2015 Vol. 21, No. 3

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NEW GENERATION 1:5000000 MAP OF REGION STABILITY EVALUATION IN CHINA
DU Jian-jun, MA Yin-sheng, TAN Cheng-xuan, CHEN Qun-ce, SHI Wei
2015, 21(3): 309-317.
Abstract (157) HTML (66) PDF (11906KB)(37)
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Based on the latest research results of neotectonic movements and geological hazards, a new 1:5000000 map of region stability evaluation in China is compiled which uses the theory of modern tectonic movement to evaluate region stability in the comprehensive analysis of basic laws of China's neotectonic movement. The new map aims to further perfect our basic geological data and improve the level of region stability evaluation research, in the service of the construction of major national projects and the regional city group, the western development strategy and the promotion of the northeastern old industrial base, the macroscopic decision of government and the sustainable development of national economy.
DIFFERENCE IN FAULT DEVELOPMENT AND ITS CONTROLLING ON OIL AND GAS ACCUMULATION IN MAICHEN SAG, BEIBUWAN BASIN
HU Ai-yu, CHEN Wei, YU Wen-quan, TONG Heng-mao
2015, 21(3): 318-329.
Abstract (111) HTML (70) PDF (26233KB)(22)
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Using the seismic and drilling data, the development, evolution and origin of the fault system in the east of Maichen Sag were analyzed, and the influence of fault on oil and gas accumulation were discussed in this paper. The results show that the fault combinations and activity characteristics have obvious differences in different regions of Maichen Sag; There are six types of tectonic styles developed, including domino structure, stepped fault, complicated "Y" shaped structure (collapse structure), listric-fan structure, drag structure, and superposed fault; And there are four types of fault activities, including continuous activity, early-activity, midterm-activity and late-activity. The fault system in Maichen Sag are developed in the superposition of multi-periodic rifting with different extension directions (NW-SE extension during E1ch-E2l, NS extension during E3w) under the pre-existing tectonic conditions. The differences of structural styles and fault activities are caused by different distribution and activity of pre-existing structures. The fault system control not only the thickness and distribution of source rock but also the oil and gas migration which impact the oil-gas accumulation model and lead to different oil and gas distribution in Maichen Sag.
DISCUSSION ON THE FRACTURE OF LAYERED ROCK MASS BASED ON THE FINITE ELEMENT METHOD
XU Ke, DAI Jun-sheng, FU Xiao-long, REN Qi-qiang, LIU Cong-ning, ZHAO Yun
2015, 21(3): 330-340.
Abstract (136) HTML (60) PDF (9600KB)(9)
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The failure mode and laws of layered rock mass are unique because of its heterogeneity and anisotropy. By conducting uniaxial, biaxial and three axis compression experiments on layered rock mass and analyzing their stress strain curves, different characteristics have been shown. And then with the software ANSYS, finite element numerical simulation have been done. Comparing stress strain curves and maps of simulation as well as combining the theory of fracture, failure modes and rules of layered rock mass in different stress conditions have been summarized. Finally Futai area was taken as an example to validate the result. This research suggests that the orientations of loads and constraints as well as the rock level are the key factors to rock failure. Rock with strong intensity like limestone would be cracked in priority if stress direction is paralleled to rock level, for stress concentration occurs to the strong rock. While rock with weak intensity like mudstone would be cracked first if stress direction is perpendicular to the rock level. Rock compression experiment, numerical simulation and the example of Futai area have verified this law successfully.
THE MULTI-PARAMETER QUANTITATIVE PREDICTION OF RESERVOIR FRACTURE OF FU-2 MEMBER IN TIAN 96 FAULT BLOCK OF JINHU SAG
ZHOU Ju-biao, SHI Xian-da, DING Yu-sheng, KAN Yan-kun, SHI Xin-yue
2015, 21(3): 341-350.
Abstract (194) HTML (60) PDF (6251KB)(13)
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Based on the theory of strain energy and surface energy, the relationship between the fracture parameters and the ancient and present earth stresses at the fracture forming period in Tian 96 fault block of Jinhu sag was established by using Griffith rock-cracking principle. The type and direction of the ancient earth stress were determined through the structure analysis, and the direction and strength of the present earth stress were calculated by using the method of sound velocity and hydraulic fracturing. The numerical simulation results of the ancient and modern stress field were substituted into the calculating model of fracture parameter to calculate the density, opening, porosity and permeability of the fractures in Fu-2 member in Tian 96 fault block. And the fracture prediction results were verified using the ancient stress field analysis and core statistics. Eventually the main factors that affect fractures development in Tian 96 fault block were analyzed comprehensively.
