Laboratory Test Methods For The Evaluation Of Flammability Of Polymers

Combustion is a complex phenomena involving a multiplicity of variables. Some important variables measured in flame tests follow [1]. In order to characterize ignition, such related parameters as ignition time, ease of ignition, flash ignition temperature, and self-ignition temperature are measured. For studying the propagation of the flame, parameters such as distance burned or charred, area of flame spread, time of flame spread, burning rate, charred or melted area, and fire endurance are measured. Smoke characteristics are studied by determining such parameters as specific optical density, maximum specific optical density, time of occurrence of the densities, maximum rate of density increase, visual obscuration time, and smoke obscuration index. In addition to the above variables, there are a number of specific properties of the combustible system which could be measured. These are soot formation, toxicity of combustion gases, heat of combustion, dripping phenomena during the burning of thermoplastics, afterglow, flame intensity, fuel contribution, visual characteristics, limiting oxygen concentration (OI), products of pyrolysis and combustion, and so forth. A multitude of flammability tests measuring one or more of these properties have been developed [2]. Admittedly, no one small scale test is adequate to mimic or assess the performance of a plastic in a real fire situation. The conditions are much too complicated [3, 4]. Some conceptual problems associated with flammability testing of polymers have been reviewed [5, 6].

Characterization of lignin-modifying enzymes of the selective white-rot fungus Physisporinus rivulosus

White-rot fungi are wood degrading organisms that are able to decompose all wood polymers; lignin, cellulose and hemicellulose. Especially the selective white-rot fungi that decompose preferentially wood lignin are promising for biopulping applications. In biopulping the pretreatment of wood chips with white-rot fungi enhances the subsequent pulping step and substantially reduces the refining energy consumption in mechanical pulping. Because it is not possible to carry out biopulping in industrial scale as a closed process it has been necessary to search for new selective strains of white-rot fungi which naturally occur in Finland and cause selective white-rot of Finnish wood raw-material. In a screening of 300 fungal strains a rare polypore, Physisporinus rivulosus strain T241i isolated from a forest burn research site, was found to be a selective lignin degrader and promising for the use in biopulping. Since selective lignin degradation is apparently essential for biopulping, knowledge on lignin-modifying enzymes and the regulation of their production by a biopulping fungus is needed. White-rot fungal enzymes that participate in lignin degradation are laccase, lignin peroxidase (LiP), manganese peroxidase (MnP), versatile peroxidase (VP) and hydrogen peroxide forming enzymes. In this study, P. rivulosus was observed to produce MnP, laccase and oxalic acid during growth on wood chips. In liquid cultures manganese and veratryl alcohol increased the production of acidic MnP isoforms detected also in wood chip cultures. Laccase production by P. rivulosus was low unless the cultures were supplemented with sawdust and charred wood, the components of natural growth environment of the fungus. In white-rot fungi the lignin-modifying enzymes are typically present as multiple isoforms. In this study, two MnP encoding genes, mnpA and mnpB, were cloned and characterized from P. rivulosus T241i. Analysis of the N-terminal amino acid sequences of two purified MnPs and putative amino acid sequence of the two cloned mnp genes suggested that P. rivulosus possesses at least four mnp genes. The genes mnpA and mnpB markedly differ from each other by the gene length, sequence and intron-exon structure. In addition, their expression is differentially affected by the addition of manganese and veratryl alcohol. P. rivulosus produced laccase as at least two isoforms. The results of this study revealed that the production of MnP and laccase was differentially regulated in P. rivulosus, which ensures the efficient lignin degradation under a variety of environmental conditions.

Characterization of groundwater chemistry under the influence of lithologic and anthropogenic factors along a climatic gradient in Upper Cauvery basin, South India

