which all five isotopes were measured
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See also:
J/ApJ/758/45 : Isotopic Sr abundances in meteorites (Moynier+, 2012)
J/ApJS/156/105 : Transitions in L-shell ions of Fe and Ni (Gu+, 2005)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 23 A23 --- Set Group of materials
25- 43 A19 --- Name Sample name
45 A1 --- f_Name [+rs*] Origin of sample (1)
47- 49 A3 --- Class Chemical group
51- 60 A10 --- NHM Natural History Museum number
62- 63 I2 --- n62 [4/72]? Number of analyses for 62Ni (2)
65- 66 I2 --- n64 [4/50]? Number of analyses for 64Ni (2)
68- 73 F6.3 [-] e60Ni [-0.2/0.01] ε60Ni58/61 (3)
75- 79 F5.3 [-] e_e60Ni [0.006/0.04] e60Ni 2-σ error
81- 86 F6.3 [-] e62Ni [-0.2/0.3] ε62Ni58/61 (3)
88- 92 F5.3 [-] e_e62Ni [0.01/0.07] e62Ni 2-σ error
94- 99 F6.3 [-] e64Ni [-0.4/0.6] ε64Ni58/61 (3)
101-105 F5.3 [-] e_e64Ni [0.02/0.2] e64Ni 2-σ error
107-112 F6.3 [-] 60/58Ni [-0.7/0.4]? δ60/58Ni
113 A1 --- f_60/58Ni [a] Flag on 60/58Ni (4)
115-119 F5.3 [-] e_60/58Ni [0.02/0.1]? 60/58Ni 2-σ standard error
121-125 A5 --- Samp Abbreviated name in Sample column in table 3
(Column added by CDS)
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Note (1): Flag as follows:
+ = Meteorite samples dissolved and initially processed by Regelous et al.
(2008E&PSL.272..330R 2008E&PSL.272..330R); before analysis, these solutions were passed
through anionic exchange resin (see Steele et al. 2011GeCoA..75.7906S 2011GeCoA..75.7906S)
in order to remove residual Zn.
r = NIST SRM 361 and JP-1 have been processed both by Regelous et al.
(2008E&PSL.272..330R 2008E&PSL.272..330R) and during this study.
s = The estimate for the bulk silicate Earth (BSE) is taken from Steele
et al. (2011GeCoA..75.7906S 2011GeCoA..75.7906S).
* = Objects of table 5 from Steele et al. 2011GeCoA..75.7906S 2011GeCoA..75.7906S; added by CDS.
Note (2): The values in columns "n62" and "n64" correspond to nxi and
nyi, respectively, with x and y refer to ε62Ni58/61
and ε64Ni58/61, respectively. See section A.2.1.
Note (3): The data show a range of 0.15, 0.29 and 0.84 parts per ten
thousand in ε60Ni58/61, ε62Ni58/61, and
ε64Ni58/61, respectively, where εiNi58/61 is
the parts per ten thousand difference in the iNi/61Ni ratio,
internally normalized to 58Ni/61Ni, relative to the NIST SRM 986
standard.
Note (4):
a = Mass-dependent δ60/58Ni data published by Cameron et al.
(2009PNAS..10610944C 2009PNAS..10610944C).
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Sample Sample name and number (separated by underscore=
11- 16 F6.3 [-] e62Ni [-0.2/0.3] Part per ten thousand difference
in the 62Ni/61Ni ratio (1)
18- 22 F5.3 [-] e_e62Ni [0.042] One standard deviation of e62Ni (2)
24- 29 F6.3 [-] e64Ni [-0.5/0.7] Part per ten thousand difference
in the 64Ni/61Ni ratio (1)
31- 35 F5.3 [-] e_e64Ni [0.082] One standard deviation of e64Ni (2)
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Note (1): Internally normalized to 58Ni/61Ni, relative to NIST SRM 986.
Note (2): The correlation coefficient between the errors in e62Ni and
e64Ni is 0.68.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 07-Jul-2014