Boletín de la Sociedad Geológica Mexicana Volumen 71, núm. 2, 2019, p. 321 ‒ 342 http://dx.doi.org/10.18268/ BSGM2019v71n2a6

Geological context and origin of the mineralization of the historic and prehistoric iron mines in the Gavà area, Catalonia, NE Iberian Peninsula

Yael Díaz-Acha^1,*, Marc Campeny¹, Joan Carles Melgarejo², Josep Bosch³, Saleh Lehbib⁴, Lisard Torró⁵, Joaquín A. Proenza², Montgarri Castillo- Oliver⁶, Antoni Camprubí⁷, Cristina Villanova-de-Benavent⁸, Aleu Andreazini², Míriam Pastor², Núria Pujol-Solà², Sandra Amores², Jingyao Xu², Júlia Farré²

¹Museu de Ciències Naturals de Barcelona. Parc de la Ciutadella s/n, 08003 Barcelona, Spain.

² Departament de Mineralogia, Petrologia i Geologia Aplicada, Facultat de Ciències de la Terra, Universitat de Barcelona. Martí i Franquès s/n, 08028 Barcelona, Spain.

³Museu de Gavà. Plaça de Dolors Clua, 13, 08850 Gavà, Barcelona, Spain.

⁴Departament de Mineralogia, Petrologia i Geologia Aplicada, Facultat de Ciències de la Terra, Universitat de Barcelona. Martí i Franquès s/n, 08028 Barcelona, Spain.

Ministery of Water and the Environment, Sahrawi Arab Democratic Republic.

⁵Departament de Mineralogia, Petrologia i Geologia Aplicada, Facultat de Ciències de la Terra, Universitat de Barcelona. Martí i Franquès s/n, 08028 Barcelona, Spain.

Departament de Geologia, Facultat de Ciències, Universitat Autònoma de Barcelona. Edifici Cs, 08193 Bellaterra (Cerdanyola del Vallès), Spain.

Departamento de Ingeniería de Minas, Pontificia Universidad Católica de Perú. Avenida Universitaria 1801, San Miguel, Lima 32, Peru.

⁶Departament de Mineralogia, Petrologia i Geologia Aplicada, Facultat de Ciències de la Terra, Universitat de Barcelona. Martí i Franquès s/n, 08028 Barcelona, Spain.

ARC Centre of Excellence for Core to Crust Fluid Systems and GEMOC, Department of Earth and Planetary Sciences, Macquarie University.NSW 2019, Australia.

⁷Instituto de Geología, Universidad Nacional Autónoma de México. Ciudad Universitaria, 04510 Coyoacán, CDMX, Mexico.

⁸School of Environment and Technology, University of Brighton. Mithras House, Lewes Rd., Brighton BN2 4AT, United Kingdom.

* This email address is being protected from spambots. You need JavaScript enabled to view it.

Abstract

Mining for iron resources in the Gavà area of Catalonia occurred intermittently during the Iberian and Roman epochs, the Middle Ages, and continuing until the industrial era, as evidenced by historical and archaeological documents. Iron mining in this area could have occurred even earlier, during the Neolithic period. Iron ores were formed in two stages: (1) a regional hydrothermal alteration associated with Hercynian thrusts that produced the ankeritization of limestones within the Paleozoic series, and (2) the karstic replacement of these iron-rich carbonates during the Pliocene and Quaternary by means of supergenic fluids that produced ochres with goethite and hematite. The style of mineralization largely depends on the characteristics of the replaced protolith, and three styles of mineralization can be defined: (1)The supergenic replacement of ankeritized massive Pridolian limestones only produced local replacements that were restricted to structural or stratigraphic discontinuities, therefore, the mineralization has reduced dimensions and occurs as irregular veinlets or pipes; (2) The replacement of interbedded ankeritized limestones and pyrite-bearing shales (Lockovian) produced massive ores in pod-shaped bodies rich in silica impurities derived from the altered shales; and (3) The replacement of carbonates overthrust by pyrite- and phosphate-rich shales favored the formation of massive stratabound deposits, which are the largest and highest grade deposits in the study area, and may be locally enriched in minerals of the alunite supergroup and Ca- and Fe-rich phosphates. Outcrops of all of these styles of mineralization were mined by the Iberian cultures, during the roman period and in the Middle Ages, taking advantage of the relatively high metallurgical quality of the ores.Therefore, the exploitation during these epochs was artisanal by means of trenches or small pits. In contrast, during the industrial era only the massive stratabound deposits were exploited in open pits and underground galleries.

Keywords: iron mining, karst, supergenic, phosphates, alunite, Iberian culture.