Phase relations governing the derivation of alkaline basaltic magmas from primary magmas at high pressures     

Sven Maaløe  Tom Svane Petersen 《Lithos》1976,9(3):243-252

A comparison between the variation trend of alkaline basaltic magmas within the CaO-MgO-Al₂O₃-SiO₂ system and experimentally estimated phase relations for this system at high pressures, suggests an olivine reaction relationship, which may explain the transition from primary magmas in equilibrium with olivine to alkaline basaltic magmas in which olivine does not form at high pressures. This reaction relationship is considered to be due to a transition from positive to negative crystallization with respect to olivine along the four phase curve where olivine, diopside, pyrope garnet and liquid are initially in equilibrium. The bimineralic, eclogitic character of alkaline basaltic compositions at high pressures is interpreted as being due to the presence of a thermal minimum on the three phase surface, where dioside and pyrope garnet are in equilibrium with liquid.  相似文献   

The join grossularite-calcite through the system CaO—Al₂O₃—SiO₂—CO₂ at 30 kilobars: Crystallization range of silicates and carbonates on the liquidus     

Sven Maaløe  P.J. Wyllie 《Earth and Planetary Science Letters》1975,28(2):205-208

At 30 kbar, calcite melts congruently at 1615°C, and grossularite melts incongruently to liquid + gehlenite (tentative identification) at 1535°C. The assemblage calcite + grossularite melts at 1450°C to produce liquid + vapor, with piercing point at about 49 wt.% CaCO₃. Vapor phase is present in all hypersolidus phase fields except for those with less than about 7% CaCO₃ or 8% Ca₃Al₂Si₃O₁₂. These results, together with known liquidus data for CaO—SiO₂—CO₂ and inferred results for CaO—Al₂O₃—CO₂ and Al₂O₃—SiO₂—CO₂, permit construction of the position of the CO₂- saturated liquidus surface in the quaternary system, and estimation of the positions of liquidus field boundaries separating some of the primary crystallization fields on this surface. The field of calcite is separated from those for grossularite and quartz by a field boundary with about 50% dissolved CaCO₃. Crystallization paths of silicate liquids in the range Ca₂SiO₄—Ca₃Al₂Si₃O₁₂—SiO₂, with some dissolved CO₂, will terminate at a quaternary eutectic on this field boundary, with the precipitation of calcite together with grossularite and quartz, at a temperature below 1450°C. Addition of Al₂O₃ to CaO—SiO₂—CO₂ in amounts sufficient to stabilize garnet thus causes little change in the general liquidus pattern as far as carbonates and silicates are concerned. With addition of MgO, we anticipate that silicate liquids with dissolved CO₂ will also follow liquidus paths to fields for the precipitation of carbonates; we conclude that similar paths link kimberlite and some carnbonatite magmas.  相似文献   

Water content of a granite magma deduced from the sequence of crystallization determined experimentally with water-undersaturated conditions   总被引：2，自引：0，他引：2  

Sven Maaløe  Peter J. Wyllie 《Contributions to Mineralogy and Petrology》1975,52(3):175-191

The sequence of crystallization in a biotite-granite from the Bohus batholith of Norway and Sweden, deduced from its texture, was magnetite, plagioclase, microcline, quartz, and finally biotite. Several sequences of crystallization were determined experimentally at 2 kb in the presence of varying only for H₂O contents below 1.2% by weight. The rock was fused to a homogeneous glass, and each experiment included samples of finely crushed rock and glass. The samples were reacted in Ag-Pd capsules with measured H₂O content in coldseal pressure vessels with NNO buffer. With excess H₂O (more than 6.5%) the crystallization interval extends from 865° C to 705° C. In the H₂O-deficient region, the solidus temperature remains unchanged as long as a trace of vapor is present, but the liquidus temperature increases as H₂O content decreases; with 0.8 % H₂O the liquidus temperature is 1125° C, the crystallization interval is 420° C, and a separate aqueous vapor phase is evolved only a few degrees above the solidus at 705° C. The biotite phase boundary increases slightly from 845° C with excess H₂O to 875° C with 1% H₂O, and it intersects the steep phase boundaries for quartz and feldspars; the sequence of crystallization changes at each intersection point. Similar diagrams at various pressures for related rock compositions involving muscovite, biotite and amphibole will provide grids useful in defining limits for the water content of granitic and dioritic magmas. Applications are considered for the Bohus batholith, other granitic rocks, and rhyolites. The Bohus magma could have been formed by crustal anatexis as a mobile assemblage of H₂O-undersaturated liquid and residual crystals with initial total H₂O content less than 1.2%, or it could have been derived by fractionation of a more basic parent with low H₂O content from mantle or subduction zone, but it could not have been derived from a primary andesite generated from mantle peridotite. We consider it unlikely that the H₂O content of large granitic magma bodies exceeds about 1.5% H₂O; these magmas are H₂O-undersaturated through most of their histories. Uprise and progressive crystallization of magma bodies produces H₂O-saturation around margins and in the upper regions of magma chambers. H₂O-saturated rhyolitic and dacitic magmas with phenocrysts can be tapped from the upper parts of the magma chambers.  相似文献   

