Geochemistry of Santo Antônio da Barra Kamafugites, Goiás, Brazil |
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Authors: | Patricia Barbosa de Albuquerque Sgarbi Jos Carlos Gaspar |
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Institution: | a Departamento de Geologia, Instituto de Geociências, Universidade Federal de Minas Gerais, 31270-901 Belo-Horizonte, MG, Brazil;b IG, Universidade de Brasília, Campus Universitário Darcy Ribeiro, Asa Norte, Brasília, Cep 70.910-900, Distrito Federal, Brazil |
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Abstract: | This work focuses on the kamafugites from Santo Antônio da Barra, Minas–Goiás Alkaline Province. These rocks contain olivine, clinopyroxene, titanomagnetite, perovskite, leucite (pseudomorphs), kalsilite, nepheline, and phlogopite.The rocks investigated are ultrabasic, with high contents of CaO, FeO, and TiO2, high to moderate contents of Al2O3, alkalis, and P2O5, and low contents of MgO. The alkaline characteristic of the rocks is reflected in TiO2, K2O, and Na2O contents and in the frequent presence of normative nepheline and leucite. K2O contents are not primary since most of the leucite was replaced by analcime.The negative K anomaly verified in the extended incompatible element distribution diagram for kamafugites seems to be mainly related to alteration. Kamafugites are characterized by a marked enrichment in incompatible and large ion lithophile elements together with other typical compatible elements.The Santo Antônio da Barra kamafugites are less enriched in titanium, niobium, zirconium, and REE than the Mata da Corda and most of the Toro-Ankole ones. San Venanzo–Cupaello rocks have much lower titanium contents. |
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Keywords: | Kamafugite Mafic alkaline volcanism Cretaceous Santo Antô nio da Barra Brazil |
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