Sistema de secagem solar para frutos tropicais e modelagem da secagem de banana em um secador de coluna estática

In this study were projected, built and tested an electric solar dryer consisting of a solar collector, a drying chamber, an exhaust fan and a fan to promote forced hot air convection. Banana drying experiments were also carried out in a static column dryer to model the drying and to obtain parameters that can be used as a first approximation in the modeling of an electric solar dryer, depending on the similarity of the experimental conditions between the two drying systems. From the banana drying experiments conducted in the static column dryer, we obtained food weight data as a function of aqueous concentration and temperature. Simplified mathematical models of the banana drying were made, based on Fick s and Fourier s second equations, which were tested with the experimental data. We determined and/or modeled parameters such as banana moisture content, density, thin layer drying curves, equilibrium moisture content, molecular diffusivity of the water in banana DAB, external mass transfer coefficient kM, specific heat Cp, thermal conductivity k, latent heat of water evaporation in the food Lfood, time to heat food, and minimum energy and power required to heat the food and evaporate the water. When we considered the shrinkage of radius R of a banana, the calculated values of DAB and kM generally better represent the phenomenon of water diffusion in a solid. The latent heat of water evaporation in the food Lfood calculated by modeling is higher than the latent heat of pure water evaporation Lwater. The values calculated for DAB and KM that best represent the drying were obtained with the analytical model of the present paper. These values had good agreement with those assessed with a numeric model described in the literature, in which convective boundary condition and food shrinkage are considered. Using parameters such as Cp, DAB, k, kM and Lfood, one can elaborate the preliminary dryer project and calculate the economy using only solar energy rather than using solar energy along with electrical energy

Estudo da secagem do pedúnculo do caju em sistemas convencional e solar: modelagem e simulação do processo

This work aims to study the drying of cashew-nut pulp with different lay-out of dryers using conventional and solar energy. It concerns with the use of exceeding of the regional raw material and the suitable knowledge for the applicability of the drying systems as pathway for food conservation. Besides, it used renewable sources as solar energy to dry these agroindustrial products. Runs were carried out using a conventional tray-dryer with temperature, air velocity control and cashew slice thickness of 55°C, 65°C, 75°C; 3.0; 4.5, 6.0 m s-1; 1.0; 1.5 and 2.0 cm, respectively, in order to compare the studied systems. To evaluate the conventional tray-dryer, it was used a diffusional model of 2nd Fick´s law, where the drying curves were quite well fitted to an infinite flat plate design. For the drying runs where the room temperature had no control, it was developed a phenomenological-mathematical model for the solar dryer with indirect radiation under natural and forced convection based on material and energy balances of the system. Besides, it was carried out assays in the in natura as well as dehydrated, statistic analysis of the experimental drying data, sensorial analysis of the final dry product and a simplified economical analysis of the systems studied

Determinacão do período orbital de sistemas binários clipsantes

In this work is presented a new method for the determination of the orbital period (Porb) of eclipsing binary systems based on the wavelet technique. This method is applied on 18 eclipsing binary systems detected by the CoRoT (Convection Rotation and planetary transits) satellite. The periods obtained by wavelet were compared with those obtained by the conventional methods: box Fitting (EEBLS) for detached and semi-detached eclipsing binaries; and polynomial methods (ANOVA) for contact binary systems. Comparing the phase diagrams obtained by the different techniques the wavelet method determine better Porb compared with EEBLS. In the case of contact binary systems the wavelet method shows most of the times better results than the ANOVA method but when the number of data per orbital cicle is small ANOVA gives more accurate results. Thus, the wavelet technique seems to be a great tool for the analysis of data with the quality and precision given by CoRoT and the incoming photometric missions.

Evolução da excentricidade dos sistemas binários com componente evoluída

On this study we have revisited the predicted tidal circularization theory in close binary systems with a evolved component. Close binaries suffer tidal interactions that tend to synchronize periods and circularize the orbits (Zahn 1977, 1989, 1992). According to Zahn s theory we compute the integral that give us the variation of the eccentricity in a binary under the influence of tidal force and we compare the integral results with new observations for 260 binary systems with orbital solutions. Our results confirm the success of the Zahn s theory with a new data and new stellar evolutionary models, on the other hand, our results points to the need for a better description of the role of convection on this theory

