Produção Nacional
The Mesoproterozoic rhyolite occurrences of fuerte Olimpo and fuerte San Carlos, northern Paraguay
2000; Sociedade Brasileira de Geologia; Volume: 30; Issue: 4 Linguagem: Inglês
10.5327/rbg.v30i4.909
ISSN2317-4889
AutoresCelso B. Gomes, P. Comin-Chiaramontí, Victor F. Velázquez,
Tópico(s)Paleontology and Stratigraphy of Fossils
ResumoPetrographic and geochemical data make it clear that rocks at the localities pf Fuerte Olimpo and Fuerte San Carlos, which lie on the margins of the Paraguay and Apa rivers, respectively, in northern Paraguay, are rhyolites. However, in the Paraguayan geological literature, these sites nave been associated to alkaline rocks. Isotopic data for the rhyolites indicate a Precambrian age of 1341 Ma (1341 ± 53 Ma and 1343 ± 4 Ma, respectively) and give almost identical values for the initial ratio 87 Sr/ 86 Sr of 0.71335 ± 0.00126 and 0.71215 ± 0.00008, respectively. On the basis of these results as well as the distribution of minor and trace elements normalized to primitive mantle, they are probably correlated to the Mesoproterozoic acidic rocks of the Rio Branco Suite occurring in the Jauru Terrain at the SW portion of the Amazon Craton.
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