Thèses sur le sujet « Mineral occurrence »

A mathematical model describing the probability for n mines or prospects occurring within an elementary unit (cell) of an area has been referred to as an occurrence model. Estimation of parameters of occurrence models has been plagued by the effect of area delineation on the parameters. Moreover, incompleteness of exploration creates a bias in parameter estimates. This study proposes that when the model is to describe the probability for occurrence of mines or prospects, the appropriate area is a metallogenic unit of mining district scale. Accordingly, this study examined the delineation of area by successive expansion of a polygon seeking that size of area which provides the best fitting of a truncated and effort-adjusted exponential model. However, estimation of occurrence model parameters was found to be sensitive to location of polygon on the cluster. Consequently, this approach was abandoned in favour of geologically-defined metallogenic units referred to as Intrinsic Samples. Truncated and effort adjusted occurrence models were fitted to Intrinsic Samples which included the mining districts of the Walker Lake Quadrangle of Nevada and California. The estimated model for each metallogenic unit is used to estimate the gold-silver metal endowment of the unit. This represents a departure from previous studies, e.g. Allais, in which a single parameter estimate from a control area is used to estimate the mineral endowment in all parts of a large study area. Furthermore, the study addresses the issue of economic truncation of occurrence data used in exponential model construction. Because a metallogenic unit is less than completely explored, estimated parameters based on observed occurrences provide a biased description of the number of occurrences present (i.e. endowment). The transition from sample to endowment (population) parameter is achieved by parameterizing the exponential model for a metallogenic unit on exploration effort deployed in a unit area. Thus, fitting the model to observed data and evaluating it at infinite effort yields the model for gold and silver metal endowment in a metallogenic unit.

Thesis (B. Sc.(Hons.))--University of Adelaide, Dept. of Geology and Geophysics, 1997.
Tennant Creek 1:250 000 sheet (SE 53-14) Green Swamp Well 1:250 000 sheet (SE 53-13). Includes bibliographical references (leaves 42-43).

CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel Superior
This study embraces the west continental shelf of Cearà (147 samples of marine sediments) and two fluvial courses (4 sediment samples of Curu and SÃo GonÃalo rivers) to determine heavy minerals distribution with their possible provenances and economic potential. Sedimentary facies on the continental shelf were distinguished through the particle size and calcium carbonate content. Heavy minerals were investigated for their total content (%), relative abundance (%) of each mineral species, concentration in Kg/ton of predominant species, mineralogical index (RZi and ZRT) and grains imaging by SEM-EDS. In geoprocessing obtained the spatial distribution of data by Arcgis 10.1 and Surfer 10 got informations about bottom morphology of the continental. Multivariate analysis were included using Statistica 7.0 to aid in the interpretation of results. Heavy minerals were concentrated in Fortaleza chart (contents reached to 4.54%) at depths until 20 m in the litoclastic and litobioclastic sands. Among the 18 mineral species identified, ilmenite and tourmaline were embracing most of the continental shelf and with epidote and monazite presented content > 1 Kg/ton near SÃo GongaÃo do Amarante coast. Paleochannels and ancient beach-ridge were identified. The occurrence of typical regional metamorphic mineral paragenesis of rocks rich in aluminum suggests the provenance of Cearà Complex rocks (primary source) that occur both near the coast and outcrops directly on the continental shelf. Reworked sediments of Barreiras Formation, beach black sands and longshore drift sediments (secondary sources) contribute regionally in heavy mineral supply.Curu river influences ilmenite, tourmaline and epidote supply. Multivariate analyzes and RZi/ZTR variations corroborated with the dual nature provenance (primary and secondary) of the continental shelf sediments and expose a mixture of recente sediments with older reworked ones.
