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Figure 5. Diagram depicting various types of precision that may be defined for sample decompositions and ICPMS analyses. Note that sample precision reflects raw uncorrected intensities (cps), while run and method precision are calculated from corrected concentration data. that of the sample precision for many elements, and also varies as function of rock type (Fig. 7). Shales display slightly poorer run precision (3-5%), though this might reflect the limited number of analyses where these CRMs were measured repeatedly. For purposes of long term reproducibility, the method precision is the most suitable measure of the standard deviation expected for a complete sample decomposition and ICPMS analyses, as it describes the variability expected in concentration data when a sample powder is dissolved numerous times over a period of months or years. Comparisons of the three types of precision discussed here (sample, run, and method) are presented in Figure 8 for CRMs of four different rock types. Of the 32 elements analyzed, the method precision RSD is better than 5% for 25 elements in BHVO-2 (basalt), 31 elements in SGR-1b, 26 elements in FeR-2 (iron-formation), and 22 elements in JDo-1 (dolomite). The method precision is also comparable to the sample and run precision, suggesting that any error associated with the HF-HClO 4 sample decomposition method (e.g., weighing and/or dilution errors) is small compared to the error inherent in the ICPMS analysis. 19
sample precision (%RSD) 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 BHVO-2 (n=5) 10 μg/kg calibration standard 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 Sc-45 Ti-47 Ti-49 Co-59 Ni-60 Ni-62 Rb-85 Sr-88 Y-89 Zr-90 Zr-91 Nb-93 Mo-95 Mo-97 Cs-133 Ba-135 Ba-137 La-139 Ce-140 Pr-141 Nd-145 Nd-146 Sm-147 Sm-149 Eu-151 Eu-153 Gd-158 Gd-160 Tb-159 Dy-161 Dy-163 Ho-165 Er-166 Er-167 Tm-169 Yb-171 Yb-172 Yb-174 Lu-175 Hf-178 Hf-179 Ta-181 W-182 W-183 Pb-206 Pb-207 Pb-208 Th-232 U-238 Sc-45 Ti-47 Ti-49 Co-59 Ni-60 Ni-62 Rb-85 Sr-88 Y-89 Zr-90 Zr-91 Nb-93 Mo-95 Mo-97 Cs-133 Ba-135 Ba-137 La-139 Ce-140 Pr-141 Nd-145 Nd-146 Sm-147 Sm-149 Eu-151 Eu-153 Gd-158 Gd-160 Tb-159 Dy-161 Dy-163 Ho-165 Er-166 Er-167 Tm-169 Yb-171 Yb-172 Yb-174 Lu-175 Hf-178 Hf-179 Ta-181 W-182 W-183 Pb-206 Pb-207 Pb-208 Th-232 sample precision (%RSD) U-238 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 SGR-1b (n=2) 10 μg/kg calibration standard sample precision (%RSD) FER-2 (n=3) 10 μg/kg calibration standard 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 Sc-45 Ti-47 Ti-49 Co-59 Ni-60 Ni-62 Rb-85 Sr-88 Y-89 Zr-90 Zr-91 Nb-93 Mo-95 Mo-97 Cs-133 Ba-135 Ba-137 La-139 Ce-140 Pr-141 Nd-145 Nd-146 Sm-147 Sm-149 Eu-151 Eu-153 Gd-158 Gd-160 Tb-159 Dy-161 Dy-163 Ho-165 Er-166 Er-167 Tm-169 Yb-171 Yb-172 Yb-174 Lu-175 Hf-178 Hf-179 Ta-181 W-182 W-183 Pb-206 Pb-207 Pb-208 Th-232 U-238 Sc-45 Ti-47 Ti-49 Co-59 Ni-60 Ni-62 Rb-85 Sr-88 Y-89 Zr-90 Zr-91 Nb-93 Mo-95 Mo-97 Cs-133 Ba-135 Ba-137 La-139 Ce-140 Pr-141 Nd-145 Nd-146 Sm-147 Sm-149 Eu-151 Eu-153 Gd-158 Gd-160 Tb-159 Dy-161 Dy-163 Ho-165 Er-166 Er-167 Tm-169 Yb-171 Yb-172 Yb-174 Lu-175 Hf-178 Hf-179 Ta-181 W-182 W-183 Pb-206 Pb-207 Pb-208 Th-232 U-238 sample precision (%RSD) JDo-1 (n=3) 10 μg/kg calibration standard 23.0% Figure 6. Average sample precision (see text for definition) for different rock types dissolved using the HF-HClO 4 decomposition, as calculated from the number (n) of decompositions where the CRM was measured repeatedly. The average 10 μg/kg calibration standard is presented for comparison (n=19). Precision is generally very similar between the rock solutions and the calibration standard, except for elements that are present at low concentrations in trace-metal poor rocks such as the JDo-1 dolomite (e.g., Rb, Mo, Cs, Hf, Th, U). This suggests that the standard deviation of ICPMS measurements is controlled by inherent instrument precision rather than by sample matrix effects. 20
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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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Page 42 and 43: Haley B.A., Klinkhammer G.P. (2003)
Page 44 and 45: Lee J.H. and Byrne R.H. (1993) Comp
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Page 52 and 53: Abstract The benefits of inductivel
Page 54 and 55: List of Figures Figure 1. Sample de
Page 56 and 57: 1. Introduction The advent of induc
Page 58 and 59: Figure 1. Flow-chart diagram of the
Page 60 and 61: during decomposition (SiF 4 and CO
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Page 64 and 65: cps, then 3000 cps must be subtract
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Page 68 and 69: Table 3. Change in HFSE concentrati
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Page 80 and 81: Two approaches may be utilized to d
Page 82 and 83: For the more recent, full 32 elemen
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Page 86 and 87: Table 4. Interferences observed for
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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
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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
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Page 122 and 123: Potential interferences on monoisot
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1500 0.5 M HCl 4.0 interference on
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4000 0.40 0.20 3500 0.17 mg/kg 0.18
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interference on 95 Mo in sample sol
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Nd isotopes in 2.9 Ga Archean surfa
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Table 2 Trace element concentration
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Author's personal copy B.W. Alexand
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and preservation of oxide-facies IF
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TOP relative stratigraphic position
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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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