Alkaline Rocks and Carbonatites of the World

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Circular Structure

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Occurrence number: 
025-00-021
Country: 
Brazil
Region: 
Maranhao
Location: 
Longitude: -46.27, Latitude: -7.67

A major concentration of circular structures occurs in northeastern Brazil in the states of Maranhao and Piaui with one in Goias. Most show evidence of doming and they are thought probably to be underlain by alkaline intrusions. Those listed are taken from Rodrigues and Lima (1984).

References: 
PESSOA, R.R. 1975. Perspectivas de ocorrencias de complexos alcalinos no nordeste Brasileiro e sua importancia economica. Atas do Simposio de Geografia Geologia, Fortaleza, 7: 319-26. RODRIGUES, C. de S. and LIMA, P.R.A. dos S. 1984. Carbonatitic complexes in Brazil. Companhia Brasileira de Metalurgia e Mineracao: 1-17
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