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2009 Vol. 20, No. 6

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Zircon SHRIMP U-Pb Dating and Neoproterozoic Metamorphism of Kangding and YuanmouIntrusive Complexes, Sichuan and Yunnan
李大鹏, 陈岳龙, 罗照华, 赵俊香
2009, 11(6) doi: 10.1007/s12583-009-0076-2
Abstract:
To clarify the relationship of the metamorphic intrusions along the west margin of the Yangtze craton and their metamorphic history after crystallization, the petrochemical and trace element geochemical characters, zircon SHRIMP U-Pb dating, and the chemical compositions of coexisting hornblendes and plagioclases from Neoproterozoic metamorphic intrusions in Kangding (康定), Sichuan (四川) Province, and Yuanmou (元谋), Yunnan (云南) Province, were studied. Combined with the former published data, it is indicated that the Kangding granitic plutons and Yuanmou complex in the west margin of the Yangtze craton generally formed at the same period. Metamorphic event at ~700 Ma existed extensively, at least covering from Kangding area in Sichuan to the Eshan (峨山) area in Central Yunnan. Moreover, amphibolite facies may represent the peak regional metamorphic condition.
Clay Rocks around Permian–Triassic Boundary at Daxiakou Section in Hubei Province, China
张素新, 袁鹏, 赵来时, 童金南, 杨浩, 于吉顺, 史玉芳
2009, 11(6) doi: 10.1007/s12583-009-0077-1
Abstract:
We studied the clay rocks around the Permian–Triassic boundary at the Daxiakou (大峡口) Section in Xingshan (兴山), Hubei (湖北) Province, China. All clay rocks are predominated by illite- montmorillonite (I/M) mixed-layer minerals, and high-temperature hexagonal bipyramid (HB) quartz and pyrite are contained in different abundances. Clay microspheres are even found in some beds. The results show that volcanic activity was very frequent in this area or in the neighboring areas during the Permian–Triassic transition though the intensity of eruption and the position of the eruption center might have varied during the period. The frequent volcanic activity should be at least one of the leading events to cause the momentous turnover of biota and the ecosystem during the great Permian–Triassic transition.
Hemipelagic Deposition of the SilurianKepingtage Formation in Tarim Basin and ItsSedimentologic Significance
姜在兴, 王玥, 魏垂高
2009, 11(6) doi: 10.1007/s12583-009-0079-z
Abstract:
Hemipelagic contourites were interpreted in the Silurian Kepingtage (柯坪塔格) Formation in the Tarim basin, Northwest China, through studies of outcrop, core, well-log, and seismic data. They are characterized by thin to thick bedded mudstone, with contour current irregularly thin bedded-lentiform siltstone and sandstone. Chitin stone, graptolite, thin-shelled bivalve, dissoconch, and acritatch fossils are present in dark-colored mudstones. A Helminthopsis-Scolicia trace fossil assem-blage was observed in the outcrop and drilling core. Sandstones are mainly well-sorted and subangular- subrounded sublitharenite. Sedimentary structures include oriented current structure, erosional sur-face, and small-scale cross stratifications. The potential of contourites as hydrocarbon source and res-ervoir rocks was evaluated on the basis of previous interpretations of paleoclimate and paleosalinity.
Sequence Stratigraphic Analysis of the FirstLayer, Upper Second Submember, ShahejieFormation in Pucheng Oilfield
张金亮, 江志强, 李德勇, 孙婧
2009, 11(6) doi: 10.1007/s12583-009-0078-0
Abstract:
In view of the high accuracy and predictability, high-resolution sequence stratigraphy had been extensively applied to oil exploration and gotten prominent practicable results. This article takes the first layer, upper second submember, Shahejie (沙河街) Formation from Pucheng (濮城) oilfield as an example to analyze the application of high-resolution sequence stratigraphy in reservoir study on the basis of a comprehensive study of core log data. Firstly, facies analysis of this area reveals the corresponding terminal fan system occurring where sediment-laden streams decrease in size and vanish as a result of evaporation and transmission losses...
Ce Anomalies of the Yangtze Region, South China, through the Ordovician and Silurian Transition
严德天, 张丽琴, 李双建
2009, 11(6) doi: 10.1007/s12583-009-0087-z
Abstract:
Systematic Ce anomalies for whole-rock have been obtained from the shale-dominated, continuous, and pelagic sedimentary sequences spanning the Ordovician/Silurian (O/S) boundary at the Tieshui (铁水) of Xiushan (秀山), Chongqing (重庆), South China. Ce anomalies across the O/S boundary are recognized in three intervals, Wufeng (五峰), Guanyinqiao (观音桥) and Longmaxi (龙马溪). The calculated Ce/Ce* values of Wufeng Formation range from 0.84 to 0.96 (avg. 0.90). In the Guanyinqiao Formation, the values of calculated Ce/Ce* range from 0.73 to 0.85 (avg. 0.79). The Ce/Ce* values of uppermost Longmaxi Formation range from 0.87 to 0.96 (avg. 0.91)...
Syndepositional Fault Controlling on Depositional Filling of the Third Member of Shahejie Formation in Beitang Sag
黄传炎, 王华, 肖敦清, 陈思, 王家豪, 廖远涛
2009, 11(6) doi: 10.1007/s12583-009-0080-6
Abstract:
In the continental lake basin whose structures were extraordinarily active, tectonism is an important factor in controlling the sequence and the depositional filling of the basin. This article reports the assemble patterns of syndepositional fault in the third member of Shahejie (沙河街) Formation in Beitang (北塘) sag. The results show that the comb-shape fracture system and the fracture transformation zone were developed in Beitang sag. These assemble patterns obviously controlled the sand-body and spatial distribution of sedimentary system. However, the steep slope belt of fault terrace, the multistage slope belt and the low uplift gentle slope belt controlled the development of sequence styles. Analyses of the spatial-temporal relationship of the assemble pattern of syndepositional faults vorable exploration zone.
