Geogaceta -- Nº 20-7, (1996)

Permanent URI for this collectionhttps://hdl.handle.net/10272/12840

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834S de los sulfuros silúricos tipo "sedex" de Latedo-Sejas de Aliste (Zamora, España)
(Sociedad Geológica de España, 1996) Timón, S. M.; Moro Benito, M. C.; Fernández Fernández, A.
The sulphides of Latedo-Sejas are mainly constituted of pyrite-pyrrhotite and, on the basis of their textural and structural characteristics, two mineralógicaI stages have been differentiated: syn-diagenetic and/or metamorphic (before or syn-phase 1) and syn-phase 3. The mineralization is associated to two processes of alteration: carbonatization and chloritization. Owe to S34S values, a biogenic origin can be attributed to these sulphides with greater hydrothermal contamination in Latedo. The changes in 8 34S values are due to the transit from a deep anoxic to another shallow and coastal environment in the sedimentary basin
Visión global del Proyecto Berrocal. Planteamiento y objetivos
(Sociedad Geológica de España, 1996) Hernán, P.
The El Berrocal Project was preceded by a preliminary study (0 Phase) started in 1989, intended to prepare and ensuring the performance of the actual Project that was divided in two two-year phases. At its very origin the Project was mainly conceived to achieve strategic objectives of methodology and instrumentation development and building up of R and D working teams. All this addressed to the study of radionuclide natural migration in a fractured granitic environment. As the Project progress it incorporates the concept of Natural Analogue and subsequently the Project objectives are more directly focussed to the Performance Assessment of HLRW repositories. In this global introduction to the Project an overview is given that covers organisational aspects, together with a summary of the sequence of activities. A final list of the technical reports produced within the project Is included
Un yacimiento de Au en carbonates del Orógeno Hercínico: el área de Salamón (N León)
(Sociedad Geológica de España, 1996) Paniagua, A.; Rodriguez Pevida, L. S.; Loredo, J.; Fontboté, L.; Fenoll Hach-Ali, P.
The Salamon gold prospect constitutes an example o f carbonate-hosted gold deposit formed during the last events of the Hercynian orogeny. It is formed by a complex paragenetic sequence o f Au-As-Sb-Hg-Cu-NI-Co-Pb-Zn-U minerals in jasperoid and quartz-dolomite host rock. Au correlated positively with As at single crystal scale in pyrite and arsenopyrite, of fluid inclusion study and arsenopyrite geothermometry show temperatures in the range 140-280°C at 350-400 bars. Stable isotope data suggest reduction of sulfur from marine evaporites and buffer of carbon in the fluid by the host carbonates.The age of the deposit is 269 ± 5 m. y., U-Pb determination on uranite grains gires and which is consistent with on uranite age from Villamarin and with age determinations of intrusive rocks spatially associated to several ore deposits in the area
Tectónica distensiva jurásica en el Subbético Externo oriental (Sureste de España)
(Sociedad Geológica de España, 1996) Rey Arrans, Javier
The stratigraphy and evolution of the subsidence during the Jurassic in an eastern section of the External Subbetic (External Zones of the Betic Cordilleras) have been analized. Backstripping curves are constructed, and they are compared with theoretically calculated tectonic subsidence curves. Margin evolution was quite complex, with distinct syn-rift and post-rift phases, affected by significant tectonic activity
Relación entre metamorfismo y mineralización en las rocas básicas y ultrabásicas de Mina Salamanca y los Gateados (Provincia de Mendoza, Argentina)
(Sociedad Geológica de España, 1996) Sánchez Anguita, A.; Molina, J. F.; Gervilla, Fernando; Fenoll Hach-Ali, P.; Acevedo Carmona, Rubén Darío
The basic and ultrabasic rocks from Mina Salamanca district and Los Gateados area are metamorphosed in epidote-amphibolite facies, and locally, in greenschist facies conditions. The green chist facies assemblages develop associated to carbonate (± .quartz ) veins in the amphibolites and to talc + magnesite assemblages in serpentinites . In the latter case, the fluids dissolved a primary, disseminated sulfide mineralization and gave rise to a massive ore along a fault zone in Mina Salamanca district
Rasgos estructurales principales de la cuenca cretácica inferior del Maestrazgo (Cordillera Ibérica oriental)
(Sociedad Geológica de España, 1996) Salas, Ramón; Guimerà, J.
