L’Open Access à l’UNIL, Sondage Open Access UNIL 2017 - Rapport et Vision

L’Open Access, ou accès ouvert, est un vaste mouvement mondial, lancé par la Budapest Open Access Initiative en 2002, visant à mettre les résultats de la recherche à la disposition de tous grâce au développement de l’Internet. L’Open Access permet l’ouverture de documents par deux voies : la voie dorée (travaux librement accessibles au moment de la publication) et la voie verte (dépôt simultané d'une copie de la publication dans une archive institutionnelle, et son ouverture souvent après un embargo). Propulsée par la stratégie nationale sur l’Open Access, l’UNIL a pris la décision d’aborder cet enjeux d’une façon active, ouverte et inclusive. Le présent rapport s’inscrit dans le cadre d’une consultation interne au sein de l’UNIL ayant pour but ultime de définir les bases de sa future directive Open Access et l'ensemble des mesures de soutien aux chercheurs qui y seront associées

Open Access at UNIL - Report on the Open Access survey and vision

Open Access is a vast global movement, started by the Budapest Open Access Initiative of 2002, seeking to give everyone free access to the fruits of research through the development of the Internet. Open Access allows for the opening of documents by two roads: The Gold Road (research freely accessible from the moment of publication) and the Green Road (simultaneous self-archiving of the manuscript in an institutional repository and its opening after an embargo period). Propelled by the National Open Access Strategy (SNOAS), the University of Lausanne (UNIL) has decided to tackle this issue in an active, open and inclusive manner. This report is part of an internal consultation framework whose ultimate goal is to define the future Open Access policy and the associated overall support measures for researchers

The age of the Mont-Blanc granite (Western Alps) : a heterogeneous isotopic system dated by Rb-Sr whole rock determinations on its microgranular enclaves

New Rb-Sr whole rock age data have been obtained for the Mont-Blanc calc-alkaline Hercynian granite. Different facies of the granite have been sampled, as well as locally abundant microgranular enclaves of magmatic origin. The analytical data for the granite and for some of the enclaves are scattered within the Sr evolution diagram, which points to isotopic disequilibrium. Other enclaves form a homogeneous system which gives an age of 316.1 ± 19.5 Ma and an initial 87Sr/86Sr ratio of 0.7058 ± 0.0005. The following evolution is plausible: - individualization of microgranular enclaves due to the dismembering of mafic synplutonic dikes within the granitic magma; - complete isotopic equilibrium between granite and enclaves during a late-magmatic stage; - remobilization ofthe granite and certain enclaves in a post-magmatic stage and during Alpine orogenesis. Certain enclaves are not affected and retain the original characteristics of the system. The 316 Ma age of these "relics" and their initial ratio of 0.7058 are therefore thought to be valid for the granite as well. These results are similar to those obtained for other calc-alkaline Hercynian plutons in Western Europe. They indicate an origin for the granitic magma in the deep crust with involvement of mantle-derived material in unknown proportions, represented by the microgranular enclaves

Mont Blanc and Aiguilles Rouges geology of their polymetamorphic basement (external massifs, Westerns Alps, France-Switzerland)

Les massifs du Mont Blanc et des Aiguilles Rouges appartiennent aux massifs dits cristallins externes de la chaîne alpine occidentale. Ils sont constitués de roches pré-mésozoïques et dessinent des nappes de socle dans le bâti alpin. Ces massifs ont enregistré une longue histoire géologique comprenant le dépôt de sédiments néoprotérozoïques à cambriens, la mise en place de roches magmatiques basiques et ultrabasiques au paléozoïque inférieur, ainsi que l’intrusion de granitoïdes ordoviciens en contexte de marge active. Ces roches sont considérées appartenir à un ensemble de blocs continentaux originaires de la marge septentrionale du Gondwana et accrétés à la marge sud-européenne après leur détachement du Gondwana et leur dérive vers le nord consécutif à l’ouverture de la Paléotéthys. Cet épisode d’accrétion correspond à l’orogenèse varisque (hercynienne), bien documentée dans les massifs du Mont Blanc et des Aiguilles Rouges, par une évolution tectono-métamorphique polyphasée essentiellement carbonifère avec formation de migmatites et intrusion de granitoïdes de types variés. Une érosion active, liée à une forte exhumation, est enregistrée au carbonifère supérieur dans les dépôts détritiques continentaux de bassins d’effondrement de type graben. Ce mémoire présente des cartes géologiques inédites et des suggestions d’excursions dans ces secteurs nouvellement cartographiés. Les lithologies sont abondamment illustrées et décrites en détail du point de vue structural, pétrologique et géochimique. Les analyses chimiques sont fournies en annexe.The Aiguilles Rouges and Mont Blanc external massifs belong to the pre-Mesozoic basement areas of the external domain of the Alps. Before their involvement into the Alpine building (basement nappes) they registered a multiple geological evolution comprising the deposition of Neoproterozoic to Cambrian sediments and emplacement of granitoid and metabasic to ultramafic magmatic rocks of Early Palaeozoic age at the Gondwanan border. After rifting and drifting (formation of Palaeotethys) all rocks underwent polyphase metamorphic and structural transformations during the Variscan orogeny, and were intruded by late Variscan granitoids. The resulting polymetamorphic basement was eroded during formation of Upper Carboniferous sedimentary troughs. New geological maps are presented in this volume, together with structural, petrological and geochemical characteristics of all lithologies. The geochemical data are presented in annexes

