Evidence of a Paleoproterozoic basement in the Moroccan Variscan

For the first time, an Eburnian magmatic event has been identified in the Rehamna Massif (Moroccan Variscan Belt, Western Meseta) located north of the South Meseta fault. The best estimate of the crystallization age of rhyolitic porphyry is given by a weighted mean 207Pb/206Pb age of 2050.6 ± 3 Ma (Rhyacian-Orosirian). The new U–Pb age obtained for rhyolitic porphyry from the Rehamna Massif is of great relevance for improving geological knowledge about the boundaries of the WAC because: (i) it overlaps the older Eburnian magmatic event described in the Anti-Atlas belt and the Icartian magmatic event of the European Variscan Belt; (ii) this suggests that exists Paleoproterozoic basement in the Western Meseta, a hundred kilometers further to the north of the South Meseta fault, as old continental crust slivers preserved in the Cadomian and Variscan belts; and (iii) this means that the Cambrian transgression in the Western Meseta probably took place based on a more complex structural architecture affecting the Precambrian basement composed not only of Ediacaran rocks, as has been suggested in the literature, but also with Paleoproterozoic rocks (ca. 2.05 Ga) as discovered in this study

Discussion on Detrital zircon geochronology of the Carboniferous Baixo Alentejo Flysch Group (South Portugal); constraints on the provenance and geodynamic evolution of the South Portuguese Zone, Journal, vol. 172, 294-308

In their recent study, Rodrigues et al. (2014) attempted a provenance analysis of the Carboniferous Baixo Alentejo Flysch Group (SW Iberia), discussing variability over time in sources of South Portuguese Zone turbidites. The U–Pb ages presented by these authors are similar to those previously obtained by Pereira et al. (2012a, 2013). A comparison of U–Pb age distributions obtained in turbidites from the two studies using the Kolmogorov–Smirnov test indicates that they are not significantly different at the 5% confidence level, increasing the statistical significance of the detrital zircon populations of each stratigraphic formation. However, the interpretations put forward in the two studies are considerably different

Potential sources of Ediacaran strata of Iberia: a review

Advances in stratigraphy, geochemistry and U-Pb detrital zircon geochronology from Ediacaran strata of Iberia allow for the improved characterisation of crustal growth in the North Gondwana active margin. The formation of Cadomian magmatic arcs and associated back-arc basins that took place in the North Gondwana active margin was a long-term process. Iberia has been placed in the Cadomian belt in currently accepted palaeogeography reconstructions at c. 570–560 Ma, based on the characteristics of Ediacaran strata. The Ediacaran strata of Iberia with outstanding geochemical homogeneity are distributed across three zones of Iberia: (1) Narcea Slates in the Cantabrian and West Asturian Leonese zones (maximum depositional age of c. 600 and 553 Ma); (2) Schist–Greywacke Complex (Lower Series) in the Central Iberian Zone (maximum depositional age of c. 578 to 550 Ma); and (3) Série Negra in the Ossa-Morena Zone (maximum depositional age of c. 590–545 Ma). Pre-Cryogenian detrital zircons found in the Ediacaran strata of Iberia seem to be related to distal sources distributed across three main areas of North Gondwana inland. The oldest detrital zircons probably derive from distal sources such as the West African craton, the Trans-Saharan belt and the Arabian–Nubian Shield, in view of the increase in distance from sedimentary basins. The West African craton is the most likely source for Archean and Palaeoproterozoic detrital zircons, while the Trans-Saharan belt and the Arabian–Nubian shield could provide a source for Tonian and Mesoproterozoic grains. The youngest zircon ages (c. 630–545 Ma), which make up the dominant population in the Ediacaran strata of Iberia, are probably derived from proximal sources as would be the Cadomian magmatic arc system, not excluding the contribution of the Pan-African orogen

