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- Late Strunian age : a key time frame for VMS deposit exploration in the Iberian Pyrite BeltPublication . Matos, João Xavier; Pereira, Zélia; Rosa, Carlos J. P.; Rosa, Diogo; Oliveira, José Tomás; Relvas, Jorge M.R.S.Estimate of geological environments favorable for the formation of massive sulphide deposits is an important goal to the exploration companies working in the Iberian Pyrite Belt (IPB), the main European VMS base metals province, with giant deposits such as Neves Corvo, Aljustrel (Portugal), Rio Tinto and Tharsis (Spain). Palynostratigraphic research programs using more than 40 exploration boreholes (>30 km length) allowed the dating of the sediments of the Volcano-Sedimentary Complex (upper Devonian to upper Viséan), that host the massive sulphide deposits. Research is based on detailed palynomorphs study. Careful work was focused on dark grey and black shale units that host stockwork and massive ore mineralizations. Felsic volcanic U/Pb age data was also used to confirm the sediment age.Late Strunian (miospore biozone LN, 360.7 ± 0.7 Ma -362 Ma) sediments host the massive sulphide ore at Neves Corvo, Lousal, Caveira and Montinho, mines located in the Portuguese IPB sector. In Spain similar data was obtained at Aznalcollar and Tharsis. The agedata show a favourable geological period of ~2 Ma were paleogeographic conditions were extremely favorable to hydrothermal fluid circulation and VMS deposits formation. Late Strunian age therefore becomes one key exploration guide in IPB.
- O Complexo Vulcano-Sedimentar de Toca da Moura-Cabrela (Zona de Ossa Morena) : evolução tectono-estratigráfica e mineralizações associadasPublication . Oliveira, José Tomás; Relvas, Jorge M.R.S.; Pereira, Zélia; Munhá, José; Matos, João Xavier; Barriga, Fernando; Rosa, Carlos J. P.
- From source to surface: clues from garnet-bearing Carboniferous silicic volcanic rocks, Iberian Pyrite Belt, PortugalPublication . Cravinho, André; Rosa, Diogo; Relvas, Jorge M.R.S.; Solá, A. Rita; Pereira, Inês; Paquette, J. L.; Borba, M. L.; Tassinari, Colombo C. G.; Chew, David; Drakou, Foteini; Breiter, Karel; Araújo, VítorABSTRACT: This work investigates the relationships between partial melting, melt extraction, pluton growth and silicic volcanism in garnet-bearing felsic volcanic rocks that were extruded in the Iberian Pyrite Belt, at ca. 345 Ma. The garnets are of peritectic origin, displaying textural and chemical features of disequilibrium crystallization during partial melting reactions involving biotite at high temperatures (up to 870 degrees C) in the middle-lower crust. Major element composition suggests compositional equilibrium with the entrained and pinitized peritectic cordierite, but reveals some subsequent homogenization by diffusion. Trace element maps and spot analyses of garnet show, nonetheless, significant trace element variations, reflecting biotite and Y-REE-P-rich accessory phase breakdown during partial melting reactions. Peritectic garnet and cordierite growth resulted in the preservation of Th- and Y-rich prograde suprasolidus monazite, which constrains the timing of partial melting of the metapelitic protolith at ca. 356.8 +/- 2.4 Ma. The zircon cargo further shows that a significant amount of zircon crystals from previously crystallized felsic melts were also remobilized and erupted. These were likely stored in an upper crustal pluton that grew episodically since ca. 390 Ma during voluminous melt generation periods within the middle to lower crust, which also resulted in voluminous volcanism. The geochemical trends of the felsic volcanic rocks reflect the entrainment of xenoliths of peritectic garnet, cordierite and feldspar, and as such, the garnet-bearing felsic volcanic rocks represent an erupted mixture of a lower-temperature (ca. 770 degrees C) silicic melt and autocrysts, and peritectic phases and zircon crystals from previously crystallized and stored felsic melts.