Hydrogeological and climatic effect on chemical behavior of groundwater along a climatic gradient is studied along a river basin. `Semi-arid' (500-800 mm of mean annual rainfall), `sub-humid' (800-1,200 mm/year) and `humid' (1,200-1,500 mm/year) are the climatic zones chosen along the granito-gneissic plains of Kabini basin in South India for the present analysis. Data on groundwater chemistry is initially checked for its quality using NICB ratio (<+/- 5 %), EC versus TZ+ (similar to 0.85 correlation), EC versus TDS and EC versus TH analysis. Groundwater in the three climatic zones is `hard' to `very hard' in terms of Ca-Mg hardness. Polluted wells are identified (> 40 % of pollution) and eliminated for the characterization. Piper's diagram with mean concentrations indicates the evolution of CaNaHCO3 (semi-arid) from CaHCO3 (humid zone) along the climatic gradient. Carbonates dominate other anions and strong acids exceeded weak acids in the region. Mule Hole SEW, an experimental watershed in sub-humid zone, is characterized initially using hydrogeochemistry and is observed to be a replica of entire sub-humid zone (with 25 wells). Extension of the studies for the entire basin (120 wells) showed a chemical gradient along the climatic gradient with sub-humid zone bridging semi-arid and humid zones. Ca/Na molar ratio varies by more than 100 times from semi-arid to humid zones. Semi-arid zone is more silicaceous than sub-humid while humid zone is more carbonaceous (Ca/Cl similar to 14). Along the climatic gradient, groundwater is undersaturated (humid), saturated (sub-humid) and slightly supersaturated (semi-arid) with calcite and dolomite. Concentration-depth profiles are in support of the geological stratification i.e., not approximate to 18 m of saprolite and similar to 25 m of fracture rock with parent gneiss beneath. All the wells are classified into four groups based on groundwater fluctuations and further into `deep' and `shallow' based on the depth to groundwater. Higher the fluctuations, larger is its impact on groundwater chemistry. Actual seasonal patterns are identified using `recharge-discharge' concept based on rainfall intensity instead of traditional monsoon-non-monsoon concept. Non-pumped wells have low Na/Cl and Ca/Cl ratios in recharge period than in discharge period (Dilution). Few other wells, which are subjected to pumping, still exhibit dilution chemistry though water level fluctuations are high due to annual recharge. Other wells which do not receive sufficient rainfall and are constantly pumped showed high concentrations in recharge period rather than in discharge period (Anti-dilution). In summary, recharge-discharge concept demarcates the pumped wells from natural deep wells thus, characterizing the basin.

Stable isotope evidence for ca. 2.7-Ga-old Archean cap carbonates from the Dharwar Supergroup, southern India

Carbon isotope compositions of carbonate rocks from similar to 2.7-Ga-old Neoarchean Vanivilas Formation of the Dharwar Supergroup presented earlier by us are re-evaluated in this study, besides oxygen isotope compositions of a few silica dolomite pairs. The purpose of such a revisit assumes significance in view of recent field evidences that suggest a glaciomarine origin for the matrix-supported conglomerate member, the Talya conglomerate, which underlies the carbonate rocks of the Vanivilas Formation. An in-depth analysis of carbon isotope data reveals preservation of their pristine character despite the rocks having been subjected to metamorphism to different degrees (from lower greenschist to lower amphibolite facies). The dolomitic member of Vanivilas Formation of Marikanive area is characterized by highly depleted delta C-13 value (up to -5 parts per thousand VPDB) and merits as the Indian example of ca. 2.7-Ga-old cap carbonate. This inference is further supported by estimated low temperature of equilibration documented by a few silica dolomite pairs from the Vanivilas Formation collected near Kalche area. These pairs show evidence for oxygen isotopic equilibrium at low temperatures (similar to 0-20 degrees C) with depleted water (delta O-18 = -21 parts per thousand to -15 parts per thousand VSMOW) of glacial origin. We propose that the mineral pairs were deposited during the deglaciation period when the ocean temperature was in its gradual restoration phase. The dolomite of Marikanive area is the first record of cap carbonates from the Indian subcontinent with Neoarchean antiquity.

Potential Application of Adsorptive Media to Enhance Phosphorus Uptake in Stormwater Basins and Wetlands at Lake Tahoe : literature review. Report to the University of California Davis Tahoe Research Group

Phosphorus removal by wetlands and basins in Lake Tahoe may be improved through designing these systems to filter storm water through media having higher phosphorus removal capabilities than local parent material. Substrates rich in iron, aluminum and calcium oftentimes have enhanced phosphorus removal. These substrates can be naturally occurring, byproducts of industrial or water treatment processes, or engineered. Phosphorus removal fundamentally occurs through chemical adsorption and/or precipitation and much of the phosphorus can be irreversibly bound. In addition to these standard media, other engineered substrates are available to enhance P removal. One such substrate is locally available in Reno and uses lanthanum coated diatomaceous earth for arsenate removal. This material, which has a high positive surface charge, can also irreversibly remove phosphorus. Physical factors also affect P removal. Specifically, specific surface area and particle shape affect filtration capacity, contact area between water and the surface area, and likelihood of clogging and blinding. A number of substrates have been shown to effectively remove P in case studies. Based upon these studies, promising substrates include WTRs, blast furnace slag, steel furnace slag, OPC, calcite, marble Utelite and other LWAs, zeolite and shale. However, other nonperformance factors such as environmental considerations, application logistics, costs, and potential for cementification narrow the list of possible media for application at Tahoe. Industrial byproducts such as slags risk possible leaching of heavy metals and this potential cannot be easily predicted. Fly ash and other fine particle substrates would be more difficult to apply because they would need to be blended, making them less desirable and more costly to apply than larger diameter media. High transportation costs rule out non-local products. Finally, amorphous calcium products will eventually cementify reducing their effectiveness in filtration systems. Based upon these considerations, bauxite, LWAs and expanded shales/clays, iron-rich sands, activated alumina, marble and dolomite, and natural and lanthanum activated diatomaceous earth are the products most likely to be tested for application at Tahoe. These materials are typically iron, calcium or aluminum based; many have a high specific surface area; and all have low transportation costs. (PDF contains 21 pages)

