Search

La presente Tesis doctoral recoge la caracterización petrográfica y geoquímica del manto subcontinental litosférico (MSCL) bajo el centro de la Península Ibérica a partir del estudio de los xenolitos peridotíticos y piroxeníticos del Campo Volcánico de Calatrava (CVC). Su caracterización geoquímica se ha llevado a cabo gracias a la química de roca total y de sus principales minerales constituyentes, tanto de los elementos mayores como los trazas. También se ha podido analizar su composición isotópica (Sr-Nd) para precisar la naturaleza del MSCL muestreado en el centro de Iberia. En la Región Volcánica Central de España, como la denominó Hernández-Pacheco en 1932, caracterizada por su volcanismo básico alcalino y ultraalcalino, y su condición de campo volcánico monogenético, solo se han encontrado xenolitos procedentes del MSCL en seis de sus más de 260 centros volcánicos. Además de los xenolitos ultramáficos en los que se centra esta Tesis, los fundidos alcalinos del CVC también transportaron una rica y variada carga cristalina que consiste en megacristales de clinopiroxeno, anfíbol y flogopita, de acumulados de grano fino clinopiroxeníticos (y glimmeríticos) y una compleja población de macrocristales y fenocristales (clinopiroxeno verde e incoloro, anfíbol, flogopita y olivino)..., This PhD Thesis reports petrographical, mineralogical and geochemical characterization of the subcontinental lithospheric mantle (SCLM) under the central parts of the Iberian Peninsula by the study of ultramafic xenoliths of the Calatrava Volcanic Field (CVF). The geochemical characterization has been carried out by whole rock analyses and the main mafic minerals chemical composition, both major and traces elements. It has also been possible to analyze whole-rock isotopic compositions (Sr-Nd isotopic signatures) to improve the sampled SCLM nature from the center of Iberia.The Región Volcánica de España (named by Hernández-Pacheco, 1932) is characterized by being a monogenetic volcanic field of basic alkaline and ultra-alkaline magmatism. Peridotite xenoliths have been only found in six of the more than 260 volcanic centres of the CVF. The CVF alkaline melts also transported a rich, varied and complex crystal cargo consisting of clinopyroxene, amphibole and phlogopite megacrysts, fine-grained aggregates of clinopyroxenites, with igneous textures and zoned clinopyroxene crystals, and a complex population of phenocrysts (green and colourless clinopyroxene, amphibole, phlogopite, and olivine)...

Much of the lithospheric subcontinental mantle (SCLM) sampled in the Calatrava Volcanic Field (CVF) shows refertilization by alkaline metasomatic agents. The Cerro Pelado and El Palo ultramafic xenolith suites record the best evidence of this type of metasomatism in this volcanic field. Several groups of peridotite (lherzolite, wehrlite, and dunite) and pyroxenite (clinopyroxenite and websterite) xenoliths have been distinguished. Despite having scarce phlogopites and amphiboles as modal metasomatic phases, all studied xenoliths present a variable cryptic metasomatism, highlighted by the strong Fe-Ti enrichment and fractionated REE patterns in the most evolved wehrlite and pyroxenite varieties. They show a common trend of an Fe-Ti-Ca increase, whereas the pyroxenites are more depleted in Fe compared to the lherzolites and wehrlites. Trace-element (REE and multi-trace) patterns are roughly similar among them, suggesting different interactions and refertilization degrees by alkaline silicate melts. The same Sr–Nd isotopic EAR composition, combined with trace-element chemistry of metasomatic xenolith phases and phenocrysts from the Calatrava volcanics, highlights the main role of this magmatism in percolation processes beneath Central Iberia. These mantle xenoliths also show variable amounts of interstitial glass that originated by in situ partial melting, favored by the enriched chemical nature of cryptically metasomatized clinopyroxene during their volcanic transport. This alkaline-refertilized mantle type represents the main domain within the SCLM beneath Central Iberia, as was also recorded in other Western European Cenozoic volcanic fields., Ministerio de Ciencia e Innovación, Depto. de Mineralogía y Petrología, Fac. de Ciencias Geológicas, TRUE, pub

Two types of lherzolite xenoliths appear in the Cerro Gordo maar from the Cenozoic Calatrava volcanic field. Hydrous lherzolites (group-1) show a major proportion of metasomatic amphibole (>5 modal%), whereas group-2 lherzolites have only accessory amounts or an absence of amphibole. Group-1 lherzolites show a higher LREE-Ba-Sr-Th content in whole-rock composition compared to group-2 lherzolites. The most depleted group-2 lherzolite xenoliths indicate a low degree of partial melting (<5%) of the mantle source, similarly to other Calatrava xenolith suites. Trace element content combined with Sr-Nd isotopic ratios suggests a protolith mantle source with the characteristics of a depleted MORB Mantle (DMM type). This mantle protolith was later refertilized by subduction-related metasomatism, causing the formation of modal amphibole and obliterating the original MORB-like chemical features in the most transformed xenoliths (group-1 lherzolites). The entrainment of these mantle fragments in the volcanic alkaline magma promoted amphibole breakdown reactions during its transport, generating silica-rich glasses with the associated unusual formation of secondary orthopyroxene. The suprasubduction character of the protolithic mantle combined with previously published Re-Os model ages in nearby lherzolite xenoliths suggests that the sampled lherzolites could represent the old Cadomian mantle wedge of the Central Iberian zone., Secretaría de Estado de Investigación, Desarrollo e Innovación, Universidad Complutense de Madrid, Depto. de Mineralogía y Petrología, Fac. de Ciencias Geológicas, TRUE, pub

Two types of lherzolite xenoliths appear in the Cerro Gordo maar from the Cenozoic Calatrava volcanic field. Hydrous lherzolites (group-1) show a major proportion of metasomatic amphibole (>5 modal%), whereas group-2 lherzolites have only accessory amounts or an absence of amphibole. Group-1 lherzolites show a higher LREE-Ba-Sr-Th content in whole-rock composition compared to group-2 lherzolites. The most depleted group-2 lherzolite xenoliths indicate a low degree of partial melting (<5%) of the mantle source, similarly to other Calatrava xenolith suites. Trace element content combined with Sr-Nd isotopic ratios suggests a protolith mantle source with the characteristics of a depleted MORB Mantle (DMM type). This mantle protolith was later refertilized by subduction-related metasomatism, causing the formation of modal amphibole and obliterating the original MORB-like chemical features in the most transformed xenoliths (group-1 lherzolites). The entrainment of these mantle fragments in the volcanic alkaline magma promoted amphibole breakdown reactions during its transport, generating silica-rich glasses with the associated unusual formation of secondary orthopyroxene. The suprasubduction character of the protolithic mantle combined with previously published Re-Os model ages in nearby lherzolite xenoliths suggests that the sampled lherzolites could represent the old Cadomian mantle wedge of the Central Iberian zone., Secretaría de Estado de Investigación, Desarrollo e Innovación, Universidad Complutense de Madrid, Depto. de Mineralogía y Petrología, Fac. de Ciencias Geológicas, TRUE, pub

