Apatites - Rare Earth Elements in Ultramafic and Mafic Rocks and their Minerals - page 176

Benfontein sill
Wesselton province

Figure 5.2 Chondrite-normalized REE patterns for apatites from kimberlites from Benfontein sill and
from Wesselton province (data [Jones & Wyllie, 1984]). Normalization was performed
according to [Nakamura, 1974]).

in the cumulative layers enriched with oxides. Moreover, the apatites from kimberlites
of Wesselton province are presented with numerous but smaller segregations and
together with associating perovskite grains are evenly distributed in a homogeneous
rock matrix enriched with carbonates.
The REE composition of apatites that has been studied in great detail are from
Boggy Plain granitoid massif (Australia) and are presented with adamellites (outer and
inner), granodiorites (outer and inner), as well as diorites and aplites [Hoskin et al .,
2000]. All of these apatites have a high total REE content and their samples from dif-
ferent varieties of granitoids show some differences in REE composition (Table 5.2,
Figure 5.3). In particular, the average total REE contents in the mineral increase in the
following row of rocks: diorites → granodiorites (outer) → granodiorites (inner) →

adamellites (outer) aplites (Table 5.3, Figure 5.4). All apa-

tites from rocks of this massif have the level of La accumulation several times higher
than the level of Lu accumulation. In the mineral from granodiorites forming the
inner areas of the massif, the values for (La/Yb) n are a much higher (46-65) compared
with the mineral from aplites (7-8). All apatites from rocks of Boggy Plain massif
have in their patterns some negative Eu anomalies of approximately equal intensity:
(Eu/Eu*) n

→ adamellites (inner) →

0.17 - 0.39. Apatites from granodiorites of the outer zone are different
from their samples from other varieties of rocks by the highest average values of
(La/Yb) n and the most intense negative Eu anomalies. In addition, the apatites from
aplites, which are characterized by the highest average total REE content, are also
described by the lowest average values of (La/Yb) n .
The distribution of La, Ce, Nd, Sm and Gd has been studied for the apatites from
some samples of metasomatic rocks represented in xenoliths from kimberlites of Matsoku
manifestation (Lesotho province, Southern Africa) [Exley & Smith, 1982]. Along with
accessory apatite these metasomatic rocks contain phlogopite (amber mica), amphi-

=