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 236

patterns of gabbro-norite and olivine gabbro from this massif shows weak positive
Eu anomalies, while the pattern of olivine gabbro from the massif that has a steep
negative slope doesn't show such anomaly (Figure 10.3, 10-12). We can assume
that the anomalous enrichment with LREE of the rocks from Maysky massif is
due to the presence of non-structural impurity of these elements in them, which
was introduced by fluids from the melts that formed the granitoids pluton located
nearby.
The rocks of Bulkinsky massif are also enriched with LREE. Their distribution
patterns of gabbro-anorthosite and leucocratic troctolite are complicated by positive
Eu anomalies of moderate intensity. Olivine leucocratic gabbro that is significantly
enriched with all REE, has a pattern complicated by especially intense positive Eu
anomaly (Figure 10.3, 13-15).
The determination of Pd, Pt, Ru and Ir in rocks of the massifs located in
the territory of Tuva performed by ICP-MS method showed that the total PGE
content in them ranges from 6.0 to 38 ppb. Contents of certain elements vary
in the following ranges (ppb): Pt (2.65-26.7); Pd (0.82-24.0); Ru (0.25-6.56);
Ir (0.02-0.90). In most samples the content of Pt is higher than the content of Pd,
with the exception of wehrlites of Mazhalyksky massif and gabbro - anorthosite
from Bulkinsky massif. In the rocks of Kalbagdagsky and Mazhalyksky massifs the
Pd content is higher than the content of Ru, but in the rocks of Karaossky, Maysky
and Bulkinsky massifs, with the exception of Bl-17 sample, the content of Ru is
higher that of Pd content. In addition, the rocks of Karaossky massif are charac-
terized by relatively high Ir content. The mentioned features of PGE geochemistry

Mazhalyksky massif Karaossky massif

Kalbagdagsky massif

Maysky massif

Bulkinsky massif

Figure 10.4 Chondrite-normalized PGE patterns for gabbro, gabbro-norite, olivine gabbro, trocto-
lite, wehrlite, websterite and gabbro-anorthosite from Kalbagdagsky, Mazhalyksky, Kara-
ossky, Maysky and Bulkinsky mafic-ultramafic massifs (Central and East Tuva, Russia) (data
Table 10.4). Used PGE composition of chondrite C1 (ppb) [Anders & Grevesse, 1989]):
Pd - 560; Pt - 990; Rh - 134; Ir - 481.