2015 NEPAL EARTHQUAKE AND THE FUTURE SEISMIC TREND OF HIMALAYA OROGENIC BELT
ZHAO Gen-mo, LIU Jie, WU Zhong-hai
2015, 21(3): 351-358.
Abstract (146) HTML (76) PDF (11688KB)(18)
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This paper briefly introduces the parameters of the M 8.1 earthquake on April 25, 2015, which is a low angle thrust fault movement in the middle of the Himalaya orogenic belt. The characteristics is that the source is very shallow, the intensity of the earthquake reaches to Ⅺ degree and the earthquake damage is severe. The rupture zone have a strike of the North West-South East, crossing the Nepalese capital Kathmandu, where the construction suffered serious damage. The earthquake was the largest earthquake in Nepal since 1934, which marking the end of the period of peace in Himalaya since 1950. Since entering the new active period in 2005, the great earthquake occurred in Nepal has reached the climax of the event in 2015, which is expected to last ten to several decades. According to the analysis of data of historical earthquakes, it may have a migration along the Himalayan zone in the future, and there will be larger earthquake in the eastern part of the Himalayan belt, so as to reach the top of earthquake tide and then have a end. There may be serious damage to the border of India, Bhutan and east-south region of Tibet. It is also possible to move northwardly along with the Himalaya belt in the vertical direction (i.e. horizontal migration), causing destructive earthquakes in Tibet, Qinghai in a few years. It needs to do a good job in monitoring, forecasting, and disaster prevention.
A PROBLEM AND EXPLANATION FOR BOREHOLE STRAIN METER RECORDS OF CO-SEISMIC STRAIN STEPS
DONG Pei-yu, REN Tian-xiang, YANG Shao-hua, PANG Ya-jin, SHI Yao-lin
2015, 21(3): 359-370.
Abstract (189) HTML (64) PDF (8970KB)(10)
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Observation data from 4-compnoent borehole strain meters can be self-checked by Δεεεε. However, when strain meters record the co-seismic strain steps, the Δεε is not often equal to the Δεε, and observed values are greater than the theory solution. In this paper, the possible reasons were analyzed and several models with different initial confining stress and different stress disturbance caused by earthquake wave were established, with the finite element method of "kill element" and transverse isotropic" wounded element" to simulate the tension fracture or shear slip occur between metal cylinder and the cement sheath, and discuss which one is the real reason. The results indicate that tension fracture between the metal cylinder and the cement sheath account for the difference of Δεε and Δεε, and affect the co-seismic strain steps observation. Therefore, some new improved methods are needed when arranging borehole probe in the drilling-hole in order to reduce the observation error in future.
STUDY ON PERMAFROST OF QILIAN MOUNTAINS BASED ON GIS SPATIAL ANALYSIS MODEL
FU Lian-zhen, HU Dao-gong, ZHANG Xu-jiao, YOU Bao-jie, WU Ze-qun, YE Meng-ni
2015, 21(3): 371-377.
Abstract (116) HTML (57) PDF (18966KB)(11)
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Based on those empirical formulas of temperature, permafrost thickness, latitude, longitude and altitude in Qilian Mountains and Tibet Plateau, the distribution characteristics of mean annual temperature, mean annual ground temperature and the thickness of permafrost in Qilian Mountains are obtained by ArcGIS spatial analysis model. The results show the average annual temperature and annual mean ground temperature of the permafrost regions in Qilian Mountains are in the range of -12~-6 ℃ and -4 ~-2 ℃ correspondingly, and the thickness of permafrost varies from 90 to 140 meters. The area with elevation above 4300 m around Hala Lake has the lowest temperature and the thickest permafrost. Its average annual temperature and ground temperature are lower than -10 ℃ and -4 ℃ respectively, and permafrost is thicker than 140 m. Combined with the distribution of hydrocarbon source rock and the permafrost thickness of gas hydrate drilling in Qilian Mountains, the middle of Qilian basin-mountain tectonic zone is believed to be the most favorable area for the gas hydrate reservoir.
EXPERIMENTAL STUDY ON ANISOTROPIC CHARACTERISTICS OF UNDISTURBED Q3 LOESS FROM DINGXI, GANSU
XU Shan-chang, LIANG Qing-guo, LI Shuai-shuai, ZHANG Tang-jie, ZHANG Rong
2015, 21(3): 378-385.
