Formações ferríferas neoproterozóicas são mundialmente conhecidas e trata-se de um tipo peculiar de depósito não só pelos aspectos econômicos, mas por estarem, geralmente, relacionadas a depósitos de origem glacial. A presente dissertação aborda as ocorrências de formações ferríferas associadas à diamictitos glaciogênicos da Formação Puga na região de Bodoquena, estado do Mato Grosso do Sul. Foram realizados processamentos de dados aeromagnetométricos, mapeamento geológico, caracterização petrográfica e geoquímica, além da avaliação dos recursos. Os dados aeromagnéticos foram eficientes para o delineamento da área de abrangência da formação ferrífera. A mesma constitui-se de camadas de óxidos de ferro disseminados, alternados com sílica. Blocos isolados ocorrem associados a formação ferrífera mas a ação tectônica dificulta a observação das relações entre os clastos e o bandamento original. As evidências geológicas observadas mostram que a deposição da Formação Puga teve contribuição de um componente glacial, provavelmente relacionada ao evento Varangeriano/Marinoano. A Formação Puga deve ter se depositado num ambiente hidrotermal distal misto com a precipitação de fluidos ferrríferos hidrotermais em sedimentos detríticos glaciais. A avaliação regional dos recursos de Bodoquena, através do uso de métodos convencionais, mostra que a região tem um potencial em torno de um bilhão de toneladas de recursos de ferro. Ensaios de caracterização tecnológica resultaram em uma recuperação final de aproximadamente 65% em massa, com um teor médio de 55% de Fe. Isto implica em produtos que atendem as especificações de mercado. / Neoproterozoic iron formations are worldwide known and they are a very peculiar kind of deposit not only by economic aspects but also they are usually related to glacial deposits. This dissertation focus on iron formation associated with glaciogenic diamictites interpreted as belonging to the Puga Formation, in Bodoquena, state of Mato Grosso do Sul. To this deposit magnetic survey, geological mapping, geochemical and petrographical characterization, as well as iron resource evaluation have been done. Moreover, aeromagnetic data were effective to delineate the total iron formation coverage. Its mostly composed of fine disseminated iron oxide layers alternated with silica. Isolated blocks occur within the iron formation but tectonic overprinting makes it difficult to have a clear observation of the relationship between clasts and original lamination. The geological evidences observed show that the Puga Formation had a glacial contribution during its deposition, and probably is related to the Varanger/Mar inoan event. It may have deposited in a distal hydrothermal environment with the ferruginous fluid precipitation together with glacial sediments. The regional evaluation of Bodoquena resources through conventional methods shows that this region has geological resource potential for more than one billion tons of iron ore. Technological characterization tests results in 65% mass recovery w ith 55% Fe. This implies in products that attend to merchantable specifications.

Formações ferríferas neoproterozóicas são mundialmente conhecidas e trata-se de um tipo peculiar de depósito não só pelos aspectos econômicos, mas por estarem, geralmente, relacionadas a depósitos de origem glacial. A presente dissertação aborda as ocorrências de formações ferríferas associadas à diamictitos glaciogênicos da Formação Puga na região de Bodoquena, estado do Mato Grosso do Sul. Foram realizados processamentos de dados aeromagnetométricos, mapeamento geológico, caracterização petrográfica e geoquímica, além da avaliação dos recursos. Os dados aeromagnéticos foram eficientes para o delineamento da área de abrangência da formação ferrífera. A mesma constitui-se de camadas de óxidos de ferro disseminados, alternados com sílica. Blocos isolados ocorrem associados a formação ferrífera mas a ação tectônica dificulta a observação das relações entre os clastos e o bandamento original. As evidências geológicas observadas mostram que a deposição da Formação Puga teve contribuição de um componente glacial, provavelmente relacionada ao evento Varangeriano/Marinoano. A Formação Puga deve ter se depositado num ambiente hidrotermal distal misto com a precipitação de fluidos ferrríferos hidrotermais em sedimentos detríticos glaciais. A avaliação regional dos recursos de Bodoquena, através