En el volcán de Los Tormos (Campo de Calatrava) se han distinguido dos grupos principales de xenolitos mantélicos en función del análisis modal, presencia de anfíbol y composición química del clinopiroxeno, lo que permite deducir al menos dos sectores del manto ligados a eventos metasomáticos de diferente naturaleza. El grupo más abundante son lherzolitas con espinela, formados por minerales con contenidos altos de Mg, y clinopiroxeno con bajo contenido en elementos traza incompatibles y espectros normalizados relativamente planos, que evidenciaría afinidad con un manto empobrecido tipo MORB, el manto más primitivo del conjunto. Sin embargo, las anomalías negativas en Nb-Ta y enriquecimiento variable en los elementos más incompatibles (Th, U, Pb, tierras raras ligeras) y elementos móviles (Sr, K, Ba) en dichos espectros indicarían la interacción con fluidos metasomáticos derivados de zonas de ubducción, que actuarían con distinta intensidad. Las wehrlitas con anfíbol destacan por la riqueza en hierro de sus minerales, así como por la composición del clinopiroxeno, con espectros de elementos traza normalizados enriquecidos en los elementos medianamente incompatibles, todo lo cual sugiere el paso de fundidos metasomáticos de naturaleza silicatada alcalina rica en carbónico. Este mismo metasomatismo afectaría a algunos xenolitos lherzolíticos con espectros similares., In xenoliths from the Los Tormos volcano (Calatrava volcanic field), two main mantle xenolithic groups have been distinguished according to modal analysis, amphibole occurrence and clinopyroxene chemical composition. These features suggest different origins for each xenolith group, evidencing mantle sectors metasomatized by different agents. The spinel-bearing lherzolite xenoliths define the most abundant group, showing high magnesium and low trace-element contents in the rock-forming minerals, with nearly flat clinopyroxene trace element pattern, suggesting affinity to depleted mantle sources (MORB type). The well-pronounced Nb-Ta negative anomaly in these patterns indicates later variable interaction with subduction-related metasomatic agents. The amphibole-bearing wehrlite group shows Fe-rich mineralogy and clinopyroxene normalized trace-element spectra enriched in the most incompatible elements, defining typical metasomatism by carbonate-rich silica under-saturated alkaline melt. The other xenoliths showing similar trace element patterns than hydrous wehrlites are also affected by silica-undersaturated alkaline metasomatism., Ministerio de Ciencia e Innovación (MICINN), Universidad Complutense de Madrid, Depto. de Mineralogía y Petrología, Fac. de Ciencias Geológicas, TRUE, pub

This work reports petrographical, mineralogical and geochemical data of a suite of mantle xenoliths from the Morrón de Villamayor volcanic centre (MVM), which belongs to the Calatrava Volcanic Field (CVF), a part of the Circum-Mediterranean Anorogenic Cenozoic Igneous Province. The MVM volcano is the only centre belonging to the first stage of the CVF magmatism, an ultrapotassic stage that provides a sampling of the subcontinental lithospheric mantle beneath central Spain. The MVM peridotites record a variable host melt interaction (spongy texture and reaction zones), more intense toward xenolith-host leucitite contacts that it was formed during transport within the volcanic melt. The studied mantle xenoliths are spinel lherzolites equilibrated at lower temperatures (618–942 °C) and similar pressure ranges (8.8–13.6 kbar) than other studied CVF mantle xenoliths, and record a lithospheric mantle before the main volcanic Calatrava event. The MVM lherzolites could be classified in two groups by their chondrite-normalized rare earth element (REE) clinopyroxene patterns: group-1 lherzolites show flat pattern, and group-2 lherzolites display a LREE-depleted (N-MORB like) pattern. Group-1 lherzolites represent a more residual lithospheric mantle (up to 9 partial melting %) than group-2 lherzolites (~ 5%), the latter with similar partial melting degrees than other mantle xenoliths from the CVF. Moreover, group-1 lherzolites have undergone a post partial melting refertilization by different metasomatic agents: silicate and alkaline silicate melts different in composition to host leucitite. A primary clinopyroxene concentrate from these MVM lherzolites provides high Sr (87Sr/86Sr = 0.706104) and intermediate Nd (143Nd/144Nd = 0.512830) initial radiogenic ratios, not previously recorded in this volcanic field. This sampling proves the presence of an enriched isotope mantle pole in xenolith suites of the Calatrava area, trending in composition to an intermediate DMM-EMII compon, Ministerio de Ciencia e Innovación (MICINN), Universidad Complutense de Madrid, Depto. de Mineralogía y Petrología, Fac. de Ciencias Geológicas, TRUE, pub

El centro volcánico de El Palo contiene varios tipos de xenolitos ultramáficos (peridotitas y piroxenitas) que registran diversos procesos ocurridos en el manto litosférico. Estos enclaves están equilibrados a temperaturas altas (1072– 1127ºC) y presiones muy variadas (7.3–13.8 kbar), dependiendo del tipo de enclave muestreado. El conjunto de xenolitos equilibrados a mayor profundidad son peridotíticos. Consisten en dos grupos de lherzolitas y una werhlita, que, en este orden, muestran gradualmente más enriquecimiento en Fe-Ti y patrones más fraccionados de REE normalizados al condrito. Los enclaves clinopiroxeníticos representarían acumulados fraccionados de magmas basálticos alcalinos a distintos niveles del manto y equilibrados en el límite con la corteza. La websterita, con mayor contenido en Al2O3 y menor en Cr2O3, está equilibrada a mayor profundidad que las clinopiroxenitas y su origen podría estar relacionado con magmas más subalcalinos., The El Palo volcano contains several groups of ultramafic (peridotite and pyroxenite) xenoliths that record enrichment processes within the lithospheric mantle. These mantle xenoliths are equilibrated at high temperatures (1072–1127ºC), though the pressures are very varied (7.3-13.8 kbar) depending on the xenolith type sampled. Xenoliths equilibrated at greater depth are mostly peridotites. They comprise two lherzolite groups and one werhlite sample, gradually more enriched in Fe-Ti and correlated with more fractionated chondrite-normalized REE patterns. Clinoyroxenites represent cumulates fractionated from alkaline basaltic magmas at shallower mantle depths and equilibrated near the crust-mantle boundary. The websterite is equilibrated at a greater depth than clinopyroxenites and its origin may be related to subalkaline melts., Ministerio de Ciencia e Innovación (MICINN), Universidad Complutense de Madrid, Depto. de Mineralogía y Petrología, Fac. de Ciencias Geológicas, TRUE, pub

El centro volcánico de El Palo contiene varios tipos de xenolitos ultramáficos (peridotitas y piroxenitas) que registran diversos procesos ocurridos en el manto litosférico. Estos enclaves están equilibrados a temperaturas altas (1072– 1127ºC) y presiones muy variadas (7.3–13.8 kbar), dependiendo del tipo de enclave muestreado. El conjunto de xenolitos equilibrados a mayor profundidad son peridotíticos. Consisten en dos grupos de lherzolitas y una werhlita, que, en este orden, muestran gradualmente más enriquecimiento en Fe-Ti y patrones más fraccionados de REE normalizados al condrito. Los enclaves clinopiroxeníticos representarían acumulados fraccionados de magmas basálticos alcalinos a distintos niveles del manto y equilibrados en el límite con la corteza. La websterita, con mayor contenido en Al2O3 y menor en Cr2O3, está equilibrada a mayor profundidad que las clinopiroxenitas y su origen podría estar relacionado con magmas más subalcalinos., The El Palo volcano contains several groups of ultramafic (peridotite and pyroxenite) xenoliths that record enrichment processes within the lithospheric mantle. These mantle xenoliths are equilibrated at high temperatures (1072–1127ºC), though the pressures are very varied (7.3-13.8 kbar) depending on the xenolith type sampled. Xenoliths equilibrated at greater depth are mostly peridotites. They comprise two lherzolite groups and one werhlite sample, gradually more enriched in Fe-Ti and correlated with more fractionated chondrite-normalized REE patterns. Clinoyroxenites represent cumulates fractionated from alkaline basaltic magmas at shallower mantle depths and equilibrated near the crust-mantle boundary. The websterite is equilibrated at a greater depth than clinopyroxenites and its origin may be related to subalkaline melts., Ministerio de Ciencia e Innovación (MICINN), Universidad Complutense de Madrid, Depto. de Mineralogía y Petrología, Fac. de Ciencias Geológicas, TRUE, pub

