Orientador: César Augusto Moreira / Banca: Ana Olivia Barufi Franco de Magalhães / Banca: Daniel Françoso de Godoy / Resumo: Este trabalho apresenta resultados gerados através de levantamentos geofísicos terrestres de eletrorresistividade e polarização induzida integrado ao reconhecimento geológico de superfície em área potencialmente mineralizada com sulfeto de cobre, localizada a noroeste do município de Caçapava do Sul, sul do Brasil, na região norte da Bacia Sedimentar do Camaquã. A ocorrência mineral é caracterizada por veios de quartzo contidos em sericita clorita quartzo xisto, com impregnações de malaquita, óxidos de ferro. A análise estrutural local revelou a existência de um sistema de fraturas com direções principais N40-50W e N70-80E. O levantamento geofísico consistiu em 6 linhas de tomografia elétrica dispostas de maneira azimutal com distância angular de 30º uma da outra em arranjo Wenner-Schlumberger, com 400 m cada dispostas segundo critérios estruturais previamente estabelecidos. Os modelos de inversão representados através de seções 2D indicaram áreas de baixa resistividade coincidentes com valores de alta cargabilidade predominantemente em profundidades abaixo dos 40 metros, interpretadas como possíveis concentração de sulfetos. A elaboração do modelo 3D possibilitou a geração de mapas multiníveis a cada 10 metros de profundidade a partir da superfície para as variáveis de eletrorresistividade e polarização induzida, que conjuntamente com modelos tridimensionais de isosuperfície para cargabilidade colaborou no mapeamento geométrico, continuidade lateral, profundidade e controle estrutural NE-SW e NW-SE para o corpo mineralizado / Abstract: This paper presents the results generated through geophysical surveys of DC Resistivity and induced polarization integrated with geological reconnaissance of surface in an area potentially mineralized with copper sulfide, located to the northwest of the Caçapava do Sul city, northern region of Camaquã sedimentary basin, southern Brazil. The mineral occurrence is characterized by quartz veins contained in sericite quartz chlorite schist, with impregnations of malachite, iron oxides. The structural analysis of the site revealed the existence of a system of fractures with main directions N40-50W and N70-80E. The geophysical survey consisted in 6 lines of electrical tomography arranged in an azimuthal way with angular distance of 30° from each other in Wenner-Schlumberger arrangement, with 400 m each arranged according to previously established structural criteria. The inversion models represented through 2D sections indicated areas of low resistivity coincident with values of high chargeability predominantly at depths below 40 meters, interpreted as possible concentration of sulfides. The development of the 3D model enabled the generation of multilevel maps every 10 meters of depth from the surface for the resistivity and chargeability variables, which together with three-dimensional models of isosurface for chargeability collaborated on geometric mapping, lateral continuity, depth and structural control NE-SW and SE to the mineralization / Mestre

