Person: Fernández Barrenechea, José María
Universidad Complutense de Madrid
Faculty / Institute
Mineralogía y Petrología
Cristalografía y Mineralogía
Now showing 1 - 10 of 22
PublicationClay minerals as provenance indicators in continental lacustrine sequences: the Leza Formation, early Cretaceous, Cameros Basin, northern Spain(Blackwell Scientific publications, 2005) Alonso Azcárate, Jacinto; Rodas, Magdalena; Fernández Barrenechea, José María; Mas Mayoral, José RamónVariations in clay mineral assemblages, changes in KuÈbler index (KI), and the chemical composition of chlorites are used to identify source areas in the lacustrine materials in the Lower Cretaceous Leza Limestone Formation of the Cameros Basin, northern Spain. This formation has fairly homogeneous lithological characteristics and facies associations which do not allow for identification and characterization of local source areas. The Arnedillo lithosome of the Leza Limestone Formation contains a clay mineral association (Mg-chlorite, illite and smectite) indicative of its provenance. Chlorite composition and illite KI values indicate that these minerals were formed at temperatures higher than those reached by the Leza Formation which indicates its detrital origin. The similarity in the Mg-chlorite composition between the Arnedillo lithosome and the Keuper sediments of the area indicates that these materials acted as a local source area. This implies that Triassic sediments were exposed, at least locally, at the time of deposition of the Leza Formation. The presence of smectite in the Leza Formation is related to a retrograde diagenesis event that altered the Mg-chlorites in some samples. PublicationInfluence of grinding on graphite crystallinity from experimental and natural data: implications for graphite thermometry and sample preparation(Mineralogical Society (Great Britain), 2006) Crespo Feo, Elena; Luque del Villar, Francisco Javier; Fernández Barrenechea, José María; Rodas, MagdalenaThis paper examines the effects of shear stress on the structuralparameters that define the ‘crystallinity’ of graphite. The results show that highly crystalline graphite samples ground for up to 120 min do not undergo detectable changes in the three-dimensional arrangement of carbon layers but crystallite sizes (Lc and La) decrease consistently with increasing grinding time. Grinding also involves particle-size diminution that results in lower temperatures for the beginning of combustion and exothermic maxima in the differentialthermalanal ysis curves. These changes in the structuraland thermalcharacteristics of graphite upon grinding must be taken into account when such data are used for geothermometric estimations. Tectonic shear stress also induces reduction of the particle size and the Lc and La values of highly crystalline graphite. Thus, the temperature of formation of graphite according to structural as well as thermaldata is underestimated by up to 100ºC in samples that underwent the most intense shear stress. Therefore, application of graphite geothermometry to fluid-deposited veins where graphite is the only mineralfound should take into consideration the effect of tectonic shearing, or the estimated temperatures must be considered as minimum temperatures of formation only. PublicationMechanical graphite transport in fault zones and the formation of graphite veins(Mineralogical Society (Great Britain), 2005) Crespo Feo, Elena; Luque del Villar, Francisco Javier; Fernández Barrenechea, José María; Rodas, MagdalenaThis paper describes a vein-shaped graphite occurrence in which, for the first time, the geological, mineralogical and isotopic evidence support its formation by physical remobilization of previously formed syngenetic graphite. The deposit studied is located in the Spanish Central System and it occurs along the contact between a hydrothermal Ag-bearing quartz vein and a graphite-bearing quartzite layer. The characteristics of this occurrence differ from those of fluid-deposited vein-type graphite mineralization in that: (1) graphite flakes are oriented parallel to the vein walls; (2) graphite crystallinity is slightly lower than in the syngenetic precursor (graphite disseminated in the quartzite); and (3) the isotopic signatures of both types of graphite are identical and correspond to biogenic carbon. In addition, the P-T conditions of the hydrothermal Ag-bearing quartz veins in the study area (P <1 kbar, and T up to 360ëC) contrast with the high degree of structural order of graphite in the vein. Therefore, physical remobilization of graphite can be regarded as a suitable alternative mechanism to account for some cases of vein-shaped graphite deposits. Such a mechanism would require a previous concentration of disseminated syngenetic graphite promoted, in this case, by the retrograde solubility of quartz. This process would generate monomineralic graphite aggregates enhancing its lubricant properties and permitting graphite to move in the solid state along distances in the range of up to several metres. PublicationCaracterización de la materia carbonosa grafitizada de las pizarras silúricas de San Ciprián- Hermisende (Zamora)(Sociedad Española de Mineralogía, 2009-09) Crespo Feo, Elena; Rodas, Magdalena; Arche, Alfredo; Fernández Barrenechea, José María; Wada, Hideki; Luque del Villar, Francisco