Ce anomaly

Negative Ce anomaly is observed for hydrothermally altered chlorite-rich basalt overlying the Kuroko ores. 

Negative Ce anomaly and positive Eu anomaly are observed for epidote-rich altered basalt near the orebody. 

The REE pattern for the Nishikurosawa exhibits slightly light REE enriched one (La/Yb = 0.55 0.09) and plots elose to the line of NASC normalized value = 1. Positive Ce anomaly is also found in the Nishikurosawa. This anomaly is defined by the following equation. 

In this section, Ishikawa (1996), and Kashiwagi et al. (2000) studies are described. Then, their calculated results are given, emphasizing the influence of hydrothermal and volcanic gas CO2 flux from back arc basins and island arc on CO2 concentration of atmosphere and climate change and are compared with the changes in CO2 and temperature obtained by analytical and paleontological data (S 0 of foraminiferal shell, Ce anomaly, 5 C, etc.). 

Liu and Schmitt (1984, 1993a,b, 1996) and Liu et al. (1988) derived the relationship between the negative Ce anomaly of seawater and PcOj from thermochemical calculations. Liu and his coworkers estimated Pco2 variation during the last 120 Ma based on this method. Pco2 middle Miocene age estimated by Liu and his coworkers is high and seems to be consistent with that by Ishikawa (1996). However, Liu s method was criticized by Elderfield and Schultz (1987). Ce anomaly depends not only on Pco2> but on many other factors such as P02, pH and SCe. 

Liu Y.-G. and Schmitt, R.A. (1993a) Earth s partial pressure of CO2 over the past 120 Ma evidence from Ce anomalies in the deep (>60 m) Pacific ocean. Lunar Planet. Sci., XX IV, 883-884. 

The presence of °Be or negative Ce anomalies, or both, in some arc lavas provide unambiguous evidence for a contribution from subducted sediments to the source of arc lavas (Morris et al. 1990 Hole et al. 1984). In addition, Pb isotopes commonly are... 

Figure 8.38 Ce anomalies in normalized REE patterns of seawater at various depths. Reproduced with modifications from H. J. W. DeBaar, M. R Bacon, P. G. Brewer, and K. W. Bruland, Geochimica et Cosmochimica Acta, 49, 1943-1960, copyright 1985, with kind permission from Elsevier Science Ltd., The Boulevard, Langford Lane, Kidlington 0X5 1GB, UK.

Figure 8.38 shows that the anomalous concentration of Ce results in a positive Ce anomaly in normalized REE patterns (relative abundances arranged in order of increasing atomic number). This anomaly, which may be ascribed to scavenging by Mn-Fe hydroxides, decreases progressively and inverts with depth. 

Debaar H. J. W., Bacon M. P., and Brewer P. G. (1983) Rare-earth distributions with a positive Ce anomaly in the western North-Atlantic Ocean. Nature 301(5898), 324-327. 

Figure 6 REE distribution for major Mn ore deposits shows variable Eu and Ce anomalies (source Table 2).

In the Spring Valley and Shavi Members, sedi-mentological facies (Bickle et al. 1975 Martin et al. 1980 Nisbet et al. 1993 Hunter et al. 1998) vary from beach to an assortment of shallow-water settings. REE patterns from oxide-facies ironstones have strong Eu anomalies, but no Ce anomalies. The Spring Valley and Shavi REE are most simply modelled as sediments deposited from water which included (1) ambient sea water of modem aspect but without a Ce anomaly, as well as (2) an admixed hydrothermal (modern black smoker or white smoker) component. The source of the REE may have been distant. 

In a similar way, calcite from the fault zone exhibits a unique REE pattern, with a marked positive Ce anomaly and a marked depletion in all heavy REEs (No. 7 in Fig. lOB), which does not resemble the patterns of other calcite samples. In agreement with O, C and Sr data, this confirms that the calcites in the fault and in the main blocks are not genetically linked. The REE patterns of calcite from the structural blocks are extremely variable, with any of the following features marked depletion in heavy REEs extreme depletion in light REEs enrichment in middle REEs marked positive Ce anomaly and small positive Gd anomaly (Fig. 10B,C). Different calcite-cemented intervals in the same well or in different wells generally... 

The typical REE pattern of end-member hydrothermal fluids exhibits a strong enrichment of TREE and a pronounced positive Eu anomaly (Michard et al. 1983 Campbell et al. 1988c Michard 1989 Fig. 13.12), in contrast to the source rocks (MORE) which have a nearly flat, TREE depleted spectrum, and to seawater which is characterized by a strong negative Ce anomaly. The overall pattern is strongly influenced by leaching of plagioclase from MORE under hydrothermal conditions. 

Wright et al. (1984) determined REE composition of hundreds of individual conodonts and ichthyoliths, and found consistent REE shapes in pre-Carboniferous conodonts, with enrichment of MREE, lesser enrichment of TREE, and no cerium anomaly. This pattern is fundamentally different to the REE pattern found in modem ocean bottom waters, and led Wright et al. (1984) to suggest that the REE chemistry and particularly Ce anomaly in ancient marine apatites could be used to infer widespread anoxia in pre-Carboniferous ocean basins. 

German C R, Elderfield H (1990) Application of the Ce anomaly as a redox indicator The ground rules. Paleoceanography 5 823-833... 

In the aoxic basins, Ce" " " is reduced to Ce " " and the Ce-anomaly tends to be smaller than those in oxygenated waters. The Black Sea provides a best example in which Ce/Ce sharply increases from less... 

Figure 7 The vertical profiles of Ce-anomaly calculated from the profile data in Figure 3.

Figure 8 The vertical profiles of La, Ce, and Nd (A) and calculated Ce-anomaly (B) in the Black Sea. After German eta/. (1991).

Fig. 34. Lanthanide ibundance pattern for river water (data are from table 19). Note the higher abundances and lack of Ce anomaly, compared to seawater (fig. 33). In general, the pattern is nearly parallel to that of the upper continental crust.

For typical marine pH s (about 8), Eh values of about 0.15-0.45 V would probably be required (see review of Addy 1979). This suggests that Ce anomalies should only be found in nodules formed in quite oxidised sediments, an observation substantiated by the limited body of data (Addy 1979). 

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