Estudo diagenético aplicado ao Membro Maruim da Formação Riachuelo , na parte terrestre da sub-bacia de Sergipe, Brasil

O Membro Maruim da Formação Riachuelo (Neoalbiano), na parte terrestre da Sub-bacia de Sergipe, contém fácies de água rasa compostas, principalmente, por rudstone/grainstone oncolítico oolítico, com baixo conteúdo e variedade de bioclastos. A correlação dos afloramentos e análise petrográfica detalhada, envolvendo catodoluminescência, microscopia eletrônica de varredura (MEV) e estudos isotópicos e análise química elementar, permitiram a reconstrução da história diagenética do intervalo estudado. As rochas carbonáticas do Membro Maruim estão completamente afetadas por processos diagenéticos associados aos estágios eogenético, mesogenético e telogenético. A dolomitização foi um dos principais produtos diagenéticos observados no estágio eogenético e encontra-se substituindo total ou parcialmente os calcários do Membro Maruim. A dolomitização concentra-se no topo dos ciclos deposicionais descritos na área de estudo e diminuem gradativamente para a base dos mesmos. As relações entre a porosidade e a dolomitização foram estudadas com base nas comparações da fábrica cristalina da dolomita preservada nos afloramentos estudados. Os resultados isotópicos das dolomitas indicam que o processo de dolomitização ocorreu a partir do refluxo de salmouras em um ambiente ligeiramente hipersalino (penesalino). As áreas mais próximas ao contato com a salmoura, fonte dos fluidos dolomitizantes, exibem menor desenvolvimento de porosidade, uma vez que nessas regiões ocorreriam processos de superdolomitização (Pedreira Carapeba). Nestas áreas a assinatura isotópica do carbono e do oxigênio é muito positiva (o valor do δ13C varia de 2.37 a 4.83 e o valor do δ18O oscila entre 0.61 e 3.92), indicando que os processos diagenéticos tardios não teriam alterado significativamente a assinatura isotópica original. As dolomitas geradas nas áreas afastadas da salmoura (pedreiras Massapé, Inorcal I, Inorcal II, Inhumas e Santo Antônio) exibem um maior desenvolvimento de porosidade e têm uma composição isotópica de carbono e oxigênio mais negativa (o valor do δ13C varia de -5.66 a 2.61 e o valor do δ18O oscila entre -4.25 e 0.38). A assinatura isotópica das dolomitas descritas nestas pedreiras também se encontra alterada por processos de dedolomitização. Os cimentos diagenéticos precipitados durante o estágio mesogenético foram os principais responsáveis pela obliteração da porosidade primária e secundária dos calcários do Membro Maruim. Adicionalmente, estes cimentos diagenéticos tardios calcitizaram as dolomitas, fechando parcialmente a porosidade secundária das mesmas. A porosidade das rochas carbonáticas também se encontra fortemente reduzida pela compactação mecânica e química. A dissolução foi o único processo que levou à geração de porosidade secundária no estágio telogenético, porém em porcentagens muito baixas. As fácies dolomíticas são as que apresentam maior desenvolvimento de porosidade secundária, como consequência dos processos de dissolução no ambiente telogenético. A dissolução compreende um dos últimos eventos diagenéticos identificados no intervalo estudado.

Utilização de imagem do sensor Aster para discriminação espectral de rochas carbonáticas aflorantes na região Noroeste do Estado do Rio de Janeiro

Este trabalho teve como objetivo geral avaliar o potencial das imagens do sensor ASTER, utilizando a região do infravermelho de ondas curtas (SWIR), para discriminação espectral de rochas carbonáticas aflorantes na região Noroeste do Estado do Rio de Janeiro, complementando produtos existentes de mapeamento geológico. As rochas carbonáticas servem de matéria-prima para produção de cimento, que atualmente apresenta forte demanda dado o crescimento de obras civis devido à expansão da infraestrutura do Estado do Rio de Janeiro. Este crescimento no consumo oferece desafios às companhias produtoras, tornando-se de vital importância a identificação de novas áreas para exploração de insumos para a indústria civil. Neste sentido, o carbonato tem sofrido grande pressão com relação a sua produção pois é a principal matéria-prima utilizada na fabricação do cimento. Imagens do sensor Aster vem sendo utilizadas na área da geologia com êxito, discriminando litologias e minerais como quartzo, óxido de ferro e calcita. Na região do intervalo de ondas entre 2,235-2,285 μm e 2,295-2,365 μm , as bandas 7 e 8 do sensor ASTER na região do SWIR, mostram-se adequadas para a identificação de minerais de calcita e dolomita. Como metodologia, foram aplicadas as técnicas de razões de bandas para separação de calcários e dolomitos e para a classificação espectral, foi utilizada a técnica SAM. Tornou-se como referência para a classificação espectral amostras de áreas de rochas carbonáticas aflorantes e espectros da biblioteca espectral da USGS. As classificações espectrais obtiveram resultados significativos na discriminação espectral das áreas carbonáticas, no entanto as técnicas de razões de bandas não obtiveram resultados suficientes para a discriminação de calcários e dolomitos. Para trabalhos futuros sugere-se a realização de trabalho de campo para a coleta de espectros, através da espectrorradiometria dos afloramentos dos carbonatos.