Bimodal magmatism as a consequence of the post-collisional readjustment of the thickened Variscan continental lithosphere (Aiguilles Rouges-Mont Blanc Massifs, Western Alps)

ABSTRACT: High Precision U-Pb zircon and monazite dating in the Aiguilles Rouges-Mont Blanc area allowed discrimination of three short-lived bimodal magmatic pulses: the early 332 Ma Mg-K Pormenaz monzonite and associated 331 Ma peraluminous Montées Pélissier monzogranite; the 307 Ma cordierite-bearing peraluminous Vallorcine and Fully intrusions; and the 303 Fe-K Mont Blanc syenogranite. All intruded syntectonically along major-scale transcurrent faults at a time when the substratum was experiencing tectonic exhumation, active erosion recorded in detrital basins and isothermal decompression melting dated at 327-320 Ma. Mantle activity and magma mixing are evidenced in all plutons by coeval mafic enclaves, stocks and synplutonic dykes. Both crustal and mantle sources evolve through time, pointing to an increasingly warm continental crust and juvenile asthenospheric mantle sources. This overall tectono-magmatic evolution is interpreted in a scenario of post-collisional restoration to normal size of a thickened continental lithosphere. The latter re-equilibrates through delamination and/or erosion of its mantle root and tectonic exhumation/erosion in an overall extensional regime. Extension is related to either gravitational collapse or back-arc extension of a distant subduction zon

Timing of Palaeozoic magmatism in the Maggia and Sambuco nappes and paleogeographic implications (Central Lepontine Alps)

Magmatic rocks from the pre-Mesozoic basements of the Sambuco and Maggia nappes have been dated by U-Pb zircon ages with the LA-ICPMS technique. Several magmatic events have been identified in the Sambuco nappe. The mafic banded calc-alkaline suite of Scheggia is dated at 540Ma, an age comparable to that of mafic rocks in the Austroalpine Silvretta nappe. The Sasso Nero peraluminous augengneiss has an age of 480-470Ma, like many other "older orthogneisses” in Alpine basement units. It hosts a large proportion of inherited zircons, which were dated around 630Ma, a Panafrican age indicating the Gondwanan affiliation of the Sambuco basement. The calc-alkaline Matorello pluton yielded ages around 300Ma, similar to numerous Late Carboniferous intrusions in other basement units of the Lower Penninic (Monte Leone, Antigorio, Verampio) and Helvetic domains (Gotthard and other External Crystalline Massifs). Associated lamprophyric dykes are slightly younger (300-290Ma), like similar dykes sampled in gneiss blocks included in the sedimentary cover of the underlying Antigorio nappe (290-285Ma). The Cocco granodiorite and Rüscada leucogranite, both intruding the basement of the neighbouring Maggia nappe, yielded ages of ca. 300-310Ma, identical within errors to the age of the Matorello pluton. They are significantly older than former age determinations. This age coincidence, coupled with remarkable petrologic similarities between the Cocco and Matorello granodiorites, strongly suggests paleogeographic proximity of the Sambuco and Maggia nappes in Late Carboniferous times. In recent publications these two nappes have been interpreted as belonging to distinct Mesozoic paleogeographic domains: "European” for Sambuco and "Briançonnais” for Maggia, separated by the "Valais” oceanic basin. In this case, the similarity of the Matorello and Cocco intrusions would demonstrate the absence of any significant transcurrent movement between these two continental domains. Alternatively, according to a more traditional view, Sambuco and Maggia might belong to a single large Alpine tectonic uni