En el volcán de Los Tormos (Campo de Calatrava) se han distinguido dos grupos principales de xenolitos mantélicos en función del análisis modal, presencia de anfíbol y composición química del clinopiroxeno, lo que permite deducir al menos dos sectores del manto ligados a eventos metasomáticos de diferente naturaleza. El grupo más abundante son lherzolitas con espinela, formados por minerales con contenidos altos de Mg, y clinopiroxeno con bajo contenido en elementos traza incompatibles y espectros normalizados relativamente planos, que evidenciaría afinidad con un manto empobrecido tipo MORB, el manto más primitivo del conjunto. Sin embargo, las anomalías negativas en Nb-Ta y enriquecimiento variable en los elementos más incompatibles (Th, U, Pb, tierras raras ligeras) y elementos móviles (Sr, K, Ba) en dichos espectros indicarían la interacción con fluidos metasomáticos derivados de zonas de ubducción, que actuarían con distinta intensidad. Las wehrlitas con anfíbol destacan por la riqueza en hierro de sus minerales, así como por la composición del clinopiroxeno, con espectros de elementos traza normalizados enriquecidos en los elementos medianamente incompatibles, todo lo cual sugiere el paso de fundidos metasomáticos de naturaleza silicatada alcalina rica en carbónico. Este mismo metasomatismo afectaría a algunos xenolitos lherzolíticos con espectros similares., In xenoliths from the Los Tormos volcano (Calatrava volcanic field), two main mantle xenolithic groups have been distinguished according to modal analysis, amphibole occurrence and clinopyroxene chemical composition. These features suggest different origins for each xenolith group, evidencing mantle sectors metasomatized by different agents. The spinel-bearing lherzolite xenoliths define the most abundant group, showing high magnesium and low trace-element contents in the rock-forming minerals, with nearly flat clinopyroxene trace element pattern, suggesting affinity to depleted mantle sources (MORB type). The well-pronounced Nb-Ta negative anomaly in these patterns indicates later variable interaction with subduction-related metasomatic agents. The amphibole-bearing wehrlite group shows Fe-rich mineralogy and clinopyroxene normalized trace-element spectra enriched in the most incompatible elements, defining typical metasomatism by carbonate-rich silica under-saturated alkaline melt. The other xenoliths showing similar trace element patterns than hydrous wehrlites are also affected by silica-undersaturated alkaline metasomatism., Ministerio de Ciencia e Innovación (MICINN), Universidad Complutense de Madrid, Depto. de Mineralogía y Petrología, Fac. de Ciencias Geológicas, TRUE, pub

This work reports petrographical, mineralogical and geochemical data of a suite of mantle xenoliths from the Morrón de Villamayor volcanic centre (MVM), which belongs to the Calatrava Volcanic Field (CVF), a part of the Circum-Mediterranean Anorogenic Cenozoic Igneous Province. The MVM volcano is the only centre belonging to the first stage of the CVF magmatism, an ultrapotassic stage that provides a sampling of the subcontinental lithospheric mantle beneath central Spain. The MVM peridotites record a variable host melt interaction (spongy texture and reaction zones), more intense toward xenolith-host leucitite contacts that it was formed during transport within the volcanic melt. The studied mantle xenoliths are spinel lherzolites equilibrated at lower temperatures (618–942 °C) and similar pressure ranges (8.8–13.6 kbar) than other studied CVF mantle xenoliths, and record a lithospheric mantle before the main volcanic Calatrava event. The MVM lherzolites could be classified in two groups by their chondrite-normalized rare earth element (REE) clinopyroxene patterns: group-1 lherzolites show flat pattern, and group-2 lherzolites display a LREE-depleted (N-MORB like) pattern. Group-1 lherzolites represent a more residual lithospheric mantle (up to 9 partial melting %) than group-2 lherzolites (~ 5%), the latter with similar partial melting degrees than other mantle xenoliths from the CVF. Moreover, group-1 lherzolites have undergone a post partial melting refertilization by different metasomatic agents: silicate and alkaline silicate melts different in composition to host leucitite. A primary clinopyroxene concentrate from these MVM lherzolites provides high Sr (87Sr/86Sr = 0.706104) and intermediate Nd (143Nd/144Nd = 0.512830) initial radiogenic ratios, not previously recorded in this volcanic field. This sampling proves the presence of an enriched isotope mantle pole in xenolith suites of the Calatrava area, trending in composition to an intermediate DMM-EMII compon, Ministerio de Ciencia e Innovación (MICINN), Universidad Complutense de Madrid, Depto. de Mineralogía y Petrología, Fac. de Ciencias Geológicas, TRUE, pub

The El Morrón de Villamayor (MVM) peridote xenoliths vary from orthopyroxene-poor lherzolite to wehrlite in modal composition. This compositional feature contrasts with other Calatrava (CVF) xenolith suites. The studied xenoliths equilibrated at lower temperatures (618-942 o C) and slightly shallower (8.8-13.6 kbar) conditions than other CVF peridotites. MVM peridotites show local intense interaction with the host leucitite displaying spongy rims around primary clinopyroxene and also reaction zones with K-rich minerals (e.g., sanidine, leucite and richterite) and widespread clinopyroxene, olivine and spinel neoblasts. Nevertheless, the orthopyroxene-poor character of MVM peridotites might be caused by some previous metasomatic event., Los xenolitos peridotíticos del volcán El Morrón de Villamayor (MVM) son lherzolitas pobres en ortopiroxeno y wehrlitas, en contraste con los datos previos de xenolitos de otros volcanes de Calatrava. Las peridotitas estudiadas están equilibradas a temperaturas más bajas (618-942 o C) y menor profundidad (8,8-13,6 kbar) que las estimadas en otras peridotitas del Campo Volcánico de Calatrava. Localmente hay una intensa interacción del fundido leucitítico con los minerales primarios de la peridotita, ya que se originan zonas de reacción con minerales ricos en K (p.ej., sanidina, leucita y richterita) y frecuentes neoblastos de clinopiroxeno, olivino y espinela. El carácter pobre en ortopiroxeno de las peridotitas MVM debe estar causado por algún evento metasomático previo, Ministerio de Ciencia e Innovación (MICINN), Universidad Complutense de Madrid, Depto. de Mineralogía y Petrología, Fac. de Ciencias Geológicas, TRUE, pub

The El Morrón de Villamayor (MVM) peridote xenoliths vary from orthopyroxene-poor lherzolite to wehrlite in modal composition. This compositional feature contrasts with other Calatrava (CVF) xenolith suites. The studied xenoliths equilibrated at lower temperatures (618-942 o C) and slightly shallower (8.8-13.6 kbar) conditions than other CVF peridotites. MVM peridotites show local intense interaction with the host leucitite displaying spongy rims around primary clinopyroxene and also reaction zones with K-rich minerals (e.g., sanidine, leucite and richterite) and widespread clinopyroxene, olivine and spinel neoblasts. Nevertheless, the orthopyroxene-poor character of MVM peridotites might be caused by some previous metasomatic event., Los xenolitos peridotíticos del volcán El Morrón de Villamayor (MVM) son lherzolitas pobres en ortopiroxeno y wehrlitas, en contraste con los datos previos de xenolitos de otros volcanes de Calatrava. Las peridotitas estudiadas están equilibradas a temperaturas más bajas (618-942 o C) y menor profundidad (8,8-13,6 kbar) que las estimadas en otras peridotitas del Campo Volcánico de Calatrava. Localmente hay una intensa interacción del fundido leucitítico con los minerales primarios de la peridotita, ya que se originan zonas de reacción con minerales ricos en K (p.ej., sanidina, leucita y richterita) y frecuentes neoblastos de clinopiroxeno, olivino y espinela. El carácter pobre en ortopiroxeno de las peridotitas MVM debe estar causado por algún evento metasomático previo, Ministerio de Ciencia e Innovación (MICINN), Universidad Complutense de Madrid, Depto. de Mineralogía y Petrología, Fac. de Ciencias Geológicas, TRUE, pub

