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1.
A simulated experimental reduction of U^v1 and the synthesis of uraninite by a sulfate-reducing bacteria,Desulfovibrio desulfuricans DSM 642, are first reported. The simulated physicochemical experimental conditions were:35℃, pH=7.0-7.4, corresponding to the environments of formation of the sandstone-hosted interlayer oxidation-zone type uranium deposits in Xinjiang, NW China. Uraninite was formed on the surface of the host bacteria after a one-week‘s incubation. Therefore, sulfate-reducing bacteria, which existed extensively in Jurassic sandstone-producing environments,might have participated in the biomineralization of this uranium deposit. There is an important difference in the orderdisorder of the crystalline structure between the uraninite produced by Desulfovibrio desulfuricans and naturally occurring uraninite. Long time and slow precipitation and growth of uraninite in the geological environment might have resulted in larger uraninite crystals, with uraninite nanocrystals arranged in order, whereas the experimentally produced uraninite is composed of unordered uraninite nanocrystals which, in contrast, result from the short time span of formation and rapid precipitation and growth of uraninite. The discovery has important implications for understanding genetic significance in mineralogy, and also indicates that in-situ bioremediation of U-contaminated environments and use of biotechnology in the treatment of radioactive liquid waste is being contemplated. 相似文献
2.
《Gondwana Research》2014,25(1):159-169
The Ediacaran–Early Ordovician interval is of great interest to paleogeographer's due to the vast evolutionary changes that occurred during this interval as well as other global changes in the marine, atmospheric and terrestrial systems. It is; however, precisely this time period where there are often wildly contradictory paleomagnetic results from similar-age rocks. These contradictions are often explained with a variety of innovative (and non-uniformitarian) scenarios such as intertial interchange true polar wander, true polar wander and/or non-dipolar magnetic fields. While these novel explanations may be the cause of the seemingly contradictory data, it is important to examine the paleomagnetic database for other potential issues.This review takes a careful and critical look at the paleomagnetic database from Baltica. Based on some new data and a re-evaluation of older data, the relationships between Baltica and Laurentia are examined for ~ 600–500 Ma interval. The new data from the Hedmark Group (Norway) confirms suspicions about possible remagnetization of the Fen Complex pole. For other Baltica results, data from sedimentary units were evaluated for the effects of inclination shallowing. In this review, a small correction was applied to sedimentary paleomagnetic data from Baltica. The filtered dataset does not demand extreme rates of latitudinal drift or apparent polar wander, but it does require complex gyrations of Baltica over the pole. In particular, average rates of APW range from 1.5° to 2.0°/Myr. This range of APW rates is consistent with ‘normal’ plate motion although the total path length (and its oscillatory nature) may indicate a component of true polar wander. In the TPW scenario, the motion of Baltica results in a back and forth path over the south pole between 600 and 550 Ma and again between 550 and 500 Ma. The rapid motion of Baltica over the pole is consistent with the extant database, but other explanations are possible given the relative paucity of high-quality paleomagnetic data during the Ediacaran–Cambrian interval from Baltica and other continental blocks.A sequence of three paleogeographic maps for Laurentia and Baltica is presented. Given the caveats involved in these reconstructions (polarity ambiguity, longitudinal uncertainty and errors), the data are consistent with geological models that posit the opening of the Iapetus Ocean around 600 Ma and subsequent evolution of the Baltica–Laurentia margin in the Late Ediacaran to Early Ordovician, but the complexity of the motion implied by the APWP remains enigmatic. 相似文献
3.
Erika M.Trejos Luis F.O.Silva James C.Hower Eriko M.M.Flores Carlos Mario González Jorge E.Pachón Beatriz H.Aristizábal 《地学前缘(英文版)》2021,12(2):746-755
The influence of emissions of an active volcano on the composition of nanoparticles and ultrafine road dust was identified in an urban area of the Andes.Although many cities are close to active volcanoes,few studies have evaluated their influence in road dust composition.Air quality in urban areas is significantly affected by nonexhaust emissions(e.g.road dust,brake wear,tire wear),however,natural sources such as volcanoes also impact the chemical composition of the particles.In this study,elements from volcanic emissions such as Si>Al>Fe>Ca>K>Mg,and Si-Al with K were identified as complex hydrates.Similarly,As,Hg,Cd,Pb,As,H,Cd,Pb,V,and salammoniac were observed in nanoparticles and ultrafine material.Mineral composition was detected in the order of quartz>mullite>calcite>kaolinite>illite>goethite>magnetite>zircon>monazite,in addition to salammoniac,a tracer of volcanic sources.The foregoing analysis reflects the importance of carrying out more studies relating the influence of volcanic emissions in road dust in order to protect human health.The road dust load(RD10)ranged between 0.8 and 26.8 mg m?2in the city. 相似文献
4.
