Hercynian Acid Magmatism and Related Mineralizations in Northern Portugal

Almeida, Angela; Martins, Helena; Noronha, Fernando

doi:10.1016/s1342-937x(05)70733-4

Cited by 18 publications

(16 citation statements)

References 7 publications

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“…In the studied sector (Fig. 1B), this pluton crosscuts the peraluminous two-mica syn-D 3 granites of Cabeceiras de Basto Complex (Almeida et al, 2002) and a metasedimentary sequence Silurian in age (Ribeiro et al, 2001). At the northern part it was intruded by the post-D 3 Gerês Massif (Mendes and Dias, 2004).…”

Section: Geological Settingmentioning

confidence: 79%

“…The late deformation phase, D 3 , Namurian-Westphalian in age, is correlated to the post-thickening and extension which marked the end of the collision process (Dias and Ribeiro, 1995;Lagarde et al, 1992). The events related to this tectonic phase were marked by vertical folds with subhorizontal axes and strike-slip sinistral and dextral, subvertical shear zones which controlled the large volume of orogenic granitic rocks emplaced in the Central Iberian Zone, (Aguado et al, 2005;Almeida et al, 2002;Dias et al, 1998Dias et al, , 2002Ferreira et al, 1987;Martins et al, 2009Martins et al, , 2011Noronha et al, 1979). Based on field and geochronological data, these Variscan granites were divided into two main groups (Dias et al, 1998;Ferreira et al, 1987;Martins et al, 2009Martins et al, , 2011: synorogenic (syn-late and late to post-D 3 ; 320-300 Ma) and late to post-orogenic (post-D 3 ; 299-290 Ma).…”

Section: Geological Settingmentioning

confidence: 99%

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Late-Variscan emplacement and genesis of the Vieira do Minho composite pluton, Central Iberian Zone: Constraints from U–Pb zircon geochronology, AMS data and Sr–Nd–O isotope geochemistry

Martins

Ovaia

Noronha

2013

Lithos

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In the Central Iberian Zone synorogenic (syn-and late-D 3 , the last deformation phase) composite batholiths of biotite-rich granitods with peraluminous character are well represented. We report here U-Pb zircon and monazite ages, geochemical, Sr-Nd-O isotopic data and Anisotropy of Magnetic Susceptibility (AMS) studies for the late-D 3 Vieira do Minho pluton, in northern Portugal. AMS reveals the paramagnetic behaviour of these granites and the magnetic fabric enhances the major role of NW-SE regional anisotropies on controlling the ascent and emplacement of the magmas. Magnetic anisotropy and medium temperature microstructures also point out the evolution of regional tectonics during crystallization of the magma. U-Pb zircon and monazite analyses yield consistent ages of 310 ± 2 Ma and 312 ± 2 Ma, interpreted as emplacement age. The Vieira do Minho pluton consists of two peraluminous monzogranites, the VMG and the MRG. Both have similar ε Nd values (VMG= −5.2 to −5.7; MRG =−4.98 to −5.96) but the VMG is slightly enriched in 87 Sr/ 86 i = 0.7087-0.7098 as well as in δ 18 O in the range of 10.6‰ to 11.0‰ than the MRG with 87 Sr/ 86 i =0.7064-0.7075 and δ 18 O=9.9‰-10.5‰. These granites are associated with coeval scarce grabroic intrusions and/or mafic microgranular enclaves which are not considered as mafic precursors of the associated granitic magmatism. Instead, a lower metaigneous crustal source, at different levels, is proposed based on the available data set.

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Section: Geological Settingmentioning

confidence: 79%

Section: Geological Settingmentioning

confidence: 99%

Late-Variscan emplacement and genesis of the Vieira do Minho composite pluton, Central Iberian Zone: Constraints from U–Pb zircon geochronology, AMS data and Sr–Nd–O isotope geochemistry

Martins

Ovaia

Noronha

2013

Lithos

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“…In the Vila Pouca de Aguiar and the Águas Frias-Chaves plutons, biotite granites are the main variety and a detailed petrographic characterisation of these granites is present in Almeida et al (2002).…”

Section: Geological Settingmentioning

confidence: 99%

Genesis and emplacement of felsic Variscan plutons within a deep crustal lineation, the Penacova-Régua-Verín fault: An integrated geophysics and geochemical study (NW Iberian Peninsula)

Martins

Sant'Ovaia

Noronha

2009

Lithos

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Multidisciplinary studies integrating, U-Pb geochronology, whole-rock geochemical data, isotope geochemistry, anisotropy of magnetic susceptibility (AMS) studies and gravimetry were carried out on the Vila Pouca de Aguiar and the Águas Frias-Chaves porphyritic biotite granite plutons. Both plutons occur independently in a distance of about 20 km. The Vila Pouca de Aguiar and Águas Frias-Chaves plutons are examples of late to post-orogenic felsic Variscan granites in northern Portugal (NW Iberian Peninsula). The U-Pb zircon analyses yield a consistent age of 299 ± 3 Ma which is considered to be the emplacement age of the two plutons. These granites are weakly peraluminous, show high HREE and Y (and low P) contents which are consistent with them being I-type. This is also supported by their weakly evolved isotopic compositions, 87 Sr/ 86 Sr i = 0.7044-0.7077 and εNd = − 2.0 to − 2.6, as well as by the whole rock oxygen isotope (δ 18 O VSMOW) ranging from + 9.7‰ to + 11.0‰. The emplacement of granite magma took place after the third Variscan deformation phase (D 3 ) in an extensional tectonic regime, large scale uplift and crustal thinning. The integration of different data suggests that both plutons have the same feeding zone aligned within the Penacova-Régua-Verin fault (PRVF) and that both have the same structure which is related to late Variscan phases. The thicker shape for the Águas Frias-Chaves pluton comparing to that of the Vila Pouca de Aguiar pluton is compatible with different depths of PRVF sectors. The available data led us to propose a model of partial melting of a meta-igneous lower crustal source rather than an open-system of mantle-crust interaction. The interaction between the continental crust and invading mafic magmas could have been limited to mere heat transfer and, perhaps, local intermingling.

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“…The U-Pb zircon dating yields a consistent age of 299 ± 3 Ma (Martins et al, 2009). The Vieira do Minho pluton is composed by the porphyrytic coarse-grained Vieira do Minho granite (VMG) and the medium-grained Moreira de Rei granite (MRG), both are biotite bearing granitic rocks of monzonitic-granodioritic composition (Almeida et al 2002;Martins et al 2013). They are peraluminous with A/CNK ranging from 1.04 to 1.24, and with a I-S transitional type affinity.…”

Section: Geological and Petrological Featuresmentioning

confidence: 98%