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

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

The BCN-SGA student chapter: a tool for insertion to research and laboral world in metallogeny

The activity of the BCN-SGA Student Chapter is evaluated. Establishedin 2012 it has grown up to 69 members, organizing 2 international workshops, 8seminars, numerous visits to museums, activities stimulating the use of English in socialevents and microresearch projects. The results of these microprojects are 15 presentations in scientific congresses. These activities enhance teamwork skills anddemonstrate that students can develop high quality research during the whole of theirformation.Peer ReviewedPostprint (published version

The BCN-SGA student chapter: a tool for insertion to research and laboral world in metallogeny

The activity of the BCN-SGA Student Chapter is evaluated. Establishedin 2012 it has grown up to 69 members, organizing 2 international workshops, 8seminars, numerous visits to museums, activities stimulating the use of English in socialevents and microresearch projects. The results of these microprojects are 15presentations in scientific congresses. These activities enhance tea

Estudio Geológico y Metalogenético del Basamento Precámbrico del Sahara Occidental

[spa] En el Sáhara Occidental hay dos unidades principales: la cobertera sedimentaria del Fanerozoico y un basamento cristalino que forma parte del cratón del África Occidental, constituido desde el Paleoarcaico al Paleoproterozoico. A su vez, en el basamento se ha definido una serie de dominios o terranes, delimitados por fallas regionales, que responden a microcontinentes que colisionaron principalmente durante la orogenia Birimiense y la Hercínica. Los primeros estadios de granitización parecen producirse entre el Paleoproterozoico y el Mesoproterozoico dependiendo del dominio, pero el primer gran episodio de plutonismo de tipo TTG generalizado es en la orogenia Leoniana (hacia 3 Ga). Se forman importantes depósitos de BIF en cuencas de “greenstone belts”. El ciclo Liberiense comienza con diques y “sills” ultrabásicos asociados a una pluma mantélica, que evoluciona a una LIP constituida por enjambres de diques de diabasa; en el resto de sectores se produce la individualización de los microcontinentes. El final del ciclo implica la colisión parcial de algunos de estos dominios y procesos de subducción que generan magmatismo calcoalcalino. El proceso de rift en el límite Arcaico- Proterozoico produce magmatismo alcalino saturado y subsaturado, con indicios de elementos raros. Localmente se individualizan cuencas sedimentarias submarinas en las que se forman depósitos importantes de BIF. Durante el Paleoproterozoico se produce la convergencia de la mayoría de las microplacas; en las zonas de suprasubducción se produce un magmatismo calcoalcalino; con el cierre de los océanos y la colisión continental se forman complejos ofiolíticos, a veces con mineralizaciones de Cr-PGE y depósitos de oro orogénico. Esta orogenia produce la cratonización de la mayor parte de los dominios. Los granitos alcalinos asociados al rift posterior son en cambio estériles. El magmatismo calcoalcalino asociado a la orogenia Kibariense en el margen occidental del crató n no par ece haber gener ado depósitos, pero los granitos alcalinos que cierran el ciclo contienen concentraciones muy altas de REE y Nb. La orogenia Panafricana determina la aparición de magmatismo calcoalcalino en el borde occidental del cratón, así como una nueva colisión con el dominio oriental de los Mauritánides, que se cratoniza. El proceso de rifting subsecuente genera rocas alcalinas saturadas y subsaturadas estériles. Los márgenes continentales así formados facilitan la sedimentación de series de plataforma del Paleozoico, en los que se encuentran mineralizaciones de Fe oolítico en el Devónico inferior. Durante la orogenia hercínica se produce la colisión continental de todos estos dominios y Laurussia, formándose el supercontinente de Pangea. En este contexto los cabalgamientos asociados pueden formar mineralizaciones de oro orogénico, y pueden darse mineralizaciones de Cr podiforme (PGE) en ofiolitas. Finalmente, la apertura del Atlántico N desde el Triásico superior-Jurásico produce el desarrollo de carbonatitas en el dominio más occidental de los Mauritánides, asimismo con mineralización de elementos raros. Los márgenes continentales así formados permiten el desarrollo de series de plataforma ricas en yacimientos de fosfatos y con potencial para petróleo. En el curso de este t rabajo se han descubierto varios depósitos minerales, pr incipalmente en el basamento del Precámbrico. Los depósitos de menas metálicas más interesantes son los siguientes: a) Los depósitos ortomagmáticos de Cr- PGE -Ti-V en el complejo estratiforme de Bir Malhat, con continuidades de decenas de km b) Los depósitos de Cr-PGE en cromititas podiformes en contextos oceánicos del Proterozoico de los Mauritánides. c) Los depósitos de Au-(PGE) orogénico asociados a zonas de cizalla, tanto en forma de listwänitas-birbiritas, sistemas filonianos o mineralizaciones estratoligadas asociadas a los mismos, correspondiendo a cizallas formadas en épocas panafricanas (dominios de Tifariti-Bir Lehlu-Ain ben Tili y de Sfariat) o hercínicas (Mauritánides). d) Los depósitos de BIF en series submarinas; si bien estos depósitos se encuentran en todos los dominios, los más interesantes por su continuidad y leyes se encuentran en las zonas de Sfariat y Miyec-Ijil. e) depósitos de Nb-Ta-LREE-U-Fe-V- P-Mo en carbonatitas, importantes tanto en las de edades del Proterozoico como en las del Cretácico. f) depósitos de Nb-Ta-F-HREE-U-Th en rocas alcalinas saturadas o subsaturadas, preferentmente en las enriquecidas en F. g) depósitos de Fe oolítico en las series de plataforma del Devónico inferior, de grandes reservas. h) depósitos de fosforitas y petróleo asociados a la cuenca sedimentaria de El Aaiún. i) Depósitos de U-(REE??) de edad Cuaternario , asociados a calcretas y ferricretas.[eng] Two main geological units are distinguished in Western Sahara: a Phanerozoic sedimentary cover and a cryst a lline basement o f Paleoarchean to Paleoproterozoic age. This basement is a part of the Reguibat ridge, in the Western Africa craton. An ensemble of domains (or terranes) are distinguished in the basement. These domains are limited by regional fauls and correspond to old microcontinents collisioned mainly during the Birimian and Hercynian orogenies. Earlier granitization stages were produced in the Paleoarchean and the Mesoarchean depending on the domain, but the first generalized episode of TTG plutonism occurs in the Leonian orogeny ( circa 3 Ga). Important BIF deposits formed in greenstone belt basins. The Liberian cycle start with the intrusion of ultrabasic sills and dykes, associated with a mantle plume. This scenario evolved to a LIP made up by a dense network of diabase dykes; the individualization of the microcontinents took place in the rest of the area. Convergence of some of these microplates pr oduced subduction and a calc-alkaline magnatism and finally a collision between some of these domains at the end of this cycle. Rifting at the limit Archean-Proterozoic generated saturated and subsaturated alkaline magmatism. Showings of rare- element mineralization occur in these rocks. Submarine sedimentary basins are locally developed, and contain important BIF deposits. Most of the microplates converged during the Paleoproterozoic; calc-alkaline magmatism do occur in the suprasubduction zones; closing of the oceans and subsequent continental collision is associated with development of Cr- (PGE) bearing ophiolitic suites. Regional shear zones are associated with orogeenic gold deposits. This Birimain orogen produced the cratonization of most of the domains.. Alkaline granites intruded in a rft stage at the end of the orogeny, but they are barren. Calc-alkaline magmatism is also present during the Kibarian and Panafrican orogeny at the west border of the WAC, and is not mineralized; however, the alkaline granites of the rifting closing the Kibaran orogeny contain high concentrations of Nb and REE; those at the end of the end of the Panafrican are devoid of mineralization.. The continental margins of the craton allowed the sedimentation of thick platform series during the Paleozoic. The lower Devonian series hosts oolitic iron deposits. The general collision of all these domains and Laurussia during the Hercynian orogeny produced the Pangea supercontinent. In this context, the thrusts can carry orogenic gold deposits, and podiform Cr-(PGE) deposits outcrop in ophiolites. Finally, the opening of the North Atlantic since the Upper Triassic-Jurassic produced carbonatites at the western end of the WAC ; these carbonatites are enriched in rare elements. The continental margins formed in this epoch allowed the sedimentation of platform series thaht contain phospate deposits and have potential to contain oil. Western Sahara has a large potential for ore deposits, and some of them have been discovered during the development of this memory; most of them are hosted in the Precambrian materials: a) Stratiform Cr-PGE -Ti-V deposits associated with the Bir Malhat complex, and their continuity overpass 20 km. b) Podiform Cr-PGE chromitite deposits were produced in the Proterozoic of the Mauritanids. c) Orogenic gold deposits (Au-(PGE) are associated with the regional shear zones. There are several styles of mineralization: listwänites- birbirites, vein systems, or stratabound mineralizations replacing favourable host rocks in the vicinity of shear zones formed during the Birimian orogeny (Tifariti-Bir Lehlu-Ain ben Tili and Sfariat domains) o the Hercynian (Mauritanids). d) BIF deposits in submarine series. These deposits occur in most of the domains, but the Sfariat and Miyec-Ijil domains contain most of the largest reserves. e) Deposits of rare elements as Nb-Ta- LREE-U-Fe-V-P-Mo occur in the Proterozoic and Cretaceous carbonatites. f) Deposits of Nb-Ta-F-HREE-U-Th are found in undersaturated or saturated alkaline rocks, mainly in those enriched in F. g) Oolitic iron deposits have large reserves in the platform series of the Lower Devonian. h) World-class stratiform phosphorite deposits occur in the Paleogene El Aaiún sedimentary basin, which has also potential for oil deposits. i) Calcrete and ferricrete U-(REE??) deposits of Quaternary age