Estudo sistemático de estrelas variáveis na era dos grandes surveys

The interest in the systematic analysis of astronomical time series data, as well as development in astronomical instrumentation and automation over the past two decades has given rise to several questions of how to analyze and synthesize the growing amount of data. These data have led to many discoveries in the areas of modern astronomy asteroseismology, exoplanets and stellar evolution. However, treatment methods and data analysis have failed to follow the development of the instruments themselves, although much effort has been done. In present thesis, we propose new methods of data analysis and two catalogs of the variable stars that allowed the study of rotational modulation and stellar variability. Were analyzed the photometric databases fromtwo distinctmissions: CoRoT (Convection Rotation and planetary Transits) and WFCAM (Wide Field Camera). Furthermore the present work describes several methods for the analysis of photometric data besides propose and refine selection techniques of data using indices of variability. Preliminary results show that variability indices have an efficiency greater than the indices most often used in the literature. An efficient selection of variable stars is essential to improve the efficiency of all subsequent steps. Fromthese analyses were obtained two catalogs; first, fromtheWFCAMdatabase we achieve a catalog with 319 variable stars observed in the photometric bands Y ZJHK. These stars show periods ranging between ∼ 0, 2 to ∼ 560 days whose the variability signatures present RR-Lyrae, Cepheids , LPVs, cataclysmic variables, among many others. Second, from the CoRoT database we selected 4, 206 stars with typical signatures of rotationalmodulation, using a supervised process. These stars show periods ranging between ∼ 0, 33 to ∼ 92 days, amplitude variability between ∼ 0, 001 to ∼ 0, 5 mag, color index (J - H) between ∼ 0, 0 to ∼ 1, 4 mag and spectral type CoRoT FGKM. The WFCAM variable stars catalog is being used to compose a database of light curves to be used as template in an automatic classifier for variable stars observed by the project VVV (Visible and Infrared Survey Telescope for Astronomy) moreover it are a fundamental start point to study different scientific cases. For example, a set of 12 young stars who are in a star formation region and the study of RR Lyrae-whose properties are not well established in the infrared. Based on CoRoT results we were able to show, for the first time, the rotational modulation evolution for an wide homogeneous sample of field stars. The results are inagreement with those expected by the stellar evolution theory. Furthermore, we identified 4 solar-type stars ( with color indices, spectral type, luminosity class and rotation period close to the Sun) besides 400 M-giant stars that we have a special interest to forthcoming studies. From the solar-type stars we can describe the future and past of the Sun while properties of M-stars are not well known. Our results allow concluded that there is a high dependence of the color-period diagram with the reddening in which increase the uncertainties of the age-period realized by previous works using CoRoT data. This thesis provides a large data-set for different scientific works, such as; magnetic activity, cataclysmic variables, brown dwarfs, RR-Lyrae, solar analogous, giant stars, among others. For instance, these data will allow us to study the relationship of magnetic activitywith stellar evolution. Besides these aspects, this thesis presents an improved classification for a significant number of stars in the CoRoT database and introduces a new set of tools that can be used to improve the entire process of the photometric databases analysis

Ofensiva do Capital e Desmobilização das Forças do Trabalho: As Estratégias Gerenciais Burguesas para a Desarticulação das Classes Trabalhadoras

The problematic that gives shape to this research is the question of the historical process of demobilization of the movement of the working classes in your accented contemporary moment. Their object of study, however, and that it particularizes, it relates to a portion this problematic; it relates to set of determinations that comprise a broader set of determinations of this historical process: it is a set of determinations forged and mediated by bourgeois strategies of management for the conformation of the circumstances necessary for the domination and for the conduct of labor force on operations in work processes for the production of surplus value. What we investigated are, because, the strategies of disarticulation that the bourgeoisie utilizes, under the mantle of subsidies conceptual and interventive of its management of work processes and the sieve of class struggles, to obstruct the union of workers; hamper the movements proletarians. Managerial strategies that intentionally or unintentionally, instill in the social relations of production means to produce and reproduce, activate and reactivate conditions of incitement of individualism and competition between the workers themselves. We shall see, thus, by analyzing means, centrally, from some of the fundamentals of disarticulation in the managerial strategies bourgeois and some of the fundamental strategies of management bourgeois hegemonized with the restructuring productive of 1970, that the disarticulation, and also the demobilization, is a concrete condition, is an objective condition, that is beyond a question that can be "solved" only by enlightenment cognitive, only by formation criticism intellectual. In everyday of the work spaces permeated by managerial strategies bourgeois there elements, then, operating as a material force putting difficulties important for the articulation of the workers, the solidarity of the proletariat; elements that constitute obstacle significant to an awareness of class and belonging; elements act in favor of the atomization of the worker - even if engenders, in the same process, as a contradiction, potentiality of resistance and fight the forces of labor

Caracterização tectono-estratigráfica da sequência transicional na sub-bacia de Sergipe

