Alkaline Rocks and Carbonatites of the World

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Cerro San Cristobal


Occurrence number: 
Longitude: -66.97, Latitude: -16.97

This intrusion of about 1.2x0.4 km has a narrow, hornfelsed aureole 15-20 m wide. One rock type consists of 70% nepheline, which is slightly replaced by cancrinite, a little orthoclase and albite, and sparse biotite and sodic amphibole; femics constitute less than 10% of the rock. In boulders derived from the intrusion sodalite has been identified. Numerous boulders of coarse, white calcite rock also occur which contain nests of apatite crystals and an unidentified Zr-Ti silicate. The difficulty of the terrain has, so far, precluded a detailed investigation of the occurrence.

AHLFELD, F. 1966. Geologische Untersuchungen in der Provinz Ayopaya (Bolivien). Neues Jahrbuch fur Mineralogie, 104, 147-71
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