Alkaline Rocks and Carbonatites of the World

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Mapari

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Occurrence number: 
025-00-010
Country: 
Brazil
Region: 
Amapa Federal Territory
Location: 
Longitude: -52.92, Latitude: 1.13

Mapari consists of three small intrusions having diameters of 200-500 m. Rock types include nepheline syenite and alkali syenite. The nepheline syenites comprise perthite, albite/oligoclase, nepheline, amphiboles, which include riebeckite and possible barkevikite, pyroxene and cancrinite. A syenite containing sodalite rather than nepheline is described as litchfieldite and includes alkali feldspar, albite/oligoclase, amphibole, biotite and calcite. A feldspathoid-free syenite occurs and comprises perthite, albite, an amphibole thought to be barkevikite, calcite and opaques.

Age: 
Rb-Sr on whole rocks gave 1335±39, 1680±63 and 1537±38 Ma (Issler et al. 1975).
References: 
ISSLER, R.S., LIMA, M.I.C. de, MONTALVAO, M.B.G. de and SILVA, G.G. da, 1975. Intrusivas feldspatoididas no Craton Guianes. Congresso Ibero-Americano de Geologia Economica, II: 363-82. ISSLER, R.S., LIMA, M.I.C. de, MONTALVAO, M.B.G. de and SILVA, G.G. da, 1975. Intrusivas feldspatoididas no Craton Guianes. Congresso Ibero-Americano de Geologia Economica, II: 363-82
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