Geology of the recently discovered massive and stockwork sulphide mineralization at Semblana, Rosa Magra and Monte Branco, Neves–Corvo mine region, Iberian Pyrite Belt, Portugal

Abstract

The recently discovered massive and stockwork sulphide mineralization of Semblana-Rosa Magra and Monte Branco, situated ESE of the Neves–Corvo volcanogenic massive sulphide (VMS) deposit in the Iberian Pyrite Belt (IPB) is presented. Geological setting and tectonic model is discussed based on proxies such as palynostratigraphy and U–Pb zircon geochronology. The mineralization is found within the IPB Volcano-Sedimentary Complex (VSC) Lower sequence, which includes felsic volcanic rocks (rhyolites) with U–Pb ages in zircons of 359.6 ± 1.6 Ma, and black shales of the Neves Formation of late Strunian age. Massive sulphides are enveloped by these shales, implying that felsic volcanism, mineralization and shale sedimentation are essentially coeval. This circumstance is considered highly prospective, as it represents an important exploration vector to target VMS mineralization across the IPB, in areas where the Lower VSC sequence is present. The Upper VSC sequence, with siliciclastic and volcanogenic sedimentary rocks of middle–late Visean age, shows no massive mineralization but a late Tournaisian (350.9 ± 2.3 Ma) volcanism with disseminated sulphides was also identified. Nevertheless, stratigraphic palynological gaps were found within the Strunian and in the Tournaisian sediments, between the Lower and Upper VSC sequences, reflecting probable erosion and uplift mechanisms linked with extensional tectonics. The Semblana and Monte Branco deposits and the Rosa Magra stockwork are enclosed by tectonic sheets that dismembered the VSC sequence in a fold-and-thrust tectonic complex, characteristic of the NE Neves–Corvo region. The methodologies used allow a geological comparison between Neves–Corvo and other IPB mine regions such as Lousal–Caveira, Herrerias, Tharsis and Aznalcollar.

A new approach to palynostratigraphy of the middle–late Famennian Gafo Formation, southern sector of the Pulo do Lobo Domain, SW Iberia (Portugal and Spain)

“…Nevertheless, more detailed palynostratigraphic studies are needed to confirm this hypothesis. A similar age and palynoassemblage are found in the Represa and Phyllite-Quartzite Formations of the IPB Phyllite-Quartzite Group (Cunha & Oliveira, 1989;Pereira et al 2008Pereira et al , 2014Pereira et al , 2021Oliveira et al 2013).…”

Maiaspora: the hallmark of gleichenioid ferns (Gleicheniales) from the early Carboniferous

“…The gleichenioids would have a neoendemic distribution at the onset of their divergence during the Visean. The earliest records of M. concava are from the volcanogenic Grac ßa Formation in the volcanic-sedimentary complex of the Iberian Pyrite Belt (Pereira et al 2003(Pereira et al , 2008(Pereira et al , 2021Oliveira et al 2013Oliveira et al , 2019. The Grac ßa Formation belongs to the Visean K. triradiatus -K. stephanephorus (TS) Biozone.…”

Detrital zircon similarities and dissimilarities between the Iberian Pyrite Belt, Ossa-Morena Zone and Meguma

“…Braid et al, 2011). The Phyllite-Quartzite Group is overlain by the Volcano-Sedimentary Complex, which comprises a Famennian-Tournaisian succession hosting an outstanding volcanogenic massive sulphide (VMS) province, which includes the giant polymetallic sulphide mineralisations of the renowned Neves-Corvo, Aljustrel and Riotinto mines (Lains Leistel et al, 1997;Oliveira et al, 2004;Pereira et al, 2021b;Valenzuela et al, 2011). In the IPB easternmost side, the metamorphosed sedimentary sequences, similar in age to the lower units of the Phyllite-Quartzite Formation (late Givetian-Frasnian?…”