El Olivino de las rocas volcánicas miocenas de la isla de Fuerteventura (Islas Canarias)
- E. Ancochea 1
- J.L. Brändle 1
- M.J. Huertas 1
- C.R. Cubas 2
- F. Hernán 2
- 1 Dpto. Petrología y Geoquímica. Universidad Complutense -lnst. Geología Económica. C.S.I.C. Fac. C. Geológicas. Madrid
- 2 Dpto. Edafología y Geología. Universidad de La Laguna. Tenerife.
ISSN: 0213-683X
Año de publicación: 1996
Número: 20
Páginas: 558-560
Tipo: Artículo
Otras publicaciones en: Geogaceta
Resumen
Olivine phenocrysts are always present in the Miocene basalts of Fuerleventura, whilst they are scarce in the trachybasaltic types. Notwithslanding, olivine is common as part of the groundmass in these lrachybasalts. This mineral is completely absenl in the Lrachyandesites. When every single rock is considered separately, the Fo-contenl of olivines is always higher in phenocrysts than in small crystals forming the groundmass. So, the olivine phenocrysts in basalts are Fo86-71 and Fo72-56, those found in the groundmass. In trachybasalls these values are respectively lower, Fo79-74 the scarce phenocrysts and Fo59-67 the more abundant crystals contained in the fine grained matrix.No difference related to rock alkalinity 57 is appreciated. Differences in the olivine behaviour among ali three the Volcanic Complexes that conslilule the Old Basaltic Series are not either observed. The Mg-richer phenocrysts in the less differentiated basaltic types show composilional features which evidence ec¡uilibrium with the bearing rock. On the contrary, those in more differentiated basalts should be interpreted as inherited from Mg-richer magmas.