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net effect of carbonate complexation in solution and particle surface adsorption for the REY is that heavier rare earth elements tend to remain in solution, and conversely, the LREE partition more easily onto particle surfaces. The result is a generally monotonic increase in shale-normalized rare earth element concentrations in seawater as a function of increasing atomic mass. However, as seen in Figs. 4-6, some elements in the REY series display anomalous behavior relative to their immediate neighbors. The most strikingly anomalous element among the lanthanides is Ce, which, as mentioned previously, can exist in the Ce 4+ valence state in oxic marine systems. Experimental work has demonstrated that when lanthanides are adsorbed onto Mnoxides and Fe-oxyhydroxides, positive Ce anomalies develop in the solid phases, which have been attributed to the oxidation of Ce(III) to highly insoluble Ce(IV) on mineral surfaces (e.g., Koeppenkastrop and De Carlo, 1992; Bau, 1999). Positive Ce anomalies have also been noted in marine hydrogenetic Fe-Mn crusts (e.g., Bau et al., 1996, and references therein), consistent with the oxidation of adsorbed Ce(III) to Ce(IV) and the preferential retention of Ce on metal-oxyhydroxide surfaces in the marine environment. It should be noted that this fractionation of Ce is not observed under anoxic conditions, and the REY patterns of seawater sampled from anoxic basins do not display negative Ce anomalies (e.g., de Baar et al., 1988; German et al., 1991b; Bau et al., 1997b). The other rare earth element that displays strongly anomalous behavior in seawater is Y, which is highly enriched relative to neighboring Dy and Ho (Figs. 4-6). While the ionic radii of Y is similar to Ho, and these elements are considered to be geochemical twins that exhibit similar behavior in most geological processes, Y is strongly fractionated from Ho (and the other lanthanides) in seawater. Relative to Ho, carbonate complexation constants for Y in seawater are similar for moncarbonate species, and somewhat different for dicarbonate species (Luo and Byrne, 2004). 16
10 2 world seawater (x10 8 ) sample/PAAS 10 1 10 0 hydrogenetic Fe-Mn crust La Ce Pr Nd PmSm Eu Gd Tb Dy Y Ho Er Tm Yb Lu Figure 8. Comparison of REY patterns in average world seawater (data same as Fig. 4) and average (n=12) non-phosphatized hydrogenetic Fe-Mn crusts from the central Pacific Ocean (data from Bau et al., 1996). Note complementary Ce and Y anomalies between seawater and precipitated Fe-Mn oxide particles as represented by Fe-Mn crust. However, the strong positive Y anomaly observed in seawater results from particle surface complexation effects, as Y adsorbed to particle surfaces is bound less strongly than the lanthanide elements (e.g., Bau, 1999). The significant fractionation of both Y and Ce from the other REY in seawater due to processes occurring on particle surfaces is clearly evident in the REY patterns for hydrogenetic Fe-Mn crusts as shown in Figure 8. This does not imply that hydrogenetic Fe-Mn crusts are solely responsible for these anomalies, as Ce and Y fractionation has been observed to develop as a function of increasing salinity in estuaries (Lawrence and Kamber, 2006). It therefore appears that significant Ce and Y anomalies begin to form during mixing of river waters and seawater, and may be present in the truly dissolved REY fraction of river waters (Byrne and Liu, 1998). Of the remaining REY, La, Gd, and Lu display anomalous behavior in seawater to varying degrees. Strong positive La anomalies are typical of seawater, though this 17
Page 1: Iron sedimentation and the neodymiu
Page 4 and 5: The process(es) by which IFs were d
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Page 18 and 19: 100 10 MORB 1 0.1 raw data (mg/kg)
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Page 52 and 53: Abstract The benefits of inductivel
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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
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Table 4. Interferences observed for
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value uncertainty (as %RSD) is repr
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1.50 FeR-4 (n=2) 1.25 JUB / referen
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1 IF-G/shale 0.1 0.01 La Ce Pr Nd P
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consistent (App. 1), and similar to
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1.50 SGR-1b (n=3) 1.25 JUB / refere
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1.50 JCh-1 (n=3) 1.25 JUB / referen
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1.50 JDo-1 (n=5) 1.25 JUB / referen
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determinations in carbonate rocks r
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1.50 JMn-1 (n=4) 1.25 JUB / referen
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eference value. The result is that
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eference value and the measured JUB
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the 32 analyzed elements, with Ti b
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Govindaraju K. (1995) 1995 working
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Appendix 1. Analytical data Appendi
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Appendix 1. Literature reference va
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Appendix 1 continued. Data in mg/kg
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the concentration of the major elem
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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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