Rare earth elements normalization

The X-ray determination of REE in geological samples is normally complicated by the relatively low concentrations of the REE, their complex X-ray spectra, the high concentration of matrix elements and the lack of reference standards with certified values for REE. A rapid and sensitive ion exchange and X-ray fluorescence procedure for the determination of trace quantities of rare earths is described. The REE in two U.S.G.S. standards, two inhouse synthetic mixtures and three new Japanese standards have been determined and corrections for inter-rare earth element interferences are made. 

The rare earth elements (REE) form a group of elements that have coherent geochemical behaviour due to their trivalent charge and similar ionic radii. They can, however, be fractionated from one another as a result of geochemical processes operating under specific physico-chemical conditions. In order to outline general trends within and differences between the individual REE, concentrations are usually normalized to a reference system (e.g. to shale). Deviations of individual elements from the generally smooth trend are referred to as anomalies. 

The Piton de la Fournaise volcano (Indian Ocean) erupts basalts with chemical compositions that change with time. The rare-earth elements have been measured on eight dated historic lavas (Table 3.9 and Figure 3.7, Albarede and Tamagnan, 1988), and chondrite-normalized (Ce/Yb)N ratios over the time interval 1948-1985 are given in Table 3.9. Calculate an annual interpolation of these results. 

Table 10.1 lists r values calculated for normalized distributions of alkalis and alkaline earths between silicates and hydrothermal solutions and for normalized distributions of rare earth elements (REE) between pyroxenes and silicate melts. 

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. 

It has been found by Utsumi(1985a,b) that in J-type carbon stars of C4-5 and WZ Cas(C9,2J Li), abundances of s-process elements with respect to Fe are nearly normal, while in normal carbon stars of C5-8, heavy metals are overabundant by factors of 10-100, and rare-earth elements are overabundant by a factor of about 10. 

Figure 10.6. Observed secular trends in the chemical composition of sedimentary rocks. Eu/Eu = ratio of observed normalized Eu concentration to that predicted (Eu ) from extrapolation between REE Gd and Sm. REE = rare earth element LREE = light REE HREE = heavy REE. Data from several authors as presented in Veizer (1988).

Cs are more depleted in western coals. Silicon is also depleted in coal, probably because of the presence of clay minerals. Most lithophile elements (i.e., those normally associated with the earth s crust) have EF values near one, but it is interesting that the rare earth elements show slightly, but consistently higher enrichments in eastern coal. The apparent depletion of Ta is probably not real, but an artifact resulting from Wedepohl s use of too large a crustal abundance for it (14). 

This refers to decomposition of the normal anhydrous sulfate to its first decomposition product, oxysulfate or oxide as the case may be for each element. The dashed line preceding Gd represents the other rare earth elements. With increasing atomic number the stability first decreases in the order Pr - Nd - Sm - Eu and then increases in the order Tb - Dy - Ho - Er - Tm - Yb. 

Although the +3 oxidation state is by far the most common one for the rare earth elements, for some of them others (+2, +4) are of importance. Cerium, and to a much lesser extent Pr and Tb, can form Ln4+ ions (formally speaking) but these are strongly oxidizing. Sm, Eu, and to a lesser extent Yb form Ln2+ ions. These deviations from normal behavior (i.e., formation of only Ln3+) are sometimes attributed to the special stability of empty, half-filled or filled shells Ce4+ (4/°), Eu2+ (4 f), Yb2+ (4/14), but Pr4+ (4 f) and Sm2+ (4/6) do not fully satisfy this criterion. This idea is better considered as a mnenonic than as an explanation. 

Figure 2. Rare earth elements concentrations (normalized to chondrites) for the original rocks (serpentinite and hornblende diorite) and their alteration products...

Figure 3, Chondrite-normalized rare earth element patterns of soapstone samples from quarries in the Mbe-marle-Nelson County regions of Virginia and in Crete. For the Albemarh-Nelson quarries f — the two lines give the range of 12 samples analyzed, and for the Crete samples (O — O) the two lines define the range of 19 samples. Two artifacts made of soapstone from the Albemarle-Nelson quarries are shown. One — M) is a pot from a habitation site in Cherokee County, NC and the other (A-- A) a pot from a habitation site near the quarry in Buckingham County, VA.

Figure 17 (a) Chondrite-normalized rare earth element patterns and (b) primitive-mantle normalized trace element... 

All values are on a coal basis. Data are exclusively from the US Geological Survey (USGS) except for estimated values in parenthesis which are based on USGS and literature data. Values in brackets are calculated from cerium and lanthanum data and assuming a chondrite normalized rare-earth-element distribution pattern. (ND — no data SD — standard deviation Max. — maximnm Num. = nnmber of samples). 

Fig. 9.24. Cl chondrite normalized rare earth element concentrations for geological glasses. The Ll-MS data are compared with the results of other analytical techniques. ( ) LI-MS (O) LA-ICP-MS (A) HPLC (V) SY-XRF ( ) INAA (X) TI-MS. (Reproduced with permission of Springer-Verlag.)...

In geochemistry, rare earth element (REE) patterns constitute a useful tool for interpreting geological processes. LI-MS produces reasonably good REE patterns, as shown in Fig. 9.24, which is a plot of Cl normalized REE concentrations alongside the results obtained with INAA, HPLC, LA-ICP-MS, synchrotron X-ray fluorescence (SY-XRF) spectroscopy and secondary ion mass spectrometry (Tl-MS). INAA and TI-MS surpass... 

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