Nova metodologia para caracterização litológica das rochas carbonáticas do pré-sal com base na perfilagem e espectroscopia de poço

O cenário mundial de crescimento está favorecendo uma demanda cada vez maior por petróleo e gás. Para se adequar a esta demanda crescente, as companhias petroleiras têm perfurado em regiões de águas profundas e com caráter geológico particular, como os depósitos carbonáticos recém explorados no Brasil pela Petrobras e que entraram em produção a partir de 2008. Para a produção de hidrocarbonetos é preciso um conhecimento profundo das rochas que os contém. Isto se deve ao fato que os sensores usados para detectar hidrocarbonetos no processo conhecido como perfilagem de poço na indústria petroleira são influenciados em suas medições pelas características das rochas. No caso deste trabalho, carbonatos do pré-sal, aparece uma complicação adicional em termos litológicos que é a presença do mineral Estevensita que não é comumente encontrado em ambientes carbonáticos. Em função de não haver uma forma de detectar sem ambiguidades o mineral Estevensita (rico em magnésio) com a Dolomita (também rica em magnésio), e levando-se em consideração o fato de que a Estevensita fecha os poros da rocha (rocha não reservatório) enquanto a Dolomita normalmente pode ser uma excelente rocha reservatório é de fundamental importância conhecer se o magnésio é proveniente da Estevensita ou do processo de dolomitização do carbonato (substituição de cálcio por magnésio). Não existe hoje em dia uma metodologia de perfilagem de poço que possa indicar a proveniência do magnésio. Estevensita ou Dolomita? Rocha reservatório ou não-reservatório? O objetivo deste trabalho é prover respostas às perguntas acima. Desenvolver uma forma de analisar os minerais presentes no pré-sal através da perfilagem e espectroscopia de poço e fazer a separação entre os diversos constituintes das rochas encontradas no pré-sal. O pré-sal brasileiro é constituído por litologia carbonática complexa, sendo a seção rifte formada por coquinas e a seção sag por microbialitos. Estas rochas foram depositadas antes da deposição da camada de sal no fim do Aptiano. Para atingir o resultado esperado neste trabalho serão utilizadas medições convencionais e não convencionais no laboratório com rochas análogas ao pré-sal e minerais puros tais como a Estevensita a fim de determinar respostas padrão para serem utilizados em programas de análise de registros de perfilagem. O produto final deste trabalho é desenvolver um procedimento para determinação de litologia no pré-sal brasileiro através de registros a cabo (wireline) ou enquanto se perfura (Logging While Drilling - LWD)

Bio-syngas production from biomass catalytic gasification

A promising application for biomass is liquid fuel synthesis, such as methanol or dimethyl ether (DME). Previous studies have studied syngas production from biomass-derived char, oil and gas. This study intends to explore the technology of syngas production from direct biomass gasification, which may be more economically viable. The ratio of H-2/CO is an important factor that affects the performance of this process. In this study, the characteristics of biomass gasification gas, such as H-2/CO and tar yield, as well as its potential for liquid fuel synthesis is explored. A fluidized bed gasifier and a downstream fixed bed are employed as the reactors. Two kinds of catalysts: dolomite and nickel based catalyst are applied, and they are used in the fluidized bed and fixed bed, respectively. The gasifying agent used is an air-steam mixture. The main variables studied are temperature and weight hourly space velocity in the fixed bed reactor. Over the ranges of operating conditions examined, the maximum H-2 content reaches 52.47 vol%, while the ratio of H-2/CO varies between 1.87 and 4.45. The results indicate that an appropriate temperature (750 degrees C for the current study) and more catalyst are favorable for getting a higher H-2/CO ratio. Using a simple first order kinetic model for the overall tar removal reaction, the apparent activation energies and pre-exponential factors are obtained for nickel based catalysts. The results indicate that biomass gasification gas has great potential for liquid fuel synthesis after further processing.