do uso de métodos convencionais, mostra que a região tem um potencial em torno de um bilhão de toneladas de recursos de ferro. Ensaios de caracterização tecnológica resultaram em uma recuperação final de aproximadamente 65% em massa, com um teor médio de 55% de Fe. Isto implica em produtos que atendem as especificações de mercado. / Neoproterozoic iron formations are worldwide known and they are a very peculiar kind of deposit not only by economic aspects but also they are usually related to glacial deposits. This dissertation focus on iron formation associated with glaciogenic diamictites interpreted as belonging to the Puga Formation, in Bodoquena, state of Mato Grosso do Sul. To this deposit magnetic survey, geological mapping, geochemical and petrographical characterization, as well as iron resource evaluation have been done. Moreover, aeromagnetic data were effective to delineate the total iron formation coverage. Its mostly composed of fine disseminated iron oxide layers alternated with silica. Isolated blocks occur within the iron formation but tectonic overprinting makes it difficult to have a clear observation of the relationship between clasts and original lamination. The geological evidences observed show that the Puga Formation had a glacial contribution during its deposition, and probably is related to the Varanger/Mar inoan event. It may have deposited in a distal hydrothermal environment with the ferruginous fluid precipitation together with glacial sediments. The regional evaluation of Bodoquena resources through conventional methods shows that this region has geological resource potential for more than one billion tons of iron ore. Technological characterization tests results in 65% mass recovery w ith 55% Fe. This implies in products that attend to merchantable specifications.

abstract: Banded iron formations (BIFs) are among the earliest possible indicators for oxidation of the Archean biosphere. However, the origin of BIFs remains debated. Proposed formation mechanisms include oxidation of Fe(II) by O2 (Cloud, 1973), photoferrotrophy (Konhauser et al., 2002), and abiotic UV photooxidation (Braterman et al., 1983; Konhauser et al., 2007). Resolving this debate could help determine whether BIFs are really indicators of O2, biological activity, or neither. To examine the viability of abiotic UV photooxidation of Fe, laboratory experiments were conducted in which Fe-bearing solutions were irradiated with different regions of the ultraviolet (UV) spectrum and Fe oxidation and precipitation were measured. The goal was to revisit previous experiments that obtained conflicting results, and extend these experiments by using a realistic bicarbonate buffered solution and a xenon (Xe) lamp to better match the solar spectrum and light intensity. In experiments reexamining previous work, Fe photooxidation and precipitation was observed. Using a series of wavelength cut-off filters, the reaction was determined not to be caused by light > 345 nm. Experiments using a bicarbonate buffered solution, simulating natural waters, and using unbuffered solutions, as in prior work showed the same wavelength sensitivity. In an experiment with a Xe lamp and realistic concentrations of Archean [Fe(II)], Fe precipitation was observed in hours, demonstrating the ability for photooxidation to occur significantly in a simulated natural setting. These results lead to modeled Fe photooxidation rates of 25 mg Fe cm-2 yr-1—near the low end of published BIF deposition rates, which range from 9 mg Fe cm-2 yr-1 to as high as 254 mg Fe cm-2 yr-1 (Konhauser et al., 2002; Trendall and Blockley, 1970). Because the rates are on the edge and the model has unquantified, favorable assumptions, these results suggest that photooxidation could contribute to, but might not be completely responsible for, large rapidly deposited BIFs such those in the Hamersley Basin. Further work is needed to improve the model and test photooxidation with other solution components. Though possibly unable to fully explain BIFs, UV light has significant oxidizing power, so the importance of photooxidation in the Archean as an environmental process and its impact on paleoredox proxies need to be determined. / Dissertation/Thesis / Masters Thesis Biochemistry 2017

