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441.
Water-saturated and water-undersaturated experiments (a
H2
O = 1.0 and 0.5) were performed in the temperature range 780–1040°C at 2 and 5 kbar in order to determine the upper thermal
stability of phlogopite in granitic melts. Starting compositions were: (A) subaluminous mixtures of 20 wt % synthetic phlogopite
and 80 wt % synthetic anhydrous haplogranitic glass; (B) peraluminous mixtures (normative corundum = 4 %) of 20 wt % synthetic
phlogopite and 80 wt % synthetic anhydrous peraluminous haplogranitic glass. The molar quartz: albite: orthoclase ratio of
the glasses of the 2␣kbar runs was 35:39:26 and that of the 5 kbar runs 30:42:28. In the subaluminous system, phlogopite is
stable up to 820°C at a
H2
O = 1.0 and up to 780°C at a
H2
O = 0.5. At higher temperatures, it is replaced by enstatite. In the peraluminous system phlogopite has a remarkably higher
thermal stability (up to 1000°C at 5 kbar and a
H2
O = 1.0) and there is a temperature interval of 80°C at a
H2
O = 1.0, and 90–100°C at a
H2
O = 0.5 between the first appearance of enstatite and the disappearance of phlogopite. In the peraluminous system, phlogopite
is a solid solution (ss) of phlogopite, muscovite, talc and eastonite components. The crystalline product of the phlogopitess breakdown reaction is an aluminous enstatite. The MgO-content of the melt depends on the normative corundum content of the
starting material and the run temperature. It is independent of pressure. In the subaluminous system, the MgO-content ranges
between 0.05 and 0.3 wt % in the temperature interval 780–880°C at both investigated water activities. The MgO-content of
the peraluminous melts at a
H2
O = 1.0 ranges between 0.4 and 1.7 wt % and at a
H2
O = 0.5 between 0.2 and 1.4 wt % in the temperature range 780–980°C.
Received: 28 August 1995 / Accepted: 6 August 1996 相似文献
442.
443.
Johannes Hendrik Van der Merwe 《GeoJournal》1997,43(2):135-151
A computerised aid to the land use planning process is demonstrated on the urban edge of Cape Town, South Africa. Multi-criteria analysis is performed in the IDRISI GIS package to evaluate development suitability for four land use categories according to appropriately measured and weighted criteria. The four suitability images are then subjected to multi-objective land allocation to demarcate optimum locations for each land use type. The decision-making process entails execution of seven consecutive steps which are discussed in detail and applied in the case study. Technical decisions are rationalised and results displayed. The paper concludes with a call for the development of applications which can incorporate public participation in this type of decision-making process to ensure the wider acceptance of advanced GIS technology as appropriate technology. 相似文献
444.
445.
446.
Die eigenartigen Verwitterungs- und Landschaftsformen des Dikilitaš-Sandsteines in Nordost-Bulgarien
Johannes F. Gellert 《International Journal of Earth Sciences》1932,23(3-4):173-178
Ohne Zusammenfassung 相似文献
447.
Johannes F. Gellert 《International Journal of Earth Sciences》1930,21(4):209-217
Ohne ZusammenfassungAuf der Hauptversammlung der Geologischen Vereinigung in Frankfurt am 5. I. 30 vorgetragen. 相似文献
448.
449.
We determined the monthly and annual riverine freshwater, nitrogen (N) and phosphorus (P) loading into the North Sea from
Belgium, The Netherlands, and Germany for the years 1977–2000. An average of 133 km3 yr−1 of the 309 km3 yr−1 precipitation into the watershed is carried by the rivers into the sea. Total freshwater discharge fluctuates with a strong
6–7 yr periodicity, is strongly correlated with precipitation, and exhibits a slight long-term decrease. The temporal changes
of regional patterns of precipitation lead to changing ratios of annual discharge of the western rivers compared to the eastern
rivers, varying between 2.2 and 3.5. The long-term oscillations in discharge were more pronounced as discharge increased.
The annual means of total and dissolved inorganic N and P loads were estimated to be 722 and 582 kt N yr−1 and 48 and 26 kt P yr−1, respectively. The monthly N loads were much more strongly correlated with discharge, compared to the monthly P loads. Total
N and P as well as dissolved inorganic N also demonstrated a 6–7 yr periodicity. The annual N loads decreased by about 17
kt N yr−1 from 1977 to 2000. The total phosphorus and phosphate loads decreased from about 80 and 50 kt P yr−1 in the 1980s to 25 and 12 kt P yr−1, respectively, in the 1990s. The western rivers contributed the major part of the nutrient loads. The long-term oscillations
in their nutrient loads were much more pronounced, compared to the eastern rivers. The area-specific loading rates estimated
for all rivers are comparable to earlier estimates using shorter data records, smaller sample sizes, and a less complete watershed
monitoring program. The monthly and annual average N:P ratios and their variability increased considerably for individual
rivers during the study interval. These results confirm that the water quality of European continental rivers is strongly
influenced by intense land use. They demonstrate the necessity for using long time series monitoring results to assess change
and evaluate the effects of climate change on the North Sea coastal ecosystems, using ecosystem models on decadal time scales. 相似文献
450.
Admir C. Targino Kevin J. Noone Frank Drewnick Johannes Schneider Radovan Krejci Gustavo Olivares Silke Hings Stephan Borrmann 《Atmospheric Research》2007,86(3-4):225-240
During June and July 2003 the Sources and Origins of Atmospheric Cloud Droplets experiment (SOACED) was carried out on a mountain-top site in central Sweden. The main objective of the experiment was to characterise the microphysical and chemical properties of cloud droplet residuals and interstitial aerosol particles in continental clouds and to understand the processes controlling cloud properties at this location.Interstitial and residual aerosol size distributions, cloud liquid water content and species- and size-resolved aerosol mass concentrations are the main variables employed to address questions pertaining to the cloud droplet number concentration and scavenging efficiency during a stratocumulus cloud event observed on July 28, 2003. In this cloud event, about 56% of the aerosol mass was associated with organic species, whilst SO4 accounted for 23% and NH4 for 14%. NO3 and Cl made up about 7% of the total mass.The partitioning of the aerosol particles between cloud droplets and interstitial air has been studied in terms of their microphysical properties. The scavenging efficiency, defined as the fraction of particles activated into cloud elements compared to the total amount of particles, was investigated as a function of size. The scavenging efficiency curves displayed different shapes during the cloud event, from an S-shaped curve, with low scavenging efficiency in the Aitken mode and larger scavenging efficiency in the accumulation mode, to more unusual shapes where Aitken-mode particles were either solely activated or activated in addition to accumulation-mode particles.This study suggests that alterations of the aerosol chemical composition occurred during the measurement period, changing the hygroscopic nature of the CCN and decreasing their activation diameter. It is also hypothesized that entrainment of drier air aloft may have introduced inhomogeneities in the supersaturation field and modified the S-shaped scavenging curves. 相似文献