The major element composition of the upper mantle estimated from the composition of lherzolites     

Sven Maaløe  Ken-ichiro Aoki 《Contributions to Mineralogy and Petrology》1977,63(2):161-173

The compilation of analyses of continental and oceanic spinel Iherzolites show that these two types of Iherzolites have very similar compositions. Their composition range differ from that of African garnet Iherzolites, and the data suggest that the mantle beneath Africa has an anomalous composition. If the composition of the upper mantle may be estimated from that of Iherzolites, the compositions of spinel Iherzolite should form the basis for this estimate. It is suggested that the compositions of spinel Iherzolite represent both undepleted and depleted compositions, and a representative composition for the primitive mantle is proposed on this basis.  相似文献   

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   

Aquifer chemistry of four high-temperature geothermal systems in Iceland     

Stefán Arnórsson  Karl Grönvold  Sven Sigurdsson 《Geochimica et cosmochimica acta》1978,42(5):523-536

The deep water feeding wet-steam wells in four high-temperature geothermal areas in Iceland have highly variable salinity as reflected in the chlorine concentrations which vary from 20 to 19000 ppm. Using available values for equilibrium constants, the activities of 26 chemical species involving the major components of the reservoir water have been calculated and quantitative evaluations of solute/ solute, mineral/solute chemical equilibria in these geothermal systems have been made.The unflashed reservoir water is just saturated with calcite. The saline geothermal waters, which represent heated sea-water, are just saturated with anhydrite, but the dilute waters, which are of meteoric origin, are somewhat undersaturated with this mineral. The fluoride mobility is thought to be limited by an ionic exchange reaction where F^? replaces some of the OH^? in the layered silicates. The pH of the unflashed reservoir water is governed by ionic exchange equilibrium in which all the major cations participitate. At a given temperature it seems likely that the activity of one cation fixes the activities of all the other major cations and hydrogen ion. If this is so and we take all the other chemical equilibria which have been demonstrated to exist for granted, it turns out that the major element composition of the unflashed high-temperature geothermal waters is controlled by two independent variables only. These variables are the temperature and the supply to the water of the incompatible element chlorine, incompatible indicating that this element is not incorporated in the geothermal minerals.  相似文献   

On atmospheric wave generation by the terminator     

Tom Beer 《Planetary and Space Science》1978,26(2):185-188

The dominant response of the terminator is found to be due to the change in thermospheric absorption of solar radiation, and leads to two types of atmospheric waves: (i) a ducted acoustic wave at altitudes below 100 km and (ii) a boundary wave concentrated along the mesopause.  相似文献   

A large-mesh salmon trap: a way of mitigating seal impact on a coastal fishery   总被引：1，自引：2，他引：1  

Lunneryd  Sven Gunnar; Fjalling  Arne; Westerberg  Hakan 《ICES Journal of Marine Science》2003,60(6):1194-1199

  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   

Rainfall Variability in Murang'a District, Kenya: Meteorological Data and Farmers' Perception   总被引：2，自引：0，他引：2  

Mira Ovuka  & Sven Lindqvist 《Geografiska Annaler: Series A, Physical Geography》2000,82(1):107-119

This study examines meteorological data and farmers' perception of rainfall in the Central Highlands of Kenya. Rainfall data from five meteorological stations during the period from 1947 to 1996 were analysed on an annual and a monthly basis. Daily data exist from 1957 and analyses from 1957 to 1996 were done on a daily basis. Discussions were held with 60 farmers about rainfall and its variation. Ten of these farmers were interviewed with a questionnaire about rainfall. Analysing annual precipitation and rain periods gave no clear trends over the study period. Results from analysing the growing seasons for maize, the main annual crop, and periods during which maize plants are sensitive to drought showed decreasing trends in rainfall amounts for the study period. Results from the interviews indicate that most of the farmers think rainfall has decreased over the last 40 years. Farmers'perceptions of rainfall are related to periods when the main food and annual crop require water and not to the periods scientists often analyse, i.e. annual and rain periods. More research and better advice from agricultural extension workers to farmers are necessary to enable this area to sustain itself in sufficient food production if the decreasing trends during the growing seasons and drought-sensitive periods continue.  相似文献