Orejana García, David

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First Name
Last Name
Orejana García
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Geológicas
Mineralogía y Petrología
Petrología y Geoquímica
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Now showing 1 - 10 of 54
  • Publication
    Mineral chemistry of late Variscan gabbros from central Spain: constraints on crystallisation processes and nature of the parental magmas
    (Universidad Complutense de Madrid, 2015) Orejana García, David; Losantos, E.; Villaseca González, Carlos; Jeffries, T.E.
    Major and trace element chemistry has been determined in the main minerals (olivine, orthopyroxene, clinopyroxene, plagioclase, amphibole, phlogopite) from the Talavera and La Solanilla gabbroic intrusions (Spanish Central System). The results show a heterogeneous mineral composition illustrative of the chemical evolution of calc-alkaline basic magmas during crystallization. The formation of incompatible element-rich interstitial minerals, such as amphibole, phlogopite and accessory phases (e.g., zircon, apatite), and the presence of zoning patterns in major minerals towards a more evolved composition, point to a progressive differentiation of the parental melt. The chemical variation depicted by trace elements usually incompatible with clinopyroxene (e.g., rare earth elements (REE), Th, Zr, Nb, Ti) implies co-precipitation with phases displaying a compatible behaviour with respect to these elements (e.g., apatite, zircon, amphibole). However, the very high LILE (large ion lithophile elements) and LREE (light REE) shown by clinopyroxene can not be explained exclusively by a closed-system in-situ crystallization process. Several features of the mineral chemistry (e.g. positive correlation of (La/Sm)N with La and Na in clinopyroxene and plagioclase, respectively) support the involvement of an external component (wall-rock assimilation or hybridization with an evolved melt). The petrography and mineral chemistry of the gabbros, in conjunction with bulk rock data from previous studies, favour a calc-alkaline affinity for the parental melts. Thus, metasomatism in the mantle sources related with this basic magmatism might be associated with recycling of crustal components during the Variscan orogeny.
  • Publication
    Early Proterozoic zircons in Variscan gabbros from central Spain: Evidence of an Icartian magmatic event at mantle depths?
    (Elsevier Science Ltd, 2009) Villaseca González, Carlos; Orejana García, David; Armstrong, R.A.; Pérez-Soba Aguilar, Cecilia; Merino Martínez, Enrique
  • Publication
    Mineral chemistry of megacrysts and associated clinopyroxenite enclaves in the Calatrava volcanic field: crystallization processes in mantle magma chambers
    (Universidad Complutense de Madrid, 2019) Villaseca González, Carlos; Dorado, Olaya; Orejana García, David
    Megacristales de clinopiroxeno, anfíbol y flogopita aparecen en los depósitos piroclásticos ricos en cristales, enclaves y xenolitos, de los volcanes de El Aprisco y Cerro Pelado (campo volcánico de Calatrava). Estos megacristales muestran una composición química similar a los cristales que forman los enclaves clinopiroxeníticos asociados, incluyendo los poco comunes enclaves ricos en flogopita (glimmeritas). El magma volcánico es de textura porfídica, mostrando una compleja población de fenocristales y macrocristales máficos, con núcleos residuales, que sugieren formen una suite cogenética con aquellos. Las estimaciones geobarométricas indican que los megacristales, así como los núcleos de fenocristales y los enclaves clinopiroxeníticos representan acumulados de alta presión, formados entre 12–16 kbar, en el manto litosférico superior (de 35 a 55 km). La variabilidad composicional de estos minerales máficos apunta a un proceso de diferenciación controlado por la cristalización de olivino, clinopiroxeno, anfíbol y flogopita. La cristalización de minerales máficos hidratados en el manto facilitaría la exsolución de CO2 y la subsecuente ebullición del fundido, posibilitando la fragmentación de los márgenes semicristalinos de la cámara magmática y la excavación de la roca mantélica encajante. Esta fragmentación profunda explicaría también la compleja variedad de cristales, enclaves y xenolitos atrapados por los magmas volcánicos. Se han encontrado dos tipos de clinopiroxenos (verde e incoloro) que aparecen como antecristales (núcleos de macrocristales/fenocristales) y también en los enclaves piroxeníticos. La coexistencia de ambos tipos de clinopiroxeno en los zonados cristalinos de las clinopyroxenitas sugiere que deben ser cogenéticos, representando precipitados de fundidos de distinto grado evolutivo, pero posiblemente de un mismo magma fraccionante. Este estudio propone un modelo de ascenso y origen de magmas ricos en cristales y xenolitos que puede ser útil para explicar otros tipos volcánicos que transportan complejos cargamentos de cristales profundos, como ocurre frecuentemente en la provincia volcánica circum-Mediterránea.
