Geochemistry of Karroo dolerite sills in the Calvinia district,Western Cape Province,South Africa     

Anton P. le Roex  David L. Reid 《Contributions to Mineralogy and Petrology》1978,66(4):351-360

Two Karroo dolerite sills display chemical and mineralogical variation compatible with cumulus enrichment. The Blaauwkrans sill is an olivine tholeiite and contains a central zone slightly enriched in olivine, plagioclase and clinopyroxene. The thicker Hangnest sill is a quartz tholeiite and shows evidence of crystal settling and has a lower zone enriched in cumulus orthopyroxene and plagioclase.The two sills differ quite markedly in their trace element compositions, with the Hangnest magma enriched by a factor of two in LIL elements (Rb, Ba, Nb, Zr, Y) relative to the Blaauwkrans magma. The Hangnest magma contained extremely low Ni contents (3–5 ppm), whereas the Blaauwkrans magma contained higher but more normal Ni (100–110ppm). Such contrasting trace element compositions preclude any simple genetic relationship between the two Karroo magmas but they may be related either through a common parent or are derivatives from separate parental magmas.South African Contribution No. 24 to the International Geodynamics Project  相似文献   

Characterization of sediments in an abandoned mining area; a case study of Mansfeld region,Germany   总被引：1，自引：0，他引：1  

Rainer?WennrichEmail author  Jürgen?Mattusch  Peter?Morgenstern  Klaus?Freyer  Hanns-Christian?Treutler  Hans-Joachim?St?rk  Lutz?Brüggemann  Albrecht?Paschke  Birgit?Daus  Holger?Weiss 《Environmental Geology》2004,45(6):818-833

The distribution of selected heavy metals, including some radionuclides, metalloids and non-metals was determined in stream sediments in a region influenced by abandoned copper mining and ore processing activities. A considerable amount of the ore processing waste with a very complex composition and highly elevated concentrations of zinc, sulfur, lead, copper, arsenic, and a lot of other elements in the range between 100 and 1,000 mg/kg (Sb, Mn, Ni, Cr, Cd, Hg, and Ag) was piled up on mine dumps. The dispersion of the pollutants originating from this source and their environmental impact were investigated. Both, sediments and original waste material were studied to indicate the pathways and the mobilization behavior of different pollutants. For this purpose, the process of the elution of pollutants by application of different fractionation schemes was studied. The capabilities of different analytical techniques are shown for the analysis of solid samples (X-ray fluorescence spectrometry, Gamma-spectrometry) and liquid ones (ICP-atomic emission spectrometry, ICP-mass spectrometry and different techniques of atomic absorption). Additionally, the coupling of ion chromatography and ICP-MS detection was used to study the distribution of arsenic species in the sediment cores of a lake which acts as a natural sink for the region.  相似文献   

Summer flows in experimental catchments with different forest covers, Chile   总被引：7，自引：0，他引：7  

Andrs Iroum  Anton Huber  Kurt Schulz 《Journal of Hydrology》2005,300(1-4):300-313

Runoff and peak flows in four experimental catchments with different land uses are analyzed for summer periods. The catchments have a rainy temperate climate with annual precipitations between 2000 and 2500 mm, 70% of which is concentrated in the winter period between May and August. The final harvest of the forest plantation in one of these catchments generated increases in summer runoff. Also, differences between the maximum instantaneous discharge and the flow at the beginning of the storm then almost duplicated those registered in rainfall events of similar magnitude when the catchment was fully forested. Runoff analysis in this catchment is difficult because the two post-harvesting summer periods are much wetter than the two pre-harvesting ones but a double mass analysis shows the effect of harvesting clearly. In a paired catchment study, low cover in one of the two neighbour catchments explains higher direct runoff and base flows although lower maximum instantaneous specific discharge occurred in the less vegetated but larger catchment. Low vegetation cover explains increases in summer flows, although the size, topography, rainfall conditions, road density, extent of affected area and runoff generation processes play an important role in the hydrological effects of different land uses.  相似文献   

Predicting catchment sediment yield in Mediterranean environments: the importance of sediment sources and connectivity in Italian drainage basins   总被引：2，自引：0，他引：2  

