Search results for " ROC"
showing 10 items of 951 documents
Growth and geomorphic evolution of the Ustica volcanic complex at the Africa-Europe plate margin (Tyrrhenian Sea)
2021
18 pages, 13 figures, 1 table
Parasitofauna del salmonete de roca (Mullus surmuletus) en el Mediterráneo español: variabilidad espaciotemporal y su implicación pesquera
2015
En el presente trabajo se ha realizado un estudio de la fauna de metazoos parásitos del salmonete de roca, Mullus surmuletus, en el Mediterráneo español. Se trata del estudio más detallado y completo hasta la fecha sobre los parásitos de este teleósteo en esta región. Además, en este trabajo investigamos las ventajas y limitaciones del uso de los parásitos como marcadores poblacionales y como herramientas para trazar el origen de las capturas de salmonete de roca con el fin de ayudar a gestionar y manejar esta especie que actualmente se encuentra sobreexplotada. Para ello se analizaron 1204 peces durante el período 2003-2006: 1000 procedentes de 5 puertos del Mediterráneo español (de norte …
De la viñeta al fotograma
2013
Arte, Música y Conceptualismo en América Latina
2021
Se investiga la relación entre el arte y la música desde el conceptualismo, que valida la existencia de un arte sonoro y de una música conceptuales, cuyas estéticas se alejan de la percepción coclear, para enfocarse en el campo de las ideas. Se sientan los antecedentes y se analiza el desarrollo de estos campos en occidente (Europa y Estados Unidos de América) desde las vanguardias del siglo XX hasta los años 60, para luego hacer una cartografía de la historia del conceptualismo sónico en Latino América desde los años 50 al presente, al redefinir, revalorar y contrastar las aportaciones que se han hecho en el continente, con un enfoque que se centra más en lo político y social, pero sin olv…
Unraveling the exhumation history of high-pressure ophiolites using magnetite (U-Th-Sm)/He thermochronometry
2020
International audience; Magnetite is a ubiquitous oxide in ultramafic and mafic rocks, which is present in a large range of geological and tectonic settings. In the case of high-pressure ultramafic rocks, exhumation timing is commonly constrained by geochronometers in nearby lithologies. The development of the magnetite (U-Th-Sm)/He method (MgHe) has opened new perspectives to refine the exhumation history of such rocks. However no thermal history has been deduced using MgHe data so far. Here we applied MgHe dating to magnetite from an HP-LT alpine ophiolite body (Rocher Blanc) from the Schistes lustres units (Western Alps, France) where part the P-T-t history is constrained to further refi…
SHRIMP ZIRCON AGES AND PETROLOGY OF LOWER CRUSTAL GRANULITE XENOLITHS FROM THE LETSENG-LA-TERAE KIMBERLITE, LESOTHO: FURTHER EVIDENCE FOR A NAMAQUA-N…
2013
Recrystallized zircons extracted from intermediate granulites of the Letseng-la-Terae Diamond Mine in northeastern Lesotho provide evidence that the Tugela Terrane of the Mesoproterozoic high-grade Namaqua-Natal mobile belt may extend ~200 km farther west than previously thought. The rock-forming minerals in the investigated lower crustal granulites contain garnet, clinopyroxene, plagioclase and quartz or garnet, wollastonite, plagioclase and quartz. Calculated values for peak granulite-facies metamorphism are ~13 kbar and ~850°C. Thermal overprint and therein granulite-facies metamorphism occurred during the late Mesoproterozoic and is documented by SHRIMP metamorphic zircon ages of 1018 ±…
Reworking of the Tarim Craton by underplating of mantle plume-derived magmas: Evidence from Neoproterozoic granitoids in the Kuluketage area, NW China
2011
Abstract Most Neoproterozoic granitoids in the Kuluketage area, northern Tarim Craton are characterized by strongly depleted HREE abundances and high Sr/Y and (La/Yb) N ratios, showing typical geochemical features of adakitic rocks. Zircon U–Pb dating of three adakitic plutons yielded Neoproterozoic ages (754 ± 4, 790 ± 3 and 798 ± 3 Ma). The adakitic granitoids exhibit low MgO and TiO 2 contents. Their low Cr, Co and Ni abundances, low ɛ Hf ( t ) values (−21 to −11) and high FeO T /MgO ratios (mostly 2.2–2.9) preclude the possibility of being derived from partial melts of delaminated lower crust. The relatively low ɛ Hf ( t ) values and old Hf two-stage model ages ( T DM 2 = 2 . 42 – 3 .0 …
Crystal-Plastic Deformation, Recovery and Recrystallisation of Quartz
2009
As stated in the introduction, this chapter is included because of the special importance of quartz to estimate metamorphic conditions during and after mylonitisation. The theory behind crystal-plastic deformation is treated elsewhere (e.g. Passchier & Trouw 2005). The main optical expression of crystal-plastic deformation is smooth, non-patchy undulose extinction. Elongated grains with such undulose extinction, sometimes accompanied by deformation lamellae, are indicative for low-temperature deformation. At slightly higher temperatures recovery produces subgrains and recrystallisation tends to substitute the old deformed grains by small new ones. Three types of recrystallisation can be dis…
Protomylonite, Mylonite and Ultramylonite
2009
The objective of this chapter is to show how variation of strain intensity can be judged in thin section. Usually this kind of variation can best be observed in low-grade mylonites where the percentage of porphyroclasts decreases progressively with strain intensity. However, the percentage of matrix is highly dependent on mineralogical composition (e.g. quartz and biotite tend to convert to matrix readily). Compositional banding in gneiss can therefore result in mylonitic banding of apparent strain variation, which in fact only reflects variation in composition of the parent rock. Several examples of ultramylonite are derived from quartzitic rocks that tend to form few or no porphyroclasts …
Low-Grade Mylonites
2009
The temperature range for these mylonites is thought to be roughly between 250 and 500 °C. There is a gradual transition between cataclasites and low-grade mylonites. Whereas many feldspar porphyroclasts in low-grade mylonites still show fracturing by cataclasis, the quartz is usually deformed by crystal-plastic processes as shown by its change in shape and by undulose extinction. At increasing temperature bulging recrystallisation starts to manifest itself along the lobate contacts and eventually recrystallisation by subgrain rotation takes over (Chapter 10).