Improved Geological Interpretation Using Landsat TM Data in Lancang-Jinghong Area, Yunnan Province, China

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 tech-niques including selected band color composites, principal component analysis and IHS decorrelation stretching are used to improve the discrimination of different lithologicai 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 trans-formed images with available geological data and surface observations, the geological interpretation could be done with satisfactory degree of accuracy.     

Effect and Prospect of Basic Geological Survey Based on Airborne Gravimetry in China

The airborne gravimetry was an important leap and innovation in the world’s history of geophysical exploration. China's first test of the airborne gravity geological survey in the onshore-offshore transitional area of the western and southern part of the Bohai Sea was successful and effective in geology. Based on the airborne gravity data, and combining previous ground gravity, seismic and drilling data etc., we carried out the geological interpretation by forward and inverse methods. The result shows that the airborne Bouguer gravity anomaly was clear, the fracture interpretation was reliable, and the inversion depth of the main geological interfaces was relatively accurate. This airborne gravity geological survey not only filled the exploring gaps in the onshore-offshore transitional area, and realized the geological and tectonic junction between the sea and the land, but also discovered four local gravity anomalies, 11 fractures and three sags or subsags, and so on. The good geological effect of airborne gravimetry not restricted by terrain condition shows that it can be served as a new geophysical method in the exploration of complex terrain physiognomy area such as mountain, jungle, desert, marsh, onshore-offshore transitional area and so on, and has an extensive application prospect in China in the future.     

Influence of the Chuxiong Yao’an Earthquake on the Mineralization of Hot Springs in the Tengchong Geothermal Area, Southwestern China

<正>The Tengchong geothermal area,an active tectonic region with frequent earthquakes,is located in Yunnan Province of southwestern China.This area contains abundant active hot springs, which often display high metal concentrations and obvious mineralization phenomena.At 19:19 on 9 July 2009,an earthquake occurred in Yao'an,Chuxiong,Yunnan Province,which is 300 km to the northeast of the Tengchong geothermal area.We sampled water in the hot springs in the Tengchong area from 4 July to 9 July 2009 and from 10 July to 15 July 2009 to study the changes of elemental concentrations before and after the earthquake and discuss the influence of the earthquake on the mineralization of the hot springs.The concentrations of most trace elements increased slightly,but the concentration of REE(rare earth elements) decreased by 50%after the earthquake in the hot springs around a NS-trending fault.The elemental concentrations remained unchanged in Longtan and Suanshuigou,which are related to an inactive crater.The elemental concentrations in other springs controlled by superficial and small-scale faults decreased after the earthquake.The earthquake can stimulate the activity of deep faults and magma chambers,as is responsible for the increase of metal concentrations in the hot springs along the NS-trending deep fault;whereas it can decrease the porosity of permeable rocks,resulting in the decline of the flux of ore-bearing fluids and the corresponding mineralization in the hot springs related to superficial faults.     

http://www.sciencedirect.com/science/article/pii/S1674987114000292

Aeromagnetic anomaly zonation of the Ordos Basin and adjacent areas was obtained by processing highprecision and large-scale aeromagnetic anomalies with an approach of reduction to the pole upward continuation.Comparative study on aeromagnetic and seismic tomography suggests that aeromagnetic anomalies in this area are influenced by both the magnetic property of the rock and the burial depth of the Precambrian crystalline basement.Basement depth might be the fundamental control factor for aeromagnetic anomalies because the positive and negative anomalies on the reduction to the poleupward-continuation anomaly maps roughly coincide with the uplifts and depressions of the crystalline basement in the basin.The results,together with the latest understanding of basement faults,SHRIMP U-Pb zircon dating of metamorphic rock and granite,drilling data,detrital zircon ages,and gravity data interpretation,suggest that the Ordos block is not an entirety of Archean.     

Separate Analysis of Remote Sensing Information of Structures of Different Geological Periods and Quantitative Study of Corresponding Tectonic Stress Fields

The structural feature shown on a remote sensing image is a synthetic result ofcombination of the deformations produced during the entire geological history of an area.Therefore, the respective tectonic stress field of each of the different stages in the complexdeformation of an area can be reconstructed in three steps: (1) geological structures formed atdifferent times are distinguished in remote sensing image interpretation; (2) structuraldeformation fields at different stages are determined by analyzing relationships betweenmicrostructures (joints and fractures) and the related structures (folds and faults); and (3)tectonic stress fields at different stages are respectively recovered through a study of the featuresof structural deformation fields in different periods. Circular structures and related circlular and radial joints are correlated in space to con-cealed structural rises. The authors propose a new method for establishing a natural model ofthe concealed structural rises and calculating the tectonic stress field by using quantitative dataof the remote sensing information of circular structures and related linear structures.     

Evaluation Methods of Profitable Tight Oil Reservoir of Lacustrine Coquina: A Case Study of Da'anzhai Member of Jurassic in the Sichuan Basin

Based on core observation,cast and fluorescent thin sections,FESEM and ESEM,coquina in Da'anzhai Member of Jurassic in Sichuan Basin were examined systematically.Together with production data and logging evaluation,a method for lacustrine coquina evaluation based on geological theory was established up.In the article,two aspects of the study were elaborated,characteristics of favorable reservoirs,and a"five-step"evaluation method for favorable coquina reservoir.According to the correlation between porosity and production data,porosity is not effective in finding high quality coquina reservoir of this area.Whereas micro research of reservoir samples from a high productivity well revealed that sparry coquina is the best lithofacies,with the most developed micro storage space of various kinds.After the favorable reservoir was sorted out,a five-step method evaluating the coquina reservoir was worked out.Correlation ofGR value and rock types suggests that GR<30 API is an effective evaluation parameter in identifying profitable reservoir lithofacies.Meanwhile,the combination of profitable reservoir rock thickness and production data revealed that the reservoirs with the highest potentiality are those with thickness of 3-18 m.Fractures are more developed in faults,folds and structural noses in the study area.Organic acid is discharged massively before the peak of hydrocarbon generation,leading to the formation of dissolution pores in the reservoir.The evaluation of organic acid was made by using the source rock indexes.After evaluating the four factors,and compiling their distribution maps,the maps were overlapped to predict favorable reservoir zones,and 7 first class and 9 second class favorable zones of coquina were picked out.     

Crustal Structure of the Chuan-Dian Block Revealed by Deep Seismic Sounding and its Implications for the Outward Expansion of the East Tibetan Plateau

The Chuan-Dian Block (CDB) is located in the southeastern margin of the Tibetan Plateau, with a complex geological structure and active regional faults. The present tectonic condition with strong crustal deformation is closely related to the ongoing collision of the India and Eurasia plates since 65 Ma. The study of the crustal structure of this area is key to revealing the evolution and deep geodynamics of the lateral collision zone of the Tibetan Plateau. Deep seismic sounding is the most efficient method with which to unravel the velocity structure of the whole crust. Since the 1980s, 19 deep seismic sounding profiles have been captured within the CDB area. In this study, we systematically integrate the research results of the 19 profiles in this area, then image the 3D crustal velocity, by sampling with a 5 km spacing and 2D/3D Kriging interpolation. The results show the following. (1) The Moho depth in the study area deepens from 30 km in the south to 66 km in the north, whereas there is no apparent variation from west to east. The Pn wave velocity is higher in stable tectonic units, such as 7.95 km/s in the Lanping-Simao block and 7.94 km/s in the western margin of the Yangtze block, than in active or mobile tectonic units, such as 7.81 km/s in the Baoshan block, 7.72 km/s in the Tengchong block and 7.82 km/s in the Zhongdian block. (2) The crustal nature of the Tengchong block, the northern Lanping-Simao block and the Zhongdian block reflects a type of orogenic belt, having relatively strong tectonic activities, whereas the crustal nature of the central Lanping-Simao block and the western margin of the Yangtze block represents a type of platform. The different features of the upper-middle crust velocity, Moho depth and Pn wave velocity to both sides of the Red River fault zone and the Xianshuihe fault zone, reflect that they are clearly ultra-crustal. (3) Based on the distribution of the low velocity zones in the crust, the crustal material of the Tibetan Plateau is flowing in a NW–SE direction to the north of 26°N and to the west of 101°E, then diverting to flowing eastwards to the east of 101°E.     

