Metalog��nese do dep��sito de Cu Cerro dos Martins, RS.

Este trabalho revisa a geologia e apresenta dados in��ditos do Dep��sito de Cobre Cerro dos Martins (DCM), incluindo geocronologia Pb-Pb em zirc��o, inclus��es fluidas, is��topos est��veis (C, O e S), composi����o isot��pica do Sr e geoqu��mica de elementos maiores e tra��os das rochas vulc��nicas encaixantes. O dep��sito est�� hospedado na seq����ncia vulcano-sedimentar do Grupo Bom Jardim, da Bacia do Camaqu��, do Neoproteroz��ico do Escudo Sul Rio-grandense, e possui reservas calculadas de 1.450.000 t, com teor m��dio de 0,83% Cu. O dep��sito consiste de um conjunto de veios sulfetados que preenchem fraturas de dire����o N40��-60��W em rochas andes��ticas e sedimentares cl��sticas, com dissemina����es confinadas em n��veis de siltito, arenito, andesito e conglomerado, da Forma����o Hil��rio do Grupo Bom Jardim. Os minerais do min��rio filoneano s��o a calcosina e bornita com calcopirita, pirita, galena e esfalerita subordinadas. Digenita, covelita, malaquita cuprita e azurita ocorrem como min��rio secund��rio em ganga constitu��da de carbonatos, quartzo, minerais argilosos, barita e rara hematita. A composi����o qu��mica das vulc��nicas (elementos maiores e tra��os, incluindo ETR) indicam uma afinidade alcalina para o vulcanismo relacionado �� Forma����o Hil��rio na regi��o do Cerro dos Martins. Um corpo de quartzo-diorito, intrusivo nas rochas vulc��nicas e sedimentares, mostrou idade de 550 ��5 Ma (Pb-Pb em zirc��es) indicando um valor m��nimo para a gera����o do min��rio do DCM. Esta idade confirma a posi����o estratigr��fica desta rocha na Forma����o Acampamento Velho e tamb��m fornece uma idade m��nima para a deposi����o da seq����ncia vulcano-sedimentar encaixante do DCM. Os sulfetos do DCM mostram ��S34 CDT com valores relativamente homog��neos entre - 6.2 e + 0.9��� (n= 7). O valor de ��S34 CDT da calcopirita, levemente positivo (+0.9���), indica uma origem magm��tica para o S, mas os valores negativos encontrados nestes sulfetos, poderiam indicar o envolvimento de outras fontes com enxofre reduzido. Entretanto, a presen��a de hematita nas parag��neses minerais indica que o min��rio foi formado sob condi����es oxidantes, modificando a composi����o isot��pica original do enxofre magm��tico (��S34 CDT ~ 0���) para valores negativos. As baritas analisadas apresentam valores com ��S34 CDT entre +9.25 e +10.65��� (n=4) indicando deposi����o em condi����es oxidantes, originadas pela mistura de um fluido magm��tico-hidrotermal com ��gua mete��rica. A composi����o isot��pica do C das calcitas do DCM varia com ��C13 PDB entre - 1,90 a -4,45���, interpretada como resultante da mistura entre carbono de fonte magm��tica com m��rmores do embasamento. Inclus��es fluidas em quartzo do min��rio indicam temperaturas de deposi����o entre 157 e 273 ��C com mediana de 215 ��C (n = 45). A composi����o isot��pica do oxig��nio da ��gua em equilibrio com a calcita do fluido hidrotermal (T= 215 ��C) mostra valores de �� O18 SMOW entre 3 e 14, indicando H2O de origem magm��tica, com contribui����o de ��gua mete��rica. A raz��o Sr87/Sr86 das mesmas calcitas mostram valores entre 0,7068 ��� 0,7087, de crosta superior. Rochas plut��nicas e vulc��nicas do escudo com idades pr��ximas de 550 Ma possuem raz��es iniciais Sr87/Sr86 entre 0,704 ��� 0,710, compat��veis com aquelas encontradas nas calcitas da mineraliza����o. Os fluidos hidrotermais do magmatismo shoshon��tico-alcalino com idade de 595 Ma e Sr87/Sr86 entre 0,7041 a 0,7053, tamb��m s��o candidatos a fonte do Sr dos carbonatos hidrotermais, mas necessitariam de um componente mais radiog��nico. Assim, a fonte de C-O e Sr das calcitas do min��rio pode ter sido originada diretamente de um fluido magm��tico-hidrotermal ou de uma mistura entre este fluido e m��rmores do embasamento. Portanto, o dep��sito Cerro dos Martins �� interpretado como de origem magm��tica-hidrotermal, relacionado ao evento magm��tico alcalinoshoshon��tico, p��s-colisional da Orog��nese Dom Feliciano, com idade entre 595-550 Ma. Novos modelos explorat��rios para dep��sitos de cobre no Escudo do Rio Grande do Sul devem considerar o magmatismo alcalino na g��nese dos dep��sitos.

