Alkaline Rocks and Carbonatites of the World

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Morro Do Engenho

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Occurrence number: 
025-00-042
Country: 
Brazil
Region: 
Goias
Location: 
Longitude: -51.67, Latitude: -15.53

This is a zoned intrusion of about 5 km diameter forming a hill and emplaced in Devonian Furnas sandstones. There is a central core of dunite surrounded by peridotites and pyroxenites and these in turn by a border group of alkaline gabbros and nepheline syenite. The dunites are partially serpentinized. The pyroxenites, as well as 'augite', contain olivine and a little plagioclase. These rocks pass gradually into biotite-bearing gabbros. The nepheline syenites are coarse rocks with nepheline phenocrysts up to 1. 5 cm, perthite, 'sanidine' phenocrysts and Ti-augite zoned to aegirine. A small area of rock composed essentially of pyroxene and magnetite and described as jacupirangite occurs, while small veins of carbonatite with phlogopite cut the dunite.

Economic: 
Garnierite occurs in laterite, with an estimated reserve of 70 million tons averaging 1.27% Ni (Rodrigues and Lima, 1984).
References: 
PENA, G.S. and FIGUEIREDO, A.J.A. 1975. Projeto Goiama II, relatorio final. Departamento Nacional da Producao Mineral. Companhia de Pesquisa de Recursos Minerais, 1: 121-61. RODRIGUES, C. de S. and LIMA, P.R.A. dos S. 1984. Carbonatitic complexes in Brazil. Companhia Brasileira de Metalurgia e Mineracao: 1-17
Fig. 196 The Ipora Group of occurrences of alkaline intrusions of central Goias.
Location: 
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith