Synthetic methods of thin section petrography, scanning electron microscope, electron microprobe, energy spectrum analysis, cathodoluminescence, isotopic analysis and temperature measuring for fluid inclusions were used in analyzing sandstone samples collected from the Zhiluo Formation in order to fully understand the diagenesis evolution and the mineralizing response as well as the genesis of the uranium-bearing sandstone in Dongsheng area. The result shows that (1) the sandstone include lithic silicarenite, feldspathic litharenite and litharenite; (2) the authigenic minerals include clay minerals, carbonate minerals, siliceous and ferric minerals; (3) the physical property of sandstone is obviously controlled by diagenesis; and (4) the sandstone with favorable physical property is propitious to migration and storage of ore-forming fluid, and finally, forming the ore deposit. The sandstone of the Zhiluo Formation had undergone the early diagenetic stage (periods A and B) and the epidiagenetic stage. The evolution of diagenetic environment is in the order of acidic oxidation, alkalescent deoxidization, acidity to transitional environment of oxidation-deoxidization and acidity-alkalescence. The uranium exists in forms of pre-enrichment uranyl ion, active uranyl ion, dispersive adsorptive uranium and uranium mineral, respectively. In addition, the authors also hold that the formation of the sandstone-type uranium is not only related to the oxidation-deoxidization environment, but also closely related to the acidic-alkaline transitional environment, which are propitious to uranium mineralization in sandstone.
A new six-layer world ocean general circulation model based on the primitive system of equations is described in detail and its performance in the case of a homogeneous ocean is described. These test integrations show that the model is capable of reproducing the observed mean barotropic or vertically-integrated transport, as well as the seasonal variability of the major ocean gyres. The surface currents, however, are dominated by the Ekman transport, and such non-linear features as the western boundary currents and the equatorial countercurrents are poorly represented. The abyssal boundary countercurrents are also absent due to the lack of thermohaline forcing. The most conspicuous effect of the bottom topography on a homogeneous ocean is seen in the Southern ocean where the calculated Antarctic circumpolar transport through the Drake passage ( ≈ 10 Sv, with bathymetry included) greatly underestimates the observed transport (≈ 100 Sv). 相似文献
Although not well understood scientifically, integrated and diversified aquaculture-agriculture systems have a history of some two millennia in parts of South and Southeast Asia. With the extremely limited farm area and scanty resources available to the typical small-scale farmer of these regions, integrated agro-ecosystems, based on generations of empirical knowledge, provide a balanced diet and often a small marketable surplus for poor rural households, while continuously recycling nutrients and energy through the system, producing little waste, and maintaining a local ecological balance. Despite the few scientific data available on such systems, they are being widely advocated for use in developing countries with no prior experience of integrated farming.This paper (paper I) describes the environmental context and provides an overview of the mulberry dike-polycultural carp pond resource system of Leliu Commune, in the Zhujiang Delta of the People's Republic of China, where complex and highly productive integrated farming systems are operated on a geographical and economic scale unmatched elsewhere. Subsequent papers will focus on the human ecology of the dike-pond system, the ecological basis for system integration, and the results and implications of experiments and trials for increasing the productivity of and the economic rate of return from the system. 相似文献
At Beijing Observatory both astrometric and gravimetric observations are available to study the non-tidal variations in the deflections of the vertical (or non-tidal plumbline variations, PLVs). From repeated gravimetric observations performed in a network around the observatory, the PLVs at Beijing Observatory during the period 1987.0–1996.0 have been calculated. After comparison with the observational residuals (which also contain the PLV components) of the photoelectric astrolabe located at the observatory, the accuracy of the obtained PLV results has been examined. It is shown that, due to the asymmetry of the gravimetric network, the qualities of the two different PLV components are not equal. The longitude component of the PLV at Beijing has been determined successfully, to be of the order of 0.05, with a contribution of about 0.02 in the inter-annual time scale. The result for the latitude PLV component is not good enough to draw a conclusion. Although both techniques are able to measure the PLV, the result of the determination depends very much on the availability of observational data. 相似文献