Geoscience

Analysis of Transform Structures in Extensional Fault Depressions

CHEN Fa-Jing, HONG Xin-Wen, CHEN Zhao-Nian

2011, 25(4): 617-625.

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Analysis of transform structures is important to study regional structural setting and hydrocarbon occurrence in extensional fault depressions. Based on previous studies and recent explanation of extensive seismic reflection survey in Bohai Bay Basin, some controversial and interesting problems of the transform structures are discussed in this paper. （1） We redefine the technical terms of the transform structures used in previous studies, such as segmentation structrure,transform structure，transfer zone,accommondation zone and transform zone,and illustrate its fundamental concepts. （2）According to different modes of the transform structures, which links two relay master faults and related fault depressions,a new scheme of classification is presented.First,the transform structures can be classified as three major types：transfer zone,accommondation zone and transform zone,and than,considering its special criteria,each type of the tranform structures is subdivided further into some subtypes. （3）Formation mechanism of transfer zone and accommondation zone is closely related with regular change of displacement along fault strike. The maximum displacement occurs in center segment of fault and gradually reduced to minimum toward fault termination,at which the transfer zone and accommondation zone are developed.However,because of difference in some controlling factors,such as overlapping degree of relay faults,keeping or not keeping constant displacement,attitude of relay faults dip and transverse distance between the ends of relay faults in plane view,either transfer zone or accommondation zone and a wide variety of its related structure styles are formed.Differing from the transfer zone and accommondation zone,the transform zone is characterized by transform fault which links different segments of extensional structural domains.It is suggested that the transform zone is formed due to difference in crustal extensional rate.

Recognition of Sedimentary Characteristics and Its Significance to Petroleum

WANG Gong-Liang, ZHOU Ting-Quan, SONG Jian-Yong, MIAO Xiao-Long

2011, 25(4): 626-634.

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Lithologic traps are the main play for the further exploration in western Dongying Depression. But the knowledge about sedimentary characteristics in this area is disputed. Based on the former views, sedimentary characteristics are reidentified through facies types, provenance systems, facies distribution and facies model. The new understandings are as follows. The main facies types are braided delta, nearshore sublacustrine fan, turbidite fan and lake. There are three provenance systems which are southern Jinjia, western Gaoqing and southeast provenance systems. The southern Jinjia provenance system is the main one, which formed largescale braided delta （Jinjia sandbody and Gaoqing sandbody） and turbidite fans located at toe of the delta. The western Gaoqing provenance system formed nearshore sublacustrine fan along fault throw wall, which is located in limited area. The southeast provenance system entered into the study area in the late of Sha 3 period, which converge with the southern provenance system. Sedimentary facies model of braided delta to turbidite is constructed in light of sedimentary characteristics which is similar to the delta model in the Gulf of Mexico. Based on this, we draw a conclusion that turbidite fans are the main play for lithologic traps in this area.

Trap Controlling Factors of StructureLithology Oil/Gas Pool in Eogene of Hongxing Area,Eastern Depression,Liaohe

JIANG Zhen-Hai, LIN Chang-Song, QU Ai-Yang-

2011, 25(4): 635-641.

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There developed several structure oil/gas traps or structurelithology oil/gas traps in delta deposit of Eogene Shahejie Formation and Dongying Formation, Hongxing area. Because of the longalive activity of Jiazhangsi fault, structure or structurelithology oil/gas traps were obviously controlled by Jiazhangsi fault and its associated faults. The study shows that the source rock of Sha 3 Member of Shahejie Formation developed extensively in Jiazhangsi sag, and the system tract of 3rd order sequence or subdistibutry, mouth bar, delta front sheet sandy and transgrasive lacustrine mudstone of 4th order sequence formed 7-8 trapscale reservoir and seal combinations in Sha 1 Member of shahejie Formation and Dong 3 Member of Dongjing Formation, which constitute the basic condition to oil/gas trap. Synsedimentary fault controlled the development and distribution of sandbody. The western fall part of Jiazhangsi fault and NEE direction extended associated faults controlled the sandy distribution developed in different periods. Longalive activity of Jiazhangsi fault connecting to reservoir sand formed the major oil/gas transfer system, along which there formed favorable structure or structurelithology oil/gas traps. Especially, the earlier developed deep senior associated faults make great significance to oil/gas distribution and oil/gas trap development. Most of these senior faults didnt develop in the upper of Sha 1 depositional period, so that oil/gas transferring along these faults tended to assemble at the middle of Sha 1 Member of Shahejie Formation. There was a good combination of reservoir and sealing, and that is why there extensively developed oil/gas trap in middle of Sha 1 Member

Sedimentary Characteristic of Braided River of Upper Jurassic Outcrops in North of Beijing

GUO Jia, DENG Hong-Wen, JI Chun-Hui, QIN Yan-Qun

2011, 25(4): 642-649.

