ASPECTOS PETROGRÁFICOS E VULCANOLÓGICOS DA PROVÍNCIA ALCALINA-CARBONATÍTICA DE SANTO ANTÔNIO DA BARRA, SUDOESTE DE GOIÁS

JOSE C. GASPAR, JOSE CARUSO MORESCO DANNI

Resumo


The volcanic province of Santo Antônio da Barra located in the southwestern portion of Goiás is of Cretaceous age (± 85,8 m.y.), and comprises a heterogeneous sequence of analcitic rocks (pyroclastic and flows), locally capped by flows, tuffs, and agglomerates of silicocarbonatitic composition. Rests of volcanic structures and a great number of pypes and vents formed by fourchites and melamonchiquites are found tectonically controlled by NW-trending faults. They are regarded as differentiated hypoabyssal products of continental volcanism of nefelinitic type. It is reported in Brazil for the first time the occurrence of carbonatitic volcanoclastics related to the terminal stage of analcimitic volcanism.


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