Internal Ossa-Morena Zone Ophiolitic Sequences: geodynamic implications for the evolution of the SW branch of the Iberian Variscan Chain

The Internal Ophiolitic Sequences correspond to allochthonous oceanic crust fragments that outcrop near the SW boundary of the Ossa-Morena Zone (Evora-Beja Domain), in an internal position relative to the Beja-Acebuches Ophiolitic Complex. The Internal Ophiolitic Sequences occur as tectonic imbrications or klippen, in the Moura Phyllonitic Complex. Despite deformation and metamorphism (greenschist/amphibolite facies), they still preserve a typical ophiolitic internal stratigraphy identical to the one described for many LOT (“Lherzolitic Ophiolite Type”) ophiolites. Geochemical data indicates that the Internal Ophiolitic Sequences have variable tholeiitic chemistry, transitional between N-MORB and E-MORB. Petrogenetic modelling suggests that the observed geochemical variations reflect both mantle source heterogeneity and partial melting processes. The Internal Ophiolitic Sequences geochemistry indicates that their igneous protholites formed in an anorogenic tectonomagmatic environment, like the ocean ridge basins, without any influence of orogenic components related to subduction mechanisms. These features contrast markedly with those reported for the Beja-Acebuches Ophiolitic Complex, which have been interpreted as representing oceanic crust generated in a “back-arc” setting,. Thus, supporting the existence of two distinct oceanic basins (ocean ridge and back-arc) during the geodynamical evolution of the SW Iberian Variscan Chain. Therefore, the Internal Ophiolitic Sequences in the Ossa-Morena Zone reflect the early oceanization events during the Variscan Orogeny

OFIOLITOS E METAMORFISMO DE ALTA PRESSÃO

Artigo de síntese sobre o limite entre as Zonas de Ossa-Morena e Sul Portuguesa e sobre a sua interpretação como uma zona de sutura varisca

AS REGIÕES CENTRAL E SUL DA ZONA DE OSSA-MORENA

Síntese da estrutura, magmatismo e evolução tectono-estratigráfica da Zona de Ossa-Morena

An Artificial Intelligence Case Based Approach to Motivational Students Assessment in (e)-learning Environments

In the last decades effective teaching and learning and e-learning environments have been performed in order to construct courses jointly with the collaboration with Industry and High-Level Educational Institutions. On another way there are several terminologies that attempt to specify the best teaching and learning methods applied to engineering, from problem-based learning, project-based learning, work-based learning, teamlearning, self-direct learning for example. However motivational studies and motivational scales typically discard uncertainty characteristic in for quantitatively evaluating the different dimensions on student’s motivational assessment in (e)-learning environments. This paper presents a computerized framework grounded on Artificial Intelligence techniques, namely the Case Based Reasoning approach for problem solving, complemented with a Knowledge Representation and Reasoning method that considers unknown, incomplete or even self-contradictory data or knowledge in the motivational student’s assessment

Relicts of Rheic Ocean in Southwest Iberia (Ossa-Morena Zone - Portugal)

