The Neolithic variscite mines of Gavà, Catalonia: Criteria for mineral exploration and exploitation in the Prehistory
Por:
Diaz-Acha, Yael, Melgarejo J.C., Bosch J., Andreazini, Aleu, Pastor, Miriam, Pujol-Sola, Nuria, Campeny M., Torró L., Villanova-de-Benavent C., Castillo-Oliver M., Lehbib S., Camprubí A., Proenza J.A.
Publicada:
1 ene 2019
Categoría:
Earth and planetary sciences (miscellaneous)
Resumen:
The Gavà Neolithic Mining Complex (GNMC) located in Catalonia was devoted to the exploitation of green variscite used in the crafting of ornaments. Archaeological works in more than 100 mines indicated that this mining activity was carried out ~5800 years before present. GNMC constitutes (1) one of the earliest known examples of underground mining in Europe, (2) the earliest example of large-scale mining for ornamental use, and (C) the earliest of the application of complex geological and mining concepts. In the GNMC variscite is found as two distinct styles: (1) replacement of thin fluorapatite beds, which are interbedded with pyritic organic-rich black shales of Silurian age; and (2) veinlets crosscutting these materials. This set of geological materials is unconformably covered locally by Quaternary calcretes. Variscite formed as a result of Quaternary supergene processes, which oxidized the pyrite and produced acidic, oxidized solutions. The resulting fluids mobilized phosphate from apatite and leached Al and organic matter out of Silurian shales, thus leading to the precipitation of the Al-rich phosphates as vein infillings and strata-bound replacements after apatite. The formation of variscite is restricted to the extent of the oxidizing front, and variscite of both mineralization styles changes in color from yellowish green near the surface to deep green in depth. The study area contains two mining fields: Can Tintorer and Can Badosa-Les Ferreres range. The presence of abundant subvertical variscite veins in Can Tintorer allowed a complex development of galleries at different exploitation levels communicated by shafts and ramps, achieving 15 meters depth. The exploitation by Neolithic miners was by overhand and underhand stoping; they also used pillars and refilling of older exploitations to avoid the mine collapsing. These mines were opened in many cases by shafts that were dug directly through hard Quaternary calcretes, favoring the galleries' stability and revealing that miners understood that mineralization continues underneath the calcrete cover. Geological mapping reveals that exploitations in the Can Badosa-Les Ferreres area are simple, showing a single entrance to simple galleries or ramps attaining less than 5 m in depth and directly excavated on phosphate outcrops. Contrastingly, the mines in the Can Tintorer area have several entrances that consist of vertical shafts through a Quaternary cover, presenting an intricate geometry with many large and communicated galleries at different depths with a system of cameras and pillars. Although the development of both mining areas was essentially contemporaneous, the Can Badosa-Les Ferreres area can only be considered an exploration area. In addition, mining was carried out on minerals adjacent to variscite, not directly on variscite veins themselves, thus indicating that the miners were effectively using a wealth of geological knowledge that was previously acquired in the complex operations in the Can Tintorer mines. © Boletín de la Sociedad Geológica Mexicana 2019.
Filiaciones:
Museu de Ciències Naturals de Barcelona, Parc de la Ciutadella s/n, Barcelona, 08003, Spain
Departament de Mineralogia, Petrologia i Geologia Aplicada, Facultat de Ciències de la Terra, Universitat de Barcelona, Martí i Franquès s/n, Barcelona, 08028, Spain
Museu de Gavà, Plaça de Dolors Clua, 13, Gavà, Barcelona, 08850, Spain
Departament de Geologia, Facultat de Ciències, Universitat Autònoma de Barcelona. Edifici Cs, Bellaterra (Cerdanyola del Vallès), 08193, Spain
Departamento de Ingeniería de Minas, Pontificia Universidad Católica de Perú, Avenida Universitaria 1801, San Miguel, Lima 32, Peru
School of Environment and Technology, University of Brighton, Mithras House, Lewes Rd., Brighton, BN2 4AT, United Kingdom
ARC Centre of Excellence for Core to Crust Fluid Systems and GEMOC, Department of Earth and Planetary Sciences, Macquarie UniversityNSW 2019, Australia
Ministery of Water and the Environment, Sahrawi Arab Democratic Republic, Morocco
Instituto de Geología, Universidad Nacional Autónoma de México. Ciudad Universitaria, Coyoacán, CDMX, 04510, Mexico
Museu Nat Barcelona, Parc Ciutadella S-N, Barcelona 08003, Spain
Univ Barcelona, Dept Mineral Petrol & Geol Aplicada, Fac Ciencies Terra, Marti i Franques S-N, E-08028 Barcelona, Spain
Museu Gava, Placa Dolors Clua 13, Barcelona 08850, Spain
Univ Autonoma Barcelona, Fac Ciencies, Dept Geol, Edifici Cs, Bellaterra 08193, Cerdanyola Del, Spain
Pontificia Univ Catolica Peru, Dept Ingn Minas, Ave Univ 1801, Lima 32, Peru
Univ Brighton, Sch Environm & Technol, Mithras House,Lewes Rd, Brighton BN2 4AT, E Sussex, England
Macquarie Univ, ARC Ctr Excellence Core Crust Fluid Syst, N Ryde, NSW 2019, Australia
Macquarie Univ, Dept Earth & Planetary Sci, GEMOC, N Ryde, NSW 2019, Australia
Minist Water & Environm, Sahrawi Arab Democratic, Morocco
Univ Nacl Autonoma Mexico, Inst Geol, Ciudad Univ, Coyoacan 04510, Cdmx, Mexico
|