Finite element modelling of rock alteration and metamorphic process in hydrothermal systems

We use the finite element method to simulate the rock alteration and metamorphic process in hydrothermal systems. In particular, we consider the fluid-rock interaction problems in pore-fluid saturated porous rocks. Since the fluid rock interaction takes place at the contact interface between the pore-fluid and solid minerals, it is governed by the chemical reaction which usually takes place very slowly at this contact interface, from the geochemical point of view. Due to the relative slowness of the rate of the chemical reaction to the velocity of the pore-fluid flow in the hydrothermal system to be considered, there exists a retardation zone, in which the conventional static theory in geochemistry does not hold true. Since this issue is often overlooked by some purely numerical modellers, it is emphasized in this paper. The related results from a typical rock alteration and metamorphic problem in a hydrothermal system have shown not only the detailed rock alteration and metamorphic process, but also the size of the retardation zone in the hydrothermal system. Copyright (C) 2001 John Wiley & Sons, Ltd.

Rare earth and trace elements in igneous and metamorphic minerals of oceanic gabbros from the Mid-Atlantic Ridge

SIMS analyses have been carried out on clinopyroxenes, plagioclases and amphiboles of six gabbroic samples from Holes 921-924 of the Ocean Drilling Program Leg 153 sited in the MARK area of the Mid-Atlantic Ridge at the ridge-transform intersection, to investigate the rare earth, trace and volatile element distribution in the lower ocean crust during igneous crystallization and higher grade metamorphic conditions. The metagabbros underwent granulite to subgreenschist facies conditions through three main tectono-metamorphic phases: (1) ductile regime (750 < T < 1000 °C and P = 0.3 GPa); (2) transitional regime (600 < T < 700 °C and P = 0.2 GPa); (3) brittle regime (350 < T < 600 °C and P < 0.2 GPa). Igneous clinopyroxenes show Cl-chondrite normalized patterns depleted in LREE, and nearly flat for HREE. The rare earth and trace element distributions in igneous clinopyroxenes and plagioclases indicate that these minerals act as REE reservoirs, and comprise the main contribution to the overall rock content. The abundances in igneous minerals reflect the degree of fractionation of the parent liquids. In metamorphic clinopyroxenes recrystallized in anhydrous assemblages, the REE and trace elements patterns mimic those of the primary ones. Conversely, clinopyroxerie re-equilibrated in amphibolebearing assemblages shows a significant increase in REE, Ti, Zr, Y and V, a negative Eu anomaly, and slight decreases in Sr and Ba. An overall increase of REE and some trace elements is evident in hydrous assemblages, with preferential partitioning in the amphibole. It shows high Ti (18196-22844 ppm), LREE depleted patterns and LaN/SmN = 0.10-0.33, LaN/YbN = 0.10-0.30. Amphiboles from granoblastic assemblages show homogeneous patterns with no or a positive anomaly for TiN and negative anomalies for SrN and ZrN. Volatiles in amphibole are low, with Cl/F < 1; H2O% is significantly lower than the stoichiometric ratio (1.33-1.53%). The composition of the clinopyroxene and amphibole recrystallized in low-strain domains records evidence of incomplete re-equilibration, and element diffusion and partitioning is in part controlled by the textural site. The possible origins of the fluids involved in the metamorphic recrystallization are discussed: (1) remobilization from igneous amphibole; (2) exsolution from evolved melts; (3) introduction of seawater-derived fluids modified in rock-dominated systems; (4) injection of highly evolved hydrous melts during the metamorphic process.

Agreste Central de Pernambuco: uma visão sobre a viabilidade da sua metropolização

