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Ultramafic complexes and associated mineral deposits in the Precambrian of eastern Minas Gerais, Brazil

Angeli, N.; Choudhuri, A.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 309-313
ENG
Relevância na Pesquisa
66.44%
Based on field work, prospection and petrographic studies ultramafic complexes and their mineral deposits from eastern Minas Gerais in southeastern Brazil are generally outlined to form a basis for future investigations in this region. The bodies dealt with occur at Ipanema, Córrego Novo, Bela Vista de Minas, Rio Pomba and Liberdade. These ultramafic bodies are generally enclosed in high-grade gneisses and consist of serpentinized peridotites and harzburgites which were metamorphosed together with their country rocks in upper amphibolite to granulite facies. Weathering of these rocks gives rise to nickeliferous laterite, while metamorphism has resulted in anthophyllite asbestos and talc deposits. © 1985 Springer-Verlag.

Aspectos economicos da exploração mineral

Isao Shintaku
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 01/06/1998 PT
Relevância na Pesquisa
46.31%
Este trabalho aborda os principais fatos econômicos que envolvem a exploração mineral, indo desde os aspectos geológicos, seleção de áreas, passando pelo o investimento inicial, suas dificuldades e deficiências, suas características, bem como o comportamento dos investimentos na exploração mineral no Brasil e em outros países. O Brasil, um dos maiores potenciais mineiros do mundo, tanto pela sua extensão territorial como por sua diversidade geológica, sofre uma perda significativa nos investimentos em pesquisa mineral, pois não oferece um clima adequado aos moldes internacionais, para entrada de capitais, comprometendo, o processo de geração de jazidas e, conseqüentemente, a descoberta de novas minas e o seu aproveitamento. Um levantamento comparativo dos investimentos em exploração mineral em diversos paises contemplando período o 1986-1995 indica que o Brasil ainda não ocupa uma posição de destaque no cenário mundial. Foram identificados nesta dissertação os riscos da exploração mineral, os tipos, e como podem ser administrados. Além disso, foi feita uma análise dos fatores que influenciam a tomada de decisão de um investimento mineral e, sob a forma de estudo de caso, foram abordados os aspectos econômicos do ouro; This work deals with the main economic facts in which are included the mineral exploration...

Exergy cost of mineral resources

Rosa, Rui Namorado; Rosa, Diogo R. N.
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Artigo de Revista Científica
Publicado em //2008 ENG
Relevância na Pesquisa
46.51%
Mineral deposits are considered as natural capital whose value can be assessed in exergy terms. Historical industry experience provides evidence that exploitation of mineral deposits and the beneficiation of ores are essentially energy intensive. The persisting decline of the grade of the developed deposits demands increasing exergy replacement and processing costs. The results demonstrate how far processed ores and concentrates are from ideal behaviour, and technologies from reversibility conditions. The exploitation of mineral resources of declining quality for mineral commodities imply a long time trend of increasing mass and exergy inputs spent per unit product output, in line with a law of ‘diminishing returns’ on invested exergy.

Lava Cave Microbial Communities Within Mats and Secondary Mineral Deposits: Implications for Life Detection on Other Planets

Northup, D.E.; Melim, L.A.; Spilde, M.N.; Hathaway, J.J.M.; Garcia, M.G.; Moya, M.; Stone, F.D.; Boston, P.J.; Dapkevicius, M.L.N.E.; Riquelme, C.
Fonte: Mary Ann Liebert, Inc. Publicador: Mary Ann Liebert, Inc.
Tipo: Artigo de Revista Científica
Publicado em /09/2011 EN
Relevância na Pesquisa
46.61%
Lava caves contain a wealth of yellow, white, pink, tan, and gold-colored microbial mats; but in addition to these clearly biological mats, there are many secondary mineral deposits that are nonbiological in appearance. Secondary mineral deposits examined include an amorphous copper-silicate deposit (Hawai‘i) that is blue-green in color and contains reticulated and fuzzy filament morphologies. In the Azores, lava tubes contain iron-oxide formations, a soft ooze-like coating, and pink hexagons on basaltic glass, while gold-colored deposits are found in lava caves in New Mexico and Hawai‘i. A combination of scanning electron microscopy (SEM) and molecular techniques was used to analyze these communities. Molecular analyses of the microbial mats and secondary mineral deposits revealed a community that contains 14 phyla of bacteria across three locations: the Azores, New Mexico, and Hawai‘i. Similarities exist between bacterial phyla found in microbial mats and secondary minerals, but marked differences also occur, such as the lack of Actinobacteria in two-thirds of the secondary mineral deposits. The discovery that such deposits contain abundant life can help guide our detection of life on extraterrestrial bodies. Key Words: Biosignatures—Astrobiology—Bacteria—Caves—Life detection—Microbial mats. Astrobiology 11...

