A series of widely spaced, scattered dykes, up to a metre thick, are aligned northeast-southwest and cut variable Precambrian gneisses. Rock types represented include nepheline-phyric tinguaite, porphyritic shonkinite and monchiquite.
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This island of less than 2 km2 consists of nepheline syenite, pulaskite and syenite, with or without quartz and with gradational boundaries between them. Modal nepheline increases from east to west and its concentration indicates a submerged nepheline syenite centre 1 km west of the island.
This is an island of 7.5 km2, 90% of which is occupied by syenite and quartz syenite, the northwestern part being of Precambrian gneisses and hypersthene charnockites.
Four poorly exposed, stock-like bodies occupy about half the island and cut Precambrian gneisses and granites and some large basaltic dykes.
The island of Monte de Trigo is 1.2x1.3 km, 90% of which is foyaite and the rest melatheralite with minor olivine gabbro, jacupirangite, teschenite and essexite. The foyaite consists of alkali feldspar, nepheline (2-11%), barkevikite, aegirine-augite and a little biotite, sodalite or analcime.
Itanhaem is a series of biotite tinguaite dykes cutting shield rocks. In the same area dykes of olivine sovite are reported.
This is a small dyke of porphyritic shonkinite with phenocrysts of biotite, aegirine-augite, apatite and orthoclase, in a groundmass of the same minerals plus nepheline. Weathered syenitic rocks also outcrop.
An approximately circular complex of nearly 13 km2, Ipanema intrudes Precambrian schists and Permian Tubarao sandstones which are fenitized (Davino, 1975).
Dykes exposed in a railway cutting south of Tatui are shonkinites similar to those of Piedade (No. 97).
Juquia is an asymmetric, zoned intrusion of 14 km2 intruded into Precambrian gneisses of the Acungui Group, which are fenitized in places.