Iron sulphides at the epithermal gold-copper deposit of Palai-Islica (Almería, SE of Spain)

El artículo original ha sido publicado por la Mineralogical Society disponible en: http://www.minersoc.org/pages/e_journals/minmag.htmlAu-Cu mineralisation at Palai-Islica occurs as disseminations in massive silicification and, more abundantly, in sulphide-bearing quartz veins. The major ore minerals in the deposit are pyrite ± chalcopyrite, sphalerite and galena and there are a great variety of accessory minerals, including Au-Ag alloys and native gold. Pyrite, the most abundant sulphide, is closely associated with gold. Seven different types of pyrite have been distinguished with a variable concentration of different trace elements. Among them only free of trace elements (type IV) is related to Au-Ag alloys. Pyrites associated with these Au-Ag alloys have a cubic and pentagonal dodecahedral habits whereas those with only the pentagonal dodecahedral habit are from barren zones. In addition, there is no significant invisible gold in pyrite, but there is relatively high Ag in collomorphic pyrite (up to 0.20 wt%) or type III pyrite (up to 1.47 wt%). As is the most abundant trace element in pyrite (up to 6.11 wt%), present as a metastable solid solution or as a non-stoichiometric element. Some kind of marcasite related with gold levels also have considerable amounts of trace elements (As, up to 1.15 wt%, Sb up to 0.40 wt%)Departamento de Mineralogía y Petrología. Grupo de Investigación de la Junta de Andalucía RNM-0131. Proyectos PB-97-1211 y BTE2001-330

Petrogénesis del plutón monzogranítico peralumínico de Santa Eufemia (Batolito de los Pedroches, Córdoba)

18 páginas, 10 figuras, 2 tablas.[ES] El plutón de Santa Eufemia forma parte del batolito de Los Pedroches, situado en el extremo sudoccidental de la Zona Centro-Ibérica del Macizo Hercínico español. Este batolito de carácter epizonal y postcinemático está constituido por tres tipos plutónicos mayoritarios: granodioritas biotíticas± anfíbol, monzogranitos biotítico-cordieríticos porfídicos y leucogranitos cordieríticos de tendencia aplítica. El plutón de Santa Eufemia está formado por monzogranitos porfídicos y leucogranitos, ambos con cordierita. Los monzogranitos presentan distintos tipos de enclaves, siendo los más comunes los enclaves monzograníticos porfídicos de grano fino y los enclaves con biotita-plagioclasa-cordierita. El análisis petrográfico, estructural y geoquímico de elementos mayores y trazas parece descartar una relación genética entre las granodioritas biotíticas±anfíbol y los monzogranitos, y permite considerar al plutón como el resultado de una historia evolutiva compleja de un magma monzogranítico, producto de la fusión parcial de una fuente metasedimentaria, cuya heterogeneidad composicional proviene de la mezcla de un fundido no mínimo y material restítico reequilibrado (restitas secundarias) durante la evolución ortomagmática del mismo. El producto final de esta evolución es la segregación de un fundido residual saturado en fluidos en el nivel de intrusión actual, emplazándose masas y diques de leucogranitos y exsolviéndose una fase fluida en condiciones supercríticas, relacionada con la recristalización tardimagmática de algunas fases minerales (moscovita, albita, cuarzo, turmalina, topacio), la removilización de ciertos elementos incompatibles (Rb, Cs, Li, Be, Sn, Nb) por interacciones roca-fluido y la formación de venas periplutónicas de wolframita-arsenopirita-cuarzo.[EN] The Santa Eufemia pluton is part of the composite magmatic assoclatlon of Los Pedroches batholith, located in the southern branch of the Central Iberian Zone of the Hercynian orogenic belt of Spain. This high-Ievel postkynematic batholith consists of three main types of plutonic rocks: boitite±amphibole granodiorites, biotite-cordierite porphiritic monzogranites and cordierite leucogranites. The Santa Eufemia pluton consists of biotite-cordierite monzogranites, and in a lesser extent of cordierite leucogranites. Scarce enclaves of different type are found in the monzogranites, biotiteplagioclase- cordierite and fine grained porphiritic monzogranite enclaves being the most common. The petrographic, structural and geochemical (major and trace elements) data suggests a complex evolutionary history of a metasedimentary-source monzogranitic magma with no genetical relationships with more basic magmas such as the one which is now represented by the granodiorite facies of the batholith. Non-minimum melt and reequilibrated source material (secondary restites) mixing during the ortomagmatic evolution of the magma accounts for the compositional heterogenities of the monzogranites. The ultimate product of this evolution is the segregation of a fluid-saturated residual liquid in the final level of intrusion of the magma, leading to the emplacement of leucogranite masses and dikes and the exsolution of a supercritical fluid phase related with the late magmatic recrystallization of sorne mineral phases (muscovite, albite, quartz, tourmaline, topaz), the geochemical removilization of sorne incompatible trace elements (Rb, Cs, Li, Be, Sn, Nb) due to fluid-rock interactions and the formation of periplutonic wolframite-arsenopyritequartz mineralizations.Peer reviewe