The role of microbes in the formation of modern and ancient phosphatic mineral deposits

Crosby, Chris H.; Bailey, Jake V.
Fonte: Frontiers Research Foundation Publicador: Frontiers Research Foundation
Tipo: Artigo de Revista Científica
Publicado em 05/07/2012 EN
Relevância na Pesquisa
46.38%
The formation of marine phosphatic mineral deposits remains incompletely understood, despite decades of research. The involvement of bacteria in this process has long been suspected, and both modern and ancient associations between bacteria and phosphorites have been recorded. Only recently has a specific bacterial metabolic process associated with the formation of phosphorites been discovered. Recent studies demonstrate that polyphosphate utilization by sulfide-oxidizing bacteria results in the rapid precipitation of apatite – providing at least a partial mechanism to explain the close spatial correlation between accumulations of sulfide-oxidizing bacteria and modern phosphorites. Possible fossilized bacteria are known from ancient phosphatic mineral deposits. Potentially, the fossilized cells represent the remains of bacteria that induced the formation of those phosphorites. However, robust criteria for the recognition of these bacteria have yet to be identified.

High Resolution Electron Microscopy of Mineral Deposits at the Human Fissure Floor

Hayashi, Yoshihiko
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica Formato: text/html
EN
Relevância na Pesquisa
46.29%
The mineral deposits at the fissure floor was investigated using a high resolution electroa microscope. Three different shapes of crystals were observed at the floor: the fine pavement-like, plate-like and large crystals. A direct contact between two different shapes of crystals was recognized in high resolution images. Selected area electron diffractions indicated that the fine crystals consisted of hydroxyapatite (OH-AP), the plate-like crystals were a mixture of OH-AP and whitlockite, and the large crystals were mainly whitlockite. These findings indicate that a natural occlusion at the fissure floor might occur through mineral deposition although contact boundaries of crystals had an intricate configuration.

Aplicativo para a avalia??o econ?mica de jazidas minerais

Baudson, Adolfo Jos? Gon?alves Stavaux
Fonte: Programa de P?s-Gradua??o em Engenharia Mineral. Departamento de Engenharia de Minas, Escola de Minas, Universidade Federal de Ouro Preto. Publicador: Programa de P?s-Gradua??o em Engenharia Mineral. Departamento de Engenharia de Minas, Escola de Minas, Universidade Federal de Ouro Preto.
Tipo: Dissertação
PT_BR
Relevância na Pesquisa
46.41%
A avalia??o econ?mica de projetos de minera??o, em especial, de jazidas minerais, tem por finalidade prover crit?rios econ?micos para a tomada de decis?es, baseados na an?lise ampla dos seguintes aspectos: t?cnico, econ?mico, financeiro, de risco e intang?veis (fatores pol?ticos, meio ambiente, etc.). O processo de avalia??o consiste em comparar as alternativas econ?micas, para selecionar aquela mais rent?vel entre as apresentadas. Neste trabalho, buscou-se o desenvolvimento de um aplicativo, em ambiente de programa??o DELPHI, para a realiza??o da avalia??o econ?micofinanceira de jazidas minerais. Atrav?s da elabora??o do fluxo de caixa do projeto mineral, s?o aplicados os principais m?todos de avalia??o econ?mica, al?m de se realizar uma An?lise de Sensibilidade para esta avalia??o. Com este aplicativo, ser? poss?vel realizar estudos de avalia??o econ?mica n?o s? pelas empresas de minera??o, mas tamb?m pelas institui??es que os desenvolvem de forma acad?mica. ____________________________________________________________________________________________________; ABSTRACT: The valuation of mining projects, especially of mineral deposits, aims at providing economical criteria for decision making, based on a deep analysis of the following aspects: technical...

