Untitled

Abstract

La composición isotópica del azufre en sulfuros (8 34S) de las mineralizaciones tipo sedimentario-exhalativo del Ordovícico superior del valle de Arán (Pirineos Centrales) varía entre +3,5 y +15,1 %0 en los encajados en carbonatos y entre -2,7 y +5,5 %0 en los encajados en materiales detríticos. Estos valores sugieren que dichos depósitos se formaron a partir de dos fuentes de azufre distintas: una originada por reducción de sulfato de origen marino y otra por lixiviación de materiales detríticos y/o volcánicos de edad cambro-ordovícica. El metamorfismo Hercínico no ha afectado significativamente las composiciones isotópicas originales de los sulfuros y las variaciones de la 8 34S de los mismos en cada una de las dos litologías encajantes, podrían explicarse por pequeños cambios en la f0 2, temperatura o pH durante la formación de los depósitos. La composición isotópica del plomo de 6 galenas analizadas presenta las relaciones siguientes: 18,02 ::; ABSTRACTThe sulfur isotopic composition of sulfides from sedex-type deposits enclosed within Upper Ordovician rocks in the valle de Arán (Central Pyrenees) ranges from +3.5 to + 15.1 %0 in mineralizations enclosed in carbonates and from -2.7 %0 to +5.5 in mineralizations enclosed in detritic rocks. These values suggest two different sources of sulfur: a heavy source of crustal origin, probably related to the reduction of seawater sulfate, and a lighter one, resulting from leaching of underlying detritic and/or volcanic rocks of cambro-ordovician age. Hercynian metamorphism has not significantly altered the original sulfur isotopic composition of sulfides and their variation at the deposit scale can be explained by changes in T, pH or f0 2 during sulfide deposition. Lead isotope composition of 6 galena samples have the following ratios: 18.02::; 206Pbp04Pb ::; 18.08; 15.66 ::; 207PbP04Pb::; 15.70 and 38.16 s 208PbP04Pb ::; 38.29, similar to those reported by Marcoux (1987) in the Pierrefitte deposits (Central Pyrenees, France). These values are very homogeneous and suggest alead source situated within the upper crust. Calculated ages based on Cumming and Richards (1975) lead evolution model range from 422 to 452 m.a. (Upper Ordovician), which is the age of the enclosing rocks. These data confirm the hypothesis of a sedimentary-exhalative origin of the deposits.

Estructura y metamorfismo del Paleozoico del sector suroccidental del Macizo de Lys-Caillaouas (Zona Axial pirenaica, Huesca, España)

“…Por otra parte, existen mineralizaciones de Zn-Pb de tipo estratoligado (SEDEX y/o Mississippi Valley) observables en el Puerto de Benasque, al Este del Macizo de Lys-Caillaouas (Fig. 1b) (García-Sansegundo et al, 2014), y en el Domo del Garona (Cardellach et al, 1996;Pouit, 1986) (Fig. 1a), cuya edad tipo está comprendida entre el Ordovícico Superior y el Devónico Inferior.…”

From Galena to Lead: Divergent Paths in Early Metallurgy in the Western Mediterranean

“…The isotopic characterisation of geological samples from lead mines in the northeastern Iberian Peninsula had already been undertaken in research projects led by some of the authors (Nuria Rafel and Ignacio Montero). Together with the data collected from the references ( Table 3), this allows us to make a relatively comprehensive comparison between the main mining areas in the different units of the Catalan coastal mountain ranges in the provinces of Girona, Barcelona and Tarragona ( Canals and Cardellach, 1997;Montero-Ruiz, et al, 2009a;2009b;Montero-Ruiz, 2017) and the Py renees on the Spanish and French sides (Marcoux, Joubert and Lescuyer, 1991;Cardellach, Canals and Pujals, 1996;Munoz, et al, 2016). In order to test the hypothesis of a local provenance, it was necessary to incorporate new samples from mines in the province of Barcelona 3).…”