The Maestrat basin (up to 6.5 km of Mesozoic sediments) is an intracontinental basin located in the Iberian Range (Iberian Basin), which underwent two significant rift stages during the Late Jurassic and Early Cretaceous. The rift structure is characterised by a system of ESE-WNW extensional Ustric faults which are detached in a shallow upper crustal level. These faults record two well-differentiated periods: i) Late Jurassic, and ii) Early Cretaceous, and divide the Maestrat basin into several blocks. These blocks controlled seven main sub-basins (Fig. 1): 1) Penyagolosa sub-basin (PC), 2) La Salzedella sub-basin (Sa), 3) Morelia sub-basin (Mo), 4) El Perello sub-basin (Pe), 5) Aliaga sub-basin (Al), (6) Galve sub-basin (Ca), and 7) Oliete sub-basin (Ol)
Procesos que afectan a la movilidad del U y otros elementos traza en entornos graníticos y a baja temperatura. Experiencias del Proyecto Berrocal
(Sociedad Geológica de España, 1996) Bruno Salgot, J.
The main processes affecting the retardation and mobility of U and other trace elements In the El Berrocal environment are presented and discussed. Particular emphasis is put in recent low temperature events that indicate the linkage between trace element and major component (Fe, HC03-) cycles. The results from kinetic and thermodynamic modelling calculations indicate that the initially mobilised U(IV) from the uraninites is effectively retained by interactions with Fe (III) -oxihydroxides
Procesos de interacción agua-roca y comportamiento del uranio en el sistema granítico de El Berrocal (España)
(Sociedad Geológica de España, 1996) Gómez, P.; Turrero, J.; Peña, J.; Gimeno, María J.; Crespo, M. T.; Gordienko, F.; Martínez, B.; Reyes, E.; Rivas, P.; Ivanovich, M.
This work depicts a synthesis of the main water-rock interaction processes controlling the water chemistry in El Berrocal granitic pluton, emphasizing in the uranium geochemistry. An uranium-sulphide dyke controls the general characteristics of the system at the site scale. Dissolution/precipitation of calcite Is the m ost im p o rta n t process in the area. U ra n iu m concentration ranges from 4x10 ~9M to 8x10 ' 6M . Undersaturation with respect to most of uranium minerals occurs in the water. Adsorption processes can be considered as main mechanism of uranium retention
Pirofanita y Braunita titànica en las rocas con Mn del Sector Central de Ossa-Morena
(Sociedad Geológica de España, 1996) Jiménez Millán, Juan; Velilla, N.
In the Oliva de la Frontera area (Ossa-Morena Central Belt, Iberian Massif, SW Spain) titanian braunite occurs in manganiferous metashales and manganiferous metatuffs while pyrophanite is restricted to pyroxmangite metatuffs. During hercynian metamorphism primary Mn4+ was reduced to Mn3+ and Mn2+ to form piemontlte in shales and metatuffs, and more extensively in piroxmangite metatuffs to form pyrophanite. Ti and Al-enrichment in braunite depend on the whole composition while high Fe-content in braunite of piroxmangite metatuffs can be related to low f02 conditions
Peloides de glauconita y apatito en sedimentos carbonatados mesozoicos del sector oriental de la Zona Subbética (provincia de Alicante)
(Sociedad Geológica de España, 1996) Nieto, Luis M.; Jiménez Millán, Juan; Molina, José Miguel; Nieto García, F.
Glauconite and apatite peloids occur in jurassic and cretaceous bioclast-bearing carbonate rocks from the Algayat-Crevillente Unit (Subbetic Zone). The size and the morphology of peloids are controlled by the bioclasts. Internal texture commonly evidence that the glauconite form nuclei surrounded by apatite. K content is elevated in both stratigraphic positions but higher in the cretaceous glauconites than the jurassic glauconites. Textural and chemical evidence indicate a model of glauconitization with two steps: an early dissolution-crystallization process and a further process of K-enrichment. Low K-content in jurassic glauconites can be explained by the calcitic early diagenetic cementation which stops the second step of glauconitization, while the low Fe content of this glauconites could be a later effect due to a deeper burial diagenesis
Origen de escapolitas asociadas a doleritas triásicas del Norte de la provincia de Cádiz
(Sociedad Geológica de España, 1996) Morata Céspedes, Diego; Domínguez Bella, S.; Morales Ruano, S.
Scapolites are present in some doleritic tectonic blocks C'ophites" )in the External Zones o f the Betic Cordilleras, In Northern of Cadiz province. These scapolites fill veinlets and replace plagioclases from the dolerites in the proximity of fissures. Scapolites (Me262g) are partial or totally replaced by low-iron prehnites (XFe3+ = 0.13-0. 66). Fluid inclusions found in scapolites show high salinity (40-55% wt. eq.) multications (Na-Ca-K.?) aqueous fluids. No volatil phases has been detected in microthermometric runs. Temperatures of homogeneization range from 380 to 540°C. These scapolites filling dolerite veinlets are interpreted as a result of magma-evaporite Interactions during dolerite emplacement into the Triassic evaporitic formations
Nuevos datos geológicos sobre las mineralizaciones de grafito de la Banda Metamorfica de Aracena, Huelva (Macizo Ibérico Meridional)
(Sociedad Geológica de España, 1996) Fernández Rodríguez, Carlos; Fernández Caliani, Juan Carlos; Miras, A.; Barrenechea, J. F.; Luque, F. J.; Rodas, M.