Este estudo abrange a plataforma continental oeste do Cearà (147 amostras de sedimentos marinhos) e dois cursos fluviais (4 amostras de sedimentos dos rios Curu e SÃo GonÃalo) para determinar a distribuiÃÃo dos minerais pesados com suas possÃveis proveniÃncias e potencial econÃmico. Distinguiram-se as fÃcies sedimentares da plataforma continental pela granulometria e teor de carbonato de cÃlcio. Os minerais pesados foram investigados pelos seus teores totais (%), abundÃncias relativas (%) de cada espÃcie mineral, teores em Kg/ton das espÃcies predominantes, Ãndices mineralÃgicos (RZi e ZRT) e imageamento dos grÃos por MEV-EDS. No geoprocessamento obteve-se a espacializaÃÃo dos dados pelo Arcgis 10.1 e informaÃÃes da morfologia de fundo da plataforma continental com o Surfer 10. IncluÃram-se anÃlises multivariadas por meio do Statistica 7.0 para auxiliar na interpretaÃÃo dos resultados. Os minerais pesados se concentraram na folha Fortaleza (teores de atà 4,54%) em atà 20 m de profundidade e nos domÃnios das areias litoclÃsticas e litobioclÃsticas. Dentre as 18 espÃcies minerais identificadas, a ilmenita e a turmalina foram as que abrangeram a maior parte da plataforma continental e juntamente com epÃdoto e monazita apresentaram teores > 1 Kg/ton prÃximo à costa de SÃo GonÃalo do Amarante. Foram identificados paleocanais e antigas linhas de praia. A ocorrÃncia da paragÃnese mineral tÃpica de metamorfismo regional de rochas ricas em alumÃnio sugere a proveniÃncia das rochas do Complexo Cearà (fonte primÃria) que ocorrem tanto prÃximo à costa como afloram diretamente na plataforma continental. Sedimentos retrabalhados da FormaÃÃo Barreiras, areias pretas praiais e sedimentos de deriva litorÃnea (fontes secundÃrias) contribuem regionalmente no aporte de minerais pesados. O Rio Curu exerce influÃncia no aporte de ilmenita, turmalina e epÃdoto. As anÃlises multivariadas e as variaÃÃes de RZi e ZTR corroboraram com a proveniÃncia de natureza dual (primÃria e secundÃria) dos sedimentos plataformais, alÃm de expor uma mistura de sedimentos recentes com sedimentos retrabalhados mais antigos.

The Tjårrojåkka area is located about 50 km WSW of Kiruna, northern Sweden, and hosts one of the best examples of spatially related Fe-oxide Cu-Au occurrences (the Tjårrojåkka-Fe and Tjårrojåkka-Cu). The bedrock, depositional environment and tectonic evolution of the area were studied through petrological, geochemical and geophysical-petrophysical investigations. The bedrock is dominated by intermediate and basic extrusive and intrusive rocks. The intermediate andesites and basaltic andesites are cut by diabases which acted as feeder dykes for the overlying basalts. The intrusive rocks range from gabbro to quartz-monzodiorite in composition. The area is metamorphosed to epidote-amphibolite facies and has been affected by scapolite, K-feldspar, epidote and albite alteration that is more intense in the vicinity of deformation zones and mineralisations. Based on geochemistry the andesites and basaltic andesites are similar to the Svecofennian Porphyrite Group intermediate volcanic rocks, but have also features common with the intermediate volcaniclastic unit in the underlying Kiruna Greenstone Group. Chemically the basalts and diabases have the same signature, but cannot directly be correlated with any known basaltic unit. Some of the samples have characteristics comparable to the basalts of the Kiruna Greenstone Group. Whether the volcanic sequence at Tjårrojåkka represents the Porphyrite Group or is part of the greenstones could not be unequivocally determined without geochronological data. Three events of deformation have been distinguished in the Tjårrojåkka area; the first one involving NW-SE compression creating NE-SW-striking steep foliation corresponding with the strike of the Tjårrojåkka-Fe and Cu bodies, followed by the creation of an E-W deformation zone. Finally a second compressional event resulted in folding and the