Lithogeochemical exploration in a Hercynian Tin-Bearing Batholith in the Northwest of the Iberian Peninsula

[EN] This workpresents the results of amulti-element lithogeochemical study of the Hercynian Batholith of Ricobayo (Zamora, NW Spain). Severa1 tin deposits are genetically associated with this batholith. Probability plots have been used to prepare contour maps of SiO,, Fe,O,, Na20, K20, CaO, MgO, Rb, Sr and Zr. The geochemical patterns of Ca0 reflects tin-bearing areas and may therefore indicate tin-target areas associated with this type of granite.[ES] El Batolito hercinico de Ricobayo, al que se encuentran asociadas genéticamente mineralizaciones de estaño, ha sido objeto de un estudio litogeoquimico con el fin de comprobar la efectividad de tales metodos en la exploración de áreas con mineralizaciones de estaño. Tomando como referencia las rupturas de pendiente que muestran las distribuciones de SiO,, Fe20,, Na20, K20, CaO, MgO, Rb, Sr y Zr en 10s correspondientes gráficos probabilisticos, se ha procedido a determinar 10s mapas de isocontenidos de tales elementos en el Batolito de Ricobayo. La distribución de Ca0 es la única que refleja las áreas con mineralizaciones de estaño y puede utilizarse como indicadora de las áreas de potencial interés asociadas a este tipo de granitos."Peer reviewe

A contribution to regional tin exploration in the Iberian Massif

11 páginas, 5 figuras, 1 tabla.The aim of this study was to develop a method for regional tin exploration applicable to the geological, physiographic and climatic characteristics of the western Iberian Peninsula. During the spring of 1985, 299 panned concentrates and water samples were collected from the drainage system of an area of 150 km2 in the east of the province of Zamora (Spain). One split of the panned concentrates was analyzed for Sn, W, As, Ph, Zn, Cu and Ba, while the heavy-mineral composition was determined on the other. Fluorine, Na and K were analyzed in the water samples. Log-probability plots were used to determine regional background and anomaly class levels. The pattern of Sn content of the panned concentrates and of F of the stream water samples clearly define anomalous zones. The mineralogical study of the concentrates revealed that cassiterite produces geochemical Sn anomalies. There are two types of cassiterite: one brown in colour and the other black and accompanied by wolframite. The first type is related to cassiterite disseminations in aplites and cassiterite-quartz veins and the second type to cassiterite-quartz veins and cassiterite disseminations in leucogranites and aplopegmatites. Thus, the results obtained suggest that Sn and F can be used to find new mineralizations.Peer reviewe

Practical determination of anomalies thresholds in drainage net prospection.

[Resumen] El propósito del presente trabajo es dar a conocer un método sencillo y práctico para la determinación correcta de los umbrales de anomalía en la prospección geoquímica y mineralógica cuantitativa sobre redes de drenaje (concentrados de sedimento, sedimentos yaguas). El método se basa en el estudio de la distribución de las variables consideradas (elementos químicos o minerales) sobre gráficos log-probavilísticos.[Abstract] The aim of the present paper is to offer a simple and practical method for the correct determination of anomaly thresholds in the geochemical and quantitative mineralogical exploration of drainage systems (sediment concentrates, sediments and waters). The method is based on the study of the distribution shown by the variables considered (chemical elements or minerals) on log-probability graphs

Contribución al conocimiento de los granitos especializados de dos micas centro-ibéricos: estudio del Batolito de Viliar del Ciervo (Salamanca)

[Resumen] Los granitos de la zona indicada presentan muchos rasgos comunes con los del área centro-occidental ibérica, mineralógicos, petrográfcos, geoqu!micos, etc. Se ha comprobado el carácter zonado del plutón, diferenciándose varias facies con ayuda de criterios de campo y estudio en laboratorio de nas de 60 muestras del granito y sus enclaves. Se pone de manifiesto la influencia de elementos como el B en la cristalizaci6n granítica. Se discute el significado de algunos minerales en la paragénesis y los posibles orígenes de las facies gran!ticas: mezcla de magras diferentes, contaminación por el encajante, proporciones distintas de magma y restitas, intrusiones diferentes originadas por secuencias de fusión parcial, fusión cortical de materiales anfiboliticos, cristalizaci6n fraccionada y difusión termogravitacional. los enclaves microgran!ticos se interpretan como porciones de magma de carácter más máfico. La asociación como de este tipo de granitos con indicios y depósitos metalíferos (Sn, W, Li, P, etc.) deriva de sus abundantes manifestaciones deutéricas, tardías.[Abstract] The granites of this zone show many mineralogical, petrographic, geochemical, etc. features like to those of the iberico,estern-central area. The zoned character of the pluton had been shown and several faciee are di:rferentiated according to terrain and laboratory criteria; more than 60 sampIes of granites and their enclaves were analysed. It is shown the influence of elements, as the B, on the granitic crystaIlization. The significance of some minerals and the possible origine of the granitic facies are discussed: mixing of different magma., wall-rook contamination, restite unmixing, intrusions by sequential partíal meIting, crustal melting of amphibolitic materials, fractional crystallization and thermogravitational diffusion. The Inícrogranitoid enclaves are interpreted as rraterials from a more mfic magna, and the frequent showings and mineral deposits (Sn, W, 1i, P, etc.) associated with these pIutons are derived from the lattest phenomena (deuteric processe