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The sedimentary facies of the Upper Jurassic Houcheng Formation silicified wood outcrops in north of Yanqing area are interpreted jointly with sedimentary structure and characters of sedimentary sequence.This area mainly developed braided river deposits. The main sedimentary microfacies include channel,channel bar,pond and overflow deposits. Two stratigraphic cycles of increasing and decreasing accommodation/sediment supply (A/S) regimes are identified. The two midterm cycles are divided into several shortterm cycles. This paper summarized the characteristics of baselevel cycle, and clarified how the stratigraphic stacking pattern changed with different A/S ratios. The connectivity of channel sand is good under low A/S ratio and vice versa. The thickness of overflow deposits can be seen as the judgment basis of accommodation as it increases with rising A/S ratio.

Origin and Evolution of Ordovician Karst Cave Reservoir in Tahe Oilfield

NIU Yu-Jing, KANG Zhi-Hong, Long-Xu, CUI Wen-Ban

2011, 25(4): 650-659.

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Karst caves, holes and cracks are important oil conductivity to Ordovician fractured reservoir and control the distribution of oil and gas in Tahe oilfield. Karst system of Ordovician reservoir in Tahe oilfield developed from Caledonian to Early Hercynian. Based on the karst origin,evolution and growth mechanism of Tahe oilfield, it is considered that the north area of pinch O3s is the result of karst in Caledonian and Early Hercynian, and the south area of pinch O3s is the result of karst in Caledonian. Utilization of core, drilling, logging and seismic data, the carbonated caved fracture reservoir caves are divided into 4 types: Excavation or dissolution by aggressive fluids; Deposition of allochthonous （externally derived） sediments; Deposition of autochthonous （internal derivation and precipitation） sediments; Collapse at nearsurface and in subsurface. Finally, the article establishes the distribution pattern of carbonated cavedfracture reservoir.

Formation and Evolution of Highquality Dolomite Reservoir in Dengying Formation of Sinian, Nanjiang Area, Sichuan

WANG Dong, WANG Guo-Zhi

2011, 25(4): 660-667.

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The highquality dolomite reservoir of Dengying Formation, Sinian, Nanjiang area, is composed of algal dolomite and grain dolomite formed at tidal flat or grain bank facies, siltfine crystalline dolostones resulted by recrystallization. The existing porosity types are basically secondary pores related to the dissolution and recrystallization, which are intercrystal （dissolution） pores, interparticle dissolution pores, great dissolution pores, stylolite dissolution pores, and lots of survivals karst cavities etc. The studies based on primary and secondary controlling factors indicate that the highquality reservoir is the final products of five evolution stages in the geological history, which is mainly controlled by the meteoric palaeokarstification during hypergene and by the bury dissolution during deep bury. The intensity of palaeokarstification is controlled by the primary sedimentary microfacies and rock types, and the burial dissolution resulted in enlargement or shrinkage of the karst cavities.

Thermal History of Wuerxun Depression in Hailaer Basin，Inner Mongolia

CUI Jun-Beng, LIN Zhan-Li

2011, 25(4): 668-674.

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Wuerxun depression is a sag with a high degree exploration in the south of Hailaer basin, Inner Mongolia. It is the main oilgasbearing depression in which the deposit thickness is big, and the stratum grows entirely, and the oilgenerating condition is very superior. The main source rock is Nantun Formation, and the next is Tongbomiao Formation and Damoguaihe Formation. The average paleogeothermal gradient recovered by the fission track method is about 344 ℃/hm, which is close to present geothermal gradient (33 ℃/hm). The results of paleotemperature and thermal history simulation show that Wuerxun depression has been undergone a heating process since Mesozoic Era, and the maturity of the source rock is controlled by present geothermal field. The geothermal history and illite dating results reveal that the formation of oilgas reservoirs have two stages in Wuerxun depression, which are in the late period of Early Creaceous and since Tertiary, and the late period of Early Creaceous is the main stage, and the second stage is since Tertiary. The source rock began to generate oil and gas in a second peak since Tertiary. The second stage is important for the formation and concentration of oilgas reservoirs in Wuerxun depression.

Numerical Studies of Gas Production from Gas Hydrate Zone Using Heat Injection and Depressurization in Shenhu Area, the South China Sea

HU Li-Tang, ZHANG Ge-Ni, GAO Tong

2011, 25(4): 675-681.

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Based on geologic conditions of natural gas hydrate deposits, this paper used pT+H software and horizontal wells to evaluate gas production strategies including heat injection and combined use of heat injection and depressurization. This paper discussed the change of the saturation of gas hydrate, the saturation of CH4 in gas phase, the production rate of CH4 in gas phase, cumulative CH4 production, and water production when injecting water temperature is 30, 60 and 90 ℃. It was found that the distribution area of low hydrate saturation increases with increasing time and temperature, and the production rate of CH4 increases rapidly within 10 days and then decreases gradually. The results verified the advantages of combine method of heat injection and depressurization, and demonstrated the temperature is not sensitive to the production rate of CH4. It was found that cumulative CH4 volume in Shenhu area is not big mainly because of the low permeability. The findings can provide the references for gas production of natural gas hydrates in Shenhu area, the South China Sea or similar areas.

The Mashan Indosinian Oceanic Island Basalt Outcropping along the Lingshan Fracture in Southeast Guangxi and Its Tectonic Implications

TUN Gen-Yao, LI Yue-Dun

2011, 25(4): 682-691.

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The Mashan Indosinian basalt outcropped along the Lingshan fracture in southeast Guangxi The discriminant diagrams of major elements showed the tectonic setting of the alkali basalt being oceanic island The trace element contents indicated the characteristics of oceanic withinplate basalt The REE patterns of the Mashan Indosinian basalt were a group of subparalled and gently rightinclined curves, with(La/Yb)N= 1169,(Ce/Yb)N=864,(Ce/Sm)N=241, and a tendency of total REE contents increased with increasing of the total alkali contents, which comprehended the Mashan oceanic island should belong to the Azorestype one This provided, firstly, an evidence of geological records from the oceanic basin for that the area of southeast Guangxi and neighbouring southwest Guangdong should be a part of the Paleotethysides, and the Lingshan fracture should be a suture resulted from closure of the Paleotethyan branch oceanic basin Furthermore, the paper represented a work model for evolution of the Lingshan oceanic basin based on the recent fruits of the Paleotethyan study in the border areas of Guangxi and Guangdong

Petrology of the Permian Langmao Basaltic Porphyry, Luquan County, Yunnan Province: Implications for the Petrogenesis of HighTi Basalts

ZHANG Jing, CAO Xiao-Meng, WANG Jia-Lin, ZHANG Qiao-Chong

2011, 25(4): 692-702.

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The Langmao subvolcanic intrusion in the village of Luquan County，Yunnan Province is located in the east of Emeishan large igneous province, which is composed of basaltic porphyries at the lower part and polyphyric basaltic porphyries at the upper part. The wholerock major element analyses show that total Fe2O3 and TiO2 contents are relatively high, from 1405% to 1486%, and 312% to 469% respectively, corresponding to those of highTi basalt. However, there are also some different features in the two rock types: the former is characterized by relatively lower content of SiO2, TiO2, Al2O3, Na2O and relatively higher content of MgO and CaO. Electric microprobe analyses show that the clinopyroxenes, which are relatively rich in iron and titanium, are augite, and plagioclase are andesine and labradorite, whereas titanomagnetites are characterized by extremely high TiO2 content (2425%-2665%). Based on clinopyroxene geothermometer and geobarometer and plagioclase thermometer, the two rock types formed in significantly different temperature and pressure. The temperature and pressure of the basaltic porphyries is estimated to be in the range of 1143-1176 ℃ and 023-086 MPa respectively, whereas those of the polyphyric basaltic porphyries is estimated to range from 1316 to 1370 ℃ and 198 to 225 MPa respectively. In addition, the titanic magnetite with very high XUsp and low Fe3+ in clinopyroxene suggests low oxygen fugacity. The oxygen fugacity is estimated to be 1013×10-6-1013×10-10 Pa. It can be inferred that low oxygen fugacity caused no crystallization of titanic magnetite in the early stage, and resulted in the enrichment of Fe and Ti in the late stage. Conclusively, highTi basalts can be formed from normal lowTi basalts by early crystal fractionation of silicate minerals. However, owing to some Fe and Ti are hosted in clinopyroxene crystals, no very high Fe and Ti enrichment has been recognized in the residual magma, and thus VTi magnetite deposits were not formed in this district.

