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2006 Vol. 17, No. 2

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Structural Geochemical Study of the Yuxi Fold-Thrust Belt in the Southern North China Plate
Wen-yong LI, Bin XIA, Dong-xu LI
2006, 17(2): 95-102.

The Yuxi (豫西) fold-thrust fracture belt is part of the gigantic fold-thrust fracture belt that extends NW in the southern North China plate. The contents of major elements of tectonites were analyzed by ICP-AES. The analysis of chemical compositions and new stress minerals indicates: extending from the surrounding country rocks to the center of the fracture belt, the Fe2O3 content gradually increases while the FeO content gradually decreases; regular increase, decrease or peak changes are shown for chemical compositions like SiO2, Al2O3, Fe2O3, MgO, CaO, FeO, loss on ignition, TiO2, K2O, Na2O, etc.. New stress minerals are developed for the south branch and few for the north branch. The characteristics of chemical compositions and new stress minerals of the thrust fracture demonstrate that the fracture belt has undergone a process from a closed reducing environmental system to a relatively open, oxidizing environmental system, and compressive fractures have resulted from compression in the late stages of evolution, and the dynamothermal metamorphism and thrusting intensities are different between the south and north branches of the belt, which is strong for the south branch but relatively weak for the north branch.

Carbonate Diagenesis Controlled by Glacioeustatic Sea-Level Changes: A Case Study from the Carboniferous-Permian Boundary Section at Xikou, China
Hai-jun ZHANG, Lin DING, Xun-lian WANG, Lei WANG, Qing-shan WANG, Guo-ying XIA
2006, 17(2): 103-114.

The platform-facies carbonate rocks of the Carboniferous-Permian boundary strata are well developed and outcropped in Xikou (西口), Zhen'an (镇安) County, Shaanxi (陕西) Province, China. The carbonate diagenesis in the Carboniferous-Permian boundary section at Xikou contains many processes with conspicuous effects, including micritization, cementation, mechanical and chemical compaction, neomorphism, and dissolution. Based on mineralogical composition and microfabrics, the diagenetic environments are distinguished into marine, near surface meteoric and burial environments. Detailed petrographical observation of abundant thin sections integrated with previous studies on sequence stratigraphy reveals that the carbonate diagenesis in the Carboniferous-Permian boundary section is related to the relative stratigraphic position of the rocks in the high-frequency cycles and controlled by the glacioeustatic sea-level changes. There are distinctive differences in diagenetic patterns between the lower transgressive sequence and the upper regressive sequence in a cyclothem. The diagenesis in the lower transgressive sequence is mainly characterized by pressure dissolution and recrystallization of mudstone and wackstone in a burial environment, and the diagenesis in the upper regressive sequence by cementation and leaching of freshwater in a meteoric environment.

Acyclic Alkanes in the Soil over Heshang Cave in Qingjiang, Hubei Province
Yang PU, Jun-hua HUANG, Xian-yu HUANG, Jing-wei CUI, Chao-yong HU
2006, 17(2): 115-120.

The reports that relate to the biomarker's fate and characteristics of the modern soil in the karst area are very lacking. By using gas chromatography-mass spectrometry (GC-MS), a series of biomarkers were identified from the soils collected over Heshang cave (和尚洞) in Qingjiang (清江), Hubei (湖北) Province. The distribution of n-alkanes is mainly from C_ 25 to C_ 33 in carbon number, with a maximum at C_ 31. They have a strong odd-over-even carbon number predominance. These characteristics represent an input mainly from higher plants. The lipid parameters, including CPIh (carbon preference index), R_ h/l (ratio of lower- to higher-molecular-weight homologues) and ACL (average chain length), show comparable trends with depth, probably reflecting vegetation change and microbial degradation. Series of monomethylalkanes and diploptene are present in the extractable organic matter; they might be derived from soil microbes, cyanobacteria in particular.

Age and General Characteristics of the Calimicrobialite near the Permian-Triassic Boundary in Chongyang, Hubei Province
Hao YANG, Su-xin ZHANG, Hai-shui JIANG, Yong-biao WANG
2006, 17(2): 121-125, 131.

