Hydroxyl in mantle olivine xenocrysts from the Udachnaya kimberlite pipe   总被引：6，自引：1，他引：5  

Monika Koch-Müller  Stanislav S. Matsyuk  Dieter Rhede  Richard Wirth  Natasha Khisina 《Physics and Chemistry of Minerals》2006,33(4):276-287

The incorporation of hydrogen in mantle olivine xenocrysts from the Udachnaya kimberlite pipe was investigated by Fourier-transform infrared spectroscopy and secondary ion mass spectrometry (SIMS). IR spectra were collected in the OH stretching region on oriented single crystals using a conventional IR source at ambient conditions and in situ at temperatures down to −180°C as well as with IR synchrotron radiation. The IR spectra of the samples are complex containing more than 20 strongly polarized OH bands in the range 3,730–3,330 cm⁻¹. Bands at high energies (3,730–3,670 cm⁻¹) were assigned to inclusions of serpentine, talc and the 10 Å phase. All other bands are believed to be intrinsic to olivine. The corresponding point defects are (a) associated with vacant Si sites (3,607 cm⁻¹ E || a, 3,597 E || a, 3,571 cm⁻¹ E || c, 3,567 E || c, and 3,556 E || b), and (b) with vacant M1 sites (most of the bands polarized parallel to a). From the pleochroic behavior and position of the OH bands associated with the vacant M1 sites, we propose two types of hydrogen—one bonded to O1 and another to O2, so that both OH vectors are strongly aligned parallel to a. The O2–H groups may be responsible for the OH bands at higher wavenumbers than those for the O1–H groups. The multiplicity of the corresponding OH bands in the spectra can be explained by different chemical environments and by slightly different distortions of the M1 sites in these high-pressure olivines. Four samples were investigated by SIMS. The calculated integral molar absorption coefficient using the IR and SIMS results of 37,500±5,000 L mol H₂O cm⁻² is within the uncertainties slightly higher than the value determined by Bell et al. (J Geophys Res 108(B2):2105–2113, 2003) (28,450±1,830 L mol H₂O cm⁻²). The reason for the difference is the different distributions of the absorption intensity of the spectra of both studies (mean wavenumber 3,548 vs. 3,570 cm⁻¹). Olivine samples with a mean wavenumber of about 3,548 cm⁻¹ should be quantified with the absorption coefficient as determined in this study; those containing more bands at higher wavenumber (mean wavenumber 3,570 cm⁻¹) should be quantified using the value determined by Bell et al. (J Geophys Res 108(B2):2105–2113, 2003).

Monika Koch-MüllerEmail: Phone: +49-331-2881492

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The golden ark: arsenopyrite crystal plasticity and the retention of gold through high strain and metamorphism          下载免费PDF全文

Denis Fougerouse  Steven Micklethwaite  Angela Halfpenny  Steven M. Reddy  John B. Cliff  Laure A. J. Martin  Matt Kilburn  Paul Guagliardo  Stanislav Ulrich 《地学学报》2016,28(3):181-187

Quantitative electron backscatter diffraction analysis and ion microprobe imaging of gold‐rich arsenopyrites provide the first insights into the crystal plasticity and element mobility behaviour of arsenopyrites through metamorphism (340°–460° and 2 kbar). Remarkably, the gold‐rich arsenopyrites remained structurally and chemically robust during high strain deformation. It was only during a superimposed lower strain deformation event, at a high angle to the preferred orientation of the arsenopyrites, that small amounts of crystal plasticity affected the arsenopyrites. During the low strain event, a dissolution–reprecipitation reaction resulted in loss of gold from the crystal lattice, facilitated by localised domains of recrystallisation, most likely due to fluid percolation along sub‐ and new grain boundaries. We suggest that the abundance and rheologically robust nature of gold‐rich arsenopyrite in giant gold deposits, affected by greenschist–amphibolite metamorphism, is actually critical in the preservation of those deposits.  相似文献   

A recent history of metal accumulation in the sediments of Rijeka harbor, Adriatic Sea, Croatia   总被引：2，自引：0，他引：2  

Neven Cukrov  Stanislav Fran?iškovi?-Bilinski 《Marine pollution bulletin》2011,62(1):154-167

We studied metal pollution in the sediments of Rijeka harbor, including anthropogenic influence during recent decades and at the present time. Sediment profiles were collected at ten sampling points. The concentrations of 63 elements in bulk sediment were obtained using ICP-MS, and the concentrations of selected elements were evaluated by statistical factor analyses. We also calculated metal-enrichment factors and geoaccumulation indices and constructed spatial-distribution maps.Mercury (Hg) was the heaviest pollutant, with concentrations exceeding 4 mg/kg. Silver (Ag) was the second most important pollutant, with constantly increasing values. The average concentrations of the most toxic elements were comparable to those found in sediments of other ports throughout the world, and their toxicity ranged from threshold values [chromium (Cr), arsenic (As)] and midrange-effect values [cadmium (Cd), lead (Pb), copper (Cu), zinc (Zn), nickel (Ni)] to extreme-effect values (Hg). Metal pollution has decreased during recent decades, except for Ag and barium (Ba).  相似文献   

Did the circum-Rodinia subduction trigger the Neoproterozoic rifting along the Congo–Kalahari Craton margin?     

