Ilmenites - Rare Earth Elements in Ultramafic and Mafic Rocks and their Minerals - page 102

schists of Polar Urals REE total content reaches 107 ppm, and in sample of ilmenite
from rhyolite - 1700 ppm. In the mineral from the gabbros of Skaergaard massif REE
total content varies in the range of 1.94-9.05 ppm (Table 3.1).
In picroilmenites of Frank Smith, Monastery (South Africa) and Mir (Yakutia,
Russia) kimberlite pipes there were observed increased chondrite-normalized REE
contents of LREE and to a smaller extent Yb and Lu compared with MREE, while
the patterns of REE distribution in these samples have a common negative slope
(Figure 3.1, 1-4). In turn, the patterns of ilmenites from Yubileynaya kimberlite pipe
(Yakutia, Russia) and from the pyroxenites presented in the xenoliths indicate their
enrichment with medium and heavy REE. At the same time the patterns of picro-
ilmenites of kimberlites from Yubileynaya pipe have a shape close to sinusoidal
(Figure 3.1, 5). Unlike previous ones, the ilmenites from pyroxenites presented in the
xenoliths from basalts of Bayuda (Sudan) and Kakanui volcano (New Zealand) vol-
canoes are depleted by LREE relative to HREE, respectively, their patterns have the
same positive slope (Figure 3.1, 6, 7). The patterns of some ilmenites have positive or
negative Eu anomalies of different intensity (Figure 3.1, 10, 12).
We have investigated the collection of samples of accessory ilmenites from
gabbro-norites and websterites composing the Tigrovy massif (Primorie province,
Russia) [Lesnov et al ., 2004a] which, as well as Ariadninsky, Kedimiysky, Uonchoy-
sky massifs and the others, is situated in the southern part of Khabarovsk territory,
in Sikhote Alin ridge [Shcheka et al ., 1973; Shcheka et al ., 2003]. Numerous indig-
enous manifestations of disseminated and massive ilmenite ores and ilmenite plac-
ers are connected to all these massifs spatially and genetically. The ilmenite content
in the massive ore sometimes reaches 50%. In the accessory ilmenites of Tigrovy
massif the TiO 2 content varies in the range of 47.0-53 wt%, FeO tot - 46-49 wt%,
MnO - 0.7-1.6 wt%, and the presence of impurities of MgO and Cr 2 O 3 was identi-
fied only in some of the cases (Table 3.2). Determination of REE in these ilmenites
was carried out by INAA method and in the certain grains was duplicated by ICP-MS
method (Table 3.1). According to the method of INAA, the total REE content in
ilmenites of Tigrovy massif varies in the range of 5.81-6.98 ppm, and the differ-
ences between ilmenites from websterites and gabbro-norites on this basis have not
been identified. All ilmenites in this collection demonstrate a relative enrichment with
LREE: (La/Yb) n 3.0-4.8, respectively, their patterns have a common negative slope

(Figure 3.1, 8, 9). Analyses of those ilmenites from gabbro-norites, which were per-
formed by ICP-MS method, indicated the presence of a substantial surplus of Eu in
them (Figure 3.1, 10). According to the data obtained by the mentioned method for
the ilmenites from gabbro-norites the values (Sm/Eu) n

=

0.19-0.28, which is slightly
less than in its samples from websterites (0.38-0.48). Determination of REE in the
three samples of ilmenites made by INAA method and duplicated by ICP-MS showed
results comparable both on the basis of the content of certain elements and their
total content (Table 3.1). Positive Eu anomalies on the REE pattern of ilmenites from
websterite (sp. Sch-095D*, Figure 3.1, 8) and gabbro-norite (analyses Sch-093 g*, 1a,
b, c; Figure 3.1, 10) which were identified according to ICP-MS method, also show
a slight excess of this element in the samples stated. According to observations made
under an optical microscope, the ilmenite grains from these and other samples from
the Tigrovy massif are mostly xenomorphic regarding coexisting crystals of pyroxene
and plagioclase, which indicates their belated crystallization relative to these silicate

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