Bárcena, M.A. & Flores, J.A. (1991): La Clase Centrobacillariophyceae (Div. Bacillariophycea) de los sedimentos superficiales obtenidos en la campaña "Antártida 8611". Stvdia Geologica Salmanticensia, 27: 7-31.
ABSTRACT: Centrobacillariophyceae marine diatoms included in surface sediments in the Atlantic sector of the Antarctic, were studied. Sistematic and quantitative analysis was carry aut to show the variability of assemblages in relation to environmental and oceanographic changes. Preservational aspects were also considered to evaluate the degree of alteration; likewise related with the oceanographic pattern.
Álvarez, F. (1991): Aspectos estructurales y petrológicos del vulcanismo neógeno en la parte oriental de la Sierra Almagrera Cordilleras Béticas Orientales). Stvdia Geologica Salmanticensia, 27: 33-44.
ABSTRACT: In the eastern part of the Sierra Almagrera, situated to the east of the Betic Mountain range, there are small outcrops of volcanic rocks that are encased in the form of sills and dykes in schists belonging to the Nevado Filabride Complex. Their distribution is related to that of the fracturation systems trending N10º 30ºE and N40º 60ºE produced by the transpressive tectonics that ocurred in this region during the Neogene.
The nature of the lava is potassic calc alkaline, shoshonitic and, to a lesser extent, ultrappotassic. Their injection is related to the first Neogene magmatic period of the south of Spain; the age of this magmatic activity is supposed to be Upper Miocene.
Reguilón Bragado, R.M. & Arribas Moreno, A. (1991): Contenido y distribución de U y Th en el granito de Montánchez, Cáceres (España). Stvdia Geologica Salmanticensia, 27: 45-61.
ABSTRACT: The Montánchez granite (Caceres) consist of three main facies. Facies I, made up of two mica granites with a predoinance of muscovite, is highly defor~ned and has medium to coarse grain. Facies II is composed of two mica granites with a predominance of biotite and coarse grain size. Facies III is made up of muscovitic granites with aplitic character, has little biotite but is rich in tourmaline.
Geochemically, The granites are alkaline with a arked peralouminous nature.
The mean content in U in the 19 samples analyzed is 5,5 ppm while that of this 2,9 ppm, the mean of the Th/U ratio being 1,9. The highest U contents are found in facies III, within the aplitic granites, whereas those of Thare found in facies II, although the tonalitic samples show a considerable increase in the Th content due to the presence of Th bearing minerals, narnely zircon and monacite, which are included in the biotite. In the case of U, the mean contents are higher than those reported by Rogers y Adams (1969) for several World granites considered to be standard (3,9 ppm). By contrast, those of Th are considerably lower than those given vy the same autors for the same granites (20 ppm).
The high mean content of U in the Montánchez granite means that it should be considered as metalliferous for U.
Pérez del Villar, L. & Martín-Herrero, D. (1991): Características litológicas y estructurales del Complejo Esquisto-Grauváquico en la zona de Cañaveral-Zarza La Mayor (provincia de Cáceres). Stvdia Geologica Salmanticensia, 27: 63-84.
ABSTRACT: The essential lithological and structural features of the metasediments of the Complejo Esquisto Grauvaquico~ (C.E.G.) in the Canaveral Zarza la Mayor zone are described in this paper.
These features have allowed to establish the correIation between these metasediments and the ones that constitute the Lower Series, also belonging to the C.E.G., defined to the North of the studied zone.
The studied metasediments are affected by several phases of deformation, two pre Ordovician, one hercynian and two late hercynian. Likewise, they are cut by several hercynian and late hercynian fracture systems, among which a subhorizontal conjugated one can be remarked for being the host of the uraniferous ores, existing in the studied zone.
Pérez del Villar, L. & Moro C. (1991): Las mineralizaciones intragraníticas de Uranio en el batolito de Cabeza de Araya (provincia de Cáceres): El Saguazal, brechas NNE y La Zafrilla. Stvdia Geologica Salmanticensia, 27: 85-112.
ABSTRACT: The U mineralizations within the most evolved granitic facies of the Cabeza de Araya batholith are controlled by reverse faults, N120 130E (El Saguazal, or by subvertical ones, NNE (La Zafrilla). Two different paragenesis have been identified in these mineralizations separated by a brecchiation process. The second one is rich in U and is constituted by pyrite, pitchlende (gummites) and cryptocrystalline silica, This paragenesis is typical of the U epithermal deposits with quartz or jasper, which are the best ones represented in the Hesperian Massif.
