Serra Do Bueno
Serra do Bueno consists of a series of small necks and dykes intruding low grade schists. The rocks are 'alkali olivine basalts', containing perovskite and zeolite.
Serra do Bueno consists of a series of small necks and dykes intruding low grade schists. The rocks are 'alkali olivine basalts', containing perovskite and zeolite.
At least 12 of a much larger number of radioactive anomalies in the Bambui area prove to be pipes up to about 100 km in diameter, which are usually filled with breccia.
A circular complex 4.5 km in diameter, Araxa cuts and domes quartzites and schists of the Proteroxoic Araxa Group.
Tapira is an almost circular intrusion about 6 km in diameter emplaced in Precambrian quartzites of the Canastra Group, which strike parallel to and dip away from the contact. The complex is deeply weathered for between 30 and 200 m.
The Sacramento complex consists of a sequence of alkali basaltic flows, tuffs, breccias, dykes and plugs of Cretaceous age.
The small intrusion of Jaboticabal is emplaced in Cretaceous basalts. To the west and northwest near Aparecida de Monte Alto, Taiuva and Piranji alkaline lavas up to 15 m thick intercalated in sandstones of the Bauru Group have been encountered in drill holes.
This intrusion forms prominent steep-sided hills on either side of the Paraguay River (see 130-00-002 Cerro Boggiani). It is surrounded by Recent sediments, but has not been mapped in detail.
An oval-shaped intrusion 4x2.5 km in diameter, Ubari forms a hill cutting Precambrian biotite gneisses. The predominant rock type is a syenite of perthite, aegirine-augite and biotite. There is a little quartz together with apatite, sphene and magnetite.
Morro de Sao Joao is an approximately circular stock 3.5 km in diameter, forming a conical hill reaching 800 m. It intrudes Precambrian granitic and granodioritic gneisses which fringe the hill and then pass beneath Quaternary alluvial deposits.
This is an area of alkaline rocks which includes much of the island of Cabo Frio (6.3 km2) together with the smaller intrusions of Morro do Forno and Atalaia on the adjacent mainland; there is an abundant dyke suite.