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991.
Geology of Ore Deposits - Behavior of copper in sulfide-free metasomatic ores of the Pelagonian massif, Republic of North Macedonia has been studied. It is shown that the highest copper activity... 相似文献
992.
993.
Lead Isotopic Composition in Biogenic Certified Reference Materials Determined by Different ICP‐based Mass Spectrometric Techniques 下载免费PDF全文
Jana Ďurišová Lukáš Ackerman Ladislav Strnad Vladislav Chrastný Jan Borovička 《Geostandards and Geoanalytical Research》2015,39(2):209-220
This work presents data for the radiogenic Pb isotopic ratios (206Pb/207Pb and 208Pb/206Pb) in nine biogenic certified reference materials (NIST SRM 1515, 1566b, 1570a, 1573a, 1575a; BCR 100, BCR 101, BCR 670 and IAEA 359), which are suitable for analytical quality control in environmental research. The results were obtained using three different types of ICP‐based mass spectrometer (quadrupole‐based/magnetic sector field single‐collector ICP‐MS instruments and a multi‐collector ICP‐MS) and applying different mass bias correction procedures (calibrator‐sample bracketing and external Tl normalisation) with and without Pb separation from the matrix using ion exchange chromatography. In the majority of the samples, the measurements from all three of the ICP‐MS instruments were in agreement within ± 0.1%, despite the lower analytical precision of the single‐collector ICP‐MS instruments. We demonstrate that the presence of the sample matrix did not significantly influence the Pb isotopic ratios measured by magnetic sector field ICP‐MS, whereas the use of the two different mass bias corrections resulted in a systematic difference of 0.09% for the 208Pb/206Pb ratio. 相似文献
994.
Lukas Krmcek Milan Novak Robert B.Trumbull Jan Cempirek Stanislav Houzar 《地学前缘(英文版)》2021,12(1):219-230
Various metacarbonate and associated calc-silicate rocks form minor but genetically significant components of the lithological units in the Bohemian Massif of the Variscan orogen in Central Europe.These rocks vary in terms of their lithostratigraphy,chemical composition and mineral assemblage(dolomite/calcite ratio,silicate abundance).Tourmaline is present in five paragenetic settings within the metacarbonate and calc-silicate units.TypeⅠcomprises individual,euhedral,prismatic grains and grain aggregates in a carbonate-dominant(calcite±dolomite)matrix poor in silicates.TypeⅡis characterized by euhedral to subhedral grains and coarse-to fine-grained aggregates in silicate-rich layers/nests within metacarbonate bodies whereas typeⅢoccurs as prismatic grains and aggregates at the contact zones between carbonate and associated silicate host rocks.TypeⅣis in veins crosscutting metacarbonate bodies,and typeⅣtourmaline occurs at the exocontacts of elbaite-subtype granitic pegmatite.Tourmaline from the different settings shows distinctive compositional features.Typical for typeⅠare Mg-rich compositions,with fluor-uvite>dravite>>magnesio-lucchesiite.Tourmalines from typeⅡsilicate-rich layers/nests are highly variable,corresponding to oxy-schorl,magnesio-foitite,Al-rich dravite and fluor-uvite.Typical for typeⅢtourmalines are Ca,Ti-bearing oxy-dravite compositions.The typeⅣveins feature dravite and fluor-uvite tourmaline compositions whereas typeⅤtourmaline is Li,F-rich dravite.Tourmaline is the only Bbearing phase in paragenetic typesⅠ-Ⅳ,where it is characterised by two principal ranges of B-isotope composition(δ^11B=-13‰to-9‰and-18‰to-14‰).These ranges correspond to regionally different units of the Moldanubian Zone.Thus,the Svratka Unit(Moldanubian Zone s.l.)contains only isotopically lighter tourmaline(δ^11B=-18‰to-14‰),whereas metacarbonates in the Poli?ka unit(Teplá-Barrandian Zone)and Olesnice unit(Moravicum of the Moravo-Silesian Zone)has exclusively isotopically heavier tourmaline(δ^11B=-9‰to-13‰).Tourmalines from metacarbonates in the Variegated Unit cover both ranges of isotope composition.The isotopically light end of the B isotope range may indicate the presence of continental evaporites within individual investigated areas.On the other hand,variations in the range of~8δ-units is consistent with the reported shift in B isotopic composition of metasedimentary rocks of the Bohemian Massif due to the prograde metamorphism from very-low grade to eclogite facies.In contrast to the metacarbonate-hosted settings,tourmaline of paragenetic type V from the exocontact of granitic pegmatites displays a significantly heavier range ofδ^11B(as low as-7.7‰to-0.6‰),which is attributed to partitioning of 10 B to cogenetic axinite and/or different B-signature of the source pegmatite containing tourmaline with heavyδ^11B signature. 相似文献
995.
