排序方式： 共有29条查询结果，搜索用时 15 毫秒
21.
In the Variscan Western Tatra granites hybridization phenomena such as mixing and mingling can be observed at the contact of mafic precursors of dioritic composition and more felsic granitic host rocks. The textural evidence of hybridization include: plagioclase?CK-feldspar?Csphene ocelli, hornblende- and biotite-rimmed quartz ocelli, plagioclase with Ca-rich spike zonation, inversely zoned K-feldspar crystals, mafic clots, poikilitic plagioclase and quartz crystals, mixed apatite morphologies, zoned K-feldspar phenocrysts. The apparent pressure range of the magma hybridization event was calculated at 6.1?kbar to 4.6?kbar, while the temperature, calculated by independent methods, is in the range of 810°C?770°C. U-Pb age data of the hybrid rocks were obtained by in-situ LA-MC-ICP-MS analysis of zircon. The oscillatory zoned zircon crystals yield a concordia age of 368?±?8?Ma (MSWD?=?1.1), interpreted as the age of magma hybridization and timing of formation of the magmatic precursors. It is the oldest Variscan magmatic event in that part of the Tatra Mountains. 相似文献
22.
23.
Assessment of the Global and Regional Land Hydrosphere and Its Impact on the Balance of the Geophysical Excitation Function of Polar Motion 总被引：2，自引：0，他引：2
The impact of continental hydrological loading from land water, snow and ice on polar motion excitation, calculated as hydrological angular momentum (HAM), is difficult to estimate, and not as much is known about it as about atmospheric angular momentum (AAM) and oceanic angular momentum (OAM). In this paper, regional hydrological excitations to polar motion are investigated using monthly terrestrial water storage data derived from the Gravity Recovery and Climate Experiment (GRACE) mission and from the five models of land hydrology. The results show that the areas where the variance shows large variability are similar for the different models of land hydrology and for the GRACE data. Areas which have a small amplitude on the maps make an important contribution to the global hydrological excitation function of polar motion. The comparison of geodetic residuals and global hydrological excitation functions of polar motion shows that none of the hydrological excitation has enough energy to significantly improve the agreement between the observed geodetic excitation and geophysical ones. 相似文献
24.
Marek Wo
niak Jolanta Ga&#x;&#x;zka‐Friedman Przemys&#x;aw Duda Martyna Jakubowska Patrycja Rzepecka &#x;ukasz Karwowski 《Meteoritics & planetary science》2019,54(8):1828-1839
Mössbauer spectra of equilibrated ordinary chondrites consist of two doublets due to paramagnetic iron present in olivines and pyroxenes and two sextets due to magnetically ordered iron present in metallic phases and troilite. The spectral areas of the different mineralogical phases found by Mössbauer spectroscopy in meteorites are proportional to the number of iron atoms in this mineralogical phase. This property of Mössbauer spectra can be the basis for constructing a method for the classification of ordinary chondrites. This idea was first explored at the Mössbauer Laboratory in Kanpur. This group suggested a qualitative method based on 2‐dimensional plots of Mössbauer spectral areas and thus classified properly some meteorites. We constructed a quantitative method using Mössbauer spectral areas, multidimensional discriminant analysis, and Mahalanobis distance (4M method) to determine the probability of a meteorite to be of type H, L, or LL. Based on 59 Mössbauer spectra, we calculated by the 4M method, S cluster , the level of similarity of the Goronyo meteorite to the clusters. On the plot of ferrosilite versus fayalite, the point representing Goronyo is located on the border between H and L areas. Calculated by the 4M method, the meteorite Goronyo is 32% similar to type H, 75% to type L, and 11% to type LL. Additional mineralogical analyses suggested that the Goronyo meteorite would be classified as type L, although it was originally reported as type H in the Meteoritical Bulletin Database. 相似文献
25.
Reiner Botz Mark Schmidt Jolanta Kus Christian Ostertag-Henning Axel Ehrhardt Nazli Olgun Dieter Garbe-Schönberg Jan Scholten 《Chemical Geology》2011,280(1-2):126-143
Parasound profiles across the Shaban Deep in the Red Sea indicate turbiditic transport of surface sediments from the topographic height (basalt ridge) into the interior of the deep. This is supported by petrographical and (isotope-) geochemical evidence in the East Basin of the Shaban Deep where the presence of variable mixtures of authochtonous and allochthonous sediment compounds had been found.The uppermost 170 cm of both sediment cores 17008-1 and 17009-3 reveal “normal” stable oxygen isotope values for the planktonic foraminifera Globigerinoides ruber near ?1‰ which is indicative for carbonate formation in Red Sea surface water around 27 °C. However, below 182 cm in core 17008-1 highly variable δ 18O values for G. ruber between 0.26 and ?10.68‰ occur which are not the result of temperature-controlled oxygen isotope fractionation between foraminiferal carbonate and Red Sea surface water. The lowest δ18O values of ?10.68‰ measured for highly-altered foraminifera shells suggests carbonate precipitation higher than 90 °C.Organic petrographical observations show a great diversity of marine-derived macerals and terrigenous organic particles. Based on petrographical investigations sediment core 17008-1 can be subdivided in intervals predominantly of authochtonous character (i.e. 1, 3, 5 corresponding to core depths 0–170 cm, 370–415 cm, 69–136 cm), and allochthonous/thermally altered character (e.g. 2 and 4 corresponding to core depths 189–353 cm and 515–671 cm). Allochthonous/thermally altered material displays a wide to an extremely wide range of maturities (0.38–1.42% Rr) and also natural coke particles were found.Similarly, the organic geochemical and pyrolysis data indicate the predominance of well-preserved, immature algal and bacterial remains with a minor contribution of land plant material. Sediments below 170 cm (core 17008-1) contain contributions of re-sedimented pre-heated material most likely from the area of the basaltic ridge. This is documented by individual coke particles reduced hydrogen indices and elevated Tmax values up to 440 °C.An “oil-type” contribution (evidenced by mature biomarkers, hopene/hopane ratios, elevated background fluorescence, n-alkane distribution) is also present in the sediments which most likely originated at greater depth and impregnated the surface sediments.The heat source responsible for recrystallisation of foraminiferal carbonate and maturation of organic particles in Shaban Deep sediments most likely is attributed to modern basalt extrusions which now separate the Shaban Deep subbasins. 相似文献
26.
