Isotopic Measurements with the
Cameca ims 1280 Ion Microprobe at
the University of Hawai‘i
Gary R. Huss, Kazu Nagashima, Sasha Krot,
Kentaro Makide, and Lydie Bonal
W. M. Keck Cosmochemistry Laboratory
University of Hawai‘i at Manoa
Isotopic Systems Studied at UH
•
•
•
•
•
•
•
•
Oxygen isotopes*
26Al-26Mg systematics*
60Fe-60Ni systematics*
53Mn-53Cr systematics
Carbon isotopes
Nitrogen isotopes
Hydrogen isotopes
Isotope ratio imaging (scanning ion imaging)
Oxygen Isotopes
•
•
•
•
•
CAIs from CR, CH, CV chondrites*
FUN CAIs from CV chondrites*
Carbonates from lithic clasts in Isheyevo
Type II chondrules from CR chondrites
Chondrules from CH and CB chondrites
Oxygen Isotopes in FUN CAIs
Data from Clayton et al. (1977, EPSL 34, 209), Clayton et al. (1977, GRL 4, 295), Lee et al.
(1980, GRL 7, 493), Clayton et al. (1984, GCA 48, 535), McKeegan et al. (2005, LPSC 36, 2077).
Oxygen Isotopes in FUN CAIs
DH8 (Type B), Allende
Normal CAIs from CR chondrites
KT-1 (Type B), NWA 779
Makide et al. (2008)
Krot et al. (2008)
Oxygen Isotopes: Standards
• Standards are critically important for calibrating
•
instrumental mass fractionation (IMF) and
determining accurate oxygen isotopic compositions
At UH, we have standards for
–
–
–
–
–
–
Olivines of several compositions
Spinel
Pyroxenes of several compositions
Quartz*
Garnet*
Calcite*, dolomite*, siderite*
* Many of these generously provided by the WiscSIMS Laboratory
Oxygen Isotopes: Standards
• We need or are working on standards for
–
–
–
–
–
–
–
Melilite or melilite glass of several compositions
Ca-Al oxides
Wollastonite
Intermediate olivines
Tochilinite
Magnetite
Magnesite
• When we develop a standard, we will try to
prepare enough to share with other SIMS labs.
26Al-26Mg
•
•
•
•
•
Systematics
CAIs from CR chondrites*
CAIs from CV chondrites*
FUN CAIs from CV chondrites
Chondrules from CR chondrites
Chondrules from ordinary chondrites
26Al-26Mg
Systematics
Compact Type A CAI, 2-A1 from Kaba (CV3)
40
(26Al/27Al)0=(4.95±0.62)x10-5
35
26Mg* (‰)
30
25
20
15
10
5
26Mg)0= 0.47±0.76
0
-5
0
20
40
60
27Al/24Mg
Nagashima et al. (2007)
80
100
26Al-26Mg
Systematics: Improving the
Precision of the Isochron
• High sensitivity of 1280 can improve precision
• Employ multicollection where possible
• Automated beam centering and careful
•
measurement protocol improves reproducibility
Correct instrumental mass fractionation (IMF) and
account for intrinsic mass fractionation separately
– Correct IMF using standard-sample bracketing
– Calculate 26Mg* using appropriate fractionation law
• Use appropriate standards to correct for relative
sensitivities of Al and Mg
Al-Mg Sensitivity Factors
Makide et al. (2008)
Mass Fractionation of Magnesium
Makide et al. (2008)
Measuring of Mass Fractionation of Mg
• Good statistical precision
• Good sample preparation
• Measure samples and standards with the same
•
•
primary beam current and shape and with same
measurement time.
Tight control over ion extraction and beam path in
secondary ion mass spectrometer
Well-characterized, matrix-matched standards to
estimate IMF and point-to-point variability
– Demonstrated long-term reproducibility
• Residual uncertainty: Do samples and standards
behave in precisely the same way?
26Al-26Mg:
Standards
• Isotopically characterized, matrix-matched standards
for Mg isotopes to determine instrumental and
intrinsic mass fractionation and to identify 26Mg*
– Assuming the published Mg composition for natural
samples may not be enough
• Matrix-matched standards for relative sensitivity
•
factors
Complete suite for cosmochemistry should include
–
–
–
–
–
Spinel, hibonite, Ca-Al oxides
Olivines and pyroxenes of various compositions
Melilites of various compositions
Plagioclase (with Al/Mg ~ 100)
Glasses of different compositions
60Fe-60Ni
•
•
•
•
Systematics
Sulfides from ordinary chondrites
Chondrules from ordinary chondrites*
Fayalite from CV chondrites
Chondrules from CR chondrites
60Fe-60Ni
Systematics: Sulfides in
Unequilibrated Ordinary Chondrites
Fe/Ni (x 10 4)
0
Krymka
5
10
15
20
8
8
12
12
6
16
16
25.5
25.5
24.5
24.5
60
60Ni/61Ni
Ni/ 61Ni
26.5
26.5
23.5
23.5
22.5
22.5
0
Tachibana and Huss
(2003)
0
4
456
61
Fe/ Ni (x 10 )
56Fe/61Ni (x106)
(60Fe/56Fe)0 = (1.81± 0.72)
x10-7
60Fe-60Ni
Systematics: Pyroxene Chondrules
in Unequilibrated Ordinary Chondrites
Tachibana et al. (2006)
(60Fe/56Fe)0 = (2.2~3.7) x 10-7
60Fe-60Ni
Systematics: Porphyritic
Chondrules in UOCs
0.1402
0.1400
60Ni/61Ni
/ 24Mg
0.1398
26Mg
23.6
(26Al / 27Al) 0 = (7.2 ± 2.7) x 10 -6
0.1396
0.1394
0.1392
23.4
23.2
23.0
0.1390
0
0.1388
0.1386
0
Semarkona 312 Chondrule 6
10
20
30
40
50
27Al / 24Mg
Huss et al. (2007)
0.2 0.4 0.6 0.8 1.0 1.2
56Fe/61Ni (x106)
(60Fe/56Fe)0 = (1.7 ± 1.1)
x10-7
Semarkona SMK3-6
Tachibana et al. (2007)
60Fe-60Ni
Systematics: Next Steps
• Improve precision of the data
– Develop multicollection (in progress)
– Higher transmission in secondary mass spectrometer
– Brute force (measure longer)
• Develop a complete suite of appropriate standards
• Find better samples to measure