The Calatrava volcanic field (CVF) comprises about 250 volcanic centers in an area of ~5000 km2. Detailed studies on mantle xenolith suites have been focused on the Cerro Pelado (Villaseca et al., 2010, and referencestherein) and the El Aprisco (González-Jiménez et al., 2014) volcanoes, and on other CVF edifices (e.g., Andía et al., 2018; García Serrano et al., 2019). The Cerro Gordo (CG) volcano is a composite edifice made by a scoria cone with short lava flows, which was partially destroyed during an explosive stage generating a maar with pyroclastic surge deposits. Some lenticular cm-sized mantle fragments appear dispersedly within these pyroclastic layers. All the sampled peridotite xenoliths are spinel lherzolites, most of them having amphibole in accessory modal amounts. No previous reference on mantle xenoliths was known from this volcano., Depto. de Mineralogía y Petrología, Fac. de Ciencias Geológicas, TRUE, pub

The Calatrava volcanic field (CVF) comprises about 250 volcanic centers in an area of ~5000 km2. Detailed studies on mantle xenolith suites have been focused on the Cerro Pelado (Villaseca et al., 2010, and referencestherein) and the El Aprisco (González-Jiménez et al., 2014) volcanoes, and on other CVF edifices (e.g., Andía et al., 2018; García Serrano et al., 2019). The Cerro Gordo (CG) volcano is a composite edifice made by a scoria cone with short lava flows, which was partially destroyed during an explosive stage generating a maar with pyroclastic surge deposits. Some lenticular cm-sized mantle fragments appear dispersedly within these pyroclastic layers. All the sampled peridotite xenoliths are spinel lherzolites, most of them having amphibole in accessory modal amounts. No previous reference on mantle xenoliths was known from this volcano., Depto. de Mineralogía y Petrología, Fac. de Ciencias Geológicas, TRUE, pub

El volcanismo alcalino se caracteriza porque frecuentemente es portador de xenolitos procedentes del manto. En el campo volcánico de Calatrava, donde varios centenares de volcanes monogénicos de magmas alcalinos y ultralcalinos han sido identificados, se han encontrado en varios de ellos lavas o piroclastos que incluyen estos xenolitos peridotíticos. En el volcán Los Tormos de Pozuelo de Calatrava, que dio lugar a un cono de escorias, también aparecen frecuentes xenolitos de peridotitas, hasta ahora no estudiados. El conjunto de estos xenolitos proporcionan una información valiosa sobre el manto litosférico y, por tanto, el estudio de éstos permitiría aumentar el conocimiento del mismo en el sector correspondiente al centro de la península Ibérica. El muestreo de los xenolitos peridotíticos en el volcán Los Tormos corresponde en su mayoría a lherzolitas, un número menor de harzburgitas y sólo se ha encontrado una wehrlita. La fase alumínica presente en todos ellos es la espinela, que concuerda con las estimaciones de presión (10-15.2 kbar) y temperatura (961-1185 ºC) obtenidas en base a la composición química de fases minerales en equilibrio, y que indican que pertenecen al campo de estabilidad de peridotitas con espinela, con profundidades de 35-55 km. Los modelos de fusión obtenidos a partir de la composición química (estimada) de elementos mayores de roca total y de los minerales primarios de la peridotita (ortopiroxeno, clinopiroxeno, espinela y olivino) muestran un bajo grado de fusión parcial para las lherzolitas (hasta un 10 %) y un mayor grado de fusión (hasta un 15 %) para las harzburgitas. La wehrlita, en cambio, por el bajo Mg# (0.83 – 0.87) de los olivinos en comparación con el de los otros xenolitos, asi como por su composición química estimada (roca total), que no sigue la tendencia de empobrecimiento del manto primordial sino que es más fértil que éste, indica que se trataría de un residuo de fusión parcial que sufrió metasomatismo debido a la interac

Unión Europea. FP7, Ministerio de Economía y Competitividad (MINECO), Universidad Complutense de Madrid/Banco de Santander, Depto. de Mineralogía y Petrología, Fac. de Ciencias Geológicas, TRUE, pub

© C. Villaseca, V.C. Ruíz-Martínez, C. Pérez-Soba, 2017 We thank Alfredo Fernandez Larios for his assistance with the electron microprobe analyses in the Centro Nacional de Microscopia Electronica Luis Bru (UCM). Comments and revision of an early version of the work by Dr. Encarnacion Roda-Robles were very fruitful. We also thank the comments and suggestions made by Montserrat Liesa (Editor) and two anonymous reviewers that greatly increased the quality of the manuscript. This work is included in the objectives and supported by the CGL2016-78796 project of the Spanish MICINN and the Santander-UCM PR26/16-20294 project., Magnetic susceptibility (MS) has been measured in Variscan granites from central Spain. They yield values in the order of 15 to 180 mu SI units for S-and I-type granites, indicating that both types belong to the ilmenite series. Only samples from magnetite-bearing leucogranites from the I-type La Pedriza massif show high MS values, in the order of 500-1400 mu SI, reflecting the presence of this ferromagnetic mineral. Mineral chemistry of magmatic Fe-rich minerals (mainly biotite) suggests similar oxidation values for both granite types. MS values change in highly fractionated granites accordingly either with the presence of rare new Fe-oxide phases (some I-type leucogranites) or with the marked modal amount decrease of Fe-rich minerals (I-and S-type leucogranites). The redox state in highly fractionated granite melts is mostly controlled by magmatic processes that modify redox conditions inherited from the source region. Thus, the occurrence of magnetite or ilmenite in granites is primarily controlled by the oxidation state of the source material but also by the differentiation degree of the granite melt. The presence of magnetite in some Variscan I-type leucogranites might be a consequence of crystal fractionation processes in a more limited mafic mineral assemblage than in S-type granite melts., Ministerio de Ciencia e Innovación (MICINN), Universidad Complutense de Madrid/Banco de Santander, Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

© C. Villaseca, V.C. Ruíz-Martínez, C. Pérez-Soba, 2017 We thank Alfredo Fernandez Larios for his assistance with the electron microprobe analyses in the Centro Nacional de Microscopia Electronica Luis Bru (UCM). Comments and revision of an early version of the work by Dr. Encarnacion Roda-Robles were very fruitful. We also thank the comments and suggestions made by Montserrat Liesa (Editor) and two anonymous reviewers that greatly increased the quality of the manuscript. This work is included in the objectives and supported by the CGL2016-78796 project of the Spanish MICINN and the Santander-UCM PR26/16-20294 project., Magnetic susceptibility (MS) has been measured in Variscan granites from central Spain. They yield values in the order of 15 to 180 mu SI units for S-and I-type granites, indicating that both types belong to the ilmenite series. Only samples from magnetite-bearing leucogranites from the I-type La Pedriza massif show high MS values, in the order of 500-1400 mu SI, reflecting the presence of this ferromagnetic mineral. Mineral chemistry of magmatic Fe-rich minerals (mainly biotite) suggests similar oxidation values for both granite types. MS values change in highly fractionated granites accordingly either with the presence of rare new Fe-oxide phases (some I-type leucogranites) or with the marked modal amount decrease of Fe-rich minerals (I-and S-type leucogranites). The redox state in highly fractionated granite melts is mostly controlled by magmatic processes that modify redox conditions inherited from the source region. Thus, the occurrence of magnetite or ilmenite in granites is primarily controlled by the oxidation state of the source material but also by the differentiation degree of the granite melt. The presence of magnetite in some Variscan I-type leucogranites might be a consequence of crystal fractionation processes in a more limited mafic mineral assemblage than in S-type granite melts., Ministerio de Ciencia e Innovación (MICINN), Universidad Complutense de Madrid/Banco de Santander, Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

