U-Pb geochronology of the El Jadida rhyolite and relation to possible Lower Cambrian recycling (Coastal block, Moroccan Meseta).

The El Jadida (Mazagan) dome, whose existence was reported as early as 1934 by Yovanovitch and Freys, constitutes one of the first outcrops of the Moroccan Meseta where the Precambrian (PIII?)-Paleozoic (Lower Cambrian?) boundary was established (Gigout, 1951; Cornée et al., 1984). Since then, it is listed as one of the few locations where the basement of the Moroccan Variscan belt can be observed (Hoepffner et al.. 2005; Michard et al., 2010).Despite, the absence of geochronological and biostratigraphic precise data to constrain the time interval recorded here, there are stratigraphic similarities that allow a correlation with the Ediacaran-Cambrian geological record of Anti-Atlas belt (Cornée et al., 1984). In this study, we developed a petrographic, geochemical and U-Pb geochronological study using zircon extracted from: (i) the El Jadida rhyolite with the aim of characterizing the magma source and estimate the age of crystallization; (ii) a microbreccia sampled at the base of the El Jadida Dolomitic Formation for determining provenance

Sedimentary provenance of siliciclastic rocks from the Lalla Mouchaa Calcschists Formation (Coastal Block, Western Rehamna): Evidence of denudation of ca. 2 Ga basement in the Moroccan Meseta.

Paleoproterozoic basement rocks (ca. 2Ga) are scarce along the European and North African Paleozoic mountain chains (Fig.1a). In Morocco, ca. 2.2-2Ga granitic rocks (Gasquet et al., 2008; Kouyaté et al., 2013) have been exclusively reported in the Western Anti-Atlas at southwest of the Anti-Atlas Major Fault, (Choubert, 1963). In Eastern and Central Anti-Atlas and in the Moroccan Meseta, the existence of a Paleoproterozoic basement has only been recognized through indirect evidence (Gasquet et al., 2008; Michard et al., 2010). In the Anti- Atlas belt, ca. 2Ga detrital zircon grains are found in the Ediacaran siliciclastic rocks of the Bou Salda, Saghro and Taghdout groups (Abati et al., 2010). In the Moroccan Meseta, Paleoproterozoic (ca. 2Ga) zircon grains were extracted from gneiss and granitic xenoliths found in Triassic lamprophyre dykes, and from Carboniferous granophyric microgranite intrusions of central Jebilet (Dostal et al., 2005, Essaifi et al., 2003). Recently, a porphyritic rhyolite from the Rehamna Massif was dated at ca. 2.05Ga (Pereira et al., 2015), demonstrating for the first time, the exposure of the Eburnian basement in the Western Meseta. These Eburnian arc-related magmatic rocks, which are exposed to the south of the Permian Sebt Brikiyine granite in the core of anticlines from the Lalla Mouchaa Anticlinorium, are allegedly unconformably overlained by transgressive siliciclastic and carbonate beds (Corsini, 1988; Pereira et al., 2015). At north of the Sebt Brikiyine granite the probable Lower Cambrian sequence (Lalla Mouchaa Calcschists Formation; Guezou & Michard, 1976; Corsini, 1988) comprises a basal unit of microbreccias, arkosic sandstones and siltstones (lower member) that pass towards the top to centimeter-thick beds of calcschists interbedded with limestones and dolomites (upper member) that are conformably overlain by the “Paradoxides Shale Formation” composed of siltstone, greywacke and sandstone with Middle Cambrian fauna. In order to study the potential sources of the Lalla Mouchaa Calcschists Formation (probable Lower Cambrian), we have sampled a microbreccia at the Koudiat El Hamra region, for U-Pb geochronology on detrital zircon. This foliated microbreccia is composed of elongated Kfeldspar and quartz phenocrysts surrounded by a fine-grained matrix. Detrital zircon grains gave 206Pb/238Ub ages that in the Probability density plot curve are distributed by two main age peaks at ca. 2.05Ga and ca. 2.03Ga (Fig.1b), yielding a 206Pb/238U age-weighted mean of ca. 2.04Ga (El Houicha et al., 2018). The obtained U-Pb results point to a provenance from a Paleoproterozoic source, suggesting a possible contribution from rocks of the same age of the 2Ga porphyritic rhyolite exposed at south of the Sebt Brikiyine granite. Thus, there is a possibility that the Paleoproterozoic basement extends bellow the Paleozoic and Neoproterozoic sequences of the Rehamna massif

