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Fig. 2.1
Simplified early Precambrian map of Gondwana (GIS from de
Wit et al.
1988
; modified). Inset (A and B) Four major African Precam-
brian Shields (
pale blue
): 1
¼
West African Shield; 2
¼
Saharan Shield;
3
¼
Central African Shield; 4
¼
Southern African Shield, and other
fragments of Rodinia (~1 Ga): A
(C) crustal domains of central Africa with four cratons (
yellow
): 1
i,ii,iii
¼
Ntem, Cuango, Kasai
¼
SouthWest Congo Craton (SWCC); 2
¼
Cuvette [Central] Congo Craton (CCC); 3
¼
Mboumou-Uganda
¼
NorthEast Congo Craton (NECC), forming the Congo Shield (CS,
green
), and enlarged in Proterozoic to form the Central African Shield
(CAS,
dark blue
).
Red dotted outline
is the SouthWest Congo Shield
(SWCS)
¼
Amazonia; B
¼
Baltica; L
¼
Laurentia; I
North
China (simplified from Li et al.
2008
and Lindeque et al.
2011
). Inset
¼
India; S
¼
Siberia; SC
¼
South China; NC
¼
(e.g. Kasai, Cuango, Ntem, Bouca, [Bomu] Mboumou-
Uganda) and some of which amalgamated before the end-
Archean into three larger cratons:
Paleoproterozic Shield in Eburnian times (circa 2.0 Ga; e.g.
Pedrosa-Soares et al.
2008
, and references therein). Suffice it
to say that it has been argued, for example, on the basis of
paleomagnetism and undeformed Mesoproterozioc sedi-
mentary sequences found on both shields (dated between
1.7-1.8 Ga (Pedreira and de Waele
2008
) that the two conti-
nental terrains may have been connected at that time (e.g.
Trompette
1994
), but also that the age correlations are far
from detailed enough to substantiate this correlation from
one continent to another (e.g. McCourt et al.
2004
; Pedreira
and de Waele
2008
). Whilst we will briefly refer to this
potential connectivity below, it is beyond the scope of this
chapter to explore this in further detail here.
As early as the mid-Paleoproterozoic, the eastern and
northern margins of the CS were convergent margins that
experienced Eburnian subduction-obduction of ca. 2.0-2.3 Ga
oceanic lithosphere, and accretion of Archean continental
fragments, over a period of at least 150 Ma, between ca.
2050-1880 Ma (e.g. Boniface and Schenk
2012
;Boniface
et al.
2012
; Nkoumbou et al.
2013
; Lawley et al.
2013
,
2014
;
and see below). By contrast, the southern margin of the CS is
defined by the Central Shield Zone of Angola (cf. Carvalho
et al.
2000
), a wide transition zone of Eburnian granitoid
magmatism and high grade tectonism that also embodies a
the Southwestern,
Cuvette [or Central], and Northeastern Congo Cratons
(SWCC, CCC, NECC, respectively), but the detailed tec-
tonic history of which still
'
remains largely unknown
(Fig
2.1
, inset C). We use
(CS) for a larger
lithospheric region that comprises those three cratons that
cannot be directly correlated beneath the present CB for lack
of appropriate geophysical data, but which likely amal-
gamated during the Proterozoic and which all lie inboard
of surrounding Pan-African (ca. 0.8-0.5 Ga), Kibaran (ca.
1.0-1.4 Ga) or Eburnian (ca. 1.9-2.3 Ga) orogenic belts and
related inferred suture zones that surround the CB (Fig.
2.1
,
inset B; Fig.
2.2
).
For simplicity, here we specifically separate the Congo
Shield (CS) from potential conterminous shield areas in
Brazil. Even though parts of a larger central African shield
area, which we here term the Central African Shield (CAS),
may have been linked to the greater S˜o Francisco Shield
(mostly referred to in the literature as a Craton) in a Rodinia
framework (Fig.
2.1
, inset A), there is still considerable
uncertainty about the detailed timing and accretion pro-
cesses that may have linked these two shields into a larger
'
Congo Shield
'
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