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https://repositorio.ufba.br/handle/ri/9941
metadata.dc.type: | Artigo de Periódico |
Title: | Uranium and thorium in potash-rich rhyolites from western Bahia (Brazil) |
Other Titles: | Chemical Geology |
Authors: | Sighinolfi, G.Paolo Sakai, Tereza |
metadata.dc.creator: | Sighinolfi, G.Paolo Sakai, Tereza |
Abstract: | The U and Th distribution in K-rich acid metavolcanics affected by postmagmatic processes has been studied. Th (20 ppm) and U (2.41 ppm) average abundances are well within the normal ranges for granitic rocks, but the Th/U values are appreciably higher than most of the values reported. Since the rhyolitic magma is supposed to have been formed by partial melting of pre-existing rocks, the high Th/U ratios may be due: (1) to an extreme magmatic fractionation towards a K-rich trend in the magma chamber or during magma displacement; and (2) to high Th/U ratios in the original material, probably ancient crystalline basemental rocks depleted in U with respect to Th during previous cycles. The possible influence of postmagmatic processes on U and Th distribution is discussed, and evidence of U mobilization and redistribution within the formation is set forth. |
Publisher: | Chemical Geology |
URI: | http://www.repositorio.ufba.br/ri/handle/ri/9941 |
Issue Date: | 1974 |
Appears in Collections: | Artigo Publicado em Periódico (IGEO) |
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