This thesis deals with the tectonic-stratigraphic evolution of the Transitional Sequence in the Sergipe Sub-basin (the southern segment of the Sergipe-Alagoas Basin, Northeast Brazil), deposited in the time interval of the upper Alagoas/Aptian stage. Sequence boundaries and higher order internal sequences were identified, as well as the structures that affect or control its deposition. This integrated approach aimed to characterize the geodynamic setting and processes active during deposition of the Transitional Sequence, and its relations with the evolutionary tectonic stages recognized in the East Brazilian Margin basins. This subject addresses more general questions discussed in the literature, regarding the evolution from the Rift to the Drift stages, the expression and significance of the breakup unconformity, the relationships between sedimentation and tectonics at extensional settings, as well as the control on subsidence processes during this time interval. The tectonic-stratigraphic analysis of the Transitional Sequence was based on seismic sections and well logs, distributed along the Sergipe Sub-basin (SBSE). Geoseismic sections and seismic facies analysis, stratigraphic profiles and sections, were compiled through the main structural blocks of this sub-basin. These products support the depositional and tectonic-stratigraphic evolutionary models built for this sequence. The structural analysis highlighted similarities in deformation styles and kinematics during deposition of the Rift and Transitional sequences, pointing to continuing lithospheric extensional processes along a NW trend (X strain axis) until the end of deposition of the latter sequence was finished by the end of late Aptian. The late stage of extension/rifting was marked by (i) continuous (or as pulses) fault activity along the basin, controling subsidence and creation of depositional space, thereby characterizing upper crustal thinning and (ii) sagstyle deposition of the Transitional Sequence at a larger scale, reflecting the ductile stretching and thinnning of lower and sub crustal layers combined with an increasing importance of the thermal subsidence regime. Besides the late increments of rift tectonics, the Transitional Sequence is also affected by reactivation of the border faults of SBSE, during and after deposition of the Riachuelo Formation (lower section of the Transgressive Marine Sequence, of Albian age). It is possible that this reactivation reflects (through stress propagation along the newlycreated continental margin) the rifting processes still active further north, between the Alagoas Sub-basin and the Pernambuco-Paraíba Basin. The evaporitic beds of the Transitional Sequence contributed to the development of post-rift structures related to halokinesis and the continental margin collapse, affecting strata of the overlying marine sequences during the Middle Albian to the Maastrichtian, or even the Paleogene time interval. The stratigraphic analysis evidenced 5 depositional sequences of higher order, whose vertical succession indicates an upward increase of the base level, marked by deposition of continental siliciclastic systems overlain by lagunar-evaporitic and restricted marine systems, indicating that the Transitional Sequence was deposited during relative increase of the eustatic sea level. At a 2nd order cycle, the Transitional Sequence may represent the initial deposition of a Transgressive Systems Tract, whose passage to a Marine Transgressive Sequence would also be marked by the drowning of the depositional systems. At a 3rd order cycle, the sequence boundary corresponds to a local unconformity that laterally grades to a widespread correlative conformity. This boundary surface corresponds to a breakup unconformity , being equivalent to the Pre-Albian Unconformity at the SBSE and contrasting with the outstanding Pre-upper Alagoas Unconformity at the base of the Transitional Sequence; the latter is alternatively referred, in the literature, as the breakup unconformity. This Thesis supports the Pre-Albian Unconformity as marker of a major change in the (Rift-Drift) depositional and tectonic setting at SBSE, with equivalent but also diachronous boundary surfaces in other basins of the Atlantic margin. The Pre-upper Alagoas Unconformity developed due to astenosphere uplift (heating under high lithospheric extension rates) and post-dates the last major fault pulse and subsequent extensive block erosion. Later on, the number and net slip of active faults significantly decrease. At deep to ultra deep water basin segments, seaward-dipping reflectors (SDRs) are unconformably overlain by the seismic horizons correlated to the Transitional Sequence. The SDRs volcanic rocks overly (at least in part) continental crust and are tentatively ascribed to melting by adiabatic decompression of the rising astenospheric mantle. Even though being a major feature of SBSE (and possibly of other basins), the Pre-upper Alagoas Unconformity do not correspond to the end of lithospheric extension processes and beginning of seafloor spreading, as shown by the crustal-scale extensional structures that post-date the Transitional Sequence. Based on this whole context, deposition of the Transitional Sequence is better placed at a late interval of the Rift Stage, with the advance of an epicontinental sea over a crustal segment still undergoing extension. Along this segment, sedimentation was controled by a combination of thermal and mechanical subsidence. In continuation, the creation of oceanic lithosphere led to a decline in the mechanical subsidence component, extension was transferred to the mesoceanic ridge and the newly-formed continental margin (and the corresponding Marine Sequence) began to be controlled exclusively by the thermal subsidence component. Classical concepts, multidisciplinary data and new architectural and evolutionary crustal models can be reconciled and better understood under these lines

Geologia, Geocronologia, Geoquímica e Petrogênese das Rochas Ígneas Cretácicas da Província Magmática do Cabo e suas Relações com as Unidades Sedimentares da Bacia de Pernambuco (NE do Brasil)