formation of a NNW-SSE striking and gently dipping structure possible related to thrusting from SW. The Tjårrojåkka apatite-magnetite ore (52.6 Mt of iron ore @ 51.5% Fe) is a blind ore consisting of a massive magnetite core surrounded by an ore- breccia containing low-grade Cu-mineralisation. Apatite, amphiboles and carbonate occur disseminated and as veins within the massive ore and in the wall rock. The Tjårrojåkka-Cu mineralisation is located 750 m from the Tjårrojåkka-Fe and contains 3.23 Mt ore @ 0.87% Cu. The main ore minerals are chalcopyrite and bornite occurring both disseminated and in veinlets. Minor pyrite, molybdenite and gold have also been observed. The host rock has been affected by strong albite, scapolite, amphibole and K-feldspar alteration. The alteration assemblages at Tjårrojåkka are highly variable with several of the alteration minerals occurring in several generations and settings, and with multiple reactivations of already existing veins and overlapping alteration stages indicating a complex, long history of fluid activity in the area. Similarity in alteration minerals and paragenesis in the iron and copper mineralisation is described in terms of whole rock geochemistry, mineral chemistry and paragenesis. This may partly be explained by the common host rock to the mineralisations, but indicates also similarities in fluid composition. Within the massive magnetite ore apatite, tremolite and carbonate veinlets fill fractures probably formed during cooling of the magnetite body. The wall rock has been affected by extensive pervasive albite and plagioclase alteration. Scapolite occurs locally as porphyroblasts and later veins. The albitised and scapolitised rocks are overprinted by pervasive K-feldspar alteration and veins of K-feldspar + Mg-hornblende ± titanite ± quartz ± magnetite ± sulphides along the foliation. Epidote is common in veins together with K-feldspar. Allanite occurs as an accessory mineral associated with epidote, otherwise REE-minerals are rare. Carbonate and zoelites were the last phases to form in vacancies. The area between the apatite-iron and copper bodies is strongly albite + magnetite altered. The footwall of the copper body is characterised by pervasive albite alteration spatially associated with magnetite and apatite veins cut by later carbonate veinlets. Scapolite (porphyroblasts and veins) is formed in an early stage in the hanging wall overprinted by pervasive K-feldspar alteration. Amphiboles (tschermakites, Mg-hornblende and actinolite) occur in several generations as porphyroblasts, in veins on its own, or together with K-feldspar ± titanite ± quartz ± carbonate ± chalcopyrite ± bornite. Epidote, REE- carbonate, zeolites and fluorite are the latest alteration phases in the copper mineralisation. Ba, Cl, S and F are enriched in the alteration minerals in the Tjårrojåkka occurrences. Barium-rich varieties of K-feldspar (max. 3.5% BaO) occur in the Cu-mineralised breccia surrounding the apatite-magneitie body indicating high concentrations of Ba in the hydrothermal fluids. Absence of sulphate in the fluids probably caused the formation of Ba-feldspars instead of barite. Scapolite shows a trend with more Cl-rich varieties around the magnetite body gradually getting more SO3 and CO2-rich in the Cu-mineralisation. The presence of accessory barite in the copper mineralisation also indicates that the SO3 content in the fluids were higher than in the iron ore. The biotites are rich in Ti while Cl and F contents are more moderate and do not show great variation in different parts of the systems. All amphiboles are Ca-rich ranging from tschermakites, Mg-hornblende to actinolite and tremolite. The apatites are F-dominate with higher Cl content in the apatite- iron ore than in the copper occurrence. Overall the alteration minerals related to the apaite-iron ore are more rich in Cl and Ba than the ones in the Cu-mineralisation that show higher contents of F, SO3 and CO2.