Abstract (124) HTML (39) PDF (4255KB)(8)
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Through the triaxial test in the laboratory, the anisotropy effect of Q3 loess from Dingxi, Gansu on the shear strength and deformation parameters was studied. The results show that the anisotropy of undisturbed Q3 loess has obvious influence on its mechanical properties. The shear strength in vertical direction of the loess is much higher than that in horizontal direction, and with the increase of the confining pressures, the difference between the shearing strengths of the two directions decreases significantly and eventually stabilizes within an error of 10%. When the confining pressure is lower than 100 kPa, the failure strain of the loess in horizontal direction is higher than that in vertical direction, and the difference between the failure strains of the two directions gradually decreases with the confining pressure increases. When the confining pressure is higher than 200 kPa, the failure strains in vertical and horizontal directions tend to be the same. By using Duncan-Chang model, the measured and the calculated deviatoric stresses are compared which indicate that the difference between the vertical direction and the horizontal direction is large in the low strain range, and with the confining pressure increasing, the difference gradually decreases and stabilizes in the error range of 5%. The stress strain curves of the loess samples in both the vertical and horizontal directions show linear relationship with very high regression coefficients when the strain is less than 2%, which can be used to approximately calculate the deformation modulus of the loess samples in both directions, and the corresponding values are 130 MPa and 85 MPa respectively.
EXPERIMENTAL STUDY ON TENSILE STRENGTH OF UNDISTUBED Q2 LOESS FROM YANAN SHANNXI, CHINA
SUN Wei-yu, Liang Qing-guo, YAN Song-hong, OU Er⁃feng, SHAO Sen-lin
2015, 21(3): 386-392.
Abstract (131) HTML (76) PDF (5177KB)(7)
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The unconfined compressive and penetration tensile tests were conducted with different loading rates on undisturbed Q2 loess from Baotashan Tunnel in Yan'an, Shanxi, and the impacts on the unconfined compressive strength and tensile strength were studied. It shows that the loading rates have a great impact on the compressive strength and tensile strength, which all increase with the increase of loading speed. The ratios of height to diameter have a great influence on the tensile strength of the Q2 loess, when the ratio of height to diameter of the samples is about 1.0, the impact on the tensile strength tends to be relatively small. Therefore, when the tensile strength of loess is to be measured by axial unconfined penetration test, the ratio of height to diameter of the samples should be 1.0. Within the scope of the test loading rates, the loading rates have little effect on the ratios of compressive strength to tensile ratio for the undisturbed Q2 loess in Baotashan tunnel, which vary between 9.88 and 13.68.
STUDY ON THE GUANZHUANGYU LOESS STRATIGRAPHY IN MANGSHAN, ZHENGZHOU
WANG Yu-zhen, WANG Shu-bing, WANG Xi-sheng, FU Jian-li, JIANG Fu-chu
2015, 21(3): 393-398.
Abstract (205) HTML (56) PDF (1291KB)(8)
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The thickness of the Guanzhuangyu section in Mangshan is 154.9 m, with the loess-paleosol sequence of S10 and above exposed. The typical malan loess there is coarse grained and uniform with the layer thickness up to 70.125 m, and there is no obvious weakly developed paleosol layer in the middle of this strata. Magnetic stratigraphic measurement indicate that the boundary of B/M is located at the bottom of L8 with the depth of 132.04 m, and the bottom of the profile is not in Jaramillo. Compared with Zhaoxiayu section, it is shown that the heights of the strata below 72 m in both are highly consistent marked by the boundary of B/M, just with different stratigraphic division. However, the magnetic susceptibility values of the stratigraphic unit L1SS1 become apparently higher in Zhaoxiayu section, while there is no obvious change in Guangzhuangyu section. The reason for this phenomenon deserves further research.
GEOLOGICAL STRUCTURE CHARACTERISTICS OF THE NORTHERN SEGMENT OF XUEFENG OROGEN: A CASE STUDY OF THE CILI-ANHUAN CORRIDOR
BAI Dao-yuan, ZHONG Xiang, JIA Peng-yuan, WANG Xian-hui, PENG Yun-yi
2015, 21(3): 399-414.
