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101.
High-pressure behavior of natural single-crystal epidote and clinozoisite up to 40 GPa 总被引:2,自引:0,他引:2
Fei Qin Xiang Wu Ying Wang Dawei Fan Shan Qin Ke Yang Joshua P. Townsend Steven D. Jacobsen 《Physics and Chemistry of Minerals》2016,43(9):649-659
The comparative compressibility and high-pressure stability of a natural epidote (0.79 Fe-total per formula unit, Fetot pfu) and clinozoisite (0.40 Fetot pfu) were investigated by single-crystal X-ray diffraction and Raman spectroscopy. The lattice parameters of both phases exhibit continuous compression behavior up to 30 GPa without evidence of phase transformation. Pressure–volume data for both phases were fitted to a third-order Birch–Murnaghan equation of state with V 0 = 461.1(1) Å3, K 0 = 115(2) GPa, and \(K_{0}^{'}\) = 3.7(2) for epidote and V 0 = 457.8(1) Å3, K 0 = 142(3) GPa, and \(K_{0}^{'}\) = 5.2(4) for clinozoisite. In both epidote and clinozoisite, the b-axis is the stiffest direction, and the ratios of axial compressibility are 1.19:1.00:1.15 for epidote and 1.82:1.00:1.19 for clinozoisite. Whereas the compressibility of the a-axis is nearly the same for both phases, the b- and c-axes of the epidote are about 1.5 times more compressible than in clinozoisite, consistent with epidote having a lower bulk modulus. Raman spectra collected up to 40.4 GPa also show no indication of phase transformation and were used to obtain mode Grüneisen parameters (γ i) for Si–O vibrations, which were found to be 0.5–0.8, typical for hydrous silicate minerals. The average pressure coefficient of Raman frequency shifts for M–O modes in epidote, 2.61(6) cm?1/GPa, is larger than found for clinozoisite, 2.40(6) cm?1/GPa, mainly due to the different compressibility of FeO6 and AlO6 octahedra in M3 sites. Epidote and clinozoisite contain about 2 wt% H2O are thus potentially important carriers of water in subducted slabs. 相似文献
102.
Anna K. Sim Kristina J. Thomsen Andrew S. Murray Geraldine Jacobsen Russell Drysdale Wayne Erskine 《Boreas: An International Journal of Quaternary Research》2014,43(1):1-21
Two fluvial sediment cores taken from a floodplain of the Hawkesbury‐Nepean River system in the Sydney region, eastern Australia are dated using Optically Stimulated Luminescence (OSL) to provide a reliable chronology essential for the management and planning of water resources. Nine charcoal 14C (AMS) dates constrain these OSL ages. Quartz extracted from seven OSL samples from each of the cores was measured using both single‐grain and multi‐grain OSL techniques. Three of the single‐grain natural dose distributions appear to be well bleached, but the others appear to be incompletely bleached to various degrees. Three minimum‐age models (MAM, MAMUL and IEU) are applied to the single‐grain dose distributions. We conclude that these models give consistent age estimates. For one of the cores it appears to be necessary to use a minimum‐age model to obtain accurate ages, but in the other core incomplete bleaching is probably less important than postdepositional mixing and mixing during sampling. As a result, the burial age is probably best estimated using the weighted average of the individual single‐grain dose estimates. The application of multi‐grain OSL techniques to these samples results in an average apparent age overestimation of ~200 years, which is significant for these samples, but negligible for sediments older than a few thousand years. The intention is that the chronology obtained in this study will be used in conjunction with a proxy flood record, derived from floodplain sediments, to gain an understanding of the long‐term variability in periods of high and low rainfall in eastern Australia. 相似文献
103.
104.
Stefan Tilmes JØrgen Brandt Frode FlatØy Robert Bergström Johannes Flemming Joakim Langner Jesper H. Christensen Lise M. Frohn Øystein Hov Ingo Jacobsen Eberthard Reimer Rainer Stern Jörg Zimmermann 《Journal of Atmospheric Chemistry》2002,42(1):91-121
Eulerian state-of-the-art air pollution forecasting systems on the European scale are operated routinely by several countries in Europe. DWD and FUB, both Germany, NERI, Denmark, NILU, Norway, and SMHI, Sweden, operate some of these systems. To apply such modeling systems, e.g. for regulatory purposes according to new EU directives, an evaluation and comparison of the model systems is fundamental in order to assess their reliability. One step in this direction is presented in this study: The model forecasts from all five systems have been compared to measurements of ground level ozone in Germany. The outstanding point in this investigation is the availability of a huge amount of data – from forecasts by the different model systems and from observations. This allows for a thorough interpretation of the findings and assures the significance of the observed features. Data from more than 300 measurement stations for a 5-month period (May–September 1999) of the German monitoring networks have been used in this comparison. Different spatial and temporal statistical parameters were applied in the evaluation. Generally, it was found that the most comprehensive models gave the best results. However, the less comprehensive and computational cheaper models also produced good results. The extensive comparison made it possible to point out weak points in the different models and to describe the individual model behavior for a full summer period in a climatological sense. The comparison also gave valuable information for an assessment of individual measurement stations and complete monitoring networks in terms of the representativeness of the observation data. 相似文献
105.
