Mineral chemistry of late Variscan gabbros from central Spain: constraints on crystallisation processes and nature of the parental magmas

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Petrología y geoquímica de las tonalitas de Villarejo de Montalbán

[ES] Las tonalitas de Villarejo de Montalbán son rocas ricas en biotita en las que se observan segregados más félsicos con abundante titanita. Los datos geoquímicos e isotópicos de roca total ((87Sr/86Sr)300 = 0,7084-0,7089; εNd = -4,79, -4,80) sugieren que el magma tonalítico se formó por fusión de rocas metaígneas de composición básica/intermedia (anfibolitas o granulitas). A su vez, los segregados félsicos parecen haberse formado por acumulación del magma residual diferenciado a partir de una matriz formada sobre todo por plagioclasa y biotita. Las condiciones de cristalización estimadas por geotermobarometría del anfíbol indican temperaturas de 890- 920ºC, y presiones de 1,3-2,4 kbar, las cuales implican niveles aproximados de emplazamiento cercanos a los 5-10 km de profundidad. [EN] The tonalites of Villarejo de Montalbán are biotite-rich rocks showing felsic segregates with abundant titanite. Whole-rock geochemical and isotopic data ((87Sr/86Sr)300 = 0.7084-0.7089; εNd = -4.79, -4.80) suggest that the tonalitic magma was formed by melting of metaigneous rocks of basic/intermediate composition (amphibolites or granulites). At the same time, the felsic segregates seem to have formed through the accumulation of a differentiated residual magma after crystal fractionation of plagioclase and biotite. Crystallization conditions estimated according to amphibole geothermobarometry indicate temperatures between 890 and 920ºC, and pressures in the range 1.3-2.4 kbar, which is in accordance with an approximate emplacement level close to 5-10 km deep.Peer Reviewe

Geothermobarometric applications of trace-element contents in granulite minerals: Zr-in rutile and HREE-in garnet from lower crustal felsic xenoliths of the Spanish Central System

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 xenolith

Alkaline monzo-syenitic porphyries from the Spanish Central System: relationship with the accompaning lamprophyres

The alkaline monzo-syenitic porphyries from the Spanish Central System (SCS) show a heterogeneous composition ranging from basic to acid terms which give rise to major and trace element compositional trends in accordance with fractional crystallization of amphibole, plagioclase, biotite, alkaline feldspar, Timagnetite and apatite. The whole-rock geochemistry of the basic porphyries shows clear similarities with respect to the SCS isotopically enriched alkaline lamprophyres, indicating that a genetic link between both groups of dykes might exist. This relationship would probably represent an origin of the monzo-syenitic porphyries after differentiation of parental lamprophyric magmas due to fractional crystallizatio

Lung cancer mortality in towns near paper, pulp and board industries in Spain: a point source pollution study

<p>Abstract</p> <p>Background</p> <p>This study sought to ascertain whether there might be excess lung cancer mortality among the population residing in the vicinity of Spanish paper and board industries which report their emissions to the European Pollutant Emission Register (EPER).</p> <p>Methods</p> <p>This was an ecological study that modelled the Standardised Mortality Ratio (SMR) for lung cancer in 8073 Spanish towns over the period 1994–2003. Population exposure to industrial pollution was estimated on the basis of distance from town of residence to pollution source. An exploratory, near-versus-far analysis was conducted, using mixed Poisson regression models and an analysis of the effect of municipal proximity within a 50-kilometre radius of each of the 18 installations.</p> <p>Results</p> <p>Results varied for the different facilities. In two instances there was an increasing mortality gradient with proximity to the installation, though this was exclusively observed among men.</p> <p>Conclusion</p> <p>The study of cancer mortality in areas surrounding pollutant foci is a useful tool for environmental surveillance, and serves to highlight areas of interest susceptible to being investigated by ad hoc studies. Despite present limitations, recognition is therefore due to the advance represented by publication of the EPER and the study of pollutant foci.</p

