The metamorphic aureole of the Nisa-Alburquerque batholith (SW Iberia): implications for deep structure and emplacement mode |
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| Authors: | Email author" target="_blank">Luís?González?MenéndezEmail author Antonio?Azor Alvaro?Rubio?Ordó?ez Isabel?Sánchez-Almazo |
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| Institution: | 1.Instituto Geológico y Minero de Espa?a,Parque Científico,León,Spain;2.Departamento de Geodinámica, Facultad de Ciencias,Universidad de Granada,Granada,Spain;3.Departamento de Geología, área de Petrología y Geoquímica,Universidad de Oviedo,Oviedo,Spain;4.CEAMA, Universidad de Granada, Junta de Andalucía,Granada,Spain |
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| Abstract: | The Nisa-Alburquerque granitic batholith (southern Variscan Belt, Iberian Peninsula) has been studied by petrological, structural
and geophysical approaches, obtaining contrasting models for its deep structure and emplacement sequence. In order to test
these models and gain knowledge on the thermal increase induced by the intrusion, we have studied its contact aureole, which
was developed in similar country rock lithologies (mica schists alternating with metasandstones and feldespatic schists) all
along the northern external contact of the batholith. Our results indicate no change in metamorphic grade and some variations
in aureole width, which narrows toward the western sectors of the batholith. Cordierite is the only contact metamorphic mineral
developed together with a high temperature biotite probably related to the granite thermal input. By considering these new
data, together with zircon saturation temperatures within the granite and previous petrological and geophysical studies, we
propose a model in which the feeder zones of the granitic magmas were an eastern main one and a western secondary one. We
have also made comparisons of the metamorphic grade in the country rocks and the xenoliths within the granite. Most of the
xenoliths have the same metamorphic facies as the country rocks (Crd-zone), though some of them contain slightly different
assemblages (And + Crd), which could be explained in different ways: (1) differences in the primary schist compositions, (2)
increased time-span of xenoliths in contact with the melt and (3) xenolith incorporation at slightly higher depths during
final granite ascent. |
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