El volcanismo alcalino se caracteriza porque frecuentemente es portador de xenolitos procedentes del manto. En el campo volcánico de Calatrava, donde varios centenares de volcanes monogénicos de magmas alcalinos y ultralcalinos han sido identificados, se han encontrado en varios de ellos lavas o piroclastos que incluyen estos xenolitos peridotíticos. En el volcán Los Tormos de Pozuelo de Calatrava, que dio lugar a un cono de escorias, también aparecen frecuentes xenolitos de peridotitas, hasta ahora no estudiados. El conjunto de estos xenolitos proporcionan una información valiosa sobre el manto litosférico y, por tanto, el estudio de éstos permitiría aumentar el conocimiento del mismo en el sector correspondiente al centro de la península Ibérica. El muestreo de los xenolitos peridotíticos en el volcán Los Tormos corresponde en su mayoría a lherzolitas, un número menor de harzburgitas y sólo se ha encontrado una wehrlita. La fase alumínica presente en todos ellos es la espinela, que concuerda con las estimaciones de presión (10-15.2 kbar) y temperatura (961-1185 ºC) obtenidas en base a la composición química de fases minerales en equilibrio, y que indican que pertenecen al campo de estabilidad de peridotitas con espinela, con profundidades de 35-55 km. Los modelos de fusión obtenidos a partir de la composición química (estimada) de elementos mayores de roca total y de los minerales primarios de la peridotita (ortopiroxeno, clinopiroxeno, espinela y olivino) muestran un bajo grado de fusión parcial para las lherzolitas (hasta un 10 %) y un mayor grado de fusión (hasta un 15 %) para las harzburgitas. La wehrlita, en cambio, por el bajo Mg# (0.83 – 0.87) de los olivinos en comparación con el de los otros xenolitos, asi como por su composición química estimada (roca total), que no sigue la tendencia de empobrecimiento del manto primordial sino que es más fértil que éste, indica que se trataría de un residuo de fusión parcial que sufrió metasomatismo debido a la interac

El documento expone brevemente los objetivos, metodología y resultados de un proyecto de innovación docente dedicado a continuar con el desarrollo de una página web para el aprendizaje de aspectos prácticos de petrología ígnea. Este proyecto es la continuación de otro desarrollado durante la convocatoria 2013. La página web creada, denominada ATLAS DE ROCAS ÍGNEAS (http://petroignea.wordpress.com), incluye fotografías de muestras de mano, imágenes de microscopio y de afloramiento de rocas ígneas, así como breves explicaciones de las características principales que se aprecian en dichas imágenes. También se introducen conceptos sobre la clasificación de las rocas ígneas. El proyecto de la convocatoria de 2014 se ha centrado más específicamente en desarrollar aspectos meso y macroscópicos relacionados con la manera en la que se disponen las rocas ígneas en la naturaleza en forma de depósitos más o menos grandes. Para ello, además de fotografías de campo, se han incluido esquemas, diagramas, mapas geológicos o imágenes de satélite. Esta página es de libre acceso y cuenta ya con una notable afluencia de visitantes.

Neoproterozoic metasedimentary units from central Spain and the northern Central Iberian Zone (CIZ) show distinctive geochemical signatures with respect to the Schist-Greywacke Complex, which is dominant in the southwestern part of the CIZ. Significant differences occur in major and trace element composition and initial Nd isotope ratios, which cannot be explained in terms of metamorphic grade and/or anatexis in some layers of these metasedimentary sequences. ɛNd540 values from metapelites of central Spain range from −5.6 to −10.4 whereas those from the Schist-Greywacke Complex span a narrower and higher range of −0.8 to −3.1. This difference suggests different source regions. The presence of two contrasting Early Ordovician magmatic belts in both subzones reinforces the idea of different Precambrian basement terranes in the CIZ. These data are crucial for pre-Variscan paleogeographic reconstructions of the westernmost European terranes and for checking the validity of current subdivisions of the Iberian Massif., Ministerio de Economía y Competitividad (MINECO), Universidad Complutense de Madrid, Depto. de Mineralogía y Petrología, Fac. de Ciencias Geológicas, TRUE, pub

Three distinct S-type peraluminous granitoid types have been identified within the Variscan Montes de Toledo batholith, located in the Central Iberian Zone (SW European Variscides): type-1, extremely high peraluminous restite-rich granitoids; type-2, highly peraluminous restite-bearing granitoids; and type-3, moderately peraluminous granitoids with mafic microgranular enclaves. Type-1 and type-2 granitoids are restricted to the western part of the batholith, whereas type-3 granites are mostly restricted to the eastern segment. There is a sequential youngering of emplacement age from type-1 (late-tectonic) to type-2 and type-3 granitoids (post-tectonic), extending the timing of the batholith formation for about 19 Ma between 316 and 297 Ma. Although the degree of peraluminousity of the different series could be related to different partial melting conditions or to the variable entrainment of restitic components (including the peritectic mineral assemblage of the melting reactions), whole-rock geochemical signatures and isotope zircon composition of the peraluminous granitoid types suggest contribution of different crustal sources. There is no evidence for the direct mantle-derived material contribution in the genesis of these peraluminous melts. Type-1 and type-2 granitoids contain mostly Archean to Neoproterozoic inherited zircons, whereas type-3 granites show preferentially Neoproterozoic (up to late Cryogenian) and Ordovician inheritance. The wide range of initial Hf isotope composition, ranging to highly radiogenic values (ƐHf up to + 10), of Neoproterozoic zircon inheritances in type-1 and type-2 granitoids suggests derivation from heterogeneous Neoproterozoic metasedimentary sources composed of both juveline and recycled crustal materials, similar in composition to the host Schist–Greywacke Complex metasediments. Trace-element modelling clearly suggests the involvement of metasediments similar to those mentioned from the southern part of the Central Iberian Zon, Ministerio de Economía y Competitividad (MINECO), Universidad Complutense de Madrid, Depto. de Mineralogía y Petrología, Fac. de Ciencias Geológicas, TRUE, pub