Variscan intra-orogenic extensional tectonics in the Ossa–Morena

Following a Middle–Late Devonian (c. 390–360 Ma) phase of crustal shortening and mountain building, continental extension and onset of high-medium-grade metamorphic terrains occurred in the SW Iberian Massif during the Visean (c. 345–326 Ma). The E ´ vora–Aracena– Lora del Rı´o metamorphic belt extends along the Ossa–Morena Zone southern margin from south Portugal through the south of Spain, a distance of 250 km. This major structural domain is characterized by local development of high-temperature–low-pressure metamorphism (c. 345– 335 Ma) that reached high amphibolite to granulite facies. These high-medium-grade metamorphic terrains consist of strongly sheared Ediacaran and Cambrian–early Ordovician (c. 600–480 Ma) protoliths. The dominant structure is a widespread steeply-dipping foliation with a gently-plunging stretching lineation generally oriented parallel to the fold axes. Despite of the wrench nature of this collisional orogen, kinematic indicators of left-lateral shearing are locally compatible with an oblique component of extension. These extensional transcurrent movements associated with pervasive mylonitic foliation (c. 345–335 Ma) explain the exhumation of scarce occurrences of eclogites (c. 370 Ma). Mafic-intermediate plutonic and hypabyssal rocks (c. 355–320 Ma), mainly I-type high-K calc-alkaline diorites, tonalites, granodiorites, gabbros and peraluminous biotite granites, are associated with these metamorphic terrains. Volcanic rocks of the same chemical composition and age are preserved in Tournaisian–Visean (c. 350–335 Ma) marine basins dominated by detrital sequences with local development of syn-sedimentary gravitational collapse structures. This study, supported by newU–Pb zircon dating, demonstrates the importance of intraorogenic transtension in the Gondwana margin during the Early Carboniferous when the Rheic ocean between Laurussia and Gondwana closed, forming the Appalachian and Variscan mountains

User acceptance of open enterprise solution: the OSS-ERP case

Organizations implement Enterprise Resource Planning (ERP) systems with the objective of reaching operational efficiency and the incorporation to new markets through the information flow control on time of the entire organization. However, ERP systems are complex tools, mainly for the small and medium size enterprises (SMEs). For these reason, new ERP configurations have arisen for SMEs such as Open Source Software-ERP (OSS-ERP). OSS-ERP is a research topic barely analyzed by the literature. Specifically, this paper’s aim is to focus on the OSS-ERP users’ acceptance and use. The authors have developed a research model based on the Technology Acceptance Model (TAM) for testing the users’ behavior toward OSS-ERP.Las organizaciones implantan Sistemas Integrados de Gestión (ERP, acrónimo de Enterprise Resource Planning) con el objetivo de alcanzar eficiencias operativas y la incorporación a nuevos mercados mediante un mayor control del flujo de información de toda la empresa a tiempo real. Sin embargo, los sistemas ERP son herramientas complejas, principalmente la pequeña y mediana empresa (PYME). Por esta razón, están surgiendo nuevas configuraciones de sistemas ERP para PYME como los sistemas ERP de código abierto (OSS-ERP). OSS-ERP es un tópico de investigación escasamente analizado en la literatura. Concretamente, este artículo se centra en el y aceptación de los usuarios a los sistemas OSS-ERP. Los autores han desarrollado un modelo de investigación basado en Metamodelo de Aceptación de la Tecnología (TAM) para testar el comportamiento de los usuarios hacia los sistemas OSS-ERP

Orthogonality catastrophe and Kondo effect in graphene

Anderson's orthogonality catastrophe in graphene, at energies close to the Dirac point, is analyzed. It is shown that, in clean systems, the orthogonality catastrophe is suppressed, due to the vanishing density of states at the Dirac point. In the presence of preexisting localized states at the Dirac energy, the orthogonality catastrophe shows similar features to those found in normal metals with a finite density of states at the Fermi level. The implications for the Kondo effect induced by magnetic impurities, and for the Fermi edge singularities in tunneling processes are also discussed.Comment: 7 pages, 7 figure

