Ilmenites - Rare Earth Elements in Ultramafic and Mafic Rocks and their Minerals - page 119

Table 3.2 Chemical compositions of ilmenites from gabbro-norites and websterites from Tigrovy
massif (Primorie province, Russia) (wt%).

Sch-093g Sch-095c Sch-096c Sch-085c Sch-095d

Component Gabbro-norites Websterites

TiO 2 52,84 47,80 50,53 48,15 47,09

Al 2 O 3 0,04 N.d. 0,01 0,06 0,01

Cr 2 O 3 N.d. N.d. N.d. 0,23 0,13

FeO tot 46,41 47,45 49,24 49,53 49,05

MgO N.d. 0,07 N.d. N.d. N.d.

MnO 1,06 1,36 0,69 1,60 1,56

CaO 0,01 0,37 N.d. N.d. 0,01

Na 2 O N.d. 0,01 N.d. N.d. N.d.

K 2 O N.d. 0,04 N.d. N.d. N.d.

Total 100,36 97,10 100,47 99,57 97,85

Note: Microprobe analyses were done in the Institute of volcanology and seismology, Far East Branch of RAS,
Petropavlovsk Kamchatsky (data V. Rybalko).

phases. It is obvious that in these two silicate phases during the crystallization have
focused the vast majority of available Eu in parent melt. Therefore, the residual por-
tion of the latter, which then became the material of crystallization of ilmenite, should
be exhausted with respect to Eu, so its excess in this ilmenite was not supposed to take
place. Considering the possible causes of the observed positive Eu anomalies in these
ilmenites, one would assume that they are caused by the presence of some amounts of
micro-inclusions of plagioclase in their grains. However, the phase X-ray analysis of
these ilmenites had shown, that the admixture of plagioclase has not been detected.
Thus, the reason for the positive Eu anomalies in the patterns of these ilmenites has
not been ascertained yet. What is more, a very intense negative Eu anomaly was found
on the spectrum of ilmenite from the rhyolite, which is characterized by very high
concentrations of REE (Figure 3.1, 12).
According to the analysis of ilmenites of kimberlites from Indaia manifestation
(Alto Paranaiba province, Brazil) it was ascertained that the overall level of accumula-
tion of REE in them is significantly lower than in C1 chondrite, while the chondrite-
normalized contents of HREE in them is higher than the content of LREE (Figure 3.1,
13, 14).
Judging by the configuration of REE pattern, all the researched ilmenites from
gabbros of Skaergaard massif demonstrate a slight enrichment with LREE and a more
significant enrichment with HREE compared with the MREE, and many of these pat-
terns show very weak positive or negative Eu anomalies (Figure 3.1, 15).
Aschepkov et al . [2007] investigated the REE composition of great collections of
ilmenite megacrystals from 50 pipes from six regions of the kimberlite magmatism in
Yakutia (Russia). In this work it was shown that ilmenites from the researched kim-
berlite pipes both as a whole and from each of the pipe are characterized by very wide
variations of REE composition, as can be seen both in the total content of elements and
the configuration and slope of their distribution (Table 3.1, Figure 3.2). Thus, the total