West Africa - Mineral Sector Strategic Assessment (WAMSSA) : An Environmental and Social Strategic Assessment for the Development of the Mineral Sector in the Mano River Union

World Bank
Fonte: World Bank Publicador: World Bank
Relevância na Pesquisa
46.48%
The West African Mineral Sector Strategic Assessment (WAMSSA) is a strategic environmental and social assessment intended to identify policy, institutional, and regulatory adjustments required to integrate environmental and social considerations into mineral sector development in Africa. The study focused on three Mano River Union (MRU) countries, Guinea, Liberia, and Sierra Leone, all categorized as mineral-rich countries which earn - or could earn (in the case of Liberia) - significant revenues from exports of bauxite, iron ore, rutile, gold, and diamonds. WAMSSA featured an analytical component, and an extensive consultation process designed to initiate a policy dialogue on improving mineral sector governance and enhancing the benefits of mineral sector development for the MRU region. This report summarizes the findings of the WAMSSA process, and provides a series of recommendations to address environmental, social, and governance priorities highlighted by analytical and consultation components of the assessment. The recommendations are intended to provide guidance to the African Mineral Governance Program (AMGP) and Extractive Industry Transparency Initiative Plus Plus initiatives that are gathering momentum in the region.

Yemen - Mineral Sector Review

World Bank
Fonte: World Bank Publicador: World Bank
Relevância na Pesquisa
46.49%
Dependence on the oil sector as a source of economic growth is no longer sustainable given the rate at which oil reserves are being depleted. Yemen will come to rely on other sectors of the economy, some of which have potential but remain under-developed. The mineral sector is one of these. The third five year plan for development and poverty alleviation 2006-2010, identified the mineral sector as one of the key sources of future growth for the country, along with tourism and agriculture. This study was conducted to assess the potential contribution of the mineral sector to sustainable growth and poverty alleviation in Yemen and to define the constraints that will need to be overcome if this potential is to be realized. In so doing it helps to define those areas of government action and donor support that will need to be sustained over the medium to long term.

Sierra Leone : Tapping the Mineral Wealth for Human Progress, A Break with the Past

World Bank
Fonte: Washington, DC Publicador: Washington, DC
EN_US
Relevância na Pesquisa
46.33%
Political instability and lack of an enabling and internationally competitive environment conducive to attracting investments particularly affected the mining sector. Excessive government control and attempts to raise higher foreign exchange and fiscal revenues from artisanal diamond activities were detrimental to artisanal mining development. The study provides an assessment and analysis of the economic and social importance of the mining sector in Sierra Leone and its impact on economic outcomes. It makes recommendations and identifies an action plan for mining sector revival and development. The Government presented this report to the stakeholders, including its international development partners, at a workshop in May 2003. The outcome of the discussions and recommendations is reflected in the report. The resulting report was subsequently discussed in a second national workshop during January 2004. Since January 2003, the Ministry of Mineral Resources has focused on a number of fronts including: formation of a core mineral policy; deepening the policy work through a review of the mineral and regulatory framework; efforts to improve the development of basic mapping geo-information; completion of the initial work required for improved administration and management of mineral rights through a cadastre system; improvements in productivity...

Phyto-exploration in arid subtropical, arid mediterranean and tropical savanna environments: biogeochemical mechanisms and implications for mineral exploration.

