The Late Caledonian to Early Hercynian North Qilian orogenic belt in northwestern China is an elongate tectonic unit situated between the North China plate in the north and the Qaidam plate in the south. North Qilian started in the latest Proterozoic to Cambrian as a rift basin on the southern margin of North China, and evolved later to an archipelagic ocean and active continental margin during the Ordovician and a foreland basin from Silurian to the Early and Middle Devonian. The Early Silurian flysch and submarine alluvial fan, the Middle to Late Silurian shallow marine to tidal flat deposits and the Early and Middle Devonian terrestrial molasse are developed along the corridor Nanshan. The shallowing-upward succession from subabyssal flysch, shallow marine, tidal flat to terrestrial molasse and its gradually narrowed regional distribution demonstrate that the foreland basin experienced the transition from flysch stage to molasse stage during the Silurian and Devonian time.
A pilot survey on a microbial mineral exploration method based on soil Bacillus cereus spore counts was carried out across three different gold mining regions, which vary in soil type, climate condition and geological setting in northwestern Sichuan, China. B-horizon soils from these sites were analyzed for B. cereus spores, Au, Ag, Cu, Pb and Zn. The results show that the numbers of B. cereus spores generally increased in soils overlying gold mineralization. Specifically, elevated spore counts were found in samples slightly offset from the outcrops of orebodies, whereas soils directly above the outcrops of orebodies usually contained low spore counts. However, the background counts of B. cereus spores varied from place to place and were complicated by environmental and pedological factors, but the relative ratios of spore counts still were indicative of the underlying gold mineralization.
The Cambrian paleogeography in south Ch ina can be divided into Yangtze platform, platform margin slope (including upper slo pe and lower slope) and basin. The carbonate gravity deposits are well developed there, particularly in the Yangtze platform adjacent areas. This paper mainly d eals with declivity fan characters of the Chefu age in Fenghuang adjacent areas, western Hunan Province. According to their distribution and thickness, three ma in declivity fans have been divided in the study areas, namely, Dama (∈c dsf), Machong (∈c msf) and Huangheyuan (∈c hsf) declivity fans. Each fan's charac ters are described in detail in this paper. Based on their distribution range, s cale and fossiliferous layers, two peak periods (fair developmental period) are distinguished: (1) Linguagnostus reconditus Zone (time), and (2) Glyptagnostus reticulatus Zone (time). They were characterized by huge thick limestone breccia layers (single layer 3-4 m thick) and closely spaced spread. Besides, th ere are also two developmental periods: (1) Lejopyge laevigata-Proagnostus bulbus Zone (time), and (2) Agnostus inexpectans-Proceratopyge protracta Zone (time) to Erixanium Zone (time) to Corynexochus plumula-Sinoproceratopyge cf. kiangshanensis Zone (time), while Glyptagnostus stolidotus Zone (time) was an interstitial period (without or rare limestone breccias). All t hese features may verify the relative movement of the earth crust and paleoclima te variety of the Chefu age in the study areas.
Based on the data of organic carbon stable isotope ratios and magnet ic susceptibility, climate evolution in the past 5 kaB.P. in Poyang Lake plain (in Jiangxi Province) has been reconstructed. The results of the research indicate that the climate evolution can be divided into nine stages in the past 5 kaB.P.. Comparisons of different regional environmental records suggest that the intens ity and the temporal spatial changes of monsoon in China mainly controlled the climate evolution.
Petrologic geochemistry and isotopic chronology of the eclogites sug ge st that most of the eclogites in northern Dabie Mountains produced from the Tria ssic Yangtze subducted continental crust (lower crust and formed during the deep subduction) and the metamorphosed mafic-untramafic belt with eclogite, marble and meta peridotite blocks around the Mozitan-Xiaotian fault zone may represen t the meta tectonic melange produced during the active subduction of an ancient oceanic slab and subsequent collision between the Yangtze and North China conti nental plates. The cooling history of the eclogites from ~900 ℃ to 300 ℃ can b e subdivided into three stages: one isothermal stage and two rapid cooling stage s. The initial stage between (230±6) and 210 Ma was a near-isothermal or tempe rature rise process corresponding to the retrograded metamorphism of granulite facies with a rapid uplift of 4 mm/a, then two fast cooling stages occurred with cooling rate of ~10 ℃/Ma during 210 Ma to (172±3) Ma and ~4 ℃/Ma durin g (172±3) Ma to 130 Ma. After the peak metamorphism of eclogite-facies, their initial isothermal stage with slower uplift rate and cooling rate and high-T overprinting of granulite-facies metamorphism is the major difference between the eclogites in northern Dabie Mountains from those in southern Dabie Mountains. This may be one of the most important reasons to preserve few evidences of earl ier ultrahigh pressure metamorphism.
The Qooshchi area lies to northwest of Orumieh Lake in western Azerbaijan, NW Iran. A basement metamorphic complex, consisting of Precambrian schists and gneisses, has been intruded by gabbros and diorites. Granitoids are grouped into five suites according to their mineralogy, texture and exposed features. The main body, pink Qooshchi granite, and apophyse-like, myrmekite-bearing grani toids are discussed in this paper. On the basis of field observations and micros copic studies, an intensive metasomatism has overprinted the country rocks, espe cially gabbros, transforming them into a more felsic composition. A prior ev ent of intensive deformation and cataclasis preceded the metasomatism, allowing the introduction of hydrothermal fluids. K-metasomatism converted plagioclase into K-feldspar (microcline), myrmekite, and sodic plagioclase as Si-metasomati sm replaced the ferromagnesian silicates by quartz. Apophyse like bodies within gabbros, called leucometasomatites, are formed during this process.
