Different Localities of Potassium-Rich Silica-Undersaturated Igneous Rocks and Their Silica-Rich Variants - Origin of Potassium-rich Silica-deficient Igneous Rocks - page 147

Plain M Basin

AMAZONAS
CRATON

Amazonas
Craton

Parana
Basin

Sao Francisco
Craton

Ipora
Province
(80-90)

16 o

Sao Francisco
Craton

Alto
Paranaiba
Province
(85)

22 o

Parana
Basin

Serra Domar
Province
(54-80)

Eastern
Paraguay
Province
128-132

Ponta Grossa
Province
(67-132)

Lages
(75-80)

28 o

Atlantic
Ocean

Anitapolis
(132) N

0 200 400 600 Km

58 o 52 o 46 o

Fig. 4.17 The Alto Paranaiba Igneous Province, Brazil (after Gibson et al. 1994)

complexes. According to them the most voluminous surface expression of K-rich
ma c volcanic rocks in the province are the lavas and tuffs of the Mata da Corda

formation. Gibson et al. noted the occurrences of vents and crater facies rocks of these
lavas at Serra do Bueno and Presidente Olegario. The lavas and tuffs outcrop
throughout the petrographic province from Presidente Olegario in the north to Sao
Gotardo and possibly further south to Oliveira, covering an area of more than
4,500 km 2 . They overlie the lower Cretaceous Areado formation and attain a thick-
ness of more than 100 m in the Sao Gotardo-Quintinos-Carmo do Paranaiba region.
The locality around Presidente Olegario (18

W) was probably the
site of numerous volcanic centres from which thick sequences of lavas and tuffs
were erupted. The intrusion of Mata do Lenco contains xenoliths of glimmerite,
harzburgite and dunite.

° 25 ′ S, 46 ° 26 ′