Stanley D. Brunn Kvetoslava Matlovičová Alexander Mušinka René Matlovič 《GeoJournal》2018,83(4):853-869
This paper presents the results of the latest sociographical research into the contemporary Roma community in Slovakia. The introduction provides an overview of Roma in Slovakian territory in the past and the various attempts by the government to calculate their numbers and ethnicity. The second part presents the 2013 in-depth and innovative field methodology used to tabulate Roma numbers and map major social characteristics of the Roma population. The information focuses on key social and economic characteristics. Maps reveal the spatial distribution of Roma in Slovakia, including subethnic groups, together with a classification of their settlements and infrastructures, and data on their education and employment structure which are useful in social policy planning. Given that few similar detailed studies on the Roma have yet been carried out in other European countries, this contribution highlights methodology and mapping efforts that could be adopted elsewhere. 相似文献
996.
J. Laštovička J. Baše F. Hruška J. Chum T. Šindelářová J. Horálek J. Zedník V. Krasnov 《Journal of Atmospheric and Solar》2010,72(16):1231-1240
Various pre-seismic and co-seismic effects have been reported in the literature in the solid Earth, hydrosphere, atmosphere, electric/magnetic field and in the ionosphere. Some of the effects observed above the surface, particularly some of the pre-seismic effects, are still a matter of debate. Here we analyze the co-seismic effects of a relatively weak earthquake of 28 October 2008, which was a part of an earthquake swarm in the westernmost region of the Czech Republic. Special attention is paid to unique measurements of infrasonic phenomena. As far as we know, these have been the first infrasonic measurements during earthquake in the epicentre zone. Infrasonic oscillations (~1–12 Hz) in the epicentre region appear to be excited essentially by the vertical seismic oscillations. The observed oscillations are real epicentral infrasound not caused by seismic shaking of the instruments or by meteorological phenomena. Seismo-infrasonic oscillations observed 155 km apart from the epicentre were excited in situ by seismic waves. No earthquake-related infrasonic effects have been observed in the ionosphere. Necessity to make vibration tests of instruments is pointed out in order to be sure that observed effects are not effects of mechanical shaking of the instrument. 相似文献
997.
Audrius Dubietis Peter Dalin Ričardas Balčiūnas Kazimieras Černis 《Journal of Atmospheric and Solar》2010,72(14-15):1090-1099
We present an analysis of systematic visual and photographic observations of noctilucent clouds seen from Lithuania in the years 1973–2009. The main trends in the noctilucent cloud occurrence frequency and the mean brightness are derived from statistical and correlation analysis. A clear signature of the solar activity cycle is imprinted on the noctilucent cloud occurrence frequency and mean brightness, both showing distinct anti-correlation with the sunspot numbers; however, no statistically significant increase of either noctilucent cloud occurrence frequency or brightness has been detected at least over past 19 yr (1991–2009). The only statistically significant positive trend is established for the numbers of very bright noctilucent cloud displays in the years 1973–2009. The most recent noctilucent cloud observations are linked to variations of local mesospheric temperatures, measured by the Aura satellite. 相似文献
998.
