63 research outputs found
Ultra High Resolution Transmission Electron Microscopy of Matrix Mineral Grains in CM Chondrites: Preaccretionary or Parent Body Aqueous Processing?
CM chondrites are highly hydrated
meteorites associated with a parent asteroid that has
experienced significant aqueous processing. The meteoritic
evidence indicates that these non-differentiated
asteroids are formed by fine-grained minerals embedded
in a nanometric matrix that preserves chemical
clues of the forming environment. So far there are two
hypothesis to explain the presence of hydrated minerals
in the content of CM chondrites: one is based on textural
features in chondrule-rim boundaries [1-3], and
the other ‘preaccretionary’ hypothesis proposes the
incorporation of hydrated phases from the protoplanetary
disk [4-6]. The highly porous structure of these
chondrites is inherited from the diverse materials present
in the protoplanetary disk environment. These
bodies were presumably formed by low relative velocity
encounters that led to the accretion of silicate-rich
chondrules, refractory Ca- and Al-rich inclusions
(CAIs), metal grains, and the fine-grained materials
forming the matrix. Owing to the presence of significant
terrestrial water in meteorite finds [7], here we
have focused on two CM chondrite falls with minimal
terrestrial processing: Murchison and Cold Bokkeveld.
Anhydrous carbonaceous chondrite matrices are usually
represented by highly chemically unequilibrated
samples that contain distinguishable stellar grains.
Other chondrites have experienced hydration and
chemical homogeneization that reveal parent body
processes. We have studied CM chondrites because
these meteorites have experienced variable hydration
levels [8-10]. It is important to study the textural effects
of aqueous alteration in the main minerals to
decipher which steps and environments promote bulk
chemistry changes, and create the distinctive alteration
products. It is thought that aqueous alteration has particularly
played a key role in modifying primordial
bulk chemistry, and homogenizing the isotopic content
of fine-grained matrix materials [7, 11, 12]. Fortunately,
the mineralogy produced by parent-body and terrestrial
aqueous alteration processes is distinctive [5, 11]
Ancient Martian Floods in a Plausible Variable Climatic Environment as Revealed from the Sequential Growth of Allan Hills 84001 Carbonate Globules
No abstract available
Ultra High Resolution Transmission Electron Microscopy of Matrix Mineral Grains in CM Chondrites: Preaccretionary or Parent Body Aqueous Processing?
CM chondrites are highly hydrated
meteorites associated with a parent asteroid that has
experienced significant aqueous processing. The meteoritic
evidence indicates that these non-differentiated
asteroids are formed by fine-grained minerals embedded
in a nanometric matrix that preserves chemical
clues of the forming environment. So far there are two
hypothesis to explain the presence of hydrated minerals
in the content of CM chondrites: one is based on textural
features in chondrule-rim boundaries [1-3], and
the other ‘preaccretionary’ hypothesis proposes the
incorporation of hydrated phases from the protoplanetary
disk [4-6]. The highly porous structure of these
chondrites is inherited from the diverse materials present
in the protoplanetary disk environment. These
bodies were presumably formed by low relative velocity
encounters that led to the accretion of silicate-rich
chondrules, refractory Ca- and Al-rich inclusions
(CAIs), metal grains, and the fine-grained materials
forming the matrix. Owing to the presence of significant
terrestrial water in meteorite finds [7], here we
have focused on two CM chondrite falls with minimal
terrestrial processing: Murchison and Cold Bokkeveld.
Anhydrous carbonaceous chondrite matrices are usually
represented by highly chemically unequilibrated
samples that contain distinguishable stellar grains.