Three distinct S-type peraluminous granitoid types have been identified within the Variscan Montes de Toledo batholith, located in the Central Iberian Zone (SW European Variscides): type-1, extremely high peraluminous restite-rich granitoids; type-2, highly peraluminous restite-bearing granitoids; and type-3, moderately peraluminous granitoids with mafic microgranular enclaves. Type-1 and type-2 granitoids are restricted to the western part of the batholith, whereas type-3 granites are mostly restricted to the eastern segment. There is a sequential youngering of emplacement age from type-1 (late-tectonic) to type-2 and type-3 granitoids (post-tectonic), extending the timing of the batholith formation for about 19 Ma between 316 and 297 Ma. Although the degree of peraluminousity of the different series could be related to different partial melting conditions or to the variable entrainment of restitic components (including the peritectic mineral assemblage of the melting reactions), whole-rock geochemical signatures and isotope zircon composition of the peraluminous granitoid types suggest contribution of different crustal sources. There is no evidence for the direct mantle-derived material contribution in the genesis of these peraluminous melts. Type-1 and type-2 granitoids contain mostly Archean to Neoproterozoic inherited zircons, whereas type-3 granites show preferentially Neoproterozoic (up to late Cryogenian) and Ordovician inheritance. The wide range of initial Hf isotope composition, ranging to highly radiogenic values (ƐHf up to + 10), of Neoproterozoic zircon inheritances in type-1 and type-2 granitoids suggests derivation from heterogeneous Neoproterozoic metasedimentary sources composed of both juveline and recycled crustal materials, similar in composition to the host Schist–Greywacke Complex metasediments. Trace-element modelling clearly suggests the involvement of metasediments similar to those mentioned from the southern part of the Central Iberian Zon, Ministerio de Economía y Competitividad (MINECO), Universidad Complutense de Madrid, Depto. de Mineralogía y Petrología, Fac. de Ciencias Geológicas, TRUE, pub

Neoproterozoic metasedimentary units from central Spain and the northern Central Iberian Zone (CIZ) show distinctive geochemical signatures with respect to the Schist-Greywacke Complex, which is dominant in the southwestern part of the CIZ. Significant differences occur in major and trace element composition and initial Nd isotope ratios, which cannot be explained in terms of metamorphic grade and/or anatexis in some layers of these metasedimentary sequences. ɛNd540 values from metapelites of central Spain range from −5.6 to −10.4 whereas those from the Schist-Greywacke Complex span a narrower and higher range of −0.8 to −3.1. This difference suggests different source regions. The presence of two contrasting Early Ordovician magmatic belts in both subzones reinforces the idea of different Precambrian basement terranes in the CIZ. These data are crucial for pre-Variscan paleogeographic reconstructions of the westernmost European terranes and for checking the validity of current subdivisions of the Iberian Massif., Ministerio de Economía y Competitividad (MINECO), Universidad Complutense de Madrid, Depto. de Mineralogía y Petrología, Fac. de Ciencias Geológicas, TRUE, pub

Depto. de Mineralogía y Petrología, Fac. de Ciencias Geológicas, TRUE, pub

El pasado 11 y 12 de mayo se celebró el Geolodía 2013 con diferentes actividades, normalmente excursiones abiertas a todo tipo de público, para impulsar la divulgación de la geología, dar a conocer el variado patrimonio geológico y concienciar a la población de la necesidad de protegerlo., Depto. de Mineralogía y Petrología, Fac. de Ciencias Geológicas, TRUE, pub

El pasado 11 y 12 de mayo se celebró el Geolodía 2013 con diferentes actividades, normalmente excursiones abiertas a todo tipo de público, para impulsar la divulgación de la geología, dar a conocer el variado patrimonio geológico y concienciar a la población de la necesidad de protegerlo., Depto. de Mineralogía y Petrología, Fac. de Ciencias Geológicas, TRUE, pub

Depto. de Mineralogía y Petrología, Fac. de Ciencias Geológicas, TRUE, pub

U–Th–Pb monazite dating by electron microprobe has been applied to three peraluminous granitic intrusions of the western Montes de Toledo batholith (MTB). Back scattered electron images of monazite crystals reveal a variety of internal textures: patchy zoning, overgrowths around older cores and unzoned crystals. On the basis of their zoning pattern and chemical composition, two monazite domains can be distinguished: (1) corroded cores and crystals with patchy zoning, exhibiting relatively constant Th/U ratios and broadly older ages, and (2) unzoned grains and monazite rims, with variable Th/U ratios and younger ages. The first monazite group represents inherited domains from metamorphic sources, which accounts for pre-magmatic monazite growth events. Two average ages from Torrico and Belvís de Monroy granites (33318 and 3335 Ma, respectively) relate these cores to a Viséan extensional deformation phase. The second group represents igneous monazites which have provided the following crystallization ages for the host granite: 29811 Ma (Villar del Pedroso), 3036Ma (Torrico) and 3143Ma (Belvís de Monroy). Two main magmatic pulses, the first about 314Ma and the second at the end of the Carboniferous (303–298Ma), might be envisaged in the western MTB. While Belvís de Monroy leucogranite is likely a syn- to late-tectonic intrusion, the Villar del Pedroso and Torrico plutons represent post-tectonic magmas with emplacement ages similar to those of equivalent intrusions from nearby Variscan magmatic sectors., Depto. de Mineralogía y Petrología, Fac. de Ciencias Geológicas, TRUE, pub

U–Th–Pb monazite dating by electron microprobe has been applied to three peraluminous granitic intrusions of the western Montes de Toledo batholith (MTB). Back scattered electron images of monazite crystals reveal a variety of internal textures: patchy zoning, overgrowths around older cores and unzoned crystals. On the basis of their zoning pattern and chemical composition, two monazite domains can be distinguished: (1) corroded cores and crystals with patchy zoning, exhibiting relatively constant Th/U ratios and broadly older ages, and (2) unzoned grains and monazite rims, with variable Th/U ratios and younger ages. The first monazite group represents inherited domains from metamorphic sources, which accounts for pre-magmatic monazite growth events. Two average ages from Torrico and Belvís de Monroy granites (33318 and 3335 Ma, respectively) relate these cores to a Viséan extensional deformation phase. The second group represents igneous monazites which have provided the following crystallization ages for the host granite: 29811 Ma (Villar del Pedroso), 3036Ma (Torrico) and 3143Ma (Belvís de Monroy). Two main magmatic pulses, the first about 314Ma and the second at the end of the Carboniferous (303–298Ma), might be envisaged in the western MTB. While Belvís de Monroy leucogranite is likely a syn- to late-tectonic intrusion, the Villar del Pedroso and Torrico plutons represent post-tectonic magmas with emplacement ages similar to those of equivalent intrusions from nearby Variscan magmatic sectors., Depto. de Mineralogía y Petrología, Fac. de Ciencias Geológicas, TRUE, pub

Ion microprobe U–Pb analyses of zircons from three gabbroic intrusions from the Spanish Central System (SCS) (Talavera, La Solanilla and Navahermosa) yield Variscan ages (300 to 305 Ma) in agreement with recent studies. Only two zircon crystals from La Solanilla massif gave slightly discordant Paleoproterozoic ages (1,848 and 2,010 Ma). Hf isotope data show a relatively large variation with the juvenile end-members showing ɛHfi values as high as +3.6 to +6.9 and +1.5 to +2.9 in the Navahermosa and Talavera gabbros, respectively. These positive ɛHfi values up to +6.9 might represent the composition of the subcontinental mantle which generates these SCS gabbros. This ɛHfi range is clearly below depleted mantle values suggesting the involvement of enriched mantle components on the origin of these Variscan gabbros, and is consistent with previous whole-rock studies. The presence of zircons with negative ɛHfi values suggest variable, but significant, crustal contamination of the gabbros, mainly by mixing with coeval granite magmas. Inherited Paleoproterozoic zircons of La Solanilla gabbros have similar trace element composition (e.g. Th/U ratios), but more evolved Hf-isotope signatures than associated Variscan zircons. Similar inherited ages have been recorded in zircons from coeval Variscan granitoids from the Central Iberian Zone. Granitic rocks have Nd model ages (TDM) predominantly in the range of 1.4 to 1.6 Ga, suggesting a juvenile addition during the Proterozoic. However, Hf crustal model ages of xenocrystic Proterozoic zircons in La Solanilla gabbro indicate the presence of reworked Archean protoliths (TDM2 model ages of 3.0 to 3.2 Ga) incorporated into the hybridized mafic magma., Depto. de Mineralogía y Petrología, Fac. de Ciencias Geológicas, TRUE, pub

