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1.
This paper compares the 1.67–1.47 Ga rapakivi granites of Finland and vicinity to the 1.70–1.68 Ga rapakivi granites of the Beijing area in China, the anorogenic 130 Ma granites of western Namibia, and the 20–15 Ma granites of the Colorado River extensional corridor in the Basin and Range Province of southern Nevada. In Finland and China, the tectonic setting was incipient, aborted rifting of Paleoproterozoic or Archean continental crust, in Namibia it was continental rifting and mantle plume activity that led to the opening of southern Atlantic at 130 Ma. The 20–15 Ma granites of southern Nevada were related to rifting that followed the Triassic–Paleogene subduction of the Farallon plate beneath the southwestern United States. In all cases, extension-related magmatism was bimodal and accompanied by swarms of diabase and rhyolite–quartz latite dikes. Rapakivi texture with plagioclase-mantled alkali feldspar megacrysts occurs in varying amounts in the granites, and the latest intrusive phases are commonly topaz-bearing granites or rhyolites that may host tin, tungsten, and beryllium mineralization. The granites are typically ferroan alkali-calcic metaluminous to slightly peraluminous rocks with A-type and within-plate geochemical and mineralogical characteristics. Isotope studies (Nd, Sr) suggest dominant crustal sources for the granites. The preferred genetic model is magmatic underplating involving dehydration melting of intermediate-felsic deep crust. Juvenile mafic magma was incorporated either via magma mingling and mixing, or by remelting of newly hybridized lower crust. In Namibia, partial melting of subcontinental lithospheric mantle was caused by the Tristan mantle plume, in the other cases the origin of the mantle magmatism is controversial. For the Fennoscandian suites, extensive long-time mantle upwelling associated with periodic, migrating melting of the subcontinental lithospheric mantle, governed by heat flow and deep crustal structures, is suggested. 相似文献
2.
Jari Nobrega Cardoso Francisco Radler De Aquino Neto Ren Rodrigues Luiz A.F. Trindade 《Organic Geochemistry》1986,10(4-6)
The distributions of polycyclic alkanes were monitored in a Neocomian sequence (well 1-ESS-34) from the Espirito Santo Basin, southeast Brazil. The profiles included, apart from regular hopanes, significant concentrations of 18α(H), 28,30-bisnorhopane and subordinate amounts of gammacerane. Sterane concentrations, normally with hopane/sterane <5, were compatible with other geochemical data indicating a predominantly planktonic/microbial source of the deposited organic matter. Sample maturities ranged from very immature to the onset of oil generation, allowing biomarker distributions to be followed along a broad maturation range. The ability of certain molecular ratios (e.g. C27 17α(H)/17β(H)hopanes) to reflect a maturity sequence with depth in the closely-spaced strata of the immature upper levels (Jiquiá Stage) showed the value of molecular techniques over classical geochemical methods (e.g. vitrinite reflectance) for the study of immature sequences. The presence in the oils of southern Espirito Santo of 28,30-bisnorhopane, gammacerane and methyl steranes in similar concentrations as in extracts of the deepest levels of the 1-ESS-34 well qualify the Jiquia Stage as the probable source rock of oils accumulated in the basin. 相似文献
3.
Ecological optima and tolerances with respect to autumn pH were estimated for 63 diatom taxa in 47 Finnish lakes. The methods used were weighted averaging (WA), least squares (LS) and maximum likelihood (ML), the two latter methods assuming the Gaussian response model.WA produces optimum estimates which are necessarily within the observed lake pH range, whereas there is no such restriction in ML and LS. When the most extreme estimates of ML and LS were excluded, a reasonably close agreement among the results of different estimation methods was observed. When the species with unrealistic optima were excluded, the tolerance estimates were also rather similar, although the ML estimates were systematically greater.The parameter estimates were used to predict the autumn pH of 34 other lakes by weighted averaging. The ML and LS estimates including the extreme optima produced inferior predictions. A good prediction was obtained, however, when prediction with these estimates was additionally scaled with inverse squared tolerances, or when the extreme values were removed (censored). Tolerance downweighting was perhaps more efficient, and when it was used, no additional improvement was gained by censoring. The WA estimates produced good predictions without any manipulations, but these predictions tended to be biased towards the centroid of the observed range of pH values.At best, the average bias in prediction, as measured by mean difference between predicted and observed pH, was 0.082 pH units and the standard deviation of the differences, measuring the average random prediction error, was 0.256 pH units. 相似文献
4.
