Publication: Caracterización de gneises glandulares del alto valle del Lozoya
(Sistema Central Español) en base al quimismo de las biotitas
y estado estructural del feldespato potásico
Loading...
Official URL
Full text at PDC
Publication Date
1982
Advisors (or tutors)
Editors
Journal Title
Journal ISSN
Volume Title
Publisher
Instituto Geológico y Minero de España (Madrid)
Citations
Exportar
Abstract
En el presente trabajo se estudian las litologías gneísicas glandulares que afloran en la ladera este del Macizo de Peñalara (Sistema Central Español), en base a la interpretación del quimismo de las biotitas de glándulas y mesostasia y del estado estructural del feldespato potásico que forma la mayoría de estas glándulas. Se deduce a partir del estudio de las biotitas, que las glándulas se comportan como sistema cerrado para el Ti y abierto para el Al durante el metamorfismo regional. El contenido en Ti de las biotitas en el interior de las glándulas es, por tanto, heredado de la historia premetamórfica de éstas, y puede relacionarse con las temperaturas de cristalización ígnea. La relación Fe/Mg de la biotita depende de la composición de la roca total. La variación estructural del feldespato potásico viene impuesta por la litología premetamórfica y por varia ciones en el campo de esfuerzos. A partir de estos datos se confirma un origen detrítico para los gneises glandulares de la Serie Calderuelas, mientras que los gneises del Reventón y Morcuera son ortoderivados.
Augengneisses cropping out at the eastern slopes of the Peñalara Massif (Spanish Central System), are dis· tinguished on the basis of chemical composition of biotites from groundmass and megacrysts and structural state of megacrysts forming K-feldspar. It seems likely that megacrysts behave as a closed system for Ti in biotites and open for Al during regional metamorphism. Ti content of biotites trapped in megacrysts is therefore inherited form the previous premeta morphic story of the mineral and seems likely related to the temperatures of igneous crystallization. Fe/Mg ra tios are controlled by bulk rock composition. Structural state of K-feldspar making up most of the megacrysts is determined by premetamorphic lithology as well as stresses field. A detritial origin for the Calderuelas augengneiss is concluded, whilst Morcuera and Reventon augnegneisses are of plutonic provenance.
Augengneisses cropping out at the eastern slopes of the Peñalara Massif (Spanish Central System), are dis· tinguished on the basis of chemical composition of biotites from groundmass and megacrysts and structural state of megacrysts forming K-feldspar. It seems likely that megacrysts behave as a closed system for Ti in biotites and open for Al during regional metamorphism. Ti content of biotites trapped in megacrysts is therefore inherited form the previous premeta morphic story of the mineral and seems likely related to the temperatures of igneous crystallization. Fe/Mg ra tios are controlled by bulk rock composition. Structural state of K-feldspar making up most of the megacrysts is determined by premetamorphic lithology as well as stresses field. A detritial origin for the Calderuelas augengneiss is concluded, whilst Morcuera and Reventon augnegneisses are of plutonic provenance.