Effect of user experience on technology acceptance: the case of foss

Free and open source software (FOSS) movement essentially arises like answer to the evolution occurred in the market from the software, characterized by the closing of the source code. Furthermore, some FOSS characteristics, such as (1) the advance of this movement and (2) the attractiveness that contributes the voluntary and cooperative work, have increased the interest of the users towards free software. Traditionally, research in FOSS has focused on identifying individual personal motives for participating in the development of a FOSS project, analyzing specific FOSS solutions, or the FOSS movement itself. Nevertheless, the advantages of the FOSS for users and the effect of the demographic dimensions on user acceptance for FOSS have been two research topics with little attention. Specifically, this paper’s aim is to focus on the influence of the user experience with FOSS the FOSS acceptance. Based on the literature, user experience is an essential demographic dimension for explaining the Information Systems acceptance. With this purpose, the authors have developed a research model based on the Technological Acceptance Model (TAM).El movimiento asociado al software de código abierto (FOSS) surge como una respuesta a la evolución acontecida en el mercado del software, caracterizado por el cierre del código fuente. Además, algunas características del FOSS como (1) el avance de este movimiento y (2) el atractivo que suscita debido a que se construye bajo la filosofía de trabajo voluntario y cooperativo, ha incrementado el interés de los usuarios hacia FOSS. Tradicionalmente las investigaciones en FOSS han estado centradas en identificar las motivaciones personales de participar en el desarrollo de un proyecto FOSS. Mientras que las ventajas del FOSS para los usuarios y el efecto de las dimensiones demográficas en la aceptación de FOSS han sido dos tópicos de investigación con poca atención. Concretamente, este artículo se centra en analizar la influencia de la experiencia con FOSS en la propia aceptación de FOSS. Basado en la literatura, la experiencia del usuario es una dimensión demográfica esencial para explicar la aceptación de los Sistemas de Información. Con este propósito, los autores han desarrollado un modelo de investigación basado en el Metamodelo de Aceptación de la Tecnología (TAM)

Understanding Geological Data Distribution and

Insufficient field test results and a sufficiently large degree of spatial disorder exhibited by melt flow properties on sheared migmatites leads us to use stochastic methods to describe the distribution and orientation of leucogranitoid veins in sheared continental crust. Qualitative data present challenges to evaluators seeking to analyse visual information from spatial observations. In this manuscript, we work through a structured approach to analyse qualitative data based on an interactive process of considering the objective of the analysis, reviewing suitable options, and working through interpretation. Techniques include grouping, summarizing, finding patterns, discovering relationships, and developing and testing relationships. The aim of this paper is to give an overview of the methodological contribution in multidimensional categorical data analysis based on correspondence analysis, which enables the analysis of a contingency table when the behaviour of one variable is supposed to be dependent on the other cross-classified variable. The analytical procedures gave statistically valid and significantly similar results for the geometrical relationships between different attributes observed in the Almansor migmatites (Évora High-Grade Metamorphic Terrains, Portugal)—leucogranitoid veins, boudins/rock fragments, folds, shear planes, and host rock/diatexite layering. The interpretation of the obtained results allowed the definition of two main geological implications. First, the association of the host rock/diatexite with the leucogranitoids I defines the compositional layering of these migmatites (with 290°–310°-trending). Secondly, the shearing is responsible for the observed structural complexity. Here leucogranitoids tend to occur associated with local perturbations of the main 290°–310°-trending of the compositional layering. They tend to occur discordant to the compositional layering (foliation) strike filling 260°–270°-trending c′-type extensional shear planes, filling dilatant structures in between or/and surrounding boudins/rock fragments and affected by folding. The applied stochastic analysis was a useful approach to properly examine and quantify the structural variability of this complex natural phenomenon

Layered granitoids: Interaction between continental crust recycling processes and