Joni Tuomas Vainikka 《GeoJournal》2016,81(1):5-22
Scale is a debatable term in the humanities and social sciences. Conceptualized in human geography as spatial categories of thought, as the arenas where social processes occur, as bounded political-economic frames or as unhelpful binaries privileging either the local or the global, scale intersects a significant body of geographical research. The unfolding and intermeshing of topological connections that help to share moments and experiences are important sources for the differentiation, renewal and recalibration of individual identities, but they often work as co-components to scalar identifications. Engaging with the recent discussion on scale and the upsurge of emotional geographies, I seek to understand how people contextualize space through situated scalar perspectives and how they realign and recognize their identities through embodied emotions. The analysis of the empirical material, that comprises 23 focus groups with locally and universally-orientated civic organizations in Finland and England, focuses on the ways people use landscapes and communities as emotional signposts in their scalar identification. I argue that scale is a situated category, whose spectrum individuals negotiate through the performance of social discourses and cultural practices. In such negotiation, people scale their identity narratives to overcome or emphasize the distinctions between ‘us’ and ‘others’. 相似文献
5.
Is the westerly rotation of the lithosphere an ephemeral accidental recent phenomenon or is it a stable process of Earth's geodynamics? The reason why the tidal drag has been questioned as the mechanism determining the lithospheric shift relative to the underlying mantle is the apparent too high viscosity of the asthenosphere. However, plate boundaries asymmetries are a robust indication of the ‘westerly’ decoupling of the entire Earth's outer lithospheric shell and new studies support lower viscosities in the low-velocity layer (LVZ) atop the asthenosphere. Since the solid Earth tide oscillation is longer in one side relative to the other due to the contemporaneous Moon's revolution, we demonstrate that a non-linear rheological behavior is expected in the lithosphere mantle interplay. This may provide a sort of ratchet favoring lowering of the LVZ viscosity under shear, allowing decoupling in the LVZ and triggering the westerly motion of the lithosphere relative to the mantle. 相似文献
6.
《中国地球化学学报》2006,(Z1)
Yellowstone National Park contains numerous thermal and non-thermal acid waters with pH=1.23–5.0. These acid-sulfate waters are produced from the microbial oxidation of elemental sulfur which is formed from abiotic oxidation of hydrogen sulfide. Metal co… 相似文献
7.
P. Goovaerts 《Mathematical Geosciences》2009,41(3):243-264
The analysis of health data and putative covariates, such as environmental, socio-economic, behavioral or demographic factors,
is a promising application for geostatistics. However, it presents several methodological challenges that arise from the fact
that data is typically aggregated over irregular spatial supports and consists of a numerator and a denominator (e.g., population
size). This paper presents an overview of recent developments in the field of health geostatistics, with an emphasis on three
main steps in the analysis of areal health data: (1) estimation of the underlying disease risk, (2) detection of areas with
significantly higher risk, and (3) analysis of relationships with putative risk factors. The analysis is illustrated by using
age-adjusted cervix cancer mortality rates recorded from 1970 to 1994 of 118 counties in four Western USA states. Poisson
kriging allows the filtering of noisy mortality rates computed from small population sizes, enhancing the correlation with
two putative explanatory variables: percentage of habitants living below the federally defined poverty line, and percentage
of Hispanic females. Area-to-point kriging formulation creates continuous maps of mortality risk, reducing the visual bias
associated with the interpretation of choropleth maps. Stochastic simulation is used to generate realizations of cancer mortality
maps, which allows one to quantify how uncertainty of the spatial distribution of health outcomes translates into uncertainty
of the location of clusters of high values or the correlation with covariates. Finally, geographically-weighted regression
highlights the non-stationarity in the explanatory power of covariates; the higher mortality values along the coast are better
explained by the two covariates than the lower risk recorded in Utah. 相似文献
8.