The area studied forms a thin NNE-directed belt situated south of Recife town (Pernambuco state), northeastern Brazil. Geologically, it comprises the Pernambuco Basin (PB), which is limited by the Pernambuco Lineament to the north, the Maragogi high to the south and the Pernambuco Alagoas massif to the west, all of them with Precambrian age. This thesis reports the results obtained for the Cabo Magmatic Province (CMP), aiming the characterization of the geology, stratigraphy, geochronology, geochemistry and petrogenesis of the Cretaceous igneous rocks presented in the PB. The PB is composed of the Cabo Formation (rift phase) at the base (polymictic conglomerates, sandstones, shales), an intermediate unit, the Estiva Formation (marbles and argillites), and, at the top, the Algodoais Formation (monomictic conglomerates, sandstones, shales). The CMP is represented by trachytes, rhyolites, pyroclastics (ignimbrites), basalts / trachy-andesites, monzonites and alkali-feldspar granite, which occur as dykes, flows, sills, laccoliths and plugs. Field observations and well descriptions show that the majority of the magmatic rocks have intrusive contacts with the Cabo Formation, although some occurrences are also suggestive of synchronism between volcanism and siliciclastic sedimentation. 40Ar/39Ar and zircon fission tracks for the magmatic rocks indicate an average age of 102 r 1 Ma for the CMP. This age represents an expressive event in the province and is detected in all igneous dated materials. It is considered as a minimum age (Albian) for the magmatic episode and the peak of the rift phase in the PB. The 40Ar/39Ar dates are about 10-14 Ma younger than published palynologic ages for this basin. Geochemically, the CMP may be divided in two major groups; i) a transitional to alkaline suite, constituted by basalts to trachy-andesites (types with fine-grained textures and phenocrysts of sanidine and plagioclase), trachytes (porphyrytic texture, with phenocrysts of sanidine and plagioclase) and monzonites; ii) a alkaline suite, highly fractionated, acidic volcano-plutonic association, formed by four subtypes (pyroclastic flows ignimbrites, fine-to medium-grained rhyolites, a high level granite, and later rhyolites). These four types are distinguished essentially by field aspects and petrographic and textural features. Compatible versus incompatible trace element concentrations and geochemical modeling based on both major and trace elements suggest the evolution through low pressure fractional crystallization for trachytes and other acidic rocks, whereas basalts / trachy-andesites and monzonites evolved by partial melting from a mantle source. Sr and Nd isotopes reveal two distinct sources for the rocks of the CMP. Concerning the acidic ones, the high initial Sr ratios (ISr = 0.7064-1.2295) and the negative HNd (-0.43 to -3.67) indicate a crustal source with mesoproterozoic model ages (TDM from 0.92 to 1.04 Ga). On the other hand, the basic to intermediate rocks have low ISr (0.7031-0.7042) and positive HNd (+1.28 to +1.98), which requires the depleted mantle as the most probable source; their model ages are in the range 0.61-0.66 Ga. However, the light rare earth enrichment of these rocks and partial melting modeling point to an incompatible-enriched lherzolitic mantle with very low quantity of garnet (1-3%). This apparent difference between geochemical and Nd isotopes may be resolved by assuming that the metasomatizing agent did not obliterate the original isotopic characteristics of the magmas. A 2 to 5% partial melting of this mantle at approximately 14 kbar and 1269oC account very well the basalts and trachy-andesites studied. By using these pressure and temperatures estimates for the generation of the basaltic to trachy-andesitic magma, it is determined a lithospheric stretching (E) of 2.5. This E value is an appropriated estimate for the sub-crustal stretching (astenospheric or the base of the lithosphere?) region under the Pernambuco Basin, the crustal stretching probably being lower. The integration of all data obtained in this thesis permits to interpret the magmatic evolution of the PB as follows; 1st) the partial melting of a garnet-bearing lherzolite generates incompatible-enriched basaltic, trachy-andesitic and monzonitic magmas; 2nd) the underplating of these basaltic magmas at the base of the continental crust triggers the partial melting of this crust, and thus originating the acidic magmas; 3rd) concomitantly with the previous stage, trachytic magmas were produced by fractionation from a monzonitic to trachy-andesitic liquid; 4th) the emplacement of the several magmas in superficial (e.g. flows) or sub-superficial (e.g. dykes, sills, domes, laccoliths) depths was almost synchronically, at about 102 r 1 Ma, and usually crosscutting the sedimentary rocks of the Cabo Formation. The presence of garnet in the lherzolitic mantle does not agree with pressures of about 14 kbar for the generation of the basaltic magma, as calculated based on chemical parameters. This can be resolved by admitting the astenospheric uplifting under the rift, which would place deep and hot material (mantle plume?) at sub-crustal depths. The generation of the magmas and their subsequent emplacement would be coupled with the crustal rifting of the PB, the border (NNE-SSW directed) and transfer (NW-SE directed) faults serving as conduits for the magma emplacement. Based on the E parameter and the integration of 40Ar/39Ar and palynologic data it is interpreted a maximum duration of 10-14 Ma for the rift phase (Cabo Formation clastic sedimentation and basic to acidic magmatism) of the PB

Lítio e rotação nas estrelas análogas solares: análise teórica das observações

The projected rotational velocity together with lithium abundance and the onset of the dilution by the deepening in mass of the convective envelope provide a key tool to investigate the so far poorly understood processes at work in stellar interiors of solar-analog stars. To investigate the link between abundances, convection and rotational velocities in solar-analog G dwarf stars, we study a bona fide sample of 118 selected solar-analog G dwarf stars presenting measured lithium abundances, rotational velocities, and fundamental parameters together with computed evolutionary tracks (Toulouse-Geneva code) for a range of stellar masses around 1 M and metallicity consistent with the solar-analog range. The aim of this work is to build up an evolution of lithium and rotation as a function of stellar age, mass, effective temperature, and convection. We analyze the evolutionary status of the sample of 118 solar-analog G dwarf in the HR diagram based on Hipparcos data and using a grid of stellar models in the effective temperature and mass range of the solar-analog stars. We discuss the deepening (in mass) of the convective envelope and the influence on the Li abundances and projected rotational velocities. We determined the stellar mass and the mass of the convective envelope for a bona fide sample of 118 selected solar-analog G dwarf and checked the evolutionary link between the rotational velocity, lithium abundance, and the deepening of the convective envelope. Fast rotators (vsini 6 km s��1) are also stars with high Li content. Slow rotators present a wide range of values of log n(Li). Our results shed new light on the lithium and rotational behavior in G dwarf stars. We confirmed the presence of a large Li abundance spread among the solar-analog stars and concluded that the solar twins probably share a similar mixing history with the Sun