Reid, Nathan
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2009
Relevância na Pesquisa
46.51%
Vegetation sampling is an effective exploration technique in areas of transported cover where other techniques have been of limited success. Several plant species were sampled along transects across 9 known Au ore bodies; Triodia pungens was found give a Au, As, ±Zn, ±S, ±Ce and ±La signature which represented mineralisation through cover materials and Eucalyptus brevifolia was found to give a geobotanical and ±Ca, ±Mg, P, S and Zn signature of underlying geological structure. The Hyperion prospect was used as a ‘blind’ target as there was no background information available until after interpretation was carried out. Mineralisation was located at the contact between granite and dolerite, biogeochemical signatures from E. brevifolia and Acacia bivenosa showed areas of change in ±Au, Ba, Ce, ±Cu, La, ±Mn, Nd, P, S, Sm, Y and Zn which corresponded to this contact. All species in the Pine Creek Orogen were able to present areas elevated in Au, As, ±Zn, ±S, ±Mo and ±Cu which provide future drilling targets. Biogeochemical sampling was able to determine the location of mineralisation at each site and identify underlying substrate changes, however, background knowledge relating to regolith, geology, hydrology and geophysics are important in aiding the interpretation of the elemental data as each component of the substrate influences the elements which a plant will uptake. Mineral exploration in Australia has been driven by the search for large ore deposits close to the surface. This has led to the need to develop technologies for detecting mineral deposits under cover...

Multi-mineral cut-off grade optimization by grid search

Cetin, E.; Dowd, P.
Fonte: South African Inst Min Metall Publicador: South African Inst Min Metall
Tipo: Artigo de Revista Científica
Publicado em //2013 EN
Relevância na Pesquisa
56.59%
Orebodies that contain more than one economically important mineral are generally evaluated by parametric cut-off grades. This approach often leads to mis-valuation of mineral deposits because cut-off grades are not based on the grades of each individual mineral and, because of the parametric formulation, are only indirectly related to the individual grade distributions. The only realistic approach is a formulation that accounts separately for each component mineral. The grid search method can be used as a means of multi-mineral cut-off grade optimization in this context. This paper describes the use of the grid search method in cut-off grade optimization for multi-mineral deposits. The authors introduce the general concepts of the method and formulate its application to cut-off grade optimization; they describe a software implementation of the method that can accommodate cut-off grade optimization for mineral deposits that contain up to three economic minerals.; E. Cetin and P.A. Dowd

An integrated risk evaluation model for mineral deposits.

Nicholas, Grant Deon
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2014
Relevância na Pesquisa
56.51%
The core asset of most mining companies is its mineral resources and reserves. The company produces ore from its reserves, which is a subset of its mineral resources associated with varying levels of geoscientific confidence and uncertainty. One of the key evaluation challenges is to distil technical complexity into a financial model that is usually designed to focus only on one or two key valuation indicators, such as net present value (NPV) or internal rate of return (IRR). The driver behind this research was whether conventional evaluation techniques for mineral projects can evaluate accurately both the spatial and temporal characteristics of project risks in financial terms, due to their inherent nature to understate the true variance, and under-value or over-value the actual NPV. How can conventional evaluation methods be compared to an innovative, integrated evaluation technique that quantifies the non-linear impacts of spatial resource variables on production constraints in financial terms, measured at the appropriate temporal scale? To answer these questions, this research focused on developing an innovative risk evaluation methodology for two different diamond deposits and one gold deposit to incorporate spatial, non-spatial and financial data across the evaluation pipeline. The author developed an integrated evaluation modelling (IEM) framework based on a unique bottom-up methodology that follows every estimation block through the mining and processing value chain...

Geogenic factors as drivers of microbial community diversity in soils overlying polymetallic deposits

Reith, F.; Zammit, C.M.; Pohrib, R.; Gregg, A.L.; Wakelin, S.A.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em //2015 EN
Relevância na Pesquisa
56.49%
This study shows that the geogenic factors landform, lithology and underlying mineral deposits (expressed by elevated metal concentrations in overlying soils) are key-drivers of microbial community diversity in naturally metal-rich Australian soils with different landuse, i.e., agriculture vs. natural bushland. 168 soil samples were obtained from two metal-rich provinces in Australia, i.e., the Fifield Au-Pt-field (New South Wales) and the Hillside Cu-Au-U-rare-earth-element (REE) deposit (South Australia). Soils were analyzed using three-domain multiplex terminal-restriction-fragment-length-polymorphism (M-TRFLP) and PhyloChip microarrays. Geogenic factors were determined using field-mapping techniques and analyses of >50 geochemical parameters. At Fifield, microbial communities differed significantly with geogenic factors and equally with landuse (P<0.05). At Hillside, communities in surface soil (0.03-0.2 m depth) differed significantly with landform and landuse (P<0.05). Communities in deeper soils (>0.2 m) differed significantly with lithology and the mineral deposit (P<0.05). Across both sites, elevated metal contents in soils overlying mineral deposits were selective for a range of bacterial taxa, most importantly Acidobacteria...