Different hypotheses have been proposed to account for the geologic evolution of the southwestern margin of Gondwana in the Early Paleozoic, involving accretion and displacement of different terranes in a protracted convergent margin. In order to constrain and understand the kinematic and paleogeographic evolution of the Pampia terrane a paleomagnetic study was carried out in different Cambrian to Devonian units of the Eastern Cordillera (Cordillera Oriental) and the Interandean Zone (Interandino) of NW Argentina. Paleomagnetic poles from the Campanario Formation (Middle to Upper Cambrian): 1.5°N 1.9°E A95 = 9.2° K = 37.46 N = 8; and Santa Rosita Formation (Lower Ordovician): 8.6°N 355.3°E A95 = 10.1° K = 26.78 n = 9, representative of the Pampia terrane, are interpreted to indicate a Late Cambrian significant displacement with respect to the Río de la Plata and other Gondwana cratons. A model, compatible with several geological evidences that explains this displacement in the framework of the final stages of Gondwana assembly is presented. We propose a simple dextral strike-slip kinematic model in which Pampia and Antofalla (? Arequipa?) blocks moved during Late Cambrian times from a position at the present southern border of the Kalahari craton into its final position next to the Rio de la Plata craton by the Early Ordovician. 相似文献
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11.
For the last sixty years, two institutions have shaped the destiny of the town of O?wi?cim in southern Poland. One of these institutions is globally recognised, its history and development widely researched; the other is well known only amongst Polish industrialists, perhaps Polish economic geographers, and amongst the people of O?wi?cim. These two institutions are the Auschwitz State Museum and the chemical firm Dwory SA. Both institutions have their roots in the German Occupation of Poland 1939-1945. This paper presents the tale of these two institutions in order not only to highlight the need to embed memorial sites in their wider contexts, but also to indicate the impact of such sites as political-economic institutions, with the influence to shape social and economic landscapes. In laying out the geographies of the town and its two major institutions, we draw attention to the ways in which Holocaust memorialisation and post-socialist transformation are articulated with each other, not only here in O?wi?cim, and also with wider processes of social, economic, political and cultural change. 相似文献
12.
A Study of the Rhenium-Osmium Geochronometry of Molybdenites 总被引：2，自引：0，他引：2
Du Andao He Hongliao Yin Ningwan Zou Xiaoqiu Sun Yali Sun Dezhong Chen Shaozhen Qu Wenjun Institute of Rock Mineral Analysis Chinese Academy of Geological Sciences Beijing Fei Zhenbi 《《地质学报》英文版》1995,69(2)
This study deals with the first application of the isotope dilution - inductively coupled plasma mass spectrometry in the rhenium-osmium geochronometry in China. The chemical separation procedure included decomposition of samples by means of alkali fusion, extraction of rhenium by acetone and extraction of osmium by distillation. The recovery of both elements in the entire process was more than 90% . The blanks of analyses were 0.07 ng for rhenium and 0.01 ng for 187Os. The mineralization ages of molybdenites from four molybdenum deposits in China were determined by using this method, with a precision (2σ)of about ±3% . These results agree satisfactorily with their geological backgrounds. The Re-Os method can directly determine ages of metal deposits and reflect the true ages more reliably than other dating methods that only determine the ages of country rocks from which mineralization ages are inferred. As many hydrothermal sulphide deposits usually contain molybdenites, this method has bright prospe 相似文献
13.
Please refer to the attachment(s) for more details. 相似文献
14.