Geochemical Evidence of Gas Sources of CO2-Rich Cold Springs from Wudalianchi, Northeast China
毛绪美, 王焰新, 王逊
2009, 11(6) doi: 10.1007/s12583-009-0081-5
Abstract:
CO2-rich cold springs occur near the active volcanoes at Wudalianchi (五大连池), Northeast China. The springs are rich in CO2, with HCO3- as the predominant anion and have elevated contents of total dissolved solid (TDS) (>1 000 mg/L), Fe2+ (>20 mg/L), Sr (>1 mg/L), and dissolved Si (>20 mg/L). The compositions of escaped and dissolved gases of the springs are similar. The δ13C values of escaped gases and dissolved gases in mineral springs at Wudalianchi vary from -8.77‰ to -4.53‰ and -8.24‰ to -5.26‰, while δ18O values vary from -10.68‰ to -7.65‰ and -10.30‰ to -8.84‰, respectively, indicating the same upper mantle origin of CO2 of escaped gases and dissolved gases in the springs. Carbon and oxygen isotope fractionations and water-CO2 exchange were weak in the process of groundwater flow...
Landslide Prediction Based on Wavelet Analysis and Cusp Catastrophe
李长冬, 唐辉明, 胡新丽, 李东明, 胡斌
2009, 11(6) doi: 10.1007/s12583-009-0082-4
Abstract:
During the monitoring engineering of landslides, the monitoring data of accumulated displacement are usually affected by the external factors. Therefore, the displacement curve always has step-like character, which brings some difficulties to the accurate prediction of landslides. In order to solve this problem, based on the wavelet analysis and cusp catastrophe, a new kind of analysis method is proposed in this article. First, Fourier transform method can be used to extract the frequency com-ponent of the curve of monitoring displacement...
Modeling of Borehole Radar for Well LoggingUsing Pseudo-spectral Time Domain Algorithm
林树海
2009, 11(6) doi: 10.1007/s12583-009-0084-2
Abstract:
In this article, numerical modeling of borehole radar for well logging in time domain is developed using pseudo-spectral time domain algorithm in axisymmetric cylindrical coordinate for proximate true formation model. The conductivity and relative permittivity logging curves are obtained from the data of borehole radar for well logging. Since the relative permittivity logging curve is not affected by salinity of formation water, borehole radar for well logging has obvious advantages as compared with conventional electrical logging. The borehole radar for well logging is a one-transmitter and two-receiver logging tool...
Characterization of Fault Zones byAnalysis of Aftershock Waveform Data
李红谊, 李松林, 赖晓玲
2009, 11(6) doi: 10.1007/s12583-009-0083-3
Abstract:
Large property contrasts between materials in a fault zone and the surrounding rock are often produced by repeating earthquakes. Fault zones are usually characterized by fluid concentration, clay-rich fault gouge, increased porosity, and dilatant cracks. Thus, fault zones are thought to have re-duced seismic velocities than the surrounding rocks. In this article, we first investigated the synthetic waveforms at a linear array across a vertical fault zone by using 3D finite difference simulation. Syn-thetic waveforms show that when sources are close to, inside, or below the fault zone, both arrival times and waveforms of P- and S-waves vary systematically across the fault zone due to reflections and transmissions from boundaries of the low-velocity fault zone...
Computation of Magnetic Anomalies andGradients for Spatial Arbitrary PostureRegular Body
洪东明, 姚长利, 郑元满, 郭伟, 骆遥
2009, 11(6) doi: 10.1007/s12583-009-0085-1
Abstract:
In the interaction computation for 3D gravity and magnetic anomalies due to arbitrarily shaped homogenous magnetized polyhedron model composed of triangular facets, there are many difficult points, such as mass computing, absence of a mature computer technique in 3D geological body modeling, inconvenient human-computer interaction, hard program coding, etc.. Based on the for-mulae of the magnetic field due to horizontal regular bodies, and by applying forward theory with the three-dimensional Cartesian coordinate system transformation, the forward problems of magnetic anomalies and gradient tensors for arbitrary slantwise regular bodies were solved. It is shown that the magnetic calculating expressions of the arbitrary posture regular body are corrected by comparing results with the homogeneous polyhedral body model outcome data...
Logging Evaluation Method of Low Resistivity Reservoir—A Case Study of Well BlockDX12 in Junggar Basin
陈力群, 邹长春, 汪中浩, 刘海军, 姚爽, 陈冬
2009, 11(6) doi: 10.1007/s12583-009-0086-0
Abstract:
The Hutubi (呼图壁) River reservoir of well block DX12 is a lithologic hydrocarbon reservoir that is under tectonic settings. The main oil-bearing sand body in this area is thin and has a poor transverse connectivity. Because of the complexity of the oil-water relationship, the oil reservoir presents a low resistivity feature, which brings great difficulties to hydrocarbon reservoir identification. This article develops an effective method of well log interpretation that can meet the requirement of low resistivity reservoir well logging evaluation...
Estimation of Depth to Salt Domes from Normalized Full Gradient of Gravity Anomaly andExamples from the USA and Denmark
曾华霖
2009, 11(6) doi: 10.1007/s12583-009-0088-y
Abstract:
We present an estimation of depth of anomalous bodies using normalized full gradient (NFG) of gravity anomaly. Maxima in the NFG map can locate the bodies and indicate their depth. Model calculation using a sphere and application of the NFG method to gravity anomalies over salt domes in the USA and Denmark shows effectiveness of the method. However, the accuracy of depth estimation strongly depends on the number of term N in the Fourier series used to calculate the NFG. An optimum N for the calculation can be given from a test.