The origin of the mineralizations is related to the remobilization, transport and redeposition of the disperse U in the host granites, This is a consequence of the joint action or the granite weathering and the hydrothermal stage associated with the development of huge sinistral strike slip faults that, with a NNE direction, affected the zone.
Consequently, it can be assu~ned that the first U mineralizing process ocurred in the Permian. That is, after the faults had become inactive at the beginning of the Triassic period. The possibility of remobilizations during the intrusion of the NNE basic dykes and the alpine fracture type tectonic cannot be put aside.
Fernández Álvarez, A. & Moro Benito, M.C. (1991): Estudio de las magnetitas de Latedo: Contribución al conocimiento geológico y metalogénico de las mineralizaciones de hierro asociadas a los materiales ordovícicos de la provincia de Zamora. Stvdia Geologica Salmanticensia, 27: 113-130.
ABSTRACT: A geo1ogical, mineralogical and geochemical study of the sedimentary Iron ores from Latedo (Zamora) has been performed. The mineralizations are associated to Ordovician materials in the South limh of the Alcañices Synform. The palaeogeographic features, the depositional environment and the provenance of the mineralization are analyzed. The physico chemical conditions in which the magnetite and chlorite constituting the mineralization were formed are stablished.
Gil Agero, M. & Moro Benito, M.C. (1991): Geología y metalogenia de las mineralizaciones de W, (Sn y P) asociadas a los niveles calcosilicatados del Complejo Esquisto Grauváquico (C.E.G.) de Villalcampo (provincia de Zamora). Stvdia Geologica Salmanticensia, 27: 131-150.
ABSTRACT: In this paper the geological, morphological, mineralogical and geochimical features of the calcosilicates ore levels in W (scheelite) and other elements (Sn and P) inter bedded in C.E.G., in Villalcampo (Zamora) are studied. So, it was realized petrological work of the ethamorphic and igneous host rocks, Finally, we stablish the genetical and spatial relations of the ore levels and associate rocks of the C.E.G., to know the origin and genesis of these mineralizations.
Hernández Sánchez, E. & Moro Benito, M.C. (1991): Geología de los materiales del Complejo Granítico-Metamórfico de Villaseco-Pereruela (Zamora). Stvdia Geologica Salmanticensia, 27: 151-174.
ABSTRACT: This paper is a study of the "Villaseco Pereruela" Granitic Metamorphyc Complex, situated western to Zamora town. In it, the cartographic, litologic, structural and compositional features of the metasedimentary, metavolcanic sedimentary and intrusive granitic materials are described.
The first kind of materials, with an age Pre Arening is a stratigraphyc serie which is formed since the botton to the top by gneisses with "eyes" texture, and over they, biotitic moscovitic schists with some quarzitic levels. At the top of the serie there is another gneis level, with "eyes" texture too, but different to the first unit. All this serie is affected by three main strain fases with associated metamorphisrn and other later corresponding to the Hercinic Orogeny. The intrusive rocks are leucogranites and outcrout with massive shapes and dikes with variable dip. These rocks have been considered sintectonic with the third hercinic fase. The attributed origin for these rocks is the anatexia, not too deep, in the matasedimentary serie.
Hernández Sánchez, E. & Moro Benito, M.C. (1991): Las mineralizaciones de Sn asociadas al Complejo de Villaseco-Pereruela y a la cizalla dextra de Pereruela-Villalcampo (Zamora). Stvdia Geologica Salmanticensia, 27: 175-195.
ABSTRACT: This paper is a study of the tin mineralizations associated to the Villaseco Pereruela Granitic Mctamorphic Complex, The only tin mineral, cassiterite, occurs as accessory mineral in applites with a hight content of albite, and also disseminated in granite hosted veins. The mining operations have been made in the granite mainly. Also, the spatial, genetic and chronological relations between ore, quartz veins and the Pereruela Villalcampo shear zone are studie in this paper.
Liso, M.J., Rincón, J.M. & Casilla, R. (1991): Presencia de CaSbO4 en La Codosera (Badajoz). Stvdia Geologica Salmanticensia, 27: 197-206.
ABSTRACT: A antimonate of calcium has been found in the "San Antonio" mine en La Codosera (N Badajoz) (Spain) with estabine scheelite paragenesis.
X ray diffraction, electron microscopy (SEM), chemical analysis (ASS) and chemical microanalysis (SEM/EDX) have been used to characterize this mineral.
Its crystalchemistry formula is:
Sb0,987O4(Ca1,046Fe0,091Na0,004Cu0,004)(OH)0,054