Comparison and integration of spatial data using covariance matrices

A differential approach to map comparison and integration is presented utilizing the variance-covariance matrices of polynomial trend surfaces. The approach is based on the statistics presented in the trend-surface computer program, CORSURF. Examples in south-central Kansas and the Maracaibo Basin in Venezuela are presented to show how the technique could be used in basinanalysis studies.     

Near-K/T age of clastic deposits from Texas to Brazil: impact,volcanism and/or sea-level lowstand?

Near-K/T boundary clastic deposits from Texas, Mexico, Haiti, Guatemala and Brazil, often described as impact-generated tsunami deposits, are stratigraphically below well-defined K/T boundary horizons and appear not to be causally related to the K/T boundary event. Stratigraphic evidence indicates that their deposition began during the last 170–200 kyr of the Maastrichtian, coincident with a major eustatic sea-level lowstand that lowered sea level by as much as 70–100 m. Clastic deposition ended a few tens of thousands of years before the K/T boundary during a rapidly rising sea level. The presence of glass in clastic deposits in Haiti, northeastern Mexico and Yucatan suggests that the sea-level lowstand coincided with a time of major volcanism or pre-K/T boundary bolide impact.     

Examples of structural control of hydrothermal mineralization: Fault zones in epicontinental sedimentary basins — A review

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.

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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.

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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.

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Geochemistry of magnesites and dolomites at the Oberdorf/Laming (Austria) deposit and implications for their origin

The major and trace element geochemistry of magnesite and dolomite samples from alternating rock masses at the Oberdorf/Laming (Styria, Austria) mineralization has been studied. The rare earth elements (REE) are considered to be of importance for the discussion of the origin of sparry magnesite deposits. The Al and REE contents are positively correlated, indicating a clay component as the main source for REE in the magnesites and their precursor rocks. Our data support the view that the Oberdorf and probably other magnesite mineralizations in the Eastern Alps have been formed by metasomatism. Through this process calcite (which was deposited by sedimentation in a marine environment) underwent dolomitization. Subsequently, Mg-rich solutions circulating through the rock masses formed the magnesite bodies.During the formation of the dolomites and the conversion to magnesites, the REE patterns of the original carbonates remained unchanged. The magnesites exhibit patterns that are very similar to sedimentary carbonates (which contain a REE-bearing clay component). Magnesites of purely sedimentary origin, formed in a predominantly evaporitic environment, should have lower total REE contents and different patterns due to the short residence times of these elements in seawater. Analyses of talc pseduomorphs after magnesite indicate as well that the REE patterns are not significantly altered during the talcification. The Mg-rich solutions that led to the formation of the magnesites have probably been derived from serpentinites below the gneiss complexes of eastern Styria and the South Penninic units of the Tauern window.

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Zusammenfassung Die Haupt- und Spurenelementgeochemie von Magnesit- und Dolomitproben, die aus alternierenden Gesteinsstöcken in der Magnesitmine von Oberdorf/Laming (Steiermark, Österreich) stammen, wurde untersucht. Besonderes Augenmerk wurde dabei auf die Geochemie der Seltenen Erdelemente (REE) gelegt, da diese für Aussagen über die Entstehung der Magnesitlagerstätten von besonderer Bedeutung sind. Eine positive Korrelation zwischen den Al und REE-Gehalten deutet darauf hin, daß der Hauptteil der REE einer Tonkomponente entstammt. Die Daten unterstützen eine metasomatische Entstehung der Spatmagnesite der Oberdorfer Lagerstätte und anderer Ostalpiner Lagerstätten. Sedimentär angelegter Kalzit wird dabei über Dolomit mit Mg-reichen Lösungen in Magnesit umgewandelt.Während der Metasomatose bleiben die chondritnormierten REE-Verteilungen der Ausgangskarbonate relativ unverändert erhalten. Die so entstandenen Spatmagnesite weisen Verteilungsmuster auf, die jenen der sedimentären Karbonate, aus denen sie entstanden sind, entsprechen. Rein sedimentär entstandene Magnesite werden praktisch nur in evaporitischem Milieu gebildet und sollten infolge der kurzen Verweilzeit dieser Elemente im Meerwasser wesentlich niedrigere REE-Gehalte und andere Verteilungsmuster aufweisen. Analysen einer Talkpseudomorphose zeigen, daß sich die REE-Verteilungsmuster auch bei der metasomatischen Talk-bildung nicht wesentlich ändern. Die Mg-reichen Lösungen, die zur Bildung der Magnesite notwendig waren, entstammen vermutlich tiefliegenden Sepentiniten, auf die es Hinweise im Untergrund der oststeirischen Gneisskomplexe und des südpenninischen Tauernfensters gibt.