Hf-isotope analyses in previously dated zircon crystals from four Variscan granulite-facies rocks from central Iberia have been studied to examine crustal evolution processes. Two samples are from exposed migmatite terranes, the other two are granulite xenoliths from lower crustal levels. Hf model ages show that lower crustal granulites display a bigger contribution of Archean components than exposed highgrade rocks (14% of the zircon population instead of 6%), reinforcing ideas of preservation of ancient crustal material in the lower crust. The distribution of age-Hf isotope data from zircon suggests two juvenile crust formation events in central Iberia: the main one during the Neoproterozoic (540–620 Ma) and a possible second Mesoproterozoic event around 1.0–1.2 Ga. Magmatism appears in the Central Iberian Zone exclusively related to that younger juvenile addition. Hf data of granulite zircons agrees with recent palaeogeographical reconstruction models which present central Iberia as a peri-Gondwanan terrane located between the West African craton and the Arabian shield, far from the Amazonia microplate., Depto. de Mineralogía y Petrología, Fac. de Ciencias Geológicas, TRUE, pub

Hf-isotope analyses in previously dated zircon crystals from four Variscan granulite-facies rocks from central Iberia have been studied to examine crustal evolution processes. Two samples are from exposed migmatite terranes, the other two are granulite xenoliths from lower crustal levels. Hf model ages show that lower crustal granulites display a bigger contribution of Archean components than exposed highgrade rocks (14% of the zircon population instead of 6%), reinforcing ideas of preservation of ancient crustal material in the lower crust. The distribution of age-Hf isotope data from zircon suggests two juvenile crust formation events in central Iberia: the main one during the Neoproterozoic (540–620 Ma) and a possible second Mesoproterozoic event around 1.0–1.2 Ga. Magmatism appears in the Central Iberian Zone exclusively related to that younger juvenile addition. Hf data of granulite zircons agrees with recent palaeogeographical reconstruction models which present central Iberia as a peri-Gondwanan terrane located between the West African craton and the Arabian shield, far from the Amazonia microplate., Depto. de Mineralogía y Petrología, Fac. de Ciencias Geológicas, TRUE, pub

Ion microprobe U–Pb analyses of zircons from three gabbroic intrusions from the Spanish Central System (SCS) (Talavera, La Solanilla and Navahermosa) yield Variscan ages (300 to 305 Ma) in agreement with recent studies. Only two zircon crystals from La Solanilla massif gave slightly discordant Paleoproterozoic ages (1,848 and 2,010 Ma). Hf isotope data show a relatively large variation with the juvenile end-members showing ɛHfi values as high as +3.6 to +6.9 and +1.5 to +2.9 in the Navahermosa and Talavera gabbros, respectively. These positive ɛHfi values up to +6.9 might represent the composition of the subcontinental mantle which generates these SCS gabbros. This ɛHfi range is clearly below depleted mantle values suggesting the involvement of enriched mantle components on the origin of these Variscan gabbros, and is consistent with previous whole-rock studies. The presence of zircons with negative ɛHfi values suggest variable, but significant, crustal contamination of the gabbros, mainly by mixing with coeval granite magmas. Inherited Paleoproterozoic zircons of La Solanilla gabbros have similar trace element composition (e.g. Th/U ratios), but more evolved Hf-isotope signatures than associated Variscan zircons. Similar inherited ages have been recorded in zircons from coeval Variscan granitoids from the Central Iberian Zone. Granitic rocks have Nd model ages (TDM) predominantly in the range of 1.4 to 1.6 Ga, suggesting a juvenile addition during the Proterozoic. However, Hf crustal model ages of xenocrystic Proterozoic zircons in La Solanilla gabbro indicate the presence of reworked Archean protoliths (TDM2 model ages of 3.0 to 3.2 Ga) incorporated into the hybridized mafic magma., Depto. de Mineralogía y Petrología, Fac. de Ciencias Geológicas, TRUE, pub

Received: 1 July 2010 / Accepted: 9 December 2010 / Published online: 31 December 2010 © Springer-Verlag 2010 e-mail C. Villaseca: granito@geo.ucm.es, Ion microprobe U–Pb analyses of zircons from three gabbroic intrusions from the Spanish Central System (SCS) (Talavera, La Solanilla and Navahermosa) yield Variscan ages (300 to 305 Ma) in agreement with recent studies. Only two zircon crystals from La Solanilla massif gave slightly discordant Paleoproterozoic ages (1,848 and 2,010 Ma). Hf isotope data show a relatively large variation with the juvenile end-members showing ɛHfi values as high as +3.6 to +6.9 and +1.5 to +2.9 in the Navahermosa and Talavera gabbros, respectively. These positive ɛHfi values up to +6.9 might represent the composition of the subcontinental mantle which generates these SCS gabbros. This ɛHfi range is clearly below depleted mantle values suggesting the involvement of enriched mantle components on the origin of these Variscan gabbros, and is consistent with previous whole-rock studies. The presence of zircons with negative ɛHfi values suggest variable, but significant, crustal contamination of the gabbros, mainly by mixing with coeval granite magmas. Inherited Paleoproterozoic zircons of La Solanilla gabbros have similar trace element composition (e.g. Th/U ratios), but more evolved Hf-isotope signatures than associated Variscan zircons. Similar inherited ages have been recorded in zircons from coeval Variscan granitoids from the Central Iberian Zone. Granitic rocks have Nd model ages (TDM) predominantly in the range of 1.4 to 1.6 Ga, suggesting a juvenile addition during the Proterozoic. However, Hf crustal model ages of xenocrystic Proterozoic zircons in La Solanilla gabbro indicate the presence of reworked Archean protoliths (TDM2 model ages of 3.0 to 3.2 Ga) incorporated into the hybridized mafic magma., Ministerio de Ciencia y Tecnología (España), Universidad Complutense de Madrid, Depto. de Mineralogía y Petrología, Fac. de Ciencias Geológicas, TRUE, pub

For hundreds of years, two types of granite (Zarzalejo and Alpedrete) from the Madrid region, Spain, have been extensively used as building stones. Fresh specimens of both stone types have been sampled from their respective quarries and subjected to sodium sulphate salt crystallization test (SCT). The resulting physical and chemical weathering patterns have been characterized by polarized light optical and environmental scanning electron microscopy. Water absorption under vacuum conditions and mercury intrusion porosimetry techniques were used to determine the pre- and post-SCT porosity and pore size distribution. The following non-destructive techniques were performed to assess stone durability and decay: ultrasound velocity (US) and surface roughness determination (SR) of intra- and inter-granular quartz, feldspar and biotite minerals at the centre as well as at the corners and edges of specimen surfaces. Before the SCT, US values were lower and SR values higher in Zarzalejo (ZAR) than Alpedrete (ALP) granite. After SCT, the US values declined while SR rose in both types of granites, with greater average differences in ZAR than ALP for both parameters. Feldspar and biotite and their inter-granular contacts were found to be the weakest and therefore the most decay-prone areas of the stone. The initial SR parameters were generally higher and rose more steeply after SCT at the corners and around the edges of the specimens. While behaviour was found to be similar in the two types of granite, variations were greater in ZAR, the less durable and more decay-prone of the two. Surface roughness measurement of mineral grains in granite stones is a very useful, in situ, non-destructive technique for quantifying salt crystallization-mediated physical and chemical weathering. The resulting quantification of decay and of related durability provides insight into the future behaviour of this type of stone, commonly used in historic buildings., Depto. de Mineralogía y Petrología, Fac. de Ciencias Geológicas, TRUE, pub

