Solubility of carbon dioxide in melts of andesite,tholeiite, and olivine nephelinite composition to 30 kbar pressure     

Bjørn O. Mysen  R. J. Arculus  David H. Eggler 《Contributions to Mineralogy and Petrology》1975,53(4):227-239

Carbon dioxide solubilities in H₂O-free hydrous silicate melts of natural andesite (CA), tholeiite (K 1921), and olivine nephelinite (OM1) compositions have been determined employing carbon-14 beta-track mapping techniques. The CO₂ solubility increases with increasing pressure, temperature, and degree of silica-undersaturation of the silicate melt. At 1650° C, CO₂ solubility in CA increases from 1.48±0.05 wt % at 15 kbar to 1.95±0.03 wt % at 30 kbar. The respective solubilities in OM1 are 3.41±0.08 wt % and 7.11±0.10 wt %. The CO₂ solubility in K1921 is intermediate between those of CA and OM1 compositions. At lower temperatures, the CO₂ contents of these silicate melts are lower, and the pressure dependence of the solubility is less pronounced. The presence of H₂O also affects the CO₂ solubility (20–30% more CO₂ dissolves in hydrous than in H₂O-free silicate melts); the solubility curves pass through an isothermal, isobaric maximum at an intermediate CO₂/(CO₂+H₂O) composition of the volatile phase. Under conditions within the upper mantle where carbonate minerals are not stable and CO₂ and H₂O are present a vapor phase must exist. Because the solubility of CO₂ in silicate melts is lower than that of H₂O, volatiles must fractionate between the melt and vapor during partial melting of peridotite. Initial low-temperature melts will be more H₂O-rich than later high-temperature melts, provided vapor is present during the melting. Published phase equilibrium data indicate that the compositional sequence of melts from peridotite +H₂O+CO₂ parent will be andesite-tholeiite-nephelinite with increasing temperature at a pressure of about 20 kbar. Examples of this sequence may be found in the Lesser Antilles and in the Indonesian Island Arcs.  相似文献   

Limits of solution of trace elements in minerals according to Henry's law: Review of experimental data     

Bjørn O. Mysen 《Geochimica et cosmochimica acta》1978,42(6):871-885

Results of a survey of experimental data on trace element partitioning between crystals and coexisting liquid and between crystals and coexisting aqueous fluid are reported. These studies involve combinations of elements such as Cs, Rb, K, Na, Li, Ba, Sr, Ni and Sm dissolved in minerals such as feldspars, micas, feldspathoids, garnets, pyroxenes, amphibole and olivine. It is shown that the concentration ranges of these elements in minerals with solution behavior according to Henry's law appear to extend to less than 1 wt.% and often to less than 100 ppm of the element in the crystalline phase.The available data indicate that the concentration ranges of solution in minerals according to Henry's law can be positively correlated with the difference of ionic radii between trace element and the host element for which the tracer is assumed to substitute. Furthermore, studies involving crystals and coexisting aqueous fluid have been used to determine whether Henry's law or Raoult's law adequately describes the solution. Based on the assumption that the aqueous fluid solution can be considered ideal, models have been proposed stating that if the difference between the ionic radii of the tracer and the host element in the crystalline phase is less than about 10% (relative to the host element), the solution is ideal (Raoult's law). With larger differences between the ionic radii, there is an excess free energy of mixing, although Henry's law is still obeyed in the concentration ranges where crystalliquid or crystal-fluid partition coefficients are independent of element concentration.  相似文献   

Olivine/melt transition metal partitioning, melt composition, and melt structure—Influence of Al for Si substitution in the tetrahedral network of silicate melts     

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, (γ_M/γ_Mg)^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 (γ_M/γ_Mg)^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   

Fault slip and identification of the second fault plane in the Varzeghan earthquake doublet     

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   

EUREC<Superscript>4</Superscript>A: A Field Campaign to Elucidate the Couplings Between Clouds,Convection and Circulation     

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   

Erratum to: On the equivalence of Kalman filtering and least-squares estimation     

E. Mysen 《Journal of Geodesy》2017,91(4):463-463

  相似文献   

Redox equilibria of iron and silicate melt structure: Implications for olivine/melt element partitioning     

