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 270

High-Mg basalts
Picrites
Tholeiitic basalts

La, ppm La, ppm

Figure 10.29 Relationship between La compositions and Pd/Ir (1) and Pt/Ir (2) parameters values for
picrites, high-Mg and tholeiitic basalts from region of Bushveld pluton (South Africa)
(data Table 10.13).

10.11 GALMOENAN MASSIF
(KORYAK HIGHLAND, RUSSIA)

Galmoenan massif is located in the Koryak highland (Kamchatka). Detailed petrologi-
cal and geochemical studies on the massif were performed in the course of exploration
and exploitation of closely located and genetically associated large placer deposit of
platinum group metals [Koryak-Kamchatka region, …, 2002]. Body of the massif
elongated in the submeridional direction, has a length of about 16 km and a width
of 2-4 km, and is exposed on an area of approximately 48 sq · km. It is composed of
dunites that make up its interior part, less commonly of olivine-, plagioclase-bearing
and magnetite clinopyroxenites that compose a 200-700 m wide zone surrounding
the dunite body, while among the pyroxenites some xenogeny isolations of wehrlites
and serpentinites occur. Along the contacts of pyroxenite zone with terrigenic-volcanic
formations that are framing the massif there is a gabbro intrusion fragmentarily
uncovered by erosion.
Based on the results of comprehensive research, including numerical modeling,
Batanova et al . [2011] concluded that the diversity of ultramafic and mafic rocks that
form the massif arose from an intrachamber differentiation of single upper mantle mafic
melt. However, our observations and, in particular, the presence of xenogeny isolations
of wehrlites and serpentinites among pyroxenites do not allow to exclude the possibil-
ity of existence of an alternative model of the genesis of this massif, which is based on
an idea of polygenic formation of complex mafic-ultramafic massifs [Lesnov, 1981,
1982, 1986]. According to the model, the dunite body of the considered massif is an
earlier protrusive block of upper mantle restites. In its peripheral part the dunites were
transformed into clinopyroxenites as a result of exposure to later mantle mafic melts
and their fluids. Mafic melts intruded along tectonic contacts of dunite protrusion with
the framing rocks and then formed gabbro intrusion that is unevenly uncovered on the
perimeter of this complex massif. However, the applicability of this alternative model
of formation to this mafic-ultramafic massif requires further studies.
Published data on the contents of REE and PGE in dunites from Galmoenan
massif (Table 10.15), as well as diagrams based on them (Figure 10.34) give ground