Felix Kaminsky 《Earth》2012,110(1-4):127-147
Starting from the late 1980s, several groups of lower-mantle mineral inclusions in diamond have been found. Three associations were established among them: juvenile ultramafic, analogous to eclogitic, and carbonatitic. The juvenile ultramafic association strongly predominates, and it is composed of ferropericlase, MgSi-, CaSi- and CaTi-perovskites, stishovite, tetragonal almandine-pyrope phase (TAPP), and some others. The association analogous to the upper-mantle eclogitic association, formed from subducting lithosphere, comprises: majorite, CaSi-perovskite bearing compositional Eu anomalies, phase ‘Egg’ with a tetragonal structure, and stishovite. The carbonatitic association is represented by various carbonates, halides, and associated minerals. Some mineral associations (wüstite + periclase and native iron + iron carbides) are, possibly, related to the D″ layer at the core/mantle boundary. The mineralogical composition of the lower mantle is now understood to be more complex than had been suggested in theoretic and experimental works. The proportion of ferropericlase in the lower mantle is higher than it was suggested before, and its composition is more iron-rich (mg = 0.36–0.90) as compared to experimental and theoretical data. Free silica (stishovite) is always present in lower-mantle associations, and a separate aluminous phase (TAPP) has been identified in several areas. These discrepancies suggest that the composition of the lower mantle differs to that of the upper-mantle, and experiments based solely on ‘pyrolitic’ compositions are not, therefore, applicable to the lower mantle. These data indicate a probability of an alternative to the CI-chondrite model of the Earth's formation, for example, an enstatite-chondrite model. 相似文献
15.
Please?refer?to?the?attachment(s)?for?more?details. 相似文献
16.
Advances in research of Asian geology—A summary of 1:5M International Geological Map of Asia project
The International Geological Map of Asia at a 1:5,000,000 scale (IGMA5000) is the first digital Asian geological map under the standard of the Commission for the Geological Map of the World (CGMW). Major advances that have been achieved in compiling the map are manifested in the following understandings.
- (1)Large amounts of Mesozoic volcanic rocks occurring in the eastern Asian coastal area are mainly Cretaceous instead of Upper Jurassic–Lower Cretaceous. Most of the Carboniferous–Permian volcanic rocks in Central Asia seem not to be arc volcanics, but the product of an extensional stage. The basal boundary of the Meso-Neoproterozoic Jixian section in China is not dated at 1.8 Ga as defined previously, but less than 1.68 Ga.
- (2)The most significant Neoarchean tectono-thermal events in the Sino-Korean craton and the Indian craton took place at 2.5 Ga rather than at 2.7 Ga. The basement of the Yangtze craton was finally formed at 0.75–0.8 Ga, which is 0.2–0.3 Ga later than the Greenville orogenic cycle. Geologically, South China is identified to be an Early Paleozoic Caledonian foldbelt. The Qinling belt, where no oceanic basin was developed in Triassic times, is not an Indosinian collisional orogen, but a continental crust subduction one. When Pangea was formed, Indo-Australian Gondwana had been joined to Paleo-Asia and between them there was no oceanic basin, i.e. no Paleo-Tethys which continued from Paleozoic to Mesozoic. A huge Indosinian orogenic belt existed on the southern margin of Paleo-Asia to the north of the Zagros–Himalayas.
- (3)Asia is a composite continent consisting of three major cratons—the Siberian, Indian and Arabian and three huge orogenic belts with a number of minor cratons and numerous microcontinents included. The main body of the Asian continent took its shape during the Mesozoic. The orogenic belts belong respectively to three global tectonic domains: the Paleo-Asian, Tethyan and Pacific. The small cratons, such as Sino-Korea, Yangtze, Tarim, and Sibumasu are thought to be affiliated to the tectonic transform zone between Gondwana and Siberia. They had been situated on the northern margin of Gondwana before the disappearance of the Paleo-Asian Ocean, and were lying on the southern margin of Paleo-Asia after the closing of the Paleo-Asian Ocean and then the opening of the Tethys. The fact that ophiolites in Asia appear to get progressively younger in age from north to south throws light on the Phanerozoic evolutionary process of the dispersion of Gondwana and the accretion of Asia accompanied by a southward migration of its orogenic belts.
17.
Dr. Wolfgang Werner 《International Journal of Earth Sciences》1990,79(2):279-290
By compiling data available from progressive geoscientific research and by complementary studies it seems possible for an increasing number of mineral districts to find indications of the regional structural control of hydrothermal ore deposits. The relationship between hydrothermal mineralization, faulting or fault reactivation and related processes can, of course, best be examined at the less deformed sedimentary record of ancient epicontinental sedimentary basins. There is increasing evidence that the sediment-hosted submarine-hydrothermal Zn-Pb-Ba mineralizations such as Meggen, Rammelsberg, Howards Pass and McArthur River are spatially and genetically related to deep synsedimentarily active fault systems of intracontinental basins or stretched passive continental margins. For long periods of basin development the faults provided favorable conduits for episodically released basin-dewatering brines, which precipitated the leached metals into third-order basins situated next to these faults. There are many similarities to epigenetic mineralizations, which formed either pre-, syn- or postorogenetically from brines leaching the (meta)sediments and associated magmatites and migrating along fault zones to their near-surface trap structures.
