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Potential interferences on monoisotopic 93 Nb are presented in Fig. A2.10, and are very similar to those described for 91 Zr. This is due to the substitution of the 37 Cl isotope for 35 Cl in the Fe and Ca molecular species listed above (i.e., 56 Fe 37 Cl and 40 Ca 16 O 37 Cl). Unlike Zr, Nb offers no additional isotope for analysis, and the low natural abundance of Nb exacerbates the problem of interfering species due to major elements. Accurate Nb analyses are unlikely in Fe- and Ca-rich rock types, unless the use of HCl is avoided. However, as discussed in Section 7.1 of the main text, Nb is unstable in pure HNO 3 acid matrices, and the presence of HCl stabilizes Nb, as well as other HFSE like Ta, in solution long enough for accurate ICPMS measurements. As mentioned previously, future work examining the optimum acid matrix for ICPMS determinations of Nb and Ta is recommended. The last element that appears to suffer from major element interferences is Mo, and in particular Mn interferences on the 95 Mo isotope (Fig. A2.11). Similarly to the Ca-Ar interferences on 88 Sr, Mn affects measured intensities for 95 Mo regardless of the acid matrix. This is apparently due to the 55 Mn 40 Ar molecular species, which forms independently of the bulk solution composition. Whereas the use of HCl appears to suppress 55 Mn 40 Ar formation (Fig. A2.11), the magnitude of the interference is significant regardless of the acid matrix (e.g., ~3-6 mg/kg at 20-30% MnO). It is therefore recommended that the 97 Mo isotope be used for Mo determinations in rock samples that contain more than a few percent MnO, unless Mo concentrations in the sample are the range of 50 to hundreds of mg/kg. 67
20000 0.5 M HCl 10 9 interference on 60 Ni in sample solution (cps) 15000 10000 5000 CaO(H) + JDo-1 dolomite (2.9 mg/kg Ni) MgCl + 8 7 6 5 4 3 2 interference on 60 Ni in sample powder (mg/kg) 1 0 0 0 10 20 30 40 50 60 70 80 90 100 MgO, CaO in sample powder (wt.%) Figure A2.1. Interferences observed at mass 60 (Ni) in 0.5 M HCl due to sample Mg and Ca content. JDo-1 contains 18.4% MgO and 34.0% CaO, effectively prohibiting in carbonate rocks determinations of Ni concentrations that are similar to JDo-1 (2.9 mg/kg Ni). 15000 18 16 interference on 60 Ni in sample solution (cps) 10000 5000 0.5 M HNO 3 JDo-1 dolomite (2.9 mg/kg Ni) CaO(H) + 14 12 10 8 6 4 interference on 60 Ni in sample powder (mg/kg) N 2 O 2 + (?) 2 0 0 0 10 20 30 40 50 60 70 80 90 100 MgO, CaO in sample powder (wt.%) Figure A2.2. Interferences observed at mass 60 (Ni) in 0.5 M HNO 3 due to sample Mg and Ca content. Use of HNO 3 effectively removes MgCl interference, but does not affect the dominant CaO(H) interference. 68
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Iron sedimentation and the neodymiu
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The process(es) by which IFs were d
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This thesis represents original and
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viii
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goal of the research is to discern
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Figure 1. Map of southern Africa sh
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appropriate to briefly discuss: 1)
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100 10 MORB 1 0.1 raw data (mg/kg)
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10 -2 hydrothermal fluid 10 -3 10 -
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seawater and returned to the sedime
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100 MCO + 3 + M(CO 3 )- 2 rare eart
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net effect of carbonate complexatio
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feature was not recognized in early
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sound geochemical basis for anomalo
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deviation of the 143 Nd/ 144 Nd rat
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available, it should be possible to
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modern and Archean oceans, as well
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Bau M., Möller P., and Dulski P. (
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Elderfield H. and Greaves M.J. (198
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Haley B.A., Klinkhammer G.P. (2003)
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Lee J.H. and Byrne R.H. (1993) Comp
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Piepgras D.J. and Wasserburg G.J. (
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Tosiani T., Loubet M., Viers J., Va
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THIS PAGE INTENTIONALLY LEFT BLANK
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Abstract The benefits of inductivel
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List of Figures Figure 1. Sample de
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1. Introduction The advent of induc
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Figure 1. Flow-chart diagram of the
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during decomposition (SiF 4 and CO
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Fractionation between the three iso
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cps, then 3000 cps must be subtract
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variety of ways. These range from r
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Table 3. Change in HFSE concentrati
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0.90, corresponding to an anomalous
Page 72 and 73: 10 2 JDo-1 reference values 10 1 IF
Page 74 and 75: Figure 5. Diagram depicting various
Page 76 and 77: 20 18 basalt BHVO-2 (n=5) run preci
Page 78 and 79: The method precision for elements p
Page 80 and 81: Two approaches may be utilized to d
Page 82 and 83: For the more recent, full 32 elemen
Page 84 and 85: isotopic data for geologic CRMs, av
Page 86 and 87: Table 4. Interferences observed for
Page 88 and 89: value uncertainty (as %RSD) is repr
Page 90 and 91: 1.50 FeR-4 (n=2) 1.25 JUB / referen
Page 92 and 93: 1 IF-G/shale 0.1 0.01 La Ce Pr Nd P
Page 94 and 95: consistent (App. 1), and similar to
Page 96 and 97: 1.50 SGR-1b (n=3) 1.25 JUB / refere
Page 98 and 99: 1.50 JCh-1 (n=3) 1.25 JUB / referen
Page 100 and 101: 1.50 JDo-1 (n=5) 1.25 JUB / referen
Page 102 and 103: determinations in carbonate rocks r
Page 104 and 105: 1.50 JMn-1 (n=4) 1.25 JUB / referen
Page 106 and 107: eference value. The result is that
Page 108 and 109: eference value and the measured JUB
Page 110 and 111: the 32 analyzed elements, with Ti b
Page 112 and 113: Govindaraju K. (1995) 1995 working
Page 114 and 115: Appendix 1. Analytical data Appendi
Page 116 and 117: Appendix 1. Literature reference va
Page 118 and 119: Appendix 1 continued. Data in mg/kg
Page 120 and 121: the concentration of the major elem
Page 124 and 125: 1500 0.5 M HCl 4.0 interference on
Page 126 and 127: 4000 0.40 0.20 3500 0.17 mg/kg 0.18
Page 128 and 129: interference on 95 Mo in sample sol
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Page 132 and 133: Nd isotopes in 2.9 Ga Archean surfa
Page 136 and 137: Table 2 Trace element concentration
Page 152 and 153: Author's personal copy B.W. Alexand
Page 166 and 167: and preservation of oxide-facies IF
Page 168 and 169: TOP relative stratigraphic position
Page 170 and 171: The mechanism by which the alkali m
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6. Widdel, F. et al. Ferrous iron o
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82 PRESERVATION OF PRIMARY REE PATT
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ulk, open ocean seawater tended to
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