A Mina de diamantes de Romaria está localizada no perímetro urbano da cidade de Romaria, na região oeste de Minas Gerais. Durante os trabalhos de mineração executados nos últimos cem anos, foi lavrada uma área de aproximadamente 1 km2 de sedimentos. O local está situado na borda NE da Bacia do Paraná, na margem direita do Rio Bagagem, entre os Ribeirões Água Suja e Marrecos. Neste local vem sendo lavrado um conglomerado polimítico da Formação Uberaba, Grupo Bauru, pertencente ao Cretáceo Superior. Ele é constituído por clastos de micaxistos, anfibolitos, filitos e veios pegmatóides do Pré-Cambriano; arenitos da Formação Botucatu e basaltos da Formação Serra Geral. Possui matriz areno-argilosa onde foram identificadas as fases caulinita, illita e quartzo por difratometria. Sua espessura na área da mina oscila em torno de 6 m. Os minerais pesados separados do conglomerado diamantífero amostrado nas Frentes de Lavra 2 (Ferraria), 6 (Mangueiras) e na Cata exploratória do Sarkis, situada fora da área minerada, são constituídos em sua maior parte por fases opacas, entre as quais se destaca a magnetita, representando 50% em volume do concentrado. Outras fases opacas incluem hematita, ilmenita e fragmentos de lateritos. Entre as fases transparentes, destacase a granada que ocorre nas cores vermelha clara, vermelha escura, roxa, violeta e laranja, além de outros minerais derivados de rochas do embasamento cristalino. Análises químicas realizadas pela microssonda eletrônica revelaram que a ilmenita contém teores de MgO (7,4 - 11,4 % em peso) e de Cr2O3 (0,0 - 2,9 % em peso) típicos de rochas kimberlíticas. Da mesma forma, as granadas correspondem a piropos ricos em Cr2O3 (0,2 - 6,7 % em peso) correspondendo aos grupos G9 (lherzolitos), G5 e G4 (piroxenitos) e G10 (harzburgitos), sendo semelhantes a granadas das principais províncias kimberlíticas conhecidas. O diamante, por sua vez, contém microestruturas típicas semelhantes a diamantes de outras localidades. Foram identificadas trígonos em faces octaédricas, bem como microestruturas de simetria senária semelhantes às observadas em diamantes do lamproíto Argyle, na Austrália. Foram descritas microestruturas quadráticas nos cristais cúbicos, e degraus resultantes da dissolução de planos de crescimento cristalino em superfícies curvas de cristais rombododecaédricos. Atualmente a mina está paralisada desde 1984 devido a uma dívida contraída pela Extratífera de Diamantes do Brasil (EXDIBRA) com o Banco Nacional de Desenvolvimento Social. Apesar do potencial mineral existente no local, qualquer tentava de lavra só poderá ser executada mediante a quitação desta dívida. / The diamond Mine of Romaria is located in the northeast border of the Paraná Sedimentary Basin, nearby the town of Romaria, in western Minas Gerais State, Brazil. The mining place is situated on the right side of the Bagagem River, comprising an area of 1 km2 between the Água Suja and Marrecos streams. At this place diamonds have been washed from a Cretaceous polimictic conglomerate of the Uberaba Formation, Bauru Group, since the end of the nineteen century. This heterogeneous diamond-bearing conglomerate contains large conglomerate blocks of several lithologies with dimensions up to 0.80 m, set in an arenous-clayish matrix where kaolinite, illite and quartz have identified among the clasts such as mica and staurolite schists, phyllites and amphibolites of the Araxá Group, quartzites of the Canastra Group, arenites of the Botucatu Formation and basalts of the Serra Geral Formation. The concentrates obtained by washing the conglomerate contains large amounts of opaques phases mainly magnetite which may reach up to 50% in volume. Other opaques are represented by hematite, ilmenite, rutile, limonite as well as rock fragments of mica schists and complex intergrowths of laterites. The mineralogical assemblages of the transparent phases include staurolite, amphibole, epidote, kyanite, monazite, tourmaline, zircon and diamond as well. Electron micro probe analyses revealed that the ilmenites contain MgO (7.4-11.4 wt%) and Cr2O3 (0.0-2.9 wt%) contents similar to their counterparts of kimberlites from worldwide localities. Moreover, garnets are chromium rich pyropes with Cr2O3 ranging from 0.2 up to 6.7 wt %. The use discriminating diagrams revealed that most of the analysed sampled plot in the fields G9 and G3-G5 corresponding to lherzolitic and pyroxenitic parageneses, respectively. The plots include some rare G10 (harzbugitic) and G0 (unclassified) samples corresponding to garnets derived from rocks of the crystalline basement. Although diamonds have not been mined in the last years a small parcel produced by local diggers (garimpeiros) was available for physical studies including color and crystalline morphology. Several microstructures have been observed in octahedral crystal such as trigons and a pseudo-hexagonal microstructure observed in diamonds from lamproites. Cubic crystals showing the combination of the cube and dodecahedral revealed microstructures of square symmetry. Concerning dodecahedral crystal hillocks produced by dissolution were observed on the rounded faces of the samples. Presently the Mine of Romaria is closed since 1984 due to an old debt contracted by late owner Extratífera de Diamantes do Brasil (EXDIBRA) with the Brazilian Federal Agency of the Banco Nacional de Desenvolvimento Social (BNDES).