Direct determination of Cu, Cd, Ni and Pb in aquatic humic substances by graphite furnace atomic absorption spectrometry

Funda����o de Amparo �� Pesquisa do Estado de S��o Paulo (FAPESP)

Influ��ncia dos ��ons Mg, Ca, Fe, Cu e Zn sobre a tens��o superficial est��tica de solu����es contendo surfatante

O objetivo do estudo foi avaliar a influ��ncia da presen��a de cinco ��ons em uma calda de pulveriza����o contendo o surfatante Aterbane. A tens��o superficial foi analisada por meio da medi����o da massa de um conjunto de 25 gotas, com quatro repeti����es constituindo um tratamento. O trabalho foi dividido em duas etapas. Na primeira, os tratamentos foram combinados em esquema fatorial 9x5x2, sendo nove concentra����es do surfatante Aterbane (0,01; 0,025; 0,05; 0,1; 0,2; 0,5; 1; 2; e 3%), cinco ��ons (Mg++, Ca++, Fe+++, Cu+++ e Zn+++) e duas concentra����es desses elementos (10 e 100 ppm). Na segunda etapa, os tratamentos foram combinados em esquema fatorial 5x5x1, utilizandose os mesmos cinco elementos (Mg++, Ca++, Fe+++, Cu+++ e Zn+++), em cinco concentra����es (1, 5, 20, 50 e 200 ppm), com apenas uma concentra����o do surfatante Aterbane (0,025%). Outros nove tratamentos permitiram avaliar as tens��es superficiais das concentra����es do surfatante (0,01; 0,025; 0,05; 0,1; 0,2; 0,5; 1; 2; e 3%) sem a adi����o dos ��ons. Os resultados mostraram que houve interfer��ncia dos ��ons sobre as solu����es, j�� que, com exce����o do Fe+++ (na concentra����o de 10 e 100 ppm) e do Cu+++ (na concentra����o de 100 ppm), todos os ��ons reduziram a tens��o m��nima alcan��ada e aumentaram a efici��ncia do surfatante, implicando benef��cios �� a����o do surfatante e sobre as caracter��sticas de poss��veis solu����es de aplica����o. Todos os ��ons avaliados promoveram redu����es nas tens��es superficiais de solu����es do surfatante na concentra����o de 0,025%.

Saberes de astronomia no 1�� e 2�� ano do ensino fundamental numa perspectiva de letramento e inclus��o

This work suggests a discussion about methodologies and didactic-pedagogical activities for the teaching of Astronomy in first and second cycles of the primary school, in a perspective of literacy and inclusion. The presented proposals have been developed in a group of the Public School Alceu Amoroso Lima, North of Natal city, with children since six years old, amongst which two considered as being with special needs . This research aims to demonstrate that it is possible to develop with those children the contents of Astronomy, while they participate of the process of literacy and inclusion. From this, we are searching a theoretical-practical contribution so that the Par��metros Curriculares Nacionais (Brazilian Nacional Curricular Guideness) include the referred contents in first cycle of primary school. For the accomplishment of this research, Experiential Astronomy was initially proposed. Later on, many workshops had been carried through (clay, ripping , crepon paper, plasticine, cardboard and gastro-lunar ). All the proposed activities were based on the conjunction of contents, which characterized the interdisciplinarity. Through the approach we adopted and the practices we proposed, we could evidence that not only children considered as being normal , but also that ones who carries special needs could appropriate themselves of our writing code, develop and incorporate a daily relationship close to the stuffs of the sky, learn many information about all of this, besides constructing attitudinal, procedural and conceptual contents

Study of copper complexes adsorbed on a silica gel surface chemically modified with 2-amino-1,3,4-thiadiazole

