Structural and Tectonic Evolution of K-Rich Silica-Deficient Volcanic Provinces of Different Continents - Origin of Potassium-rich Silica-deficient Igneous Rocks - page 426

Plate Configuration
at ~45 Ma

0 0 10 0 20 0 30 0 40 0

30 0

Tibesti

Future
Red Sea
Rift

Hoggar ~ 25 Ma

ARABIA

20 0

~ 30 Ma

Air

Future
Gulf of Aden
Rift

28 Ma

Darfur <23 Ma

< 30 Ma

Tenere-
Termit - 10 Ma

WARS

Biu

Afar

10 0

MER

Benue
-20 Ma

Ethiopian
Plateau

38 Ma

Adamawa
plateau

Cameroon
Volcanic
Line
<31 Ma

Anza

ER
<33 Ma

0 0

Indian
Ocean

Western
Rift
<12 Ma

is

Eocene
volcanics - 45 Ma
Oligocene-
Recent volcanics

E.African
Plateau

is

Davie
ridge

Is
Comoros
Is

C

Palaeogene
reactivation

-10 0

F

Mesozoic rifts

SL

Jurassic
marine strata

<10 Ma

Madagascar

0 0 10 0 20 0 30 0 40 0

Fig. 14.5 Reconstruction of the African plate at * 45 Ma ago, before the separation of Africa and
Arabia. Shown are Cenozoic plateaux, swells, Eastern Rift (ER); Main Ethiopian Rift, MER) and
magmatism (maximum ages in each province indicated). The distribution of Mesozoic - Palaeocene
rifts, and marine strata along passive margins (after Bosworth et al. 1992; cited by Ebinger and
Sleep 1998)

(a) it has highest mean elevation of all the continents,

(b) it hosts the great East African Rift system,

(c) there is young and active sea- oor spreading in the Red Sea and Gulf of Aden,

and
(d) presence of great volumes of volcanic rocks in the northeast and minor vol-
canism in association with rift valley extended across a large area of the
eastern, central and northern parts of the continents.

These features suggest upwelling of hot mantle under Africa associated with
mantle plumes. A maximum number of 40 hot-spots was proposed by Burke and
Willson (1976) in Africa. Geophysicists working on mantle dynamics have debated
whether so many plumes could rise beneath one continent. Duncan and Richards
(1991, cited by Davies 1998) advocated only one hot-spot within the African