Joris de Vente  Jean Poesen  Paolo Bazzoffi  Anton Van Rompaey  Gert Verstraeten 《地球表面变化过程与地形》2006,31(8):1017-1034

Predicting sediment yield at the catchment scale is one of the main challenges in geomorphologic research. The application of both physics‐based models and regression models has until now not provided very satisfying results for prediction of sediment yield for medium to large sized catchments (c. >50 km²). The explanation for this lies in a combination of the large data requirements of most models and a lack of knowledge to describe all processes and process interactions at the catchment scale. In particular, point sources of sediment (e.g. gullies, mass movements), connectivity and sediment transport remain difficult to describe in most models. From reservoir sedimentation data of 44 Italian catchments, it appeared that there was a (non‐significant) positive relation between catchment area and sediment yield. This is in contrast to what is generally expected from the theory of decreasing sediment delivery rates with increasing catchment area. Furthermore, this positive relation suggests that processes other than upland erosion are responsible for catchment sediment yield. Here we explore the potential of the Factorial Scoring Model (FSM) and the Pacific Southwest Interagency Committee (PSIAC) model to predict sediment yield, and indicate the most important sediment sources. In these models different factors are used to characterize a drainage basin in terms of sensitivity to erosion and connectivity. In both models an index is calculated that is related to sediment yield. The FSM explained between 36 and 61 per cent of the variation in sediment yield, and the PSIAC model between 57 and 62 per cent, depending on the factors used to characterize the catchments. The FSM model performed best based on a factor to describe gullies, lithology, landslides, catchment shape and vegetation. Topography and catchment area did not explain additional variance. In particular, the addition of the landslide factor resulted in a significantly increased model performance. The FSM and PSIAC model both performed better than a spatially distributed model describing water erosion and sediment transport, which was applied to the same catchments but explained only between 20 and 51 per cent of the variation in sediment yield. Model results confirmed the hypothesis that processes other than upland erosion are probably responsible for sediment yield in the Italian catchments. A promising future development of the models is by the use of detailed spatially distributed data to determine the scores, decrease model subjectivity and provide spatially distributed output. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Tectonic style and pressure distribution at the northern margin of the Alps between Lake Constance and the River Inn     

Manfred Müller Dipl.-Geol. Dr.  Franz Nieberding Dipl.-Geol. Dr.  Anton Wanninger Dipl.-Geophys. 《International Journal of Earth Sciences》1988,77(3):787-796

Hydrocarbon exploration in the Molasse basin and the Alpine thrust belt has provided new information on the tectonic structure of the foreland margin of the overthrust belt. Two N-S cross-sections show the front of the Folded Molasse as a so-called Triangle Zone in the area north of the Hindelang 1 well (Bavaria) and the Sulzberg 1 well (Vorarlberg). The Triangle Zone was described and defined byJones (1982) for the Alberta Foothills in Canada.Oil and gas wells commonly encountered overpressured zones with pressure gradients up to 2.5 bar/10 m. The pressure profiles from the Sulzberg1, Hindelang1, Staffelsee1, Miesbach 1 and Bromberg 1 wells were analysed stratigraphically and lithologically with respect to the tectonics of the region. It can be concluded that the overpressures in the Foreland Molasse were caused by compaction, where those within the thrust belt were caused by tectonics.

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Zusammenfassung Die von der Erdöl- und Erdgasindustrie im Bereich des Alpennordrandes durchgeführten Untersuchungsarbeiten brachten neue Ergebnisse zum tektonischen Bau. So stellt sich in zwei N-S-Profilen nördlich von Hindelang (Bayern) und über die Tiefbohrung Sulzberg 1 (Vorarlberg) die Stirn der Faltenmolasse als Triangelzone dar, wie sie von Jones (1982) aus den Foothills der Rocky Mountains beschrieben wird.Tiefbohrungen auf Erdöl und Erdgas haben verbreitet überhydrostatische Porendrücke mit Gradienten bis 2,5 bar/10 m angetroffen. Es wurden Druckprofile aus den Bohrungen Sulzberg 1, Hindelang 1, Staffelsee 1, Miesbach 1 und Bromberg 1 nach stratigraphisch-lithologischen Gesichtspunkten analysiert, regionaltektonisch zugeordnet und interpretiert. Es zeigt sich, daß die Überdrücke in der Vorlandmolasse durch Kompaktion entstanden sind, während diejenigen unter den Decken tektonische Ursachen haben.