Iron Deposits in Southwestern Indiana

Bundy, Wayne M.
Fonte: Indiana Geological Survey Publicador: Indiana Geological Survey
Tipo: Relatório Formato: 1716655 bytes; application/pdf
EN_US
Relevância na Pesquisa
46.52%
Indiana Geological Survey Report of Progress 10; Most of the iron deposits of Martin and Greene Counties, Ind. , are within the Mansfield formation (lower Pennsylvanian), but small deposits also occur in the Beech Creek limestone (upper Mississippian). Goethite, the major iron mineral, occurs as cementing material, concretions, bands along bedding planes, veins, irregular open-space fillings, and replacements of plants in sandstone and shale. Small replacement bodies of goethite are common in the limestone. Magnetite occurs as finely disseminated grains within the interior shells of concretions. Iron deposits in Indiana probably were precipitated in swamps and lagoons in early Pennsylvanian time. The belief that the iron was deposited in bogs is substantiated by the following evidence: (1) the irregular and local distribution of the iron deposits in Indiana is characteristic of bog iron deposits; (2) the relative abundance of those plant fossils associated with iron deposits is similar for both the iron deposits in Indiana and bog iron deposits; (3) the chemical analyses of the iron deposits in Indiana are similar to other iron deposits that are known to be of bog origin; (4) clay that is similar in composition to underclay (indicative of swamp conditions) is present in the Indiana deposits; and (5) the syngenetic nature of the concretions and the abundance of concretions of the Indiana deposits are like those of other iron deposits that are known to be of bog origin. Shrinkage cracks and colloform texture indicate that the iron was largely a colloidal precipitate. Electrolytes...

Malawi - Mineral Sector Review : Source of Economic Growth and Development

World Bank
Fonte: World Bank Publicador: World Bank
Tipo: Economic & Sector Work :: Mining/Oil and Gas
ENGLISH
Relevância na Pesquisa
46.35%
This mineral sector review examines the mineral sector as a potential source of growth and development in Malawi. In seeking the World Bank's assistance the Government of Malawi was particularly interested in confirming the potential for mineral sector growth, identifying which constraints to the development of the sector need to be addressed by the Government and suggesting strategies to foster a positive contribution by the mineral sector to sustainable development and poverty reduction. This report is organized into four chapters. Chapter one examines the potential for mineral sector growth in the short, medium and long term and indicates the direct and indirect economic and development benefits that could result. The remaining chapters address constraints that could prevent the mineral sector's full potential from being realized, especially those that can be addressed by government action, focusing on the development of efficient and effective legal, regulatory and institutional arrangements for managing the mineral sector (chapter two); the design of robust mineral revenue generation and management regimes (chapter three); and the creation of sound arrangements for the environmental and social management of the mineral sector (chapter four). Each chapter concludes with a summary of the main findings and recommendations for action with an indicated timeframe.

Mineral Rights Cadastre : Promoting Transparent Access to Mineral Resources; Cadastres miniers : promotion d'un acces transparent aux ressources minerales Catastro minero : promoviendo la transparencia en el acceso a los recursos minerales

