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On the pseudobinary join CaO:3MgO:Al2O3:2SiO2:xH2OCaO:1.25MgO:2.75 Al2O3: 0.25SiO2:xH2O clintonite mixed crystals Ca(Mg1+ xAl2 x) (Al4 xSixO10)(OH)2 with x rangingfrom 0.6 to 1.4 occur in the temperature range 600830?C, 2 kb fluid pressure. On the MgSirich side clintonites coexistwith chlorite, forsterite, diopside, and calcite (due to smallamounts of CO2 in the gas phase) and, at lower temperatures,also with idocrase, hydrogrossularite, and aluminous serpentine.Decomposition of clintonite over a divariant temperature rangeoccurs above 830 ?C, 2 kb; clintonite-free subsolidus assemblagescomprising three or four solid phases are formed in the temperatureranges 890 ?1120 ?C. The subsolidus assemblages can berepresented in a polyhedron defined by the corners forsterite,diopside, melilite, spinel, anorthite, corundum, and calciumdialuminate. Above 1120 ?C partial melting occurs. The upper thermal stability limits of three selected compositionshave been reversed in the P-T range 0.520 kb and 7301050 ?C, respectively. Below some 4 kb breakdown is dueto the divariant reactions: (1)Ca(Mg2.25Al0.75)(Al2.75)(Si1.25O10)(OH)2 spinel+diopsidess+forsterite+clintonitess+vapor, (2)Ca(Mg2Al)(Al3SiO10)(OH)2 spinelx002B;melilitess+anorthite+clintonitess+vapor, (3)Ca(Mg1.75Al1.25)(Al3.25)(Si0.75O10)(OH)2 spinel+melilitess+corundum+clintonitess+vapor, At the terminations of the divariant temperature ranges (1)melilitess, (2) diopsidess, and (3) anorthite enter those assemblagesand clintonitess disappears completely. The reactions can berepresented by the following equations (1)log,H2O = 10.28798113/T+0.0856(P1)/T, (2)log = 9.58527325/T+0.0794(P1)/T, (3)log = 7.83585250/T+0.077(P1)/T, with P expressed in bars and Tin ?K. Above 4 kb the upper thermalstability limit of clintonite is defined by incongruent melting,with grossularite participating at pressures above 9 kb. Thesecurves exhibit a very steep, probably even negative slope inthe P-T diagram. There is a close correspondence between natural clintonite-bearingassemblages and thosefound experimentally. The rarity of clintonitein nature is not due to special conditions of pressure and temperaturebut rather due to special bulk compositions of the rocks. 相似文献
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Karl E. SEIFERT 《Geostandards and Geoanalytical Research》1984,8(1):35-38
Silicate rock standards AN-G, BHVO-1, QLO-1, RGM-1, SDC-1 and STM-1 have been analyzed for 7 REE (La, Ce, Sm, Eu, Tb, Yb and Lu), Na2 O, FeOt , Sc, Co, Cr, Ta, Hf and Th by instrumental neutron activation analysis. The mean values are compared to those from other studies reported in the literature. 相似文献
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The harp seal ( Phoca groenlandica ) population of the Barents and White Seas has probably decreased from about one million individuals to half this size the last few years. Energy requirements of the population have been estimated by use of the simulation model SEAERG. In this model the energy requirements of an individual seal from each age group is multiplied with the group size and summed to provide the requirements of the population. In addition to population size and age structure the total food and energy requirement is sensitive to individual activity levels as well as metabolic levels and other specified physiological functions. The interactions between the seal population and fisheries depends on the caloric density of the prey species which varies with season and location. Realistic simulations of interactions between seals and fisheries require more information about spatial and temporal variations in the prey selection of harp seals than is available today.