悬索桥隧道式锚碇与围岩系统的破坏模式研究

The anchorages are unparalleled structures only in a suspension bridge, and as main bearing facilities, play an important role in connecting the superstructures and the ground. The tunnel anchorage, as one alternative type of the anchorages, has more advantages over its counterpart, the gravity anchorage. With the tunnel anchorages adopted, not only can surface excavation be reduced to protect the environment, and natural condition of the rock be utilized and potential bearing capacity of surrounding rock be mobilized to save engineering cost, but also the technological predominance of auxiliary engineering measures, such as prestressed concrete, anchoring piles, rock anchors and collar beam between the two separated anchorages, can be easily cooperated to work together harmoniously under the circumstances of poor rock quality. There are plentiful high mountains and deep canyons in west part of China, and long-span bridge construction is inevitably encountered in order to realize leapfrogging development of the transportation infrastructure. Western mountainous areas usually possess the conditions for constructing tunnel anchorages, and therefore, the tunnel anchorages, which are conformed to the conception of resource conservative and sustainable society, extremely have application and popularization value in western underdeveloped region. The scientific and technological problem about the design, construction and operation of tunnel anchorages should be further investigated. Combining the engineering of western tunnel anchorages for the Balinghe Suspension Bridge, this paper probed into the survey method and in-situ test method for tunnel anchorages, scientific rock quality evaluation of surrounding rock to provide reasonable physical and mechanical parameters for design, construction and operation of tunnel anchorages, bearing capacity estimation for tunnel anchorage, deformation prediction of the anchorage-rockmass system, tunnel-anchorage slope stability analysis and the evaluation of excavation stability and degree of safety of the anchorage tunnel. The following outcomes were obtained: 1. Materials of tunnel anchorages of suspension bridge built (and in progress) at home and abroad were systematically sorted out, with the engineering geological condition and geomechanical property of surrounding rock around the anchorage tunnel, the design size of anchorages and the construction method of anchorage tunnel paid more emphasis on, to unveil the internal relationship between the engineering geological conditions of surrounding rock and the design size and axis angle of anchorages and provide references for future design, construction and study of tunnel anchorages. 2. Physical and mechanical parameters were recommended based on three domestic and foreign methods of rock quality evaluation. 3. In-situ tests, adopting the back-thrust method, of two kinds of reduced scale model, 1/30 and 1/20, for the tunnel anchorages were conducted in the declining exploration drift with rock mass at the test depth being the same as surrounding rock around real anchorages, and reliable field rockmass displacement data were acquired. Attenuation relation between the increment of distance from the anchorage and the decrement of rockmass displacement under maximum test load, and influential scope suffered by anchorage load were obtained. 4. Using similarity theory, the magnitude of real anchorage and rockmass displacement under design load and degree of safety of the anchorage system were deduced. Furthermore, inversion analysis to deformation modulus of slightly weathered dolomite rock, the surrounding rock of anchorage tunnel, was performed by the means of numerical simulation. 5. The influential law of the geometrical size to the limit bearing capacity of tunnel anchorage was studied. 6. Based on engineering geological survey data, accounting for the combination of strata layer and adverse discontinuities, the failure patterns of tunnel anchorage slope were divided into three modes: sliding of splay saddle pier slope, superficial-layer slippage, and deep-layer slippage. Using virtual work principle and taking anchorage load in account, the stability of the three kinds of failure patterns were analyzed in detail. 7. The step-by-step excavation of anchorage tunnel, the numerical overload and the staged decrement of rock strength parameters were numerically simulated to evaluate the excavation stability of surrounding rock around anchorage tunnel, the overload performance of tunnel anchorage, and the safety margin of strength parameters of the surrounding rock.