The electronic structure and absorption spectrum of MnO 6 9− octahedra in manganian andalusite     

Aldwyn Tang Kai  Sven Larsson  Ulf Hålenius 《Physics and Chemistry of Minerals》1980,6(1):77-84

The energy levels of MnO ₆ ^9? clusters, with D _4h approximated and C _2v actual symmetry of the M ₁ site of Mn³⁺-bearing andalusite, are calculated using the multiple scattering method. The energies of the electronic d-d transition of Mn³⁺ in the clusters with D _4h symmetry are calculated to be 6,000–7,000 cm^?1 (⁵ B _1g → ⁵ A _1g ), ～18,000 cm^?1 (⁵ B _1g → ⁵ B _2g ) and ～19,000 cm^?1 (⁵ B _1g → ⁵ E _g ). Apart from a splitting of the ⁵ E _g -level into two levels separated by 300–350 cm^?1, no significant changes of these transition energies are noted for the corresponding cluster with C _2v symmetry. The calculated transition energies give a good fit to the structure of the optical absorption spectra of Mn³⁺-bearing andalusites and support recent assignments of the major absorption bands observed in these spectra.  相似文献   

Hydrothermal dolomite marbles associated with charnockitic magmatism in the Proterozoic Bamble Shear Belt,south Norway     

Sven Dahlgren  Ron Bogoch  Mordeckai Magaritz  Annie Michard 《Contributions to Mineralogy and Petrology》1993,113(3):394-409

Deformed and metamorphosed dolomite marbles in the Kragerø area of the Bamble Shear Belt occur as lenses within metasupracrustal sequences, as matrix in bodies resembling magmatic breccias, and as veins/dykes cutting amphibolites and metagabbros. A common origin is not evident from the field relationships, but is nevertherless probable due to great geochemical similarities between dolomite from the different occurrences. They are characterized by higher REE, Ni, Co, Cr and Sc, and lower Ba and Sr contents relative to metasedimentary marbles occurring nearby. Sm-Nd isotope data shows that the dolomites are of Sveconorwegian age (1175±37 Ma). The dolomite marbles are very weakly LREE-enriched and display in most cases positive Eu anomalies. Their stable isotope compositions are uniform (¹⁸O=+9.6 to +10.7; ¹³C=-8.5 to-6.2), their initial ⁸⁷Sr/⁸⁶Sr ratios are high (0.706–0.709), whereas their age corrected _Nd varies from +0.7 to-1.5. Geochemically the dolomitic marbles differ considerably from sedimentary or metasedimentary marbles as well as from carbonatites. The Kragerø dolomite marbles represent deformed and metamorphosed hydrothermal veins or vein-complexes deposited in tensional fractures in the deep crust. Although the dolomitic marbles regionally are of minor volume, the dolomite deposition represents a specific and important event in the geological evolution of the Bamble Shear Belt. Their geochemical and isotopic homogeneity on a regional scale suggest that the hydrothermal solutions were supplied from a very large, homogeneous reservoir. Trace elements, stable and radiogenic isotopes, and field and isotopic age relationships are consistent with a deposition from hydrothermal solutions which were exsolved from crystallizing charnockitic intrusions and subsequently interacted with the crust. The parental magma to these intrusions underplated the crust and raised the geotherm of a carbonated ultramafic uppermost mantle, and imposed decarbonation and fluid release. These fluids were channelled into a large degassing zone now found as a deformed, regional zone with hydrothermal dolomite deposits, albitites, apatite-veins and widespread scapolitization. Whether the CO₂-rich fluids, which precipitated the Kragerø dolomites, pervasively infiltrated crustal rocks at a deeper level and caused granulitization is ambiguous, but possible.  相似文献   

Seismic response analysis of adjacent liquid‐storage tanks          下载免费PDF全文

Konstantinos Mykoniou  Christoph Butenweg  Britta Holtschoppen  Sven Klinkel 《地震工程与结构动力学》2016,45(11):1779-1796

A refined substructure technique in the frequency domain is developed, which permits consideration of the interaction effects among adjacent containers through the supporting deformable soil medium. The tank‐liquid systems are represented by means of mechanical models, whereas discrete springs and dashpots stand for the soil beneath the foundations. The proposed model is employed to assess the responses of adjacent circular, cylindrical tanks for harmonic and seismic excitations over wide range of tank proportions and soil conditions. The influence of the number, spatial arrangement of the containers and their distance on the overall system's behavior is addressed. The results indicate that the cross‐interaction effects can substantially alter the impulsive components of response of each individual element in a tank farm. The degree of this impact is primarily controlled by the tank proportions and the proximity of the predominant natural frequencies of the shell‐liquid‐soil systems and the input seismic motion. The group effects should be not a priori disregarded, unless the tanks are founded on shallow soil deposit overlying very stiff material or bedrock. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Spatio‐temporal variability of water and energy fluxes – a case study for a mesoscale catchment in pre‐alpine environment          下载免费PDF全文

