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51.
Phosphorus solubility mechanisms in haplogranitic aluminosilicate glass and melt: effect of temperature and aluminum content 总被引:1,自引:0,他引:1
Bjorn O. Mysen 《Contributions to Mineralogy and Petrology》1998,133(1-2):38-50
The solubility behavior of phosphorus in glasses and melts in the system Na2O-Al2O3-SiO2-P2O5 has been examined as a function of temperature and Al2O3 content with microRaman spectroscopy. The Al2O3 was added (2, 4, 5, 6, and 8 mol% Al2O3) to melts with 80 mol% SiO2 and ∼2 mol% P2O5. The compositions range from peralkaline, via meta-aluminous to peraluminous. Raman spectra were obtained of both the phosphorus-free
and phosphorous-bearing glasses and melts between 25 and 1218 °C. The Raman spectrum of Al-free, P-bearing glass exhibits
a characteristic strong band near 940 cm−1 assigned to P=O stretching in orthophosphate complexes together with a weaker band near 1000 cm−1 assigned P2O7 complexes. With increasing Al content, the proportion of P2O7 initially increases relative to PO4 and is joined by AlPO4 complexes which exhibit a characteristic P-O stretch mode slightly above 1100 cm−1. The latter complex appears to dominate in meta-aluminosilicate glass and is the only phosphate complex in peraluminous glasses.
When P-bearing peralkaline silicate and aluminosilicate glasses are transformed to supercooled melts, there is a rapid decrease
in PO4/P2O7 so that in the molten state, PO4 units are barely discernible. The P2O7/AlPO4 abundance ratio in peralkaline compositions increases with increasing temperature. This decrease in PO4/P2O7 with increasing temperature results in depolymerization of the silicate melts. Dissolved P2O5 in peraluminous glass and melts forms AlPO4 complexes only. This solution mechanism has no discernible influence on the aluminosilicate melt structure. There is no effect
of temperature on this solution mechanism.
Received: 7 October 1997 / Accepted: 11 May 1998 相似文献
52.
Sandrine Bony Bjorn Stevens Felix Ament Sebastien Bigorre Patrick Chazette Susanne Crewell Julien Delanoë Kerry Emanuel David Farrell Cyrille Flamant Silke Gross Lutz Hirsch Johannes Karstensen Bernhard Mayer Louise Nuijens James H. RuppertJr. Irina Sandu Pier Siebesma Sabrina Speich Frédéric Szczap Julien Totems Raphaela Vogel Manfred Wendisch Martin Wirth 《Surveys in Geophysics》2017,38(6):1529-1568
Trade-wind cumuli constitute the cloud type with the highest frequency of occurrence on Earth, and it has been shown that their sensitivity to changing environmental conditions will critically influence the magnitude and pace of future global warming. Research over the last decade has pointed out the importance of the interplay between clouds, convection and circulation in controling this sensitivity. Numerical models represent this interplay in diverse ways, which translates into different responses of trade-cumuli to climate perturbations. Climate models predict that the area covered by shallow cumuli at cloud base is very sensitive to changes in environmental conditions, while process models suggest the opposite. To understand and resolve this contradiction, we propose to organize a field campaign aimed at quantifying the physical properties of trade-cumuli (e.g., cloud fraction and water content) as a function of the large-scale environment. Beyond a better understanding of clouds-circulation coupling processes, the campaign will provide a reference data set that may be used as a benchmark for advancing the modelling and the satellite remote sensing of clouds and circulation. It will also be an opportunity for complementary investigations such as evaluating model convective parameterizations or studying the role of ocean mesoscale eddies in air–sea interactions and convective organization. 相似文献
53.
54.
Bjorn O. Mysen 《Geochimica et cosmochimica acta》2007,71(22):5500-5513
The influence on olivine/melt transition metal (Mn, Co, Ni) partitioning of substitution in the tetrahedral network of silicate melt structure has been examined at ambient pressure in the 1450-1550 °C temperature range. Experiments were conducted in the systems NaAlSiO4-Mg2SiO4- SiO2 and CaAl2Si2O8-Mg2SiO4-SiO2 with about 1 wt% each of MnO, CoO, and NiO added. These compositions were used to evaluate how, in silicate melts, substitution and ionization potential of charge-balancing cations affect activity-composition relations in silicate melts and mineral/melt partitioning.The exchange equilibrium coefficient, , is a positive and linear function of melt Al/(Al + Si) at constant degree of melt polymerization, NBO/T. The is negatively correlated with the ionic radius, r, of the M-cation and also with the ionization potential (Z/r2, Z = electrical charge) of the cation that serves to charge-balance Al3+ in tetrahedral coordination in the melts. The activity coefficient ratio, (γM/γMg)melt, is therefore similarly correlated.These melt composition relationships are governed by the distribution of Al3+ among coexisting Q-species in the peralkaline (depolymerized) melts coexisting with olivine. This distribution controls Q-speciation abundance, which, in turn, controls (γM/γMg)melt and . The relations between melt structure and olivine/melt partitioning behavior lead to the suggestion that in natural magmatic systems mineral/melt partition coefficients are more dependent on melt composition and, therefore, melt structure the more alkali-rich and the more felsic the melt. Moreover, mineral/melt partition coefficients are more sensitive to melt composition the more highly charged or the smaller the ionic radius of the cation of interest. 相似文献
55.