Recycling of the Proterozoic crystalline basement in the Coastal Block (Moroccan Meseta): New insights for understanding the geodynamic evolution of the northern peri-Gondwanan realm

Detrital zircon age spectra from the siliciclastic rocks of the Lalla Mouchaa Calcschists and El Jadida Dolomitic formations (the Coastal Block of the Moroccan Meseta) are dominated by Paleoproterozoic and Ediacaran ages. The provenance of these two formations is a composite Proterozoic crystalline basement. El Jadida rhyolite (584.2 ± 4.8 Ma) represents the Ediacaran crystalline basement of the El Jadida dome. El Jadida rhyolite is unconformably overlain by the microbreccia, arkosic sandstone and dolostone of the El Jadida Dolomitic Formation with a maximum depositional age of ca. 539 Ma (Lower Cambrian). Detrital zircon-age spectra from El Jadida Dolomitic Formation (ca. 583–582 Ma) suggest direct recycling of El Jadida rhyolite as an exclusive original primary source. However, in the Western Rehamna massif, detrital zircon-age spectra from pre-Middle Cambrian microbreccia and arkosic sandstone of the Lalla Mouchaa Calcschists Formation (ca. 2.05–2.03 Ga) indicate exclusive recycling of the ca. 2.05 Ga-aged crystalline basement rocks (original primary source). Detrital zircon contents of the siliciciclastic rocks from these two formations of the Coastal Block are consistent with derivation from either Eburnian (Paleoproterozoic) or Cadomian/Pan-African (Ediacaran) igneous rocks. The discovery of this composite Proterozoic crystalline basement in the Moroccan Meseta stresses that Cadomian/ Pan-African magmatic arcs were built on an Eburnian basement in a paleoposition close to the West African craton, as part of the northern peri-Gondwanan realm

The Electromagnetic Form Factor of the Kaon in the Light-Front Approach

The kaon electromagnetic form factor is calculated within a light-front constituent quark model (LFCQM). The electromagnetic components of the current are extracted from the Feynman triangle diagram within the light-front approach. We also obtain the electroweak decay constant and the charge radius for the kaon in the light-front approach. In this work, the kaon observables are calculated and a fairly good agreement is obtained with a very higher accuracy when compared with the experimental data.Comment: Paper with 4 pages, 1 figure, reference: XII HADRON PHYSICS Conference - to appear in AIP Conference Proceeding

A minimal HIV-AIDS infection model with general incidence rate and application to Morocco data

We study the global dynamics of a SICA infection model with general incidence rate. The proposed model is calibrated with cumulative cases of infection by HIV-AIDS in Morocco from 1986 to 2015. We first prove that our model is biologically and mathematically well-posed. Stability analysis of different steady states is performed and threshold parameters are identified where the model exhibits clearance of infection or maintenance of a chronic infection. Furthermore, we examine the robustness of the model to some parameter values by examining the sensitivity of the basic reproduction number. Finally, using numerical simulations with real data from Morocco, we show that the model predicts well such reality.Comment: This is a preprint of a paper whose final and definite form is with 'Statistics Opt. Inform. Comput.', Vol. 7, No 2 (2019). See [http://www.IAPress.org]. Submitted 16/Sept/2018; Revised 10 & 15/Dec/2018; Accepted 15/Dec/201

The Thirring interaction in the two-dimensional axial-current-pseudoscalar derivative coupling model

The authors reexamine the two-dimensional model of massive fermions interacting with a massless pseudoscalar field via axial-current-pseudoscalar derivative coupling. Performing a canonical field transformation on the Bose field algebra the model is mapped into the Thirring model with an additional vector-current-scalar-derivative interaction (Schroer-Thirring model). The complete bosonized version of the model is presented. The bosonized composite operators of the quantum Hamiltonian are obtained as the leading operators in the Wilson short distance expansion.Comment: 13 page

