998 resultados para MINAS
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Inscripción en parte inferior: "E Tabula Romae in Capitolio asservata"
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Mode of access: Internet.
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"Com um appendice sobre a nova lorena diamantina, sua descripção, suas producções mineralógicas, e utilidades que d'este paiz possam resultar ao estado."
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Mode of access: Internet.
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At head of title 1902-1939: Ministerio de Fomento.
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Mode of access: Internet.
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Mode of access: Internet.
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Subtitle varies.
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Mode of access: Internet.
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Ar-40/Ar-39 laser incremental-heating analyses of 22 individual grains of supergene cryptomelane from three weathering profiles, up to 400 km apart, in the Rio Doce valley and Barbacena regions at Minas Gerais, Brazil, show that the formation of weathering profiles in these regions is contemporaneous, suggesting a strong weathering event in the Middle to Late Miocene (10-8 Ma). The preservation of these Miocene samples at or near the present surface suggests that either erosion rates have been very low in the region since the Miocene or that a much thicker weathering mantle was present in the region originally. Assuming a constant thickness of weathering profiles in the region throughout the Tertiary, we may calculate weathering front propagation rates of 4-8 m Myr(-1) during the past 10 Ma. Copyright (C) 2004 John Wiley Sons, Ltd.
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Weathering profiles overlying the Sapecado, Pico and Andaime iron ore deposits, Quadrilátero Ferrífero (QF), Minas Gerais, Brazil, reach depths of 150–400 m and host world-class supergene iron orebodies. In addition to hosting supergene ore bodies of global economic significance, weathered banded iron-formations at the Quadrilátero Ferrífero and elsewhere (e.g., Carajás, Hamersley) are postulated to underlie some of the most ancient continuously exposed weathering profiles on earth. Laser incremental-heating 40Ar/39Ar results for 69 grains of hollandite-group manganese oxides extracted from 23 samples collected at depths ranging from 5 to 150 m at the Sapecado, Pico and Andaime deposits reveal ages ranging from ca. 62 to 14 Ma. Older Mn-oxides occur near the surface, while younger Mn-oxides occur at depth. However, many samples collected at the weathering–bedrock interface yield ages in the 51–41 Ma range, suggesting that the weathering profiles in the Quadrilátero Ferrífero had already reached their present depth in the Paleogene. The antiquity of the weathering profiles in the Quadrilátero Ferrífero is comparable to the antiquity of dated weathering profiles on banded iron-formations in the Carajás Region (Brazil) and the Hamersley Province, Western Australia. The age versus depth distributions obtained in this study, but not available for other regions containing similar supergene iron deposits, suggest that little further advance of the weathering front has occurred in the Quadrilátero Ferrífero lateritic profiles during the Neogene. The results suggest that weathering in some of these ancient landscapes is not controlled by the steady-state advance of weathering fronts through time, but may reflect climatic and geomorphological conditions prevailing in a remote past. The geochronological results also confirm that the ancient landsurfaces in the Quadrilátero Ferrífero probably remained immune to erosion for tens of millions of years. Deep weathering, mostly in the Paleogene, combined with low erosion rates, account for the abundance and widespread distribution of supergene iron, manganese, and aluminum orebodies in this region.
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Ar-40/Ar-39 incremental heating ages for twenty one grains of cryptomelane, collected at 0, 42, 45, and 60 in depths in the Cachoeira Mine weathering profile, Minas Gerais, permit calculating long-term (10 Ma time scale) weathering rate (saprolitization rate) in SE Brazil. Pure well-crystallized cryptomelane grains with high K contents (3-5 wt.%) yield reliable geochronological results. The Ar-40/Ar-39 plateau ages obtained decrease from the top to the bottom of the profile (12.7 +/- 0.1 to 7.6 +/- 0.1 Ma at surface; 7.6 +/- 0.2 to 6.1 +/- 0.2 Ma at 42 m; and 7.1 +/- 0.2 to 5.9 +/- 0.1 Ma at 45 in; 6.6 +/- 0.1 to 5.2 +/- 0.1 Ma at 60 in), yielding a weathering front propagation rate of 8.9 +/- 1.1 m/m.y. From the geochronological results and the mineral transformations implicit by the current mineralogy in the weathering profiles, it is possible to calculate the saprolitization rate for the Cachoeira Mine lithologies and for adjacent weathering profiles developed on granodiorites and scbists. The measured weathering front propagation rate yields a saprolitization rate of 24.9 +/- 3.1 t/km(2)/yr. This average long-term (> 10 Ma) saprolitization rate is consistent with mass balance calculations results for present saprolitization rates in weathering watersheds. These results are also consistent with longterm saprolitization rates estimated by combining cosmogenic isotope denudation rates with mass balance calculations. (c) 2005 Elsevier B.V All rights reserved.
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Esse estudo investiga como a aprendizagem organizacional pode influenciar a inovação em produtos nas empresas de base tecnológica. As empresas estudadas estão localizadas no Arranjo Produtivo Local Eletroeletrônico, conhecido informalmente como Vale da Eletrônica, na cidade de Santa Rita do Sapucaí, Minas Gerais. O arcabouço teórico envolve a exploração dos temas principais: aprendizagem organizacional e inovação. A decisão em estudar algumas empresas localizadas nessa cidade se deu por este ambiente ser composto de uma estrutura voltada à produção de conhecimentos tecnológicos dotados de inovações. Como objetivos específicos, esta pesquisa busca identificar as formas, fontes e o processo de aprendizagem organizacional que influenciaram as inovações apresentadas pelas empresas. Trata-se de uma pesquisa qualitativa, de caráter exploratório e descritivo. Os dados empíricos foram coletados por meio de entrevistas semiestruturadas a proprietários e gestores das empresas. O resultado evidenciou que formas e fontes internas e externas de aprendizagem e a proximidade da academia como coadjuvante no desenvolvimento das inovações contribuíram e influenciaram a inovação de produtos responsáveis pelo aumento de vantagem competitiva nas empresas. Esse estudo também permitiu apontar a relevância e a contribuição da aprendizagem organizacional na inovação de produtos e abre caminhos para estudos em outras empresas de base tecnológica.