Alkaline Rocks and Carbonatites of the World

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Bernal De Horcasitas


Occurrence number: 
Longitude: -98.03, Latitude: 22.07

A volcanic plug rising almost vertically for 600 m, Bernal de Horcasitas is surrounded by an apron of basalt lavas, and lies in the plain about 15 km south of Sierra de Tamaulipas. The rock consists of clinopyroxene, biotite, nepheline, alkali feldspar, plagioclase, which is probably albite, and accessory apatite. A chemical analysis indicates 17% normative nepheline and 23% alkali feldspar. Xenoliths of biotite granite and syenite are present.

HEIM, A. 1934. El Bernal de Horcasitas, a volcanic plug in the Tampico Plain, Mexico. Zeitschrift fur Vulkanologie, 15: 254-60. ROBIN, C. 1976. El vulcanismo de las plancies de la Huasteca (Este de Mexico). Datos geoquimicos y petrograficos. Boletin Universidad Nacional Autonoma de Mexico. Instituto de Geologia, 96: 55-92
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