油气、微生物与砂岩型铀矿形成关系研究——以东胜铀矿床和钱家店铀矿床为例

Sandstone-type uranium deposits are frequently found close to oil fields or uraniferous sandstones contain bitumen or petroleum. However, few evidence has been presented to indicate the association of uranium mineralization with petroleum oxidation. Thus, Dongsheng uranium deposit in Ordos Basin and Qianjiadian deposit in Kailu Basin are taken for examples to solve the puzzle. Integration data from sedimentary petrology, mineralogy, race elements geochemistry, isotope geochemistry and organic geochemistry, the uranium and petroleum sources, and diagenetic paragenesis of the host sandstone are analyzed, and then the genetic relationship between microbes, petroleum and uranium deposits are discussed. The observation under microscope shows that the host sandstone samples from Middle Jurassic Zhiluo Formation in the Dongsheng deposit contained different kinds of metamorphic rock fragments, which should have been derived form outcrops north to this basin. The LREE/HREE ratios of gneiss and amphibolite sampled from outcrops were close to the highest and the lowest LREE/HREE ratios of the sandstones with well-compared chondrite-normalized REE patterns, respectively. So these results consistently indicated that parent rocks of sandstones were mainly contributed from these two kinds of metamorphic rocks. There was very high Th/U ratio for granite gneiss, which was a mainly potential U resource. Hydrocarbon inclusions and adsorbed hydrocarbons are observed under fluorescence microscope in the host sandstone of Dongsheng uranium deposit, suggesting that the sandstones may have been utilized as oil migration pathways. Based on biomarker parameters, it is indicated that the inclusion oils and adsorbed hydrocarbons were marginally mature to mature, and were derived from humic-sapropel type organic matter under poor reducing freshwater to semi-saline environment. The features are similar to those of organic matter extracted from Triassic sandstone and source rock, but are different from that of cretaceous sandstone. Thus, it can be concluded that the inclusion oils and adsorbed hydrocarbons were mainly derived from Triassic lacustrine facies source rock. Observation results under Scanning Electron Microscopy and Electron Microprobe with Energy Spectrum Analysis show that, in Dongsheng area, the main uranium ore mineral is coffinite. The coffinite is intimately intergrown or coexists with pyrite and calcite, thus, the solution during mineralization stage is inferred to be alkaline. The alkaline environment is not favored for uranium to be pre-concentrated by absorption, and then be reduced abiogenetically. δ34S of pyrite and δ13C of calcite indicate that pyrite was formed by bacterial sulfate reduction (BSR) and part of the carbon of calcite has been dirived from oxidation of petroleum, respectively. Additionally, petroleum is found biodegraded. All the lines of evidence consistently indicate that petroleum was involved in uranium mineralization. Coffinite with microbe-like structures is found in the high U sandstone samples and is composed of nanoparticles, indicating the coffinite is biogenic. The conclusion are also supportted by laboratory experiment studies, which have shown that SRB are capable of utilizing U(VI) as the preferred electron acceptor for respiration and reduce U(VI) to U(IV) directly, coupled the oxidaton of organic matter and sulfate reduction. Based on the research results mentioned above, in the Dongsheng area, coffinite is likely to have formed by mixing of brine containing petroleum derived from Triassic with uranium-bearing meteoric water from outcrops north to Ordos Basin. SRB utilize hydrocarbon as carbon source, and directly reduce U(VI) resulting in precipitation of coffinite. The product of metabolism, H2S and CO2, was precipitated as pyrite and calcite during mineralization stage. Petroleum in fluid inclusions and adsorbed type in host sandstone from Lower Cretaceous Yaojia Formation in Qianjiadian uranium deposit, Kailu Basin, are derived from Jurassic Jiufotang Formation in this basin and the uranium mineral consists mainly of pitchblende. The δ34S and δ13C values of pyrite and calcite during mineralization stage indicate SRB have likely degraded petroleum, which is similar to that of Dongsheng deposit. The alkaline environment as indicated by the diagenetic mineral assemblage calcite, Fe dolomite, pyrite and pitchblende deposit suggests that U ore in the Qiangjiajiadian has a similar origin, i.e., direct reduction by SRB. However, less part of pitchblende is intergrown with kaolinite, suggesting the solution during mineralization stage is acidic. The environment is favorable for U(VI) to be adsorded on quartz or other mineral, and then reduced by H2S produced by SRB. Thus, it can be concluded that U(VI) reduction with petroleum oxidation by SRB and other microbes is an important ore-forming mechanism in petroleum-related sandstone-type uranium deposits. The finding is significant in that it provides a theoretical basis for exploration of both uranium and petroleumr.

内蒙古白云鄂博地区元古宙构造-岩浆演化史与超大型REE-Nb-Fe矿床成因

Bayan Obo giant REE-Nb-Fe deposit in the northen margin of the North China Craton (NCC) is well known in the world for its abundant rare earth element resources. There is nearly one hundred year of studying history in substance component, chronology and geochemistry of the ore deposit, since the main ore body was found in 1927. However, there still exist remarkable divergences in genesis, mineralized age and material origin. Especially the REE enrichment mechanism leaves us a secret. Recent research shows that the Bayan Obo ore deposit likely resulted from the carbonatite magma activity, which is a favorable factor for REE accumulation. Based on the analysis of tectonic evolution history of north margin of NCC this thesis mainly discussed the formation background of cratonic margined rifts in Bayan Obo, and presented the analytical results of formation environment, intrusion age and deep origin of Proterozoic carbonatite magma. These research results can provide evidence for ore genesis. LA ICP-MS U-Pb dating on zircon shows that the Neoarchean basement was mainly composed of calc-alkaline TTG gneisses (2588±16Ma). The collision orogeny movement of the northen margin of the NCC between 2.0 Ga to 1.9 Ga brought the swarm of diorite-granodiotite magma (2023±16Ma) and intense regional metamorphism event (1906.3±7.7 Ma to 1892.7±6.7 Ma). In the sequent super continent break up background, intense metamorphic and deformed basement complex was uplifted to the surface suffered denudation, forming Mesoproterozoic Bayan Obo group in the contemporary continental margin rifts. The uplift of basement complex and formation of continental rifts were likely related with mantle plume activity. Evidence from petrological and geochemical data suggests that abundant alkaline-basic magma resulted from enhancement of continental breakup activity, that separated into carbonatite veins and mafic dykes by melt immiscibility mechanism, intruded in Bayan Obo margin rifts at the late stage of extension movement. Carbonatite veins can be divided into three main types by mineral composition: dolomite carbonatite, dolomite-calcite coexistent carbonatite and calcite carbonatite. Intrusion relationship between different types of carbonatite veins show that the calcite carbonatite veins were formed latter than the dolomite type as well as the coexistent type. Moreover, geochemical data also reveals successive and evolutive character between them. The content of REE increases together with the calcite minerals component. That is to say that REE gradually accumulated as the evolution of carbonatite magma. High precision Sm-Nd isochron data shows that the intrusion age of carbonatite veins was at 1319±48Ma. Moreover, the REE mineralization age in calcite carbonatite veins was around 1275±87Ma that is consistent with the intrusion age in error range. According to these data the abundant REE already existed in the carbonatite magma before intrusion and result in the earlier ore mineralization. The average age of mineralized dolomite was at 1353±100Ma, and the mineralization age of apatite in coarse grain dolomite was around 1329±150Ma. These data is consistent with carbonatite. Considering the coincident rare, trace element and isochron composition between them, it is presumed that mineralized dolomite was also the carbonatite intrusion and was the mainly factor for huge REE enrichment.