The calimicrobialites of Chongyang (崇阳), Hubei (湖北) Province, occur above the mass extinction line in the Late Permian reef facies. Below the boundary are the sponge reef limestone, crinoid limestone and algae-foraminifer bioclastic limestone of the Changxing (长兴) Formation. The calimicrobialites are generally composed of mid-coarse grains and microlite calcite with a structure of "graniphyic fabric" and stromatolite. The fossils discovered in the calimicrobialites include globular cyanobacteria, ostracods, micro-gastropods, bivalves, fish teeth and some micro-problematical fossils. Conodont fossils of Hindeodus parvus, H. typicalis and H. latidentatus were also found in the calimicrobialites. According to the conodonts, the calimicrobialites spanned the latest Permian and earliest Triassic in the Chongyang Section. The upper part above the first occurrence of Hindeodus parvus should be attributed to the earliest Triassic, and the lower part to the Changhsingian. The sedimentary structure, fossil composition and conodont zonation of the Chongyang calimicrobialites can be well correlated with the calimicrobialites found in other areas of South China.

Further Study on Geochemical Characteristics and Genesis of the Boninitic Rocks from Bikou Group, Northern Yangtze Plate
Yong-fei LI, Shao-cong LAI, Jiang-feng QIN
2006, 17(2): 126-131.

Compared with the major and trace elements of typical boninite, the metabasalts collected from the Nanfanba (南范坝) -Miaowanli (庙湾里) region in the Bikou (碧口) block could be treated as boninite characterized by low-Si, low-Ti, low-P, high-Mg# and high Al2O3/TiO2, consistent with geochemical features of boninite. The normal mid-ocean ridge basalt (N-MORB) normalized spider diagram displays fairly depleted high field strong elements (HFSE) (Zr, Y, Ti). Enriched refractory elements (Cr, Co, Ni) as well as light rare earth elements (LREE) -depleted chondrite-normalized REE distribution patterns suggest the boninitic magmas are derived from an extremely depleted mantle wedge in the presence of a hydrous fluid, meanwhile signifying the source region had previously undergone a high degree partial melting process yielding primary magmas with enriched large ion lithophile elements (LILE). In addition, almost all the samples in the Nb-Zr-Y and Ti-Zr-Y discrimination diagrams were plotted in the island arc basalt (IAB) field. Coupled with the island arc tholeiitic (IAT) basalt in the study region, therefore, the geochemical characteristics of the studied rocks indicate the meta-basalts probably occurred in a fore-arc subduction setting. This conclusion may be of great significance for the further study of the tectonic background of the Bikou volcanism.

Preliminary Study on the PGE Geochemistry of the Permian Basalts in the Jinping Area
Hong NIAN, Wei SHEN, Xue-shu ZHANG
2006, 17(2): 132-137.

To disclose and study the magma genesis of the Permian basalts in the Jinping (金平) area, the PGE and Au contents of the Permian basalts in the Jinping area were assayed by use of the ICP-MS method. The PGE data show relatively strong differentiation of basaltic magma in comparison with the primitive mantle. The primitive mantle-normalized pattern is a left-dipping curve of the Pd-Pt enriched type. The Pd/Ir ratios of the PGE of the Permian basalts in the Jinping area are higher than those of the primitive mantle and the upper primitive mantle and the chondrite meteorite. The Pd/Ir ratios exhibit great similarity with that of the Emeishan (峨眉山) basalts as a whole suggesting a similar material source. It is concluded that they are derived from the basaltic magma of the upper mantle source with a lower melting degree, which shares the similar magma material source with the Emeishan Permian basalts as a whole.

Sedimentary Characteristics and Reservoir Prediction of Paleogene in the East Part of Kuqa Foreland Basin
De-tian YAN, Hua WANG, Jia-hao WANG, Qing-chen WANG
2006, 17(2): 138-145, 157.

Most of the Mesozoic and Cenozoic large-scale hydrocarbon-bearing basins in western China were formed in a similar foreland setting. Hydrocarbon exploration of the Kuqa foreland basin requires research into the sedimentary characteristics and filling evolution of the depositional sequences and their response to the basin process. Based on an analysis of outcrops, well logs and high resolution seismic data, the sedimentary system types and distribution characteristics of the Paleogene in the east part of Kuqa foreland basin were systematically studied. The results show that: (1) Three types of sedimentary systems are developed in the area: an oxidative salty wide shallow lacustrine system, a fan delta system and an evaporitic bordersea system. (2) The configuration and evolution of the depositional systems of the Paleogene in the Kuqa foreland basin were predominantly determined by foreland tectonism. Vertically, the Paleogene sedimentary sequence can be divided into three parts: the lower, middle and upper depositional system tracts. The lower and upper tracts commonly consist of progradational or aggradational sequences, while the middle part is usually comprised of a set of aggradational to transgressive third-order sequences. Laterally, the sedimentary systems in the east part of the Kuqa foreland basin spread from east to west as a whole, and the sedimentary facies obviously vary from south to north. The sand bodies of the delta front facies are excellent gas reservoirs, characterized by rather thick, extensive and continuous distribution, high porosity and permeability, and just a few barrier beds.