Investigando o campo magnético das estrelas análogas e gêmeas solares através da espectropolarimetria

This study proposes an observing program focused on the investigation of the stellar magnetism and dynamo evolution in cool active solar-like stars. More mainly in the solar analogs and twins. Observations of stars of our base were carried out with two spectropolarimeter (ESPaDOnS@CFHT and NARVAL@TBL). The analyse of stars in stage different allows an understanding of the dependence of magnetic activity on basic stellar parameters such as rotation, mass, age and depth of the convection zone. This study provides measures necessary for testing dynamo theories. The 65 targets for this project are solar type stars with mass spanning from 0:9 M=Mfi 1:075 solar masses and at different evolutionary stages. Our two main science objectives were, (i) To determine how the magnetic field evolved from the ZAMS to the TO (turn off) for stars with 0:9 M=Mfi 1:075; (ii) To determine the impact of convective depth and rotation on magnetic of cool stars of solar type. The main result from this study was the characterization of the dependence of magnetic field intensity as function of age, Rossby number and the convective zone deepening. This context, the availability of ESPaDOnS and NARVAL opens an exceptional possibility to study the magnetic properties of Sun-like stars by means of spectropolarimetric observations

Estimativa de espessura crustal na Província Borborema (NE/Brasil) através de função do recpetor

Crustal thickness and VP/VS estimates are essential to the studies of subsurface geological structures and also to the understanding of the regional tectonic evolution of a given area. In this dissertation, we use the Langston´s (1979) Receiver Function Method using teleseismic events reaching the seismographic station with angles close to the vertical. In this method, the information of the geologic structures close to the station is isolated so that effects related to the instrument response and source mechanics are not present. The resulting time series obtained after the deconvolution between horizontal components contains the larger amplitude referring to the P arrival, followed by smaller arrival caused by the reverberation and conversion of the P-wave at the base of the crust. We also used the HK-Stacking after Zhu & Kanamori (2000) to obtain crustal thickness and Vp/VS estimates. This method works stacking receiver functions so that the best estimates of crustal thickness and Vp/VS are found when the direct P, the Ps wave and the first multiple are coherently stacked. We used five broadband seismographic stations distributed over the Borborema Province, NE Brazil. Crustal thickness and Vp/VS estimates are consistent with the crust-mantle interface obtained using gravity data. We also identified crutal thickening in the NW portion of the province, close to Sobral/CE. Towards the center-north portion of the province, there is an evident crustal thinning which coincides with a geological feature consisting of an alignment of sedimentary basins known as the Cariris-Potiguar trend. Towards the NE portion of the province, in Solânea/PB and Agrestina/PE regions, occurs a crustal thickening and a systematic increase in the VP/VS values which suggest the presence of mafic rocks in the lower crust also consistent with the hypothesis of underplating in the region

Petrologia do magmatismo tardi-brasiliano no Maciço São José de Campestre(RN/PB), com ênfase no Plúton Alcalino Caxexa

