Geochemical relationship between REE and PGE in mafic and ultramafic rocks and their petrogenetic significance - Rare Earth Elements in Ultramafic and Mafic Rocks and their Minerals - page 223

Geochemical relationship
between REE and PGE in mafic
and ultramafic rocks and their
petrogenetic significance
It is known that REE began to be used as geochemical indicators for the diagno-
sis and classification of magmatic, metamorphic and metasomatic rocks and their
minerals, as well as for reconstructions of the processes of their formation as devel-
oped the analytical methods for determining its quite low concentrations in the
analyzed samples. At present, the analysis of REE in geological objects became a
rather routine procedure even while studying the ultramafic and mafic rocks and
minerals depleted by them. Due to this reason, the rare contemporary publications
on the problems of Geochemistry, Mineralogy, Petrology of magmatic rocks and
geodynamics do not use the results of REE analysis by one of the existing analyti-
cal methods. The same trend is approximately observed with respect to platinum
group elements (PGE), the determination of relatively low concentrations of which
became possible with the introduction of several new analytical techniques includ-
ing ICP-MS method.
Zharikov & Yaroshevsky [2003] while examining the challenges and prospects
for further development of the geochemical sciences, among other things, pointed at
two important problems of petrology that can be solved by using geochemical meth-
ods: 1) a comprehensive study of the behavior of different groups of compatible and
incompatible impurities in magmatic processes, and 2) identification of correlations
between groups of impurities that are different in their geochemical properties in
order to develop consistent models of dispersion and concentration during the genera-
tion, differentiation, contamination and crystallization of magmatic melts of different
composition.
Barnes et al . [1985] while discussing some aspects of geochemistry of PGE in a
variety of products of magmatic processes, came to the conclusion that the determina-
tion processes, during which the fractionation of PGE in nature occurred, were such
as partial melting of mantle sources, crystallization differentiation of melts, as well as
some epigenetic processes.
In recent years, some studies were executed aiming to identify relationships
between REE and PGE in rocks of ultramafic and mafic composition [Lazarenkov
et al ., 1989; Naldrett et al ., 1994; Roman'ko et al ., 1994; Shengrong et al ., 1994;
Lesnov et al ., 2000, 2001, 2004b, 2005c; Pearson & Woodland, 2000; Lesnov &
Oydup, 2002; Lesnov, 2003a, b; Schmidt et al ., 2003; Lesnov & Balykin, 2005;
Zhou et al ., 2005; Karipi et al ., 2006; Day et al ., 2008; Lesnov, 2006, 2009; and
others]. Despite the limited number of analyses performed, the results of these studies
have shown that comprehensive data on the contents of REE and PGE provide an