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Résumé Les travaux d'exploration entrepris par l'industrie du pétrole dans le bassin molassique et dans la bordure septentrionale des Alpes ont conduit à de nouveaux résultats en ce qui concerne les structures tectoniques de cette région. Dans deux profils nord — sud établis dans la région, respectivement au nord de Hindelang (Bavière) et au nord de Sulzberg (Vorarlberg), le front de la molasse plissée se présente comme une »zone triangulaire« du type défini parJones (1982) dans les Foothills d'Alberta au Canada.Des forages pétroliers profonds ont fréquemment recontré des pressions interstitielles hyperhydrostatiques avec des gradients pouvant atteindre 2,5 bars / 10 m.Les profils de pression relevés dans les sondages de Sulzberg 1, Hindelang 1, Staffelsee 1, Miesbach 1 et Bromberg 1 ont été analysés au point de vue stratigraphique et lithologique et placés dans le cadre tectonique de la région. Il en résulte que les surpressions dans la molasse d'avant-pays (Vorlandmolasse) sont dues à la compaction et que celles des formations recouvertes par les nappes sont d'origine tectonique.

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, - , . , Hindelang / /, Sulzberg 1 / Vorarlberg / , Jones' 1982 Foothills . 2.5 /10 . , . , , - .

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Petrogenesis of picrite and associated basalts from the southern Mid-Atlantic Ridge     

Leon A. van Heerden  Anton P. le Roex 《Contributions to Mineralogy and Petrology》1988,100(1):47-60

Basalts dredged from the south wall of a fracture zone transecting the southern Mid-Atlantic Ridge (SMAR) at 54° S are unusual in that they include a suite of highly olivine phyric basalts, sampled along with more normal sparsely plagioclase phyric basalts, and a highly plagioclase phyric basalt. Four basalt types (olivine phyric, sparsely plagioclase phyric, evolved sparsely plagioclase phyric and highly plagioclase phyric) are readily distinguished on the basis of petrography, mineralogy and bulk composition. They range from primitive to evolved, with the olivine phyric basalts having elevated MgO (up to 15.5%) and the plagioclase phyric basalt having elevated Al₂O₃ (19.3%) and CaO (13.1%) contents. Compositional variations are extremely consistant, with the olivine phyric basalts and the sparsely plagioclase phyric basalts defining coherent linear trends. On the basis of the ratios and covariation of the incompatible trace elements Zr, Nb, Y and Ba, distinct parental magmas for each basalt type are required. An investigation of Fe-Mg and Mg-Ni distribution coefficients between olivine and magma indicates that olivines from the olivine phyric basalts are on average too forsteritic and too Ni poor to have crystallized in a magma corresponding to the host bulk rock composition. This implies that these basalts are enriched in xenocrystic olivine. Olivines from the other basalt types are mostly of equilibrium composition, although there are some exceptions. Petrogenetic models for the formation of the different basalt types are quantitatively evaluated in terms of fractional crystallization/crystal accumulation processes. These indicate that (1) the olivine phyric basalts are the products of olivine and minor Cr-spinel accumulation and do not represent analogues of primary magma, or a liquid fractionation trend; (2) that the sparsely plagioclase phyric basalts were formed by polybaric fractional crystallization of olivine, plagioclase and clinopyroxene; and (3) that the evolved sparsely plagioclase phyric basalts are not readily related to one another. The single highly plagioclase phyric basalt is unrelated to the other basalt types and is cumulus enriched in plagioclase.The different basalt types are unrelated to one another and document the presence of at least four distinct magma types erupted in close proximity at this ridge/transform intersection on the southern end of the Mid-Atlantic Ridge.  相似文献   

Nationalities of Slovenia — changing ethnic structures in Central Europe     

Anton Gosar 《GeoJournal》1993,30(3):215-223

The ethnic structure of Slovenia has in recent decades changed dramatically due to the geo-political rearrangements in Central Europe and due to the socio-economic developments in former Yugoslavia. The mixed, dark-age based ethnic pattern was at first eliminated to be replaced by a similar level of multi-ethnicity of a different origin recently. Ethnic groups of mostly Slavic (Croat, Muslim, Serb) origin have in the past couple of decades migrated to urban centers of Slovenia, thus replacing there former German and Italian minority population. Problems of attitudinal, cultural, social and linguistic nature emerge and impact the poli-structured cultural landscape of the independent nation-state.  相似文献   

