Petrogenesis of Permian alkaline lamprophyres and diabases from the Spanish Central System and their geodynamic context within western Europe

Abstract

Basic to ultrabasic alkaline lamprophyres and diabases intruded within the Spanish

40 Ar/ 39 Ar phlogopite geochronology of lamprophyre dykes in Cornwall, UK: new age constraints on Early Permian post-collisional magmatism in the Rhenohercynian Zone, SW England

“…1) including the Rhenohercynian and Saxothuringian Zones of the Bohemian Massif (c. 334-323 Ma and c. 297-295 Ma;von Seckendorff et al 2004;Hegner et al 1998), the Central Iberian Zone of the Iberian Massif (c. 265 Ma; Scarrow et al 2011;Orejana et al 2008;Bea et al 1999) (Scarrow et al 2011), and (iii) an association in space and time with voluminous intermediate-felsic batholiths (e.g. Bea et al 1999;von Seckendorff et al 2004).…”

Mineral chemistry of late Variscan gabbros from central Spain: constraints on crystallisation processes and nature of the parental magmas

“…300 Ma would register a previous and different mantle source. This transformation of the lithospheric (and asthenospheric) mantle under central Spain has been associated with delamination of dense crustal blocks in the thickened Variscan collisional belt, which is supported by Sm-Nd isotopic signatures of pre-Variscan, Variscan and post-Variscan basic magmas (e.g., Villaseca et al, 2004;Orejana et al, 2008;Gutierrez-Alonso et al, 2011).…”

“…264 Ma; e.g., Scarrow et al, 2006;Perini and Timmerman, 2008), which intrude about 35 Ma after the Variscan gabbros are emplaced (305-300 Ma; Villaseca et al, 2011), in a fairly different tectonic regime. Some of these alkaline dykes display isotopically depleted signatures (eNd ~ +7; Orejana et al, 2008), which suggests that metasomatism in the source mantle likely occurred shortly before alkaline melt generation (Orejana et al, 2008). The Variscan basic magmatism at ca.…”

“…The only basic alkaline magmatic rocks outcropping in the SCS are lamprophyric and diabasic dykes (Orejana et al, 2008) of Permian age (ca. 264 Ma; e.g., Scarrow et al, 2006;Perini and Timmerman, 2008), which intrude about 35 Ma after the Variscan gabbros are emplaced (305-300 Ma; Villaseca et al, 2011), in a fairly different tectonic regime.…”

“…The alkaline and tholeiitic mafic rocks are post-Variscan dyke swarms associated with a rifting regime prior to the Atlantic Ocean opening (e.g. Cebriá et al, 2003;Orejana et al, 2008). The calc-alkaline gabbroic intrusions, which are mainly concentrated in the western SCS (Franco and García de Figuerola, 1986;Franco and Sánchez-García, 1987), are small (usually < 1 km in length) Variscan post-tectonic plutons with ages mainly in the range 305-300 Ma (Zeck et al, 2007;Villaseca et al, 2011).…”