Alkaline Rocks and Carbonatites of the World

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Ilha Dos Buzios


Occurrence number: 
Sao Paulo
Longitude: -45.13, Latitude: -23.8

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. The syenite is a coarse, grey rock of mesoperthite, K-feldspar, aegirine-augite, hornblende, biotite and opaque minerals and grades in places into quartz syenites. Near contacts with Precambrian gneisses and charnockites, the quartz syenites pass into a fine to medium grained, green variety of the same mineralogy but with the addition of remnant orthopyroxene; these rocks are rich in xenoliths.

F. R. Alves, personal communication, 1985;. BJORNBERG, A.J.S. and ELLERT, R. 1955. Observacoes geologicos e petrograficas sobre a Ilha dos Buzios. Anais da Academia de Ciencias, 27: 169-82
Fig. 1_213 Ilha dos Buzios (F. R. Alves, personal communication, 1985).
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith