U–Pb dating of granodiorite and granite units of the Los Pedroches batholith. Implications for geodynamic models of the southern Central Iberian Zone (Iberian Massif) |
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| Authors: | M Carracedo J L Paquette A Alonso Olazabal J F Santos Zalduegui S García de Madinabeitia M Tiepolo J I Gil Ibarguchi |
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| Institution: | 1.Departmento de Mineralogía-Petrología,Universidad del País Vasco/EHU,Leioa,Spain;2.UMR6524 Magmas et Volcans, Université Blaise Pascal,Clermont-Ferrand,France;3.Servicio General de Geocronología y Geoquímica Isotópica/SGIker,Universidad del País Vasco/EHU,Leioa,Spain;4.C.N.R. Istituto di Geoscienze e Georisorse, Unità di Pavia,Pavia,Italy |
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| Abstract: | The first U–Pb geochronological results on the magmatic alignment of the Los Pedroches batholith are presented. The batholith
is composed of a main granodioritic unit, several granite plutons and an important acid to basic dyke complex, all of them
intrusive after the main Variscan regional deformation phase, D1, along the boundary between the Ossa-Morena and Central Iberian
zones (SW Iberian Massif). Zircons from samples on both extremes of the granodiorite massif record nearly simultaneous magmatic
crystallization at ca. 308 Ma, while the emplacement of granite plutons was diachronic between 314 and 304 Ma. The U–Pb results
combined with new field and textural observations allow to better constrain the age of Variscan deformations D2 and D3 across
the region, while the age of D1 remains imprecise. Transcurrent D2 shearing-tightening of D1 folds occurred around 314 Ma
(lower Westphalian) in relation to the emplacement of the first granitic magmas. D3 faults and shear bands bearing a strong
extensional component developed at ca. 308 Ma (upper Westphalian), associated to the intrusion of the main granodiorite pluton
(granodiorite) of the batholith. Together with available geochemical and geophysical information, these results point to the
Variscan reactivation of lithospheric fractures at the origin and subsequent emplacement of hybrid magmas within this sector
of the Massif. |
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