Geossítios
GEO

Gossan (chapéu de ferro) do depósito de Algares

justificação do valor científico

The Algares massive sulphide orebody, mined out, outcrops through an imposing gossan more than 900 m long and up to 35 m thick. This is a true landmark, not only because of the red hues of the oxidised sulphides, but also by the presence, equally imposing, of the Viana and Vipasca iron headframes above their respective shafts (Schermerhorn et al. 1983, Silva et al. 1997, Leitão 1998, Matos et al. 2003, 2008, 2009). Algares is also the main sector of the Vipasca Roman mine. Some Roman galleries and shafts are still visible (Martins et al. 2003). Because the orebody is vertical and relatively thin, mining was never in open pit, which provided a high degree of preservation. This has permitted its present status of a geological monument of excellence, integrated in the geo/eco-mining transect of Aljustrel, created in 2006 by LNEG, the Aljustrel municipality and CCDR Alentejo 
Geosite of Iberian dimension in the context of the Iberian Pyrite Belt. Concerning archaeology, however, Algares attains international status, in view of the Roman mining works of the Vipasca Mine, one of the main mining centres of the Roman Empire (Martins et al. 2003, Matos et al. 2008).

References:
Alves, H., Martins, A. (2005) – Aljustrel, um olhar sobre as minas e as gentes no séc. XX. CM Aljustrel, Portugal, 133pp..
Coelho, C., Valente, S, Figueiredo, E., Ribeiro, C., Matos, J.X. (2007) Avaliação dos impactos socioeconómicos da actividade mineira na Vila de Aljustrel: O contributo do Projecto EVALUSE. IX Sem. Ambiente, Un. Aveiro, 6pp..
Leitão, J. (1998) – Geologia dos depósitos de sulfuretos maciços de Aljustrel. Liv.-Guia V Cong. Nac. Geologia, IGM, pp.91-100.
Martins, A., Alves, H. e Costa, T. (2003). 2000 anos de mineração em Aljustrel. Câmara Municipal de Aljustrel, Portugal, 78pp..
Martins, J., Carvalho, P. (2005) – Recuperação ambiental da área mineira de Aljustrel. Abst. III Enc. Com. Mineiras Aljustrel, CM Aljustrel.
Matos, J.X., Barriga, F.J.A.S., Oliveira, V. (2003) Alunite veins versus supergene kaolinite/halloysite alteration in the Lagoa Salgada, Algares and S. João (Aljustrel) and S. Domingos massive sulphide deposits, IPB, Portugal. Ciências da Terra, Lisboa, V, pp. B56-B59.
Matos, J.X., Martins, L. (2006) Reabilitação ambiental de áreas mineiras do sector português da Faixa Piritosa Ibérica: estado da arte e perspectivas futuras. IGME, Bol. Geológico y Minero España, v. 117, nº2, pp. 289-304.
Matos, J.X., Martins, L.P., Martins, A., Pedro, C., Franco, A. (2008) O chapéu de ferro de Algares, proposta de um Jardim Geológico para a mina de Aljustrel, Faixa Piritosa Ibérica, Portugal. V Cong. Int. SEDPGYM Minería y Metalurgia Históricas SW Europeo, León, Spain, pp. 66.
Matos, J.X., Martins, L.P., Oliveira, J.T., Pereira, Z., Batista, M.J., Quental, L. (2008) Rota da pirite no sector português da Faixa Piritosa Ibérica, desafios para um desenvolvimento sustentado do turismo geológico e mineiro. Projecto RUMYS, programa CYTED, Livro Rutas Minerales en Iberoamérica, Ed. Paul Carrion, Esc. Sup. Politécnica del Litoral, Guayaquil, Equador, pp 136-155.
Matos, J. X. (2009) Ampliação e desenvolvimento da Rota da Pirite através da inclusão dos jardins geológicos de Algares e Lousal, Faixa Piritosa Ibérica, Portugal. Projecto RUMYS, programa CYTED, Livro Rutas Minerales y Sostenibilidad, Ed. Paul Carrion, Esc. Sup. Politécnica del Litoral, Guayaquil, Equador, pp 113-121.
Schermerhorn L., Zbyzewski, G., Ferreira, V. (1987) – Carta Geológica 42D Aljustrel, SGP, 55pp.
Silva JMB, V Oliveira, J Matos, JC Leitão, 1997. Field Trip #2: Aljustrel and the Central Iberian Pyrite Belt. In Barriga FJAS, Carvalho D, eds, 1997. Geology and VMS Deposits of the Iberian Pyrite Belt, Society of Economic Geologists Guidebook Series, Boulder, Colorado, USA, vol 27, 192 p

Outros valores e sua justificação

The Algares gossan occurs within the main historical area of the Aljustrel mine. There is a project to create a Geological Garden, by LNEG and the Aljustrel municipality, to include the orebody with its Roman woks, the aforementioned headframes, the Transtagana smokestack recently recovered by EDM, the Compressors plant, and modern galleries. The latter, after rubble removal, will be able to host underground visits over 500 m long (Matos et al. 2008). There will be specific walking trails, for Roman and modern mining, metallogeny, mineralogy, stratigraphy and structural geology. The conservation of Algares will also bring added value to nearby mining infrastructures, such as the copper cementation tanks, the Roman slag heaps, the ore stores and the miners quarters of Vadoca and Santa Bárbara (Alves & Martins 2005). Mining tourism has been highly ranked as an option for sustainable economy for the Aljustrel region in technical studies on the subject (Coelho et al. 2007).

Observações

Coordenadas em actualização.