Hybrid zones from the Seville Sierra Norte Batholith: the missing Late Famennian plutonic basement of the Iberian Pyrite Belt

Abstract

Subvolcanic rocks from hybrid zones provide insights into the parental magmas present in calc-alkaline arc systems. Determining the composition and formation conditions of the parental magma is essential for linking plutonic and volcanic rocks to a common source.

Here, we investigate the genetic relationships between plutonic rocks from the bimodal Seville Sierra Norte Batholith (SSNB) and coeval bimodal volcanic rocks from the Iberian Pyrite Belt, one of the largest massive sulfide provinces on Earth, hosted by the Volcanic–Sedimentary Complex in the South Portuguese Zone (Iberian Variscan Belt). Metadata analysis of geochemical signatures from the SSNB and the Volcanic–Sedimentary Complex indicates a common arc-like magma source. The Gerena hybrid zone, located in the southern section of the SSNB, provides evidence of a genetic link between mafic and felsic end members of this magmatism. Experiments on the hybrid zone, performed at 300 MPa and 1000°C, and subsequently quenched, produced a liquid composition consistent with the Andean cotectic. Furthermore, the crystallization ages of the granodiorites (356 ± 1 Ma) and quartz-diorites from the Gerena hybrid zone (368 ± 3 Ma) overlap the age range of volcanic felsic rocks from the Iberian Pyrite Belt. We propose that: (i) the quartz-diorite of the Gerena hybrid zone corresponds to the missing Late Famennian plutonic roots of the Iberian Pyrite Belt; and (ii) the Late Famennian–Tournaisian arc-like magmatism in the South Portuguese Zone was related to the termination of subduction of the Rheic oceanic lithosphere. Our findings can help in understanding the links between magmatic systems and metallogenic provinces.