Continental hydrological loading by land water, snow and ice is a process that is important for the full understanding of the excitation of polar motion. In this study, we compute different estimations of hydrological excitation functions of polar motion (as hydrological angular momentum, HAM) using various variables from the Global Land Data Assimilation System (GLDAS) models of the land-based hydrosphere. The main aim of this study is to show the influence of variables from different hydrological processes including evapotranspiration, runoff, snowmelt and soil moisture, on polar motion excitations at annual and short-term timescales. Hydrological excitation functions of polar motion are determined using selected variables of these GLDAS realizations. Furthermore, we use time-variable gravity field solutions from the Gravity Recovery and Climate Experiment (GRACE) to determine the hydrological mass effects on polar motion excitation. We first conduct an intercomparison of the maps of variations of regional hydrological excitation functions, timing and phase diagrams of different regional and global HAMs. Next, we estimate the hydrological signal in geodetically observed polar motion excitation as a residual by subtracting the contributions of atmospheric angular momentum and oceanic angular momentum. Finally, the hydrological excitations are compared with those hydrological signals determined from residuals of the observed polar motion excitation series. The results will help us understand the relative importance of polar motion excitation within the individual hydrological processes, based on hydrological modeling. This method will allow us to estimate how well the polar motion excitation budget in the seasonal and inter-annual spectral ranges can be closed. 相似文献
27.
P. A. Floyd J. A. Winchester J. Ciesielczuk A. Lewandowska J. Szczepanski K. Turniak 《International Journal of Earth Sciences》1996,85(2):225-238
Orthoamphibolites within and marginal to the Orlica-Śnieżnik dome in the eastern Bohemian massif are associated with a series
of Proterozoic-Lower Palaeozoic supracrustal meta-sediments of the Stronie, Nové Město and Staré Město formations. Massive
and variably foliated amphibolites range from common epidote-plagioclase-blue-green/green hornblende varieties to assemblages
with diopside, garnet and brown amphibole. All the amphibolites have a basaltic composition and are divided into three main
chemical groups which are intimately associated in the field: main series tholeiites, low-Ti tholeiites and alkali basalts.
All groups exhibit a common enrichment in LIL elements+Nb+Ta (relative to high-field-strength elements) which reflects contamination
by upper continental crust and/or pelagic sediment compositions. The gross chemistry of the tholeiitesapproaches that for MORB, although the geological environment and nature of crustal contamination suggests that the basaltic precursors
were probably emplaced in a rifted ensialic basinal environment. If the amphibolites are representative of an early phase
of the Lower Palaeozoic fragmentation of Gondwanaland, then rifting did not fully develop ocean crust. The wider significance
of the chemical interpretation implies that some of the variation from Variscan Proterozoic-Palaeozoic metabasite suites that
is ascribed to a complex of different eruptive settings could be accounted for by variable contamination and/or source composition. 相似文献
28.
Artur Poręba Wacław M. Zuberek Jolanta Nogaj-Chachaj Andrzej Kotyrba Sławomir Siwek 《Acta Geophysica》2007,55(4):640-651
The aim of the research was to examine subsurface soil layers with the use of the Ground Penetrating Radar (GPR) method. Neolithic
archaeological post in Karmanowice was examined. On the basis of earlier geophysical researches and archaeological premises,
eight measurement profiles had been chosen. Ground Penetrating Radar system with antenna of 500 MHz frequency was applied.
The measurements were made with 30 and 60 ns time windows. The results were shown as the GPR sections. The analysis of the
obtained results allowed us to outline anomalies connected with the appearance of archaeological objects in subsurface soil
layers. The border between the anthropogenically changed upper layer and undisturbed loess was established, and the sections
of slope wash layers were designated. Anomalies were confirmed by digging and test drillings. Additionally, 2D resistivity
imaging method was used for verification of specific anthropogenic anomalies. 相似文献
29.