Konopásek  Jiří  Janoušek  Vojtěch  Oyhantçabal  Pedro  Sláma  Jiří  Ulrich  Stanislav 《International Journal of Earth Sciences》2018,107(5):1859-1894

International Journal of Earth Sciences - Early Neoproterozoic metaigneous rocks occur in the central part of the Kaoko–Dom Feliciano–Gariep orogenic system along the coasts of the...  相似文献   

Simulating the effects of quasar structure on parameters from geodetic VLBI   总被引：1，自引：1，他引：0  

Stanislav S. Shabala  Jamie N. McCallum  Lucia Plank  Johannes Böhm 《Journal of Geodesy》2015,89(9):873-886

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Uncovering the Directional Heterogeneity of an Aggregated Mobile Phone Network     

Tao Pei  Stanislav Sobolevsky  Carlo Ratti  Alexander Amini  Chenghu Zhou 《Transactions in GIS》2014,18(Z1):126-142

The aggregated mobile phone network (AMPN) (i.e. the calling time or numbers are aggregated at every vertex), which records the call volume between different places over time, has been studied extensively to reveal the mobility patterns of residents, etc. Nevertheless, most previous works were implemented based on the non‐directionality of the network model. This simplification may overlook some important characteristics of AMPN. To explore the AMPN as a directional network model, we introduce the concept of directional heterogeneity in the study of AMPN data. The heterogeneity is twofold: (1) the imbalance of vertex (difference between outgoing and incoming calls of the vertex); and (2) the reciprocity of each edge (difference between the directed weights of the same edge). Taking the data of Singapore as an example, we systematically analyze the directional heterogeneity of AMPN. Our findings include three aspects. First, the AMPN shows as more unbalanced in the night‐time than in the daytime, and its imbalance decreases as vertex granularity increases. Second, the directional heterogeneity varied with locations. Specifically, the residential area is dominated by deficits and others by surpluses. Third, the trajectories of incoming and outgoing calls follow a similar geographical pattern (i.e. southeast‐north‐south‐north‐southeast), indicating the calling behavior and routine mobility of users over time and space.  相似文献   

Synfolding magnetization: detection, testing and geological applications   总被引：1，自引：0，他引：1  

Stanislav V. Shipunov 《Geophysical Journal International》1997,130(2):405-410

A correct method for determining the direction of a synfolding remanence is described, and a new test, which in a number of cases can discriminate between a true synfolding remanence and a remanence that is the sum of pre- and post-folding components, is suggested. It is shown that it is possible to reveal the folding evolution of a local object under an assumption that the acquisition of the synfolding remanence was synchronous over this object.  相似文献   

Crystal field and covalency of octahedral chromium in natural ^[8](Mg_1?xCa_x) ₃^[6] (Al_0.67Cr_0.33)₂Si₃O₁₂ garnets from upper mantle rocks     

Alexej N. Platonov  Klaus Langer  Stanislav S. Matsyuk 《Physics and Chemistry of Minerals》2008,35(6):331-337

In the course of a thorough study of the influences of the second coordination sphere on the crystal field parameters of the 3d ^N -ions and the character of 3d ^N –O bonds in oxygen based minerals, 19 natural Cr³⁺-bearing (Mg,Ca)-garnets from upper mantle rocks were analysed and studied by electronic absorption spectroscopy, EAS. The garnets had compositions with populations of the ^[8] X-sites by 0.881 ± 0.053 (Ca + Mg) and changing Ca-fractions in the range 0.020 ≤ w _Ca[8] ≤ 0.745, while the ^[6] Y-site fraction was constant with x _Cr³⁺ _[6] = 0.335 ± 0.023. The garnets had colours from deeply violet-red for low Ca-contents (up to x _Ca = 0.28), grey with 0.28 ≤ x _Ca ≤ 0.4 and green with 0.4 ≤ x _Ca. The crystal field parameter of octahedral Cr³⁺ 10Dq decreases strongly on increasing Ca-fraction from 17,850 cm⁻¹ at x _Ca[8] = 0.020 to 16,580 cm⁻¹ at x _Ca[8] = 0.745. The data could be fit with two model which do statistically not differ: (1) two linear functions with a discontinuity close to x _Ca[8] ≈ 0.3, (2) one continuous second order function, The behaviour of the crystal field parameter 10Dq and band widths on changing Ca-contents favour the first model, which is interpreted tentatively by different influences of Ca in the structure above and below x _Ca[8] ≈ 0.3. The covalency of the Cr–O bond as reflected in the behaviour of the nephelauxetic ratio decreases on increasing Ca-contents.  相似文献   

Insoluble portion of dust fallout on snow and its composition in prague     

František Anýz  Rudolf Přibil  Reviewer S. Brandejs 《Studia Geophysica et Geodaetica》1974,18(2):191-198

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Equation of radiation balance of the earth     

Jan Bednář  Stanislav Brandejs  Reviewer Jaroslav Pícha 《Studia Geophysica et Geodaetica》1976,20(3):295-300

Summary The equation of the planetary radiation balance of the Earth is derived and discussed. The changes of the temperature of the Earth due to the change in the cloud cover, the cloud albedo and the Earth's surface albedo are analysed in detail.  相似文献