In this work a detailed geological map o f the graphite mineralizations of the Aracena Metamorphic Belt (SW Iberian Massif) is shown. Three types of mineralizations have been distinguished according to lithostratigraphic and structural criteria: 1) Stratiform deposits related to gneissic lenticular bodies embedded within a complex calc-silicate sequence 2) Veinlets of graphite cutting across mafic granulites; and 3) Disseminated graphite within gneisses and quartzites belonging to the Fuente del Oro series. Only the first type of mineralizations could have an economic interest
Minerales de tierras raras en las carbonatitas del Complejo Basal de Fuerteventura (Islas Canarias)
(Sociedad Geológica de España, 1996) Mangas, J.; Pérez Torrado, Francisco J.; Martín Izard, A.; Reguilón Bragado, R. M.
The Fuerteventura carbonatites appear in the Complejo Basal as veins, breccias and shear bands in the coastline between Puerto de la Pena and Cueva de Lobos, and in the Esquinzo ravine zone. These carbonatites are formed by calcite mainly and apatite, aegirine-augite, albite, orthoclase-sanidine, biotite, epidote and ore minerals occur in lower amounts, and as accessory minerals titanite, zircon, garnet, celestite, barite, brithdlite, allanite, pyrochlore and monazite. Geochemical analysis o f these carbonatites show high values] of REE between 511 and 7,372 ppm, with high relation LREE/HREE. Microprobe studies show that these elements mainly are associated with phosphates (britholite, monazite and apatite), silicates (allanite and titanite), oxides (pyrochlore), carbonates (bastnaesite) and sulphates (barite). The carbonatites have been generated in the last magmatic-hydrothermal crystallization phases of the alkaline intrusive complexes of Fuerteventura
Metamorfismo y magmatismo del Paleozoico inferior en la zona central de las Sierras Pampeanas (SW de Gondwana)
(Sociedad Geológica de España, 1996) Pascua, M. I.; Saavedra, J.; Baldo, Edgardo G.
The Sierra de Los Llanos intrusion is a Lower Paleozoic pluton of meta-aluminous granites (with tholeiitic and calc-alkaline features) representative of batholiths of the Sierras Pampeanas, here associated to small bodies of cordieritic granite and metamorphic septa that upgrade from weak contact to strong grade of metamorphism, emplaced at low depth. The first data (spatial and temporal associations, etc.) suggest a genetic relation to a heterogeneous source, with contamination, by crustal materials and other processes, of mantelic arc magmas
Los pisos estratigráficos y la paleogeografía del Cámbrico en España: una visión retrospectiva
(Sociedad Geológica de España, 1996) Liñán Guijarro, Eladio
The Cambrian biostratigraphy and chronostratigraphy of the Iberian Peninsula has been studied since the beginning of the past decade by the Spanish Working Croup of the ICCP projects, 29 and 303, followed by palaeogeographical studies within the ICCP project 319. Numerous sections in Spain and Portugal have been sampled for trilobites, arqueocyaths, acritarchs, small shelly fossils, microbiotas and trace fossils. In this way a stratotype for the Precambrian/Cambrianboundary was proposed in Central Spain, and at the same time the former regional stages Ovetian, Marianian and Bilbilian (and the new Cordubian Staged for the Lower Cambrian were revised. The Leonian and Caesaraugustian stages have also been proposed for the Middle Cambrian while, a third and younger Middle Cambrian stage is now being studied in Northern Spain and Southern France. This Cambrian chronostratigraphical scale is now applied elsewere in South Europe by foreign research groups. Studies in palaeoecology and event stratigraphy have permitted to subdivide the Spanish Lower Cambrian into transgressive/regressive sequences. They have been correlated with other events of similar age from other countries and continents. By means of both chronostratigraphic and event stratigraphy scales, it has been possible to summarize the Spanish Cambrian System into palaeogeographical maps and to stabllsh this palaeogeographical evolution as related to a generalized rifting process
Los depósitos minerales de pirofilita de Villa Unión (Rioja Argentina) y sus posibles aplicaciones en cerámica y vidrio
(Sociedad Geológica de España, 1996) Fiscina, J.; Malachevsky, M. T.; Jordán, M. M.; San Feliú, T.; Rincón, J. M.; Romero, M.
