Volcanic architecture in the Odiel river area and the volcanic environment in the Riotinto–Nerva Unit, Iberian Pyrite Belt, Spain

In order to assess the volcanic architecture of the VSC in the Iberian Pyrite Belt, Spain, a study of the volcanic and sedimentary lithofacies has been undertaken on a section up to 1000 m thick in the Odiel river, considered to be also representative of other areas of the Riotinto–Nerva Unit. Among other mineral deposits, this unit includes the world-class volcanic-hosted massive sulfide deposits of the Riotinto mining district.Several conclusions have been obtained: a) a complex, thick volcanic succession, as well as mafic and felsic sills and thin sedimentary intervals, predated the genesis of the sulfide deposits, which did not form in a dominantly sedimentary environment; b) two successive, felsic volcanic sequences can be distinguished, showing textural and chemical variations from bottom to top; c) mafic lithofacies decrease upwards in the sequence, and d) volcanic structures, eruption style and internal organization suggest a deep subaqueous depositional environment, which agrees with the depositional setting for massive sulfide deposits.

Research Highlights
► The Odiel river is not a sill-sediment complex, but a bimodal volcanic succession.
► Basic rocks are more abundant towards the bottom of the stratigraphic column.
► We distinguish two contrasting rhyolitic successions.
► We describe submarine felsic volcanic rocks, partly constituting Neptunian deposits.
► VHMS deposits in the Riotinto-Nerva unit postdate a thick volcanic succession.