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Résumé Cette note présente les résultats d'une étude géochimique des éléments majeurs et en trace d'échantillons de magnésite et de dolomite qui se présentent en masses alternées dans la mine de magnésite de Oberdorf/Laming (Steiermark, Autriche). Une attention particulière a été apportée aux terres rares, considérées comme fournissant des arguments importants dans la discussion de l'origine des gisements. Les teneurs en Al et en terres rares montrent une corrélation positive, ce qui permet de rapporter à un composant argileux la source principale des terres rares. Les résultats obtenus plaident en faveur d'une origine métasomatique des minéralisations en magnésite d'Oberdorf et d'autres endroits des Alpes orientales. Au cours de ce processus, la calcite, d'origine sédimentaire marine, a été le siège d'une dolomitisation avec, subséquemment, formation de corps de magnésite grâce à la circulation de solutions riches en Mg.Au cours de la métasomatose, la distribution des terres rares des carbonates originels n'est pas modifiée: les magnésites montrent des répartitions très semblables à celles des carbonates sédimentaires (lesquels renferment un constituant argileux porteur des terres rares). Des magnésites d'origine purement sédimentaires, formées en milieu évoporitique, doivent présenter un contenu total en terres rares moins élevé et une distribution différente de ces éléments, eu égard à la brièveté de leur séjour dans l'eau de mer. Des analyses de pseudomorphoses de magnésite en talc montrent de même que la distribution des terres rares n'est pas modifiée de manière significative au cours de la talcification. Les solutions riches en Mg responsables de la formation de la magnésite sont probablement dérivées de serpentines situées sous les complexes gneissiques de Styrie et les unités penniques méridionales de la fenêtre des Tauern.

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Leptonic jets from young stellar objects?

Various explanations of the bipolar-flow phenomenon in star-forming regions are compared and confronted with the observed facts. It is concluded that stellar-wind interpretations are inconsistent with the constraints. The exotic property of young stellar objects may be their extreme spin which implies strong magnetic fields and vacuum discharges above thee ^± pair-formation threshold (of 10¹² eV). Pair-plasma jets are thought to be centrifugally driven by young stars during their first 10^4±1 years of rapid rotation.     

A first approach to calculate BIOCLIM variables and climate zones for Antarctica

Theoretical and Applied Climatology - For testing the hypothesis that macroclimatological factors determine the occurrence, biodiversity, and species specificity of both symbiotic partners of...     

Magnetic properties of urban soil profile and their significance for traffic pollution-Case study of the capital airport expressway in Beijing

An expressway-side soil profile 22 cm long was sampled from the grassland of the expressway linking Beijing and the Capital International Airport. Magnetic measurements, geochemical and multivariate statistic analyses were performed on the soil samples. The results reveal that the soil profile can be divided into two parts with significant difference in magnetic proxies and heavy metal concentration. The uppermost soil horizon (0–8 cm) represents the pollution-rich layer with higher concentration of ferrimagnetic phases and metallic elements. The values of xare very high with an average of 141.60 × 10⁻⁸ m³·kg⁻¹ in the layer. We explain that the anthropogenic dust input from traffic is the predominant cause for strong signals of magnetic phases and heavy metals. Below the profile depth of 8 cm, there is minor pollution in the soil with lower concentration of magnetic minerals and heavy metals compared to the natural background values. χ remains quite stable and relatively low with an average of 49.44 × 10⁻⁸ m³·kg⁻¹. S-ratio also generally decreases with depth, and it changes from 0.93 in the 0–8 cm layer to 0.87 below the depth of 8 cm. It indicates that the soil samples are overwhelmingly predominated by ferrimagnetic minerals in the upper part soil, while the contribution of imperfect antiferromagnetic components is stronger in the lower part. Rock magnetic experiments show MD magnetite as the main magnetic carrier both in the upper and lower parts. Themagnetic grain size in the upper part is, however, a bit coarser than that in the lower part. Cluster analysis shows a positive correlation between magnetic properties (χ, ARM, SIRM) and heavy metal pollutants of Pb, Zn, Cu. Fuzzy C-means cluster analysis can clearly help divide the soil profile into two different layers and distinguish their characteristics. It can be concluded that these magnetic concentration-related parameters can be used as proxies for pollution investigation in a fast, sensitive, low-cost and highly efficient approach to screening heavy metal pollution. __________ Translated from Quaternary Sciences, 2007, 27(6): 1113-1120 [译自:第四纪研究]     