Magmatic Evolution Processes of Segment II in the Jinchuan Orebearing Intrusion, Gansu Province

LI Shi-Ban, SONG Xie-Tan, HU Rui-Zhong, CHEN Li-Meng

2011, 25(4): 703-711.

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The Jinchuan deposit is the largest NiCu sulfide deposit in China. The intrusion is composed mainly of sulfide peridotite, harzburgite, lherzolite and pyroxenite. Samples for segment II of the Jinchuan intrusion, according to the petrographic observations, combined the analysis of geochemical features of major oxides and trace elements, the paper attempts to research the magma differential evolution in magma rising process. The authors consider that the fractional crystallization process of segment II of the Jinchuan intrusion contain the spinelolivine fractional crystallization in the deep magma chamber and pyroxenite and plagioclase crystallization in the shallow magma chamber, and crustal contamination occur in the whole magma rising processes. In addition, the crustal contamination is the major factors of saturated sulfur. The above magma differentiation evolution supports the mineralization model proposed by Tang Zhongli.

LA-ICP-MS UPb Age of the Monzonitic Granite from Liangkeshu Iron Deposit and Its Geological Implications in Altay, Xinjiang

JIANG Li-Ping, CHAI Feng-Mei, YANG Fu-Quan, LIU Feng, ZHANG Zhi-Xin, GENG Xin-Xia, LV Shu-Jun

2011, 25(4): 712-719.

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The Liangkeshu iron deposit in Xinjiang Uygur Autonomous Region is located in the Kelang basin at the south margin of Altay orogenic belt. It occurs in pegmatite dikes found in the contacts between the monzonitic granite pluton and stratum. LAICPMS zircon UPb method yields a (3767±13) Ma age of granite crystallization. This age indicates that the granite is the product of magmatic activities occurred in late Middle Devonian, meanwhile the age limits that Liangkeshu pegmatite iron deposit formed in late Middle Devonian. The granite has the same tectonic background as the contemporary granite, namely formed in active continental margin environment.

Geological Characteristics and S, Pbisotope Geochemistry of Sareke Copper Deposit in Wuqia County, Xinjiang

LI Zhi-Dan, XUE Chun-Ji, XIN Jiang, WANG Sai-Cheng, GU Zhi-Ye, DAN Hai-Gang, DONG Xin-Feng, SHAO Hang-Lai

2011, 25(4): 720-729.

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Sareke copper deposit in MesoCenozoic sedimentary basins of northwestern margin of Tarim Basin is a largescale deposit. The tectonic location of the deposit is located in the Sarekebayi Mesozoic fault basin, which is seated between the western margin of Tuoyun MesoCenozoic pullapart basin and Late Hercynian deep ocean basin in east Alai. The orebodies, with the layered and lenslike shape, occurred in the gray green conglomerate belonging to the second lithologic section of Upper Jurassic Kuzigongsu Formation. The main metallic minerals are chalcocite and malachite with weak country rock alteration. δ34S of chalcocite is in the range of -240‰~-190‰，indicating that the sulfur are mainly derived from biological reduction of the strata sulfate. The ratio of 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb are 18475~18642, 15606~15676, and 38585~38795，respectively, which illustrate that the oreforming matters are mainly from upper crust and orogenic erosion zone. Geological characteristics and geochemistry of the copper deposit lead to the conclusion that Sareke copper deposit is a basin fluidrelated conglomerate type deposit.

Isotopic Geochemistry of the Tonglushan CuFe Skarn Type Deposit in Hubei Province

WANG Pan-Bo, GU Xue-Xiang, ZHANG Zong-Bao, DONG Shu-Xi

2011, 25(4): 730-739.

