Papers by Pedro Castiñeiras
In the Órdenes Complex (NW Iberian Massif, Spain) an intermediate pressure (IP) uppermost unit co... more In the Órdenes Complex (NW Iberian Massif, Spain) an intermediate pressure (IP) uppermost unit consists of a thick flyschoid metasedimentary sequence, intruded by large bodies of gabbros and granitoids. Metamorphic conditions in the IP units range between greenschist facies, in the uppermost sectors, and IP granulite facies in the basal part. In the intermediate structural levels of the IP units
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Although the range in low-cost seismometers is usually restricted to local seismology, induced se... more Although the range in low-cost seismometers is usually restricted to local seismology, induced seismology or human activities, our approach is able to record data with sampling rates up to 500 Hz. It can record and analyze data with a resolution of 16-bit, but it can be regulated to reach 24-bit if needed. Data transfer can operate all-day with low power consumption, using around 1-Amp per hour, or even less, depending on the final setup chosen.
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La cantera de Touro (A Coruna) es una explotacion a cielo abierto de la que se extraen anfibolita... more La cantera de Touro (A Coruna) es una explotacion a cielo abierto de la que se extraen anfibolitas y esquistos para su uso como arido de machaqueo. Estos materiales geologicos han sufrido una evolucion metamorfica compleja, lo que dificulta su identificacion y posterior separacion en cantera. Por este motivo, es necesario buscar tecnicas analiticas sencillas de campo y laboratorio que permitan identificar y caracterizar el material en los frentes y evaluar su calidad en relacion a sus posteriores usos en obra. Con este objetivo, se identificaron las variedades litologicas presentes en los frentes de extraccion y se estudio su dureza superficial, porosidad, expresada como la capacidad de absorcion del agua, y velocidad de propagacion de ondas P. A partir de los resultados obtenidos, se concluyo que la textura, tamano de grano, porosidad y dureza superficial, son los mejores indicadores de la calidad de los materiales y se propone un sistema de sectorizacion de los frentes de explotac...
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Solid Earth
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Minerals
A comprehensive study of the serpentinite and associated veins belonging to the Frido Unit in the... more A comprehensive study of the serpentinite and associated veins belonging to the Frido Unit in the Pollino Massif (southern Italy) is presented here with the aim to provide new constraints about the hydrothermal system hosted by the accretionary wedge of the southern Apennines. The studied serpentinites are from two different sites: Fosso Arcangelo and Pietrapica. In both sites, the rocks show mylonitic-cataclastic structures and pseudomorphic and patch textures and are traversing by pervasive carbonate and quartz-carbonate veins. The mineralogical assemblage of serpentinites consists of serpentine group minerals (with a predominance of lizardite), amphiboles, pyroxene, chlorite, titanite, magnetite, and talc. In some samples, hydro-garnet was also detected and documented here for the first time. As for cutting veins, different mineralogical compositions were observed in the two sites: calcite characterizes the veins from Fosso Arcangelo, whereas quartz and dolomite are the principal...
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Rendiconti Online della Società Geologica Italiana
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Lithos
New data on the geochemistry and geochronology of different felsic gneisses and metabasites from ... more New data on the geochemistry and geochronology of different felsic gneisses and metabasites from the Variscan massifs of Eastern Pyrenees have allowed us to shed some light on the Ordovician magmat ...
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Solid Earth, 2016
High-grade, highly deformed gneisses crop out continuously along the Masanteo peninsula and const... more High-grade, highly deformed gneisses crop out continuously along the Masanteo peninsula and constitute the upper part of the lower crustal section in the Cabo Ortegal nappe (NW Spain). The rock sequence formed by migmatitic quartzo-feldspathic (qz-fsp) gneisses and mafic rocks records the early Ordovician (ca. 480–488 Ma) injection of felsic dioritic/granodioritic dykes at the base of the qz-fsp gneisses, and Devonian eclogitization (ca. 390.4 ± 1.2 Ma), prior to its exhumation. A SE-vergent ductile thrust constitutes the base of quartzo-feldspathic gneissic unit, incorporating mafic eclogite blocks within migmatitic gneisses. A NW-vergent detachment displaced metasedimentary qz-fsp gneisses over the migmatites. A difference in metamorphic pressure of ca. 0.5 GPa is estimated between both gneissic units. The tectono-metamorphic relationships of the basal ductile thrust and the normal detachment bounding the top of the migmatites indicate that both discrete mechanical contacts were a...
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The first LA-ICP-MS U–Pb detrital zircon ages from quartzites located below (three samples) and a... more The first LA-ICP-MS U–Pb detrital zircon ages from quartzites located below (three samples) and above (one sample) the Upper Ordovician unconformity in the Central Pyrenees (the Rabassa Dome, Andorra) were investigated. The maximum depositional age for the Jújols Group, below the unconformity, based on the youngest detrital zircon population, is around 475 Ma (Early Ordovician), whereas for the Bar Quartzite Fm., above the unconformity, the presence of only two zircons of 442 and 443 Ma precludes obtaining a precise maximum sed-imentation age. A time gap of ~20 million years for the Upper Ordovician unconformity in the Pyrenees can be proposed, similar to that of the Sardic unconformity in Sardinia. The similar age patterns obtained on both sides of the Upper Ordovician unconformity suggest that there was no change in the source area of these series, while the absence of a Middle Ordovician age population may be due to a lack of sedimentation at that time. The four study samples present very similar U–Pb age patterns: the main age populations correspond to Neoproterozoic (Ediacarian–Cryogenian, ca. 550–750 Ma); Grenvillian (Tonian–Stenian, ca. 850–1100 Ma); Paleoproterozoic (Orosirian, ca.1900–2100 Ma) and Neoarchean (ca. 2500–2650 Ma). The similarity with the Sardinian age distribution suggests that these two terranes could share the same source area and that they were paleogeographically close in Ordovician times in front of the Arabian–Nubian Shield.