The isotherms of adsorption of CuX2 (X=Cl-, Br-, ClO4-) by silica gel chemically modified with 2-amino-1,3,4-thiadiazole were studied in acetone and ethanol solutions: at 298 K. The following equilibria constants (in 1 mol(-1)) were determined: (a) CuCl2: 3.5 x 10(3) (ac), 2.0 x 10(3) (eth); (b) CuBr2: 2.8 x 10(3) (ac), 2.0 x 10(3) (eth); (c) Cu(ClO4)(2): 1.8 x 10(3) (ac), 1.0 x 10(3) (eth); ac = acetone, eth = ethanol. The electron spin resonance spectra of the surface complexes indicated a tetragonal distorted structure in the case of lower degrees of metal loading on the chemically modified surface. The d-d electronic transition spectra showed that for the ClO4-, complex, the peak of absorption did not change for any degree of metal loading, and for Cl- and Br- complexes, the peak maxima shifted to a higher energy region with a lower metal loading. (C) 1998 Elsevier B.V. B.V. All rights reserved.

Study of copper complexes absorbed on a silica gel surface chemically modified with 5-amino-1,3,4-thiadiazole-2-thiol

The isotherms of adsorption of CuX2 (XCl-, Br-, ClO4-) by silica gel chemically modified with 5-amino-1,3,4-thiadiazole-2-thiol were studied in acetone and ethanol solutions, at 25 degrees C. The following equilibria constants (in L mol(-1)) were determined: (a) CuCl2, 3.2 x 10(3) (ac), 2.5 x 10(3) (eth); (b) CuBr2, 2.9 x 10(3) (ac), 2.3 x 10(3) (eth); (c) Cu(ClO4)(2), 1.8 x 10(3) (ac), 1.2 x 10(3) (eth); ac, acetone; eth, ethanol. The electron spin resonance spectra of the surface complexes indicated a tetragonal-distorted structure in the case of lower degrees of metal loading on the chemically modified surface. The d-d electronic transition spectra showed that for the ClO4- complex, the peak of absorption did not change for any degree of metal loading and for Cl- and Br- complexes, the peak maxima shifted to higher energy with lower metal loadings. (C) 1998 Academic Press.

Adsorption of CuX2 (X = Cl-, Br-, and ClO4-) on a silica gel surface chemically modified with thiazolidine-2-thione from acetone and ethanol solutions

The isotherms of adsorption of CuX2 (X = Cl-, Br, ClO4-,) by silica gel chemically modified with thiazolidine-2-thione were studied in acetone (ac) and ethanol (eth) solutions at 25 degrees C. The following equilibrium constants (in 1 mol(-1)) were determined: a) CuCl2, 1.9 x 10(3) (ac), 1.6 x 10(3) (eth); b) CuBr2, 1.7 x 10(3) (ac), 1.2 x 10(3) (eth); c) Cu(ClO4)(2), 1.1 x 10(3) (ac), 1.0 x 10(3) (eth). The electron spin resonance spectra of the surface complexes indicate a tetragonal distorted structure in the case of lower degrees of metal loading on the chemically modified surface. The d-d electronic transition spectra show that for the ClO4- complex, the peak of absorption did not change for any degree of metal loading, and for Cl- and Br complexes, the peak maxima shift to higher energy with lower metal loading.

Preconcentration and determination of Cu(II) in a fresh water sample using modified silica gel as a solid-phase extraction adsorbent

Funda����o de Amparo �� Pesquisa do Estado de S��o Paulo (FAPESP)

Comparison of the univariate and multivariate methods in the optimization of experimental conditions for determining Cu, Pb, Ni and Cd in biodiesel by GFAAS

Funda����o de Amparo �� Pesquisa do Estado de S��o Paulo (FAPESP)

Attachment of 2,2-bipyridine onto a silica gel for application as a sequestering agent for copper, cadmium and lead ions from an aqueous medium

Funda����o de Amparo �� Pesquisa do Estado de S��o Paulo (FAPESP)

Efeitos da suplementa����o de fitase sobre a disponibilidade aparente de Mg, Ca, Zn, Cu, Mn e Fe em alimentos vegetais para a til��pia-do-nilo