Potash–Forming Regularity of the Ordovician Marine Northern Shaanxi Salt Basin: Insight from Review and Prospect of the Deep Geology of the Ordos Basin

The Ordovician Northern Shaanxi Salt Basin(ONSSB), located in the east–central Ordos Basin, western North China Craton(NCC), is one of the largest marine salt basins yet discovered in China. A huge amount of halite deposited in the Mid-Ordovician Majiagou Formation, and potashcontaining indication and local thin layer of potash seam were discovered in O2 m65(6 th submember, 5 th member of the Majiagou Formation). This makes ONSSB a rare Ordovician potash-containing basin in the world, and brings new hope for prospecting marine solid potash in this basin. However, several primary scientific problems, such as the coupling relationship between ONSSB and the continent nucleus, how the high-precision basement fold controls the ONSSB, and how the basement faults and relief control ONSSB, are still unclear due to the limitations of the knowledge about the basement of the Ordos Basin. This has become a barrier for understanding the potash-forming regularity in the continental nucleus(CN) area in marine salt basin in China. Up to now, the material accumulation has provided ripe conditions for the answers to these questions. Latest zircon U-Pb ages for the basement samples beneath the Ordos Basin reveal that there exists a continental nucleus(Yi-Meng CN) beneath the northern Ordos Basin. And this brings light into the fact that the ONSSB lies not overlying on the YiMeng CN but to south Yi-Meng CN. Both do not have superimposed relationship in space. And borehole penetrating into the basement reached Palaeoproterozoic meta-sedimentary rocks, which suggests the ONSSB is situated in the accretion belt of Yi-Meng CN during geological history. Basement relief beneath the ONSSB area revealed by seismic tomography and aeromagnetic anomaly confirms the existence of basement uplift and faults, which provides tectonic setting for sedimentary center migration of the ONSSB. Comparative research with various data sources indicates that the expanding strata in the ONSSB adopted the shape of the basement folds. We found that the orientations of the potash sags showed high correlation with those of several basement and sedimentary cover faults in the ONSSB. The secondary depressions are also controlled by the faults. Comparative research between all the global salt basins and continental nuclei distribution suggests that distribution of the former is controlled by the latter, and almost all the salt basins developed in or at the margin of the continental nucleus area. The nature of the tectonic basement exerts a key controlling effect on potash basin formation. And on this basis we analyzed in detail the geological conditions of salt-forming and potash-forming in the ONSSB.     

Effects of Near-Surface Absorption on Reflection Characteristics of Continental Interbedded Strata: the Dagang Oilfield as an Example

<正>Due to the effects of seismic wave field interference,the reflection events generated from interbedded and superposed sand and shale strata no longer have an explicit corresponding relationship with the geological interface.The absorption of the near-surface layer decreases the resolution of the seismic wavelet,intensifies the interference of seismic reflections from different sand bodies,and makes seismic data interpretation of thin interbedded strata more complex and difficult. In order to concretely investigate and analyze the effects of the near-surface absorption on seismic reflection characteristics of interbedded strata,and to make clear the ability of current technologies to compensate the near-surface absorption,a geological model of continental interbedded strata with near-surface absorption was designed,and the prestack seismic wave field was numerically simulated with wave equations.Then,the simulated wave field was processed by the prestack tune migration, the effects of near-surface absorption on prestack and poststack reflection characteristics were analyzed,and the near-surface absorption was compensated for by inverse Q-filtering.The model test shows that:(1) the reliability of prediction and delineation of a continental reservoir with AVO inversion is degraded due to the lateral variation of the near-surface structure;(2) the corresponding relationships between seismic reflection events and geological interfaces are further weakened as a result of near-surface absorption;and(3) the current technology of absorption compensation probably results in false geological structure and anomaly.Based on the model experiment,the real seismic data of the Dagang Oil Field were analyzed and processed.The seismic reflection characteristics of continental interbedded strata were improved,and the reliability of geological interpretation from seismic data was enhanced.     

