An Alternative Scenario on the Origin of Ultra-High Pressure (UHP) and Super-Reduced (SuR) Minerals in Ophiolitic Chromitites: A Case Study from the Mercedita Deposit (Eastern Cuba)

The origin of the assemblage of ultra-high pressure (UHP), super-reduced (SuR) and several crustally derived phases in ophiolitic chromitites is still hotly debated. In this paper, we report, for the first time, this assemblage of phases in ophiolitic chromitites of the Caribbean. We studied the Mercedita chromitite deposit in the eastern Cuban ophiolitic complexes. The mineral phases were characterized using microRaman spectroscopy, energy-dispersive spectroscopy with a scanning electron microscope (SEM-EDS), X-ray microdiffraction and electron microprobe analyses. Mineral concentrates were prepared using hydroseparation techniques. We have identified oriented clinopyroxene lamellae in chromite, oriented rutile lamellae in chromite, moissanite hosted in the altered matrix of the chromitite, graphite-like amorphous carbon, corundum and SiO2 hosted in healed fractures in chromite grains, and native Cu and Fe–Mn alloy recovered in heavy-mineral concentrates obtained by hydroseparation. This assemblage may correspond to UHP-SuR conditions, implying recycling of chromitite in the mantle or formation of the chromite grains at deep mantle depths, followed by emplacement at a shallow level in the mantle. However, the chromitite bodies contain gabbro sills oriented parallel to the elongation of the chromitite lenses, and these show no evidence of HP/UHP metamorphism. Therefore, the identified “exotic” phases may not be indicative of UHP. They formed independently as oriented clinopyroxene lamellae in chromite during cooling (clinopyroxene and rutile), in super-reduced microenvironments during the serpentinization processes, and by transference of subducted crustal material to the mantle wedge via cold plumes.This research was financially supported by the Spanish Project CGL2015-65824 granted by the Spanish “Ministerio de Economía y Competitividad” to J.A.P., the Ramón y Cajal Fellowship RYC-2015-17596 to J.M.G.-J. and a FPU Ph.D grant to N.P.-S. by the Ministerio de Educación of the Spanish Government

La primera explotació de coure a Catalunya. Dades arqueològiques i arqueomètriques de la Mina de la Turquesa (Cornudella de Montsant, Priorat)

Aquest treball exposa l’estat de la recerca a la mina de coure de la Turquesa (Cornudella de Montsant Priorat) l’explotació prehistòrica que vam identificar l’any 2011. Es van realitzar tres campanyes d’excavació que han permès recuperar i estudiar 117 artefactes lítics miners i s’han analitzat mostres de minerals i roques del jaciment amb diverses tècniques (isòtops de plom fluorescència de raigs X i difracció de raigs X). Els resultats obtinguts permeten detectar coincidències amb altres elements metal·lúrgics de la zona i datar la primera explotació de la mina durant el III mil·lenni cal ANE

La primera explotació de coure a Catalunya. Dades arqueològiques i arqueomètriques de la Mina de la Turquesa (Cornudella de Montsant, Priorat)

Altres ajuts: HUM2004-04861-C03 ; HUM2007-65725-C0

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

Les col·leccions de mineralogia de la UB. Una eina d'aprenentatge i de participació dels estudiants

Les col·leccions de Mineralogia de la Universitat de Barcelona poden ser de litoteca (emprades en l'ensenyament presencial i no presencial) i sistemàtica (usades com a material de referència de recerca). Comprenen mostres de mà, làmines primes i probetes. Les col leccions de referència son controlades per estudiants, els quals comproven la identitat del mineral i en fan la catalogació. Així s'introdueix els estudiants en les tècniques de caracterització i en les tècniques de musealització