Other chondrites have experienced hydration and
chemical homogeneization that reveal parent body
processes. We have studied CM chondrites because
these meteorites have experienced variable hydration
levels [8-10]. It is important to study the textural effects
of aqueous alteration in the main minerals to
decipher which steps and environments promote bulk
chemistry changes, and create the distinctive alteration
products. It is thought that aqueous alteration has particularly
played a key role in modifying primordial
bulk chemistry, and homogenizing the isotopic content
of fine-grained matrix materials [7, 11, 12]. Fortunately,
the mineralogy produced by parent-body and terrestrial
aqueous alteration processes is distinctive [5, 11]
Estudio de la idoneidad de un nuevo hormigón estructural fabricado con áridos ligeros reforzados con fibra de carbono sinterizados a partir de residuos
The suitability of three new lightweight aggregates containing carbon fiber residues (CAs) as components in structural lightweight concrete has been studied. Prismatic concrete specimens were prepared using these CAs as a coarse fraction. Additional specimens of normal-weight aggregate, commercial lightweight aggregate and mortar were prepared for comparison. The CA-concrete samples (CACs) have yielded compressive strength values between 35 and 55 MPa as well as low density and thermal conductivity results. Furthermore, the CACs have displayed the highest ratios of mechanical strength over density and the thermal conductivity, which means that there is a better balance between their mechanical and physical properties than in the other samples studied. These results indicate that the new CAs could have great potential for use in structural lightweight concrete, also complying with the principles of the Circular Economy.Este estudio pretende comprobar la idoneidad de unos novedosos áridos ligeros sinterizados con residuos de fibra de carbono (CAs) en la fabricación de hormigón ligero estructural. Se prepararon probetas prismáticas de hormigón, utilizando estos CAs como fracción gruesa, comparándose a su vez con probetas fabricadas con un árido convencional, un árido ligero comercial y mortero. Las muestras de hormigón con los áridos CA (en adelante CAC) han dado lugar a valores de resistencia a compresión entre 35 y 55 MPa, así como a resultados bajos de densidad y conductividad térmica, mostrando además las ratios más altas al relacionar estos tres parámetros. Esto indicaría por tanto un mejor equilibrio entre las propiedades mecánicas y físicas que los obtenidos en las otras muestras estudiadas. Estos resultados apuntan a que los nuevos CAs podrían tener un gran potencial para su uso en hormigón ligero estructural, cumpliendo además los principios de la Economía Circular
Ancient Martian Floods in a Plausible Variable Climatic Environment as Revealed from the Sequential Growth of Allan Hills 84001 Carbonate Globules
No abstract available
Primeros datos del magmatismo pérmico medio-superior del SE de la Cordillera Ibérica: caracterización y comparación con magmatismos contemporáneos del Tethys occidental
A multiple basic to intermediate sill is reported for the first time in the south-eastern Iberian Ranges. It is composed of several tabular to irregular levels intercalated within the fluvial sediments of the Alcotas Formation (Middle-Upper Permian). The sill could represent the youngest Paleozoic subvolcanic intrusion in the Iberian Ranges. The igneous rocks are classified as basaltic andesites. They show a subophitic microstructure constituted by plagioclase (An62 – An6), augite (En48Wo44Fs7 –En46Wo39Fs15), pseudomorphosed olivine, minor amounts of oxides (magnetite and ilmenite) and accessory F-apatite. According to the mineralogy and whole-rock composition, their geochemical affinity is transitional from subalkaline to alkaline. Radiometric dating of the sill is not feasible due to its significant alteration. Field criteria, however, suggest an emplacement coeval to the deposition of the Alcotas Formation (Middle-Upper Permian). This hypothesis is supported by the transitional affinity of these rocks, similar to other Middle-Upper Permian magmatisms in the western Tethys, e.g., from the Pyrenees. Taking into