The Pilbara region of Western Australia hosts the Hamersley Province, an area of abundant iron ore resources located in the lower Hamersley Groups, Brockman and Marra Mamba Iron Formations. This study consists of a geotechnical and a geochemical and mineralogical investigation into the Banded Iron Formation (BIF) and shale deposits of the lower Hamersley Group that reside in the pit walls of RTIO mines in Western Australia. Areas throughout Tom Price, Paraburdoo, Marandoo and West Angelas iron ore mines are geotechnically investigated for rock mass conditions through the use of the Slope Mass Rating (SMR) classification system and through point load and slake durability testing. Selected samples from these areas were then geochemically and mineralogically tested by X-ray Fluorescence (XRF), X-ray Diffraction (XRD) and microscopic analysis, to determine the geochemical and mineralogical changes of BIF and shale as they alter and weather through hypogene and supergene alteration and Recent weathering. It was found that the most efficient method for determining the alteration and/or weathering of lower Hamersley Group BIF and shale deposits was by the use of a chemical alteration index, calculated from enriched and depleted major elements in the BIF and shale as they alter and weather. It has been suggested here that this Pilbara Iron alteration index can be calculated efficiently and effectively from geochemical testing in intervals down boreholes throughout future or developing open pit mines to assist in estimating slope stability conditions. It is also suggested that many boreholes should be analysed in section or in 3D space to create cross sections or block models showing the varying extent of alteration and weathering throughout the area being studied. From the geotechnical investigation, it was found that the weakest region, in terms of pit slope stability, were the highly and extremely altered and/or weathered regions with Pilbara Iron alteration indices of between 61 and 80, and 81 and 100, respectively. If these zones are identified, slope stability analysis can be focused on these geotechnically vulnerable areas. Slope stability analysis should be completed by using a suitable technique, such as by the use of SMR, which, along with other risk identification measures, will identify potentially unstable areas and suggest the required course of action. Further hazard and risk analysis should be undertaken in potentially unstable areas and remedial measures undertaken as appropriate. Thereby, the Pilbara Iron alteration index can be used in the Hamersley Province as a predictive tool for pit slope stability.

Memoria para optar al título de Geólogo / En la región de Pilbara, Australia, hay una gran cantidad de depósitos de hierro. En la zona destaca un depósito coluvial, cuyo material está siendo estudiado para ser utilizado en obras civiles. El objetivo de este estudio es caracterizar mineralógica y geotécnicamente el material. Para caracterizar el material se hizo una clasificación granulométrica, se describió geológicamente el material y se analizó los datos de un triaxial gigante realizados por IDIEM que aún no han sido publicados. A modo de entender los procesos internos de lo que ocurre en el triaxial, se hizo dos ensayos especiales: un corte directo entre dos rocas y un corte directo entre roca y suelo. La caracterización del material granular grueso se basó en descripciones macroscópicas de partículas, descripciones microscópicas de cortes transparentes y pulidos y determinación de propiedades físicas (densidad, absorción y porosidad). La resistencia de las partículas se estimó mediante ensayos de carga puntual y martillo de Schmidt. Adicionalmente, el material grueso se sometió a un ensayo de desgaste (slake). La mineralogía del material fino se caracterizó a través de un análisis de difracción de rayos x y espectrometría por infrarrojo (FTIR). Las principales conclusiones de este estudio son: el material se clasificó como gravas bien graduadas, GW, el ángulo de fricción del material es 30,15°, el ángulo de fricción entre roca-roca varía entre 11,2° y 15,4°, y el ángulo de fricción entre roca-suelo varía entre 15,2° y 19,3° dependiendo de la humedad. La mineralogía del material granular grueso está compuesta en mayor parte por hematita, magnetita y cuarzo. La resistencia a la compresión simple de las partículas es 101,24 Mpa. La mineralogía del material fino está compuesta por magnetita, hematita, cuarzo, goethita, muscovita, caolín y rutilo. El material grueso resultó resistente al desgaste.

Original estimates of phosphorus (P) concentrations in the Precambrian oceans before 1.9 Ga gave a budget of ~10-25% of modern day levels. This budget was challenged by accounting for high silica (Si) concentrations that were believed to have outcompeted P for binding sites on precipitating iron oxide-hydroxide particles during the chemical oxidation and burial of iron (Fe). Such iron oxide-hydroxide particles are considered as proxies of ancient iron-rich sedimentary rocks, such as banded iron formations, which are often used to infer the dissolved chemistry of trace elements in the ancient oceans. This study raises the question of wether arsenic (As) had an effect of the binding of P to precipitating iron minerals, during the co-precipitation of Iron oxide- hydroxide in elevated Fe and Si concentrations characteristic of the early oceans. This hypothesis is based on the chemical similarities seen between P and As. Results show a more pH dependent competition between P and AsIII, whereby P outcompetes AsIII at a pH <7. The effect decreases as the pH rises until pH ~8 at which the effect cancels out and AsIII becomes somewhat predominant over P. AsV on the other hand, an analogue to P, is outcompeted by P throughout pH 5-10. Distribution coefficients (Kd) of P on iron oxide-hydroxide particles were not affected by the concentration of Si in solution. Average Kd and standard error between concentrations of Si, across the sample pH of 5-10 revealed an average Kd of 0.072 (±0.01) μM-1. This is strikingly similar to another experimental Kd at 0.075 (±0.003) μM-1, when the effects of Si are excluded. The average Kd in this study is also consistent with the average Kd of 0.06 μM-1 from a range of As-rich hydrothermal systems reported in a previous study, supporting the original idea of Precambrian P levels being low. The average Kd between concentrations of Fe revealed a Kd of 0.12 (±0.03) μM-1 although this was not statistically significant from the average Kd between groups of Si. In addition to low levels of P, the Precambrian oceans likely also contained high levels of As, due to the high hydrothermal activity. This scavenging of P from oceanic waters would have become increasingly important as surface oceans became more oxygenated and the presence of AsV would have been greater. Because the availability of Si does not show any great effect on the uptake of P by precipitating iron oxide-hydroxides, Si concentration is likely not a proxy for oceanic P concentrations. It is proposed that low dissolved P levels are consistent with early oceans that w!ere a lot more hydrothermally influenced than the oceans of today. / Prekambriska fosfor (P) nivåer var ursprungligen estimerade till ca 10-25% utav koncentrationen funnen i dagens havsvatten. Denna budget blev motsagd i och med att kisel (Si) sades kunna ersätta bundet fosfor på järn oxid-hydroxid partiklar som precipiterade genom kemisk oxidation och sedimentering av järn (Fe). Dessa järn oxid-hydroxid partiklar anses användbara som proxy för formationen av uråldriga järn-rika sedimentära bergarter såsom banded iron formation (BIF), vilka används idag för att bestämma mängden spårämnen i de uråldriga haven. Denna studie ställer frågan huruvida arsenik (As) påverkar mängden P som binder till precipiterande järn mineral under procession av co-precipitering av järn oxid-hydroxid i lösning med förhöjda koncentrationer av Fe och Si, karakteristiska för the uråldriga haven. Denna hypotes är baserad på de kemiska likheter som finns mellan P och As. Resultaten påvisar en pH beroende konkurrens mellan P och AsIII där P utkonkurrerar AsIII vid låg pH. Effekten av denna konkurrans minskar med ökande pH tills effekten blir omvänd omkring pH 8 och P blir istället till viss del utkonkurrerad av AsIII. AsV å andra sedan, en verklig kemisk analog till P, är kontinuerligt utkonkurrerad av P genom alla utförda pH, pH 5-10. Distribueringskoefficienter (Kd) för P på järn oxid-hydroxid partiklar visade ingen påverkan av mängden Si tillgängligt. Medelvärdet av Kd och standard error mellan data av alls pH, grupperat av Si, gav ett värde av 0.072 (±0.01) μM-1. Detta är påfallande nära ett experimentellt framtaget Kd värde av 0.075 (±0.03) μM-1 då effekten av Si är borttagen. Medelvärdet i denna studie är också sammanfallande med det Kd medelvärde man finner idag från olika hydrotemala system av 0.063 (±0.01) μM-1. Detta ger support till den originala idén att de prekambriska haven troligen hade låga halter P tillgängligt. Medelvärdet av Kd mellan koncentrationer av Fe gav ett värde av 0.12 (±0.03) μM-1, dock var detta värde ej statistiskt significant från det Kd utifrån koncentrationer av Si. Förutom de låga nivåer av P i de Prekambriska haven så var det troligen även höga halter av As på grund av utbredd hydrotermal aktivitet. Detta uppfångande av P i de tidiga haven var troligen en alltmer viktigare process då ytvatten blev syrerikare och den oxiderade formen av As, det vill säga AsV hade varit mer vanligt förekommande. Framför allt då den konkurrerande effekten av Si kan bortses när P såväl som As inte påverkas av dess närvaro till den grad man hade trott. Detta gör även att mängden Si troligen inte är en tillförlitlig proxy för att estimera P nivåer i de uråldriga haven. Därmed föreslås det att de prekambriska haven var k!arakteriserade av låga P nivåer, jämfört med idag.