Extracció minera a la Selva del Camp

Treball de recerca realitzat per un alumne d’ensenyament secundari i guardonat amb un Premi CIRIT per fomentar l'esperit científic del Jovent l’any 2008. L’objectiu d’aquest treball és localitzar i descriure algunes de les mines que s’havien explotat al municipi de la Selva del Camp -comarca del Baix Camp, Tarragona - durant el segle XIX i inici del XX. També es pretén estudiar els minerals extrets en aquestes mines i recollir-ne mostres. Finalment, s’investiga la situació de les mines en el context geològic general i quin és l’origen dels filons explotats. La metodologia seguida ha tingut diverses fases. Primerament, s’ha obtingut informació bibliogràfica i cartogràfica sobre la geologia de la Selva del Camp. En segon lloc, s’ha obtingut informació sobre les mines que s’explotaven al terme a l’Arxiu Municipal i s’han localitzat les mines en un mapa. En tercer lloc, s’ha recollit informació oral sobre la ubicació i l’explotació de les mines amb entrevistes a gent gran del poble. Posteriorment s’ha realitzat un treball al camp per buscar les mines. Un vegada trobades s’han descrit confeccionant esquemes del seu recorregut, localitzant les escombreres i recollint-ne mostres. Finalment s’han estudiat les mostres al laboratori i s’ha elaborat una col•lecció. Els resultats de la recerca mostren que les mines explotaven filons metàl•lics formats per precipitació de sulfurs i òxids dins de les llicorelles del carbonífer-permià. Els minerals explotats eren principalment galena, mena del plom i pirolusita, d’on s’obtenia manganès. Es recomana crear algun itinerari per donar difusió a aquest patrimoni

Una explotación de cobre prehistórica: la mina "de la Turquesa" (o del Mas de les Morenes), Cornudella de Montsant, el Priorat, Tarragona

Con permiso de la revistaIn this paper we synthetically present the results of the studies carried out at La Turquesa prehistoric copper mine, preceded by an introduction to the oldest European mining, that has the role of contextualizing the mine. The results of the archaeological excavations carried out and the research on the structure and mineralogy of the mine (where there is not turquoise) within the framework of its local geological environment are presented. The analysis of the more than one hundred stone mining tools found in the course of the excavations shows their un-doubtedly prehistoric nature, as well as their main characteristics from the point of view of the raw materials used and their manufacturing processes. The archaeometallurgical study has focused on two types of characterisation of the ores from the mine: elemental analyses (pXRF and X-ray diffraction) and characterisation by lead isotope analysis to define the isotopic field, allowing comparative studies to be made of the archaeological finds and iden-tification of possible prehistoric objects manufactured using this copper ore. This chaeometallurgical research has shown the affinities between some ores and objects and indicates the use of the copper of La Turquesa mine in the elaboration of some of them. The results of a pioneering research implemented with the aim of verifying the existence of mining operations using the fire-setting technique are also presented. All this allows to establish the period of exploitation of the mine between the Chalcolithic and the Middle Bronze Age (2,800 to 1,300 BC), helps to know prehistoric mining in Catalonia, the character of the communities that occupied the territory and its relationship with mining and exchange and shows the importance of protecting and investigating the prehistoric mining heritage.Peer reviewe

Una explotació de coure prehistòrica : la mina 'de la Turquesa' (o del Mas de les Moreres), Cornudella de Montsant, el Priorat, Tarragona

In this paper we synthetically present the results of the studies carried out at La Turquesa prehistoric copper mine, preceded by an introduction to the oldest European mining, that has the role of contextualizing the mine. The results of the archaeological excavations carried out and the research on the structure and mineralogy of the mine (where there is not turquoise) within the framework of its local geological environment are presented. The analysis of the more than one hundred stone mining tools found in the course of the excavations shows their undoubtedly prehistoric nature, as well as their main characteristics from the point of view of the raw materials used and their manufacturing processes. The archaeometallurgical study has focused on two types of characterisation of the ores from the mine: elemental analyses (pXRF and X-ray diffraction) and characterisation by lead isotope analysis to define the isotopic field, allowing comparative studies to be made of the archaeological finds and identification of possible prehistoric objects manufactured using this copper ore. This archaeometallurgical research has shown the affinities between some ores and objects and indicates the use of the copper of La Turquesa mine in the elaboration of some of them. The results of a pioneering research implemented with the aim of verifying the existence of mining operations using the fire-setting technique are also presented. All this allows to establish the period of exploitation of the mine between the Chalcolithic and the Middle Bronze Age (2,800 to 1,300 BC), helps to know prehistoric mining in Catalonia, the character of the communities that occupied the territory and its relationship with mining and exchange and shows the importance of protecting and investigating the prehistoric mining heritage