account their isotopic signature (εSr: -6.8 to -9.2; εNd: +1.7 to +8.3), an enriched mantle source with the involvement of a HIMU component has been identified. This interpretation is supported by the trace element contents. Some of these HIMU characteristics have been recognised in the Middle-Upper Permian magmatisms of the Central Pyrenees (Anayet Basin) and the High Atlas (Argana Basin). However, none of these source features are shared with other Middle-Upper Permian magmatisms of the western Tethys (Catalonian Coastal Ranges, Corsica-Sardinia and southern France), nor with the Lower Permian magmatism of the Iberian Ranges. These differences support the presence of a heterogeneous mantle in the western Tethys during the Permian.Se describe por primera vez en el sudeste de la Cordillera Ibérica un sill múltiple de carácter básico a intermedio. Está compuesto por varios cuerpos tabulares a irregulares intercalados entre los sedimentos de origen fluvial de la Formación Alcotas (Pérmico Medio-Superior). El sill podría representar la intrusión subvolcánica paleozoica más reciente en la Cordillera Ibérica. Estas rocas subvolcánicas se clasifican como andesitas basálticas. Muestran una textura subofítica constituida por plagioclasa (An62 – An6), augita (En48Wo44Fs7 –En46Wo39Fs15), pseudomorfos de olivino, minerales opacos (magnetita e ilmenita) y F-apatito accesorio. De acuerdo con su composición mineral y de roca total, su afinidad geoquímica es transicional entre subalcalina y alcalina. La datación radiométrica del sill no es posible debido a su elevado grado de alteración. No obstante, los criterios de campo sugieren un emplazamiento contemporáneo con el depósito de la Formación Alcotas (Pérmico Medio-Superior). Esta hipótesis está apoyada por la afinidad transicional de estas rocas, similar a otros episodios magmáticos del Pérmico Medio-Superior en el Tethys occidental, como los que afloran en los Pirineos. Teniendo en cuenta su signatura isotópica (εSr: -6.8 a -9.2; εNd: +1.7 a +8.3), se propone un origen a partir de un manto enriquecido, con la participación de un componente de tipo HIMU. Esta interpretación está apoyada por sus contenidos en elementos traza. Algunas de estas características del protolito han sido reconocidas en los magmatismos del Pérmico Medio-Superior del Pirineo (cuenca del Anayet) y del Alto Atlas (cuenca de Argana), pero no son habituales en otros magmatismos de edad Pérmico Medio-Superior del Tethys occidental (Cadenas Costero Catalanas, Córcega-Cerdeña y Sur de Francia), ni en el magmatismo Pérmico Inferior de la Cordillera Ibérica. Estas diferencias apoyan la presencia de un manto heterogéneo en el Tethys occidental durante el Pérmico
Petrographic and geochemical evidence for multiphase formation of carbonates in the Martian orthopyroxenite Allan Hills 84001
This research has been funded by the Spanish Ministry of Science and Innovation (projects: AYA2011‐26,522, AYA 2015‐67175‐P, CTQ2015‐62,635‐ERC, and CTQ2014‐60,119‐P to which J.M. Trigo‐Rodríguez and C.E. Moyano‐Cambero acknowledge financial support). The UK Science and Technology Facilities Council is also thanked for funding through grants ST/H002960/1, ST/K000942/1, and ST/L002167/1. ICN2 and ICMAB acknowledge support of the Spanish MINECO through the Severo Ochoa Centers of Excellence Program under Grants SEV‐2013‐0295 and SEV‐2015‐0496, respectively. We acknowledge B. Ballesteros and M. Rosado from the ICN2 Electron Microscopy Division, and A. Fernández from the ICTS (National Center of Electronic Microscopy) for the SEM, EDS, and microprobe measurements. We also thank the NASA Meteorite Working Group, and the Johnson Space Center for providing the ALH 84001,82 section. This study was done in the frame of a PhD on Physics at the Autonomous University of Barcelona (UAB) under the direction of J. M. Trigo‐Rodríguez.Peer reviewedPublisher PD
The impact of neos and their fragments recorded from the ground : ongoing research lines of the spanish fireball network
A continuous monitoring of the night sky all over Spain will be completed in 2009. This involves the recording over a
very large surface area of 500,000 km2, but new CCD and video cameras operated by the Spanish Meteor and Fireball
