Magnetic susceptibility of Variscan granite-types of the Spanish Central System and the redox state of magma
Villaseca González, Carlos (Universidad Complutense de Madrid. Departamento de Petrología y Geoquímica)
Ruíz Martínez, Vicente Carlos (Universidad Complutense de Madrid. Departamento de Física de la Tierra y Astrofísica)
Pérez-Soba Aguilar, Cecilia (Universidad Complutense de Madrid. Departamento de Petrología y Geoquímica)

Data:	2017
Resum:	Magnetic susceptibility (MS) has been measured in Variscan granites from central Spain. They yield values in the order of 15 to 180µSI units for S- and I-type granites, indicating that both types belong to the ilmenite series. Only samples from magnetite-bearing leucogranites from the I-type La Pedriza massif show high MS values, in the order of 500-1400µSI, reflecting the presence of this ferromagnetic mineral. Mineral chemistry of magmatic Fe-rich minerals (mainly biotite) suggests similar oxidation values for both granite types. MS values change in highly fractionated granites accordingly either with the presence of rare new Fe-oxide phases (some I-type leucogranites) or with the marked modal amount decrease of Fe-rich minerals (I- and S-type leucogranites). The redox state in highly fractionated granite melts is mostly controlled by magmatic processes that modify redox conditions inherited from the source region. Thus, the occurrence of magnetite or ilmenite in granites is primarily controlled by the oxidation state of the source material but also by the differentiation degree of the granite melt. The presence of magnetite in some Variscan I-type leucogranites might be a consequence of crystal fractionation processes in a more limited mafic mineral assemblage than in S-type granite melts.
Drets:	Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, la comunicació pública de l'obra i la creació d'obres derivades, fins i tot amb finalitats comercials, sempre i quan aquestes es distribueixin sota la mateixa llicència que regula l'obra original i es reconegui l'autoria de l'obra original.
Llengua:	Anglès
Document:	Article ; recerca ; Versió publicada
Matèria:	Magnetic susceptibility ; Granite type ; Biotite chemistry ; Oxygen fugacity
Publicat a:	Geologica acta, Vol. 15 Núm. 4 (December 2017) , p. 379-394, ISSN 1696-5728

Adreça alternativa: https://raco.cat/index.php/GeologicaActa/article/view/330805
Adreça alternativa: https://revistes.ub.edu/index.php/GEOACTA/article/view/GeologicaActa2017.15.4.8
DOI: 10.1344/GeologicaActa2017.15.4.8

17 p, 2.4 MB

El registre apareix a les col·leccions:
Articles > Articles publicats > Geologica acta
Articles > Articles de recerca