The Palaeoproterozoic (1.9 Ga) Rytky and Kotalahti mafic-ultramafic intrusions are located in the contact zone between the Archaean craton and Proterozoic supracrustal rocks. During the second deformation event (D2) the surrounding country rocks were subjected to intensive metamorphism and deformation associated with the Svecofennian orogeny; the Archaean/Proterozoic boundary controlled both D2 thrusting and magma ascent. Emplacement of the Rytky and Kotalahti intrusions took place at the culmination of D2, as shown by the gneiss inclusions with S2 schistosity within the intrusions. Overthrusting continued after emplacement, with detached fragments of the bodies incorporated into the Archaean gneisses. During the third deformation event (D3) the originally subhorizontal intrusions were rotated into a subvertical position, so that they now have their stratigraphic top towards the west. The Rytky intrusion is composed mainly of medium- and coarse-grained lherzolite, websterite and gabbronorite. The nickel deposit with pentlandite as the main nickel mineral is associated with the lherzolite and websterite. The coarse-grained lherzolite, websterite and melagabbro represent the first rocks to form, and they contain the nickel sulphide mineralisation. Country rock contamination, as indicated by high TiO2, P2O5, Rb, Zr and light rare earth element contents (LREE), is most pronounced in the marginal part of the intrusion, which was the first to form. The variation in olivine composition (Fo 78.6-84.77 mole %; Ni 630–2386 ppm) and the metal ratio of the sulphide (Ni/Co 19.3 – 50.3) along with the internal stratigraphy of the intrusion indicate an in-situ process of sulphide ore formation.Editorial handling: P. LightfootAn erratum to this article can be found at 相似文献
5.
Use of biliary PAH metabolites as a biomarker of pollution in fish from the Baltic Sea 总被引：2，自引：0，他引：2
Vuorinen PJ Keinänen M Vuontisjärvi H Barsiene J Broeg K Förlin L Gercken J Kopecka J Köhler A Parkkonen J Pempkowiak J Schiedek D 《Marine pollution bulletin》2006,53(8-9):479-487
During field campaigns of the BEEP project (Biological Effects of Environmental Pollution in Marine Coastal Ecosystems) in 2001-2002, metabolites of polycyclic aromatic hydrocarbons (PAHs) were determined in bile samples from three fish species, flounder (Platichthys flesus), perch (Perca fluviatilis) and eelpout (Zoarces viviparus), from four separate areas in the Baltic Sea. Two determination methods were applied: fixed wavelength fluorescence (FF) for pyrene-type metabolites and high-performance liquid chromatography with fluorescence detection (HPLC). There was a good correlation between the FF method and 1-OH pyrene determined by HPLC. Normalisation of the FF data for absorbance at 380 nm or bile protein concentrations greatly increased variance in one third and decreased it in two thirds of the cases and resulted in a loss of significant differences (protein normalisation) between the sampling stations, but normalisation of the HPLC data had little effect on the results. The biliary PAH metabolite content was usually higher in males than in females. In perch and eelpout the biliary PAH contents were at similar levels, whereas in flounder the levels were lower. The sampling areas arranged in decreasing order of biliary PAH contents were: Wismar Bay > Gulf of Gdansk > Lithuanian coast > Kvadofj?rden (reference area). It is concluded that FF with un-normalised data is a reliable and simple method for monitoring purposes and only one sex of a selected species should be used. 相似文献
6.