Leitmann's direct method for fractional optimization problems

Based on a method introduced by Leitmann [Internat. J. Non-Linear Mech. {\bf 2} (1967), 55--59], we exhibit exact solutions for some fractional optimization problems of the calculus of variations and optimal control.Comment: Submitted June 16, 2009 and accepted March 15, 2010 for publication in Applied Mathematics and Computation

Structures in jurassic rocks of the Wessex Basin, Southern England - I : field example of deformed crustal wedges

Levantamento estrutural de detalhe realizado na Formação Purbeck (Jurassico) no afloramento Fossil Forest de Lulworth Cove (Dorset, sul da Inglaterra) permite definir a existência de uma cunha (~ 10m de espessura) de camadas exibindo diferentes padroes de deformação segundo quatro andares (L2-L5) justapostos na vertical, e situados entre dois andares de camadas nao deformadas (LI e L6). O andar inferi- or, L1, consiste de carbonates nao deformados e L6 consiste de calcareos e folhelhos / argilitos. No andar L2 da cunha deformada margas calcareniticas exibem estrutura de almofada devida a uma foliação anastomosada sub-horizontal, e sao sotopostas a evaporitos e folhelhos com lentes de chert, exibindo dezenas de estruturas na forma de cogumelos de escala me'trica; no andar L3 evaporitos e folhelhos exibem estruturas centimétricas a decimétricas como falhas extensionais e contracionais, dobras, boudins e foliação paralela aos contatos; no andar L4 evaporitos e folhelhos estão envolvidos em melange tectonica; e, no andar L5, camadas de evaporitos e carbonates, com folhelhos e argilitos intercalados, exibem estruturas metricas, como falhas extensionais e contracionais, e dobras associadas a fraturamento ruptil nas charneiras, o que as transforma em Camadas Brechadas. A deformação se deu progressivamente, a medida que cunha movia-se acima de um descolamento extensional ao longo dos andares L3 e L4 (capa deslizando para oeste), e abaixo de um descolamento (lapa deslizando para oeste) formado ao longo de camada de folhelho da base do andar L6. A analise estrutural aqui reportada, conjuntamente com outros dados da literatura, todos indicam que um evento de extensao afetou a area regionalmente, nos estagios iniciais da inversao Alpina que afetou a bacia de Wessex e que resultou ao final no basculamento de toda a Formação Purbeck para norte, incluindo nela a cunha deformada, no interior da qual as Camadas Brechadas foram submetidas a movimentação adicional. O deslizamento da cunha de rochas e a partifao vertical da deformação, tanto em estilo como em intensidade, colocam o afloramento em questao como localidade-tipo para direta observação de processes tectonicos análogos aos que vem sendo reconhecidos correntemente na literatura internacional para deformação da crosta continental. _________________________________________________________________________________________ ABSTRACTDetailed studies of the Purbeck Formation (Jurassic) in the Fossil Forest outcrop, Lulworth Cove (Dorset, southern England) allow to define a ~ 10 m-thick wedge of deformed layers comprising four juxtaposed structural levels (L2-L5) situated between two levels of non deformed layers (L1 and L6). L1 consists of limestone and L6 consists of limestone and intercalated shale / argillite. Within the wedge, the basal structural level (L2) consists of calcareous marls displaying pillow-like structures due to a layer-parallel anastomosed foliation, and evaporite, shale and chert displaying m-scale mushrooms; level L3 consists of evaporite and shale displaying cm- to dm-scale features like normal and thrust faults, folds, foliation and boudins; level L4 consists of evaporite and shale transformed into a tectonic melange; and level L5 consists of evaporite and limestone affected by m-scale folds, contraction and extension faults. Intensive fracturing of the layers around the hinges of the folds transformed L5 in a set of Broken Beds, The wedge deformed progressively, as it slided above a top-down to the west basal detachment along levels L3 and L4, and below a bottom-down to the west detachment established along a layer of calcareous shale (bottom of level L6). The structural analysis, together with other published data, all indicate that an event of extension affected regionally the area, earlier in the Alpine inversion of the Wessex Basin, during which the entire set of rocks tilted to the north and further slip occurred within the Broken Beds. The slide of a detachment-bounded wedge of rocks and the vertical partition of deformation styles and intensity of strain, all place the Fossil Forest outcrop as a key-field locality for direct observation of tectonic processes analogous to those currently recognized for deformation of the continental crust