  • Publication
    Geochemistry and geochronology of mafic rocks from the Spanish Central System: Constraints on the mantle evolution beneath central Spain
    (Elsevier, 2019) Orejana García, David; Villaseca González, Carlos; Kristoffersen, M.
    The Spanish Central System (SCS) contains several suites of Palaeozoic mafic igneous intrusions with contrasting geochemical affinity: Ordovician tholeiitic metabasites, Variscan calc-alkaline gabbros (Gb1) and microdiorites (Gb2), shoshonitic monzogabbros (Gb3) and alkaline diabases and lamprophyres (Gb4). Not all of these rocks are accurately dated, and several aspects of their genesis are still poorly understood. We present new whole-rock geochemical data (major and trace elements, and Sr–Nd isotopes), U–Pb and Lu–Hf isotopic ratios on magmatic zircons and 40Ar/39Ar amphibole geochronology results in order to establish a precise chronology for the successive events of magmatism in the SCS, and discuss the nature of their mantle sources. Accurate ages have been determined for the Variscan gabbros (305–294 ​Ma), the microdiorites (299 ​Ma) and the accompanying felsic porphyries (292 ​Ma), the shoshonitic monzogabbros (285 ​Ma), and the alkaline diabases (274 ​Ma) and monzosyenites (271–264 ​Ma). According to this information, the Variscan mafic magmatism would be mainly concentrated in the range of 305–294 ​Ma, with a final manifestation represented by the minor shoshonitic dykes. The alkaline magmatism proved to be slightly older than previously thought and yielded at least two distinct pulses: diabases and lamprophyres–monzosyenites. Zircon Hf isotopes evidence the involvement of depleted and slightly enriched mantle sources. The bulk of the εHf values are in the broad range of −8 to +11, indicative of melting both depleted and enriched mantle regions. The high within-sample Hf isotope variation (up to ~11 epsilon units) shown by samples from the Variscan series (gabbros, microdiorites and monzogabbros) could be explained mainly by hybridisation of magmas derived from heterogeneous lithospheric mantle sources. Pressure estimates indicate that the Variscan mafic magmas were extracted from the lithosphere. The Nd–Hf isotopic composition of these suites of rocks suggests the recycling of pelitic sediments during the Cadomian orogeny. Deeper (asthenospheric) mantle levels were involved in the generation of the alkaline suite, whose anomalous negative εHf values (moderately decoupled with respect to radiogenic Nd) could be associated with subducted oceanic components raised by mantle upwelling associated with lithosphere thinning and extension during the Permian.
  • Publication
    Aplicaciones geotermobarométricas de los contenidos en elementos trazas de minerales granulíticos: Zr en rutilo y HREE en granate de los xenolitos félsicos de la corteza inferior del Sistema Central Español
    (Sociedad Geológica de España, 2006) Villaseca González, Carlos; Orejana García, David
    Geothermobarometric estimations based on the trace element concentration of minerals from lower crustal peraluminous felsic granulite xenoliths from the Spanish Central System (SCS) have been performed. Zr in rutile thermometry (Zack et al., 2004) gives a main range of 970 to 1100 ºC whereas HREE in garnet barometry (Bea et al., 1997) yields a pressure range of 7.2 to 9.3 kbar. These new thermobarometric data overlap previous P-T estimates based on conventional metamorphic phase equilibria. Nevertheless, the slightly higher temperature range obtained with rutile thermometry force to future revision of granulite mineral equilibria of the SCS lower crustal xenoliths.
  • Publication
    Estimación del régimen térmico y producción de calor de los niveles litosféricos del Sistema Central Español
    (Sociedad Geológica de España, 2005) Villaseca González, Carlos; Orejana García, David; Pérez-Soba Aguilar, Cecilia; Reyes Andrés, Jesús
    Heat production of outcropping metamorphic and granitic rocks from the Spanish Central System (SCS) is similar to other surface heat production estimates in Paleozoic provinces (average A value 2.64 mWm-3). However, heat flow range in the SCS is higher than for Paleozoic terranes (70-90 mWm-2 instead of 45-70 mWm-2). Contribution of mantle to the heat budget is estimated to be 27 mWm-2. Thus, a slightly higher mantle heat flow combined with a lower crust with a markedly high heat production (average A value 1.04 mWm-3) may explain the high estimated surface heat flow.
