Precambrian Basement of the Congo Basin and Its Flanking Terrains - Geology and Resource Potential of the Congo Basin - page 24

These dates also confirm Kibaran (s.s.) mafic and granite
magmatism and crustal melting along the southern margin of
the SWCS, similar to the Karagwe-Ankole Belt east of the
CB; both predated by Paleo-Mesoproterozoic sedimentation
across a large region of the CAS, including the Kibaran
Supergroup sequences flanking the western margin of the
Tanzania Craton (e.g. Pedreira et al., 2008 ).
Extensive Archean areas north of the CAMB have also
been affected locally by Eburnian tectono-metamorphic
remobilisation. In parts of the Kasai and Cuango Cratons,
the 2.0-2.2 Ga Mubindji Event deformed Paleoproterozoic
metasediments (Luiza Group) and possibly related low-
grade metabasaltic with pillow lavas (Lulua Group), which
unconformably overlie Archean charnockites and enderbites
(Cahen et al. 1984 ; Carvalho et al. 2000 ). Neither accurate
field relationships nor precise geochronology are available to
establish a more detailed geologic history.
If the Kasai, Cuango and Ntem Cratons are in fact
connected beneath the CB (as the SWCC), then the flanking
Eburnian high-grade mobile belt (CAMB) to the south
may have stretched all the way from Zambia in the southeast
(terminating along a NE-trending Eburnian-Kibaran
transcurrent suture) to Gabon, where, as the WCAMB, it
forms basement to the younger, overlying West Congo Belt
(Figs. 2.2 , 2.3 and 2.4 ). The westernmost tectonic margin of
the (CAMB-WCAMB) Mobile Belt is exposed in Brazil
between the Trans-Amazonian suture (containing the fold
and thrust belt, and gold mineralisation in the Jacobina
metasediments) that separates the eastern margin of the
Sao Fransisco Craton from the Archean-Eburnian Jequie
granulites along the east coast of Brazil (e.g. Feybesse
et al. 1998 ; Lerouge et al. 2006 ).
Finally the CS was again strongly tectonized during the
Pan-African (Brasiliano) orogenesis (ca. 650-540 Ma; e.g.
de Wit et al. 2008 and references therein) during accretion of
continental blocks along peripheral suture zones, now
manifested by a number of well-studied fold-and-thrust
belts, including: the West Congo, the Oubanguides (Central
African Fold Belt), the Mozambique, and the Irumides-
Lufilian-Damara-Kaoko Belts (Figs. 2.2 , 2.3 and 2.4 ).
These belts all verge tectonically into the CB, and provided
sediment detritus to late Neoproterozoic-early Paleozoic
foreland basin sequences that cover the basement rocks
and/or the Cryogenian Carbonate sequences exposed along
the outer margins of the CB (e.g. Delpondor and Pr´at, Chap.
3 this Topic), and which likely also cover the basement of
all of the three Congolese Cratons as shallow marine
carbonates, with possibly evaporites (e.g. Kadima et al.,
Chap. 6 , this Topic; Selley et al. 2005 ; Jackson et al. 2014).
Evaporite minerals have been recorded in these sequences
where they outcrop near the southern and western margins of
the CB (e.g. Mbuji-Mayi and Gabon; see Delpomdor et al.,
and Kolo et al., Chaps. 4 and 5 , this Topic, respectively),

However, major salt sequences have not been observed
anywhere in the deep drill holes through the central CB or
along the peripheral Neoproterozoic basins (e.g. Tait et al.,
2011 ; and, respectively, Kadima et al., and Linol et al.,
Chaps. 6 and 11 , this Topic).
Regionally, unconformably overlie the folded

Neoproterozoic (carbonate) sequences of the Pan-African
Belts and in cores through the CB (Kanda et al. 2011 ).
These Redbeds can no longer be considered as only Pre-
cambrian, as frequently argued, because ca. 540 Ma detrital
zircons have been found in the Redbeds of the Inkisi Group
(Jelsma et al. 2011 ). At least the upper parts of the CB
Redbeds are thus younger than earliest Cambrian; however,
the general stratigraphy of these and younger Redbeds
remains poorly constrained as there is no reliable chronostrati-
graphy to correlate them accurately (e.g. Tait et al. 2011 ).
It has been suggested that the CCC and SWCC
amalgamated along an NW-SE trending Pan African defor-
mation zone (Daly et al. 1992 ; de Wit et al. 2008 ; Figs. 2.2
and 2.5 ), but the age of this deformation, indeed even the
existence of such a Neoproterozoic deformation zone is still
in dispute (Linol et al., Chap. 12 , this Topic) and will require
new high resolution reflection seismology to clarify this
(e.g. Kadima et al. 2011 ; Kadima et al., Chap. 6 , this
Topic). Similarly, the CCC and NECC may have amalgama-
ted along a NW-SE trending deformation zone during the
Mesoproterozoic (Kibaran) (as suggested by S. Master in
2004, see Raveloson et al., Chap. 1 , this Topic), or during
Neoproterozoic (Pan African) as suggested by de Wit et al.
( 2008 ; see Fig. 2.2 ). Again there is no hard data, geologically
or geophysically, to refute or substantiate these working
models.
Below we briefly summarize the most reliable geology
and geochronology of some of the cratons and shield
regions, referred to above, surrounding the CB.

' Redbeds '

2.4 Local Geology and Geochronology

of Cratonic Domains and Their Cover
Sequences Surrounding the CB

The Precambrian basement of the Congo Shield and relevant
parts of the CAS is described below in four sub-regions:
(1) southern, (2) western, (3) northern, and (4) eastern cen-
tral Africa (Fig. 2.3a, b ). A detailed map with selected (most
robust) radiometric dates summarized from the literature and
our own unpublished data, is presented (Fig. 2.5 ; Table 2.1 ).
In almost all of the basement areas directly flanking
the CB, thick (~5-10 km) sequences of Cryogenian
(850-635 Ma) siliciclastics and carbonates, with excellently
preserved, albeit sedimentologically complex, glacial
deposits (diamictites and tillites; also sometime named
' mixites ' ) and cap carbonates rest directly on the