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1.
Mineral deposits are unevenly distributed in the Earth's crust, which is closely related to the formation and evolution of the Earth. In the early history of the Earth, controlled by the gravitational contraction and thermal expansion, lighter elements, such as radioactive, halogen-family, rare and rare earth elements and alkali metals, migrated upwards; whereas heavier elements, such as iron-family and platinum-family elements, base metals and noble metals, had a tendency of sinking to the Earth's core, so that the elements iron, nickel, gold and silver are mainly concentrated in the Earth's core. However, during the formation of the stratified structure of the Earth, the existence of temperature, pressure and viscosity differences inside and outside the Earth resulted in vertical material movement manifested mainly by cascaded evolution of mantle plumes in the Earth. The stratifications and vertical movement of the Earth were interdependent and constituted the motive force of the mantle-core movement.  相似文献   

2.
The origin and history of the Earth are manifested as the evolutionary processes of chemistry and physics of its interiors,which can be recognized by deciphering the geochemical signals recorded in minerals and rocks.Deep interiors of the Earth and other rocky planets are under both extreme pressure and temperature,i.e.,approximately 360 gigapascals(GPa)and as high as 7000 K at the center of the Earth.  相似文献   

3.
We describe the earlier unknown, when applied to global tectonics, centrifugal inertial mechanism of lithosphere plate moving under the effect of forces appearing as a result of Earth‘s planetary rotation. The mechanism stated gives an insight into global tectonics of plates with the indirect participation of emanation streams which, in their turn, are the derivatives of centrifugal and inertial forces of planetary motion. The application of this mechanism provides a logical explanation for the regularities of global tectogenesis including the formation of mountain ridges mainly of submeridional and sublatitudinal strike, and also the drift of continental plates from the east to the west and from the south to the north. The mechanism clarifies the significance of the Arctic and the Antarctic Circles as geodynamic barriers.  相似文献   

4.
Geologic time is fundamental to the Earth Sciences, and progress in many disciplines depends critically on our ability to measure time with increasing accuracy and precision. Isotopic geochronology makes use of the decay of radioactive nuclides as a help to quantify the histories of rock, minerals, and other materials. Both accuracy and precision of radioisotopic ages are, at present, limited by those of radioactive decay constants. Modem mass spectrometers can measure isotope ratios with a precision of 10-4 or better. On the other hand, the uncertainties associated with direct half-life determinations are, in most cases, still at the percent level. The present short note briefly summarizes progress and problems that have been encountered during the Working Group‘s activity.  相似文献   

5.
The tried and tested multianvil apparatus has been widely used for high-pressure and high-temperature experimental studies in Earth science. As a result, many important results have been obtained for a better understanding of the components, structure and evolution of the Earth. Due to the strength limitation of materials, the attainable multianvil pressure is generally limited to about 30 GPa (corresponding to about 900 km of the depth in the Earth) when tungsten carbide cubes are adopted as second-stage anvils. Compared with tungsten carbide, the sintered diamond is a much harder material. The sintered diamond cubes were introduced as second-stage anvils in a 6–8 type multianvil apparatus in the 1980s, which largely enhanced the capacity of pressure generation in a large volume press. With the development of material synthesis and processing techniques, a large sintered diamond cube (14 mm) is now available. Recently, maximum attainable pressures reaching higher than 90 GPa (corresponding to about 2700 km of the depth in the Earth) have been generated at room temperature by adopting 14-mm sintered diamond anvils. Using this technique, a few researches have been carried out by the quenched method or combined with synchrotron radiation in situ observation. In this paper we review the properties of sintered diamond and the evolution of pressure generation using sintered diamond anvils. As-yet unsolved problems and perspectives for uses in Earth Science are also discussed.  相似文献   

6.
The Shazi anatase ore deposit in Qinglong, Guizhou Province, is a large-sized anatase deposit that has been recently explored. The characteristics of major oxides in the ore are similar to those of modem laterite weath- ering crust and laterite in the laterite-type gold deposits in the western part of Guizhou Province. Studies on the REE characteristics of basalts and anatase ores in the study region showed that both of them do have extremely strong affinities. There are two groups of trace elements in the ores, i.e., Au-Ag-As-Sb-Hg-Tl association and Sc-TiO2-Cu-Fe-Mn association, reflecting that the formation of anatase ore is related to the formation of siliceous claystone at the early stage of eruption of the Emeishan basaltic magma. The siliceous claystones are the major country rocks for the formation of laterite-type gold ores and anatase ores. In the region anatase ores are rich in Sc and the basalts enriched in Fe, Mn, Ti and Sc are the material source of metallogenesis.  相似文献   

