Cerium peridotites

The middle REE (MREE) show AI2O3 covariation patterns intermediate between those of heavy and TREE. Samarium shows both a rough positive correlation reminiscent of the one observed for ytterbium, and variations irrespective of AI2O3 comparable to those observed for cerium (i.e., higher samarium in orogenic peridotites, especially the metasomatized samples, than in ophiolitic and abyssal peridotites). 

In addition, a detailed study of a metasomatized wall rock adjacent to an amphi-bole-pyroxenite dike has revealed that the contamination in " Nd/ " " Nd and Sr/ Sr is spatially limited to a distance of <25 cm from the dike (Bodinier et al., 2003). This distance is interpreted as the chromatographic front of neodymium and strontium since the infiltration of small volume melts probably occurred on a greater distance in the host peridotite, as attested by the enrichment of the highly incompatible elements observed at 25-80 cm from the dike (e.g., lanthanum and cerium, see Section... 

Most apatites are chlorine-rich (2-4.3%) with low F/Cl (0.1 -0.3). High fluorine ( 5%) and low chlorine (—0.25%) have been reported for apatite in spinel Iherzolites from Pacific OIB (Hauri et al., 1993). Extremely high strontium contents, commonly >2X10 ppm and up to 7 wt.% (Ionov et al., 1997 Table 9) are common in mantle apatites meaning that this phase is a major repository for strontium when present in peridotites at abundances of 0.1% or above. Rb/Sr is very low. Apatites have high levels of REE and are LREE-enriched (Table 9). Lanthanum and cerium concentrations can reach >1 wt.% and neodymium concentrations can be above 1,000 ppm. Sm/Nd is below PUM. HFSE are low and so the presence of this phase does not affect bulk rock HFSE chemistry. 

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