The geodynamic evolution of Iberian Peninsula during the Variscan Orogeny is directly related with the Wilson Cycle of Rheic Ocean (Vera, 2004; Dias et al., 2006; Ribeiro et al., 2007). This relationship is underlined by major sutures zones and by several occurrences of high pressure metamorphic rocks (i. e. eclogites and blueschits) and ophiolites terranes (scattered slices) in the Iberian Terrane. The Ossa-Morena Zone (OMZ), the southernmost unit of the Iberian Autochthon Terrane in SW Iberia (Fig. 1), is bounded by two major tectonic lines: the Northern boundary which corresponds to the Tomar-Badajoz-Cordoba Shear Zone (TBCSZ), a Cadomian suture reworked in transpression during the Variscan Orogeny, and the Southern boundary, which corresponds to the South Iberian Variscan Suture Zone (Ribeiro et al., 2007). In the OMZ the Proterozoic basement is separate from the lower Cambrian rocks (felsic volcanics and conglomerates) by a major unconformity that corresponds to the beginning of the Variscan Cycle. The rifting stage is marked by the deposition of lower Cambrian limestones and by bimodal extensional magmatism (Mata & Munhá, 1990). The lower Palaeozoic sequence of OMZ shows strong variations of facies, corresponding to the existence of several local sedimentary basins. This feature is related with a near continuous extensional tectonics regime (Rheic opening), until Silurian times. The Silurian sequence denotes a deep sedimentary environment. At this time, Rheic becomes a wide ocean and the passive margin evolution during lower Palaeozoic is confirmed by the sedimentary record and magmatism chemistry (Mata & Munhá, 1990, Ribeiro et al, 1992; 1997). During lower Devonian the sedimentary record show the existence of tectonic instabilities probably related with the beginning of the Rheic oblique closure. This assumption is supported by the existence of (1) local flysch deposits with lower Devonian age, (2) the occurrence of reworked slices of Silurian rocks within lower Devonian formations and (3) the presence of a Tectonic Accretionary Complex which truncates the autochthonous sequence of OMZ, ranging from Precambrian to upper Silurian/Lower Devonian (Araújo et al, 2005; 2006). During middle to upper Devonian occurs the main tectono-metamorphic event related with the Rheic closure in the southern border of OMZ (Quesada et al., 1994; Fonseca et al., 1999): a subduction/obduction process, with northwards polarity, is responsible by the generation of a flake like geometry and by the occurrence of the Tectonic Accretionary Complex, related with the obduction in the Southern Iberia Variscan Suture, which includes slices of (1) autochthonous rocks, (2) ophiolites and (3) high-pressure rocks (blueschists and eclogites). Also related with the subduction/obduction process occurs the emplacement of the Paired Ophiolite Belt. This ophiolite belt is formed by the Beja-Acebuches Ophiolite Complex (BAOC), an external ophiolite that mark the South Iberian Variscan Suture Zone, and by the Internal Ophiolite Sequence (IOS) (Fonseca, 1995; Pedro, 2004; Ribeiro, 2006; Ribeiro et al., 2007) Also in Devonian times the orogenic magmatism starts with the emplacement of the first rocks of Beja Massif and goes on until upper Carboniferous with the emplacement of widespread intrusive rocks

New Lipschitz–type conditions for uniqueness of solutions of ordinary differential equations

We present some generalized Lipschitz conditions which imply uniqueness of solutions for scalar ODEs. We illustrate the applicability of our results with examples not covered by earlier Lipschitz–type uniqueness testsRodrigo López Pouso and Jorge Rodríguez López were partially supported by grant ED431C 2019/02, Xunta de Galicia (Spain), and by Ministerio de Ciencia y Tecnología (Spain), grant PID2020-113275GB-I00S

The Neoproterozoic-Cambrian transition in Abrantes Region (Central Portugal); Litostratigraphic correlation with the Cambrian Series of Ossa-Morena Zone

Abrantes region presents a litostratigraphic succession with clear similarities with typical sequences of Neoproterozoic-Cambrian transition in Ossa-Morena Zone (OMZ). Classical works have attributed Abrantes entire sequence to Neoproterozoic (e.g. Gonçalves et al., 1979). Detailed characterization, based on fieldwork, of the stratigraphic succession allows to discriminate the presence of litostratigraphic units, attributed to lower Cambrian by correlation with other localities of the OMZ; these units overly Neoproterozoic series. The Cambrian sequence begins with a volcano-sedimentary unit composed by detrital rocks, which includes meta-arkoses, meta-pelites and meta-psamites; some rocks show immature content. The volcanic component is mostly composed by abundant felsic rocks, generally with rhyodacitic composition (Abrantes Felsic Unit). The previous characteristics are common in OMZ, where a clastic unit (often missing), sometimes with felsic volcanics and conglomerates, overlies the Serie Negra succession, previously deformed during the Cadomian orogeny at N1; Nance et al., 2012). Abrantes felsic unit gradually change to a carbonate unit (S. Miguel do Rio Torto Carbonates), with calcitic and dolomitic marbles and interbeded mafic volcanics. This unit can be correlated with a range of carbonated units present in all OMZ (Fig. 1C). These units represent a carbonate platform during lower Cambrian showing the beginning of an oceanization process that culminates with the opening of Rheic in lower Ordovician times (Pedro et al., 2010). The lower Cambrian succession culminates with another volcano-sedimentary complex, poorly outcropping; the clastic succession of this complex is dominated by pelitic rocks, interbedded with bimodal volcanics. The transition between the carbonated sedimentation and the overlying volcano-sedimentary one is gradual. All the previous units have not fossiliferous content, mainly due to the action of metamorphic process, which reaches the amphibolitic facies

