Zircons - Rare Earth Elements in Ultramafic and Mafic Rocks and their Minerals - page 143

Flatraket province (1)

Flatraket province (2) Flatraket province (3)

Verpeneset province

Figure 4.2 Chondrite-normalized REE patterns for zircons from eclogites from some metamorphic
provinces in Norway. 1-3 - Flatraket province; 4 - Verpeneset province (data Table 4.2).

moderate intensity and intense negative Eu anomalies (Figure 4.3, 1.3). They are also
characterized by very low values for (La/Yb) n 0,0005-0,007. Based on the assump-

tions that the zircons of this type were crystallized on conditions of equilibrium with
the minette parent melt, and that afterwards the trace elements in them have not
undergone a substantial redistribution, the calculations on the model REE composi-
tion of the minette parent melt were made (Figure 4.4). Results of the calculations
showed that this minette parent melt was significantly enriched with LREE, especially
with Ce, and at the same time had some Eu deficiency. The estimated model REE com-
position of minette parent melt gives grounds to consider them as geochemical ana-
logues of lamproites, although in the latter there is usually a less severe Eu deficiency.
The REE composition of the zircon crystals from the considered minettes, which were
assigned to the 2nd, 3rd and 4th types, was studied on the example of single grains. It was
ascertained that zircons of the 2nd type, being close to zircons of the 1st type by total
REE content, differ from them by higher values of (Ce/Ce*) n parameter (Figure 4.3, 4).
Meanwhile, the zircons of 3rd and 4th types show an anomalous enrichment with LREE,
while their patterns have no positive Ce anomalies (Figure 4.3, 5, 6). Apart from this, the
pattern of zircon, which is referred to the 4th type, has no negative Eu anomaly.
The identified geochemical features of zircons from minettes of Kirovograd block
give grounds to consider these zircons to by heterogeneous. Their crystals that are
referred to the 1st type are characterized by typical for this mineral significant enrich-
ment with HREE, depletion by LREE, as well as excess content of Ce with Eu deficit.
Additionally, the unusual for zircons REE distribution observed in the grains, that are
assigned to other three types, melting signs observed in their crystals as well as the
presence of fluid microinclusions, lead to the conclusion that these crystals at a late

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