The West Kunlun orogenic belt is located at the conjunction of the paleo-Asian tectonic system and the Tethys tectonic system.
Petrological and mineralogical studies of the Early Cambrian metamorphic surface crust in this region have shown that in case
the metamorphism reached low-temperature granulate facies, the typical mineral assemblage is biotite-garnet-silimanite-K feldspar-plagioclase-quartz.
The peak metamorphic temperatures are within the range of 720–740°C and the pressure is 0.6 GPa ±. Three types of metamorphic
zircon have been detected in the metamorphic rocks: the complex inclusion-bearing type ; the early relic zircon inclusion-bearing
type; and the inclusion-free type. SHRIMP age determination of these three types of metamorphic zircon have revealed that
these zircons were formed principally during 400–460 Ma, indicating that pre-Cambrian metamorphic surface crust rocks underwent
low-temperature granulite facies metamorphism during the Caledonian. In combination with the geological characteristics of
this region, it is considered that when the oceanic basin was closed, there occurred intense intracontinental subduction (type
A), bringing part of the Early Cambrian metamorphic basement in this region downwards to the lower crust. Meanwhile, there
were accompanied with tectonic deformation at deep levels and medium- to high-grade metamorphism. This study provided important
chronological and mineralogical evidence for the exploration of the evolutionary mechanism and process of the West Kunlun
Early Paleozoic.
Part of the results from the research project “ Research on the West Kunlun pre-Cambrian tectonic events” under the program
“ Research on the important geological problems of China’ s pre-Cambrian” (No. 200113900070) sponsored by the China National
Geological Surveying Bureau. 相似文献
Natural Resources Research - Depletion of shallow mineral resources caused by deep mining has become an inevitable trend, and deep mining can increase safety accidents and geological hazards.... 相似文献
To ensure the safety of structures, high-speed railway and highway founded on liquefiable soils, liquefaction evaluation is a primary task. Herein, a dynamic set pair analysis method based on variable weights is introduced to assess liquefaction. A concept of connection degree of set pair consisting of the evaluation sample and the classification standard was described to interpret the uncertainty of liquefaction and relationship. Moreover, based on reward and penalty mechanism, state variable vectors were presented to assign composite weights of evaluation indicators in order to take into account impacts of indicator variation. And the integrated connection degree to each grade was calculated to evaluate liquefaction of the evaluated cases. Results from practical example and comparison with field investigation and extension method indicated that this proposed model used to evaluate liquefaction is feasible and effective. In addition, it can quantitatively describe liquefaction hierarchy of evaluated samples. 相似文献
The distribution of indigenous microorganisms was surveyed in Block 1 of Daqing Oilfield. Based on this survey, the indigenous microorganisms in the formation water were activated with different activator systems at the simulated stratum ecological environment. The changes of the number of bacteria of various physiological groups were determined during the process of activation. Also changes of pH value and composition of gas productions were analyzed at the end of culturing. The results showed that the selected block formation water contained a great number of saprophytic bacteria, hydrocarbon-oxidizing bacteria, fermentative bacteria, methane-producing bacteria and sulfate-reducing bacteria. Under the conditions that the growth of sulfate-reducing bacteria was controlled the block had the potential to enhance oil recovery by activating beneficial bacteria. The growth of sulfate-reducing bacteria can be inhibited through the activation of nitrate-reducing bacteria. The number of nitrate-reducing bacteria reached 106–107 cells/mL, but sulfate-reducing bacteria reached only 0–45 cells/mL in A system. Methane-producing bacteria can be activated by C, D activators. The relative content of biological methane in the light hydrocarbon gas reached 80% in C, D systems. B activator was conducive to the propagation of acid-producing bacteria, so that the pH value of the culture medium decreased from 7.5 to around 5.0. Hydrocarbon-oxidizing bacteria can be activated by various activator systems. There was low molecular light hydrocarbon in gas production according to the analysis of gas chromatograph. According to the content of methane and the number of methane-producing bacteria, methane only can be generated through activating methane-producing bacteria. By choosing different activator systems, various populations of indigenous microorganisms can be activated accordingly. 相似文献
Since Simpson and Hunter proposed in 1971 the idea that shallow water fronts were induced by tidal mixing, many authors have
investigated the tide induced shallow water fronts in various areas. It was generally assumed that a critical value of the
stratified parameterK=log10(H/U3) may be used to identify the location of these fronts. Here, H means the depth of sea waler. U denotes the characteristic
velocity of tidal current. and the critical value ofK is generally laken as 1.8–2.0.
In this paper. Simpson-Hunter’s stratified parameterK was calculated by using quasi-maximum current velocity (which consists of the six main tidal constituents. i.e.M2.S2,O1.K1.M4,MS4) in the H ranghai Sea (Yellow Sea) and in the northern Donghai Sea (East China Sea) as well. Caleulated results show that
the areas of the Subei (the northern part of Jiangsu) Shoal. the area off the mouth area of the Changjiang (the Yangtze) River,
along the coast of Shandong Peninsula. and along the western coast of Korea, the tidal mixing is strong. Calculations also
show that along the whole boundary of the HCWM and also along the western boundary of the cyclonic eddy in the northern Donghai
Sea, i.e. along the fronts, the value ofK is found to be very close to the eritical value 1.8. It is also to be noied that at these locations, the temperature of the
surface water is very low. These clearly show that shallow water fronts in the Huanghai Sea and in the northern Donghai Sea
as well, are induced by tidal mixing.
Contribution No. 1241 from Institute of Oceanology, Academia Sinica.
This paper was published in Chinese in theOcean. et Limn. Sinica16(6): 451–459, 1985. 相似文献