Geology Reference
In-Depth Information
Fig. 3.1
Simplified geological
map of Sub-Saharan Africa
showing the Neoproterozoic
basins on and around the Congo
Shield (modified after De Waele
et al.
2008
a, b).
LC
Lower Congo
Basin,
Co
Comba Basin,
Sa
Sangha Basin,
Ny
Nyanga-Niari
Basin,
An
Angola Basin,
SO
Semb
´
-Ouesso Basin,
Ba
Ubangui Basin,
LiB
Likki-Bemb
´
Basin,
Bk
Bakouma Basin,
Fou
Fouroumbala Basin,
Li
Lindi
Basin,
It
Itombwe Basin,
Ma
Malagarazi-Bukoban Basin,
Mb
Sankuru-Mbuji-Mayi-Lomami-
Lovoy Basin,
Lu
Luamba Group,
Kat
Katanga Basin,
RB
Ruwenzorian Belt,
KaB
Karagwe-Ankole Belt,
RuB
Ruzisian Belt,
KiB
Kibaran Belt,
UB
Ubendian Belt,
IB
Irumide
Belt
2005
; Kampunzu et al.
2007
), related to the opening of the
Mozambique Ocean (Li et al.
2008
).
Around 600 Ma, West Gondwanaland was coherent with
the assembly of Amazonia, West Africa and Congo-S˜o
Francisco (Maurin
1993
; Trompette
1994
; Brito-Neves
et al.
1999
; Cordani et al.
2003
), initiating the earlier Pan-
African deformations of the Ara¸ua
´
-West Congo Belt (e.g.
Pedrosa-Soares et al.
2001
,
2007
; Alkmim et al.
2006
,
2007
;
Pedrosa-Soares and Alkmin
2011
). The convergence of East
and West Gondwanaland was initiated between approxi-
mately 650 Ma and 515 Ma with the closure of the
Mozambique Ocean (Boger and Miller
2004
; Jacobs and
Thomas
2004
). In Central Africa, the Pan-African tectonic
episode was related to a c. 560-550 Ma collision between
the western margin of the Congo and the S˜o Francisco
shields (Maurin
1993
; Trompette
1994
; Brito-Neves et al.
1999
; Cordani et al.
2003
); between the Kasai-(Angola)-
Kalahari cratons, CS and the Tanzania Craton along a
southeast-northwest trending suture linking up the southern
Mozambique Belt with the Ara¸uai-West Congo Belt
(Porada and Berhorst
2000
; Alkmim et al.
2006
,
2007
;
Pedrosa-Soares et al.
2001
,
2007
; Pedrosa-Soares and
Alkmin
2011
); at c. 620- 610 Ma collision between the
Central African Mobile Zone and the northern margin of
the Congo and S˜o-Francisco shields (Pin and Poidevin
1987
; Toteu et al.
2006
; Oliveira et al.
2006
; Bueno et al.
2009
); and between the northern CS and the Saharan
Metacraton (Abdelsalam et al.
2002
). Recently, Moni´
et al. (
2012
) reported two deformational Pan-African events
in the hinterland domain of the Angola Basin with recrystal-
lisation ages of c. 540 Ma, coeval with the age of 490
3
Ma (Torquato
1974
; Carvalho et al.
2000
).
3.3
Neoproterozoic Stratigraphy
3.3.1 The Western Margin of the CS
The West Congo Belt (WCB) is exposed, on 1,300 km, along
the western margin of the CS. It comprises a thrust-fold-belt
with top-to-(north-)east transport direction from the hinter-
land domain in the west and grades into a foreland domain in
the east with decreasing regional metamorphism from
amphibolite facies (in the west) to unmetamorphosed rocks
(in the east) (Frimmel et al.
2006
).
3.3.1.1 The Sangha-Comba-Lower-Congo basins,
DRC (Fig.
3.2A
)
Lithostratigraphically, the West Congo Supergroup
(Fig.
3.2B
) is divided into, from oldest to youngest, the
rift-related volcanoclastic 999
7 Ma Zadinian and vol-
cano-sedimentary
910 Ma Mayumbian groups deposited
on a
2.1 Ga polymetamorphic Kimezian basement,
and the sedimentary West Congolian Group (Tack et al.
2011
). This latter (originally described by Cahen
1978
)is
subdivided into four subgroups:
(i)
the 1,650 m-thick
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