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Plagioclase accumulation and phenocryst reaction in oceanic tholeiite: an indication of spreading rate
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Resumo(s)
A comparison of basalt lithology and chemistry for different mid-ocean ridge spreading axes indicates: (1) basalt generated at slow spreading axes (< 5 cm/yr, e.g. Mid-Atlantic Ridge) reflects widespread flotation of calcic plagioclase and phenocryst-liquid reaction; (2) basalt generated at fast-spreading axes (> 5 cm/yr, e.g., Juan de Fuca Ridge, Galapagos spreading Center, East Pacific Rise) is invariably aphyric or sparsely phyric, phenocrysts if present representing low pressure Iiquidus crystallization products. Interestingly, basalt generated at intermediate spreading rates (e.g., Costa Rica Rift, Gorda Rise, Gulf of California shows incipient development of the «slow-spreading» petrographic tendencies. […].
Descrição
International Symposium on the Activity of Oceanic Volcanoes. Ponta Delgada, 4-9 August 1980.
Palavras-chave
Geology Lithology Petrology
Contexto Educativo
Citação
FLOWER, Martin F. J. (1982). Plagioclase accumulation and phenocryst reaction in oceanic tholeiite: an indication of spreading rate. "Arquipélago. Série Ciências da Natureza", 3: 249-250.