Eu anomaly

Positive Eu anomaly is observed for barite, Kuroko ores, ferruginous chert (tet-susekiei), and hydrothermally altered basaltic and dacitic rocks overlying the Kuroko ores. 

Negative Eu anomaly is observed for hydrothermally altered dacite underlying the Kuroko ores and anhydrite in the dacitic tuff breccia. 

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

The REE pattern for fresh volcanic rocks in the Kuroko mine area studied by Dudas et al. (1983) is shown in Fig. 1.47 which shows no negative Ce and no positive Eu anomalies and FREE (Light Rare Earth Element) are not enriched compared with HREE... 

Heavy Rare Earth Element). Therefore, it is considered that negative Ce and positive Eu anomalies in hydrothermally altered volcanic rocks, Kuroko ores, and ferruginous chert and LREE enrichment in the Kuroko ores have been caused by hydrothermal alteration and precipitations of minerals from hydrothermal solution responsible for sulfides-sulfate (barite) mineralization. 

Negative Eu anomaly is also found in the fresh and altered dacitic rocks (Dudas et al., 1983). Therefore this negative anomaly in anhydrite is also explained in terms of an influence of sericitization of dacite accompanied by the depletion of Eu. 

Positive Eu anomaly is observed for hydrothermal solution issuing from the hydrothermal vent on the seawater at East Pacific Rise (Bence, 1983 Michard et al., 1983 Michard and AlbarMe, 1986). Guichard et al. (1979) have shown that the continental hydrothermal barites have a positive Eu anomaly, indicating a relatively reduced environment. Graf (1977) has shown that massive sulfide deposits and associated rocks from the Bathurst-Newcastle district. New Brunswick have positive Eu anomalies. These data are compatible with positive Eu anomaly of altered basaltic rocks, ferruginous chert and Kuroko ores in Kuroko mine area having positive Eu anomaly and strongly support that Eu is present as divalent state in hydrothermal solution responsible for the hydrothermal alteration and Kuroko mineralization. 

The REE characterics of calcite from the Au-Ag type are variable. For example, calcites from Sado Au-Ag vein, one of the largest Au-Ag deposits in Japan have both signatures of meteric water and magmatic (or igneous) contributions. Positive Eu anomaly is only found in caleite containing low REE from Au-Ag type (Seigoshi deposit) (Shikazono, unpublished). 

Hydrothermal solution venting from midocean ridges and back-arc basins has positive Eu anomaly (Klinkhammer et al., 1983 Miehard et al., 1983 Mitra, 1994 Shikazono, 1999a) (Fig. 1.158). Therefore, the positive Eu anomaly of the sedimentary rocks is thought to be due to a contribution of hydrothermal solution. In order to know the contribution of hydrothermal solution the positive Eu anomaly of seawater (Eu/Eujg gjgj.) is useful. 

A few REE data on hydrothermal solutions are available (Fig. 2.34). Chondrite normalized REE patterns of hydrothermal solutions from Vienna Wood, Pacmanus and Desmos, Manus Basin exhibit positive Eu anomaly and LREE enrichment are similar to midoceanic ridge solution and Kuroko ore fluids. This positive Eu anomaly (Fig. 2.35) may have been caused by the selective leaking of Eu due to the interaction of an ascending hydrothermal solution and footwall volcanic rocks (Gena et al., 2001). It is interesting to note that altered basaltic andesite has a negative Eu anomaly and this feature is the same as that found in the Kuroko mine area (Shikazono, 1999). 

ABSTRACT A geochemical analysis of major, trace and rare earth elements was carried out in beach sands collected from the Northeastern coast of Mexico in order to observe the spatial trends along three different beaches. Results show that major elements patterns along the beaches are controlled by heavy minerals and plutonic and sedimentary input towards the coast. In addition, trace elements tendencies indicate that the beach sands are influenced by the presence of magnetite. Finally, the differences in Eu anomalies indicate a mix of felsic to mafic and intermediate rocks and feldspar weathering. 