Geological Fluid Mapping in the Tongling Area： Implications for the Paleozoic Submarine Hydrothermal System in the Middle-Lower Yangtze Metallogenic Belt, East China

The Tongling area is one of the 7 ore-cluster areas in the Middle-Lower Yangtze metallogenic belt,East China,and has tectonically undergone a long-term geologic history from the late Paleozoic continental rifting,through the Middle Triassic continent-continent collision to the Jurassic-Cretaceous intracontinental tectono-magmatic activation.The Carboniferous sedimentary-exhalative processes in the area produced widespread massive sulfides with ages of 303-321 Ma,which partly formed massive pyrite-Cu deposits,but mostly provided significant sulfur and metals to the skarn Cu mineralization associated with the Yanshanian felsic intrusions. To understand the Carboniferous submarine hydrothermal system,an area of about 1046 km~2 was chosen to carry out the geological fluid mapping.Associated with massive sulfide formation,footwall sequences 948 m to 1146m thick,composed of the Lower Silurian-Upper Devonian sandstone,siltstone and thin-layered shale,were widely altered.This hydrothermal alteration is interpreted to reflect large- scale hydrothermal fluid flow associated with the late Paleozoic crustal rifting and subsidence.Three hydrothermal alteration types,i.e.,deep-level semiconformable silicification(S_1),fracture-controlled quartz-sericite-pyrite alteration(S_(2-3)),and upper-level sub-discordant quartz-sericite-chlorite alteration(D_3),were developed to form distinct zones in the mapped area.About 50-m thick semiconformable silicification zones are located at～1-km depth below massive sulfides and developed between an impermeable shale caprock(S_1)and the underlying Ordovician unaltered limestone. Comparisons with modern geothermal systems suggest that the alteration zones record a sub-seafloor aquifer with the most productive hydrothermal fluid flow.Fracture-controlled quartz-sericite-pyrite alteration formed transgressive zones,which downward crosscut the semiconformable alteration zones, and upwards grade into sub-discordant alteration zones that enveloped no economic stringer- stockwork zones beneath massive sulfides.This transgressive zone likely marks an upflow path of high- flux fluids from the hydrothermal aquifer.Lateral zonation of the sub-discordant alteration zones and their relationship to overlying massive sulfide lenses suggest lateral flows and diffusive discharging of the hydrothermal fluids in a permeable sandstone sequence.Three large-sized,14 middle-small massive sulfide deposits,and 40 massive sulfide sites have been mapped in detail.They show regional strata- bound characters and two major styles,i.e.,the layered sheet plus strata-bound stringer-style and the mound-style.Associated exhalite and chemical sedimentary rock suites include(1)anhydrite-barite,(2) jasper-chert,(3)Mg-rich mudstone-pyrite shale,(4)barite lens,(5)siderite-Fe-bearing dolomite,and (6)Mn-rich shale-mudstone,which usually comprise three sulfide-exhalite cyclic units in the area. The spatial distribution of these alteration zones(minerals)and associated massive sulfides and exhalites,and regional variation inδ~(34)S of hydrothermal pyrite and inδ~(18)O-δ~(34)C of hanging wall carbonates,suggest three WNW-extending domains of fluid flow,controlled by the basement faults and syn-depositional faults.Each fluid domain appears to have at least two upflow zones,with estimated even spacing of about 5-8 km in the mapped area.The repeated appearance of sulfide-sulfate or sulfide-carbonate rhythmic units in the area suggests episodically venting of fluids through the upflow conduits by breaking the overlying seals of the hydrothermal aquifer.     

