Lanthanum anomalies

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... 

Studies on the thermal properties of lanthanum, cerium, neodymium, and gadolinium hexaborides in the cryogenic region from 5° to 350°K. 193) have shown the presence of two types of anomalies in the latter three substances. At temperatures near 10 °K. there appears a lambda-type anomaly in each which is rather characteristic of a magnetic transformation. At slightly higher temperatures this is followed by Schottky-... 

Tantalum and niobium in arc magmas are depleted relative to REEs, so that Nb/La and Ta/La are lower than in the primitive mantle and in MORBs. Depletion of primitive arc magmas in tantalum and niobium relative to lanthanum and thorium (Figure 14) is ubiquitous (a few niobium-enriched lavas—e.g., Kepezhinskas et al. (1997)—form a distinct anomaly which will not be discussed in this chapter). For this reason, and because thorium, tantalum, and niobium are relatively immobile in low temperature alteration of basalts, low Nb/Th and Ta/Th have been used as discriminants between arc magmas and both... 

As a result of these factors, the REE pattern of seawater is distinctive. The seawater pattern is heavy REE enriched (e.g., Elderfield and Greaves, 1982). In addition, cerium shows a marked depletion compared with its neighbors, lanthanum and praseodymium. Because average shale contains a negative europium anomaly compared to chondrites, the practice of normalizing seawater to... 

Nuclear magnetic relaxation rates have been used to investigate the coordination number. In an investigation of the line-width broadening of La in various perchlorate solutions, Nakamura and Kawamura (1971) attributed the decreases in the values of (Av is the relaxation rate and is the relative viscosity) to a possible equilibrium between the nonahydrates and octahydrates for lanthanum ion. This conclusion was disputed by Reuben (1975) who proposed that this apparent anomaly reflected an erroneous estimate of the corrections of the linewidths for peaks due to the effect of the finite modulation amplitude and/or of partial saturation. Measurement of the transverse relaxation rates by the pulse method gave results consistent with a constant hydration number for lanthanum ion (Reuben 1975). 

After Moseley published his work relating X-ray spectra to atomic number in 1912, it became known for the first time how many rare earth elements should exist, and it became possible to eliminate many of the elements which had been falsely reported in the literature. The anomaly that 14 elements with properties similar to lanthanum existed, intrigued the theorists, and the existence of these elements proved an important clue in developing our present theories of atomic structure. 

The experimental study of H.G.J. Moseley in the early 1910s on the X-ray spectra of the elements clearly showed for the first time that only 14 4f elements could exist and that one element still remained to be discovered. Furthermore, the anomaly that 14 elements with properties similar to lanthanum proved to be an extremely important clue in aiding Bohr and other theorists in developing our present theory of atomic structure. This work was probably the greatest contribution to the field of the rare earths (lanthanides) since their discovery in 1787. 

Roberts and Lock (1957) measured the heat capacity between 1.5 and 20 K on four lanthanum-cerium alloys (5.0, 27.0, 37.6 and 78.9 at% Ce) and found anomalies which moved to lower temperatures with decreasing cerium content. NikuUn and Patrikeev (1971) studied the nuclear heat capacity of lanthanum-cerium alloys at low temperatures (0.08 to 0.18 K). Culbert and Edelstein (1974) examined several... 

Lundin s data for the calculated heat of mixing in the lanthanum-gadolinium systems is plotted in fig. 8. An anomaly exists in the diagram because lanthanum-rich alloys went into solution slowly—too slowly for accurate results. Between 40 and 60 at% Gd the dissolution slowed down abruptly. Between 7.5 and 30 at% Gd the dissolution was extremely slow but a normal rate of dissolution was observed when less than 5 at% Gd was present. This slowdown of dissolution is not related to the Sm-type phase since it occurs at the other end of the diagram. Lundin deduced that tighter bonding in the lattice occurred over this composition range. 

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