Bjorn O. Mysen 《Geochimica et cosmochimica acta》2006,70(12):3121-3138

Olivine/melt partitioning of ΣFe, Fe²⁺, Mg²⁺, Ca²⁺, Mn²⁺, Co²⁺, and Ni²⁺ has been determined in the systems CaO-MgO-FeO-Fe₂O₃-SiO₂ (FD) and CaO-MgO-FeO-Fe₂O₃-Al₂O₃-SiO₂ (FDA3) as a function of oxygen fugacity (f_O2) at 0.1 MPa pressure. Total iron oxide content of the starting materials was ∼20 wt%. The f_O2 was to used to control the Fe³⁺/ΣFe (ΣFe: total iron) of the melts. The Fe³⁺/ΣFe and structural roles of Fe²⁺ and Fe³⁺ were determined with ⁵⁷Fe resonant absorption Mössbauer spectroscopy. Changes in melt polymerization, NBO/T, as a function of f_O2 was estimated from the Mössbauer data and existing melt structure information. It varies by ∼100% in melts coexisting with olivine in the FDA3 system and by about 300% in the FD system in the Fe³⁺/ΣFe range of the experiments (0.805-0.092). The partition coefficients ( in olivine/wt% in melt) are systematic functions of f_O2 and, therefore, NBO/T of the melt. There is a -minimum in the FDA3 system at NBO/T-values corresponding to intermediate Fe³⁺/ΣFe (0.34-0.44). In the Al-free system, FD, where the NBO/T values of melts range between ∼1 and ∼2.9, the partition coefficients are positively correlated with NBO/T (decreasing Fe³⁺/ΣFe). These relationships are explained by consideration of solution behavior in the melts governed by Qⁿ-unit distribution and structural changes of the divalent cations in the melts (coordination number, complexing with Fe³⁺, and distortion of the polyhedra).  相似文献   

The Atlantic ITCZ bias in CMIP5 models     

Siongco  Angela Cheska  Hohenegger  Cathy  Stevens  Bjorn 《Climate Dynamics》2015,45(5-6):1169-1180

Climate Dynamics - Precipitation over the tropical Atlantic in 24 atmospheric models is analyzed using an object-based approach, which clusters rainy areas in the models as precipitation objects...  相似文献   

Assessment of different metrics for physical climate feedbacks     

Daniel Klocke  Johannes Quaas  Bjorn Stevens 《Climate Dynamics》2013,41(5-6):1173-1185

We quantify the feedbacks from the physical climate system on the radiative forcing for idealized climate simulations using four different methods. The results differ between the methods and differences are largest for the cloud feedback. The spatial and temporal variability of each feedback is used to estimate the averaging scale necessary to satisfy the feedback concept of one constant global mean value. We find that the year-to-year variability, combined with the methodological differences, in estimates of the feedback strength from a single model is comparable to the model-to-model spread in feedback strength of the CMIP3 ensemble. The strongest spatial and temporal variability is in the short-wave component of the cloud feedback. In our simulations, where many sources of natural variability are neglected, long-term averages are necessary to get reliable feedback estimates. Considering the large natural variability and relatively small forcing present in the real world, as compared to the forcing imposed by doubling CO₂ concentrations in the simulations, implies that using observations to constrain feedbacks is a challenging task and requires reliable long-term measurements.  相似文献   

Reduction Rates of Sedimentary Mn and Fe Oxides: An Incubation Experiment with Arctic Ocean Sediments     

C��dric Magen  Alfonso Mucci  Bjorn Sundby 《Aquatic Geochemistry》2011,17(4-5):629-643

To test the hypothesis that manganese- and iron-reducing bacteria in marine sediments respond rapidly to seasonal pulses of fresh organic carbon settling to the sea floor, we amended wet metal oxide?Crich and metal oxide?Cpoor sediments from the Beaufort Sea, Canadian Arctic, with organic carbon in the form of shrimp powder and incubated them at room temperature. Neither Mn nor Fe was released to the aqueous phase from unamended metal oxide?Crich sediment during a 41-day incubation, but both elements were released from sediment aliquots amended with organic carbon. Dissolved Mn appeared in the aqueous phase after a lag period of 2 days or less and reached levels as high as 600 ??mol l^?1 before levelling out. The release of dissolved Mn was accompanied by a decrease in the concentration of solid-phase reducible Mn. Dissolved Fe did not appear until 2 weeks into the incubation and only after the concentration of dissolved Mn had levelled out. For low concentrations of amended organic carbon (0.3%), the kinetics of Mn reduction fit a second-order rate law with a rate constant k = 2 × 10^?3 g ??mol^?1 day^?1, but at intermediate and high organic carbon concentrations (0.7 and 1.3%), the reduction kinetics was better described by a pseudo-first-order rate law with a rate constant k?? = 1.6 × 10^?1 day^?1. A pulse of organic carbon settling to the sea floor can trigger reduction of Mn and Fe oxides within a few days in strongly seasonal sedimentary environments, such as in the Arctic.  相似文献