Metallogenic Epoch and Ore-forming Environment of the Lamasu Skarn-porphyritic Cu-Zn deposit, western Tianshan,Xinjiang, NW China

Granitic rocks, widely developed in the Lamasu copper ore region, western Tianshan were formed at 390.5±7.7 Ma according to the SHRIMP zircon U-Pb dating of the plagioclase granite porphyry. Based on the regional tectonic evolution and published chronological data of both diagenesis and mineralization, the Biezhentao- Kokirqin region was rolled into the orogen associated with the closure of Yili Ocean during early Devonian. The N-S-trending thrust faults were formed during this period and accompanied by the intrusion of granitic rocks. On this stage, the paleo-Asian Ocean Plate entered into the early collision orogenic phase and the plagioclase granite porphyry intruded （390.5±7.7 Ma） and replaced with limestone of the Mesoproterozoic Kusongmuqieke Group, Jixianian System and formed the early phase of skarn-type copper mineralization in the Lamasu region. Furthermore, the subduction-melting of Bayingou Ocean Plate during Carboniferous generated a deep-seated magmatic chamber in the Lamasu copper ore region which located in the northwestern part of the Paleozoic Biezhentao-Kokirqin island arc. The magmatic chamber segregated Cu-bearing magmas, which transported upward to the shallow earth crust along the faults or fractures and formed the Cu-hosting porphyry. According to the research on the characteristics of the ore deposit and the ore-forming environment as mentioned above, the Lamasu Cu-Zn deposit was characterized by the superposing of mineralization at different geological settings and it was skarn-porphyritic type.     

http://www.sciencedirect.com/science/article/pii/S1674987113000029

The Preandean geological configuration of the eastern North Patagonian Massif is established through the use of geological and geophysical analysis.The positive gravity anomalies located near the Atlantic coast are due to 535 and 540 Ma old rocks belonging to the Pampean Orogeny （Precambrian-middle Cambrian）,which are widely recognized in central and northern Argentina.The Famatinian Cycle （Ordovician-Devonian） is represented by a Silurian-Devonian marine basin equivalent to those of eastern-central Argentina and South Africa,and which was deformed at the end of the Devonian byan～E-W to WNW-ESE compressional event,part of the Famatinian Orogeny.Containing strong gravity gradients,the NW-SE belt is coincident with fault zones which were originated during the Gondwanide Orogeny.This event also produced NW-SE overthrusting of the Silurian-Devonian sequences and strike-slip faults that displaced blocks in the same direction.This deformation event belongs to the Gondwanide Orogeny that includes movements related to a counterclockwise rotation of blocks in northern Patagonia.The strong negative anomalies located in the western part of the area stem from the presence of rocks of the Jurassic Ca（n）adón Asfalto basin interbedded in the Marifil Complex.These volcaniclastic sequences show mild deformation of accommodation zones in a pre-Jurassic paleorelief.     

New Zircon U‐Pb Ages of Granitic Rocks in Northeastern Jiagedaqi of the Da Hinggan Mountains and their Significance

正Objective The research area is located in the north of the Xing'an block and within the Ali River-Zhalantun granite belt in the eastern part of the Xingmeng orogenic belt.The geotectonic setting and geological evolution history of this area are complex with strong magmatic activity and extremely developed granite rocks.Since predecessors     

Estimation of the Cenozoic Strike-slip Displacement for Major Faults in the Liaodong Bay Depression and its Geological SignificanceEI北大核心CSCD

