Significance of Europium anomalies in silicate melts and crystal-melt equilibria: a re-evaluation

Origin of convex tetrads in rare earth element patterns of hydrothermally altered siliceous igneous rocks from the Zinnwald Sn–W deposit, Germany

“…In the past decades, the geochemical behavior of the rare earth elements (REEs) has been studied extensively because this group of elements provides a range of geochemical indicators that can be used to constrain the evolution of magmatic and hydrothermal systems (e.g., Mö ller and Muecke, 1984;Masuda and Akagi, 1989;Raimbault et al, 1993;Dostal and Chatterjee, 1995;Bau, 1996;Pan and Breaks, 1997;Mö ller, 1998;Irber, 1999;Monecke et al, 2000). It has been shown that variations in the geochemical behavior of the REEs primarily result from differences in their ionic radii (ionic radii of the REEs decrease steadily with atomic number) as well as variations in valence states (Ce 3+ and Ce 4+ , Eu 2+ and Eu 3+ ).…”

Discovery of lanthanide tetrad effect in an oceanic plagiogranite from an Ocean Core Complex at the Central Indian Ridge 25.DEG.S

“…It is known that a conspicuous negative Eu-anomaly is a typical REE feature of tetrad granites (e.g., Irber, 1999). Crystal fractionation of plagioclase, which has a very high partition coefficient for Eu, is commonly regarded to cause a negative Eu-anomaly in igneous rocks (e.g., Möller and Muecke, 1984). However, Irber (1999) has shown that strong Eu depletions (Eu/Eu* < 0.06) with tetrad REE patterns cannot be accounted for only by plagioclase fractionation.…”

REE(Y), Nb, and Ta Enrichment in Pegmatites and Carbonatite-Alkalic Rock Complexes

“…With the exception ofthe wall zone and firstintermediate zone, which show positive Eu anomalies, even the negative Eu anomaly stays unchanged, although the REE in the fluid must have increased as a consequence of solidification. The conspicuous change ofEu anomalies between the first and the second intermediate zone has been interpreted by the authors to indicate either a change in melt structure (Möller and Muecke 1984) or in fo2 (Drake and Wei111975).…”

“…REE(Y) in biotite and apatite; Eu in feldspars], the negative Eu anomalies develop in the evolved melts (e.g.leucogranites in Fig. 6) In highly polymerized melts silicate-Eu 2 + complexes are more stable than the Eu 3 + equivalents and the other trivalent REE(Y) complexes (Möller and Muecke 1984). The Eu 2 + -silicate complex, with its assumed double four-ring structure, is preferentially incorporated in feldspars, because it can be considered as a subunit of the feldspar structure.…”