Major and trace metal loading to mountains in the western US depends on dust sources, intensity of storms and their availability for transport during snowmelt and runoff. Previous work has been conducted on dust production, composition, and its affect on solar radiation and timing of snow melt. This study was conducted to 1) examine temporal and spatial variability in dust chemistry; 2) evaluate form and availability of major and trace elements in dust; and 3) identify potential dust sources affecting mountains in Utah and Nevada. Spring and summertime dust was collected across northern Utah over the course of three years (2013-2015). Additional dust samples were collected from eastern Nevada for comparison. All samples were analyzed for mineralogy. The spring dust samples were also leached with 1 M acetic acid, 0.8 M nitric acid, and aqua regia and analyzed for 87Sr/86Sr ratios and concentrations of 40+ trace and major elements. Nearly all dust samples were enriched in playa-associated elements (U, Mg, Li, Ca, Sr, As) and anthropogenic elements (Sb, Mn, Zn, Cu, Pb, Se, Cd) relative to average upper continental crust. Leachate results showed that nearly 60% Ca, Sr, and Cd mass is potentially available for transport during snowmelt and that the rare earth elements could be mobilized under lower pH conditions in the soil zone. A major dust event on 17 March 2014 that was sampled across the study area showed spatially variable trace element concentrations and 87Sr/86Sr ratios, indicating that dust deposited to mountain snowpack originated from multiple upwind desert dust source areas. The NOAA HYSPLIT model was used to calculate back trajectories for this dust event and showed potential dust sources ranged from the Sevier, West and Great Salt Lake deserts in Utah and the Snake River Plain in Idaho. In contrast, multivariate statistical analysis showed that over the course of the study samples had unique geochemical signatures within each sample area. These findings suggest that spatial variability is more important than temporal variability in terms of the chemistry of dust deposition. With increasing populations and land use change in the western US, the short and long term effects of aeolian dust deposition to mountain environments need to continual monitored and constrained.

Socorro Island (18$\sp\circ$45'N, 111$\sp\circ$00'W) is the top portion of Volcan Evermann which has recorded historic eruptions in 1848 (?), 1896 (?), 1947, 1951 and 1993. The volcano is located at the intersection of the Clarion Fracture Zone (E-W) and the Mathematician Ridge System (N-S), and has erupted voluminous (i.e. 36 km$\sp3)$ pantellerite to trachyte ash-flows, lava-flows and domes which make up for 90% of the rocks exposed on the island. The southeastern portion of Socorro Island, known as the Lomas Coloradas area, makes up for the remaining 10%, and consists mostly of pahoehoe lava-flows of subalkaline basalt, mugearite and hawaiite intercalated with horizons of ash and scoria erupted from numerous cinder cones. K/Ar ages of the peralkaline rocks and the Lomas Coloradas basalts cluster around 0.5 m.y. suggesting eruption rates one order of magnitude larger than those estimated for Pantelleria, Italy. Although the evolution of peralkaline rocks at Pantelleria has been explained by partial melting of an alkali gabbro, mineralogical and geochemical data presented in this study are more consistent with a mechanism of differentiation involving crystal fractionation and possibly volatile-transfer from a parental basalt magma. The model proposed here has no constraints in terms of the volumes of magmas involved since the submerged portion of Volcan Evermann is presumed to be made entirely of basalt. The tectonic setting of Volcan Evermann and the eruption of volatile-rich voluminous pyroclastic-flows are considered as important factors in the development of the peralkaline condition at Socorro Island and the lack of Daly gap intermediates common to other oceanic islands of peralkaline affinity / acase@tulane.edu

Cova des Pas de Vallgornera (CPV) is morphologically and scientifically, the most prominent karst feature of Mallorca Island (Spain). It consists of over 74 km of passages developed within two carbonate lithologies (reef front and back reef facies) of Upper Miocene age. Two distinct cave patterns are recognized, both tightly controlled by the type of facies; spongework mazes and collapse chambers are characteristic for the reef front unit, whereas linear, fracture-guided galleries develop in the back reef carbonates. CPV is abundantly decorated with a variety of speleothems. The overarching goal of this study is to provide evidence towards the cave's major speleogenetic pathways using diagnostic mineral assemblages and a set of micro- and macro-scale morphological features. In particular, this research investigates whether hypogene processes were/are the main driving force in CPV's speleogenesis and how mineral assemblages and cave morphologies help untangle the complex evolution of the cave. The mineralogy of speleothems (crusts, nodules, crystals, earthy masses) deposited in the vicinity of hypogene features in the reef front is characterized by the presence of aragonite, ankerite, huntite, clay minerals, and quartz. In the back reef limestone, however, the dominant mineral is dolomite, along with aragonite, celestine, huntite, clay minerals, and quartz. Calcite is by far the most ubiquitous mineral throughout the cave. A total of twenty-six minerals were identified throughout the cave; the highest diversity (20 species) is around or inside typical hypogene features occurring within the back reef limestone, whereas in the seaward part only 13 minerals occur. Detailed macroscopic and scanning electron micro-chemical analysis and imaging have permitted the investigation of textural relationships between the minerals associated with vents, rims, and corrosion cupolas above them. These studies along with morphological and stable isotope analyses (δ13C, δ18O, δ34S), confirm that not all minerals are connected with a hypogene stage in the cave evolution, and furthermore, none of them appears to be sulfuric acid by-products. Instead, the mineral assemblages documented in speleothems from CPV clearly support at least three speleogenetic pathways, namely seacoast mixing, ascending of warm groundwaters (basal recharge), and vadose (meteoric recharge). In summary, we have shown that cave minerals (in association with particular cave morphologies) in CPV hold the keys to understanding mineral-forming processes, conditions, and events, allowing establishing their relationship with various speleogenetic pathways.