Depto. de Mineralogía y Petrología, Fac. de Ciencias Geológicas, TRUE, pub

Depto. de Mineralogía y Petrología, Fac. de Ciencias Geológicas, TRUE, pub

Received: 1 July 2010 / Accepted: 9 December 2010 / Published online: 31 December 2010 © Springer-Verlag 2010 e-mail C. Villaseca: granito@geo.ucm.es, Ion microprobe U–Pb analyses of zircons from three gabbroic intrusions from the Spanish Central System (SCS) (Talavera, La Solanilla and Navahermosa) yield Variscan ages (300 to 305 Ma) in agreement with recent studies. Only two zircon crystals from La Solanilla massif gave slightly discordant Paleoproterozoic ages (1,848 and 2,010 Ma). Hf isotope data show a relatively large variation with the juvenile end-members showing ɛHfi values as high as +3.6 to +6.9 and +1.5 to +2.9 in the Navahermosa and Talavera gabbros, respectively. These positive ɛHfi values up to +6.9 might represent the composition of the subcontinental mantle which generates these SCS gabbros. This ɛHfi range is clearly below depleted mantle values suggesting the involvement of enriched mantle components on the origin of these Variscan gabbros, and is consistent with previous whole-rock studies. The presence of zircons with negative ɛHfi values suggest variable, but significant, crustal contamination of the gabbros, mainly by mixing with coeval granite magmas. Inherited Paleoproterozoic zircons of La Solanilla gabbros have similar trace element composition (e.g. Th/U ratios), but more evolved Hf-isotope signatures than associated Variscan zircons. Similar inherited ages have been recorded in zircons from coeval Variscan granitoids from the Central Iberian Zone. Granitic rocks have Nd model ages (TDM) predominantly in the range of 1.4 to 1.6 Ga, suggesting a juvenile addition during the Proterozoic. However, Hf crustal model ages of xenocrystic Proterozoic zircons in La Solanilla gabbro indicate the presence of reworked Archean protoliths (TDM2 model ages of 3.0 to 3.2 Ga) incorporated into the hybridized mafic magma., Ministerio de Ciencia y Tecnología (España), Universidad Complutense de Madrid, Depto. de Mineralogía y Petrología, Fac. de Ciencias Geológicas, TRUE, pub

For hundreds of years, two types of granite (Zarzalejo and Alpedrete) from the Madrid region, Spain, have been extensively used as building stones. Fresh specimens of both stone types have been sampled from their respective quarries and subjected to sodium sulphate salt crystallization test (SCT). The resulting physical and chemical weathering patterns have been characterized by polarized light optical and environmental scanning electron microscopy. Water absorption under vacuum conditions and mercury intrusion porosimetry techniques were used to determine the pre- and post-SCT porosity and pore size distribution. The following non-destructive techniques were performed to assess stone durability and decay: ultrasound velocity (US) and surface roughness determination (SR) of intra- and inter-granular quartz, feldspar and biotite minerals at the centre as well as at the corners and edges of specimen surfaces. Before the SCT, US values were lower and SR values higher in Zarzalejo (ZAR) than Alpedrete (ALP) granite. After SCT, the US values declined while SR rose in both types of granites, with greater average differences in ZAR than ALP for both parameters. Feldspar and biotite and their inter-granular contacts were found to be the weakest and therefore the most decay-prone areas of the stone. The initial SR parameters were generally higher and rose more steeply after SCT at the corners and around the edges of the specimens. While behaviour was found to be similar in the two types of granite, variations were greater in ZAR, the less durable and more decay-prone of the two. Surface roughness measurement of mineral grains in granite stones is a very useful, in situ, non-destructive technique for quantifying salt crystallization-mediated physical and chemical weathering. The resulting quantification of decay and of related durability provides insight into the future behaviour of this type of stone, commonly used in historic buildings., Depto. de Mineralogía y Petrología, Fac. de Ciencias Geológicas, TRUE, pub

Depto. de Mineralogía y Petrología, Fac. de Ciencias Geológicas, TRUE, pub

Depto. de Mineralogía y Petrología, Fac. de Ciencias Geológicas, TRUE, pub

The phenomenon of deficient electron microprobe analyses, with sums of analyzed constituents often below 95 wt%, is assigned to the analysis of altered, porous minerals. With the example of three zircon populations we show that low totals are related to textural features (i.e., numerous pores of tens to hundreds of nanometers size) as well as to the chemical composition (i.e., water content well within the wt% range, which may affect partial sample degradation under the electron beam). The formation of the spongy texture is explained by the alteration of a previously radiation-damaged and, thus, volumeexpanded material in a fluid-driven replacement reaction. The smaller volume of the reaction product (crystalline, non volume- expanded zircon) accounts for the formation of numerous voids and pores, which are perfect candidates for the incorporation of water. The alteration has also resulted in uptake of non-formula elements such as Al, P, Ca, Fe, Y, and REEs whereas Si and Zr are depleted. In one case, strong uptake of non-radiogenic Pb in altered zircon was observed. Because porous, low-total zircon has formed in secondary alteration process, its occurrence can be considered as an indicator of a secondary alteration history of the host rock. Low-total zircon is easily recognized by very low electron back-scatter intensities, which are closely related to the two main causes of the analytical shortfall (i.e., water content and porosity) and often lowered furthermore by the presence of light non-formula elements (especially P and Fe) up to the wt% range., Depto. de Mineralogía y Petrología, Fac. de Ciencias Geológicas, TRUE, pub

The original publication is available at www.springerlink.com, Depto. de Mineralogía y Petrología, Fac. de Ciencias Geológicas, TRUE, pub

Depto. de Mineralogía y Petrología, Fac. de Ciencias Geológicas, TRUE, pub

Depto. de Mineralogía y Petrología, Fac. de Ciencias Geológicas, TRUE, pub

The phenomenon of deficient electron microprobe analyses, with sums of analyzed constituents often below 95 wt%, is assigned to the analysis of altered, porous minerals. With the example of three zircon populations we show that low totals are related to textural features (i.e., numerous pores of tens to hundreds of nanometers size) as well as to the chemical composition (i.e., water content well within the wt% range, which may affect partial sample degradation under the electron beam). The formation of the spongy texture is explained by the alteration of a previously radiation-damaged and, thus, volumeexpanded material in a fluid-driven replacement reaction. The smaller volume of the reaction product (crystalline, non volume- expanded zircon) accounts for the formation of numerous voids and pores, which are perfect candidates for the incorporation of water. The alteration has also resulted in uptake of non-formula elements such as Al, P, Ca, Fe, Y, and REEs whereas Si and Zr are depleted. In one case, strong uptake of non-radiogenic Pb in altered zircon was observed. Because porous, low-total zircon has formed in secondary alteration process, its occurrence can be considered as an indicator of a secondary alteration history of the host rock. Low-total zircon is easily recognized by very low electron back-scatter intensities, which are closely related to the two main causes of the analytical shortfall (i.e., water content and porosity) and often lowered furthermore by the presence of light non-formula elements (especially P and Fe) up to the wt% range., Depto. de Mineralogía y Petrología, Fac. de Ciencias Geológicas, TRUE, pub

Depto. de Mineralogía y Petrología, Fac. de Ciencias Geológicas, TRUE, pub