Europium anomaly

Figure 9.9 REE abundances from archaeological glass, showing the effect of chondrite normalization, (a) shows the raw abundances of the REE measured on a set of English medieval window glasses, with the saw-tooth pattern evident, and little indication of differences between any of the samples (apart from perhaps one which has lower overall REE concentrations), (b) shows the same data normalized to the chondrite data (Table 9.1). The saw-tooth has largely disappeared, and close inspection suggests that two samples have a positive europium anomaly, possibly indicating a different geographical origin.

Chondrite-normalized REE profiles (Fig. 1) for massive sulfides exhibit a prominent enrichment in LREE and Eu. The enrichment of LREE over the HREE is substantiated by strong positive REE correlations with La, Ce, Pr, Nd and Sm, and a (La/Lu)N ranging widely from 0.15 to 387. Europium anomalies are distinctly positive with (Eu/Eu )n averaging 4.7, but vary widely, ranging from 0.21 to 36. Minor negative Eu anomalies occur in semi-massive sulfides, due to dilution by volcaniclastic material. A positive... 

One of the most striking findings during the analyses of the first lunar samples was the large negative europium anomaly found in all mare basalts29-31) and later in the KREEP samples, too (Fig. 10). 

As illustrated in Fig. 10, europium anomalies are found not only in lunar samples but also, for example, in the silicate phase of mesosiderites. This is strong evidence that these meteorites have undergone extensive magmatic fractionation. Of course, a low partial pressure of oxygen is required in order to keep europium in the 2+ state. 

NWA Oil is basaltic in composition, with enrichments in aluminum, calcium, and titanium relative to chondrites, and is ferroan, with an mg of 36. NWA 011 has a cumulate-eucrite-like REE pattern (Figure 6). However, Afanasiev et al. (2000) report that NWA Oil has a negative europium anomaly and samarium content of 13.3 X Cl, more like those expected for a mafic melt composition. Yamaguchi et al. (2002) suggest that the heterogeneous distribution of calcium phosphate is the likely explanation for this discrepancy. This is supported by their hafnium and tantalum analyses, which are at 12.8 X Cl and... 

Mittlefehldt D. W., Rubin A. E., and Davis A. M. (1992) Mesosiderite clasts with the most extreme positive europium anomalies among solar system rocks. Science 257, 1096-1099. 

Brophy J. G. and Basu A. (1990) Europium anomalies in mare basalts as a consequence of mafic cumulate fractionation from an initial lunar magma. Proc. 20th Lunar Planet Sci. Conf, 25-30. 

McKay G., Le L., and Wagstaff J. (1991) Constraints on the origin of the mare basalt europium anomaly REE partition coefficients for pigeonite. In Lunar Planet. Sci. XXII. The Lunar and Planetary Institute, Houston, (CD-ROM), pp. 883-884. 

Figure 15). Conversely, the most REE-enriched sample from the Garret Transform shows a negative europium anomaly that might result from the entrapment of melt evolved after plagioclase fractionation. However, further assessment of this hypothesis is hampered by secondary alteration (Niu and Hekinian, 1997a).

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