- Volcanic facies architecture, hydrothermal alteration and subsea-floor replacement at the Neves Corvo deposit, Iberian Pyrite BeltPublication . Rosa, Carlos J. P.; Relvas, Jorge M.R.S.; McPhie, Jocelyn; Pereira, Zélia; Oliveira, José Tomás; Pacheco, Nelson; Barriga, FernandoThree felsic volcanic sequences constitute the host succession to the Neves Corvo VHMS deposit. The lower volcanic sequence (late Famennian) consists of a rhyolitic fiamme-rich facies association that comprises polymictic and overall graded quartzphyric fiamme breccia units (up to 60 m thick). These units have pyroclastic origin and constitute the substrate to the rhyolite facies association (intermediate volcanic sequence). The rhyolite facies association (late Strunian) comprises intervals of coherent quartz-feldspar-phyric rhyolite (up to 10 m thick) that are enclosed by much thicker intervals (up to 250 m) of jigsaw-fit and clast-rotated monomictic rhyolite breccia. Laterally these breccias grade to beds of monomictic rhyolite breccia that alternate with crystal-rich sandstone. The units defined by the rhyolite facies association are rhyolitic lavas. The massive sulfide orebodies (late Strunian) directly overly the lavas or are interleaved with relatively thin (up to 50 m) intervals of mudstone. The upper volcanic sequence (early Visean) consists of a thin interval of monomictic dacite breccia. The host succession to the Neves Corvo orebodies thus comprises proximal to source vent deposits from submarine explosive and effusive eruptions. However, the ore-forming process relates both in time and space with the rhyolitic lavas, which are coeval with the mineralization. Neves Corvo is well known for its high-grade Cu ores and unique cassiterite mineralization. Ore-related hydrothermal activity overprints an early metasomatic stage and relates with a multi-sourced hydrothermal system, responsible for early stringer and massive cassiterite deposition and subsequent massive sulfide oregeneration. In the Corvo orebody, the early deposition of massive cassiterite ores was fed by an independent stockwork in a tectonically-bounded alignment. Textural and petrographic analyses, geochemistry and oxygen-isotope data indicate brusque flushing of the tin-bearing fluid into seawater after minimal fluid-rock interaction during up flow. Massive sulfide-related hydrothermal alteration is essentially stratabound and controlled by permeability contrasts. Alteration zonation is classical, consisting of an inner chlorite/donbassite-quartz-sulfides-(sericite) core that grades into sericitequartz- sulfides-(chlorite) and paragonite-quartz-sulfides-(chlorite) peripheral envelopes. The aluminous hydrothermal alteration mineralogy coupled with elemental and stable isotope geochemistry indicates very low pH, unusually high maximum interaction temperature and predominant low-sulfidation alteration/mineralization conditions. Textural and mass-balance analyses show extensive silicate-sulfide replacement in the coherent volcanic rocks of the footwall sequence, and disseminated replacement mineralization in the volcaniclatic/sedimentary units.
- Definition of the Portuguese frameworks with international relevance as an input for the European geological heritage characterisationPublication . Brilha, José Bernardo; Andrade, César; Azerêdo, Ana Cristina; Barriga, Fernando; Cachão, Mário; Couto, Helena; Cunha, Pedro Proença e; Crispim, José António; Dantas, Pedro; Duarte, Luís Victor; Freitas, Maria da Conceição; Granja, Helena Maria; Henriques, Maria Helena; Lopes, L.; Madeira, José; Matos, João Xavier; Noronha, Fernando; Pais, João; Piçarra, José Manuel; Ramalho, Miguel Magalhães; Relvas, Jorge M.R.S.; Ribeiro, António; Santos, A.; Santos, Vanda Faria dos; Terrinha, Pedro
- The volcanic-sedimentary sequence of the Lousal deposit, Iberian Pyrite Belt, Portugal [Abstract]Publication . Rosa, Carlos J. P.; Rosa, Diogo; Matos, João Xavier; Relvas, Jorge M.R.S.
- Cartografia de facies vulcânicas aplicada à prospecção de recursos mineraisPublication . Rosa, Carlos J. P.; Relvas, Jorge M.R.S.
- Lava-cryptodome-pumice cone volcanoes in the Iberian Pyrite BeltPublication . Rosa, Carlos J. P.; McPhie, Jocelyn; Relvas, Jorge M.R.S.
- The potential for magnetic metal sources in the Iberian Pyrite Belt [Poster]Publication . Marques, A. F. A.; Scott, S. D.; Relvas, Jorge M.R.S.; Rosa, Carlos J. P.; Guillong, M.
- Sn and Cu in melt inclusions of the Albernoa felsic volcanic centre, Iberian Pyrite Belt, Portugal : seeking for the missing (magmatic) linkPublication . Marques, A. F. A.; Scott, S. D.; Relvas, Jorge M.R.S.; Rosa, Carlos J. P.; Barriga, Fernando