Contribución al conocimiento de los granitos especializados de dos micas centro-ibéricos. Estructura del batolito de Villar de Ciervo (Salamanca).

Universidad de la Coruña. Area de Xeoloxía e Minerí

Prospección estratégica de la cuenca hidrográfica superior del río Garona (Vall d'Arán, Lleida)

Fernández Turiel J.L., Viladevall M., Gimeno D., Durán M.E., Prospección estratégica de la cuenca hidrográfica superior del río Garona (Vall d'Arán, Lleida). Revista d'Investig. Geol., 1986, 42/43: 121-130.[EN] The present work was conducted as part of a pilot experiment of a research project on the mineral resources of the NE the Iberian Peninsula. lts aim is to test a method for regional exploration in alpine zones. Accordingly, the hydrographic basin of t[he River Garona in the Vall d'Aran (Lleida, Spain) in the Pyrenean axial zone was chosen since the occurrences and ancient mining activity there are abundant and it is typical of the kind of zone to be studied. Two hundred and sixty-eight stream sediments and 64 panned concentrates were obtained from an area of 550 km2 of the hydrographic network. ln Ihe below-80 mesh fraction (ASTM) of the sediments Ihe contents in Pb, Zn, Cu, Fe, Mn, Ni, Ca, Cd, Ag, Mo, and V were analyzed whereas the concentrates were employed for the mineralogical determination and count of the grains of scheelite present. The statistical treatment of geochemical information (log-probabilistic graphs, bivariate analysis, principal component analysis, discriminant analysis and multiple linear regression), together with the mapping of the different parameters, has allowed us to determine the anomalies of the study area.[ES] Este trabajo se ha realizado como parte de la experiencia piloto de un proyecto de investigación de los recursos minerales del NE de la Península Ibérica. Su propósito es el de probar una metodología de prospección estratégica en zonas alpinas, por lo que se eligió para este fin la cuenca hidrográfica del río Garona en la Vall d'Aran (Lleida) en la zona axial pirenaica, pues en ella son numerosos los indicios y labores mineras antiguas y su orografía es característica del tipo de zona a estudiar. Sobre la red hidrográfica de una área de 550 km2 se recogieron 268 sedimentos de arroyo y 64 concentrados a la batea. En la fracción inferior a 80 mesh (ASTM) de los sedimentos, se analizaron los contenidos en Pb, Zn, Cu, Fe, Mn, Ni, Ca, Cd, Ag, Mo y V; mientras que los concentrados se usaron para la determinación mineralógica y contaje de los granos de scheelita presentes. El tratamiento estadístico de la información geoquímica (gráficos log-probabilísticos, análisis bivariante, análisis de componentes principales, análisis discriminante y regresión lineal múltiple), junto con la cartografía de los diferentes parámetros, ha permitido determinar correctamente las anomalías existentes en el área estudiada.Universitat de BarcelonaPeer reviewe

Trace elements in high-S subbituminous coals from the teruel Mining District, northeast Spain