Present estimates indicate average maintenance requirements of about 13,600 and ll,150kcal/day for adult female and male harp seals respectively. The high value for the females is due to the costs of pregnancy and lactation. With a mean energy density of prey of 1500 kcal/kg, the corresponding food consumption is 9 kg/day for females and 7.4 kg/day for males. 相似文献
Present estimates indicate average maintenance requirements of about 13,600 and ll,150kcal/day for adult female and male harp seals respectively. The high value for the females is due to the costs of pregnancy and lactation. With a mean energy density of prey of 1500 kcal/kg, the corresponding food consumption is 9 kg/day for females and 7.4 kg/day for males. 相似文献
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PIM DE KLERK NORMAN DONNER HANS JOOSTEN NIKOLAY S. KARPOV MERTEN MINKE NINA SEIFERT MARTIN THEUERKAUF 《Boreas: An International Journal of Quaternary Research》2009,38(1):39-58
Fine-scaled distribution patterns of vegetation and palynomorphs in a polygon mire in NE Siberia were studied in 31 × 31 plots of 1 m2 (vegetation) and along a transect at intervals of 1 m (palynomorphs). Pollen and non-pollen-palynomorph contents clearly reflect differences between polygon ridges and centres. For most single pollen types, however, no unambiguous relation with actual plant abundances and distribution exists. High pollen values are restricted to the immediate vicinity of the pollen sources, which is attributed to the low height of the vegetation. For several plant taxa, high pollen values were found to be restricted to particular plant specimens in the population. High values of pollen ascribed to taxa currently absent at the relevant plot show that the sampled mosses contain a pollen signal of several years. Betula exilis produces two morphologically clearly distinct pollen types. The distribution of selected non-pollen palynomorphs correlates to microrelief, moisture regime and/or trophic conditions. The study shows that single palaeo-sections from arctic peatlands should not be over-interpreted with respect to their palaeoecological value. Local vegetation types and site conditions, however, can be accurately reconstructed from the total assemblages and from combined occurrences of specific palynomorph types. 相似文献
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Subsolidus phase relations have been determined in the systemsSiO2-Cr-0 and MgO-SiO2-Cr-O in equilibrium with metallic Cr,at 11001500C and 0288 kbar. There are no ternaryphases in the SiO2-Cr-O system at these conditions, ie. onlythe assemblage eskolaite + Cr-metal + SiO2 is found. However,in the MgO-containing system, extensive substitution of Cr2+for Mg is observed in (Mg,Cr2+)2SiO4 olivine, (Mg,Cr2+)2Si2O6pyroxene, and (Mg,Cr2+)Cr3+204 spinel. Cr 3+ levels in olivineand pyroxene are below detection limits. The pyroxene is orthorhombicat monoclinic at higher . The structure of the spinels becomestetragonally distorted at is limited by the breakdown of olivine to pyroxene + spinel+ metal. This maximum amount increases strongly with increasingtemperature, reaching >0.2 at 1500C and 48 kbar. Increasing pressure reduces the maximum. Increasing temperature also increases the maximum amounts of Cr2+ which substitute intopyroxene and spinel, indicating that end-member Cr2Si206 andCr3O4 may become stable above 1650C if melting does not intervene.Powder X-ray diffraction analysis of selected runs has beenused to extract molar volumes of the Mg-Cr2+ solid solutionsas a function of composition, which may be extrapolated to predictmolar volumes for Cr2SiO4 (olivine), Cr2Si2O6 (ortho- and clino-pyroxene)and Cr2O4 (cubic spinel) of 477, 680 and 449 cm3, respectively.The experimental data have been fitted to a thermodynamic model,including free energies of formation for end member Cr2SiO4,Cr2Si2O6 and Cr3O4. This model is then used to predict the amountsof Cr2+ which can be expected in olivine in equilibrium withCr-bearing spinel as a function of T, P and fo2. This amountincreases strongly with temperature along standard T-fo2 buffercurves, and is sufficient to explain the observed high Cr contentsof olivine from komatiites and diamond inclusions at reasonableterrestrial fo, values. The lower fo2 of the lunar environmentresults in significant Cr2+ in olivine being stable to muchlower temperatures. The tendency for the oxidation state ofCr, and hence its geochemical properties, to change with temperaturerelative to other redox reactions makes it a potentially usefulmonitor of the temperatures of uppermantle processes, and isa significant factor in the differing styles of igneous differentiationin the Earth and Moon.
Corresponding author 相似文献
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The equilibrium temperatures of the reaction muscovite+chlorite+quartz= cordierite+phlogopite+H2O (1) in the pure system K2OMgOAl2O2SiO2H2Owere found to be 495±10°C at 1 kb PH2O; 525±10°Cat 2 kb; 610±15°C at 5 kb; 635±10°C at6 kb. From intersection of this curve with the lower temperaturestability limit of cordierite close to 645°C, 6.5 kb PH2O,a reaction cordieritc+muscovite = phlogopite+aluminum silicate+quartz+H2O(2) is generated which has a negative slope and passes throughthe points 645°C, 6.5 kb PH2O and 700°C, 5 kb PH2O.On the high-pressure side of this reaction curve cordieriteis restricted to K2Opoor bulk compositions. Application of the experimentally determined phase relationsto more complex natural pelitic rocks suggests that reaction(1) represents maximum temperatures for the disappearance ofchlorite from pelitic assemblages containing muscovite and quartz,whereas reaction (2) gives maximum water pressures for the disappearanceof cordierite from these rocks. 相似文献
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