Geology Reference
In-Depth Information
Table 7.1
Summary of U-Pb detrital zircon dates from samples D1400 and D1595 (the Lukuga Group)
Age-population
U-Pb Dates (
206
Pb/
207
Pb)
Notes
1. Mesoarchean
One (oldest) zircon dates at 2925
8Ma
2. Early
Paleoproterozoic to
Neoarchean
10 zircons date between 2.4 Ga and 2.7 Ga, with 9 concentrated
between 2566
Indicate some contributions from Neoarchean aged-
terrains. These dates are similar to dated basement rocks
in southern DRC and northern Angola (Delhal
1991
;
Jelsma et al.
2011
), western Tanzania and Uganda (Link
et al.
2010
), and Gabon (Caen-Vachette et al.
1988
)
17 Ma and 2690
16 Ma
3. Paleoproterozoic
(
Second most
common age-
population
)
48 zircons date between 1.8 Ga and 2.1 Ga, with 21 restricted
between 1852
Overlap the conventional Eburnian period (e.g. Cahen
et al.
1984
). Such dates are common within the
Ruwenzori and Ubendian Belts in Uganda and western
Tanzania (Lenoir et al.
1995
; Nagudi et al.
2003
), and
within the (Kimezian) basement of the West Congo Belt
in western DRC and its large counterpart in eastern
Brazil (Tack et al.
2001
; Pedrosa-Soares et al.
2008
)
17 Ma and 1898
17 Ma, and 17 between
2006
17 Ma and 2048
10 Ma
4. Mesoproterozoic
8 zircons date between 1.2 Ga and 1.6 Ga, with 5 bracketed
between 1371
18 Ma and 1421
16 Ma
Coincide with the main peak of magmatism of the
Kibaran Belt in eastern DRC, Rwanda and Burundi
(Kokonyangi et al.
2004
; Tack et al.
2010
)
5. Early
Neoproterozoic to
late Mesoproterozoic
(
Most common age-
population
)
49 zircons date between 902
27 Ma and 1181
29 Ma
Indicate large contributions from late Mesoproterozoic
aged-terrains. These dates are common with the
Oubanguides, in particular the central Sahara Belt in
CAR and Chad (de Wit et al.
2014
, in press), and the
Mozambique Belt (Jamal et al.
1999
; Bingen et al.
2009
)
6. Late
Neoproterozoic
30 zircons date between 544
21 and 865
25 Ma
Indicate large contributions from Pan African aged-
terrains, such as the West Congo, Oubanguides,
Mozambique and Lufilian Belts
Table 7.2
Summary of U-Pb detrital zircon dates from samples S1605 and S2035 (the Haute Lueki Group)
Age-population
U-Pb dates (
206
Pb/
207
Pb)
Notes
1. Early
Paleoproterozoic
One (oldest) zircon dates at 2470
10 Ma
2. Paleoproterozoic
6 zircons date between 1952
11 Ma and
Indicate relatively small contributions from Eburnian aged-terrains.
Such dates are common in Uganda and western Tanzania (Lenoir 1995;
Link et al.
2010
), and in Angola and western DRC (de Carvalho et al.
2000
; Tack et al.
2001
)
2103
5Ma
3. Mesoproterozoic
15 zircons date between 1.2 Ga and 1.5 Ga,
with only one concordant date at
1399
Kibaran Belt (ca. 1.4 Ga) was not a major source, possibly largely
covered by sediments
65 Ma
4. Early Neoproterozoic
to late Mesoproterozoic
(
Second most common
age-population
)
36 zircons date between 940
9 Ma and
1143
15 Ma
Indicate large contributions from late Mesoproterozoic aged-terrains,
dinstinctively younger than the 1.4 Ga Kibaran type-area. Potential
source areas have been reported in CAR and Chad (de Wit et al.
2014
in
press), and in Mozambique (Jamal et al.
1999
; Bingen et al.
2009
)
5. Late Neoproterozoic
(
Most common age-
population
)
40 zircons date between 579
14 Ma and
817
15 Ma
Correspond to tectonic episodes of the Pan African orogens, such as
within the Oubanguides that include multiple structures active between
850 Ma and 550 Ma (Poidevin
1985
; Rolin
1995
; Toteu et al.
2006
)
are some differences in their proportions that apparently
reflect changes in provenance. Figure
7.15
shows a simpli-
fied map of basement ages around the CB to evaluate possi-
ble source regions for these detrital zircons.
(S1605 and S2035). This suggests greater (more proximal)
derivations from early Precambrian sources to the glacial
sediments in the Dekese section, or that these sources
became progressively covered during deposition of the
Haute Lueki Group. These 2.4-2.9 Ga sources most likely
correspond to the Kasai and Tanzanian Cratons located
immediately to the south (~200 km) and to the east
(~800 km) of the Dekese section, respectively. This prove-
nance is also supported by the E-W orientations of Carboni-
ferous glacial valleys (Fig.
7.15
).
7.4.3.1 Early Paleoproterozoic to Archean
(2.4-2.7 Ga and 2.9 Ga)
Early Paleoproterozoic to Archean dates are more common
in the samples (D1400 and D1595) from the Lukuga Group
(8 grains) in the Dekese section compared to those from the
Haute Lueki Group (only 1 grain) in the Samba section
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