Godkänd; 2003; 20070215 (ysko)

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As formigas são insetos sociais com características próprias que as propiciam habitarem e se dispersarem à todos ambientes terrestres. Algumas espécies podem causar prejuízos e danos ao homem, e ainda atuarem como vetores patogênicos em hospitais. Este estudo objetivou identificar as espécies de formigas presentes em um hospital da Zona da Mata Mineira, determinar o número médio de formigas visitando a isca por hora (NMFVIH), a similaridade entre os setores, a variação da diversidade nos períodos seco e chuvoso, além de identificar as estruturas físicas utilizadas como recurso para nidificação. Para a coleta da formigas foram utilizadas iscas atrativas não tóxicas, distribuídas a cada dez metros de distância nos seguintes setores: UTI Neonatal (UN), UTI Pediátrica (UP), Enfermaria Feminina (EF) e Entorno Hospitalar (EH). Registraram-se 42 espécies de formigas e quanto à riqueza obteve-se UN (n=4), UP (n=7), EF (n=13) E EH (n=30). Seis espécies foram classificadas como constantes, destacando-se Camponotussp.9, com 100% de ocorrência; 21 acessórias e 15 acidentais; Camponotus sp.4, Hylomyrmasp e Linepithemasp foram encontradas em todos setores. A subfamília Myrmicinae apresentou o maior índice de ocorrência (76,09%) e Ectatomminae com o menor (<0,01%). Os setores internos tenderam à similaridade, com exceção da UN no período seco e o número médio de formigas visitando a isca por hora diferiu significativamente entre as áreas interna e externa. O período de maior ocorrência foi entre às 12:00 e 17:59, período da tarde. Foram quantificados 28 ninhos, Interior Hospitalar (IH=23) e Entorno Hospitalar (EH=5), a categoria fresta foi a estrutura física mais utilizada (n=16) e tubulação (n=1) a menos. A espécie Camponotus sp.9 e Hylomyrmasp.1 nidificaram tanto no EH como no EF. A espécie registrada que mais se distanciou do ninho para forragear foi Attini sp.2 e a que menos se distanciou foi Linepithema sp.1. Conhecer a distribuição física do hospital, das formigas infestantes e a localização dos ninhos pode ser importante para determinar estratégias de controle.
The ants are social bugs with own characteristics that offer them to live and scatter to all terrestrial environments. Some species can cause damage and harm to humans, and still act as pathogenic vectors in hospitals. This study aimed identify the species of ants at a hospital in Zona da Mata Mineira, to determine the average number of ants visiting the bait by hour (NMFVIH), the similarity between the sectors, the variation of diversity in dry and rainy season, besides, identify the physical structures used as a resource for nest building. The ants were collect with non-toxic attractive bait distributed at each ten meters of distance in the following sectors: Neonatal ICU (NI), Pediatric ICU (PI), Women's Infirmary (WI), and the Surrounding area of the Hospital (HS). 42 species of ants were registered and the following diversity of species NI (n=4), PI (n=7), WI (n=13) and HS (n=30). Six species were classified as constant with emphasis for the Camponotussp.9, with 100% of occurrence; twenty-one ancillaries and fifteen accidentals; Camponotus sp.4, Myrmicini sp.1 and Linepithema sp.1 were found in all sectors. The subfamilyMyrmicinae had the highest rate of occurrence (76,098%) andEctatominae with the lowest (<0,01%). The internal sectors tended to similarity, except the NI in the dry season and the average number of ants visiting the bait per hour differed significantly between internal and external areas. The period of higher occurrence of ants used to be between 12:00 PM and 5:59 PM.28 nests were quantified in Area Interior (AI=23) and Area Around (AA=5), the gap category was the most used physical structure (n=16) and tubing (n=1) the lower. The species Camponotus sp.9 and Hylomyrmasp.1 nested both in HI and the HS. The registered species that more distanced itself from the nest to forage was Attini sp.2 and the one that less distanced it was Linepithema sp.1. The results showed that knowing the physical distribution of the hospital, the infesting ants and the location of the nests can be important for control strategies.