Petrology and geochemistry of tonalites fromVillarejo de Montalbán (Toledo)

The tonalites of Villarejo de Montalbán are biotite-rich rocks showing felsic segregates with abundant titanite. Whole-rock geochemical and isotopic data ((87Sr/86Sr)300 = 0.7084-0.7089; εNd = -4.79, -4.80) suggest that the tonalitic magma was formed by melting of metaigneous rocks of basic/intermediate composition (amphibolites or granulites). At the same time, the felsic segregates seem to have formed through the accumulation of a differentiated residual magma after crystal fractionation of plagioclase and biotite. Crystallization conditions estimated according to amphibole geothermobarometry indicate temperatures between 890 and 920ºC, and pressures in the range 1.3-2.4 kbar, which is in accordance with an approximate emplacement level close to 5-10 km deepLas tonalitas de Villarejo de Montalbán son rocas ricas en biotita en las que se observan segregados más félsicos con abundante titanita. Los datos geoquímicos e isotópicos de roca total ((87Sr/86Sr)300 = 0,7084-0,7089; εNd = -4,79, -4,80) sugieren que el magma tonalítico se formó por fusión de rocas metaígneas de composición básica/intermedia (anfibolitas o granulitas). A su vez, los segregados félsicos parecen haberse formado por acumulación del magma residual diferenciado a partir de una matriz formada sobre todo por plagioclasa y biotita. Las condiciones de cristalización estimadas por geotermobarometría del anfíbol indican temperaturas de 890- 920ºC, y presiones de 1,3-2,4 kbar, las cuales implican niveles aproximados de emplazamiento cercanos a los 5-10 km de profundida

The granulitic residue of the Variscan granites of central Iberia: challenges to restite unmixing and peritectic entrainment models

Trabajo presentado en la European Geosciences Union General Assembly, celebrada en Viena (Austria), del 8 al 13 de abril de 2018The origin of granitic magmas in a crustal recycling context implies that deep-seated residual granulites and shallower granite batholiths have to be consanguineous. Moreover, the heat necessary to achieve granulite-facies metamorphism, driving extensive melting, might be mostly generated by thickening of fertile lithotypes rich in heatproducing elements, which is only possible in intracontinental collisional orogens. The Variscan Spanish Central System (SCS) batholith, in central Iberia, is a useful example of the above background. It is mainly composed of peraluminous felsic granites and it has been related to a suite of granulite xenoliths of ultra high temperature (UHT), carried by post-Variscan ultrabasic alkaline lamprophyres. These granulites indicate that the SCS lower crust is composed by peraluminous meta-igneous felsic types (90-95 %), with subordinated pelitic (7 %) and pyroxene-bearing mafic (≤1 %) varieties. A set of arguments points to the granulitic SCS lower crust being the restitic counterpart of the outcropping granitic batholith. Major and trace element composition indicates that UHT granulites have high MgO, FeOt, TiO2, Cr, Ni and low SiO2, Na2O, K2O, Rb, Th, U relative to the average composition of pelitic and metaigneous country rocks, consistent with a more mafic, dehydrated and residual composition. Granulite-facies rocks from outcropping migmatite terranes do not show such an extreme residual composition and give rise to anatectic leucogranites and minor restite-rich granitoids with a dissimilar composition with respect to the large granite batholith. Similarities in the isotopic composition (Sr-Nd-O-Pb-Hf), the U-Pb zircon ages (305-285 Ma) and inherited zircon age populations between UHT granulites and Variscan granites are robust arguments supporting a source-extracted melt relationship. Moreover, the high temperatures (Ti-in zircon) determined in these Variscan granites (mostly 800-865 ºC) are consistent with an adiabatic ascent (∼100 ºC decrease) from a deep melting area (900-1100 ºC and ∼10 kbar conditions) to epizonal levels (∼3 kbar). Granulite conditions in the SCS lower crust were reached after the thickening and collapse of the Iberian Variscan belt, involving widespread partial melting. The scarcity of basic magmatism and related mafic granulites suggests a minor role of mantle-derived underplating. The Variscan orogen in central Iberia outstands for an apparently nil crustal growth. The elevated radioactive heat production of a fertile thickened crust makes unnecessary a mafic thermal input to achieve UHT conditions at the base of the crust. Consequently, the Variscan granites resulted from reworking of Neoproterozoic to Cambrian metasedimentary and Cadomian meta-igneous rocks within the lower crust. The study of deep-seated granulites helps to discuss the role played by the source in the chemical variation observed in granites (e.g., peritectic assemblage entrainment, PAE). The studied UHT granite residues add some troubles to PAE models: most REE, Y and Zr are hosted in common granulite minerals (plagioclase, K-feldspar, garnet, rutile), accessories are almost exhausted during partial melting (Th-U-depleted granulites), and residual plagioclase is around An32Or18Ab50. Mineral chemistry helps to distinguish between residual and magmatic crystals in peraluminous granites and indicates that the SCS hot S-type granites are not in accordance with PAE modelling.Peer reviewe