Estimation of a maximum Lu diffusion rate in a natural eclogite garnet

Lutetium zoning in garnet within eclogites from the Zermatt-Saas Fee zone, Western Alps, reveal sharp, exponentially decreasing central peaks. They can be used to constrain maximum Lu volume diffusion in garnets. A prograde garnet growth temperature interval of ~450-600 °C has been estimated based on pseudosection calculations and garnet-clinopyroxene thermometry. The maximum pre-exponential diffusion coefficient which fits the measured central peak is in the order of D0=5.7*10−6 m2/s, taking an estimated activation energy of 270kJ/mol based on diffusion experiments for other rare earth elements in garnet. This corresponds to a maximum diffusion rate of D (~600 °C) = 4.0*10-22 m2/s. The diffusion estimate of Lu can be used to estimate the minimum closure temperature, Tc, for Sm-Nd and Lu-Hf age data that have been obtained in eclogites of the Western Alps, postulating, based on a literature review, that D (Hf)< D (Nd) <D (Sm) ≤ D (Lu). Tc calculations, using the Dodson equation, yielded minimum closure temperatures of about 630 °C, assuming a rapid initial exhumation rate of 50°/m.y., and an average crystal size of garnets (r = 1mm). This suggests that Sm/Nd and Lu/Hf isochron age differences in eclogites from the Western Alps, where peak temperatures did rarely exceed 600 °C must be interpreted in terms of prograde metamorphis

Organization of pre-Variscan basement areas at the north-Gondwanan margin

Pre-Variscan basement elements of Central Europe appear in polymetamorphic domains juxtaposed through Variscan and/or Alpine tectonic events. Consequently, nomenclatures and zonations applied to Variscan and Alpine structures, respectively, cannot be valid for pre-Variscan structures. Comparing pre-Variscan relics hidden in the Variscan basement areas of Central Europe, the Alps included, large parallels between the evolution of basement areas of future Avalonia and its former peri- Gondwanan eastern prolongations (e.g. Cadomia, Intra-Alpine Terrane) become evident. Their plate-tectonic evolution from the Late Proterozoic to the Late Ordovician is interpreted as a continuous Gondwana-directed evolution. Cadomian basement, late Cadomian granitoids, late Proterozoic detrital sediments and active margin settings characterize the pre-Cambrian evolution of most of the Gondwana-derived microcontinental pieces. Also the Rheic ocean, separating Avalonia from Gondwana, should have had, at its early stages, a lateral continuation in the former eastern prolongation of peri-Gondwanan microcontinents (e.g. Cadomia, Intra-Alpine Terrane). Subduction of oceanic ridge (Proto-Tethys) triggered the break-off of Avalonia, whereas in the eastern prolongation, the presence of the ridge may have triggered the amalgamation of volcanic arcs and continental ribbons with Gondwana (Ordovician orogenic event). Renewed Gondwana-directed subduction led to the opening of Palaeo-Tethys

Contrasting magma types and timing of intrusion in the Permian layered mafic complex of Mont Collon (Western Alps, Valais, Switzerland): evidence from U/Pb zircon and 40Ar/39Ar amphibole dating

Abstract.: We have selected and dated three contrasting rock-types representative of the magmatic activity within the Permian layered mafic complex of Mont Collon, Austroalpine Dent Blanche nappe, Western Alps. A pegmatitic gabbro associated to the main cumulus sequence yields a concordant U/Pb zircon age of 284.2 ±0.6Ma, whereas a pegmatitic granite dike crosscutting the latter yields a concordant age of 282.9 ±0.6Ma. A Fe-Ti-rich ultrabasic lamprophyre, crosscutting all other lithologies of the complex, yields an 40Ar/39Ar plateau age of 260.2 ±0.7Ma on a kaersutite concentrate. All ages are interpreted as magmatic. Sub-contemporaneous felsic dikes within the Mont Collon complex are ascribed to anatectic back-veining from the country-rock, related to the emplacement of the main gabbroic body in the continental crust, which is in accordance with new isotopic data. The lamprophyres have isotopic compositions typical of a depleted mantle, in contrast to those of the cumulate gabbros, close to values of the Bulk Silicate Earth. This indicates either contrasting sources for the two magma pulses - the subcontinental lithospheric mantle for the gabbros and the underlying asthenosphere for the lamprophyres - or a single depleted lithospheric source with variable degrees of crustal contamination of the gabbroic melts during their emplacement in the continental crust. The Mont Collon complex belongs to a series of Early Permian mafic massifs, which emplaced in a short time span about 285-280Ma ago, in a limited sector of the post-Variscan continental crust now corresponding to the Austroalpine/Southern Alpine domains and Corsica. This magmatic activity was controlled in space and time by crustal-scale transtensional shear zone