Ortega Girones, Enrique; Pugachevsky, Alexandra; Walser, Gotthard
Fonte: World Bank, Washington, DC Publicador: World Bank, Washington, DC
Tipo: Publications & Research :: Working Paper; Publications & Research
ENGLISH; EN_US
Relevância na Pesquisa
46.3%
This document proposes a set of generally applicable recommendations and good practices for creating a Mineral Rights Cadastre (MRC), an administrative body responsible for overseeing the process of granting and managing mineral licenses throughout a country. The document reviews lessons learned from World Bank-funded projects aimed at reforming mineral rights management and assesses the impacts and benefits of the implemented changes. The document focuses on the MRC system as a key regulatory agency of mining sector administration. This study is also intended to fill a gap in the literature on mining sector administration, as few publications since roughly the 1930s have been dedicated to the overall analysis of MRCs, particularly in relation to modern and recent mining cadastral practices. While the overall concepts and principles presented in this document are intended to be universally valid and applicable, there is no single solution to mining sector development, and it would be unrealistic to believe that actions that have been successful in one country can be directly transferred to others. The MRC of any given country will need to be adapted to that particular country's culture...

Towards Sustainable Mineral-Intensive Growth in Orissa : Managing Environmental and Social Impacts

World Bank
Fonte: Washington, DC Publicador: Washington, DC
Tipo: Economic & Sector Work :: Country Environmental Analysis (CEA); Economic & Sector Work
ENGLISH; EN_US
Relevância na Pesquisa
46.31%
The study's objective was to support the socio-economic development program of the Government of Orissa by helping to analyze and formulate practical strategies for strengthening an institutional and regulatory framework with respect to managing the environmental and social impacts of investments in the mining and industry sectors. This study, conducted for about a year, focused on two sets of issues: (i) the need to create mechanisms to share the concentrated benefits of mineral-intensive investments across the community, and (ii) the need to address the externalities of accelerated mineral-intensive through improved enforcement and compliance of environmental and mining regulations. Significant attention was given to the capacity needs of the Orissa Pollution Control Board (OPCB), as the main agency to monitor and enforce compliance with environmental regulations and standards. This analytical work was undertaken with strong support from the Department of Environment (DOE), the Orissa Pollution Control Board (OPCB)...

Geochronology of Mexican mineral deposits. I: the San Martín polymetallic skarn, Zacatecas

Camprubí,Antoni; González-Partida,Eduardo; Valencia,Victor A.; Barra,Fernando
Fonte: Sociedad Geológica Mexicana, A.C. Publicador: Sociedad Geológica Mexicana, A.C.
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2015 EN
Relevância na Pesquisa
56.49%
The Zn-Pb-Cu(-Ag±Au) San Martín deposit in northwestern Zacatecas is one of the most economically important and biggest skarns in Mexico. Mineral associations in this deposit belong to the sulfide skarn type (with rather "classical" prograde and retrograde zones) and contain peripheral subepithermal to epithermal veins. Re-Os ages were obtained for two molybdenite samples from deep Cu-Zn-Pb±Mo±Bi±Ag retrograde mineralization in these deposits, of 43.7 ± 0.3 and 44.0 ± 0.2 Ma, which correspond essentially to the same age. These are 1 to 3 Myr younger than preexisting K-Ar ages for the granitic stock that generated these mineral deposits. Prograde mineral associations are hereby interpreted to have been directly associated with this intrusion. Therefore, we may calculate a simple decrease rate in temperatures of hydrothermal fluids between ~100º and > 300 ºC per million years from prograde to retrograde skarn associations. Subepithermal and epithermal veins, however, remain undated.

Multi-mineral cut-off grade optimization by grid search

Cetin,E.; Dowd,P.A.
Fonte: Journal of the Southern African Institute of Mining and Metallurgy Publicador: Journal of the Southern African Institute of Mining and Metallurgy
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2013 EN
Relevância na Pesquisa
56.59%
Orebodies that contain more than one economically important mineral are generally evaluated by parametric cut-off grades. This approach often leads to mis-valuation of mineral deposits because cut-off grades are not based on the grades of each individual mineral and, because of the parametric formulation, are only indirectly related to the individual grade distributions. The only realistic approach is a formulation that accounts separately for each component mineral. The grid search method can be used as a means of multi-mineral cut-off grade optimization in this context. This paper describes the use of the grid search method in cut-off grade optimization for multi-mineral deposits. The authors introduce the general concepts of the method and formulate its application to cut-off grade optimization; they describe a software implementation of the method that can accommodate cut-off grade optimization for mineral deposits that contain up to three economic minerals.