Estimation of the strike-slip displacement of faults in basins or covered regions has always been a hot and knotty issue. Based on the fine interpretation of 3D seismic data, we estimated the strike-slip displacements of the Cenozoic evolutionary stages of the main faults in the Liaodong Bay Depression, and analyzed their geological significance, using methods of physical modeling experiments and structural analysis. The results showed that two thirds of the strike-slip displacements of the major faults were converted into the horizontal displacement of those secondary extension faults in the Liaodong Bay Depression. It should be noted that the Liaodong Bay Depression isn't a pure strike-slip basin, and its Cenozoic evolution also influenced by extension, thus, extension amount produced by mantle upwelling should be detracted. Strike-slip movements were generated in the depositional stage of the first and second members of the Shahejie Formation, and the strike-slip displacements of major faults in different evolution stages vary considerably. In terms of the Cenozoic cumulative strike-slip displacement, the displacement of faults in the Liaozhong Sag is the largest, followed by those in the Liaodong Sag, and those in the Liaoxi Sag is the smallest. Among all of the faults, the Liaozhong1 fault had the largest strike-slip displacement. As to the displacement in different stages, the strike-slip displacement of all major faults showed the largest displacement in depositional stage of the Dongying Formation. The Neogene strike-slip displacement of faults is bigger than that of the depositional stage of the first and second members of the Shahejie Formation in the Liaoxi region, while it showed an opposite trend in the eastern Liaodong Bay Depression. The difference of relative strength between extensional and strike-slip stress controlled the difference of structural styles and basin structures in different evolution stages and structural locations in the Liaodong Bay Depression. The Cenozoic strong strike-slip effects in the Liaozhong and Liaodong Sag were presented by the obvious strike-slip characteristics on major faults and structural styles. In the Liaoxi Sag, the obvious “extension strike-slip” superimposed structural style was caused by the extension effects in the early Paleogene and strike-slip effects of the Dongying Formation and Neogene. © 2018, Science Press. All right reserved.     

Characteristics and Formation Mechanism of Polygonal Faults in Qiongdongnan Basin,Northern South China Sea

Based on high-resolution 3D seismic data,we document the polygonal faults within the Miocene Meishan (梅山) Formation and Huangliu (黄流) Formation of the Qiongdongnan (琼东南)basin,northern South China Sea.Within the seismic section and time coherent slice,densely distributed extensional faults with small throw and polygonal shape were identified in map view.The orientation of the polygonal faults is almost isotropic,indicating a non-tectonic origin.The deformation is clearly layer-bounded,with horizontal extension of 11.2% to 16%,and 13.2% on average.The distribution of polygonal faults shows a negative correlation with that of gas chimneys.The development of polygonal faults may be triggered by over-pressure pore fluid which is restricted in the fine-grained sediments of bathyal facies when the sediments is compacted by the burden above.The polygonal faults developed to balance the volumetric contraction and restricted extension.The product of hydrocarbon in the Meishan Formation may have contributed to the development of the polygonal faults.In the study area,it was thought that the petroleum system of the Neogene post-rift sequence is disadvantageous because of poor migration pathway.However,the discovery of polygonal faults In the Miocene strata,which may play an important role on the fluid migra-tion,may change this view.A new model of the petroleum system for the study area is proposed.     

The Crustal Structure and Assembly of Terranes in the Qaidam-Qilian-Beishan Area, Western China

Through a study of the geotransect from Golmud to Ejin Qi published recently, the tectonics of the crust beneath the area from the northern Qinghai-Tibet plateau (Qaidam and the Qilian Mountains) to the border between China and Mongolia and its structure, composition and tectonic evolution have been revealed, and abundant information about the deep structures has been provided. Based on the research into the geotransect, it is suggested that the crust in this area was formed by the assembly of the terranes in different geological stages. Following the formation of the Palaeo-Asian continent, the north part of the corridor of the transect became a part of the huge unifying continent by the end of the Early Permian. In the Mesozoic and Cenozoic, as a result of the compression mainly by the push of the Qinghai-Tibet plateau on the south, the unique crustal structure and geomorphologic features on the northern Qinghai-Tibet plateau were formed. This geotransect together with the Yadong-Golmud geotransect co     

Three-Dimensional Density Distribution and Seismic Activity along the Guxiang–Tongmai Segment of the Jiali Fault, Tibet

The Guxiang–Tongmai segment of the Jiali fault is situated northeast of the Namche Barwa Syntaxis in northeastern Tibet. It is one of the most active strike-slip faults near the syntaxis and plays a pivotal role in the examination of seismic activity within the eastern Himalayan Syntaxis. New study in the research region has yielded a 1:200000 gravity dataset covering an area 1500 km2. Using wavelet transform multiscale decomposition, scratch analysis techniques, and 3D gravity inversion methods, gravity anomalies, fault distributions, and density structures were determined across various scales. Through the integration of our new gravity data with other geophysical and geological information, our findings demonstrate substantial variations in the overall crustal density within the region, with the fault distribution closely linked to these density fluctuations. Disparities in stratigraphic density are important causes of variations in the capacity of geological formations to endure regional tectonic stress. Earthquakes are predominantly concentrated within the density transition zone and are primarily situated in regions of elevated density. The hanging wall stress within the Guxiang–Tongmai segment of the Jiali fault exhibits a notable concentration, marked by pronounced anisotropy, and is positioned within the density differential zone, which is prone to earthquakes.     

