The trachytic rocks of Vilacolum (Girona): an amendment of the large-block rock’s catalogue of the Museo de GeologIa de Barcelona.
Evidence of outcrops of rocks with trachytic texture at Vilacolum (Girona, NE Spain) are known after Font i Sagué (1907), which classified these rocks as amphibolic andesites. Some years later, San Miguel de la Cámara (1921) reclassified these rocks as trachytes studying from a petrographic point of view a block donated by Font i Sagué. A whole rock geochemical analysis by Burn & Parga Pondal (1935) allowed San Miguel de la Cámara (1936) to confirm his initial amendment. These classification of the Vilacolum rocks as trachytes has been accepted until today (Araña et al., 1983; Lopez Ruiz y Rodriguez Badiola 1985).
This note shows that both Font i Sagué (1907) and San Miguel de Ia Cámara (1921) achieved good descriptions of the Vilacolum rocks, because in the Baseia-Els Olivets-Vilacolum sector several petrographic types ranging from basaltic trachyandesite to trachyte are found, in correspondance to a differentiation trend by fractional crystallization of an alkalic (potassic) basaltic magma. Hence, the Vilacolum trachytes are not a petrological oddity in the context of the Tertiary and Quaternary Catalonian volcanic province, and can be considered as an analogue to the well known tertiary and quaternary equivalents of the French Central Massif.
trachyte, trachyandesite, basaltic trachyandesite, kaersutite, pigeonite, whole rock geochemistry, large-block rock's catalogue, Museo de GeologIa deBarcelona, Vilacolum, Girona, NE Spain
Publication date: 09/12/1995
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