Rare earth elements in ultramafic and mafic rocks and their minerals. Main types of rocks. Rock-forming minerals / Редкоземельные элементы в ультраосновных и основных породах и их минералах. Главные породы. Породообразующие минералы

This monograph is the generalization of up-to-date data and theoretical ideas on the problems of the geochemistry of rare earth elements (REE) in ultramafic and mafic rocks as well as in their minerals. As is the convention in the Russian, URSS literature, by the term “rare earth elements’’ or REE, we mean, after Henderson (Rare Earth Element Geochemistry, 1984), the chemical elements of Group IIIA of the Periodic Table of Elements from lanthanum to lutetium with atomic numbers from 57 to 71: La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. For brevity, this group of elements is sometimes referred to as “lanthanides’’ (Solodov et al., 1998). In 1968, in accordance with the decision of the International Union of Pure and Applied Chemistry (IUPAC), Sc and Y were also included in the REE, but this usage has not become generally accepted. Despite the similarity of their chemical properties, among them the fact that the charge of their ions is predominantly 3+, the REE differ in the sizes of their ion radii, which decrease from La3+ (1.032 Å) to Lu3+ (0.861 Å) (Shannon, 1976]. This served as the basis for dividing the REE into groups, first into ceric and yttric elements, and later, into light (La . . . Eu) and heavy (Gd . . . Lu) ones (this division is followed in the present work). Somewhat less frequently the REE are divided into three groups: light (La . . . Nd), middle (Pm . . . Ho), and heavy (Er . . . Lu) elements (Rare Earth Element Geochemistry, 1984). All the REE, except Eu2+, just as a number of other trace elements, are included among the high-field strength elements (HFSE) (Rollinson, 1993; Sklyarov, 2001). <...>