Javier PublicationEvolución de la mineralogía de arcillas en el tránsito diagénesis-metamorfismo de bajo grado en el grupo Urbión (Cretácico inferior) de la cuenca de los Cameros (Soria-La Rioja)(Universidad Complutense de Madrid, Servicio de Publicaciones, 2002) Fernández Barrenechea, José María; Rodas, Magdalena; Mas, J. RSe ha realizado un estudio de la evolución de la mineralogía de arcillas en los materiales pertenecientes al grupo urbión (cretacico inferior), en las zonas afectadas por diagénesis y metamorfismo de bajo y muy bajo grado, en relación con los medios de sedimentación en la cuenca de los cameros. Se han diferenciado cuatro unidades estratigraficas (a,b,c y d) limitadas por discontinuidades, que van siendo progresivamente mas extensivas. El estudio sedimentologico de estos materiales indica que corresponden a sistemas fluviales meandriformes (con desarrollo de lagos carbonatados someros en el sector oriental), así como a sistemas fluviales entrelazados (borde occidental). El carácter de los sedimentos va siendo gradualmente mas distal hacia el sector oriental de la cuenca. Las muestras correspondientes a las unidades a, b y c en las areas depocentrales presentan una asociación mineralógica característica de condiciones epimetamorficas, mientras que en el sector oriental se estiman condiciones próximas al limite entre anqui-epimetamorfismo. Los valores de "cristalinidad" de la ilita en estas muestras son mayores de lo esperado, debido a la presencia de paragonita e interestratificado moscovita/paragonita asociados a la reflexión a 10 a. Las muestras pertenecientes a la unidad d en las areas depocentrales representan un brusco cambio hacia condiciones anquimetamorficas, marcado por la presencia de pirofilita y rectorita, mientras que en el borde occidental corresponden a diagénesis profunda. Los cambios en las asociaciones de minerales de la arcilla y en los valores de "cristalinidad" se relacionan con la circulación de fluidos hidrotermales asociados a una banda de deformacion, mas que con la profundidad de enterramiento. La litologia (permeabilidad y composición global) es el principal factor que controla la circulación de dichos fluidos PublicationPalaeoenvironmental significance of Late Permian palaeosols in the South-Eastern Iberian Ranges, Spain(Blackwell Publishing Ltd, 2008) Horra del Barco, Raúl de la; Benito Moreno, María Isabel; López Gómez, José; Arche, Alfredo; Fernández Barrenechea, José María; Luque del Villar, Francisco JavierThe Late Permian (Wuchiapingian) Alcotas Formation in the SE Iberian Ranges consists of one red alluvial succession where abundant soil profiles developed. Detailed petrographical and sedimentological studies in seven sections of the Alcotas Formation allow six different types of palaeosols, with distinctive characteristics and different palaeogeographical distribution, to be distinguished throughout the South-eastern Iberian Basin. These characteristics are, in turn, related to topographic, climatic and tectonic controls. The vertical distribution of the palaeosols is used to differentiate the formation in three parts from bottom to top showing both drastic and gradual vertical upwards palaeoenvironmental changes in the sections. Reconstruction of palaeoenvironmental conditions based on palaeosols provides evidence for understanding the events that occurred during the Late Permian, some few millions of years before the well-known Permian-Triassic global crisis. PublicationEarly Triassic-Anisian continental sediments from SE Iberian ranges: sedimentological and mineralogical features(Sociedad Española de Mineralogía, 2008-09) Galán Abellán, Ana Belén; Fernández Barrenechea, José María; López Gómez, José; Lago San José, Marceliano; Benito Moreno, María Isabel PublicationA new triadotypomorphan insect from the Anisian (Middle Triassic), Buntsandstein facies, Spain(Universidad Complutense de Madrid, 2009) Béthoux, Olivier; Horra del Barco, Raúl de la; Benito Moreno, María Isabel; Fernández Barrenechea, José María; Galán Abellán, Ana Belén; López Gómez, JoséThe species rubra sp. nov., a new triadotypomorphan insect from the Iberian Ranges, is described on the basis of a newly discovered specimen, found in fine grained sandstones of alluvial origin, in the lowermost part of the Eslida Formation (Buntsandstein facies), in the central part of the Iberian Ranges. The occurrence of a triadotypomorphan suggests an Anisian age of the Eslida Formation. The species represents the oldest Mesozoic insect described from Spain, and provides interesting information to better appreciate the process of ecosystems recovery after the Permian-Triassic boundary crisis. [RESUMEN] La especie rubra sp. nov., un nuevo insecto triadotipomorfo de la Cordillera Ibérica, es descrito en este trabajo en base a un nuevo espécimen hallado en un nivel de areniscas de grano fino de origen aluvial en la parte más baja de la Formación Eslida (facies Buntsandstein), en la zona central de la Cordillera Ibérica. La aparición de este triadotipomorfo confirma la edad Ansíense (Triásico Medio) de la Formación Eslida. La especie encontrada representa el insecto más antiguo hallado en el Mesozoico de España y una interesante información para comprender mejor el proceso de recuperación de los ecosistemas tras la crisis del límite Pérmico-Triásico. PublicationLate