Based on the results of two-dimension velocity structure, 1∶100 000 aeromagnetic anomaly, 1∶200 000 bouguer gravity anom aly and seismic anisotropy of Jiaodong and neighboring region in Shandong, China, the information of geophysical field was divided into two parts: deep- and shallow- focus fields. And then, the information of two different fields was combined with that of deep seated geology and ore deposit features. The syntheti cresult was adopted to analyze three-dimension structure, to probe into crust-mantle coupling effects of mineralization and dynamics of ore formation system.
Landsat TM digital spectral data of Lancang-Jinghong area(Yunnan Province) has been used for the purpose of geological interpretation. To meet this object, different image processing techniques including selected band color composites, principal component analysis and IHS decorrelation stretching are used to improve the discrimination of different lithological and structural features in the area.It was found that IHS decorrelation stretching images obtained from the transformation of false color composite 741(in red, green and blue) provided the best results based on the original data.By combining the characteristics of images produced by different approaches and other canonically transformed images with available geological data and surface observations, the geological interpretation could be done with satisfactory degree of accuracy.
This research was conducted at the sand dunes stabilization research station in Baiji district, Iraq. Three techniques for sand dunes stabilization are selected: the first method is stabilization by clayey block barriers; the second method is stabilization by dry planting of tamarix(tamarix articulata) cuttings and the third is stabilization by using cane branch barriers. Randomized samples were taken from the surface and subsurface layers of the stabilized and shifting sand dunes to evaluate the effect of the three techniques on wind erosion parameters. The results indicate high significant differences between the wind erosion parameters in the surface and subsurface layers in the stabilized sand dunes, while there are insignificant differences between the subsurface layer of the stabilized dunes and the surface and subsurface layers in the active sand dunes. The results clarify the fact that there is an increase in the percentage of clay, silt, organic matter, mean weight diameter and the percentage of the dry aggregates(> 0.84 mm). A decrease is found in the rate of disaggregation for the dry aggregates in the samples of the surface layer of stabilized dunes when compared with the subsurface layer of stabilized dunes and the surface layer of the shifting sand dunes. There is a positive high significant correlation among the aggregate stability parameters and the percentage of clay and silt, and the content of organic matter in the studied layers.
The purpose of this paper is to analyze the regional fault systems of Qaidam basin and adjacent orogenic belts. Field investigation and seismic interpretation indicate that five regional fault systems occurred in the Qaidam and adjacent mountain belts, controlling the development and evolution of the Qaidam basin. These fault systems are: (1)north Qaidam-Qilian Mountain fault system; (2) south Qaidam-East Kunlun Mountain fault system; (3)Altun strike-slip fault system; (4)Elashan strike-slip fault system, and(5)Gansen-Xiaochaidan fault system. It is indicated that the fault systems controlled the orientation of the Qaidam basin, the formation and distribution of secondary faults within the basin, the migration of depocenters and the distribution of hydrocarbon accumulation belt.
Collecting waste water with a certain concentration of organic pollutants COD(chemical oxygen demand), static adsorption, static biodegradation and dynamic soil column experiments were made in laboratory, we researched migration and transformation of COD in aerated zone, and put forward a mathematical model showing the process. The results show that adsorption of organism in aerated zone is linear, which is represented by Henry's law s= Kdc+sd, adsorption coefficient Kd= 0.069 3; biodegradation diagram accord basically with first-order kinetics equation c= c0e-K1t, biodegradation coefficient K1= 0.049 9 d-1; dispersion coefficient D= 0.002 42 m2/d in experiments. The migration and transformation of organic pollutants(COD)in aerated zone jointly result from many factors such as dispersion, adsorption and biodegradation etc..
The karst immersion and waterlogging is one of the typical and the most harmful natural disasters in southern karst areas of China. It is threat to the local production and life for a long time. In recent years, due to the construction of more reservoirs, the disaster became serious. This article takes immersion and waterlogging of Banwen's subterranean rivers in Yantan reservoir area as an example, researches the daily rainfall's reflection to the water level of reservoir depression, discusses characteristics of immersion and waterlogging of the valley, analyzes the disaster index in detail, such as water level process, the highest water level, sensitive rainfall, original waterlogged rainfall and delayed day numbers etc., and provides the reference as a basis to the disaster analysis.
This paper presents a synthetic analysis method for multi-sourced geological data from geographic information system(GIS). In the previous practices of mineral resources prediction, a usually adopted methodology has been statistical analysis of cells delimitated based on thoughts of random sampling. That might lead to insufficient utilization of local spatial information, for a cell is treated as a point without internal structure. We now take"cell clusters", i. e., spatial associations of cells, as basic units of statistics, thus the spatial configuration information of geological variables is easier to be detected and utilized, and the accuracy and reliability of prediction are improved. We build a linear multidiscriminating model for the clusters via genetic algorithm. Both the right-judgment rates and the in-class vs. between-class distance ratios are considered to form the evolutional adaptive values of the population. An application of the method in gold mineral resources prediction in east Xinjiang, China is presented.
Despite the constant expansion of the application of GIS, in recent years, the data processing ability of the application system developed with GIS_Tool is quite limited. Management information system with the geographical information can not only be used to deal with data commonly, but also deal with digitized maps as GIS_Tool does. Thus it can help the user develop an application system high-quali-fied both in maps and traditional data. This paper, by taking the method of integrated MapInfo in the application of Visual Basic as an example, mainly illustrates two technological problems-integrated map technology and the multiuserization of MapInfo geographical information. And also the concrete solutions to the problems are provided.