Características geológicas y metalogénicas de la mineralización de Cu-Zn-Pb-Ag de Congostrina, Sistema Central.

Las investigaciones realizadas en la zona de Congostrina han consistido en la descripción de las características morfológicas de la mineralización y su encuadre dentro del contexto de la metalogenia de la plata del Sistema Central. Asimismo se han estudiado los aspectos mineralógicos y texturales de los principales minerales de plata, estableciéndose la paragénesis y sucesión mineral del yacimiento

Estudio geoquímico de los materiales encajantes de las mineralizaciones de plata del sector oriental del Sistema Central

En este trabajo se han estudiado las características geoquímicas de los materiales que constituyen el medio encajante de las mineralizaciones de La Bodera, Congostrina y Hiendelaenclna. En las tres zonas se ha realizado un estudio lito-geoquímico, en relación con los filones, a partir del cual se ha podido determinar la distribución de los principales elementos metalogénicos y el "contenido metal" de los materiales encajantes. Por otro lado, en la zona de La Bodera. se ha realizado una prospección geoquímica de suelos, para conocer las posibles prolongaciones filonianas y el efecto de las fracturas que afectan al filón principal de la zona

Biolixiviación en columnas de sulfuros polimetálicos del yacimiento de Aznalcóllar (Faja Pirítica Ibérica).

Una alternativa al tratamiento clásico de los sulfuros polimetálicos a través del circuito flotación diferencial - fundición es el desarrollo de procesos hidrometalúrgicos eficientes que permitan la extracción selectiva de cobre, plomo y zinc. Entre las técnicas hidrometalúrgicas, la biolixiviación de menas sulfuradas complejas podría constituir un tipo de proceso limpio, de bajo costo y eficiente para extraer estos metales a partir de los materiales de mina (por lixiviación "in situ", en pila o de escombreras) o para subir selectivamente la ley (en cobre, plomo o zinc) en los concentrados de planta. Esta investigación muestra los resultados de pruebas de lixiviación en columnas, de minerales de la mina de Aznalcóllar, mediante la utilización de soluciones ácidas conteniendo una cepa (ATCC 19859) de Thiobacillus ferrooxidans. Los minerales (8,57 Kg.; pirita-calcopirita-esfalerita-galena; 0,38 por 100 Cu, 4,42 por 100 Zn, 2,11 por 100 Pb) fueron lixiviados continuamente durante 31 semanas. El tamaño de partícula elegido estuvo entre +2,0 mm. (Series DIN 1171; parte inferior de la columna) y - 2,0 + 1,2 mm. (parte superior de la columna). Pruebas de lixiviación continua adicionales fueron realizadas en embudos de decantación (3.000 mi.; 0,9 Kg. de mena; -2,0 +1,2 mm.) durante 28 semanas. Se alcanzaron altas extracciones de zinc (59,9 por 100 - 63,0 por 100) cuando el pH fue nivelado en 2,0. Cuando se pararon las pruebas el proceso de lixiviación continuaba a una tasa sostenida, por lo que puede presumirse que extracciones mayores pueden conseguirse si se emplea más tiempo en el proceso. La precipitación generalizada de minerales refractarios al proceso (e. g. sulfatos férricos) sobre las superficies de los granos de sulfuros fue impedida mediante la no utilización del medio nutriente 9 K durante la lixiviación. La precipitación de sulfatos hidratados de zinc y de hierro ferroso (gunningita, ZnS04 - 6 H20, rozenita y melanterita) tomó lugar bajo condiciones extremas de sobresaturación, y puede ser considerada como un fenómeno restringido que no impidió la extracción de metales

Silver and lead mineralogy in gossan type deposits of Sierra de Cartagena, southeast Spain

Depto. de Mineralogía y PetrologíaFac. de Ciencias GeológicasTRUEpu

a model based on fluid inclusion and geologic evidence

Depto. de Mineralogía y PetrologíaFac. de Ciencias GeológicasTRUEpu

Fluid Evolution in the Patricia Zn-Pb-Ag vein deposit (Paguanta, NE Chile): fluid inclusion assemblages and laser ablation ICP-MS evidence

The Patricia Zn-Pb-Ag ore deposit represents the first known example of economic mineralization in the northern part of the Andean late Eocene – Oligocene metallogenic belt in Chile. The hydrothermal evolution has been deduced based on detailed mineralogy, fluid inclusion petrography, microthermometry and laser ablation ICP-MS analysis. We present microthermometric data for fluid inclusion assemblages (FIAs) in co-genetic ore and gangue minerals through the different mineralization stages. In the pre-ore stage, early quartzhosted FIAs indicate high salinity values (22 to 6 wt.% NaCl) with homogenization temperatures from 270 to 205ºC. During the base metal and silver stage, a drop in temperature from 250 to 140 ºC and salinity less than 10 wt.% NaCl is related to the main ore precipitation. Primary FIAs in the post-ore stage indicate temperature up to 245ºC and low salinity (4 to 3 wt.% NaCl). The LAICP- MS analyses of fluid inclusions show that the metal content in the base metal stage is significantly higher than in the pre-ore and post-ore stages. This study documents the existence of different fluid pulses characterized by cooling and low salinity conditions favourable for the main ore deposition during the base metal and silver stage. The ore mineralogy and the associated hydrothermal alteration define the Patricia ore as an intermediate-sulfidation epithermal deposit with low-sulfidation events.This research was funded by the Spanish research project CGL-2010-17668.Peer reviewe