15 páginas, 7 figuras, 5 tablas.The elemental composition of high temperature ash (750°C) and forms of S were studied in 25 coal seams from the Escucha Formation (Middle Albian) in the Teruel Mining District, northeast Spain. The principal analytical method was ICP-MS, but ICP-ES was also used in the determination of some trace elements. The analytical data show wide ranges of trace element cotnents among the coal seams studied, even in the vertical profile of a single coal seam. These wide ranges of the trace element concentrations are attributed to both syngenetic and epigenetic processes. When a comparison was made between the average trace element contents of the Teruel Mining District coals, and those of the average content in worldwide coals, the Teruel coals show slightly higher concentrations of Be and U, and lower concentrations of Ba, Cd, Mn, Pb, Sr and Zr. Further, three main groups of trace elements were differentiated on the basis of the inorganic/organic association: (1) trace elements with inorganic affinity; Ba, Ce, Co, Cr, La, Mn, Ni, Rb and Zr. Between these, Ba, Ce, Cr and Rb show a well defined correlation with the clay mineral content, and Co and Ni with pyritic-S content; (2) trace elements with an intermediate (mixed) affinity; As, Cd, Cu, Dy, Er, Eu, Gd, Ge, Ho, Lu, Mo, Nd, Pb, Pr, Sb, Sm, Sr, Tb, Th, Tm, U, Yb and Zn. In this group, As, Cd, Cu, Ge, Mo, Th, U and Zn show a weak trend associated with the mineral matter and Sr with the organic matter; and (3) Be shows an organic affinity. The high mineral matter content (21.3% HTA) of the Teruel coals may account for the great number of elements with inorganic affinity. This classification represents a general trend, but the results show that the affinities of some trace elements (e.g. As, Sb and Zn) may vary from one coal seam to another in the Teruel Mining District.This work has been supported by Research Project PB 87-0463-C02-01 of the Spanish Ministry of Education and Science and by a Research Project of the Instituto de Estudios Turolenses.Peer reviewe

Comparison between analytical and mineralometric methods in regional scheelite exploration

7 páginas, 3 figuras, 1 tabla.The scheelite dispersion was studied in a drainage system over an area of 150 km2 with stratabound mineralization of scheelite in a Pre-Ordovician volcano-sedimentary Series in the Hercynian Iberian Massif (Zamora province, NW Spain). A density of two samples per square kilometer (approximately 500 m sample spacing along streams), a sample volume of 10 l and sieving at 5 mm ensure that an anomaly source is detected. It was found that the dispersion of scheelite is typically less than 1 km. The methods applied to panned concentrates (mineralometric scheelite study, with or without multifractional grain size basis, and X-ray fluorescence tungsten analysis) give similar anomaly patterns and are efficient in exploration for scheelite mineralization.Peer reviewe

Aspectos geoquímicos y mineralógicos de la prospección aluvionar para Sn en dos áreas de la provincia de Salamanca.

Universidad de la Coruña. Area de Xeoloxía e Minería

Late postmagmatic alterations in the tin-bearing batholith of Ricobayo (Iberian Massif, NW Spain)

[EN] The deuteric alteration processes undergone by the granites of the Ricobayo Batholith were: microclinization, chloritization, albitization, muscovitization, tourmalinization and garnetization. These processes must be interpreted in a dynamic context so that the different reactions that take place are the consequence of a successive interaction between rock and fluids. The physicochemical conditions deduced from these fluids are: temperature lower than 600 OC, pressure between 1.5 and 1 Kb, fugacity of oxygen between 10-25 and 10-35 bars, fugacity of sulphur lower than 10-l5 bars, the composition was kept stable and their log (a(K+)/a(Ht)) and log (a(Na+)/a(H+)) varied between 3.8 and 3.2 and between 3.5 and 4.6, respectively, and the pH of the fluids was higher than 5 during the microclinization, muscovitization and tourmalinization, and lower during chloritization and albitization. The deposition of cassiterite occurs with pH episodes that exceed 5.`[ES] En el Batolito de Ricobayo (Zamora, noroeste de Espana) se ha podido distinguir la siguiente secuencia de procesos de alteración: microclinización, cloritización, albitización, moscovitizaciÓn, turmalinización y granatización. Estos procesos se han producido como consecuencia de la interacción entre fluidos y roca en las etapas tardi- y post-magmáticas del mencionado batolito. Las condiciones físico-químicas deducidas para estos fluidos son: temperatura inferior a 600 OC, presión entre 1.5 y 1 Kb, fugacidad de oxigeno entre 10-25a nd 10-35b ars, fugacidad de azufre inferior a 10-'s bars, la composición se mantuvo esencialmente estable y su log (a(K+)/a(Ht)) y log (a(Na+)/a(H+)) variaron entre 3.8 y 3.2 y entre 3.5 y 4.6, respectivamente, mientras que el pH de 10s fluidos fue superior a 5 durante la microclinización, moscovitización y turmalinización, e inferior durante la cloritización y la albitización. En 10s estadios con pH superior a 5 tuvo lugar la precipitación de casiterita.Peer reviewe