Geochemistry of Volcanic Rocks, Albernoa Area, Iberian Pyrite Belt, Portugal
| Autor: | Carlos J. P. Rosa, Vítor M. J. Oliveira, Carlos Inverno, Diogo R. N. Rosa |
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| Rok vydání: | 2004 |
| Předmět: | |
| Zdroj: | International Geology Review. 46:366-383 |
| ISSN: | 1938-2839 0020-6814 |
| Popis: | Volcanic rocks from the Albernoa area essentially consist of calcalkaline quartz-feldspar-phyric coherent and hyaloclastic rhyodacites, and alkaline and tholeiitic basaltic rocks. Binary plots show that high-field-strength elements behaved as immobile elements, and allow for the identification of two felsic rock suites. Silica and alkali mobility, however, is reflected by compositional scatter on major-element diagrams: felsic rocks display rhyolitic to apparent andesitic compositions, and the mafic rocks display basaltic to apparent dacitic compositions. Silica and alkali mobility was focused along fracture networks and within the matrices of hyaloclastic breccias. Problematic classification of geotectonic setting for the felsic rocks is a reflection of anomalous high-field-strength element systematics; this probably results from a low temperature of crustal fusion, causing decreased solubility of the refractory phases in which these elements reside. The mafic rocks, however, evidently were generated in ... |
| Databáze: | OpenAIRE |
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