Efects of secondary late dolomitization on 87Sr/86Sr isotopic ratio; examples from Ossa-Morena Zone carbonates

The 87Sr/86Sr ratio is usually used in stratigraphy to correlate and even date marine carbonate sedimentation events. The variation of the 87Sr/86Sr isotopic ratio along the geological time scale combined with the fact of this isotopic ratio could be considered uniform in all ocean at a given geological moment, opens a thematic for the investigation and characterization of carbonate sedimentation and as well it sedimentation environment. Therefore, it is important to understand the inherent limitations to the use of this isotope ratio as a method of correlation. For the present work, the Cambrian (or Cambrian attributed) carbonates from the Ossa-Morena Zone were sampled in several sectors. These samples present distinct metamorphic features and their litho-facies were been characterized, as well as the presence of late dolomitization processes (i.e. post-metamorphic). The data show that the late dolomitization processes induce a significant increase of the 87Sr/86Sr ratio, when compared with the calcitic carbonates (marbles and limestones) collected in the same units

Rare occurrence of severe blindness and deafness in Friedreich ataxia: a case report

Background: Friedreich ataxia is the most frequent hereditary ataxia worldwide. Subclinical visual and auditory involvement has been recognized in these patients, with co-occurrence of severe blindness and deafness being rare. Case report: We describe a patient, homozygous for a 873 GAA expansion in the FXN gene, whose first symptoms appeared by the age of 8. At 22 years-old he developed sensorineural deafness, and at 26 visual impairment. Deafness had a progressive course over 11 years, until a stage of extreme severity which hindered communication. Visual acuity had a catastrophic deterioration, with blindness 3 years after visual impairment was first noticed. Audiograms documented progressive sensorineural deafness, most striking for low frequencies. Visual evoked potentials disclosed bilaterally increased P100 latency. He passed away at the age of 41 years old, at a stage of extreme disability, blind and deaf, in addition to the complete phenotype of a patient with Friedreich ataxia of more than 30 years duration. Discussion: Severe vision loss and extreme deafness has been described in very few patients with Friedreich ataxia. Long duration, severe disease and large expanded alleles may account for such an extreme phenotype; nonetheless, the role of factors as modifying genes warrants further investigation in this subset of patients.info:eu-repo/semantics/publishedVersio

A Psychometrics Approach to Entropy

Today's metrics for women housework work (WHW) operate at a quantitative level, specifically measuring time expended on a task and the totality of tasks women perform, not considering that it is a process that is eminently qualitative in nature. To fill this gap, an innovative framework for representing and thinking about big data or knowledge is presented, borrowing from the field of artificial intelligence the methods and methodologies for problem solving, from logic programming the artifacts to improve practice through theory, and from the laws of thermodynamics the construct of entropy, interpreted as the degree of disorder or unpredictability in a system, a principle that may be used to understand system evolution. Last but not least, it also considers the relationship among the disciplines of psychometrics and psychology or sociology (i.e., how certain psychological and sociological concepts such as cognition, knowledge and personality affect WHW satisfaction)