Cem juvenis de til��pia-do-nilo (Oreochromis niloticus; PV = 100.0 �� 5.0 g) foram distribu��dos em 10 tanques-rede com o objetivo de avaliar o efeito da suplementa����o da enzima fitase (0, 1.000 e 2.000 UFA/kg) sobre a disponibilidade de minerais em alguns alimentos energ��ticos (milho, milho extrusado, farelo de trigo, farelo de arroz e farelo de sorgo) e prot��icos (farelo de soja extrusado, farelo de soja, farelo de girassol, farelo de algod��o e gl��ten de milho) utilizados na alimenta����o de til��pia-do-nilo (Oreochromis niloticus). Para determina����o dos coeficientes de disponibilidade aparente (CDA) do c��lcio (Ca), magn��sio (Mg), zinco (Zn), cobre (Cu), ferro (Fe) e mangan��s (Mn), foram confeccionadas 31 ra����es, marcadas com 0,10% de ��xido de cr��mio III uma refer��ncia (ra����o purificada) e 30 contendo os dez alimentos e os diferentes n��veis de suplementa����o da enzima fitase. O CDA dos nutrientes foi calculado com base no teor de cr��mio da ra����o e das fezes. A fitase aumenta, nos vegetais, a disponibilidade do Mg, Cu, Zn e Mn, os quais apresentam tend��ncia diferenciada, em raz��o do seu valor biol��gico e do n��vel de suplementa����o de enzima.

Role of the alpha(1)- and alpha(2)-adrenoceptors of the paraventricular nucleus on the water and salt intake, renal excretion, and arterial pressure induced by angiotensin II injection into the medial septal area

In this study we investigated the influence of cu-adrenergic antagonists injections into the paraventricular nucleus (PVN) of the hypothalamus on the thirst and salt appetite, diuresis, natriuresis, and presser effects of angiotensin II (ANG II) stimulation of medial septal area (MSA). ANG II injection into the MSA induced water and sodium intake, diuresis, natriuresis, and presser responses. The previous injection of prazosin (an alpha (1)-adrenergic antagonist) into the PVN abolished, whereas previous administration of yohimbine (an alpha (2)-adrenergic antagonist) into the PVN increased the water and sodium intake, urinary, natriuretic, and presser responses induced by ANG ii injected into the MSA. Previous injection of a nonselective alpha -adrenergic antagonist, regitin, into the PVN blocked the urinary excretion, and reduced the water and sodium intake, sodium intake, and presser responses induced by ANG II injected into the MSA. The present results suggest that alpha -adrenergic pathways involving the PVN are important for the water and sodium excretion, urine and sodium excretion, and presser responses, induced by angiotensinergic activation of the MSA. (C) 2001 Elsevier B.V.

Evaluation of Cu, Mn, and Se in Vegetables Using Ultrasonic Extraction and GFAAS Quantification

Funda����o de Amparo �� Pesquisa do Estado de S��o Paulo (FAPESP)

Determination of metal ions in natural waters by flame-AAS after preconcentration on a 5-amino-1,3,4-thiadiazole-2-thiol modified silica gel.

5-amino-1,3,4-thiadiazole-2-thiol groups attached on a silica gel surface have been used for adsorption of Cd(II), Co(II), Cu(II), Fe(III), Ni(II), Pb(II) and Zn(II) from aqueous solutions. The adsorption capacities for each metal ion were (in mmol.g(-1)): Cd(II)= 0.35, Co(II)= 0.10, Cu(II)= 0.15, Fe(III)= 0.20, Hg(Il)= 0.46, Ni(II)= 0.16, Pb(II)= 0.13 and Zn(II)= 0.15. The modified silica gel was applied in the preconcentration and quantification of trace level metal ions present in water samples (river, and bog water).

Aging kinetics in the Cu-8 wt.% Al alloy with Ag additions

The influence of additions of 2, 4, 6, 8, 10 and 12 wt.% Ag in the isothermal aging kinetics of the Cu-8 wt.% Al alloy was studied using microhardness measurements, differential scanning calorimetry, optical and scanning electron microscopy and X-ray diffractometry. The results indicate that the presence of silver is responsible for the shift of the equilibrium concentration to higher Al contents, allowing the formation of the gamma(1) phase (Al4Cu9) in this alloy. For Ag additions up to 6% the dominant kinetic process is Ag precipitation and for additions from 8 to 12% Ag the nucleation of the perlitic phase dominates. (C) 2003 Elsevier B.V. B.V. All rights reserved.