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2001 Vol. 12, No. 2

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GIS Based Evaluation of Danger in Karst Collapse
Chen Xuejun, Chen Fujian, Liu Baochen, Bao Huiming
2001, 12(2)
New Evidence from Alashan Area of West Nei Monggol to Reveal Enigma of Dinosaur Extinction
Hongzhi Wang, Xueyin Wang, Rendong Li
2001, 12(2): 95-98.

Dinosaur extinction of the late Cretaceous is an enigma. A scorched earth layer was discovered at the end of the Cretaceous system from drilling cores in west of Nei Monggol in China. And there was a creature interruption for 6-8 million years after that period through fossil analysis of the area and the adjacent area. Just in the same system of scorched earth layer, the Polish scientists found the abnormal geo-chemical phenomena and high dense universal substances generally contained in meteorite. The authors think, at the end of Cretaceous, many celestial bodies ran into the earth. The collision caused fires all over the world and slowed down the speed of the earth rotation suddenly. The oxygen density decreased sharply. And because of the sudden increase of day length, the biological clock of dinosaur was in the state of chaos. That's the reason why dinosaurs got extinct. It took a very long time both for the oxygen to return normal for most creatures to live and for the new species fit for new rotation speed of the earth to come into being. That's why there was the creature interruption after the extinction of the dinosaur.

Dinosaur Footprints of Early Cretaceous in Site 1, Yanguoxia, Yongjing Country, Gansu Province
Yuansheng Du, Daqing Li, Bingxia Peng, Rulin Lei, Zhongcai Bai
2001, 12(2): 99-99, 154.
A High-Precision Forecasting Model and Its Constructing Method for Vein-Type Gold Deposits
Jun Zhang
2001, 12(2): 100-107.

A high-precision forecasting and prospecting model incorporating the "field theory-field structure analysis-field simulation", a temporal and spatial structural framework reflecting local extremely fine structures, is established to make an effective extraction and an integrated analysis of multivariate forecasting information. This model can best show not only the coupling between metallogenic anomalous structure, mineralized structure and information structure, but also the extraction, optimization, matching and summarization of key forecasting information. The technological keys to this model are the fine structural analysis of geological and geophysical and geochemical anomalous fields and metallogenic fields, and the establishment of occurrence patterns for the spatial location of orebodies.

Theory of Geological Anomaly in Remote Sensing
Jianping Chen, Pengda Zhao, Huoping Ding
2001, 12(2): 108-112.

Geological anomaly is geological body or complex body with obviously different compositions, structures or orders of genesis as compared with those in the surrounding areas. Geological anomaly, restrained by the geological factors closely associated with ore-forming process, is an important clue to ore deposits. The geological anomaly serves as a geological sign to locate ore deposits. Therefore, it is very important to study how to define the characteristics of geological anomaly and further to locate the changes in these characteristics. In this paper, the authors propose the geological anomaly based on the remote-sensing images and data, and expound systematically such image features as scale, size, boundary, morphology and genesis of geological anomalies. Then the authors introduce the categorization of the geological anomalies according to their geneses. The image characteristics of some types of geological anomalies, such as the underground geological anomaly, are also explained in detail. Based on the remote-sensing interpretation of these geological anomalies, the authors conclude that the forecasting and exploration of ore deposits should be focused on the following three aspects: (1) the analysis of geological setting and geological anomaly; (2) the analysis of circular geological anomaly, and (3) the comprehensive forecasting of ore deposits and the research into multi-source information.

Soil Loss by Wind Erosion for Three Different Textured Soils Treated with Polyacrylamide and Crude Oil, Iraq
Jabbar Mushtak Talib
2001, 12(2): 113-116.

The study is conducted to estimate the resistance of three soils (EL-Hartha clay loam, Barjisiya sandy loam and the soil near the sand dunes in Sheikh sa'ad area sandy soil) to wind erosion, it is also aimed at getting full acquaintance of the relationship between the soil loss and the physical and chemical features of soil. In addition to the experiment of some soil stabilizers, polyacrylamide (PAM) concentration of 0.2 % and crude oil in concentration of 1 % in order to reduce or prevent wind erosion. The study shows that the amendment increased the dry soil aggregate > 1 mm, mean weight diameter and soil moisture. It is clear that polyacrylamide had greater effect than that of crude oil, besides the great effectiveness of these amendments in decreasing bulk density and relations of soil loss.