The area studied is located on the north-easternmost portion of the Borborema Province, on the so-called São José de Campestre Massif, States of RN and PB, Northeast Brazil. Field relations and petrographic, geochemical and isotope data permitted the separation of five suites of plutonic rocks: alkali-feldspar granite (Caxexa Pluton), which constitutes the main subject of this dissertation, amphibole-biotite granite (Cabeçudo Pluton), biotite microgranite, gabbronorite to monzonite (Basic to Intermediate Suite) and aluminous granitoid. The Caxexa Pluton is laterally associated to the Remígio Pocinhos Shear Zone, with its emplacement along the mylonitic contact between the gneissic basement and the micashists. This pluton corresponds to a syntectonic intrusion elongated in the N-S direction, with about 50 km2 of outcropping surface. It is composed exclusively of alkali-feldspar granites, having clinopyroxene (aegirine-augite and hedenbergite), andradite-rich garnet, sphene and magnetite. It is classified geochemically as high silica rocks (>70 % wt), metaluminous to slightly peraluminous (normative corindon < 1%), with high total alkalis (>10% wt), Sr, iron number (#Fe=90-98) and agpaitic index (0.86-1.00), and positive europium anomaly. The Cabeçudo Pluton is composed of porphyritic rocks, commonly containing basic to intermediate magmatic enclaves often with mingling and mixing textures. Petrographically, it presents k-feldspar and plagioclase phenocrysts as the essential minerals, besides the accessories amphibole, biotite, sphene and magnetite. It is metaluminous and shows characteristics transitional between the calc-alkaline and alkaline series (or monzonitic subalkaline). Its REE content is greater than those ones of the Caxexa Pluton and biotite microgranite, and all spectra have negative europium anomalies. The biotite microgranites occur mainly on the central and eastern portion of the mapped area, as dykes and sheets with decimetric thickness, hosted principally in orthogneisses and micashists. Their field relationships as regards the Caxexa and Cabeçudo plutons suggested that they are late-tectonic intrusions. They are typically biotite granites, having also sphene, amphibole, allanite, opaques and zircon in the accessory assemblage. Geochemically they can be distinguished from the porphyritic types because the biotite microgranites are more evolved, peraluminous, and have more fractionated REE spectra. The Basic to Intermediate rocks form a volumetrically expressive elliptical, kilometric scale body on the Southeast, as well as sheets in micashists. They are classified as gabbronorites to monzonites, with the two pyroxenes and biotite, besides subordinated amounts of amphibole, sphene, ilmenite and allanite. These rocks do not show a well-defined geochemical trend, however they may possibly represent a monzonitic (shoshonitic) series. Their REE spectra have negative europium anomalies and REE contents greater than the other suites. The aluminous granitoids are volumetrically restricted, and have been observed in close association with migmatised micashists bordering the gabbronorite pluton. They are composed of almandine-rich garnet, andalusite, biotite and muscovite, and are akin to the peraluminous suites. Rb-Sr (whole rock) and Sm-Nd (whole-rock and mineral) isotopes furnished a minimum estimate of the crystallization (578±14 Ma) and the final resetting age of the Rb-Sr system (536±4 Ma) in the Caxexa Pluton. The aluminous granitoid has a Sm-Nd garnet age similar to that one of the Caxexa Pluton, that is 574±67 Ma. The strong interaction of shear bands and pegmatite dykes favoured the opening of the Rb-Sr system for the Caxexa Pluton and biotite microgranite. The amphibole-plagioclase geothermometer and the Al-in amphibole geobarometer indicate minimum conditions of 560°C and 7 kbar for the Cabeçudo Pluton, 730°C and 6 kbar for the microgranite and 743°C and 5 kbar for the basic to intermediate suite. The Zr saturation geothermometer reveals temperatures of respectively 855°C, 812°C and 957°C for those suites, whereas the Caxexa Pluton shows temperatures of around 757°C. The Caxexa, Cabeçudo and microgranites suites crystallized under high fO2 (presence of magnetite). On the other hand, the occurrence of ilmenite suggests less oxidant conditions in the basic to intermediate suite. Field relations demonstrate the intrusive character of the granitoids into a tectonically relatively stable continental crust. This is corroborated by petrographic and geochemical data, which suggest a late- or post-collisional tectonic context. It follows that the generation and emplacement of those granitoid suites is related to the latest events of the Brasiliano orogeny. Finally, the relationships between eNd (600 Ma), TDM (Nd) and initial Sr isotope ratio (ISr) do not permit to define the precise sources of the granitoids. Nevertheless, trace element modelling and isotopic comparisons suggest the participation of the metasomatised mantle in the generation of these suites, probably modified by different degrees of crustal contamination. In this way, a metasomatised mantle would not be a particular characteristic of the Neoproterozoic lithosphere, but a remarkable feature of this portion of the Borborema Province since Archaean and Paleoproterozoic times.

Petrologia dos granitóides brasilianos associados à zona de cisalhamento Remígio-Pocinhos(PB)

The Brasiliano Cycle in the Seridó Belt (NE Brazil) is regarded mostly as a crustal reworking event, characterized by transcurrent or transpressional shear zones which operated under high temperature and low pressure conditions. In the eastern domain of this belt- the so-called São José de Campestre Massif (SJCM), a transtensional deformation regime is evidenced by extensional components or structures associated to the strikeslip shear zones. The emplacement of the Neoproterozoic Brasiliano granitoids is strongly controled by these discontinuities. Located in the southern border of the SJCM, the Remígio-Pocinhos shear zone (RPSZ) displays, in its northern half, top to the SW extensional movement which progressively grade, towards its southern half, to a dextral strike-slip kinematics, defining a negative semi-flower structure. This shear zone is overprinted upon allocthonous metasediments of the Seridó Group and an older gneiss-migmatite complex, both of which containing metamorphic parageneses from high amphibolite to granulite facies (the latter restricted to the strike-slip zone), defining the peak conditions of deformation. Several granitoid plutons are found along this structure, emplaced coeval with the shearing event. Individually, such bodies do not exceed 30 km2 in outcropping area and are essentially parallel to the trend of the shear zone. Petrographic, textural and geochemical data allow to recognize five different granitoid suites along the RPSZ: porphyritic granites (Serra da Boa Vista and Jandaíra), alkaline granites (Serra do Algodão and Serra do Boqueirão) and medium to coarse-grained granites (Olivedos) as major plutons, while microgranite and aluminous leucogranite sheets occur as minor intrusions. The porphyritic granites are surrounded by metasediments and present sigmoidal or en cornue shapes parallel to the trend of the RPSZ, corroborating the dextral kinematics. Basic to intermediate igneous enclaves are commonly associated to these bodies, frequently displaying mingling textures with the host granitoids. Compositionally these plutons are made up by titanite-biotite monzogranites bearing amphibole and magnetite; they are peraluminous and show affinities to the monzonitic, subalkaline series. Peraluminous, ilmenite-bearing biotite monzogranites and titanite-biotite monzogranites correspond, respectivally, to the Olivedos pluton and the microgranites. The Olivedos body is hosted by metasediments, while the microgranites intrude the gneiss-migmatite complex. Being highly evolved rocks, samples from these granites plot in the crustal melt fields in discrimination diagrams. Nevertheless, their subtle alignment also looks consistent with a monzonitic, subalkaline affinity. These chemical parameters make them closer to the I-type granites. Alkaline, clearly syntectonic granites are also recognized along the RPSZ. The Serra do Algodão and Serra do Boqueirão bodies display elongated shapes parallel to the mylonite belt which runs between the northern, extensional domain and the southern strike-slip zone. The Serra do Algodão pluton shows a characteristic isoclinal fold shape structure. Compositionally they encompass aegirine-augite alkali-feldspar granites and quartz-bearing alkaline syenite bearing garnet (andradite) and magnetite plus ilmenite as opaque phases. These rocks vary from meta to peraluminous, being correlated to the A-type granites. Aluminous leucogranites bearing biotite + muscovite ± sillimanite ± garnet (S-type granites) are frequent but not volumetrically important along the RPSZ. These sheet-like bodies may be folded or boudinaged, representing partial melts extracted from the metasediments during the shear zone development. Whole-rock Rb-Sr isotope studies point to a minimum 554��10 Ma age for the crystalization of the porphyritic granites. The alkaline granites and the Olivedos granite produced ca. 530 Ma isochrons which look too young; such values probably represent the closure of the Rb-Sr radiometric clock after crystallization and deformation of the plutons, at least 575 Ma ago (Souza et al. 1998). The porphyritic and the alkaline granites crystallized under high oxygen fugacity conditions, as shown by the presence of both magnetite and hematite in these rocks. The presence of ilmenite in the Olivedos pluton suggests less oxidizing conditions. Amphibole and amphibole-plagioclase thermobarometers point to minimum conditions, around 750°C and 6 Kbars, for the crystallization of the porphyritic granites. The zirconium geothermometer indicates higher temperatures, in the order of 800°C, for the porphyritic granites, and 780°C for the Olivedos pluton. Such values agree with the thermobarometric data optained for the country rocks (5,7 Kbar and 765°C; Souza et al. 1998). The geochemical and isotope data set point to a lower crustal source for the porphyritic and the alkaline granites. Granulite facies quartz diorite to tonalite gneisses, belonging or akin to the gneiss-migmatite complex, probably dominate in the source regions. In the case of the alkaline rocks, subordinate contributions of mantle material may be present either as a mixing magma or as a previously added component to the source region. Tonalite to granodiorite gneisses, with some metasedimentary contribution, may be envisaged for the Olivedos granite. The diversity of granitoid rocks along the RPSZ is explained by its lithospheric dimension, allowing magma extraction at different levels, from the middle to lower crust down to the mantle. The presence of basic to intermediate enclaves, associated to the porphyritic granites, confirm the participation of mantle components in the magma extraction system along the RPSZ. This mega-structure is part of the network of Brasiliano-age shear zones, activated by continental collision and terrane welding processes at the end of the Neoproterozoic