Zr-rich rutile included in garnet from lower crustal granulite xenoliths of the Spanish Central System: geodynamic implications

Two petrographic types of rutile are observed in the peraluminous felsic meta-igneous granulites, the most common type of the lower crustal xenolith suite of the Spanish Central System (SCS). Rutile-1 (Rt-1) corresponds to small crystals (mainly < 80 mm) only preserved as micro-inclusions within garnet, whereas rutile-2 (Rt-2) is commonly found as big idiomorfic crystals forming the granulite granoblastic matrix. Chemical analyses by EMP show a higher Zr content in Rt-1 (up to 7800 ppm) than in Rt-2 (up to 5200 ppm) of the same granulite. Applying Zr-in-rutile thermometry, Rt-1 gives 50-60 ºC higher for rutile crystallization (950-1015 ºC) when compared to Rt-2 thermometry (940-955 ºC). These ultra-high temperatures (UHT) are likely attained at Moho depths without external heat sources (e.g. mantle input) as supported by the high heat production estimated for the crustal section of the SCS. The granulitegranite petrogenetic link suggests that these HT-UHT granulites were generated by intra-crustal reworking during Hercynian continental thickenin

Zircon Lu-Hf isotopic composition of Ordovician metabasites from the Spanish Central System

La composición isotópica Lu-Hf de los circones de las metabasitas ordoví-cicas del Sistema Central Español proporciona valores entre ligeramente ymoderadamente empobrecidos y señala diferencias entre el sector de Tenzuelay los de Revenga-El Caloco. Los metagabros de estos últimos sectores poseenun ligero desajuste entre los valores de εHf y εNd (εHf por encima de la ali-neación del manto), así como edades modelo de Hf y Nd mayores. Estacaracterística probablemente implica que cierto reciclaje de sedimentos pelági-cos se produjo dentro del área fuente mantélica de las metabasitas deRevenga-El Caloco durante el ciclo orogénico Cadomiense. La semejanza iso-tópica respecto a materiales básicos variscos parece indicar que el manto bajoel Sistema Central Español no se rejuveneció ni experimentó cambios impor-tantes desde el Ordovícico hasta el final de la orogenia VariscaThe zircon Lu-Hf isotopic composition of the Ordovician metabasitesfrom the Spanish Central System provides slightly to moderately depletedvalues and highlights the existence of significant differences between theTenzuela and Revenga-El Caloco areas. Metagabbros from this latter areashow a subtle decoupling between εHf and εNd (εHf above the mantlearray) as well as older Hf and Nd model ages. This likely implies thatpelagic sediments were recycled in the mantle source of Revenga-ElCaloco metabasites during the Cadomian cycle. The isotopic similitudewith respect to Variscan basic rocks indicates that juvenile componentswere not added to the mantle below the Spanish Central System, whichdid not experience significant modifications from the Ordovician to theend of the Variscan orogen