Cretaceous transformation from passive to active continental margin in the Western Carpathians as indicated by the sedimentary record in the Infratatric unit

The Cretaceous orogen of the Western Carpathians comprises fragments of the destructed northern Centrocarpathian domain, which is defined as Infratatric unit and formed a continental margin facing the Penninic Ocean in Jurassic and Cretaceous times. The breakup event and opening of the Penninic Ocean occurred in the Early Jurassic (Pliensbachian), which is recorded by an abrupt deepening event from shallow-water sediments to deep-water nodular limestone in the Infratatric sediment succession. The transformation of the passive into an active continental margin by the onset of subduction of the Penninic oceanic crust occurred in Santonian times and is reflected by the beginning of flysch deposition in the Infratatric Belice domain, which took the position of a forearc basin in the convergent margin setting. The forearc basin was supplied by clastic material from the more internal part of the Infratatric unit, which experienced nappe stacking, metamorphism, and subsequent exhumation in Late Cretaceous times. In the frontal part of the forearc basin an accretionary wedge was built up, which formed an outer-arc ridge and delivered detrital material into the forearc basin in Maastrichtian time. Final collision between the European and the Adriatic plate occurred in the Eocene period and is responsible for weak metamorphism in the Infratatric unit.     

Evolution of the isotopic composition of carbon and oxygen in a calcite precipitating H2O-CO2-CaCO3 solution and the related isotopic composition of calcite in stalagmites

The isotopic composition of carbon and oxygen in a calcite precipitating CO₂-H₂O-CaCO₃ solution is preserved in the calcite precipitated. For the interpretation of isotopic proxies from stalagmites knowledge of the evolution of δ¹³C and δ¹⁸O in the solution during precipitation is required. A system of differential equations is presented from which this evolution can be derived. Both, irreversible loss of carbon and oxygen from the solution with precipitation time τ and exchange of oxygen in the carbonates with the oxygen in the water with exchange time T are considered. For carbon, where no exchange is active, a modified equation of Rayleigh-distillation is found, which takes into account that precipitation stops at c_eq, the saturation concentration of DIC with respect to calcite, and that c_eq as well as the precipitation time τ is slightly different for the heavy and the light isotope. This, however, requires introducing a new parameter γ = (A_eq/B_eq)/(A₀/B₀), which has to be determined experimentally. (A_eq/B_eq) is the isotopic ratio for the heavy (A) and the light isotope (B) at both chemical and isotopic equilibrium and (A₀/B₀) is the initial isotopic ratio of the solution. In the case of oxygen, where exchange is present, the isotopic shifts are reduced with increasing values of the precipitation time τ. For τ ? T the solution stays in isotopic equilibrium with the oxygen in the water during the entire time in which precipitation is active. The isotopic ratios in a calcite precipitating solution R(t)/R₀ = (1 + δ(t)/1000) for carbon are plotted versus those of oxygen. R₀ is the isotopic ratio at time t = 0, when precipitation starts and δ(t) the isotopic shift in the solution after time t. These show positive correlations for the first 50% of calcite, which can precipitate. Their slopes increase with increasing values of τ and they closely resemble Hendy-tests performed along growth layers of stalagmites. Our results show that stalagmites, which grow by high supply of water with drip times less than 50 s, exhibit positive correlations between δ¹³C and δ¹⁸O along a growth layer. But in spite of this the isotopic composition of oxygen in the solution at the apex is in isotopic equilibrium with the oxygen in the water, and therefore also that of calcite deposited at the apex.