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Located in the southeastern Hubei metallographic province of the MiddleLower Yangtze River FeCu metallogenic belt,the Tonglushan CuFe deposit is a typical skarn CuFe deposit in the southeastern Hubei metallographic province. The ore bodies,in the lenticular forms，occur in the contact zone between the marble of 4th 7th Members of the Lower Triassic Daye Group. The oreforming process can be divided roughly into five stages：the anhydrous skarn stage(Ⅰ)，the hydrous skarn stage(Ⅱ)，the oxide stage(Ⅲ)，the quartzsulfide stage(Ⅳ) and the carbonate stage(Ⅴ). Ore minerals mainly include magnetite,chalcopyrite and hematite; gangue mineral include mainly garnet, quartz and carbonate mineral. This paper mainly studied sulfur, hydrogen, oxygen,carbon, lead isotopic compositions and analyzed the indicative meaning of these isotopes to chemistry of the ore fluids and the sources of the oreforming materials and intrusions. The composition of H and O isotopes shows that ore fluids were most likely composed of magmatic water mixed with limited meteoric water at the early oreforming stage and mixed with much meteoric water at the late oreforming stage. Sulfur and carbon isotopic data suggest that the ore forming materials were mainly derived from the deep magma and the carbon was derived subordinately from the dissolution of wall rocks or the mantle. The Pb isotopic composition of ore sulfides are stable and they are ordinary common lead. Ore lead was derived from mantle magma which was subjected to the hybridization of crust materials in the course of intruding upward.

Regularity of Wall Rock Alteration and Mineralization in the Tuanshan Ore Section, Guanfang Scheelite Ore Deposit,Wenshan,Yunnan

ZHANG E-Hui, ZHANG Shi-Chao, FENG Meng-Gang, LIU Xiao-Bei, SUN Qi-Sen, ZHANG Bo

2011, 25(4): 740-749.

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The Wenshan scheelite ore deposit is a mediumlarge skarntype scheelite deposit, which has an intense wall rock alteration and zoning evidently. According to petrography and petrochemistry of alterated rocks, combining with the data of drill hole, three alteration zones are classified from the internal to external zoning of the rock body in the Tuanshan section: phlogopitionepidotization zone→dipsidizationhopfneritation zone→forsteritation zone. Based on transfer amounts of rocks components in all kinds of alteration zones, this paper regards that Al2O3,SiO2, TFe, K2O, Na2O coming from granitic thermal water of magma immigrate and MgO, CaO coming from limestone emigrate in the process of thermal water alteration and scheelite mineralization; therefore, we could draw conclusions: scheelite mineralization mainly occurs in dipsidization and hopfneritation zone; ore body attitude is consistent with dipsidizationhopfneritation zone; scheelitee mineralization is relatively weak inforsteritation zone; mineralization can be only found scattered in the phlogopitionepidotization zone. This research would provide important theory basis for ore deposit metallogenic rule and further searching for mine in Guanfang ore field in Wenshan.

Typomorphic Characteristics of Arsenopyrite in the Bake Gold Deposit, Eastern Guizhou Province

ZHENG Jie, TU Da-Long, Tun-Wen-Meng, Yang-Zhong-Qin, LIU Yang

2011, 25(4): 750-758.

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The Bake gold deposit is characterized by high richness in gold in ore body and widely distributed arsenopyrite in surrounding rocks, which make a clear distinction with other gold deposits of this area. Based on the analysis of the geological background, regional geological conditions of mineralization, oreforming mechanism, by applying theories and methods of minerageny and prospecting mineralogy, using the modern testing technology, the typomorphic characteristics of arsenpyrite in the Bake gold deposit were studied in this paper, achieving important information on the genesis of ore deposits from the view of another point. The results show that goldbearing arsenopyrite in ore bodies have the features of small size, poor crystallinity, unit cell parameters close to the theoretical value, Ntype thermoelectricity, and the mean value of -1956 μV/℃ for pyroelectric coefficient which is significantly lower than that of arsenopyrites adjacent to the surrounding rocks (-1851μV/℃) and that far away from the surrounding rocks (-1746μV/℃). For the chemical compositions, S/As is more than 1, and Fe /(As+S) is less than 05. From the morphology by electron probe observation, arsenopyrite particles are relatively broken, fractures develop, and galenas are filling being associated minerals. The results of rare earth elements and trace elements indicate that, REE contents in arsenopyrite of ore body are obviously lower than those of surrounding rock, and show strong Eu negative anomaly. Ore forming fluids are rich in chalcophile elements and LREEs, lose HFSEs, belong to a fluid system with weak deoxidation and rich Cl. Through the study on Y/Ho, Zr/Hf, Nb/Ta and Co/Ni ratio, Bake gold deposit is inferred to be a magmatic hydrothermal type deposit with medium temperature.