Geochemical Constraints on the Origin of the Ni–Cu Sulfide Ores in the Tejadillas Prospect (Cortegana Igneous Complex, SW Spain)

After the discovery of theAguablanca ore deposit (the unique Ni–Cu mine operating in SW Europe), a number of mafic-ultramafic intrusions bearing Ni–Cu magmatic sulfides have been found in the Ossa–Morena Zone of the Iberian Massif (SW Iberian Peninsula). The Tejadillas prospect is one of these intrusions, situated close to the border between the Ossa–Morena Zone and the South Portuguese Zone of the Iberian Massif. This prospect contains an average grade of 0.16 wt%Ni and 0.08 wt%Cu with peaks of 1.2 wt%Ni and 0.2 wt%Cu. It forms part of the Cortegana Igneous Complex, a group of small mafic-ultramafic igneous bodies located 65 km west of the Aguablanca deposit. In spite of good initial results, exploration work has revealed that sulfide mineralization is much less abundant than in Aguablanca. A comparative study using whole-rock geochemical data between Aguablanca aand Tejadillas shows that the Tejadillas igneous rocks present a lower degree of crustal contamination than those of Aguablanca. The low crustal contamination of the Tejadillas magmas inhibited the assimilation of significant amounts of crustal sulfur to the silicate magmas, resulting in the sparse formation of sulfides. In addition, Tejadillas sulfides are strongly depleted in PGE, with total PGE contents ranging from 14 to 81 ppb, the sum of Pd and Pt, since Os, Ir, Ru and Rh are usually below or close to the detection limit (2 ppb). High Cu/Pd ratios (9700–146,000) and depleted mantle-normalized PGE patterns suggest that the Tejadillas sulfides formed from PGE-depleted silicate magmas. Modeling has led us to establish that these sulfides segregated under R-factors between 1000 and 10,000 from a silicate melt that previously experienced 0.015% of sulfide extraction. All these results highlight the importance of contamination processes with S-rich crustal rocks and multiple episodes of sulfide segregations in the genesis of high-tenor Ni–Cu–PGE ore deposits in mafic-ultramafic intrusions of the region

Cu, Mn, and Ag mineralization in the Quebrada Marquesa Quadrangle, Chile: the Talcuna and Arqueros districts

The Quebrada Marquesa Quadrangle in Chile exhibits a series of mineralizations comprising manto-type manganese and copper deposits of Lower Creta-ceous age, and copper and silver veins of Tertiary age. The deposits are hosted by volcanic and volcaniclastic units of the Arqueros (Hauterivian-Barremian) and Quebrada Marquesa (Barremian-Albian) Formations. Three episodes of manganese mineralization (Mn1-3) are recognized within the study area. Hydrothermal activity leading to episodes 1 and 3 was of minor importance, while the second one (Mn2) gave rise to major manto-type deposits of both manganese and copper in the Talcuna mining district. Extensional faulting during Tertiary time resulted in block faulting and the unroofing of the oldest andesitic volcanics and marine sediments (Arqueros Formation). This episode was accompanied by magmatic and hydrothermal activity leading to vein formation in the Arqueros (Ag) and Talcuna (Cu) districts. The latter veins cross-cut the previous manto-type copper deposits. Ore mineralogy is similar in both styles of mineralization (manto- and vein-type) and consists mainly of chalcopyrite and bor-nite, with variable amounts of galena, tetrahedrite (vein-related), chalcocite, sphalerite, pyrite, hematite, digenite and covellite. Alteration processes at Talcuna can be divided into two categories, those related to the Lower Cretaceous manto-type episode (LK alteration: chlorite-epidote-calcite-albite, prehnite, zeolite), and those associated with the locally mineralized normal faults of Tertiary age (Tt alteration: chlorite-calcite, sericite). The Arqueros silver veins display an ore mineralogy consisting of arquerite, argentite, native silver, polybasite, cerargyrite and pyrargyrite-proustite; associated altera-tion includes strong chloritization of the country rock. The manto-type deposits formed from fluids of salinity between 11 and 19 wt.% NaCl equivalent and temperatures between 120 and 205 °C. Mineralizing fluids during the vein-type stage circulated at lower temperatures, between 70 and 170 °C, with salinity values in a wide range from 3 to 27 wt.% NaCl equivalent. This distribution of salinities is interpreted as the result of the complex interplay of two diferent processes: boiling and fluid mixing; the former is considered to control the major mineralogical, textural and fluid inclusion features of the vein-type deposits. We suggest that the Lower Cretaceous mineralization (manto-type stage) developed in response to widespread hydrothermal activity (geothermal field-type) involving basinal brines