Microtremor study of site effects and soil-structure resonance in the city of Ljubljana (central Slovenia) 总被引:1,自引:0,他引:1
Andrej Gosar Janez Rošer Barbara Šket Motnikar Polona Zupančič 《Bulletin of Earthquake Engineering》2010,8(3):571-592
The city of Ljubljana is located in one of the three areas with the highest seismic hazard in Slovenia, and it is also the
most densely populated. Site effects due to Quaternary sediments, which fill the up to 200 m-deep basin, are characteristic
of the whole city area, but they can be especially strong in the southern part of Ljubljana, which is built on very soft lacustrine
deposits. Existing microzonation studies of the city are inadequate, since there is a lack of borehole, geophysical and earthquake
data. The microtremor horizontal-to-vertical spectral ratio (HVSR) method was therefore applied to a 200 m dense grid of free-field
measurements over an area of 45 km2 (1,223 measuring points) in order to assess the fundamental frequency of the sediments. The main difficulties in microtremor
measurement arose from high levels of traffic and industrial noise, and from underground structures. Experimental conditions
which can influence data quality, such as strong wind and water saturation of soil, were analysed. Very clear HVSR peaks were
obtained in the entire southern part of the city, whereas in the northern part the site response is in general lower due to
lower impedance contrast of gravel with the bedrock. The iso-frequency map of sediments shows a distribution in the range
of 0.9–10 Hz. In the southern part of Ljubljana, sediment frequency correlates well with the thickness of soft sediments known
from geophysical investigations and sparse drilling. Average amplitude of the HVSR peaks is considerably higher in the southern
part (6.7 ± 2.4) than in the northern part (4.0 ± 2.0) of the city, indicating a high impedance contrast of lacustrine sediments
with the bedrock. Microtremor measurements were also performed inside 122 buildings of various heights. We focused on important
public buildings and selected blocks of flats and houses. To assess the longitudinal and transverse fundamental frequencies
of each building, amplitude spectra and the spectral ratio between the upper floor and the basement were analysed for both
directions. When one of these frequencies is close to a nearby free-field fundamental frequency, a potential soil-structure
resonance is present. This was found in 12 of the measured buildings. Three of them are tall residential buildings (from 10
to 15 floors) with a fundamental frequency of 2–3 Hz, and nine of them are low-rise buildings (from 3 to 5 floors) with a
fundamental frequency ranging from 3 to 4.5 Hz. Using the relationship between fundamental frequency and height, the typical
height of buildings that might cause soil-structure resonance can be estimated at a given sediment frequency obtained from
free-field measurements. 相似文献
999.
M. R. Gallipoli M. Mucciarelli B. Šket-Motnikar P. Zupanćić A. Gosar S. Prevolnik M. Herak J. Stipčević D. Herak Z. Milutinović T. Olumćeva 《Bulletin of Earthquake Engineering》2010,8(3):593-607
During a three year-period, the participants of a NATO Science for Peace project performed ambient noise measurements inside buildings in four European countries. This paper reports the results relevant to reinforced concrete (RC) buildings with height in the range 1–20 floors. The total number of such buildings surveyed is 244. The most striking feature is the similarity of the height-period relationships in the four countries, which allowed the treatment of the all measurements as a single database. We found no significant correlation with other variables, and calculated a regression that is very similar to other empirical height-period relationships and quite different from code provisions and theoretical models. 相似文献
1000.
P. Vaníček J. Huang P. Novák S. Pagiatakis M. Véronneau Z. Martinec W. E. Featherstone 《Journal of Geodesy》1999,73(4):180-192
The definition of the mean Helmert anomaly is reviewed and the theoretically correct procedure for computing this quantity
on the Earth's surface and on the Helmert co-geoid is suggested. This includes a discussion of the role of the direct topographical
and atmospherical effects, primary and secondary indirect topographical and atmospherical effects, ellipsoidal corrections
to the gravity anomaly, its downward continuation and other effects. For the rigorous derivations it was found necessary to
treat the gravity anomaly systematically as a point function, defined by means of the fundamental gravimetric equation. It
is this treatment that allows one to formulate the corrections necessary for computing the `one-centimetre geoid'. Compared
to the standard treatment, it is shown that a `correction for the quasigeoid-to-geoid separation', amounting to about 3 cm
for our area of interest, has to be considered. It is also shown that the `secondary indirect effect' has to be evaluated
at the topography rather than at the geoid level. This results in another difference of the order of several centimetres in
the area of interest. An approach is then proposed for determining the mean Helmert anomalies from gravity data observed on
the Earth's surface. This approach is based on the widely-held belief that complete Bouguer anomalies are generally fairly
smooth and thus particularly useful for interpolation, approximation and averaging. Numerical results from the Canadian Rocky
Mountains for all the corrections as well as the downward continuation are shown.
Received: 9 March 1998 / Accepted: 16 November 1998 相似文献