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D470 and D600 (the Dekese Formation)
data-point error ellipses are 2
σ
30
106 dates (80-110% conc.)
a
b
3000
0.6
25
2600
20
2200
0.4
15
1800
1400
10
0.2
1000
5
0.0
0
0
4
8
12
16
20
0
500
1000
1500
2
3000
3500
00
000
207
Pb/
235
U
Age (Ma)
WP19 (the Lower Kwango Group)
data-point error ellipses are 2
σ
30
59 dates (80-110% conc.)
c
d
3000
0.6
25
2600
20
2200
0.4
15
1800
1400
10
0.2
1000
5
0.0
0
0
4
8
12
16
20
0
500
00
1000
000
1500
2000
2000
2500
500
3000
3500
207
Pb/
235
U
Age (Ma)
Fig. 8.16
U-Pb Concordia- and frequency age-diagrams of detrital
zircons from (
a
and
b
) sample WP19 of the Lower Kwango Group in
the southwest CB, and (
c
and
d
) samples D470 and D600 of the Dekese
Formation in the middle part of the Dekese cores, plotted using Isoplot
3.0 (Ludwig
2003
)
8.6.2.3 Early Neoproterozoic to late
Mesoproterozoic (900-1100 Ma)
In total, 56 zircons date between 900 Ma and 1100 Ma,
forming a major peak centered at 1000 Ma (Fig.
8.16
).
This 1 Ga age-population is identical to other analyzed
samples from the underlying Carboniferous-Permian and
corresponds to the general
zircons in the J-K sequences of the CB suggests that the
type-Kibaran Belt was not a major source, possibly because
it was covered by sediments or it was below sea-level during
the Mesozoic.
8.6.2.4 Cambrian to late Neoproterozoic
(500-850 Ma)
97 zircons date between 500 and 850 Ma (Fig.
8.16
),
corresponding to the widespread Pan African tectono-
metamorphic events in Africa (Cahen et al.
1984
). Such
dates are abundant within the West Congo, Oubanguides,
Mozambique and Lufilian Belts, and their overlying foreland
period in Africa (e.g.
Cahen et al.
1984
), although its type-area along the eastern
margin of the CB, in eastern DRC, Rwanda and Burundi has
been shown recently to be older and restricted in age to ca.
1375 Ma (Tack et al.
2010
). This may requires a new
definition of the Kibaran, but this is beyond the purpose of
this study. Here, the general absence of ca. 1.4 Ga detrital
'
Kibaran
'
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