Os minerais do grupo do pirocloro (A2B2X6Y1) apresentam grande interesse econômico, principalmente como fonte de nióbio e tântalo, metais que possuem importantes aplicações tecnológicas como a fabricação de aço e a confecção de componentes eletrônicos. Apesar de seu interesse científico e econômico, a maioria das ocorrências brasileiras de minerais do grupo do pirocloro está apenas parcialmente caracterizada ou não dispõe de nenhum estudo mineralógico. Adicionalmente, o atual sistema de classificação dos minerais do grupo do pirocloro, apesar de aprovado pela IMA, não segue as regras gerais de nomenclatura de minerais da própria IMA. Na posição A, não há diferenciação na ocupação por Ca e por Na, e se um ou mais cátions diferentes de Na ou Ca compuserem mais de 20 % total de átomos na posição A, então a espécie é nomeada pelo átomo mais abundante em A (exceto Na e Ca). Por outro lado, a espécie fluornatromicrolita foi aprovada com base na predominância de Na na posição A. Com relação à ocupação da posição B, a divisão entre os grupos não é feita com uma classificação tripartite: as espécies com Nb + Ta >2Ti e Nb > Ta são consideradas como do subgrupo do pirocloro; se Nb + Ta > 2Ti e Ta ≥ Nb, o mineral irá pertencer ao subgrupo da microlita; e se 2Ti ≥ Nb + Ta, o mineral irá pertencer ao subgrupo da betafita. Espécies isoestruturais com outros cátions predominantes na posição B não são incluídas no grupo do pirocloro (por exemplo, romeíta com Sb dominante). Os ânions não são levados em consideração na classificação, mas o flúor foi usado na aprovação da espécie fluornatromicrolita. Neste trabalho, são apresentados novos esquemas de nomenclatura para os minerais do grupo do pirocloro, que levam em consideração os íons ocupantes das posições A, B e Y. Os prefixos são sempre escritos por extenso (\'hidroxi\', \'fluor\', \'calcio\', \'natro\' etc), enquanto os sufixos são representados por símbolos químicos (Na, F, H2O etc) ou por [] (vazio). Os nomes raízes relacionam-se aos cátions predominantes na posição B, levando a termos como pirocloro, microlita, betafita e romeíta. São apresentados novos dados químicos por MEV-EDS e WDS (incluindo análises de Si, normalmente negligenciado na maioria dos dados da literatura). Foram analisados minerais de seis ocorrências em pegmatitos e uma em carbonatito. Os resultados obtidos permitem separar as espécies em três \'famílias\'. A primeira delas poderia ser denominada \'microlita\', envolvendo fluornatromicrolita, fluorcalciomicrolita, oxinatromicrolita e oxicalciomicrolita. Esta família foi identificada nas ocorrências da lavra do Morro Redondo, Coronel Murta, MG; lavra do Jonas, Conselheiro Pena, MG; mina Quixabá, Frei Martinho, PB; Pegmatito Volta Grande, Nazareno, MG; lavra do Ipê, Marilac, MG; e Pegmatito Ponte da Raiz, Santa Maria de Itabira, MG. A primeira das espécies, fluornatromicrolita, parece ser bem mais comum do que se imaginava, tendo sido descrita previamente no Brasil apenas em Quixabá, e agora verificada em diversas das ocorrências estudadas nesta tese. Apesar de usados os prefixos natro e cálcio, todas as amostras parecem tender para um termo de fórmula final (NaCa)Ta2O6F, ou seja, com Na=Ca em apfu, que poderia ser denominado, por exemplo, fluormicrolita-NaCa ou CaNa. O oxigênio é, algumas vezes, superior ao flúor (em apfu) na cavidade Y, dando origem a espécie oxi-. A segunda família poderia ser denominada \'hidromicrolita\', tendendo a [ [](H2O)]Ta2O6(H2O). Esta fórmula, entretanto, não é eletricamente neutra, necessitando que na cavidade A, (H2O) seja parcialmente substituído por cátions (Ba, U etc), ao mesmo tempo que parte do O da posição X seja substituído por (OH). Minerais desta família foram verificados no Pegmatito Volta Grande, Nazareno, MG. A terceira família, do \'pirocloro\', verificada apenas no carbonatito da mina Jacupiranga, Cajati, SP, inclui as espécies fluorcalciopirocloro e oxicalciopirocloro. Os novos nomes sugeridos parecem discriminar melhor as espécies, com base em cátions, vazios ou H2O predominantes nas posições A, B eY, permitindo inclusive uni-las em \'famílias\'. Esta nova nomenclatura apresenta também como vantagem não dar ênfase a componentes menores da cavidade A, bem como verificar nela a predominância de Ca ou Na. Adicionalmente, os cátions Ta, Nb e Ti passam a ter a mesma importância na cavidade B. Por outro lado são criados nomes \'exóticos\', como hidrohidromicrolita, ou \'impronunciáveis\', como hidro-[]-microlita.