Este trabalho tem por finalidade apresentar uma visão sobre a viabilidade da metropolização do Agreste Central de Pernambuco. Para tanto, trata-se aqui de apresentar uma análise inicial sobre o atual estágio da globalização os seus efeitos e formas de sobrevivência dos pequenos centros produtivos neste constante e metamórfico processo. Trata ainda dos processos de regionalização, passando-se pela sua conceituação até as formas mais recentes desse fenômeno, alcançando-se a metropolização como alternativa de centros urbanos para atingir um novo patamar social, político, econômico e cosmopolita, que melhor se adéqua à sua realidade. É apresentada neste trabalho, a situação atual do Agreste Central de Pernambuco, sob diversos aspectos, especialmente quanto à economia local, que é a mola propulsora da região, e o principal argumento daqueles que defendem a sua metropolização. Para tanto, fazse necessário analisar, também, o recente processo de interiorização do desenvolvimento por que passa o Brasil, e, em especial, o Estado de Pernambuco. É feita, ainda, uma avaliação histórica, sócio-econômica e política das principais cidades desta região, que são Santa Cruz do Capibaribe, Toritama e Caruaru, com foco nesta última, que, por vocação, seria a cidade sede da pretensa Região Metropolitana do Agreste Central de Pernambuco. Em seguida, é feita uma análise de interação das cidades envolvidas, e os dados são comparados com as três principais regiões metropolitanas do interior do País. É traçado um paralelo entre o atual pólo de desenvolvimento e os prováveis benefícios da pretensa região metropolitana, c, por fim, analisada a percepção dos Agentes Políticos, sobre o tema, para se apresentar a visão deste trabalho sobre a viabilidade da metropolização da região estudada, c as propostas altcmativas.

Palavras em desdobramento na poesia de Herberto Helder

No poema Em silêncio descobri essa cidade no mapa, inserido em A máquina lírica (1964), Herberto Helder desenha um contra mapa desnorteante com as palavras, que pulalam na travessia da escrita, deslocando-se incessantemente e ocupando diferentes posições nos versos. A proliferação dos vocábulos que se cruzam em novas combinações dão origem aos fios cambiantes que se dobram, redobram e desdobram-se no tecido da linguagem que objetivamos desfiar neste trabalho.

Rhythms of anorexigenic neuropeptides in senegalese sole: Effects of light, feeding regimes and developmental stage.

Increasing knowledge on the endocrine mechanisms that regulate feeding and growth in cultured fish can contribute to make improvement in fish holding conditions and feeding strategies, supporting the development of new techniques that could ameliorate feeding, food conversion efficiency and growth in aquaculture practice. The main objective of this study was to investigate how daily mRNA expression of three specific anorexigenic hormones, i.e. the corticotropin-releasing hormone (CRH) and the paralogues α- and β- proopiomelanocortin (POMC), is modulated by different photoperiods, light spectra and feeding regimes, in both adult and larvae of Solea senegalensis. In addition, as Senegalese sole exhibits a shift from diurnal to nocturnal in locomotor activity and feeding habits during metamorphic process, we tried to elucidate if this shift is accompanied by relevant daily variations in the expression of these anorexigenic hormones before, during and after the completion of metamorphosis. In order to reach this main objective, three main experiments were developed. In a first experiment, adults were reared under LD (12 h light: 12h dark) cycle and fed at mid-light (ML), mid-dark (MD) and at random (RND). In a second experiment, adult specimens were reared in constant darkness (DD) and fed at subjective mid-light (sML) or at RND. Larvae of Senegalese sole were reared under LD cycle with white, blue or red light for 40 days. Our results show an independence of crh mRNA expression from the feeding time and suggest an endogenous control of crh expression in sole. Both pomc paralogues showed significant daily rhythms under LD conditions. The rhythms were maintained or were even more robust under DD conditions for pomc_a, but were completely abolished for pomc_b. Our results indicate an endogenous control of pomc_a expression by the molecular clock in telencephalon and diencephalon, but not in the pituitary gland. Our findings confirm for the first time the significant influence that ambient lighting has on larval growth and development in Senegalese sole, revealing an important effect of light spectra upon functional elements of this species. Our results also emphasize the importance of maintaining cycling light-dark conditions of the adequate wavelengths in aquaculture practices during early development of sole.

40Ar/39Ar dating of Mn-iron ore of the Sapecado Mine, Qadrilatero Ferrifero, Brazil

