Precambrian Basement of the Congo Basin and Its Flanking Terrains - Geology and Resource Potential of the Congo Basin - page 27

Precambrian crystalline basement. In many places at least
two glacial sequences are recognized and commonly linked
to the Marinoan and Sturtian Glaciations, ca. 635-650 Ma
and 720-750 Ma, respectively (e.g. Poidevin 2007 ; Tait
et al. 2011 ). However, because these sections are not conter-
minous around the CB and because in many places Pan-
African tectonism has tectonically repeated and/or strongly
deformed these sequences (e.g. in the Lufilian Arc of
Zambia and northwest Botswana; the Oubanguides of north-
ern DRC, CAR and Cameroon), and because radiometric
data are scarce and often imprecise, accurate correlations
across the CS remain wanted (e.g. Frimmel et al. 2006 ; Tait
et al. 2011 ; Delpomdor and Pr ´ at, Chap. 3 , this Topic).
An angular unconformity across the Neoproterozoic
carbonates in central Africa is considered to represent the
base of the CB (although some researchers place it beneath
the deformed carbonates; e.g. Daly et al. 1992 ; Kadima et al.
2011 ). It is overlain by ubiquitous Cambrian Redbeds,
which are often tentatively correlated across the entire CB;
however other (similar) formations of red quartzites, conglo-
merates, sandstones and red siltstones are very common
within the stratigraphic record of this large basin (e.g. the
Triassic Haute Lueki Group; Lombard 1961 ) and may often
have been misidentified.

Neoarchean granulites and gabbro-norites (e.g. the
charnockites and enderbites of the Kasai-Lomami Com-
plex), dated between 2.76 and 2.89 Ga, and which, in turn,
are in tectonic contact with Eburnian granites and gneisses to
the south and metasediments to the north (e.g. the Lulua
Group). The age of granulite metamorphism is estimated
at ca. 2.78 Ga and generally referred to as the Musefu
event (Cahen et al. 1984 ). Farther north and east are late
Neoarchean granites and migmatites (the Dibaya Complex),
dated between 2.58 and 2.69 Ga (Cahen et al. 1984 ; Delhal
1991 ). These granites and migmatites of the Kasai Craton
may extend southeast as far as NW Zambia where granites
have also been dated recently at 2561 10 Ma (Key et al.

2001 ). Migmatisation and metamorphism of this age was
referred to as the Moyo event by Cahen et al. ( 1984 ).
More recent U-Pb zircon (TIMS) analyses yielded an
oldest date of 2825

3 Ma on a TTG in the Lunda area of
northeast Angola (and a range between 2.9-2.5 Ma in the
same general region; Doucoure et al. 1999 ; Fig. 2.5 ), and of
2684-2520 Ma (SHRIMP) on biotite gneisses of the Dando-
Kwanza area (Jelsma et al. 2012 ), suggesting an extension of
the central Kasai region into northeast Angola as far south as
the CAMB. Whilst a number of dates on charnockitic gneiss
in the Lunda area have yielded the oldest zircon dates of the
Kasai Craton yet (3.4-3.6 Ga) overprinted by metamorphic
U/Pb zircon of ca. 3.25 Ga (H. Jelsma personal communica-
tion, 2012), the early geological history of the Kasai Craton
is still to be resolved.
Farther south, the Angola basement is swamped by
Eburnian granites (e.g. at Jamba and Cutenda, dated at
1.8 Ga by Cahen et al. 1984 ), and younger rapakivi granites
and syenites

2.4.1 Southern Central Africa

At the southern margin of the CB, the Precambrian basement
corresponds to the Kasai and Cuango Cratons (Kasai and
NE Angola Cratons of Cahen et al. 1984 ), which essentially
comprise Meso- to Neo-Archean grey tonalitic to
granodioritic gneisses (TTG), high-grade metamorphic
granite gneisses (including extensive charnockites and
enderbites) and migmatites (e.g. the Dibaya and Kasai-
Lomami Complexes), as well as large mafic-ultramafic
complexes, all intruded by widespread Neoarchean granites.
Diamondiferous kimberlites of late Precambrian (582 Ma) to
late Phanerozoic (110-140 Ma [Alto Cuilo]; 70 Ma [Mbuji-
Mayi]; 32 Ma [Kundelungu]) intrude these two cratons
(Batumike et al. 2009 ; Jelsma et al. 2009 ; de Wit and Jelsma,
Chap. 17 , this Topic), attesting to the deep cratonic mantle-
lithosphere characteristics of this region (e.g. Fig. 2.4 ).

dated by Rb/Sr between
1302-1411 Ma; de Carvalho et al. 2000 ). Recently, precise
U/Pb zircon analyses re-date these granites between 2065
and 2068 Ma (U/Pb TIMS by S. Bowring, in Doucoure et al.
1999 ). Nevertheless, there is a great apparent range of
granites and syenites from Paleo- to Meso-Proterozoic
based on Rb/Sr dates and low resolution U/Pb zircon dates
(between 1300-1960 Ma, and in one case as young as
1027 Ma; in Cahen et al. 1984 ; Carvalho et al. 2000 ).
More precise petrology and geochronology is clearly
wanted.
The Kasai Craton is overlain by a sequence of Paleopro-
terozoic metasediments (the Luiza Supergroup), intruded by
granitoids (e.g. Kapenda and Lunge) dated between 2.0 and
2.2 Ga, and covered by younger basaltic volcanics (with
pillow lavas) of the Lulua Group dated at 1.9 Ga (Delhal
1991 ; Andre 1994 ). To the NE, it is overlain by Late
Mesoproterozoic carbonate platform metasediments (the
Mbuji-Mayi Supergroup), with basalts in the upper part
dated at 948

( ' red granites '

2.4.1.1 The Kasai Craton
In the central core of the Kasai region of southern DRC,
small regions of Mesoarchean TTG gneisses (c. Luanyi;
Fig. 2.5 ) were dated at 3490

170 Ma (Rb/Sr microcline
date; in Cahen et al. 1984 ), and granodiorites (Kanda-Kanda
gneisses; c. Sandoa) at 3021 49 Ma (Pb/Pb whole-rock

date; Walraven and Rumvegeri 1993 ). These rocks are
flanked to the north and south by an extensive region of

20 Ma (K/Ar whole-rock date; in Cahen
et al. 1984 ; see also Delpomdor et al. Chap. 4 , this Topic).