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New geochronological data from the Canigó massif (Eastern Pyrenees) using U–Pb SIMS on zircon pro... more New geochronological data from the Canigó massif (Eastern Pyrenees) using U–Pb SIMS on zircon provide evidence of the existence of a Late Ordovician (456–446 Ma) plutonic event that emplaced granitic and dioritic bodies into a Late Neoproterozoic–Early Paleozoic metasedimentary series. These are the first geochronological data documenting this magmatic episode in the Pyrenees, which is coeval with synsedimentary volcanism and normal fault development in rocks of the Upper Ordovician. This Late Ordovician magmatic event postdates a ?Middle Ordovician compressional episode recorded in the pre-Upper Ordovician sequence, and is distinct from an Early Ordovician magmatic event that gave rise to the protoliths of large gneissic bodies cropping out in the Pyrenees. This evolution argues against a continuous extensional regime related to the opening of the Rheic or the Rheic and Paleotethys oceans in this segment of the Northern Gondwana margin during the Ordovician and Silurian.
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New geochronological data from low-to medium-grade metamorphic areas of the Eastern Pyrenees (Can... more New geochronological data from low-to medium-grade metamorphic areas of the Eastern Pyrenees (Canigó, Roc de Frausa and Cap de Creus massifs) confirm the presence of two significant pre-Variscan igneous events: Ediacaran–Early Cambrian and Early Ordovician. The Ediacaran–Early Cambrian (580–540 Ma) magmatism is characterized by metavolcanic plagioclasic gneisses (metatuffs) coeval with sedimentation and by sheets of granitic orthogneisses emplaced in the lower part of the metasedimentary series. In the Canigó and Roc de Frausa massifs, the metatuffs are spatially associated with metabasites. Both lithologies occur as massive layers of lava flows, discontinuous lense-shaped, subvolcanic, gabbroic bodies or volcanoclastic tuffs interbedded in the lower and middle part of the pre-Upper Ordovician metasedimentary succession. This magmatism is bimodal and has a tholeiitic and calc-alkaline affinity. The granitic orthogneisses represent thick laminar intrusions of subaluminous and aluminous composition. Early Ordovician (475–460 Ma) magmatism is represented by laccoliths of aluminous granitic orthogneisses emplaced in the middle part of the pre-Upper Ordovician succession. These geochronological data reveal the existence of an Ediacaran metasedimentary sequence and Cadomian magmatism in the Pyrenees and allow their correlation along the Eastern Pyrenean massifs. The data also show ages ranging from Neoproterozoic to Early Ordovician of the large bodies of granitic orthogneisses that intruded into the series at different levels. Both events represent the final stages of the Cadomian orogeny and its transition to the Variscan cycle in the Eastern Pyrenees. A Cambrian rifting event linking both cycles has not been identified in the Pyrenees to date. Our findings provide a better fit for the pre-Variscan sequences of the Pyrenees with those of the Iberian Massif and allow their comparison with other pre-Variscan massifs in Europe.
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Petrogénesis del magmatismo Ordovícico en Pirineos (macizos de Albera y Canigó) basada en la comp... more Petrogénesis del magmatismo Ordovícico en Pirineos (macizos de Albera y Canigó) basada en la composición de elementos menores y traza en circón Abstract: Zircon composition was tested as a tracer of petrogenetic processes in a set of metaigneous rocks from two pre-Ordovician massifs in the Pyrenees, Canigó and Albera. Two groups were differentiated after analyzing a number of elements in zircon: a) Casemí gneiss and the Marialles amphibolite, and b) subvolcanic metaporphyries and Cadí and Sureda orthogneisses. The anomalous trend of the first group data in the Th/U versus Hf plot suggests a mantle involvement in the origin of these rocks and the participation of fractional crystallization during their evolution. Zircon of the metaporphyries and Cadí and Sureda orthogneisses exhibit similar characteristics despite a difference in age, which suggest that this mineral grew in a melt formed by anatexis of a continental crust, with stable plagioclase. These petrogenetic data are consistent with the previously studied whole-rock geochemistry and Sr-Nd isotopes and confirm the use of zircon as a marker of petrogenetic processes in preference to a lithological tracer. Resumen: Se ha puesto a prueba la composición del circón como trazador de procesos petrogenéticos en un conjuto de rocas metaígneas de dos macizos pre-Ordovícicos en Pirineos, Canigó y Albera. Después de analizar una serie de elementos en el circón se han distinguido dos grupos: a) gneiss de Casemí y anfibolita de Marialles, y b) metapórfidos subvolcánicos y ortogneisses de Cadí y Sureda. La pauta anómala de los datos del primer grupo en el gráfico Th/U frente a Hf sugiere una implicación del manto en el origen de estas rocas y la participación de cristalización fraccionada durante su evolución. Los circones de las rocas del segundo grupo tienen características similares, a pesar de la diferencia de edad, que sugieren que este mineral creció en un fundido formado por fusión parcial de una corteza continental con plagioclasa estable. Estos datos petrogenéticos son consistentes con la geoquímica de roca total y los isótopos de Sr y Nd estudiados previamente y confirman el uso de circón como marcador de procesos petrogenéticos en vez de trazador litológico. Palabras clave: Pirineos, magmatismo Ordovícico, contenido en REE del circón, SHRIMP.
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Papers by Pedro Castiñeiras