The SW region of Amazonian craton presents policyclic evolution between 1.80-1.00 Ga and is comprised of the Rio Negro-Juruena, Rondoniana and Sunsas Provinces. The evolution of this region has being characterized by four orogens: Alto Jauru (1.79-1.74 Ga), Cachoeirinha (1.58-1.52 Ga), Suíte Santa Helena (1.45-1.42 Ga) e Sunsas/Aguapeí (1.0-0.9 Ga). The Alto Jauru orogen consists of TTG gneissic associations, greenstone sequences and intrusive granitoids origined in volcanic arc setting. Eight 40Ar/39Ar step-heating analyses were carried out in minerals (biotiteand hornblende) to investigate the thermal history and crustal evolution of this region. From the Alto Jauru orogen was sampled the gneiss banded and two biotite grains provide large dispersion of apparent ages, suggesting heterogenity in reservoir of the argon. Apparent age diagram yielded integrated ages of 1472 ± 6 Ma, interpreted as minimum ages of regional cooling episode. Three analyses of hornblende present ages varing from 1310 to 1400 Ma, possibly because smaller grain size become more susceptible to argon loss. 40Ar/39Ar step-heating methodology applied on biotite of pyroclastic tuff (U-Pb age about 1758 ± 7 Ma) presented integrated age of 1507 ± 7 Ma. The results found for this terrane demonstrated a geochronological correlation with metamorphic process linked Cachoeirinha orogen. Biotite and hornblende grains separates from granite and a tonalite origined during Cachoeirinha orogen were analyzed and the apparent age diagrams indicated well-defined plateau ages of 1520-1540 Ma. Biotite grains from a granitic sample were analized, and integrated ages about 1526 ± 2 Ma were obtained due argon loss in the initial steps. Thermochronologic history of SW region Amazonian craton is coherent with regional policyclic events and 40Ar/39Ar ages here presented probably correspond to regional cooling period of Cachoeirinha orogen.

Unraveling an antique subduction process from metamorphic basement around Medellin city, Central Cordillera of Colombian Andes

In the surroundings of Caldas and El Retiro cities (Colombia) metamorphic rocks derived from basic and pelitic protoliths comprise the Caldas amphibole schist and the Ancon schist respectively. Subordinated metamorphosed granite bodies (La Miel gneiss) are associated to these units, and The El Retiro amphibolites, migmatites and granulites crops out eastwards of these units, separated by shear zones. The Caldas amphibole schist and the Ancon schist protoliths could have been formed in a distal marine reduced environment and amalgamated to the South American continent in an apparent Triassic subduction event. The El Retiro rocks are akin to a continental basement and possible include impure metasediments of continental margin, whose metamorphism originated granulite facies rocks and migmatites as a result of the anatexis of quartz-feldspathic rocks. The metamorphism was accompanied by intense deformation, which has juxtaposed both migmatites and granulite blocks. Afterward, heat and fluid circulation associated with the emplacement of minor igneous intrusions resulted in intense fluid-rock interaction, variations in the grain size of the minerals and, especially, intense retrograde metamorphic re-equilibrium. Thermobarometric estimations for the Caldas amphibole schist indicate metamorphism in the Barrovian amphibolite fades. The metamorphic path is counter-clockwise, but retrograde evolution could not be precisely defined. The pressures of the metamorphism in these rocks range from 6.3 to 13.5 kbar, with narrow temperature ranging from 550 to 630 degrees C. For the Ancon schist metapelites the P-T path is also counter-clockwise, with a temperature increase evidenced by the occurrence of sillimanite and the cooling by later kyanite. The progressive metamorphism event occurred at pressures of 7.6-7.2 kbar and temperatures of 645-635 degrees C for one sample and temperature between 500 and 600 degrees C under constant pressure of 6 kbar. The temperature estimated for these rocks varies between 400 and 555 degrees C at pressures of 5-6 kbar in the retrograde metamorphic path. The El Retiro rocks evidence strong decompression with narrow variation in temperature, showing pressure values between 8.7 and 2.7 kbar at temperatures of 740-633 degrees C. These metamorphic fragments of the basement in the Central Cordillera of the Colombian Andes could represent a close relationship with an antique subduction zone. (C) 2011 Elsevier Ltd. All rights reserved.