Zusammenfassung Für viele Erzprovinzen bietet sich durch Kompilation der in den letzten Jahrzehnten rasch angewachsenen Zahl geowissenschaftlicher Daten und durch gezielte ergänzende Untersuchungen die Möglichkeit, Anhaltspunkte oder Belege für die regionale Strukturbindung von hydrothermalen Vererzungen zu finden. Naturgemäß lassen sich die Zusammenhänge zwischen hydrothermaler Mineralisation, Störungstektonik und begleitenden Prozessen am besten an nur gering orogen überprägten ehemaligen Sedimentbecken untersuchen. So gibt es vermehrt Belege dafür, daß die sediment-gebundenen, submarin-hydrothermalen Zn-Pb-Ba Vererzungen wie Meggen, Rammeisberg, Howards Pass, McArthur River etc. räumlich und genetisch an tiefreichende Störungssysteme gebunden sind, die während der Sedimentation in intrakontinentalen Riftbecken oder auf ausgedünnten passiven Kontinentalrändern aktiv waren. Diese Störungssysteme bündelten die salinaren Beckenentwässerungsströme und ermöglichten über lange Zeiträume ihren episodischen Aufstieg zum Meeresboden, wo die aus den Sedimenten aufgenommenen Metalle als Sulfide in Spezialbecken abgesetzt wurden. Es bestehen prinzipielle Ähnlichkeiten mit vielen epigenetischen prä-, syn- oder postorogenen Mineralisationen; auch hier migrierten die salinaren Lösungen, die ihren Metallgehalt aus den (Meta)Sedimenten und eingelagerten Magmatiten bezogen, entlang von Störungssystemen bis zu den oberflächennahen Fallenstrukturen.
Résumé La compilation des données géologiques qui se sont largement multipliées au cours des dernières décennies, complétée par des rechercùhes complémentaires particulières, nous offre pour beaucoup de régions la possibilité de trouver des indices ou même des preuves d'un contrôle structural des minéralisations hydrothermales. Il va de soi que les relations entre la minéralisation hydrothermale, la formation et la réactivation des failles ainsi que les processus associés sont les plus faciles à étudier dans les couches sédimentaires les moins touchées par une orogenèse postérieure. Ainsi, il existe des preuves que les gisements stratiformes et sédimentaires de Zn-Pb-Ba du type Howards Pass, McArthur River et Meggen sont liés à des systèmes de failles synsédimentaires profondes, en relation avec des bassins intracontinentaux du genre rift et avec des marges continentales passives en extension. Ces systèmes de failles synsédimentaires ont drainé des eaux salines intersticielles et ont rendu possible leur mouvement ascendant vers les fonds marins où leur contenu métallifère s'est déposé dans des bassins locaux. Des nombreuses recherches récentes mettent en évidence la ressemblance avec les minéralisations épigénétiques formées avant, pendant et après l'orogenèse; là aussi, les eaux interstitielles, après avoir reçu leur contenu métallifère des (meta)sédiments et des magmatites associées ont migré le long de systèmes de failles jusqu'aux pièges structuraux proches de la surface.
, , , , 280 . , , . , - , , , .: Meggen, Rammerlsberg, Howards Pass, McArthur River ., , . , , , , , . -, - - ; , // , .相似文献
18.
《中国地球化学学报》2006,(Z1)
As one of the most fertile soils in China, phaeozem has been cultivated for about three hundred years and some soil physical-chemical characters have been changed, which would affect the agricultural development. In order to evaluate the quality of phaeoz… 相似文献
19.
正In addition to an extrusive volcanic component and associated sills,the Neoproterozoic Franklin Large Igneous Province(LIP)comprises a giant radiating dyke swarm spanning an arc of ca.110?,as well as a less- 相似文献