Rare earth elements patterns show differences in Eu anomalies for the samples studied from Boca del Tordo (Fig. 5) that can be attributed to the mix of felsic and mafic sources. This variation can also be explained due to the impoverishment of feldspars due to weathering (Kasper-Zubillaga etal. 2008b). Also Boca del... 

Rare earth elements trends show a negative and positive Eu anomalies in some samples studied from the Northeastern beaches suggesting a mix of felsic and mafic source rocks and feldspar weathering. 

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... 

Chondrite-normalized REE profiles (Fig. 3) display a distinct enrichment in LREE with prominent negative Eu anomalies, which are broadly consistent with known profiles of monazite in metamorphosed terrains (Spear Pyle 2002). The LREE contents of monazite have fairly restricted compositions dominated by Ce averaging 29.8% Ce203 and behaving sym-... 

Contents of REE in massive sulfides from the BMC are strongly controlled by the abundance of and REE concentrations in phosphate minerals, specifically apatite, xenotime and monazite. Strong positive Eu anomalies in apatite, account for the anomalous Eu signatures of exhalative sulfides whereas REE in monazite masses are largely reflective of detrital sources and may mask hydrothermal signatures. Limited release of mobile trace elements (LREE and Eu) during green-schist facies metamorphism has partly modified REE profiles for VMS deposits of the BMC. 

Rare earth elements (REEs) displayed an average value of 140 23 ppm for XREEs within the Mn-BIFs (Roberts Prince 1990). REE data displayed a negative Eu anomaly within the Mn-BIF and the barren host rocks DDH 87-2 suggestive of no volcanic input associated with the Mn-BIFs (Fig. 3). Positive Eu anomalies commonly occur with Fe-Mn-bearing sediments associated with igneous systems (Mishra et al. 2007). If low ratios of Cerium and Lanthanum (i.e., Ce/La ratios of < 0.12) occur in... 

The felsic rocks have negative Sr and Eu anomalies suggesting plagioclase fractionation. Zr/AbOs appears to be the best criteria for the discrimination of volcanic rocks and related volcaniclastic sedimentary rocks, because the rocks have been hydrothemally altered AI2O3 is the most conserved. The mafic rocks are dominantly of transitional alkaline to calc-alkaline affinity with high Cr and Ni... 

The primitive mantle-normalized trace-element spider diagram of felsic rocks shows negative Sr and Eu anomalies that are indicative of either plagioclase restite or plagioclase fractionation resulting from a combination of the partial melting and fractional crystallization processes (Fig. 5), and later changed by hydrothermal alteration. 

REE patterns of Th-rich uraninite and uranothorianite, are characterized by the high REE contents, a weak global fractionation, and a marked negative Eu anomaly (Fig.2), that are typical for magmatic uraninite, in particular those of the Rbssing alaskite (Bonhoure 2007). 

Rare earth element patterns for basalt and chondrite, and the chondrite-normalized basalt REE pattern. Normalization removes the zigzag pattern due to differences in odd and even atomic number abundances. The europium (Eu) anomaly in the normalized pattern is due to incorporation of extra plagiodase. 

The geochemical composition of the volcanics at most localities in the internal zones of Abruzzi and Lazio is characterised by strongly fractionated REE patterns, with significant negative Eu anomalies. Incompatible element patterns are fractionated and contain negative spikes of Ba and... 

Major element compositions for the Colle Fabbri rocks are extremely variable for such a small outcrop (e.g. Si02 = 43-64 wt % CaO = 4 to 37 wt %). Rare-earth elements (REE) are moderately enriched and fractionated, and contain an important negative Eu anomaly. 87Sr/86Sr ratios range from 0.7077 to 0.7119 and 143Nd/144Nd ratios vary from 0.71115 to 0.71192 (Melluso et al. 2003). 

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