Evolution, Migration, Controlling Factors and Forming Setting of Mesozoic Basins in Western Shandong

The distinctive topography in western Shandong province consists of several NW-WNW-trending mountain ranges and intervening basins. Basins, in which late-stage sediments to the south have progressively overlapped the earlier sediments and ＂basement＂ rocks of the hanging-wall block, are bounded by S-SW-dipping normal faults to the north. Basin analysis reveals the Jurassic-Cretaceous sedimentary rocks accumulated both within the area of crustal extension and during extensional deformation; they contain a record of a sequence of tectonic events during stretching and can be divided into four tectonic-sequence episodes. These basins were initially developed as early as ca. 200 Ma in the northern part of the study area, extending dominantly N-S from the Early Jurassic until the Late Cretaceous. Although with a brief hiatus due to changes in stress field, to keep uniform N-S extensional polarity in such a long time as 130 Ma requires a relatively stable tectonic controlling factor responsible for the NW- and E-W-extensional basins. The formation of the extensional basins is partly concurrent with regional magmatism, but preceded magmatism by 40 Ma. This precludes a genetic link between local magmatism and extension during the Mesozoic. Based on integrated studies of basins and deformation, we consider that the gravitational collapse of the early overthickened continental crust may be the main tectonic driver for the Mesozoic extensional basins. From the Early Jurassic, dramatic reduction in north-south horizontal compressive stress made the western Shandong deformation belt switch from a state of failure under shortening to one dominated by extension and the belt gravitationally collapsed and horizontally spread to the south until equilibrium was established; synchronously, the normal faults and basins were developed based on the model of simple-shear extensional deformation. This may be relative to the gravitational collapse of the Mesozoic plateau in eastern China.     

Engineering Geological Study of Regional Tectonic Stability in the Area of the Longyang Gorge Power Station on the Huanghe (Yellow) River

In the stability study of the regional structures in the area of the Longyang Gorge Hydroelectrical Power Station, a model of the current stress-deformation field of the area was constructed based on analyses of available data of regional surveys and historical earthquakes and field investigations of active faults and ancient earthquakes. This model was examined and verified by physical and mathematical simulation experiments, and quantitative relations and data were obtained.     

Development of Geological Data Warehouse

Data warehouse (DW), a new technology invented in 1990s, is more useful for integrating and analyzing massive data than traditional database. Its application in geology field can be divided into 3 phrases: 1992-1996, commercial data warehouse (CDW) appeared; 1996-1999, geological data warehouse (GDW) appeared and the geologists or geographers realized the importance of DW and began the studies on it, but the practical DW still followed the framework of DB; 2000 to present, geological data warehouse grows, and the theory of geo-spatial data warehouse (GSDW) has been developed but the research in geological area is still deficient except that in geography. Although some developments of GDW have been made, its core still follows the CDW-organizing data by time and brings about 3 problems: difficult to integrate the geological data, for the data feature more space than time; hard to store the massive data in fifferent levels due to the same reason; hardly support the spatial analysis if the data are organized by time as CDW does. So the GDW should be redesigned by organizing data by scale in order to store mass data in different levels and synthesize the data in different granularities, and choosing space control points to replace the former time control points so as to integrate different types of data by the method of storing one type data as one layer and then to superpose the layers. In addition, data cube, a wide used technology in CDW, will be no use in GDW, for the causality among the geological data is not so obvious as commercial data, as the data are the mixed result of many complex rules, and their analysis needs the special geological methods and software; on the other hand, data cube for mass and complex geo-data will devour too much store space to be practical. On this point, the main purpose of GDW may be fit for data integration unlike CDW for data analysis.