内蒙古白云鄂博超大型REE-Nb-Fe矿床脉状矿化时代与成矿流体特征

Bayan Obo REE-Nb-Fe ore deposit is the largest REE deposit in the world. Owing to its unique type and tremendous economic value, this deposit has widely attracted interests from geological researchers and vast amount of scientific data have been accumulated. However, its genesis, especially ore-forming age and REE sources, have been under dispute for a long time. On the basis of previous research works, this paper mainly conducts studies on the Early Paleozoic ore-forming event in the Bayan Obo deposit. The following results and conclusions can be suggested: Sm-Nd isotopic analytical results of bastnaesite, beloeilite, albite and fluorite samples from a coarse-crystalline ore lode present an isochron age of 436±35Ma. Besides, Rb-Sr isotope dating of the coarse-crystalline biotite lode that intruded into banded ores gives an isochron age of 459±39Ma. The two ages verify the exist of Early Paleozoic ore-forming event at Bayan Obo, which characterized by extensive netted mineralization of REE fluorocarbonates, aeschynite and monazite, accompanied by widely fluorite-riebeckite-aegirine-apatite alteration. Sr-Nd isotope composition of vein minerals is located between EMI and ancient lower crust component in the ISr(t)-εNd(t) correlation diagram, indicating that there is a crustal contamination during veined mineralization. A large area late Paleozoic granitoids are distributed in the southeast region of east open pit of the mine. The granitoids intruded directly into the ore-bearing dolomite, and produced intense skarnization. Moreover, at 650-660m of the drill core on 22 line and 1598m level flat in the south of East Open Pit, we firstly found skarnization rocks. Single grain and low background Rb-Sr isochrone dating on phlogopite in skarn gives 309±12Ma. Considering the intruded contacting relationship, the late Paleozoic granitoids, already extended to the under part of REE ore bodies, must be posterior to the latest intense REE mineralization, and is only a destructive tectonic and magmatic activity. Fluid inclusion types of fluorite in the Bayan Obo deposit consist of multiphase daughter mineral-bearing inclusion, two or three phase CO2-bearing inclusion and two phase aqueous inclusion. Petrography, laser Raman analysis and microthermometry study indicate that the fluids involving in REE-Nb-Fe mineralization at Bayan Obo might be mainly of H2O-CO2-NaCl-(F-REE) system. The presence of REE-carbonate as a daughter mineral in fluid inclusions shows that the original ore-forming fluids are rich in REE elements.