Volatile transport during the crystallization of anatectic melts: Oxygen, boron and hydrogen stable isotope study on the metamorphic complex of Naxos, Greece

Crystallization of anatectic melts in high-temperature metamorphic terrains releases volatile-rich magmas that can be transported into adjacent lithologies. This study addresses the variations in the oxygen, boron and hydrogen isotopic composition of aplite-pegmatite dikes that formed during the crystallization of anatectic melts in regional high-temperature metamorphism on the island of Naxos, Greece, and propagated upward into the overlying sequences of metamorphic schist. The transport distance of these dikes was increased through a significant horizontal component of travel that was imposed by contemporaneous low-angle extensional shearing. Laser fluorination oxygen isotope analyses of quartz, tourmaline, garnet, and biotite mineral separates from the aplite-pegmatite dikes show a progressive rise in delta(18)O values with increasing distance from the core. Oxygen isotope fractionations among quartz, tourmaline, and garnet show temperature variations from > 700degreesC down to similar to400degreesC. This range is considered to reflect isotopic fractionation beginning with crystallization at high temperatures in water-undersaturated conditions and then evolving through lower temperature crystallization and retrograde sub-solidus exchange. Two processes are examined for the cause of the progressive increase in delta(18)O values: (1) heterogeneous delta(18)O sources and (2) fluid-rock exchange between the aplite/pegmatite magmas and their host rock. Although the former process cannot be ruled out, there is as yet no evidence in the exposed sequences on Naxos for the presence of a suitable high delta(18)O magma source. In contrast, a tendency for the delta(18)O of quartz in the aplite/pegmatite dikes to approach that of the quartz in the metamorphic rock suggests that fluid-rock exchange with the host rock may potentially be an important process. Advection of fluid into the magma is examined based on Darcian fluid flow into an initially water-undersaturated buoyantly propagating aplitic dike magma. It is shown that such advective flow could only account for part of the O-18-enrichment, unless it were amplified by repeated injection of magma pulses, fluid recycling, and deformation-assisted post-crystallization exchange. The mechanism is, however, adequate to account for hydrogen isotope equilibration between dike and host rock. In contrast, variations in the delta(11)B values of tourmalines suggest that B-11/B-10 fractionation during crystallization and/or magma degassing was the major control of boron geochemistry rather than fluid-rock interaction and that the boron isotopic system was decoupled from that of oxygen. Copyright (C) 2003 Elsevier Ltd.

Trace element partitioning in HP-LT metamorphic assemblages during subduction-related metamorphism, Ile de Groix, France: a detailed LA-ICPMS study

Devolatilization reactions and subsequent transfer of fluid from subducted oceanic crust into the overlying mantle wedge are important processes, which are responsible for the specific geochemical characteristics of subduction-related metamorphic rocks, as well as those of arc magmatism. To better understand the geochemical fingerprint induced by fluid mobilization during dehydration and rehydration processes related to subduction zone metamorphism, the trace element and rare earth element (REE) distribution patterns in HP-LT metamorphic assemblages in eclogite-, blueschist- and greenschist-facies rocks of the Ile de Groix were obtained by laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) analysis. This study focuses on 10 massive basic rocks representing former hydrothermally altered mid-ocean ridge basalts (MORB), four banded basic rocks of volcano-sedimentary origin and one micaschist. The main hosts for incompatible trace elements are epidote (REE, Th, U, Pb, Sr), garnet [Y, heavy REE (HREE)], phengite (Cs, Rb, Ba, B), titanite [Ti, Nb, Ta, REE; HREE > LREE (light REE)], rutile (Ti, Nb, Ta) and apatite (REE, Sr). The trace element contents of omphacite, amphibole, albite and chlorite are low. The incompatible trace element contents of minerals are controlled by the stable metamorphic mineral assemblage and directly related to the appearance, disappearance and reappearance of minerals, especially epidote, garnet, titanite, rutile and phengite, during subduction zone metamorphism. Epidote is a key mineral in the trace element exchange process because of its large stability field, ranging from lower greenschist- to blueschist- and eclogite-facies conditions. Different generations of epidote are generally observed and related to the coexisting phases at different stages of the metamorphic cycle (e.g. lawsonite, garnet, titanite). Epidote thus controls most of the REE budget during the changing P-T conditions along the prograde and retrograde path. Phengite also plays an important role in determining the large ion lithophile element (LILE) budget, as it is stable to high P-T conditions. The breakdown of phengite causes the release of LILE during retrogression. A comparison of trace element abundances in whole-rocks and minerals shows that the HP-LT metamorphic rocks largely retain the geochemical characteristics of their basic, volcano-sedimentary and pelitic protoliths, including a hydrothermal alteration overprint before the subduction process. A large part of the incompatible trace elements remained trapped in the rocks and was recycled within the various metamorphic assemblages stable under changing metamorphic conditions during the subduction process, indicating that devolatilization reactions in massive basic rocks do not necessarily imply significant simultaneous trace element and REE release.

