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Table 2 Trace element concentrations in iron-formation and shale samples (mg/kg) Iron-formation samples Shale samples WM41 WM42 WM51 WM52 WM61 WM62 WM71 WM72 WM101 WM102 WM111 WM112 WM121 WM122 WM131 WM132 WM2 WM8 WM18 WM19 pelite a Rb
384 B.W. Alexander et al. / Geochimica et Cosmochimica Acta 72 (2008) 378–394 considerably lower (average 1.13). The REY patterns are not correlated with major element chemistry, nor with immobile trace element content, but the two groups of patterns can be distinguished on the basis of relative stratigraphic position; i.e., high (Dy/Yb) WMS corresponds to samples collected at the base and at the top of the sequence REY/WMS REY/WMS 1 0.1 0.01 0.001 1 0.1 0.01 top of sequence bottom of sequence La Ce Pr Nd Pm Sm Eu Gd Tb Dy Y Ho Er Tm Yb Lu middle of sequence WM42 WM132 WM131 WM62 WM61 WM52 WM51 WM42 WM41 WM122 WM121 WM112 WM111 WM102 WM101 WM72 WM71 studied, and low (Dy/Yb) WMS is found in samples collected from the middle of the sequence. The REY patterns of all the IF samples exhibit WMSnormalized positive La, Eu, and Gd anomalies. Calculated (La/La * ) WMS and (Gd/Gd * ) WMS are above unity for all 16 IF samples (Fig. 3), and (Eu/Eu * ) WMS ranges from 1.51 to 2.09 (average 1.69). The magnitude of the La, Eu, and Gd anomalies are indistinguishable on the basis of stratigraphic position. Y/Ho averages 42 for all samples, and higher Y/ Ho values are observed for samples collected from the middle of the sequence, though the difference between the two groups is small when samples WM121 and WM122 (Y/Ho of 61 and 66, respectively) are not considered. The REY pattern of sample WM42 is similar to samples obtained stratigraphically above and below it, possessing positive La, Gd, and Y anomalies. The RREY content is the highest of the IF samples, and though most major element concentrations for sample WM42 are comparable to the other IF samples, Al 2 O 3 is enriched at 1.2% and MnO is significantly higher (14.5%). WM42 also contains somewhat greater concentrations of Rb, and significantly more Zr, Hf and Th than any of the other 15 IF samples. Seven iron-formation samples and three shale samples were analyzed using TIMS, and Nd and Sm isotope data are presented in Table 3. Six of the samples (one shale and five IF samples) display similar 147 Sm/ 144 Nd between 0.1164 and 0.1486, values common to other Archean shales and iron formation (e.g., Miller and O’Nions, 1985; Alibert and McCulloch, 1993; Jahn and Condie, 1995; Bau et al., 1997). Of the remaining four samples, two are iron formations displaying the highest 147 Sm/ 144 Nd observed (>0.17), whereas the lowest 147 Sm/ 144 Nd values are observed in the remaining two shale samples (
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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
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10 2 JDo-1 reference values 10 1 IF
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Figure 5. Diagram depicting various
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20 18 basalt BHVO-2 (n=5) run preci
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The method precision for elements p
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Two approaches may be utilized to d
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For the more recent, full 32 elemen
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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 122 and 123: Potential interferences on monoisot
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
Page 130 and 131: THIS PAGE INTENTIONALLY LEFT BLANK
Page 132 and 133: Nd isotopes in 2.9 Ga Archean surfa
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
Page 172 and 173: 6. Widdel, F. et al. Ferrous iron o
Page 178 and 179: 82 PRESERVATION OF PRIMARY REE PATT
Page 184: ulk, open ocean seawater tended to
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