Permian continental sediments in the SE Iberian Ranges, eastern Spain: Petrological and mineralogical characteristics and palaeoenvironmental significance(Elsevier, 2005) Benito Moreno, María Isabel; Horra del Barco, Raúl de la; Fernández Barrenechea, José María; López Gómez, José; Rodas, Magdalena; Alonso Azcárate, Jacinto; Arche, Alfredo; Luque del Villar, Francisco JavierA detailed mineralogical and petrological study and the analysis of paleosol profiles in continental alluvial sediments of the Late Permian in the SE Iberian Ranges (Spain) allow us to infer the significant environmental changes that occurred during this time period. Three parts have been distinguished in the Late Permian sediments (Alcotas Formation). The lower part includes abundant and well-preserved carbonate paleosol profiles and fine-grained sediments made up by quartz, feldspar, hematite and illite, with scarce kaolinite. The preservation of dolomicrite in some paleosols suggests that they originally developed as dolocretes in an arid to semi-arid climate with marked seasonality. A change towards more humid and acid conditions can be deduced from the presence of siderite and goethite in paleosols in the middle part of the Alcotas Formation. Moreover, the presence of plant remains, coal beds and/or carbonaceous shales at the top of the middle part, and the lack of carbonate paleosols in the upper part of the formation would indicate a further step towards acid conditions. These conditions would increase until the Early Triassic, as indicated by the lack of carbonates and the presence of Sr-rich aluminium phosphate sulphates (APS minerals) at the base of the Triassic (Can˜ izar Formation), which clearly indicates extreme acid conditions during the Permian–Triassic transition of the study area. PublicationSandstone petrography of continental depositional sequences of an intraplate rift basin: western Cameros Basin (North Spain)(SEPM (Society for Sedimentary Geology), 2009) Arribas Mocoroa, José; Alonso Millán, Ángela; Mas Mayoral, José Ramón; Tortosa, A.; Rodas, Magdalena; Fernández Barrenechea, José María; Alonso Azcárate, Jacinto; Artigas, RosanaThe Cameros Basin in Central Spain is an intraplate rift basin that developed from Late Jurassic to Middle Albian time along NW–SE trending troughs. The sedimentary basin fill was deposited predominantly in continental environments and comprises several depositional sequences. These sequences consist of fluvial sandstones that commonly pass upward into lacustrine deposits at the top, producing considerable repetition of facies. This study focused on the western sector of the basin, where a total of seven depositional sequences (DS- 1 to DS-7) have been identified. The composition of sandstones permits the characterization of each sequence in terms of both clastic constituents and provenance. In addition, four main petrofacies are identified. Petrofacies A is quartzosedimentolithic (mean of Qm85F2Lt13) and records erosion of marine Jurassic pre-rift cover during deposition of fluvial deposits of DS-1 (Brezales Formation). Petrofacies B is quartzofeldspathic (mean of Qm81F14Lt5) with P/F > 1 at the base. This petrofacies was derived from the erosion of low- to medium-grade metamorphic terranes of the West Asturian–Leonese Zone of the Hesperian Massif during deposition of DS-2 (Jaramillo Formation) and DS-3 (Salcedal Formation). Quartzose sandstones characterize the top of DS-3 (mean of Qm92F4Lt4). Petrofacies C is quartzarenitic (mean of Qm95F3Lt2) with P/F > 1 and was produced by recycling of sedimentary cover (Triassic arkoses and carbonate rocks) in the SW part of the basin (DS-4, Pen˜ - acoba Formation). Finally, depositional sequences 5, 6, and 7 (Pinilla de los Moros–Hortigüela, Pantano, and Abejar–Castrillo de la Reina formations, respectively) contain petrofacies D. This petrofacies is quartzofeldspathic with P/F near zero and a very low concentration of metamorphic rock fragments (from Qm85F11Lt4 in Pantano Formation to Qm73F26Lt1 in Castrillo de la Reina Formation). Petrofacies D was generated by erosion of coarse crystalline plutonics located in the Central Iberian Zone of the Hesperian Massif. In addition to sandstone petrography, these provenance interpretations are supported by clay mineralogy of interbedded shales. Thus, shales related to petrofacies A and C have a variegated composition (illite, kaolinite, and randomly interlayered illite–smectite mixed-layer clays); the presence of chlorite characterizes interbedded shales from petrofacies B; and Illite and kaolinite are the dominant clays associated with petrofacies D. These petrofacies are consistent with the depositional sequences and their hierarchy. An early megacycle, consisting of petrofacies A and B (DS-1 to DS-3) was deposited during the initial stage of rifting, when troughs developed in the West Asturian–Leonese Zone. A second stage of rifting resulted in propagation of trough-bounding faults to the SW, involving the Central Iberian Zone as a source terrane and producing a second megacycle consisting of petrofacies C and D (DS-4, DS-5, DS-6, and DS-7). Sandstone composition has proven to be a powerful tool in basin analysis and related tectonic inferences on intraplate rift basins because of the close correlation that exists between depositional sequences and petrofacies.