Mecanismos de alojamento de magmas granitóides :exemplo do plúton de Japi(RN)

This dissertation describes the igneous suites of the Japi granitoid pluton, intrusive in the Paleoproterozoic gneiss-migmatite complex of the eastern domain of the Seridó Belt, northeastern Brazil. Field relations show that the pluton is affected by strong deformation associated to the Brasiliano orogeny (known as the D3 phase) , with a NW-trending extensionalleft-hand senestral shear zone (the Japi Shear Zone, JSZ) bordering the intrusive body to the west. Four plutonic suites are found in the main pluton and as satellyte intrusions, besides Iate pegmatite and pink leucogranites. An alkaline granitoid suite, dominated by syenogranites bearing sodic augite (and subordinate hornblende), define a main elliptical intrusion. In its northern part, this intrusion is made up by concentric sheets, contrasting with a smaller rounded stock to the south. These granites display a pervasive solid-state S>L fabric developed under high T conditions, characterized by plastic deformation of quartz and feldspar. It is especially, developed along the border of the pluton, with inward dips. A regular magmatic layering is present sometimes, parallel to the tectonic foliation. The syntectonic emplacement as regards to the Brasiliano (D3) event is indicated by the common occurrence of dykes and sheets along transtensional or extensional sites of the major structure. Field relations attest to the early emplacement of the alkaline granites as regards to the other suites. A basic-to-intermediate suite occurs as a western satellyte body and occupying the southern tail of the main alkaline pluton. It comprises a wide variety of compositional terms, including primitive gabbros and gabbro-norites, differentiated to monzonitic intermediate facies containing amphibole and biotite as their main mafic phases. These rocks display transitional high-K calc-alkaline to shoshonitic affinities. Porphyritic monzogranite suítes commonly occur as dykes and minor intrusives, isolated or associated with the basic-tointermediate rocks. In the latter case, magma mingling and mixing features attest that these are contemporaneous igneous suites. These granites show K-feldspar phenocrysts and a hornblende+biotite+titanite assemblage, displaying subalkaline/monzonitic geochemical affinities. Both suites exhibit SL magmatic fabrics overprinting or transitional to solid-state D3 deformation related to the JSI. Chemical data clearly show that they are related to different parental magmas. Finally, a microgranite suite occurs along a few topographic ridges paralell to the JSI. It comprises dominantly granodiorites with a mineralogy similar to the one of the porphyritic granitoids. However, discriminant diagrams show their distinct calc-alkaline affinity. The granodiorites display an essencially magmatic fabric, even though an incipient D3 solid-state structure may be developed along the JSI. Intrusion relationships with the previous suites, as well as regards to the D3 structures, point to their Iate emplacement. All these suites are intrusive in a Paleoproterozoic, high-grade gneiss-migmatite complex affected by two previous deformation phases (D1, D2). The fabrics associated with these earlier events are folded and overprinted by the younger D3 structures along the JSZ. The younger deformation is characterized by NE-dipping foliations and N/NE-plunging stretching lineations. In the JSZ northern termination the foliation acquires an ENE orientation, containing a stretching lineation plunging to the south. Symmetric kinematic cri teria developed at this site confirms the transpressional termination of the JSZ, as also shown by orthorrombic quartz c-axis patterns. E-W-trending d extra I shear zones developed in the central part of the JSZ are interpreted as antithetic structures associated to the transtensional deformation along the JSZ. This is consistent with its extensional-transcurrent kinematics and a flat-and-ramp geometry at depth, as shown by gravimetric data. The lateral displacement of the negative residual Bouguer anomalies, as regards to the main outcropping alkaline pluton, may be modelized by other deeper-seated granite bodies. Based on numerical modelling it was possible to infer two distinct intrusion styles for the alkaline pluton. The calculated model values are consistent with an emplacement by sheeting for the northern body, as already suggested by satellyte imagery and field mapping. On the other hand, the results point to a transition towards a diapir-related style associated to the smaller. southern stock. This difference in intrusion styles may relate to intensity variations and transtensional sites of the shear deformation along the JSZ. Trace element and Sr and Nd isotopes of the alkaline granites are compatible with their derivation trom a more basic crustal source, as compared to the presently outcropping highgrade gneisses, with participation (or alternatively dominated by) of an enriched lithospheric mantle component. Like other igneous suites in the Seridó Belt, the high LlL contents and fractionated REE patterns of the basic rocks also point to an enriched mantle as the source for this kind of magmatism. Geochemical and isotope data are compatible with a lower crustal origin for the porphyritic granites. On the basis of the strong control of the JSZ on the emplacement of lower crustal (porphyritic and alkaline granites) or lithospheric mantle (basic rocks, alkaline granites or a component of them) magmas, one may infer a deep root for this structure, bearing an important role in magma extraction, transport and emplacement in the Japi region, eastern domain of the Seridó Belt