Pyrochlore group minerals are important sources of niobium and tantalum and these metals are used in important technological applications such as steel manufacturing and eletronic components development. However, the majority of Brazilian occurrences are only partially characterized or there is no mineralogic study available. In addition, the official pyrochlore-group minerals classification system does not follow the IMA mineralogical nomenclature rules although this system is approved by IMA. In the A site, it does not differentiate between occupation by Ca and Na, and if there is one or more cation other than Na or Ca composing more than 20% of total A-atoms, then the species must be named according to the most abundant A-atom, other than Na or Ca. In spite of this, the species fluornatromicrolite was approved based on the predominance of Na in the A-site. Regarding the B-site occupation, the division among the subgroups is not made with a tripartite symmetrical classification: the species with Nb + Ta >2Ti and Nb > Ta are considered as pyrochlore subgroup minerals; if Nb + Ta > 2Ti and Ta ≥ Nb, the mineral will belong to the microlite subgroup; and if 2Ti ≥ Nb + Ta, the mineral will belong to the betafite subgroup. Isostructural species with other predominant cations in the B-site are not included in the pyrochlore-group (for example, romeite, with dominant Sb). The anions are not taken into account in the classification but the predominance of fluorine was used for the approval of the species fluornatromicrolite. In this present work new nomenclature schemes, based on the ions in A, B and Y sites, are presented. Prefixes are, for example, \'hidroxi\', \'fluor\', \'calcio\', \'natro\' etc., while sufixes are represented by chemical symbols (Na, F, H2O etc) or [] (vacancies). The root names (pyrochlore, microlite, betafite, romeite) are related to the dominant-constituent cations in the B position. New chemical data by MEV-EDS and WDS (including Si analysis, hardly ever mentioned in litetarature) were obtained. Six occurrences from pegmatites and one from carbonatite were analysed. The results allow the species to be grouped in three \'families\'. The first could be named as \'microlite\', and includies fluornatromicrolite, fluorcalciomicrolite, oxinatromicrolite and oxicalciomicrolite. This family was identified in Morro Redondo quarry, Coronel Murta, MG; Jonas quarry, Conselheiro Pena, MG; Quixabá mine, Frei Martinho, PB; Volta Grande pegmatite, Nazareno, MG; Ipê quarry, Marilac, MG and Ponte da Raiz pegmatite, Santa Maria de Itabira, MG. Fluornatromicrolite seems to be more common than was previously thought. It was previously described only in Quixabá but now many other occurrences are known. Although \'natro\' and \'calcio\' prefixes were used, all the formulae seem to approach the term (NaCa)Ta2O6F. As Na approximately equals Ca (apfu) it could be used the name fluornatromicrolite-Na-Ca or CaNa could be used. The oxigen content is sometimes greater than F content in the Y position. This generates the oxi- species. The second family could be named \'hidromicrolite\', becoming [ [] (H2O)]Ta2O6(H2O). This formulae is not eletrically neutral so the H2O is replaced by cations (Ba, U etc) in the A cavity while the O is replaced by (OH) in the X position. Minerals from this family were identified in the Volta Grande pegmatite, Nazareno, MG. The third family, \'pyrochlore\', was only verified in the Jacupiranga mine, Cajati, SP, including fluorcalciopyrochlore and oxicalciopyrochlore species. The suggested new names, based on cations, vacancies or H2O dominant constituents of A, B and Y sites, seem to better describe the species, allowing their grouping in families. This new nomenclature has the advantage of not emphasize minor constituents in the A cavity, and verify the dominance of Ca or Na. Furthermore, Ta, Nb and Ti cations have the same balance in B cavity. On the other hand, exotic names were created such as hydrohydromicrolite or unpronounceable as hydro-[]-microlite.