Evaluation of Two Absolute Radiometric Normalization Algorithms for Pre-processing of Landsat Imagery
Han-qiu XU
2006, 17(2): 146-150, 157.

In order to evaluate radiometric normalization techniques, two image normalization algorithms for absolute radiometric correction of Landsat imagery were quantitatively compared in this paper, which are the Illumination Correction Model proposed by Markham and Irish and the Illumination and Atmospheric Correction Model developed by the Remote Sensing and GIS Laboratory of the Utah State University. Relative noise, correlation coefficient and slope value were used as the criteria for the evaluation and comparison, which were derived from pseudo-invariant features identified from multitemporal Landsat image pairs of Xiamen (厦门) and Fuzhou (福州) areas, both located in the eastern Fujian (福建) Province of China. Compared with the unnormalized image, the radiometric differences between the normalized multitemporal images were significantly reduced when the seasons of multitemporal images were different. However, there was no significant difference between the normalized and unnormalized images with a similar seasonal condition. Furthermore, the correction results of two algorithms are similar when the images are relatively clear with a uniform atmospheric condition. Therefore, the radiometric normalization procedures should be carried out if the multitemporal images have a significant seasonal difference.

Classification and Extraction of Urban Land-Use Information from High-Resolution Image Based on Object Multi-features
Chun-fang KONG, Kai XU, Chong-long WU
2006, 17(2): 151-157.

Urban land provides a suitable location for various economic activities which affect the development of surrounding areas. With rapid industrialization and urbanization, the contradictions in land-use become more noticeable. Urban administrators and decision-makers seek modern methods and technology to provide information support for urban growth. Recently, with the fast development of high-resolution sensor technology, more relevant data can be obtained, which is an advantage in studying the sustainable development of urban land-use. However, these data are only information sources and are a mixture of "information" and "noise". Processing, analysis and information extraction from remote sensing data is necessary to provide useful information. This paper extracts urban land-use information from a high-resolution image by using the multi-feature information of the image objects, and adopts an object-oriented image analysis approach and multi-scale image segmentation technology. A classification and extraction model is set up based on the multi-features of the image objects, in order to contribute to information for reasonable planning and effective management. This new image analysis approach offers a satisfactory solution for extracting information quickly and efficiently.

Landslides at Qingjiang River in the Downstream Area of Shuibuya Dam Site, China
D Kallen, Wei XIANG, D Ehret, J Rohn
2006, 17(2): 158-162.

To enhance the general knowledge of landslides in China, the DAAD (German Academic Exchange Service) is financing an investigative project. As part of this project, at the Qingjiang (清江) River, a 10 km 2 area downstream of the Shuibuya (水布垭) dam site was geologically and geotechnically mapped to gather information concerning landslides and their correlation to lithology, slope angles and texture. The geological mapping contained the characterization of the lithological units. The characterization of the shape of landslides and the classification of rocks into units with similar geotechnical behavior is contained in the geotechnical map. Samples were taken and investigated using X-ray diffraction to identify the clay minerals and geotechnical tests to determine the effective shear angle and cohesion of rocks and soils. Geotechnical mapping showed a close connection between lithology, slope angle and texture concerning the occurrence of landslides. Most landslides occur on the northern bank of the Qingjiang River where the dip angle of the bedding is nearly parallel to the slope, resulting in potential and effective slide planes. On the southern bank only sporadic and small landslides occur because the bedding is antipodal to the slope angle. This pilot work is a base for further and more detailed investigations in this area.

Modeling the 3D Terrain Effect on MT by the Boundary Element Method
Bai-yao RUAN, Shi-zhe XU, Zhi-feng XU
2006, 17(2): 163-167.

A numerical method is put forward in this paper, using the boundary element method (BEM) to model 3D terrain effects on magnetotelluric (MT) surveys, Using vector integral theory and electromagnetic field boundary conditions, the boundary problem of two electromagnetic fields in the upper half space (air) and lower half space (earth medium) was transformed into two vector integral equations just related to the topography : one magnetic equation for computing the magnetic field and the other electrical equation for computing the electrical field. The topography integral is decomposed into a series of integrals in a triangle element. For the integral in a triangle element, we suppose that the electromagnetic field in it is the stack of the electromagnetic field in the homogeneous earth and the topography response which is a constant; so the computation becomes simple, convenient and highly accurate. By decomposition and computation, each vector integral equation can be calculated by solving three linear equations that are related to the three Cartesian directions. The matrix of these linear equations is diagonally dominant and can be solved using the Symmetric Successive Over-Relaxation (SSOR) method. The apparent resistivity curve of MT on two 3D terrains calculated by BEM is shown in this paper.