In this paper, field, petrographic, mineralogical, geochemical and isotopic (Rb–Sr and Sm–Nd) information from three areas within the Évora Massif (Iberian Variscan Orogen) is presented and discussed aiming at to unravel the relationships between granitoids and units mapped as migmatites and also to evaluate the interplay between mantle and crustal derived magmas. One of the areas – Almansor – displays a well-developed compositional layering (concordant with the regional Variscan structure) which was considered, in previous works, as an alternation of leucosome and melanosome. In this study, the layering is described as intercalation of diatexites, weakly foliated granitoids and trondhjemitic veins. Diatexites have characteristics of crustal melts plus restitic material and, according to geochemical and isotopic evidence, result from anatexis of Ediacaran metasediments. Weakly foliated granitoids and trondhjemitic veins from Almansor have calc-alkaline signatures and may be related to each other by crystal fractionation processes; however, the mixing between mafic (mantle-derived) and felsic (diatexitic melt) magmas revealed by the isotopic data may also explain their genesis. In the Alto de São Bento area, several igneous lithologies (tonalites, granodiorites, porphyritic granites and leucogranites) are present and show typical isotropic igneous textures. Despite structural and textural differences, geochemical data support, for most rocks, an origin from the same calk-alkaline suite, also present at Almansor. The Alto de São Bento leucogranites have an isotopic signature that, although different from that obtained in the Almansor diatexites, is still compatible with an origin involving melting of Ediacaran metasediments; compositions, with very low contents of usually incompatible elements, flat normalized REE patterns and strong negative Eu anomalies, suggest that the anatectic melt has undergone crystal fractionation processes before reaching the composition of the leucogranite magma. The Almansor outcrop is then interpreted as the remnants of a shear zone that operated as a pathway for melts that moved upward through the crust providing the locus for differentiation and mingling/mixing of magmas, whilst Alto de São Bento would correspond to the zone, at a higher crustal level, where magmas were trapped and forced to spread horizontally. At Valverde (the third area) foliated and non-foliated granitoids are spatially related and field criteria links these rocks to metamorphic protolith and anatectic melt, respectively. However, petrographic, geochemical and isotopic information shows that they all are compositionally identical trondhjemites with no evidence of metamorphic fabric. In the foliated rocks, mesoscopic features are interpreted as resulting from melt segregation structures formed in a crystallizing mush. In contrast to the previous areas, the Valverde trondhjemites probably do not belong to the main calc-alkaline plutonic suite of the Évora Massif, since they have a distinct Sr and Nd isotope signature

Transcurrent continental tectonics model

The Ossa-Morena Zone (SW Iberian Massif) was affected by continuous orogen-parallel transcurrent continental tectonics from the Neoproterozoic to the Carboniferous times, involving transtension (TT) and transpression (TP) processes that co-existed together, occurred separately in neighbouring regions by the means of strain partitioning or even worked diachronically. A first stage of transpression TP1 took place during the Late Neoproterozoic–Lower Cambrian as a result of Cadomian arc-continent collisional processes. Structures generated by transtension TT1 from Cambrian to Lower Devonian were related to strong lithosphere stretching responsible for the development of basins controlled by major detachments, tilting, rifting and important tectono–thermal diachronic processes. Denudation phenomena and inhibition of sedimentation related with thermal uplift (asthenosphere upwelling) and consequent subsidence caused by isostatic equilibrium, involving generalized transgressions, were processes responsible for major unconformities. The Variscan TP2-TT2 episodes that followed diachronically TP1-TT1, by maintaining the orogen- parallel transport direction, were concomitant with syntectonic deposition of continental basins in the OMZ and foreland basins in the SPZ. TT2 local transtension and tectonic exhumation of deep crustal rocks along major shear zones, favoured the opening of tectonic troughs filled up by sediments and volcanism. TP2 shortening have generated fold axes parallel to the orogen- strike and composite dissymmetric flower structures