Análise de terrenos na porção setentrional da Província Borborema, NE do Brasil: integração de dados geológicos e gravimétricos

It is presently assumed that the Borborema Province resulted from a complex collisional process associated with the convergent movement of plates, possibly involving amalgamation and accretion of microplates. This process was consolidated at the end of the Brasiliano event. It is investigated the possible limits for the tectonostratigraphic terranes in the northern portion of the province based on an integrated study of geological and gravity data. The study area comprises the portion of the Borborema Province located north of the Patos Lineament, limited by longitudes 33º00 W and 43º29 44"W and latitudes 1º36 S and 8º00 S. A revision of the regional geology allowed to identify areas presenting contrasting geological attributes, possibly representing different terranes whose limits are always shear zones of Brasiliano-age. The Sobral-Pedro II shear zone is the only one undoubtedly presenting geological attributes of sutures zones. The other shear zones are very likely associated with a geodinymic context of accretion, involving oblique collisions (docking), transcurrent and/or transforming sutures, and deep intracrustal shear zones. The gravity data contributed as a tool to identify strong lateral contrasts of density inside the upper crust possibly associated with crustal blocks tectonically juxtaposed. The dominant long wavelength anomaly in the Bouguer anomaly map is an expressive gradient, grossly parallel to the continental margin, caused by density variation across the crust-mantle interface in the transition from the continental crust to the oceanic crust originated by the separation between South America and Africa. Medium to small wavelength anomalies are due to intracrustal heterogeneities such as different Precambrian crustal blocks, Brasiliano-age granites and Mesozoic sedimentary basins. A regional-residual separation of the Bouguer anomaly map was performed in order to enhance in the residual map the effect due to intracrustal heterogeneities. The methodology used for this separation was a robust polinomial fitting. The inversion of residual gravity field resulted in a density contrast map (Δρ), in an equivalent layer that provided more accurated anomalies contours and consolidated the model which the sources of residual anomalies are located in the upper part of the present crust. Based on the coincidence of gravity lineaments in the residual map and Brasiliano shear zones, and using additional geological information, the following shear zones are proposed as limits between terranes: Patos shear zone, Sobral-Pedro II shear zone, Picuí-João Câmara shear zone, Remígio-Pocinhos shear zone, Senador Pompeu shear zone, Tauá shear zone, and Portalegre shear zone. Based on the geological/geophysical information it is attributed a higher level of confidence to the first three proposed limits(Patos, Sobral Pedro II, and Picuí-João Câmara shear zones). From west to east, these shear zones individualize the following terranes: Northwest of Ceará terrane, Central Ceará terrane, Tauá terrane, Orós-Jaguaribe terrane, Seridó terrane, and São José de Campestre terrane. In our study, the Rio Piranhas and Patos terranes are questioned because their previously proposed limits do not present good geological and gravimetric evidences. On the other hand, the previously proposed Cearense terrane is now subdivided into Central Ceará and Tauá terranes. Two residual gravity profiles located in the Seridó belt were interpreted using 2 ½ D direct gravity modeling. The main result of the modeling process is that all anomalies, with the exception of one, can be explained by outcroppring bodies, therefore restricted to the upper part of the present crust