Application of Hyperspectral Remote Sensing on Mineral Exploration in Dongdatan District of East Kunlun,Qinghai Province

ZHANG Zi-Cheng, ZHANG Xu-Jiao, HU Dao-Gong, GAO Mo-Li

2011, 25(4): 759-767.

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Taking Dongdatan district in Qinghai Province as an example, the characteristics and the processing techniques of the Hyperion data are discussed in detail. With methods of SAM, SFF and MF, the hyperspectral data of Hyperion were processed, and the mineral alteration image of Dongdatan district was acquired through the extraction of mineral alteration information from the hyperspectral data using ENVI. The image shows that the mineral alteration assemblages of silicate, carbonate and ferric iron exist at the southeast of the outside body of monzogranite and granodiorite in Moshigou. The field verification of the abnormal alteration was conducted, and the range of mineral alteration is same as what the remote sensing image shows. According to the remote sensing image, a valuable result of mineralization prediction was achieved combining regional geology with mineralization conditions in this region and the optimized target area, and the Dongdatan copper mineralization point was identified. It comes to the conclusion that the hyperion data can provide accurate and reliable information for mineral exploration.

Strain Measurement and Analysis in Matrix of Asymmetric BongShaped Boudinage in Tieshan，Southeast Hubei

TUN Lin-Bei, CENG Zuo-Xun, GAO Xi

2011, 25(4): 768-777.

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Tieshan in southeast Hubei is the first area where boneshaped boudinage was discovered in Asia. To acquire the distributing diagrams of relating parameters such as true differential strain (1-2), kinematic vorticity（Wk） and orientations of the major axes of the finite strain ellipse, the finite strain measurement at different positions in the matrix of asymmetric boneshaped boudinage in this area was carried out by inertia moment ellipse method. It is shown that the finite strain in matrix of the asymmetric boneshaped boudinage is controlled by its competent layer, namely negatively related to the distance away from the competent layer and to the granularity of minerals in the matrix. The finite strain in matrix also shows larger in its thinned sections than that in thickened sections along direction of its elongation. Other structures around the boudin with similar scale could disrupt the distribution of strain in the study matrix. Besides, the study shows that the asymmetric boneshaped boudinage in this area was formed by simple shear parallel to the layer during early period and by pure shear with extension parallel to the layer and contraction perpendicular to it later. Comparison between asymmetric boneshaped boudinage and asymmetric fishhead boudinage of the same area reveals that the pure shear and simple shear in their matrix are corresponding to the relatively thinned sections and thickened sections respectively, and that their differences in shape are mainly related to the difference in competency of minerals filled in their discontinuous sections, which proves that both sorts of boudinages could serve as rheological indicators of rocks.

Gravel Fabric Characteristics of the Neocene Mahui Formation in Yushe Basin, Shanxi and Its Geological Significance

JIAN Cheng, HAN Jian-En, TU Jia, HE Cheng-An, SHU Da-Gang, MENG Xian-Gang, SHAO Zhao-Gang, WANG Jin

2011, 25(4): 778-788.

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Based on the analysis of gravel fabric characteristics of conglomerate layers of the Middle Neogene Mahui Formation in Yushe basin, combined with the lithological study of basin basement and its adjacent mountains, this paper deals with the origins, sources, hydrodynamic conditions, climate environment, geomorphy and tectonics of Yushe basin, Shanxi. The study reveals that Mahui Formation is composed of fluvial and lacustrine basal conglomerate during Neocene, of which three conglomerate layers show better consistency in origins, sources, transport and sedimentary environment. The conglomerate layers of Mahui Formation are multiperiods, multisources and unsteady alluvial and lacustrine sediment, which indicates an environment from drycold to humid. The gravels underwent strongly physical and chemical weathering and some biological action. The main source rocks of the conglomerate are basement strata of the basin and strata located in the eastern, northern and western margin of the basin. Lower content granite gravels were carried over comparatively long distance. Nevertheless, the majority of gravels underwent nearmedium distance transport. A conclusion is drawn that Yushe basin is an intramontane basin formed by relative mountain uplift in the east of Shanxi during the second stage of the Himalayan movement.

Characteristics of Weathering Crust and Formation Environment of Planation Surface in Zhangjiajie

NI Zhi-Yun, YANG Gui-Fang, ZHANG Xu-Jiao, TIAN Meng-Zhong, BENG E-Min, YANG Zhen

2011, 25(4): 789-795.