Jari J. E. Kajava Juri Poutanen 《Monthly notices of the Royal Astronomical Society》2009,398(3):1450-1460
We study spectral variability of 11 ultraluminous X-ray sources (ULX) using archived XMM–Newton and Chandra observations. We use three models to describe the observed spectra: a power law, a multicolour disc (MCD) and a combination of these two models. We find that seven ULXs show a correlation between the luminosity L X and the photon index Γ. Furthermore, four out of these seven ULXs also show spectral pivoting in the observed energy band. We also find that two ULXs show an L X –Γ anticorrelation. The spectra of four ULXs in the sample can be adequately fitted with a MCD model. We compare these sources to known black hole binaries (BHB) and find that they follow similar paths in their luminosity–temperature diagrams. Finally, we show that the 'soft excess' reported for many of these ULXs at ∼0.2 keV seems to roughly follow a trend L soft ∝ T −3.5 when modelled with a power law plus a 'cool' MCD model. This is contrary to the L ∝ T 4 relation that is expected from theory and what is seen for many accreting BHBs. The observed trend could instead arise from disc emission beamed by an outflowing wind around a ∼10 M⊙ black hole. 相似文献
7.
To model ice conditions in the eastern Gulf of Finland, a high-resolution three-dimensional hydrodynamic model is coupled with the advanced sea-ice model HELMI (Haapala et al., 2005). To test the model in extreme situations, the ice pattern in the eastern Gulf of Finland was simulated for a mild ice winter (2007–2008) and for a moderate one (2003–2004). The reference runs were performed on the assumption that the ice in the model domain is fast ice if the sea depth is less than 10 m. Using this assumption, the ice thickness averaged over the Neva Bay (the easternmost part of the Gulf of Finland) is overestimated by the model for almost the entire wintertime in the mild winter and during the ice formation and melting periods in the moderate winter, as compared with the thickness reported in ice charts. 相似文献
8.
Quarry faces several kilometers long in the Glesborg area in Denmark show that Bronze Age farmers used a sustainable land‐use system. Despite nutrient‐poor soils, the Glesborg area was under a rotation system in which cropland alternated with grassland. Soil fertility was improved by the addition of household waste and probably also by locally obtained inorganic fertilizer. The soil surface was very stable, and local drift sand movement was limited. Toward the end of the Bronze Age, the landscape changed dramatically with the arrival of overwhelming amounts of drift sand, and farmsteads were abandoned. Subsequent land use on these poor fine sandy soils was no longer capable of maintaining a stable soil surface, and frequent erosion/sedimentation events of more local importance took place. The post‐Bronze Age landscape may have been mainly a shifting mosaic of heathland with some temporary arable fields and deflation/accumulation areas. This landscape persisted up to about 200 years ago, when afforestation programs started. © 2007 Wiley Periodicals, Inc. 相似文献
9.
Samuli Helama Jianmin Jiang Johanna Korhonen Jari Holopainen Mauri Timonen 《地理学报(英文版)》2013,23(6):1069-1079
Cryophenological records （i.e. observational series of freeze and breakup dates of ice） are of great importance when assessing the environmental variations in cold regions. Here we employed the extraordinarily long observational records of river ice breakup dates and air temperatures in northern Fennoscandia to examine their interrelations since 1802. Historical observations, along with modern data, comprise the informational setting for this analysis carried out using t-test. Temperature history of April-May season was used as cli- matic counterpart for the breakup timings. Both records （temperature and breakup） showed seven sub-periods during which their local means were distinctly different relative to preced- ing and subsequent sub-periods. The starting and ending years of these sub-periods oc- curred in temporal agreement. The main findings of this study are summarized as follows： （1） the synchrony between the temperature and river ice breakup records ruled out the possibility that the changes would have occurred due to quality of the historical series （i.e. inhomoge- neity problems often linked to historical time-series）; （2） the studied records agreed to show lower spring temperatures and later river ice breakups during the 19th century, in comparison to the 20th century conditions, evidencing the prevalence of cooler spring temperatures in the study region, in agreement with the concept of the Little Ice Age （1570-1900） climate in North-West Europe; （3） the most recent sub-period demonstrate the highest spring tem- peratures with concomitantly earliest river ice breakups, showing the relative warmth of the current springtime climate in the study region in the context of the past two centuries; （4） the effects of anthropogenic changes in the river environment （e.g. construction and demolition of dams） during the 20th century should be considered for non-climatic variations in the breakup records; （5） this study emphasizes the importance of multi-centurial （i.e. historical） cryo- phenological information for highly interesting viewpoints of climate and environmental his- tory. 相似文献
10.