RM - Comunicações em actas de encontros científicos internacionais
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- Preliminary study of quartz gravel and veins occurring in the Equimina region, Benguela (Angola): potential uses in industryPublication . Lisboa, Jose; Pereira, L. F.; Osório, A.; Rodrigues, José Feliciano; Fernández, J.; Oliveira, Álvaro; Manuel, JoséABSTRACT: Vast occurrences of quartz in veins and extensive gravel beds in the coastal area of Equimina, approximately 100 km south of Benguela, constitute the object of this study, aiming for its industrial use. These occurrences are related to Paleoproterozoic gneisses and migmatites on which they outcrop. The veins are quite dismantled on the surface, and show a pronounced strike scattering, but the NE-SW orientation prevails. Some veins are pegmatitic (feldspar, quartz, and mica), others, if not the majority to the East in the study area, have a strong predominance of milky quartz with low content of other minerals. Except for a superficial and removable patina of iron oxides that often coats the quartz, it is free of visible impurities. Chemical analysis confirms high purity (SiO2 > 99.5%) and very low content of penalizing oxides. Although the composition of quartz is suitable for use in the ceramic and glass industry, due to the ways it occurs, the main potential of this abundant resource in the studied area is for the refractory and metallurgy industry. Besides the chemical composition, the size of the gravel mostly meets the dimensional requirements for silicon metal production, needing minimal beneficiation.
- A critical look at raw materials criticalityPublication . de Oliveira, Daniel Pipa SoaresABSTRACT: In the eve of the proposed Critical Raw Materials Act published in March of 2023, Europe has realized that even with already predicted exponential growth in raw materials supply, the situation remains critical with regards provision of these (critical) raw materials (CRM). The various initiatives led by the EU Commission starting with the Raw Materials Initiative in 2008, the various CRM lists (2011, 2014, 2017, 2020 and 2023), the launch of several dedicated CRM task forces (e.g., ERECON), alliances (E.G., ERMA) and the objectives of the EU Green Deal mean that in a few short years, 7 in fact, the EU needs to find new sources for CRM. An impossible task.
- Selénio retido por minerais das fumarolas vulcânicas na Ilha do Fogo (Cabo Verde)Publication . Silva, Teresa; de Oliveira, Daniel Pipa Soares; Veiga, JP; Ávila, Paula Freire; Candeias, Carla; Salas-Colera, Eduardo; Caldeira, Rita
- Nature conservation, land use planning and exploitation of ornamental stonesPublication . Carvalho, Jorge; Meira, João; Marques, Célia; Machado, Susana; Mergulhão, Lia; Cancela, JorgeABSTRACT: Cabeça Veada is the name of a relatively small exploitation cluster for ornamental limestones occupying an area of 98 ha in the Portuguese Natural Park of Serra de Aire e Candeeiros, which is also a Natura 2000 Network protected area. Supported by comprehensive geological, mining and environmental studies, a specific methodology was developed in order to address the compatibility between the long term sustainability of this industry with the preservation of existing protected natural values. The obtained land use map should allow the Cabeça Veada mineral resources to be adequately included in the municipal land use planning process.
- New data on nodular monazite from Monfortinho (Idanha-a-Nova, Portugal)Publication . Salgueiro, Rute; Inverno, Carlos; De Oliveira, Daniel Pipa Soares; Guimarães, Fernanda
- Roman slag distribution in the Portuguese sector of the Iberian Pyrite BeltPublication . Matos, João Xavier; Martins, A.; Rego, M.; Mateus, António; Pinto, A.; Figueiras, Jorge; Silva, E.
- Os Scavrarii de VipascaPublication . Pérez Macias, Juan Aurélio; Matos, João Xavier; Martins, Artur
- Structure, stratigraphy and hydrothermal alteration at the Gavião orebodies, Aljustrel : reconstruction of a dismembered ore-forming system at the Iberian Pyrite Belt and implications for explorationPublication . Relvas, Jorge M.R.S.; Barriga, Fernando; Carvalho, João R. S.; Pinto, Álvaro M. M.; Matos, João Xavier; Rosa, Carlos J. P.; Pereira, Zélia
- Characterization of placer gold deposits from central Portugal : preliminary resultsPublication . Ehser, Anja; Borg, Gregor; de Oliveira, Daniel Pipa Soares; Rosa, Diogo; Salgueiro, Rute
- Gold in the Lousal mine, Iberian Pyrite Belt, PortugalPublication . de Oliveira, Daniel Pipa Soares; Guimarães, Fernanda; Matos, João Xavier; Rosa, Diogo; Rosa, Carlos J. P.; Castelo-Branco, José MárioRecent exploration boreholes in the Lousal Mine, located within the Portuguese sector of the Iberian Pyrite Belt (IPB) yielded marked concentrations in gold/electrum in a section of core consisting of banded metasediments with massive pyrite. Preliminary research indicates that the gold is associated with native bismuth and bismuthinite and is clearly late in the paragenetic sequence occurring in fine chalcopyrite (± covellite)-bismuthinite-gold filled veinlets within the dominant and more massive pyrite. The pale yellow gold grains are fine, seldom reaching more than 6 ..m in length and half of that in thickness. EPMA results indicate that silver concentrations in gold grains can be as high as 27 wt.%. The results show similarities with conclusions drawn from the IPB on the Spanish side where gold of Co-Bi geochemical association is found as electrum with abundant to common Co and Bi minerals. These associated with pyrite and/or chalcopyrite are characterized by an abundance of sedimentary facies and show that the gold association formed at high temperature (>300 °C) during the initial phases of massive sulphide formation.
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