Algoma-type banded iron formation is common in Neoarchean greenstone belts, and many of its distinctive features such as the banding of iron-rich and silica-rich material and deposition in volcanic terranes have been ascribed to their deposition related to volcanic-hydrothermal activity and cyclic variability in depositional pathways. The work presented in this thesis tests these assumptions and presents a model for the deposition and post-depositional processes now represented by the petrography and geochemistry of a 2.73 Ga type-locality of Algoma-type BIF in Temagami, ON. Adsorption of components onto the surface of Fe-oxyhydroxides forming in the anoxic Neoarchean water column is the most likely process capable of transferring silica, as well as trace quantities of transition metals, rare earth elements, Ge, P, U and other components to the sediment. The petrogenesis of the Temagami BIF lithologies suggests ongoing recrystallization processes and volume loss reactions leading to the formation of magnetite layers, while jasper is identified as the most pristine lithology best representative of the initially deposited Fe-oxyhydroxide-silica gel. Recrystallization and volume loss reactions are controlled by the ongoing dewatering during compaction and diagenesis, without the influence of external hydrothermal or metamorphic fluids. When corrected for the volume loss and small amounts of clastic contamination, little residual variability can be observed in the composition of jasper and magnetite layers, indicative of an originally homogenous primary precipitate instead of sorted and layered material deposited on the seafloor. This model is in stark contrast to previous interpretations of seasonal variability in biologic activity, cyclical seasonal or hydrothermal events responsible for primary layering in BIF. Instead, very little direct input of hydrothermal components is recorded in the chemistry of the Temagami BIF, and elements abundant in high-temperature hydrothermal fluids such as sulfur are instead sourced from atmospheric sources and deposited by bacterial pathways. Lack of primary chemical variability and non-hydrothermally sourced components captured in BIF argue against a genetic link to local hydrothermal venting, but rather an open ocean depositional setting. As such, the Temagami BIF does not represent a marker horizon related to local or regional hydrothermal venting and potential formation of associated massive sulfide deposits but reflects processes and the chemistry of the open Neoarchean ocean.

<p> The East South C (E.S.C.) ore zone at the Dickenson Mine, Red Lake, is a major auriferous banded sulphide orebody which cross-cuts sulphide facies banded iron formation (S.F.B.I.F.) near its eastern termination. Pyrite was obtained from sulphide-rich portions of the ore zone as well as from sulphide-poor E.S.C. mineralization not spatially associated with S.F.B.I.F., S.F.BI.F., shear zone hosted mineralization such as the 1492 and F ore zones, and from quartz-carbonate vein mineralization in the South C ore zone. Forty-three pyrite separates from the zones were analyzed by Atomic Absorption Spectrophotometry for Co and Ni, in order to determine the origin of the E.S.C. ore zone. The average Ni and Co content of these pyrites are as follows: S.F.B.I.F.,7.9 and 13.6 ppm respectively; remobilized S.F.B.I.F. 10.3 and 13.6; carbonatized S.F.B.I.F. 10.9 and 22.6; South C 14.9 and 50.6; 1492 zone 34.1 and 28.4; F-zone 11.2-27.6; sulphide-poor E.S.C. 26.2 and 48.4 and sulphide-rich E.S.C., 17.91 and 16.63.</p> <p> High and variable Co values were found to be associated with carbonate-rich samples, irrespective of the type of mineralization and low and similar Co values were found in all carbonate-poor samples irrespective of their origin. Therefore, the Co content of pyrite cannot be used as a discriminant of genetically dissimilar pyrite. The Ni content in pyrite from S.F.B.I.F. is low and constant, while in shear zone and vein mineralization it is higher and more variable. The E.S.C. ore zone has similar values to that found in the epigenetic mineralization, however, a few sulphide-rich samples are similar to those found in S.F.B.I.F., suggesting a bimodal source of sulphide for the E.S.C.. It is proposed that the hydrothermal system which produced the E.S.C., 1492, F and South C ore zones, locally incorporated sulphides from the S.F.B.I.F. to produce the sulphide-rich mineralization found at the eastern extremity of the E.S.C. ore zone.</p> / Thesis / Bachelor of Science (BSc)