Earth's surface movements in the hazardous area of Jezeří Castle,Krušné hory Mountains     

Jan Kalvoda  Vít Vilímek  Antonín Zeman 《GeoJournal》1994,32(3):247-252

Abstact The results are summarized of the correlation between the detailed geomorphological analysis and the geodynamic interpretation of the twelve high-precision levelling measurements of the Earth's recent surface movements (1983–1989) in the hazardous area of Jezeí Castle in the Kruné hory Mts. Indicated are the types and régime of these movements (Tab 1, Fig 3) which are climatic, tectonic and anthropogenous in origin. Both slightly and strongly deformed zones in the near-surface part of crystalline rocks massif were formed (Fig 1). The landform patterns (Fig 2), as well as the present-day activity of geological processes are described.  相似文献   

Presolar nanodiamonds: faster, cleaner, and limits on platinum-HL     

Silke Merchel  Ulrich Ott  Siegfried Herrmann  Thomas Faestermann  Gunther Korschinek  Anton Wallner 《Geochimica et cosmochimica acta》2003,67(24):4949-4960

We have developed a procedure that allows extraction of clean nanodiamond samples from primitive meteorites for isotopic analyses of trace elements on a timescale of just a week. This procedure includes microwave digestion and optimization of existing isolation techniques for further purification. Abundances of trace elements that are difficult to dissolve using standard procedures (e.g., Ir) are lower in the diamond residues prepared using the new technique. Accelerator mass spectrometry (AMS) was explored as a means for isotopic measurements. Results obtained on diamond fractions from Allende and Murchison show the need for suitable matrix-adjusted standards to correct for fractionation effects; nevertheless they allow putting an upper limit on the abundance of ¹⁹⁸Pt-H in nanodiamonds of ∼1 × 10¹⁴ atoms/g. This limit is on the order of what can be expected from predictions of competing nucleosynthesis models and extrapolation of the apparently mass dependent abundance trend of the associated noble gases.Unfortunately, and unexpectedly, presolar silicon carbide is almost quantitatively dissolved during microwave digestion with HCl/HF/HNO₃. Re-evaluation of the standard extraction technique, however, shows that it also may lead to severe loss of fine-grained SiC, a fact not commonly appreciated. A lower limit to SiC abundance in Murchison is 20 ppm, and previous conclusions that Murchison SiC is unusually coarse-grained compared to SiC in other primitive meteorites seem not to be warranted. Graphite and silicon nitride may survive and possibly can be separated after this step as suggested by a simulation experiment using terrestrial analog material, but the detailed behavior of meteoritic graphite requires further study.  相似文献   

Comparison of 24 h and Long-term pHstat Leaching Tests for Heavy Metal Mobilization from Solid Matrices     

A. Paschke  R. Wennrich  P. Morgenstern 《洁净——土壤、空气、水》1999,27(4):223-229

The dynamic leaching behaviour of environmentally relevant heavy metals makes it difficult to fix a suitable elution time of leaching tests. With ten different solid materials which were characterized by wavelength-dispersive X-ray fluorescence analysis and by the determination of aqua regia soluble amounts of heavy metals we performed 24 h and long-term leaching tests using the pH_stat procedure at pH 4 to be able to compare the resulting acid neutralization capacities (ANC) and heavy metal mobilization. This comparison demonstrates firstly the limitations in predicting the extent of heavy metal release after a longer (geological) time period only from the leached amounts after 24 hours and the ratio of the ANC values measured in the 24 h test and in a long-term experiment, respectively. Secondly, the effect of elution time on the leachability is not uniform but element specific and matrix dependent. Hence, the pH_stat leaching test performed in the usual manner does not seem to be suitable particularly for assessing long-term mobilization of heavy metals under acidic conditions. Additional experiments under variation of shaking frequency and time clearly demonstrate the dominant influence of the first parameter on the resulting ANC and support the necessity of further studies to optimize the pH_stat leaching procedure before the test can be recommended in regulations for environmental protection.  相似文献