Different Localities of Potassium-Rich Silica-Undersaturated Igneous Rocks and Their Silica-Rich Variants - Origin of Potassium-rich Silica-deficient Igneous Rocks - page 117

Fig. 4.9 Map of the Birunga
volcanic and Toro Ankole
field (after Holmes 1965)

N

MILES

0 250 500

1 - BIRUNGA FIELD
2 - TORO-ANKOLE FIELD
3 - SOUTH KIVU FIELD

Lake
Rudolf
KENYA

2

Lake
Victoria

CONGO
Lake Kivu

1
3

INDIAN
OCEAN

Lake
Tanganyika

TANZANIA

Fig. 4.10 The sketch map
showing the position of
heights (in ft) of the eight
major volcanic complexes
north of Kivu (after Holmes
1965)

UGANDA

CONGO

MILES

0 10 20

and K 2 O/Na 2 O ratio from Lake Kivu through Nyamuragira, Nyiragango and to two
different centres of the lava plane (Table 4.6 ).
The three most easterly volcanoes, Muhavura, Gahinga and Sabinyo lie along an
east west line suggesting their positions as fault-controlled (Rogers et al. 1998).

Whereas the Muhavura and Gahinga were erupted lavas of the K-basanites series
(e.g. Nyamuragira, Mikeno and Karisimbi) to the west, the lava of the Sabinyo
volcano, is unique in the Birunga volcanic province in that they are silica-saturated
orthopyroxene-bearing K-trachytes and latites. The majority of the lavas from

-