Luitpold Hingerl  Harald Kunstmann  Sven Wagner  Matthias Mauder  Jan Bliefernicht  Riccardo Rigon 《水文研究》2016,30(21):3804-3823

Water and energy fluxes at and between the land surface, the subsurface and the atmosphere are inextricably linked over all spatio‐temporal scales. Our research focuses on the joint analysis of both water and energy fluxes in a pre‐alpine catchment (55 km²) in southern Germany, which is part of the Terrestrial Environmental Observatories (TERENO). We use a novel three‐dimensional, physically based and distributed modelling approach to reproduce both observed streamflow as an integral measure for water fluxes and heat flux and soil temperature measurements at an observation location over a period of 2 years. While heat fluxes are often used for comparison of the simulations of one‐dimensional land surface models, they are rarely used for additional validation of physically based and distributed hydrological modelling approaches. The spatio‐temporal variability of the water and energy balance components and their partitioning for dominant land use types of the study region are investigated. The model shows good performance for simulating daily streamflow (Nash–Sutcliffe efficiency > 0.75). Albeit only streamflow measurements are used for calibration, the simulations of hourly heat fluxes and soil temperatures at the observation site also show a good performance, particularly during summer. A limitation of the model is the simulation of temperature‐driven heat fluxes during winter, when the soil is covered by snow. An analysis of the simulated spatial fields reveals heat flux patterns that reflect the distribution of the land use and soil types of the catchment. The water and energy partitioning is characterized by a strong seasonal cycle and shows clear differences between the selected land use types. Copyright © 2016 The Authors Hydrological Processes Published by John Wiley & Sons Ltd.  相似文献   

Modeling and visualizing uncertainties of flood boundary delineation: algorithm for slope and DEM resolution dependencies of 1D hydraulic models   总被引：1，自引：0，他引：1  

Sven Anders Brandt 《Stochastic Environmental Research and Risk Assessment (SERRA)》2016,30(6):1677-1690

As flood inundation risk maps have become a central piece of information for both urban and risk management planning, also a need to assess the accuracies and uncertainties of these maps has emerged. Most maps show the inundation boundaries as crisp lines on visually appealing maps, whereby many planners and decision makers, among others, automatically believe the boundaries are both accurate and reliable. However, as this study shows, probably all such maps, even those that are based on high-resolution digital elevation models (DEMs), have immanent uncertainties which can be directly related to both DEM resolution and the steepness of terrain slopes perpendicular to the river flow direction. Based on a number of degenerated DEMs, covering areas along the Eskilstuna River, Sweden, these uncertainties have been quantified into an empirically-derived disparity distance equation, yielding values of distance between true and modeled inundation boundary location. Using the inundation polygon, the DEM, a value representing the DEM resolution, and the desired level of confidence as inputs in a new-developed algorithm that utilizes the disparity distance equation, the slope and DEM dependent uncertainties can be directly visualized on a map. The implications of this strategy should benefit planning and help reduce high costs of floods where infrastructure, etc., have been placed in flood-prone areas without enough consideration of map uncertainties.  相似文献   

A revised approach to discriminating sediment transport histories in glacigenic sediments in a temperate alpine environment: a case study from Fox Glacier,New Zealand     

Martin S. Brook  Sven Lukas 《地球表面变化过程与地形》2012,37(8):895-900

Clast shape measurements have developed into a standard method for reconstructing the transport histories of sediments in glacial environments. The majority of studies use the ‘RA‐C₄₀’ covariance approach, with some researchers routinely including clasts of varying lithologies within their samples. The corollary is that variable lithological properties may control clast form and roundness, rather than debris‐transport mechanisms. Despite this, the role of lithology on clast shape in glacial environments has rarely been analysed. Furthermore, some studies have reported difficulties in using the RA‐C₄₀ co‐variance plot in discriminating clasts that have undergone subglacial transport, and clasts that have been modified by fluvial activity. Results from a glacierized valley in a temperate alpine setting indicate that detailed analysis of clast shape where samples are of uniform lithology, although time consuming, is a useful tool in the investigation of deposits in glaciated environments. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Development of a generic concept to analyze the accessibility of emergency facilities in critical road infrastructure for disaster scenarios: exemplary application for the 2017 wildfires in Chile and Portugal     

Guth  Johanna  Wursthorn  Sven  Braun  Andreas Ch.  Keller  Sina 《Natural Hazards》2019,97(3):979-999

Natural Hazards - Natural hazards such as earthquakes, floods, or wildfires pose a serious threat to road infrastructure. Especially in emergency situations, the society depends on the road...  相似文献