Interpreting Dual Laterolog Fracture Data in Fractured Carbonate Formation
Shao-gui DENG, Xiao-chang WANG, De-jiang ZOU, Yi-ren FAN, Zhen YANG
2006, 17(2): 168-172.

The estimation of fractures is key to evaluating fractured carbonate reservoirs. It is difficult to evaluate this kind of reservoir because of its heterogeneously distributed fractures and anisotropy. A three-dimensional numerical model was used to simulate the responses of the dual laterolog (DLL) in a fractured formation based on a macro-isotropic anisotropic model. Accordingly, a fast fracture- computing method was developed. First, the apparent conductivity of the DLL is linearly related to the porosity of the fracture and the conductivity of pore fluid. Second, the amplitude difference of the deep and shallow apparent resistivity logs is mainly dependent on the dip angle of the fracture. Then the response of the DLL to a formation with dip angle fractures is approximately depicted as a function of the bulk resistivity of the rock, the porosity of the fractures and the conductivity of fracture fluid. This function can be used to compute the porosity of fracture quickly. The actual data show that the fracture parameters determined by the DLL closely coincide with the formation micro imager log.

Logging Data High-Resolution Sequence Stratigraphy
Hong-qi LI, Yin-fu XIE, Zhong-chun SUN, Xing-ping LUO
2006, 17(2): 173-180.

The recognition and contrast of bed sets in parasequence is difficult in terrestrial basin high-resolution sequence stratigraphy. This study puts forward new methods for the boundary identification and contrast of bed sets on the basis of manifold logging data. The formation of calcareous interbeds, shale resistivity differences and the relation of reservoir resistivity to altitude are considered on the basis of log curve morphological characteristics, core observation, cast thin section, X-ray diffraction and scanning electron microscopy. The results show that the thickness of calcareous interbeds is between 0.5 m and 2 m, increasing on weathering crusts and faults. Calcareous interbeds occur at the bottom of a distributary channel and the top of a distributary mouth bar. Lower resistivity shale (4-5 Ω · m) and higher resistivity shale (> 10Ω·m) reflect differences in sediment fountain or sediment microfacies. Reservoir resistivity increases with altitude. Calcareous interbeds may be a symbol of recognition for the boundary of bed sets and isochronous contrast bed sets, and shale resistivity differences may confirm the stack relation and connectivity of bed sets. Based on this, a high-resolution chronostratigraphic frame- work of Xi-1 segment in Shinan area, Junggar basin is presented, and the connectivity of bed sets and oil-water contact is confirmed. In this chronostratigraphic framework, the growth order, stack mode and space shape of bed sets are qualitatively and quantitatively described.

Determination and Application of the Sharp Degradation Point of Concrete under Environmental Actions
Xi-wu ZHOU, Jun WEI, Xin LUO
2006, 17(2): 181-184.

To study the sharp degradation point of concrete durability, damage at the characteristic failure point under loads was first obtained by the application of the one-dimensional stress-strain relationship of Saenz. Then based on the principle that damage at the characteristic failure point subjected to loads is equal to the damage in accordance with the characteristic point of concrete durability under environmental actions, the sharp degradation point of concrete durability was determined. The results were applied to the case of concrete suffering freeze-thaw actions. Good accordance between experimental results and forecasted results indicated the reliability of this method.

Numerical and Experimental Study of Free Vibration Characteristics of a Cable-Stayed Bridge
Jian-min ZI, Yuan-han WANG, Hong-ping ZHU
2006, 17(2): 185-188.

The main aim of this study is to understand the dynamic behavior of a cable-stayed bridge, using both numerical and experimental analysis. A three-dimensional finite element model for the bridge was developed for the free vibration analysis and the ambient vibration properties of the bridge were determined through field testing. The experimental and numerical results of natural frequencies and the associated mode shapes were compared, and the high accuracy between them shows that the 3D model is capable of approximately representing the dynamic behavior of the bridge and the use of ambient vibration survives in future testing of the bridge. These dynamic characteristics can be used as the basis for updating the finite element model and also for global damage detection.