  • Publication
    Análisis de la evolución en la adquisición de competencias específicas y transversales en los Grados de Geología e Ingeniería Geológica
    (2019-06-28) García Lorenzo, Mari Luz; Abati Gómez, Jacobo; Orejana García, David; Castiñeiras García, Pedro; Crespo Feo, María Elena; Piña García, Rubén; García Romero, Emilia; Granja Bruña, José Luis; López García, José Ángel; Fernández Barrenechea, José María; Arribas Mocoroa, María Eugenia; Ortega Menor, Lorena; Pérez Moreno, Elisa María; Benito Moreno, María Isabel
  • Publication
    Petrografía de rocas ígneas
    (2008-10-02) Villaseca González, Carlos; Andonaegui Moreno, Pilar; Huertas Coronel, María José; Orejana García, David
    Es un tratado práctico de petrografía de rocas ígneas o magmáticas que cubre diversos aspectos: mineralogía fundamental y accesoria de las rocas magmáticas; fábrica (textura y estructura) de las rocas ígneas; clasificaciones modales y descripción de los principales tipos de rocas y series ígenas, tanto volcánicas como plutónicas.
  • Publication
    Composition and evolution of the lithospheric mantle in central Spain: inferences from peridotite xenoliths from the Cenozoic Calatrava volcanic field
    (Geological Society of London, 2010) Villaseca González, Carlos; Ancochea Soto, Eumenio; Orejana García, David; Jeffries, Teresa E.
    Spinel lherzolite xenoliths from the Cenozoic Calatrava volcanic field provide a sampling of the lithospheric mantle of central Spain. The xenoliths are estimated to originate from depths of 35–50 km. Trace element content of clinopyroxene and Cr-number in spinel indicate low degrees of partial melting (5%) of the xenoliths. Although a major element whole-rock model suggests wider degrees of melting, the Calatrava peridotite chemistry indicates a moderately fertile mantle beneath central Spain. Calatrava peridotite xenoliths bear evidence for interaction with two different metasomatic agents. The enrichment in LREE (light rare earth element), Th, U and Pb, and the negative anomalies in Nb–Ta in clinopyroxene and amphibole from xenoliths of El Aprisco, indicate that the metasomatic agent was probably a subduction-related melt, whereas the enrichment in MREE in clinopyroxene from xenoliths of the Cerro Pelado centre suggests an alkaline melt similar to the host undersaturated magmas. These metasomatic agents are also consistent with the chemistry of interstitial glasses found in xenoliths of the two volcanic centres. Differences in metasomatism but also in mantle composition is supported by Sr–Nd whole-rock data, which show a more radiogenic nature for Sr isotopes of samples from the El Aprisco centre (87Sr/86Sr ratios of 0.7035–0.7044 instead of 0.7032–0.7037 for samples from Cerro Pelado). The timing of the subduction-related metasomatic stage is unconstrained, although the Calatrava intraplate volcanism intrudes an old Variscan lithospheric section reworked during the converging plate system affecting SE Iberia in the Tertiary. The presence of wehrlite types within the Calatrava peridotite xenoliths is here interpreted as a reaction of host lherzolites with silica-undersaturated silicate melts that could be related to the Calatrava alkaline magmatism. The Sr–Nd isotopic composition of Calatrava peridotites plot within the European asthenospheric reservoir (EAR) mantle, these values represent more enriched signatures than those found in the other Spanish Cenozoic alkaline province of Olot.
  • Publication
    Heterogeneous metasomatism in cumulate xenoliths from the Spanish Central System: implications for percolative fractional crystallization of lamprophyric melts
    (Geological Society of London, 2008) Orejana García, David; Villaseca González, Carlos
    The alkaline lamprophyres and diabases from the Spanish Central System carry a heterogeneous suite of xenoliths including a group of highly altered ultramafic pyroxenites that contain Cr–Mg-rich high-T hydrous minerals (Ti-phlogopite and pargasitic to kaersutitic amphibole), indicative of modal metasomatism. The trace element mineral compositions of these xenoliths show three patterns: type A xenoliths, with light rare earth element enriched clinopyroxenes with high field strength element (HFSE) negative anomalies; type B xenoliths, with clinopyroxenes and amphiboles with high incompatible trace element contents (large ion lithophile elements (LILE), HFSE and REE); type C xenoliths, with relatively REE- and HFSE-poor clinopyroxenes and amphiboles. These metasomatic signatures suggest the involvement of three different metasomatic agents: carbonate, silicate and hydrous fluids or melts, respectively. These agents could have been derived from the progressive differentiation of a CO2–H2O-rich highly alkaline magma, genetically related to the Late Permian alkaline magmatism. Because of the original sub-alkaline nature of the pyroxenite xenoliths, theymight have been formed originally as pyroxene-rich cumulates associated with underplated Hercynian calc-alkaline basic magmas. Metasomatism as a result of the infiltration of alkalinemagmaswithin these cumulatesmight explain the relatively high radiogenic Nd composition of the altered ultramafic xenoliths.