56.
Thorsten Mauritsen Rune G. Graversen Daniel Klocke Peter L. Langen Bjorn Stevens Lorenzo Tomassini 《Climate Dynamics》2013,41(9-10):2539-2554
Earth’s climate sensitivity to radiative forcing induced by a doubling of the atmospheric CO2 is determined by feedback mechanisms, including changes in atmospheric water vapor, clouds and surface albedo, that act to either amplify or dampen the response. The climate system is frequently interpreted in terms of a simple energy balance model, in which it is assumed that individual feedback mechanisms are additive and act independently. Here we test these assumptions by systematically controlling, or locking, the radiative feedbacks in a state-of-the-art climate model. The method is shown to yield a near-perfect decomposition of change into partial temperature contributions pertaining to forcing and each of the feedbacks. In the studied model water vapor feedback stands for about half the temperature change, CO2-forcing about one third, while cloud and surface albedo feedback contributions are relatively small. We find a close correspondence between forcing, feedback and partial surface temperature response for the water vapor and surface albedo feedbacks, while the cloud feedback is inefficient in inducing surface temperature change. Analysis suggests that cloud-induced warming in the upper tropical troposphere, consistent with rising convective cloud anvils in a warming climate enhances the negative lapse-rate feedback, thereby offsetting some of the warming that would otherwise be attributable to this positive cloud feedback. By subsequently combining feedback mechanisms we find a positive synergy acting between the water vapor feedback and the cloud feedback; that is, the combined cloud and water vapor feedback is greater than the sum of its parts. Negative synergies surround the surface albedo feedback, as associated cloud and water vapor changes dampen the anticipated climate change induced by retreating snow and ice. Our results highlight the importance of treating the coupling between clouds, water vapor and temperature in a deepening troposphere. 相似文献
57.
58.
Water fluxes through the Barents Sea 总被引:14,自引:2,他引:14
59.
Gary J. Whiting Henry N. McKellar Bjorn Kjerfve John D. Spurrier 《Estuarine, Coastal and Shelf Science》1985,21(2):273-286
A sampling and computational approach for estimating nutrient fluxes from a salt marsh ecosystem is presented. Extensive and intensive sampling of tidal velocities, water depths, and nutrient concentrations was made synoptically across three tidal creeks, connecting a 34 km2 South Carolina salt marsh with surrounding coastal waters. An estimate of nutrient exchange over each sampling period is based on measurements over four tidal cycles during a neap and spring tidal regime. The computation of instantaneous fluxes of NO3?NO2?, NH4+, and o-PO24? was based on the cross-multiplication of concentration, velocity, and integrated over the cross-sectional area of each tidal creek. The net flux of nutrients was estimated using a least-squares regression model which included periodic functions simulating tidal and diurnal cycles. This computational approach allows for a rigorous test of the statistical significance of the measured nutrient fluxes and a basis on which interpretations of the ecological significance of the exchange can be made.Tidal patterns in inorganic nutrient concentrations and the corresponding exchanges are presented for a spring time sampling. Nitrate-nitrite was exported consistently from the marsh to the coastal ocean with a mean value of 8.0 kg per tidal cycle for the neap sampling set and 15.6 kg per tidal cycle for the spring set. This corresponded to high concentrations of nitrate-nitrite (0.6 μM) on the ebb tide with low concentrations (0.1 μM) on the flood tide. Ammonia flux was variable and did not portray a consistent tidal concentration pattern. Concentrations ranged from 1 to 6 μM. Ammonia flux was exported to the coastal ocean only during the spring tidal set with a mean value of 114 kg per tidal cycle. Ortho-phosphate was also exported only on the spring tidal set with a mean flux of 40.0 kg per tidal cycle. A tidal concentration pattern of high concentrations (0.6 μM) on the ebb tide and low concentrations (0.05 μM) on the flood was consistent for ortho-phosphate during both neap and spring tidal sets. 相似文献
60.
Samar Amini Roland Roberts Mohammad Raeesi Zaher Hossein Shomali Bjorn Lund Zoya Zarifi 《Journal of Seismology》2018,22(4):815-831
An intraplate earthquake doublet, with 11-min delay between the events, devastated the city of Varzeghan in northwestern Iran on August 11, 2012. The first Mw 6.5 strike-slip earthquake, which occurred after more than 200 years of low seismicity, was followed by an Mw 6.4 oblique thrust event at an epicentral separation of about 6 km. While the first event can be associated with a distinct surface rupture, the absence of a surface fault trace and no clear aftershock signature makes it challenging to identify the fault plane of the second event. We use teleseismic body wave inversion to deduce the slip distribution in the first event. Using both P and SH waves stabilize the inversion and we further constrain the result with the surface rupture extent and the aftershock distribution. The obtained slip pattern shows two distinct slip patches with dissimilar slip directions where aftershocks avoid high-slip areas. Using the estimated slip for the first event, we calculate the induced Coulomb stress change on the nodal planes of the second event and find a preference for higher Coulomb stress on the N-S nodal plane. Assuming a simple slip model for the second event, we estimate the combined Coulomb stress changes from the two events on the focal planes of the largest aftershocks. We find that 90% of the aftershocks show increased Coulomb stress on one of their nodal planes when the N-S plane of the second event is assumed to be the correct fault plane. 相似文献