7.
Wetland is the conjunction of lake and terrene where human activities are concentrated. From the viewpoints of material transport and cycling in the terrene-lake system, wetland is the buffer where sand and mud, heavy metals, pollutants and nutrients are tarried. In this paper, we provide a case study based on the temporal and spatial distribution of elements in the Wangling River catchment, a small sub-catchment of Longgan Lake in the middle reaches of the Yangtze River. We have found that wetland can buffer major heavy metals such as Cr, Cu, etc.significantly, but has a little buffer function to some active elements such as Fe and Mn, which are always transported as solutions. Human activities not only influence the distribution of elements, but also weaken the buffer function of wetland. Intensive human activities in the Longgan Lake area in the past 70 years have been recorded in stream, wetland and lake sediments, especially the human activity events such as deforesting and reclaiming on a large scale in 1958 and the 1980‘s. Human activities caused the increase of sedimentation rates since the 1950‘ s, as well as the increase of elements‘ concentrations. The extensive use of fertilizers and pesticides since the 1960‘ s have led to the increase of total P concentrations. Increasing SO2 emission accelerate the process of cation exchange in soil, and enhance the leaching of Mn out of soils. Permanent storing of water causes the soil gleyification that also intensifies the leaching of Mn.These are two major reasons for the obvious increase of manganese concentrations in recent 20 years in Longgan Lake. Intensive human activities since the 1950s‘ have intensified the population in this region and thus destroyed the buffer function of wetland.  相似文献   

8.
陈雄 《地球化学》1984,(3):256-269
Various changes, or geological events, and. their periodicity involved in the evolution of the earth can hardly be explained satisfactorily and completely only in terms of the earth itself. More recently, ever-increasing attention has been paid to the influence of the solar system and the galactic system, even that of the vast cosmic space. This paper intends to discuss the relationship between the earth‘s evolution and the galactic system, based on the revolution of the solar system and other space factors. It is well-known that one period in which the solar system moves around the gtlactic centre is defined as one cosmic year (ca. 220---250m.y.). A good many facts have shown that the periodicity of various changes involved in the evolution of the earth, such as climatic fluctuation, crustal movement, magmatic activity, biological evolution, eustatic movement, elemental synthesis, the reversal of polarity of the earth‘s magnetic field, the variation of the speed of earth‘s rotation, etc. is generally consistent with the concept of cosmic year, which reflects the internal connection between the evolution of the earth and the galactic system. The author has proposed that the revolution of the solar system orbiting around the galactic centre with an ellipticy of 0.07--0.1, the speed of earth‘s rotation, and the annual average distance between the sun and the earth, as well as some space physical fields, such as magnetic field,radiation field, etc. are all characterized by cosmic year periodic variatioons. Under the influence of these cosmic factors, various changes involved in the evolution of the earth are also characterized by cosmic year periodicity. The exploration of the regularities governing the earth‘s evolution and its origin from the concept of cosmic year periodicity, coupled with astronomical, cosmological and geological data, will give a great impetus to the rapid development of earth sciences. Research in this respect is of great significance both in theory and practice with respect to astronomy, geology and philosophy.  相似文献   

9.
The dissolved ionic constitutents of groundwaters are,in part,a recored of the minerals and rocks in aquifers through which the water has flowed.The chemical composition and association of these major ions in groundwaters have been used to trace groundwater flow paths and sources,In general,the chemical compostion of water in carbonate-rock aquifers in dominated by calcium,magnesium,and bicarbonate,whereas sodium,chloride,and sulfate can be dominant ions in the water that comes from volcanic aquifers or clay minerals.Since the 1990‘s,we have dealt with the geochemistry of groundwaters from more than 100 springs and wells in southern Nevada and eastrn california ,USA for major solutes and trace elements.This paper compiles the hydrochemical data of major ions of these groundwaters.Based on major ion geochemistry,groundwaters from southern Nevada and eastern California can be classified as carbonate aquifer water,volcanic aquifer water,and mixing water (either mixing of cabonate and volcanic aquifer waters or mixing with local recharges),Piper and stiff diagrams of major ions have graphically shown the general chemical characteristics,classification,and mixing relationships of groundwaters from southern Nevada and eastern California.  相似文献   

10.
西藏南部花岗岩类中微量元素的某些地球化学特征   总被引:1,自引:0,他引:1  
Types and intrusion times of granitoid rocks in Southern Xizang have been distingui.shed by diseriminatory and cluster analyses. By means of regression analyses, we discussed quantitatively the correlations between trace and major elements and the characteristics of trace element evolution. The features of trace element distribution and evolution have been discussed as well. It has been indicated, that the granitoid recks of different periods are resulted from partial melting to various extents in the lower crust or in the upper crust.  相似文献   

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