Vertical Migration of Petroleum via Faults in Zhu Ⅲ Subbasin, Pearl River Mouth Basin, South China Sea
Fengjun Nie, Sitian Li, Hua Wang, Xinong Xie, Keqiang Wu, Meizhu Jiang
2001, 12(2): 117-126.

The problem that faults act as a conduit for hydrocarbon bearing fluid flow has been under debate for a long time. The southern boundary fault (FS) and No.2 fault belt in the Zhu Ⅲ subbasin in the Pearl River Mouth basin (PRMB) of South China Sea (SCS) are considered as the conduit of hydrocarbons for the oil and gas fields in the hydrocarbon generating half grabens. Based upon the basin modeling and seismic velocity inversion simulation, there are abnormal pressure compartments in the central part of half grabens. Wenchang, Enping and Zhuhai FormationⅡare seated within the abnormal-pressure zone, while the Zhuhai Formation Ⅰ is within the pressure-transition zone. The abnormal pressure was mainly caused by undercompaction due to the high rate of sedimentation for layers with an abnormal-pressure. The increase of temperature of inclusions as the increase of depth supports vertical migration via faults in the study area.

Development of Diapirs and Accumulation of Natural Gases in Yinggehai Basin
Zaisheng Gong, Jiaming Yang, Jianwu Hu, Fang Hao
2001, 12(2): 127-131.

Overpressure developed throughout most of the Yinggehai basin. The burial depth to top overpressure varied from about 1 600 m to 4 500 m, with the shallowest top overpressure occurring in the depocenter. The main cause of the overpressure was disequilibrium compaction resulting from rapid sedimentation of fine-grained sediments. The overpressure was strengthened by the retention of fluids including gases due to lack of faults before diapir development. The diapirism in the Yinggehai basin was a combined result of the strong overpressure and the tensile stress field caused by the right-lateral slip of the boundary-fault. The diapirism, a product of the movement of overpressured fluids and plastic shales, shaped the vertical conduits from source to traps that would be absent without overpressured fluid release. Natural gas accumulation in traps in the diapir structure zones was also intermittent, which can be inferred from the inter-reservoir compositional heterogeneity, transient thermal effect of fluid flow and migration fractionation.

Characteristics of Water Environment in Regions of Zhaling and Eling Lakes near Waterhead of Yellow River
Cao Wenbing, Li Wan, Fusheng Hu, Zhaoli Shen, Weide Yan
2001, 12(2): 137-141.

Conditions of the water environment in the region of the Zhaling and Eling lakes, which are located in the frozen earth zone on the Qingzang plateau, are unique. The equilibrium of the water quantity of the two lakes is maladjustment under the condition of a dry and cold climate in which evaporation is greater than precipitation. The Zhaling and Eling lakes have been atrophying, leaving three lake terraces and star studded lagoons around the two lakes since Holocene. When these lagoons were separated from the original lakes, they became cut lake basins, and were transformed from fresh water lakes into salt water lakes, salt lakes or salt playas owing to strong evaporation. This kind of evolutionary process will continue in the future.

Effect Blasting Excavation of Yujiapeng Tunnel on Stability of Nearby Giant Dangerous Rock Masses (DRM)
Hongming Yu, Yanxin Hu
2001, 12(2): 142-144.

On the basis of the interpretation of engineering geology of the tunnel and of its adjacent dangerous rock masses (DRM), this paper presents the energy and vibration parameters of the explosion that propagates in different blasting modes according to the experimental formulas now usually employed. Then the stability checking computation of T 8-T 12 area, the most dangerous area of DRM, is conducted under the limited blasting condition and with the limited equilibrium method. The result shows that the effect on the stability is only 5.5 % and that this area also contains certain safety reserves.

Study on Smooth-Blasting Results in Jointed and Fractured Rock
Li Wu, Jianping Chen
2001, 12(2): 145-159.

Factors that affect blasting results may be grouped into those factors that can be controlled and those that cannot be controlled. The controllable factors include explosive properties, initiation timing, and blast geometry. The uncontrollable factors comprise the rock 's natural structures, such as joints and fractures, and the properties, such as elastic constants, density and strength. Among these, the in- fluence of rock structural planes often contributes a high degree of vari ability to blasting results. This paper presents a theoretical analysis of rock structural plane influences on smooth-blasting results based on elasticity and stress wave propagation theory with an emphasis on smooth blasting techniques. Two types of simulated experiments in lab (using strain and acoustic emission measurements) are used to verify the theoretical analysis. The results show that it is difficult to achieve smooth-blasting results when the angle between the natural rock structural planes and the blast-induced fracture planes ranges from 10° to 60°. Among these angles, 30° is the least desirable angle to produce a smooth wall. For an- gles less than 10° and greater than 60°, the influence of rock structural planes on blasting results can be ignored.