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This paper characterized the weathering crust and planation surface in Zhangjiajie based on the field investigation, geochemical analysis, and regional comparison. It is indicated that the planation surface formed in humid environment of Late Tertiary Period, followed by the occurrence of erosional surface. Structures of weathering crusts from the planation surface are clear, showing artificial soil, residual layer, semiweathered rock and rock downward. The weathering crust is dominated by high silicon and low aluminum, suggesting the moist and hot environment. On the regional scale, the planation surface in Zhangjiajie at the altitude of 1,100-1,300 m occurred in humid environment of Late Tertiary Period, whilst the lower erosional surface （800-950 m） appeared between the Late Pliocene and Early Pleistocene.

Assessment of Groundwater Specific Vulnerability in Guangzhou Based on Fuzzy Comprehensive Evaluation

YANG Mu-Zhuang, TUN Chao, LI Yan-Jun

2011, 25(4): 796-801.

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Taking into account various factors that may influence the groundwater specific vulnerability, including topography, strata, hydrogeology and human activities, this paper selected 9 indices from these factors, and constructed nonlinear fuzzy membership with method of fuzzy comprehensive evaluation. The membership degrees of these indices were calculated, then the groundwater specific vulnerability in Guangzhou was assessed combining with the GIS technology of spatial analysis. The results indicate that the indices of special vulnerability change in the range of 299-2216, and could be divided into 5 grades. It comes to the conclusion that the groundwater in Guangzhou is easily polluted, and there are much obvious regional differences. It is necessary to take different protecting measures to promote sustainable utilization of groundwater resources in Guangzhou.

Rare Earth Element Fractionation Between Groundwater and Wall Rock in Limestone Aquifer: Sample from Taiyuan Formation Limestone Aquifer in Renlou Coal Mine, Northern Anhui Province

CHEN Song, GUI He-Rong, SUN Lin-Hua, LIU Xiang-Gong

2011, 25(4): 802-807.

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Rare earth element analysis had been carried out for the Taiyuan limestone and limestone water collected from the Renlou coal mine, and the results show that the total rare earth element (REE) contents of limestone are low and are 36947×10-6 in average. The rare earth element patterns indicate that the LREE is rich and the HREE is depleted; the REE contents of limestone water are 00526×10-6 in average; the LREE and HREE both are rich; the fractionation between LREE and HREE is clear. The waterrock interactions in limestone aquifer had been studied, and the results indicate that the LREE content is stable, the fractionation of HREE is clear, and especially that of Y is a peak, the relationship between Y and Ca is positive correlation, the fractionation of Y/Ho, Y/Dy in limestone water is more obvious than in limestone. This paper considers that the peak effect of Y can be the distinguishing basis for limestone water.

Fractal Characteristics and Watercourse Evolution of the Lower Jingjiang Segment in Middle Yangtze River

LUO Yun, HUANG Chang-Sheng

2011, 25(4): 808-812.

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The fractal characteristics were discussed according to the fractal analysis of segments in lower Jingjiang River in this paper. The parameter of dimensions are changing between 1078 to 123 and are lower than those of Yellow River, Haihe River and Luanhe River and close to those of plain areas in lower Yellow reaches and upper Yangtze reaches. The result indicates the evolution of segment is mature period, which is disproportional to other segments of this catchment. This is maybe controlled by its geological settings, especially longterm slow subsidence of JianghanDongting Lake plain. After the watercourse is cut off, the fractal value decreases evidently associated with the simplification of watercourse. The curve cutoff of segment generally occurs between 119 and 123 of dimension. Thus the fractal value can be regarded as an early warning parameter.

Soil Heavy Metal Existence Form in Langfang Area and Its Validity Analysis

CA Kui, LUAN Wen-Lou, SONG Ze-Feng, LI Chao, CHEN Zhi-Xian, GU Hai-Feng

2011, 25(4): 813.

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According to the statistics and analysis on contents of 5 kinds of heavy metal elements such as As, Cd, Cr, Hg and Pb under different forms from 39 samples of root soil in Langfang area, this paper sums up the characteristics of form composition, and analyzes the geochemical behavior of the heavy metal elements in the root soil preliminarily. By using the correlation analysis method, the effective form contents and total contents of 5 kinds of heavy metal elements, pH and TOC of the soil are analyzed to come to a conclusion that the effective form contents of heavy metal elements are not only effected by the total contents, but also closely related to pH and TOC in soil, which provides theoretical basis for studying pollution degree of heavy metal elements of surface soil in Langfang area.

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