Search results for "otolith"
showing 10 items of 149 documents
Geochemical data and zircon ages for rocks in a high-pressure belt of Chu-Yili Mountains, southern Kazakhstan: Implications for the earliest stages o…
2011
Abstract The mechanism and age of Palaeozoic accretion in the Central Asian Orogenic Belt remain poorly constrained. One of the most complex belts extends from the Kokchetav area in northern Kazakhstan to the Kyrgyz northern Tianshan. It represents an assemblage of small blocks with Palaeoproterozoic continental crust, intervening slivers containing early Palaeozoic ophiolites and/or deep-marine sediments, and a number of HP and UHP metamorphic complexes. The HP–LT metamorphic rocks provide important clues for reconstructions of the overall structure and evolution of the accretionary collage. This study is aimed to constrain the metamorphic age and tectonic implications of HP garnet pyroxen…
Structural and functional organization of fish assemblages in a Mediterranean shallow CO2 vent.
2017
Gli effetti dell’acidificazione degli oceani a livello globale hanno richiamato l’attenzione degli scienziati su dei sistemi marini naturali quali i vent superficiali di CO₂. Si tratta di mesocosmi naturali, in quanto su piccole scale spaziali (anche di pochi metri) si osservano marcati gradienti di pH, dove poter testare ipotesi ecologiche dell’acidificazione delle acque marine. Obiettivo della tesi è studiare le risposte della popolazione ittica alla riduzione del pH in vent superficiali mediterranei utilizzando numerosi descrittori, quali la struttura di comunità, l’organizzazione trofica, le caratteristiche e la composizione chimica delle strutture carbonatiche. Inoltre poiché i vent so…
Shape indices to identify regional differences in otolith morphology of comber, Serranus cabrilla (L., 1758)
2003
Summary Sagittal otoliths from the Atlantic and Mediterranean regions of Serranus cabrilla L. were compared using shape indices (form-factor, roundness, circularity, rectangularity, ellipticity and eccentricity). Regional differences were best described by form-factor, circularity and eccentricity variables. The canonical discriminant functions were built with form-factor or rectangularity indices. The results indicated slight regional variations. The G-test was the criterion more useful to identify the otolith origin in the discriminant analysis.
Transition from self tilt to object tilt during maintained lateral tilt in parabolic flight.
1991
Abstract 19 young healthy subjects were subjected to parabolic rollercoaster flight. A horizontal luminous line was seen by the subjects in a headfixed goggle device. During the hypergravic phases of parabolic flight the luminous line seemed to rotate into and during the hypogravic phase against the direction of static head tilt. Ocular counter rotation and activity of the neck position receptors cannot explain these subjective rotations. We conclude that information from the otolith system, converging with visual information within the brain, dislocated the headfixed visual target line. While the retinal image of the luminous line remains unchanged, loading and unloading the otoliths in pa…
Dispersal of larval and juvenile seabream: Implications for Mediterranean marine protected areas
2015
International audience; In the marine context, information about dispersal is essential for the design of networks of marine protected areas (MPAs). Generally, most of the dispersal of demersal fishes is thought to be driven by the transport of eggs and larvae in currents, with the potential contribution of dispersal in later life stages relatively minimal.Using otolith chemistry analyses, we estimate dispersal patterns across a spatial scale of approximately 180 km at both propagule (i.e. eggs and larvae) and juvenile (i.e. between settlement and recruitment) stages of a Mediterranean coastal fishery species, the two-banded seabream Diplodus vulgaris. We detected three major natal sources …
Nonstoichiometric silica mask to fabricate reverse proton-exchange waveguides in lithium niobate crystals
2004
Producing channel waveguides requires a photolithographic mask, but the standard technique of using thermally evaporated metal films for proton exchange has proved to be unsuitable for withstanding the rather aggressive process of reverse proton exchange. We report the fabrication of a nonstoichiometric silica mask by ion-plating plasma-assisted deposition. This mask is strong enough to resist both direct and reverse proton exchange and is also compatible with anisotropic dry etching for patterning the mask and with electric field poling. Our technique is a practical alternative to the use of SiO2 sputtered masks.
The tectonic domains of southern and western Madagascar
2019
Abstract Southern and western Madagascar is comprised of five tectonic provinces that, from northeast to southwest, are defined by the: (i) Ikalamavony, (ii) Anosyen, (iii) Androyen, (iv) Graphite and (v) Vohibory Domains. The Ikalamavony, Graphite and Vohibory Domains all have intermediate and felsic igneous protoliths of tonalite-trondhjemite-granodiorite-granite composition, with positive eNd, and low Sr and Pb isotopic ratios. All three domains are interpreted to be the products of intra-oceanic island arc magmatism. The protoliths of the Ikalamavony and Graphite Domains formed repectively between c. 1080–980 Ma and 1000–920 Ma, whereas those of the Vohibory Domain are younger and date …
The geochemistry of the Barra do Itapirapua carbonatite (Ponta Grossa Arch, Brazil): a multiple stockwork
2002
The Early Cretaceous Barra do Itapirapuā carbonatite, in southern Brazil, belongs to the initial stages of the alkaline carbonatitic magmatism in the Ponta Grossa Arch Province, as related to the opening of the south Atlantic Ocean. The magmatic evolution of the complex comprises four phases of intrusive carbonatite that are composed of medium- to coarse-grained Mg and Fe carbonatites with small volumes of late fine- to very fine-grained Mg carbonatites and show evidence of pervasive hydrothermal events. Drill core samples reveal the existence of silicate rocks of syenitic composition of two different origins. Among the silicate rocks, there are syenites of a likely magmatic origin, as well…
Zircon ages of metamorphic and magmatic rocks within peridotite-bearing mélanges: Crucial time constraints on early Carboniferous extensional tectoni…
2013
Abstract We dated and geochemically characterized peridotite-bearing melanges in the Chinese South Tianshan and within the Main Tianshan Shear Zone. The Yushugou-Tonghuashan melange in the Chinese South Tianshan exposes a tectonic juxtaposition of a diapirically emplaced metaperidotite (predominantly lherzolite) massif with a high-grade metamorphic terrane (ca. 10 km long; protolith age ≥ ca. 445–466 Ma). Metamorphic zircons of a mafic granulite (eNd(t) = 5.0) yielded a weighted mean 206Pb/238U age of 341 ± 8 Ma that we interpret as the time of granulite-facies metamorphism. The youngest zircon rims of an intermediate granulite (eNd(t) = − 4.3) have a mean age of 332 ± 13 Ma that records a …
Anatectic amphibole and restitic garnet in Variscan migmatite from NE Sardinia, Italy: insights into partial melting from mineral trace elements
2014
We report results of a laser-ICP-MS investigation of trace element contents in the main constituent minerals of an amphibole-bearing migmatite from the Variscan orogen in northeastern Sardinia. The migmatite is associated with migmatised orthogneiss and Al-silicate-bearing pelitic migmatites. The protolith of the amphibole-bearing migmatite was a mid-Ordovician igneous rock of intermediate composition characterised by a biotite + plagioclase + quartz assemblage. The migmatite consists of mesosomes and tonalitic (or, less frequently, granodioritic) leucosomes, characterised by amphibole crystals (potassian ferropargasite) up to 2 cm in size. The tonalitic leucosomes are made up of quartz, pl…