Frequency Analysis of Heavy Tamping Vibration
Jinzhong Sun, Hanhua Tan, Shengwen Qi, Shuli Wang
2001, 12(2): 150-154.

Heavy tamping is one of the important methods for ground treatmentîBut the vibration is often a problem that restricts the application during heavy tamping. On the other hand, as an instant impact load with controllable energy, heavy tamping is a good test in situ for the study of soil dynamics. With the analysis in the field of frequency, deductive method for medium-effecting function and excitation function of heavy tamping is put forward in this paper.

Magnetic, Geochemical and Mineralogical Characteristics of Soils in Qiangtang Basin, Tibet, China: Implications for Prospective Oil and Gas Land
Qingsheng Liu, Qifan Wu, Haixia Li, Tongjin Cheng, Xianghua Xia, LungS Chan, Shuang Zhang
2001, 12(2): 155-159.

The alterationof iron-bearing minerals induced by hydrocarbon microseepage above oil/gas reservoirs has been evaluated using measurements of soil magnetic susceptibility κ, geochemical compositions (gas hydrocarbon and alteration carbonateΔC), and composition and concentration of iron-bearing minerals.The analyses were performed along two profiles across the Qiangtang basininTibet, China: the Nuoermahu-Xuehuanhu profile (C)and the Mugar-i Huochetoushan profile (E).Results show that three strong magnetic anomalies (C1, E1 and E2anomalies)are related to the distribution of Neogene volcanic rocks onthe surface in the Gangmacuo-Xiyaergang uplift.Two other anomalies (C2and E4 anomalies), characterized by both moderately amplitude magnetic susceptibility and elevated soil gas hydrocarbons, occur near fault zones in the Cuoni-Donghu synclinorium.These latter anomalies display characteristics of hydrocarbon microseepage anomalies commonly associatedwithoil andgas accumulations.Theirpresence in the Cuoni-Donghu synclinorium suggests that parts ofthe Qiangtang basin may have significant petroleum potential.

Cold Thermal Anomalous Structure within Lower Mantle and Its Geodynamic Implications
Xiong Xiong, Houtze Hsu, Jiwen Teng
2001, 12(2): 160-164.

The lateral temperature a nomalous structure of the lower mantle is reconstructed from the seismic tomographical model and high temperature and high pressure laboratory results. A significant correlation between the distribution of the cold anomaly and the location of past subduction belts shows that the shallower anomaly corresponds to the younger subduction sites, while the deeper anomaly to the older ones.This correlation also suggests that the cold anomaly may have come from the subduction slabs and the scale of mantle convection may have been completed.The coldest and largest anomaly is concentrated near the core-mantle boundary (CMB). Few cold anomalies float in the shallower and middle parts of the lower mantle, suggesting that the downward migration of the subduction slabs, discontinuous and step-like, may be divided into the following three stages: subduction, stagnation at the 670 km discontinuity due to the phase transition, and disintegration when the size exceeds the critical point.

Fast Web-Based Data Transmission
Zukuan Wei, Jaehong Kim, Haeyoung Bae
2001, 12(2): 165-176.

Since web-based GIS processes large-size spatial geographic information on internet, we should try to improve the efficiency of spatial data query processing and transmission.This paper presents two efficient methods for this purpose: division-transmission and progressive-transmission methods.In division-transmission method, a map can be divided into several parts, called "tiles", and only tiles can be transmitted at the request of a client.In progressive-transmission method, a map can be split into several phase views based on the significance of vertices, and a server produces a target object and then transmits it progressively when this spatial object is requested from a client.In order to achieve these methods, the algorithms, "tile division", "priority-order estimation" and the strategies for data transmission are proposed in this paper, respectively.Compared with such traditional methods as "map total transmission" and "layer transmission", the web-based GIS data transmission, proposed in this paper, is advantageous in the increase of the data transmission efficiency by a great margin.

Abstracts of Earth Science—Journal of China University of Geosciences(Chinese Version, Volume26, Nos1-3, 2001)
2001, 12(2): 177-188.