Le district de Litsa est une région de la Péninsule de Kola particulièrement prometteuse pour la métallogénie de l'uranium. Présentant toutes les caractéristiques d'une province métallifère, ce district a enregistré une histoire géologique complexe avec des enrichissements successifs en uranium. Trente anomalies uranifères y sont observées, estimées à 102 000 tonnes (IAEA nomenclature), pour une teneur moyenne de 0,01%. Elles sont encaissées dans différentes formations de niveau structural et d'âge différents, depuis l'Archéen jusqu'au Calédonien. La minéralisation présentant les teneurs en uranium les plus économiques sont des veines de pechblende observées autour du complexe granitique de Litsa-Araguba, où sont présents des protolites, des structures et des phénomènes épigénétiques favorables
The Litsa district is one of the most interesting areas of the Kola Peninsula with respect to uranium metallogenesis. Presenting all the features of uraniferous province, it endured a protracted geological history with several successive uranium enrichments. There are over 30 uranium occurrences and manifestations, totally estimated at 102,000 tons in Speculative Resources (IAEA nomenclature), with an average grade of Uranium 0.01%. They occur at different stratigraphic levels of the geological succession in the district: Archean, Paleoproterozoic, Mesoproterozoic and Paleozoic. Uranium content in the geological formations gradually increases during the geological evolution of the Litsa district from Archean to Paleozoic. The most abundant and probably prospective for the economic-grade uranium mineralization is Paleozoic pitchblende vein type, located around the Litsa-Araguba granitoid complex, where favorable protoliths, structures and epigenetic processes are encountered

L’Anti-Atlas marocain est une vaste province géologique composée d’un socle précambrien et d’une couverture sédimentaire tardi-néoprotérozoïque à paléozoïque. Plus de 200 occurrences cuprifères sont répertoriées dans cette couverture. Avec l’augmentation de la demande mondiale en cuivre depuis les années 2000, ces minéralisations, considérées non rentables dans les années 1980, sont désormais d’intérêt économique majeur pour les compagnies minières. Outre cet intérêt économique, ces occurrences restent un mystère scientifique du point de vue de leur genèse. En effet, les quelques études existantes sur ces objets ne permettent pas d’établir un modèle métallogénique clair expliquant la formation de ces concentrations à cuivre. Notre étude est centrée sur la boutonnière de Bou Azzer-El Graara (Anti-Atlas central). Elle propose de réaliser une synthèse des minéralisations de ce secteur basée sur quatre axe : (1) une étude de terrain à l’échelle des objets minéralisés, (2) une caractérisation minéralogique et texturale des minéralisations, (3) une approche statistique appliquée aux bases de données roche totale de ces occurrences, (4) une étude des inclusions fluides des minéraux de gangue associés au cuivre. Les résultats ont montré que l’ensemble des minéralisations de la couverture avait une texture en stockwork et une minéralogie identique auto-similaire à toute les échelles d’observation, et ce indépendamment de la morphologie des corps. Ce stockwork est contemporain de zones plissées et faillées. Il est contemporain du mouvement de failles du socle Précambrien rejouant au Varisque et induisant la circulation de saumures profondes minéralisant le socle précambrien comme la couverture néoprotérozoïque à cambrienne de cette boutonnière
The Anti-Atlas belt is a large geological province. It is composed by a Precambrian basement and a Neoproterozoic to Paleozoic sedimentary cover. More than 200 copper occurrences are localized in this cover. Since the 2000s, with the increase of global copper demand, these mineralizations have a great economic interest for mining company. Besides economic interests, the scientific understanding of these mineralizations in this area are not clear. It does not exist a global model to explain the formation of these deposits. Our study is focus on the Bou Azzer-El Graara inlier (central Anti-Atlas). We proposed to realize a synthesis of copper deposits in this area based on four axes: (1) a field study at the ore bodies’ scale, (2) a mineralogical and textural characterization of these mineralizations, (3) a statistical approach applied to rock total data bases of these deposits, (4) a study of fluid inclusions associated to the ore gangue minerals. Results showed that the whole of mineralizations in the Neoproterozoic to Cambrian cover have a same stockwork texture and a same mineralogy at all scales of observations and that, independently of the ore bodies morphology. This stockwork is synchronous of folded and faulted zones. It is too synchronous of Precambrian basement faults movements during the Variscan compression. These movements are link to deep brines circulations responsible of copper mineralizations localized in the Precambrian basement and in the Neoproterozoic to Cambrian cover of this inlier