[meanings Of The Sickening Process For Patients With Systemic Lupus Erythematosus: A Review Of The Literature.]

Systemic lupus erythematosus is an autoimmune disease that causes many psychological repercussions that have been studied through qualitative research. These are considered relevant, since they reveal the amplitude experienced by patients. Given this importance, this study aims to map the qualitative production in this theme, derived from studies of experiences of adult patients of both genders and that had used as a tool a semi-structured interview and/or field observations, and had made use of a sampling by a saturation criterion to determine the number of participants in each study. The survey was conducted in Pubmed, Lilacs, Psycinfo e Cochrane databases, searching productions in English and Portuguese idioms published between January 2005 and June 2012. The 19 revised papers that have dealt with patients in the acute phase of the disease showed themes that were categorized into eight topics that contemplated the experienced process at various stages, from the onset of the disease, extending through the knowledge of the diagnosis and the understanding of the manifestations of the disease, drug treatment and general care, evolution and prognosis. The collected papers also point to the difficulty of understanding, of the patients, on what consists the remission phase, revealing also that this is a clinical stage underexplored by psychological studies.

[in Process Citation].

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O aluno com deficiência visual nas aulas de educação física : análise do processo inclusivo = The student with visual impairments : analysis of inclusive process

Universidade Estadual de Campinas . Faculdade de Educação Física

Hegemonia e contra-hegemonia na construção de políticas de esporte e lazer : a experiência do Consórcio Brasília = Hegemony and counter-hegemony in the process of sport and leisure policy-making : the experience of the Consortium Brasilia

Universidade Estadual de Campinas . Faculdade de Educação Física

Effects of the condylar process fracture on facial symmetry in rats submitted to protein undernutrition

PURPOSE: To investigate the facial symmetry of rats submitted to experimental mandibular condyle fracture and with protein undernutrition (8% of protein) by means of cephalometric measurements. METHODS: Forty-five adult Wistar rats were distributed in three groups: fracture group, submitted to condylar fracture with no changes in diet; undernourished fracture group, submitted to hypoproteic diet and condylar fracture; undernourished group, kept until the end of experiment, without condylar fracture. Displaced fractures of the right condyle were induced under general anesthesia. The specimens were submitted to axial radiographic incidence, and cephalometric mensurations were made using a computer system. The values obtained were subjected to statistical analyses among the groups and between the sides in each group. RESULTS: There was significative decrease of the values of serum proteins and albumin in the undernourished fracture group. There was deviation of the median line of the mandible relative to the median line of the maxilla, significative to undernutrition fracture group, as well as asymmetry of the maxilla and mandible, in special in the final period of experiment. CONCLUSION: The mandibular condyle fracture in rats with proteic undernutrition induced an asymmetry of the mandible, also leading to consequences in the maxilla.

Influence of specimens' design and manufacturing process on microtensile bond strength to enamel: laboratory and FEA comparison

This study evaluated the effect of specimens' design and manufacturing process on microtensile bond strength, internal stress distributions (Finite Element Analysis - FEA) and specimens' integrity by means of Scanning Electron Microscopy (SEM) and Laser Scanning Confocal Microscopy (LCM). Excite was applied to flat enamel surface and a resin composite build-ups were made incrementally with 1-mm increments of Tetric Ceram. Teeth were cut using a diamond disc or a diamond wire, obtaining 0.8 mm² stick-shaped specimens, or were shaped with a Micro Specimen Former, obtaining dumbbell-shaped specimens (n = 10). Samples were randomly selected for SEM and LCM analysis. Remaining samples underwent microtensile test, and results were analyzed with ANOVA and Tukey test. FEA dumbbell-shaped model resulted in a more homogeneous stress distribution. Nonetheless, they failed under lower bond strengths (21.83 ± 5.44 MPa)c than stick-shaped specimens (sectioned with wire: 42.93 ± 4.77 MPaª; sectioned with disc: 36.62 ± 3.63 MPa b), due to geometric irregularities related to manufacturing process, as noted in microscopic analyzes. It could be concluded that stick-shaped, nontrimmed specimens, sectioned with diamond wire, are preferred for enamel specimens as they can be prepared in a less destructive, easier, and more precise way.