Geochemistry and geochronology of the Palaeozoic mafic magmatism in the Codosera, Almadén and Guadalmez synclines, Central Iberian Zone, Spain

The Central Iberian Zone (CIZ) hosts several mafic suites showing variable geochemical affinities and signatures evolving through time. To provide a better understanding of magmatic processes, possible sources and the temporal evolution of the mafic magmatism in the CIZ, this work presents new geochemical and geochronological data on mafic intrusions hosted by three structures: the Guadalmez syncline (GS), the Almadén syncline (AS) and the Codosera syncline (CS). According to the U-Pb dating on apatite, the alkaline dolerites from the GS and AS were emplaced during at least two events, the first one at the end of the Silurian, and the second one during the upper Devonian to Carboniferous. The mafic rocks from the CS present a transitional affinity and were emplaced during the Carboniferous, either as a single major event around 348±33Ma or as a series of discrete events between 359 ± 22 Ma and 332 ± 17 Ma. They are therefore associated with the first stages of the Variscan orogeny. The mafic suites of the AS and GS show no evidence of crustal contamination, whereas the rocks from the CS may have experienced slight crustal contamination. All studied rocks show an enrichment in LREE, high Gd/Yb>2.9 and Ti/Y>554 ratios; likely indicating the presence of residual garnet in the mantle source. Some of the mafic rocks in this study are contemporaneous with a mafic magmatic event already reported in the Armorican Massif. This allows us to propose the existence of a widespread mafic magmatic event that took place between the Upper Devonian to the Mississippian in both the Central Iberian Zone and in the Armorican Massif at around 360 Ma.