碩士
臺北醫學大學
傷害防治學研究所
95
Purpose: To investigate the relation between bone mineral density (BMD) level and falls occurrence in elderly people and osteoporosis is one of the risk factors of falls. Method: The is a case-control study, we investigated 80 cases out of 94 patients consecutively admitted to emergency department of Taipei county hospital San-Chung branch due to falling from June to Oct. in 2006. While matched on sex, age, 80 controls were found in elderly people health center. BMD was assessed by the dual-energy x-ray absorptiometry (DXA) at distal third of radial bone of non-dominant side. Results: The overall incidence of osteoporosis in the study is 56.5% and 70.3% in cases group. The relative risk of falls for osteoporosis, as compared to the normal BMD group, had adjusted odds ratio 12(95% C.I.: 1.1-125.2). The T-score of BMD significantly differed between the 80 cases and the 80 controls. People live alone or without a spouse, without real estate and without religious belief tend to fall. Conclusions: Osteoporosis can be a risk factor for falling in elderly people

MESMEG
Department of Mining and Environmental Geology
The Mushithe coal occurrence is situated approximately 16 km west of the Tshikondeni coal mine in the Tshipise-Pafuri sub-basin of the Soutpansberg coalfield in South Africa. The Soutpansberg Coalfield has received comparatively less attention compared to other more notable South African coalfields. There is as a consequence very limited information in the public domain applicable to the geology as well as quality of coal in this coalfield, as a result there is no known study focused exclusively on the Mushithe coal occurrence. The aim of the study was to conduct detailed geological mapping of the Mushithe Deposit so as to ascertain the geological environment and petrological characteristics of rocks within the area. Further work involved coal sampling and analysis in order to establish coal quality and its physical and chemical characteristics. Samples were collected using geological field mapping and channel sampling. Nine coal samples were collected from the coalbed and host rock, exposed along the Mbodi River, during geological field mapping using channel sampling. Furthermore, 92 rock samples were collected during geological field mapping of which 10 representative samples were selected for further analysis. X-ray fluorescence spectrometry was conducted on all selected samples. Proximate analysis and ultimate analyses, and calorimetry tests were undertaken on coal samples. Three samples were selected based on calorific value for maceral identification, mineral analyses and vitrinite reflectance using petrographic study. Detailed geological mapping of the area around the Mushithe coal occurrence showed the geological setting of coal in this area. The following lithologies were identified in the study area: sandstone, mudstone, ironstone, calcrete, shale, quartzite, quartz vein with a general strike direction to the north-east. The host rocks including coal were intruded by dolerite dykes and this resulted in the devolatilization of coal. The current study concluded that the Mushithe coal was formed in a wet swampy environment. This has been confirmed based on tissue preservation index (1.69) and gelification index (2.35). Coal rank ranged from bituminous Rank C- B according to United Nations Economic Commission for Europe Coal Classification (UNECE) and samples were characterised by high ash (27.90%), high moisture (10.47%) and low sulphur (0.24%). Furthermore, coal was graded below grade D based on classification for use by ESKOM which consider any calorific value below 24.5 MJ/kg to be in this category. The coal is vitrinite rich (77.75 vol%) and low in Inertinite (22.25 vol%) and devoid of Liptinite and pseudovitrinite, thus it is of good coking quality. Geochemical analysis revealed that the coal was enriched in TiO2 and Fe2O3 which was corroborated by the mineral matter which was mostly clay and pyrite. Comparatively, coal quality analysis revealed the calorific value of 14.26 MJ/kg and vitrinite reflectance between 0.94 %ROV to 1 %ROV which was less than that of the Tshikondeni Deposit but greater than that at Waterberg coalfield. The study recommends further detailed exploration of coal in the area, applying such techniques such as geophysical exploration and borehole drilling leading to resource evaluation. Further studies are recommended to provide a better interpretation of the depositional environment of coal at Mushithe as well as the effect of devolatilaziton by a dolerite dyke.
NRF