塔里木盆地塔北、塔中地区早古生代白云岩形成机理

In Tarim Basin, extensive carbonates of Lower Paleozoic occur, in which thick Cambrian and Lower Ordovician dolostones are widespread and show a potential perspective in hydrocarbon exploration. So they are viewed as an important target for exploration. Tarim Basin is a poly phase composite basin, which underwent multiphase tectonic modification and volcanic activities; these exerted significant influences on the basin-fills and basin fluid evolution, thereby the diagenetic history, particularly on the deep-buried Lower Paleozoic dolostones. Referring to the classification of dolomite texture proposed by Gregg & Sibley (1984) and Sibley & Gregg (1987). In view of crystal size, crystal shape, crystal surface and contact relation, eight genetic textures of dolomite crystals are identified, based on careful petrographic examinatoins. These textures include: 1) micritic dolomite; 2) relict mimetic dolomite; 3)finely crystalline, planar-e(s), floating dolomite; 4)finely crystalline, planar-e(s) dolomite; 5) finely-coarse crystalline, nonplanar-a dolomite; 6)coarse crystalline, nonplanar saddle dolomite; 7) finely-medium crystalline, planar-e(s) dolomite cement; 8) coarse crystalline, nonplanar saddle dolomite cement, in which the former six textures occurs as in matrix, the latter two in the cements. Detailed geochemistry analysis is carried out on the basis of genetic textures of dolomite and related minerals such as quartz and calcite. The result showed that the calcite has the highest average content in Sr, which can be sorted into two groups; micritic dolomite has the highest average content in Sr among all kinds of dolomites; the REE patterns of all kinds of dolomites is similar to those of marine limestone samples. Saddle dolomite cement has δ13C values from -2.44‰ to 1.27‰ PDB, and δ18O values from -13.01‰ to -5.12‰ PDB, which partially overlap with those of matrix dolomite (δ13C values from -2.83‰ to 2.01‰ PDB, δ18O values from -10.63‰ to -0.85‰ PDB). Saddle dolomite cement has 87Sr/86Sr ratios from 0.7086 to 0.7104, which totally overlap with those of matrix dolomite (0.7084 ~ 0.7116). Compared with saddle dolomite derived from other basins all over the world, the saddle dolomites of Tarim Basin have similar δ13C, δ18O and 87Sr/86Sr ratios values with those of matrix dolomite. This scenario reflects the unusual geological setting and special dolomitizing liquid of Tarim Basin. The values of δ18O, δ13C and 87Sr/86Sr ratios of calcite also can be sorted out two groups, which may been resulted from the one stage of extensive uplift of Tarim Basin from Mesozoic to Cenozoic. Fluid inclusion microthermometry data of the diagenetic mineral indicates that matrix dolomite has relatively low homogenization temperatures (Th) of 80～105oC and salinities of 12.3％ (wt% NaCl equivalent); saddle dolomite has highest Th values, which concentrate in 120～160oC and salinities of 13.5～23.7％ (wt% NaCl equivalent); quartz has relatively low Th of 135～155oC and salinities of 17.8～22.5％ (wt% NaCl equivalent); calcite has relatively low Th of 121～159.5oC and salinities of 1.4～17.5％ (wt% NaCl equivalent). These data suggest that the saddle dolomites could have formed in thermal brine fluids. Based on comprehensive petrographical study, detailed geochemistry and fluid inclusion microthermometry analysis on Lower Paleozoic dolomite of Tarim Basin, three types of dolomitisation mechanism are proposed: Penecontemporaneous dolomitisation (Sabkha dolomitisation & Reflux dolomitisation); Burial dolomitisation (shallow-intermediate burial dolomitisation & Deep burial dolomitisation ); Hydrothermal cannibalized dolomitisation. In view of host-specified occurrences of hydrothermal dolomite, the low abundance of saddle dolomite and high geochemical similarities between saddle dolomite and host dolomite, as well as highest Th and high salinities , the hydrothermal dolomite in Tarim Basin is thus unique, which could have been precipitated in modified fluid in the host dolomite through intraformational thermal fluid cannibalization of Mg ions from the host. This scenario is different from the cases that large scale dolomitizing fluid migration took place along the fluid pathways where abundant saddle dolomite precipitated. Detailed observations on 180 petrographic and 60 casting thin sections show original pores in Lower Paleozoic dolomite were almost died out by complicated diagenetic process after a long time geologic evolution. On the other hand, deep-buried dolomite reservoirs is formed by tectonic and hydrothermal reforming on initial dolomites. Therefore, the distribution of structure-controlled hydrothermal dolomite reservoirs is predicted in Tabei and Tazhong Area of Tarim Basin based on the geophysical data.

鄂尔多斯盆地东部地区奥陶系马家沟组沉积相与储层特征研究

Ordos Basin is one of the primary bases for petroleum exploration in our country. A series of Ordovician large gas fields were discovered, which suggest that the Lower Paleozoic carbonate, especiallly for Ordovician carbonate rocks, preserve plenty of hydrocarbon resources. Well Longtong 1 is studied as the typical exploration well. Acorrding to the specific research on the type of lithology, texture, structure and sedimentary sequence in Ordovician Majiagou Formation as well as additional data from another 20 wells, the sedimentary model has been built in Majiagou Formation. The sedimentary characteristics for each Member in Majiagou Formaiton and the feature of distribution are well understood as below: It suggests that period of Member 1, Member 3 and Member 5 in Majiagou Formation characterize with dry and hot climate as well as drop of the sea level. The area of Well Longtan 1 in the eastern basin is abundant of platform evaporite lithofacies with the depositional anhyrock and salt rock, whereas yield a suite of dolomite intercalated by the thin layers of anhyrock from the anhyrcok-dolomite platform sediment. It deposits muddy dolomite, dolomitic limestone and fine-grain dolomite in limestone-dolomite platform and restricted sea. During the stage of Member 2 and Member 4 in Majiagou Formation, the climate is wet and hot with increasing sea level. The study region occurs limestone with little dolomite in the open sea environment; but the margin area is the restricted sea settings with interbeding dolomite and limestone. Based on the thin section identification, element and isotope analysis as well as the study of texture and structure, it sugguests that the main reserviors are dolomite while the gypsum are major cap rocks. The Member 2 in Majiagou Formation is both the source rocks and the resveroirs; gypsum rocks widely occur in Member 3 as the better cap; similar to the Member 2, the Member 4 in Majiagou Formation is both the source rocks and the resveroirs; there are two source-reservoir-cap assemblages in the Member 5 alone and the cap is gypsum with high quality and great thickness, which is a favorite source-reservoir-cap assemblage.