Bien que la teneur en titane des roches naturelles ne dépasse généralement pas 2% en poids de TiO2, cet élément peut se rencontrer sous des formes très diverses. les minéraux titanifères sont parfois constitués par l'oxide simple TiO2 'rutile, anatase, brookite) ; parfois par des oxydes doubles, de fer et de titane, tels que l'ilménite (FeTiO3), la titanomagnétite (Fe3-xTixO4) ....

LE GISEMENT DE MUNELLA EST UN GISEMENT VOLCANOGENE TYPIQUE, DEVELOPPE SUR LES KERATOPHYRES EN CONTACT AVEC LES SPILLITES. DANS LES KERATOPHYRES SOUS-JACENTS SE DEVELOPPENT LES STOCKWERKS, PAR CONTRE, DANS LES SPILITES SITUEES SUR LE CORPS PRINCIPAL DE LA MINERALISATION VOLCANIQUE S'EST DEVELOPPEE LA MINERALISATION DISSEMINEE EN FILONNETS. LES MINERAUX METALLIQUES CONSTITUTANT LE MINERAI SONT : PYRITE, CHALCOPYRITE, SPHALERITE ET QUARTZ, LES MINERAUX PEU FREQUENTS ETANT MARCASITE, BORNITE, GALENE, TENNANTITE-TETRAEDRITE, BARYTINE. LES MINERAUX EN TRACE SONT : HEMATITE, PYRARGYRITE, BOURNONITE, GEOCRONITE, OR, CHALCOCITE. L'ARSENOPYRITE A ETE RENCONTREE UNIQUEMENT DANS UN ECHANTILLON OU ELLE CONSTITUE 40 % DES MINERAUX METALLIQUES. LA RESSEMBLANCE FRAPPANTE DE CES MINERALISATIONS AVEC LES MINERALISATIONS SOUS-MARINES ACTUELLES NOUS PERMET DE CONSIDERER CE GISEMENT COMME UN GISEMENT VOLCANIQUE TRES PEU METAMORPHISE

minerology

The combination of rising population and increasing food demand has placed tremendous pressure on the soil resource in Bangladesh, especially floodplain soils where rice may be grown year round. Although these floodplain soils contain minerals high in potassium (K) such as micas, K deficiency in rice paddy soils is increasing throughout Bangladesh. Harvesting of straw from fields exacerbates the removal of nutrients including K, and intensive cropping with unbalanced fertilizer has resulted in depletion of "readily available" K in large areas. Five representative floodplain soils in rice production were sampled by horizon to determine physical, chemical and mineralogical properties, assess soil K, investigate plant available K, and understand impacts of redox on K fixation and release. Total and nonexchangeable K were determined using concentrated hydrogen fluoride (HF) digestion and 1.0 M HNO3 digestion, respectively, along with NH4OAcextractable K. Cation exchange capacity under both oxidized and reduced conditions was determined. Assessment of adsorption and release of K as a function of redox was done in conjunction with seven different concentrations of potassium chloride (KCl) solution and three different soils. Significant amounts of K were present in all fractions of silts and clays. Potassium concentration was greatest in the coarse clay fraction. High HNO3- extractable K suggested that much of the K in soils was from mica interlayers. Acidic soils contained less K in all fractions than the less weathered, calcareous soils. The clay fractions exhibited mostly mica, vermiculite, smectite and kaolinite. The cation exchange capacity (CEC) of reduced soils was less under oxidized condition, due to collapse of the interlayer in response to increased layer charge upon structural Fe reduction. The adsorption of K was greater for calcareous soils under both oxidized and reduced conditions than for the acidic soils. Less native K was extracted under oxidized conditions than under reduced conditions. Less adsorption under reduced conditions may be due to an increase in solution Fe2+ which can compete with K+ for exchange sites on clays.

published_or_final_version / Radioisotope / Master / Master of Philosophy