The Neoproterozoic was a time of major change in Earth’s surficial history, including a major rise in atmospheric oxygen, the first appearance of complex metazoan life, and a series of worldwide glaciations. A particular interesting element of these so called “snowball Earth” glacial deposits is the presence of iron formation, a distinctive Precambrian rock type that is largely absent from the post-Paleoproterozoic record. Despite being relatively poorly studied with respect to their geochemistry and sedimentology, Neoproterozoic iron formations are used to support many models for the record of oxygen concentrations of the Earth. The classical example of Neoproterozoic iron formation is the Rapitan iron formation of northwestern Canada. This hematite-jasper iron formation is associated with glaciogenic turbidites and diamictites. Despite being the archetype, the Rapitan iron formation has not been studied in the context of recent ideas about the Neoproterozoic. In this thesis, the stratigraphy, geochemistry, and basin architecture of the Rapitan iron formation are reassessed. Using the REE+Y and the redox-sensitive elements Mo and U, it is shown that the Rapitan iron formation was deposited in a partially restricted basin from biogenically reduced iron under variable redox conditions. Elemental Re and Mo isotopes further show that although oxic and ferruginous conditions predominated during deposition of the iron formation, a transition towards a sulfidic water column locally terminated deposition. Finally, regional stratigraphy and geochemistry show that the iron formation was preferentially deposited in deep, newly formed basins that were protected from significant siliciclastic sedimentation. These basins were delimited by inferred crustal-scale faults trending roughly perpendicular to the axis of the rift basin, and allowed significant changes in thickness and sedimentological character over short distances along strike. These factors help build an overall geotectonic regime under which Neoproterozoic iron formations were deposited: young, deep rift basins that had undergone marine incursion, and were intermittently sealed by an ice shelf, allowing for the generation of an anoxic, iron-rich water column. The absence of the Eu anomaly and the heavy Mo isotopic signature indicate that the open ocean was fully oxygenated at the time of Rapitan iron formation deposition, as opposed to ferruginous as previously suggested.

During the Geological Survey of Canada’s Cumberland Peninsula Integrated Geoscience project a ~150km long NE-SW trending volcanic belt, now termed the North Touak-Cape Dyer volcanic belt, was mapped. The volcanic rocks that comprise the belt are dominantly green weathering komatiitic rocks with some black weathering tholeiitic occurrences. Given the similar stratigraphic position, textures, mineralogy, and geochemical characteristics of the volcanic rocks throughout the belt they have been termed the Totnes Road formation, after the locality from which they were first described. The komatiitic rocks possess numerous unusual characteristics for ultramafic volcanic rocks including: fragmental textures, lack of spinifex texture, young eruption age (Paleoproterozoic), eruption through ancient continental crust, and enrichment in the HFSEs including the REEs. This places them in the uncommon and poorly understood sub-type of komatiites termed Karasjok-type komatiites. Given the ultramafic nature of the rocks and their within-plate geochemical signatures, a mantle plume is the most likely source of these rocks, with the komatiites being sourced from the hot plume axis and the tholeiites from the cooler plume head. Incorporation and melting of mantle enriched by the addition of subduction zone recycled, garnet-bearing eclogitic material, beneath thick lithosphere could cause the rocks geochemical enrichment. Stratigraphically overlying the Totnes Road formation is a variety of chemical sedimentary rocks including chert, sulphide and silicate facies iron formation, and sulphide-rich boulders. Given their consistent stratigraphic position and parallel REE patterns, these rocks have been interpreted as a co-genetic suite and are grouped under the Clephane Bay formation, after a locality that exposes a spectacular section of the chemical rocks. The variety of lithologies is believed to be due to mixing of hydrothermal and detrital inputs during deposition within an anoxic basin. Regional correlations in the area are tentative due to the lack of available geochronological and geochemical data. Mafic-ultramafic volcanic occurrences to both the north and the south of the Cumberland Peninsula show remarkably similar geochemical characteristics to the Totnes Road formation. Thus it is possible that one plume was the source for numerous volcanic occurrences within in the region but more detailed study is required to prove or disprove this possibility.