The pyrophillite and sericite from the Mining District of Villa Union , Rioja, in Argentina arew eelknown because they are a wide area of metamorphic rocks, Precambric or Paleozoic, well distributed and communicated at approx. 20 km from National Roads. Nowadays, two ores with different mixtures of: pyrophillite + kaolinite + quartz ( white and brilliant ) and other constituted by sericite ( schist aspect and silk b r i l l i a n t ) are being exploted. In o rd e r to define the applications as ra w materials fo r ceramics and glasses production, a full characterization of the Vicchi and San Lorenzo Mines materials are being carried out. Several ceramics, traditional and advanced, are being obtained and materials characterized for best define the applications of this argentinian raw materials. It has been demonstrated the obtention of ceramics based on cordierite and/ or leucite by formulating ceramic bodies from this pyrophiiiite products
Los depósitos de Mn de La Margarita y Los Chivos, Cuba Oriental
(Sociedad Geológica de España, 1996) Cazañas Díaz, X.; Melgarejo i Draper, J. C.
The stratiform ore deposits o f Los Chivos and La Margarita manganese , consist o f ore-rich beds (massive, mainly constituted by botrioidal todorokite), and ore-poor beds (todorokite cementing vulcanoclastics). They are associated to jasper and celadonite beds. Hydrothermal alteration occurs at the basis of the deposits, and this indicates the proximity of exhalative centers. According to textural evidences, synsedimentary and diagenetic ore removilization is also present
Las mineralizaciones de U de la Carretona y Casa del Gallo En el granito de Albala (Câceres)
(Sociedad Geológica de España, 1996) Reguilón Bragado, R. M.; Arribas, A.; Martín lzard, A.; Mangas, J.
The U mineralizations that are estudied in this paper are hosted in Albalagranite.They are controled by late Hercinian vertical or subvertical faults, with an aproximate orientation of N30°E. The mineral association in them comprises pichblenda, coffinite, blackoxides, piryte mar casite,melnicovite and some sphalerite in La Carretona, and black oxides,pyrite and melnicovite in Casa del Gallo. In both cases the gangue is made up of quartz, jasper and apatite.The origin of the uranium that gives rise to these mineralizations comes from the remobilizations of this element present in the host granite, basically in the form of uraninite, as a consequence of the early hydrothermal weathering of these granites, which occurred during,discontinuous proceses and supergenic weathering .Hence, we suggest that the first mineralizing process of the uranium took place during the sub-solid state of the granite, as a consequence of the leaching of U due to late hydrothermal fluids during the Permian Period, the posibility of a remobilization of U during the late alpinefracturation cannot be excluded. Finally, from the end of the tertiary to the present the latest stage of weathering and a concentration of the U have occurred, forming the hexavalent minerals
Las mineralizaciones de wolframio asociadas a la granodiorita de Santa Coloma (Andorra)
(Sociedad Geológica de España, 1996) Espinola, M. R.; Soler Gil, Albert; Arcos, D.
The late Hercynian Santa Coloma granodiorite intruded Paleozoic metasediments of upper Ordovician to Devonian age. Several forms of tungsten-bearing ores are found associated to the Santa Coloma granodiorite in the Central Pyrenees: veins, filled joints and skarns. Fluid inclusion study in quartz crystals from veins suggests that the mineralising fluid was a polysaline brine (22 wt% NaCI eq.) wich was trapped at 360 ±30 °C and 2.5 ±0.3 kbar, even the first mineralizing stage could be formed at higher temperatures (up to 500°C). Preliminary data of 8 MS of sulphides from skarn and vein mineralizations show values near 5 ± 1%o suggesting a sulphur of magmatic origin
Las mineralizaciones auríferas de los Pirineos y su significado en la evolución del orógeno Hercínico
(Sociedad Geológica de España, 1996) Soler Gil, Albert; Cardellach, Esteve; Arcos, D.; Delgado, J.
G old is found in the Hercynian terranes of Central and Eastern Pyrenees as disseminations in metasediments of lower Paleozoic age; in veins contemporaneous with the main Hercynian foliation; in veins related to the Hercynian shear zones, faults and thrusts that postdate the main foliation and in skarns related to late Hercynian granites. Gold is associated to arsenopyrite, a typical feature throughout the Pyrenees. Two types of mineralizing fluid have been recognized: a C 0 2- rich lo w s a lin ity (6% w t N aCI eq.) fluid, present in the synfoliation veins and a C 0 2- free and high s a lin ity (up to 30% w t NaCI eq) fluid found in the post-foliation deposits. Ore deposition took place around 500 °C and 5kb in the synfoliation veins and around 350 °C and 2kb in the post-foliation veins and skarns. The late Hercynian uplift of themetamorphic terranes caused a steep rise in the thermal gradient (from 25 to 50°C/km), theexpansion of porous fluid, and its migration into faults and thrusts. In the case of the skarns, the fluids were mobilized because of the thermal gradient related to the contact metamorphism.

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