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

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 podshaped 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

The Neolithic variscite mines of Gavà, Catalonia: criteria for mineral exploration and exploitation in the Prehistory

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.El Complejo Minero Neolítico de Gavà (CMNG) ubicado en Cataluña tuvo como objeto la explotación de la variscita verde utilizada para la elaboración de adornos y joyería. Los trabajos arqueológicos en más de 100 minas indican que la minera en este complejo se llevó a cabo ~5800 años antes del presente. CMNG constituye (A) uno de los primeros ejemplos conocidos de minería subterránea en Europa, (B) posiblemente el ejemplo más antiguo de minería a gran escala para uso ornamental y (C) el ejemplo más antiguo de aplicación de conceptos geológicos y mineros complejos. En el CMNG, la variscita se encuentra en dos estilos distintos: (1) reemplazamientos de láminas delgadas de fluorapatito intercaladas con pizarras negras ricas en minerales orgánicos de edad silúrica y (2) vetillas que cortan transversalmente estos materiales. El conjunto está cubierto discordantemente y localmente por caliches del Cuaternario. La variscita se formó como resultado de procesos supergénicos cuaternarios que oxidaron la pirita produciendo soluciones ácidas y oxidadas. Los fluidos resultantes movilizaron fosfato de apatito y lixiviaron Al y materia orgánica de las pizarras, lo cual condujo a la precipitación de los fosfatos ricos en Al como rellenos de venas y de reemplazamientos estratoligados de apatito. La formación de variscita se restringió a la extensión del frente de oxidación, y la variscita de ambos estilos de mineralización varia de color verde amarillento, en superficie, hasta verde profundo, en profundidad. El área de estudio contiene dos campos mineros: Can Tintorer y Can Badosa-Les Ferreres. La presencia de abundantes vetas subverticales de variscita en Can Tintorer permitió un complejo desarrollo de galerías en diferentes niveles de explotación comunicadas por pozos y rampas, logrando 15 metros de profundidad. La explotación empleada por los mineros neolíticos fue mediante realce ascendente y descendente; también usaron pilares y rellenos de explotaciones más antiguas para evitar el colapso de la mina. Estas minas fueron abiertas en muchos casos por pozos que fueron cavados directamente en duros caliches cuaternarios, favoreciendo la estabilidad de las galerías y revelando que los mineros comprendían la continuidad de la mineralización por debajo de la cubierta de caliches. El mapeo geológico revela que las explotaciones en el área de Can Badosa-Les Ferreres son simples, mostrando una entrada única a galerías simples o rampas que alcanzan menos de 5 m de profundidad y excavadas directamente en afloramientos de fosfatos. En contraste, las minas en el área de Can Tintorer tienen varias entradas y consisten en pozos verticales a través de una cubierta cuaternaria, presentando una intrincada geometría con muchas galerías grandes y comunicadas a diferentes profundidades con un sistema de cámaras y pilares. Aunque el desarrollo de ambas áreas mineras fue esencialmente contemporáneo, Can Badosa-Les Ferreres puede considerarse como un área de exploración. Además, la minería se llevó a cabo en minerales adyacentes a la variscita, no directamente en las venas de variscita, lo cual indica que los mineros usaron de forma efectiva un caudal de conocimiento geológico que se adquirió previamente a las complejas operaciones en las minas de Can Tintorer

The Neolithic variscite mines of Gavà, Catalonia (NE Iberian Peninsula): criteria for mineral exploration and exploitation in the Prehistory

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 stratabound 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 un-derstood 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

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

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

The BCN-SGA student chapter: a tool for insertion to research and laboral world in metallogeny

The activity of the BCN-SGA Student Chapter is evaluated. Establishedin 2012 it has grown up to 69 members, organizing 2 international workshops, 8seminars, numerous visits to museums, activities stimulating the use of English in socialevents and microresearch projects. The results of these microprojects are 15 presentations in scientific congresses. These activities enhance teamwork skills anddemonstrate that students can develop high quality research during the whole of theirformation.Peer Reviewe

The BCN-SGA student chapter: a tool for insertion to research and laboral world in metallogeny

The activity of the BCN-SGA Student Chapter is evaluated. Establishedin 2012 it has grown up to 69 members, organizing 2 international workshops, 8seminars, numerous visits to museums, activities stimulating the use of English in socialevents and microresearch projects. The results of these microprojects are 15 presentations in scientific congresses. These activities enhance teamwork skills anddemonstrate that students can develop high quality research during the whole of theirformation.Peer Reviewe