Network (SPMN) allows this target to be achieved. Through the use of these new techniques the SPMN can obtain new
information regarding the dynamical processes that deliver meteorites to the Earth. It transpires that the main asteroid
belt is not the only source of these fireballs, Near Earth Objects (NEOs) and Jupiter Family Comets (JFCs) may also
play a role. To obtain more information in this regard, new efforts are needed to compare the orbits of large meteoroids
reaching the Earth with those of the members of NEO and JFC populations. By numerically integrating their orbits back
in time it may be possible to identify meteoroids delivered by other mechanisms like such as catastrophic disruptions or
collisions
The 2011 October Draconids outburst. I. Orbital elements, meteoroid fluxes and 21P/Giacobini-Zinner delivered mass to Earth
On October 8th, 2011 the Earth crossed the dust trails left by comet
21P/Giacobini-Zinner during its XIX and XX century perihelion approaches with
the comet being close to perihelion. The geometric circumstances of that
encounter were thus favorable to produce a meteor storm, but the trails were
much older than in the 1933 and 1946 historical encounters. As a consequence
the 2011 October Draconid display exhibited several activity peaks with
Zenithal Hourly Rates of about 400 meteors per hour. In fact, if the display
had been not forecasted, it could have passed almost unnoticed as was strongly
attenuated for visual observers due to the Moon. This suggests that most meteor
storms of a similar nature could have passed historically unnoticed under
unfavorable weather and Moon observing conditions. The possibility of obtaining
information on the physical properties of cometary meteoroids penetrating the
atmosphere under low-geocentric velocity encounter circumstances motivated us
to set up a special observing campaign. Added to the Spanish Fireball Network
wide-field all-sky and CCD video monitoring, other high-sensitivity 1/2" black
and white CCD video cameras were attached to modified medium-field lenses for
obtaining high resolution orbital information. The trajectory, radiant, and
orbital data of 16 October Draconid meteors observed at multiple stations are
presented. The results show that the meteors appeared from a geocentric radiant
located at R.A.=263.0+-0.4 deg. and Dec.=+55.3+-0.3 deg. that is in close
agreement with the radiant predicted for the 1873-1894 and the 1900 dust
trails. The estimated mass of material from 21P/Giacobini-Zinner delivered to
Earth during the six-hours outburst was around 950+-150 kg.Comment: Manuscript in press in Monthly Notices of the Royal Astronomical
Society, submitted to MNRAS on November 16th, 2012 Accepted for publication
in MNRAS on April 28th, 2013 Manuscript Pages: 21 Tables: 8 Figures: 4
Manuscript associated: "The 2011 October Draconids outburst. II. Meteoroid
chemical abundances from fireball spectroscopy" by J.M. Madiedo is also in
press in the same journa
Evolución del estuario del rio piedras (Huelva) durante el Holoceno
Trabajo presentado en la XIV Reunión Nacional de Cuaternario, celebrada en Granada (España), del 30 de junio al 2 de julio de 2015This paper presents the preliminary results of a multidisciplinary study of the mixed wave-and-tide dominated estuary of the Piedras River in the mesotidal coast of the Gulf of Cadix. Nineteen hand cores and three mechanical drill cores allowed reconstructing
the history of infill. Overlying the erosional surface incising the Mio-pliocene pre-estuarine deposits there follows a succession of
fluvio-marine deposits (ca. 9000 calBP), an open estuarine facies with central basin muds and sandy tidal delta interbeds, with a
maximum ca. 6.500 calBP, and a transition to tidal flat deposits after ca. 2800 calBP. Two episodes of extreme wave energy at ca.
3000 calBP and ca. 195 calBP were identified and interpreted as tsunami surges, the latter ascribed to the catastrophic Lisbon
earthquake and the related tsunami.Está investigación ha sido financiada
por los proyectos CGL2012-33430 y CGL2013-42847-R,
así como por Fondos de la Faculty of Environment and
Technology, UWE Bristol (UK). Participa el Grupo de Investigación UCM 910198.Peer reviewe
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