Rb-Sr isotope data are presented for gneisses, migmatite neosome material and granitic and gabbroic intrusive rocks from the southern part of the Kongsberg sector, south Norway. The maximum age of the crust in this area appears to be ~1.6 AE. Two metamorphic episodes at ~1.5–1.6 AE and at ~1.1–1.2 AE are recognized. Initial 87Sr/86Sr ratios for the granitic rocks give evidence for reworking of sialic crust and indicate that approximately 1.6 AE old crust repeatedly acted as a source for granitic magmas for a timespan of ~0.5 AE. 相似文献
106.
The Messina Copper Mines comprise a group of breccia pipes, disseminated replacement and fissure deposits within an area 20 km long by 1 km wide, emplaced within high-grade metamorphic rocks of the Limpopo mobile belt. Breccia pipes as well as associated hydrothermal copper deposits are aligned along a northeast trend which forms a southwestern projection of the Nuanetsi Igneous Province. The "L" and West lode breccia columns are known over a vertical extent of 1 250 metres, and are not exposed on surface; they are circular to polygonal in plan outline, as a result of joint controls. Peripheral microbreccia grades downwards and inwards to macrobreccia. Downward displacement of country rock marker zones indicate a maximum 1 – 3 per cent volume increase, while observed interfragmental fill constitutes 15 – 25 per cent. Hydrothermal alteration of wallrock gneiss mantles the breccia columns and does not extend to surface; it is comprised of distinct zones, the outermost characterized by sericitized gneiss, grading to an albitite, and finally to zoisite-quartz rock around the immediate brecciated contacts, and within the pipes. The interfragmental fill consists largely of quartz and sulphides, and grades downwards to albite + sulphides in the West Lode pipe. Sulphide mineral distribution is zoned, pyrite dominating in the apex of the pipes, grading downwards to chalcopyrite-bornite and then bornite-chalcocite at deeper levels. The nature of the fragmentation precludes normal stoping collapse mechanisms for brecciation and suggests a single implosive event. Chemical reaction induced shrinkage of fragments probably created the bulk of the interfragmental volume. 相似文献
107.
A Fourier transformation of the magnetic field from a magnetized sphere allows a particularly simple interpretation of the parameters of the sphere. The depth to the centre and total magnetic moments of the sphere are related to the intercept and slope of the power spectrum. The horizontal centre and direction of magnetization are related to slope and intercept of the phase spectra in two perpendicular, horizontal directions. Examples with artificial data contaminated by various noise components are presented. 相似文献
108.
Michael D. Cheetham Annabelle F. Keene Wayne D. Erskine Richard T. Bush Kathryn Fitzsimmons Geraldine E. Jacobsen Stewart J. Fallon 《第四纪科学杂志》2010,25(7):1160-1168
A previous assessment of radiocarbon (14C) dates from alluvial units in southeastern Australia revealed a gap in the geochronological record that coincides with the Holocene climatic optimum. This gap in the alluvial record can be further refined using optically stimulated luminescence (OSL). The chronology of Holocene river terraces on Widden Brook, a sandy alluvial stream in southeastern Australia, was established using 14C and OSL techniques. Combined use of these independent techniques allows for a more rigorous assessment of the alluvial record. The robust chronology, consisting of 38 14C and 11 OSL samples, permitted identification of significant depositional variation within the catchment, resulting from localised geomorphic processes. The three terrace sequences identified yielded distinct chronologies, suggesting alluvial deposition at different times. The sequences exhibited a continuous chronology, which indicated continuous deposition throughout the Holocene. The chronology of terrace sequences within this catchment suggests that terrace formation can be attributed to localised geomorphic processes rather than climatic forcing. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
109.
Pedotransfer functions estimating soil hydraulic properties using different soil parameters 总被引:1,自引:0,他引:1
Estimates of soil hydraulic properties using pedotransfer functions (PTF) are useful in many studies such as hydrochemical modelling and soil mapping. The objective of this study was to calibrate and test parametric PTFs that predict soil water retention and unsaturated hydraulic conductivity parameters. The PTFs are based on neural networks and the Bootstrap method using different sets of predictors and predict the van Genuchten/Mualem parameters. A Danish soil data set (152 horizons) dominated by sandy and sandy loamy soils was used in the development of PTFs to predict the Mualem hydraulic conductivity parameters. A larger data set (1618 horizons) with a broader textural range was used in the development of PTFs to predict the van Genuchten parameters. The PTFs using either three or seven textural classes combined with soil organic mater and bulk density gave the most reliable predictions of the hydraulic properties of the studied soils. We found that introducing measured water content as a predictor generally gave lower errors for water retention predictions and higher errors for conductivity predictions. The best of the developed PTFs for predicting hydraulic conductivity was tested against PTFs from the literature using a subdata set of the data used in the calibration. The test showed that the developed PTFs gave better predictions (lower errors) than the PTFs from the literature. This is not surprising since the developed PTFs are based mainly on hydraulic conductivity data near saturation and sandier soils than the PTFs from the literature. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
110.
In 2008 two male sperm whales (Physeter macrocephalus) stranded along the northern California coast with large amounts of fishing net scraps, rope, and other plastic debris in their stomachs. One animal had a ruptured stomach, the other was emaciated, and gastric impaction was suspected as the cause of both deaths. There were 134 different types of nets in these two animals, all made of floating material, varying in size from 10 cm2 to about 16 m2. The variability in size and age of the pieces suggests the material was ingested from the surface as debris rather than bitten off from active gear. These strandings demonstrate that ingestion of marine debris can be fatal to large whales, in addition to the well documented entanglements known to impact these species. 相似文献