Survivality and Impaired Growth in Arsenic Treated Fingerlings of Channa punctatus,a Fresh Water Murrel

The LC₅₀-values of As³⁺-compounds for Channa punctatus are determined for a 48-h exposure to 19.4 (18.02… 21.3) mg/1 and for a 96-h exposure to 14.3 (13.06… 16.80) mg/1. At a long-time exposure to 7.0 mg/1 As³⁺, during the first seven days there does not occur any change of growth, then the growth in length and the increase in weight decreased by 6.6 and 11.7%, respectively, till the 31st day. At the same time, the RNA content of the muscle decreased by 11.5% to 966.7 μg/g fresh weight and the protein content decreased by 12.5 % to 95.39 mg/g fresh weight.     

Proterozoic deformation of the East Saharan Craton in Southeast Libya, South Egypt and North Sudan

The basement areas in Southeast Libya, South Egypt and North Sudan, west of the Nile, between Gebel Uweinat and the Bayuda Desert, are part of an approximately 1000-km-wide, complexly folded, polymetamorphic zone with a regional N-NNE-NE-ENE trend of foliation and fold axis. Since this belt extends southwestward into the area of Zalingei in the southern Darfur block (West Sudan), it is named the Northern Zalingei fold zone. Sr and Nd isotopic studies suggest that this zone is older than Pan-African and further indicate that, apart from Archean rocks in the Gebel Uweinat area, this belt is of Early-Middle Proterozoic age. An Early-Middle Proterozoic three-stage deformational and anatectic event established the present-day fold and fault geometry in the western parts of this zone in the Gebel Uweinat—Gebel Kamil area. The Pan-African tectono-thermal episode was most effective in the eastern part of the belt, near the boundary with the Nubian Shield volcano-sedimentary-ophiolite-granitoid assemblages. It caused migmatization, granite emplacement, mylonitization and large-scale wrench faulting which was related to Late Proterozoic accretionary and collisional events of the Arabian-Nubian Shield with the margin of the East Saharan Craton.     

Decomposition of fayalite (Fe2SiO4) in an oxygen potential gradient at 1,418 K

The decomposition of fayalite (Fe₂SiO₄) in oxygen potential gradients is studied at T=1,418 K. The compound will be decomposed into its component oxides wüstite, Fe_1?δO, and silica, SiO₂, by the simultaneous action of two different oxygen partial pressures, exceeding a critical ratio, despite the fact that fayalite is stable at both the lower and the higher oxygen potential. A quantitative analysis of the decomposition process caused by defect fluxes within the bulk Fe₂SiO₄ is given.     

The western desert — an example for geodetic problems in arid areas

In this paper some methodical aspects concerning the construction of an accurate geodetic network in arid areas and the connection of the new points to an existing network are discussed. In this context special attention is rapid on the determination of the station heights above the geoid. For the Western Desert in Egypt, which can be regarded as an example of an arid, geodetically underdeveloped region, an observational program is outlined that combines Doppler-measurements with an astrogravimetric-levelling.     

Li,Pb and Tl abundances in the K-alkaline rocks from the Middle Latina Valley volcanoes (southern Latium,Italy) and their petrological significance

Li, Pb and Tl contents of 15 primitive lava samples from the Middle Latina Valley volcanoes (southern Latium, Italy) are higher in the high-K than in the K-Series rocks, the enrichment factors roughly following the increase of the ionic size of the elements.The abundances in both series are higher than those of typical alkali basalts from oceanic environments, but similar to those of granitoid rocks. Such anomalous features may be explained as due to either crustal contamination of the parental magmas or derivation of these latter from a lithophile-enriched mantle region due to metasomatism by a lower crust-derived fluid. In both hypotheses, however, a larger involvement of crustal materials is suggested for the HKS rocks.Comparison of Li, Pb and Tl abundances in the primitive rocks of the Middle Latina Valley and Roccamonfina volcanoes shows that, unlike the KS rocks from the two districts show comparable levels and probably originated under similar conditions, the HKS rocks from the Middle Latina Valley are enriched in Li, Pb and Tl relative to their analogues from Roccamonfina. This suggests either a higher involvement of crustal materials in their genesis, or an evolution at shallower depth in the crust.     

Subophitic lithologies in KREEP-rich poikilitic impact melt rocks from Cayley Plains,Apollo 16 — remnants of a volcanic highland crust?

KREEP-rich poikilitic impact melt rocks 65777,11, 65015,88, and 62235,66 are the only mafic impact melt rocks from Cayley Plains stations, Apollo 16, from which areas of subophitic texture can be reported.The bulk chemistry of these unique subophitic areas and the surrounding poikilitic matrices, as well as mineral compositions (olivine, plagioclase, pyroxene, Fe-Ni metal) were determined by electron microprobe analysis. All subophitic areas could be undoubtedly identified as impact melt rockclasts. Inclusion 65777,11 II is of uniquely KREEP-rich composition, 62235,66 II can be classified as anorthositic. Therefore our attempt to identify pristine volcanic basement rocks of the Cayley regions among these inclusions of basaltic texture failed.However, the absence of pristine volcanic target rock fragments and the existence of KREEP-rich and anorthositic impact melt clasts in KREEP-rich impact melt rocks from Cayley Plains favors the theory that the Cayley Plains formation is part of the ejecta blanket from a large basin-type impact crater (Imbrium?), which is underlain by anorthositic material (Nectaris ejecta?), and has been reworked by local impacts in post-Imbrian times.     

Heat transport by variable viscosity convection and implications for the Earth's thermal evolution

The case is presented that the efficiency of variable viscosity convection in the Earth's mantle to remove heat may depend only very weakly on the internal viscosity or temperature. An extensive numerical study of the heat transport by 2-D steady state convection with free boundaries and temperature dependent viscosity was carried out. The range of Rayleigh numbers (Ra) is 10⁴?10⁷ and the viscosity contrast goes up to 250000. Although an absolute or relative maximum of the Nusselt number (Nu) is obtained at long wavelength in a certain parameter range, at sufficiently high Rayleigh number optimal heat transport is achieved by an aspect ratio close to or below one. The results for convection in a square box are presented in several ways. With the viscosity ratio fixed and the Rayleigh number defined with the viscosity at the mean of top and bottom temperature the increase of Nu with Ra is characterized by a logarithmic gradient β = ?ln(Nu)/? ln(Ra) in the range of 0.23–0.36, similar to constant viscosity convection. More appropriate for a cooling planetary body is a parameterization where the Rayleigh number is defined with the viscosity at the actual average temperature and the surface viscosity is fixed rather than the viscosity ratio. Now the logarithmic gradient β falls below 0.10 when the viscosity ratio exceeds 250, and the velocity of the surface layer becomes almost independent of Ra. In an end-member model for the Earth's thermal evolution it is assumed that the Nusselt number becomes virtually constant at high Rayleigh number. In the context of whole mantle convection this would imply that the present thermal state is still affected by the initial temperature, that only 25–50% of the present-day heat loss is balanced by radiogenic heat production, and the plate velocities were about the same during most of the Earth's history.