Abstract (186) HTML (133) PDF (13651KB)(21)
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Cili-Anhuan corridor was taken as examples for studying the geological structure characteristics of the western part of the northern Xuefeng orogen. It is shown that the northern segment of Xuefeng orogen is composed of the northern Wuling fault-bend fold belt and the southern Xuefeng basement detachment belt. There existed main deformation types such as NEE-EW trending folds and thrust faults in the Wuling fault-bend fold belt with minor NE-NNW trending dextral strike-slip faults and NEE-EW trending normal faults. And there existed EW-NE trending folds, EW-NE trending thrust faults and normal faults with minor NE trending strike-slip faults in the Xuefeng basement detachment belt. The deformations in the Wuling fault-bend fold belt were controlled mainly by the northward detachment of the bottom of the Banxi Group and thrust faults. While the deformations in the Xuefeng basement detachment belt were controlled mainly by the detachment and thrust faults cutting through the Lengjiaxi Group fold-basement, with the direction from north to south in overall and then turning to south at the southern margin. The folds and faults in the northern segment of Xuefeng orogen were formed in the compression events of Wuling Movement, Caledonian Movement, Indosinian Movement and Early Yanshanian Movement, following by the extension in Cretaceous, the NE-NNE direction regional compression during middle-late Paleogene and the NW direction compression during late Paleogene-early Neogene. Among which the folds and thrust faults formed in the Caledonian Movement and Indosinian Movement are the most important. There existed back-thrust structures both in the northern segment and the middle-southern segment of Xuefeng orogen, however there existed stronger thrusting, thickening and uplift in the northern segment controlled by the Caledonian regional S-N compression.
TECTONIC DEVELOPMENT AND ORE-CONTROLING CHARACTERISTICS OF XIAOQINLING GOLD FIELD
ZHANG Kai, REN Hong-wei, GUO Gang, TENG Fei, WANG Chen
2015, 21(3): 415-425.
Abstract (218) HTML (181) PDF (36536KB)(50)
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Through analyzing the collected geological data of xiaoqinling gold field, the different levels of exploration engineering on typical ore deposits were studied systematically and the ore-controlling tectonic characteristics of the mine field were discussed. The research shows that under the control of the folds, most auriferous quartz veins are located at the axes or corners of Yangzhaiyu-Dayueping-Jinluoban compound antiform. The development of ore-controlling faults inside the mine field can be divided into three stages: pre-minerogenic faults (the early ductile shear zone), early minerogenic faults (the middle brittle-ductile or ductile-brittle shear zone) and main metallogenic faults (the late brittle fault zone). Accordingly the main ore-controlling faults can be roughly divided into four groups: nearly EW, NE, NW and NS. The sizes of the ore bodies and ore deposits are directly determined by the structural belts and the scale of one single fault in the area, and because of the difference in the tectonic activity stages, tectonic deformation types and strength, the veins are in different occurrence state and the mineralization imbalance phenomenon is widespread. These research results can provide reference for carrying out metallogenetic prediction in large scale in this area.
BLUESCHIST BELT IN CHINA AND ITS TECTONIC SIGNIFICANCE
ZENG Pu-sheng, MA Jing, GOU Rui-tao, WANG Ju-jie
2015, 21(3): 426-437.
Abstract (225) HTML (96) PDF (3545KB)(24)
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On the basis of previous studies, the blueschist belt in China can be divided into 20 parts according to the metamorphic age and original place. This paper selects some typical blueschist belts of different times to discuss their characteristics (such as distribution area, gross scale, the features and formation age of the original rock and mineral combination), and analyze their geological genesis. The generation patterns of China's blueschist belts are complicated, they are all associated with the subduction, and mostly belong to the B-type subduction. Part of regions, however, also are superposed by the A-type subduction which are UHP and HP metamorphic belts (such as Arkin, Dabie belt, Namjagbrawa Subei Myitkyina band, etc.). China's blueschist belts can be divided into four formation ages, which are the Proterozoic (Jinning period), the Paleozoic (Caledonian, Hercynian), the Mesozoic (Indosinian to Yanshanian) and the Cenozoic (Himalayan). And the formation of the blueschist belts in each period are mostly related with the subduction of the ocean basin in the process of China's terrane accretion, and some also are effected by the superposition of the later intracontinental subduction (high-ultrahigh pressure subduction) at some specific areas.
LARGE-SCALE E-W THRUST NAPPES IN JIANCHUAN-HUTIAOXIA AREA, NW YUNNAN, CHINA: A DISCUSSION ON THE BOUNDARY OF THE YANGTZE CRATON AND TIBET-SANJIANG OROGENIC SYSTEM
SHA Shao-li, ZENG Pu-sheng, GOU Rui-tao, DAI Yan-juan, ZHANG Zi-xiong
2015, 21(3): 438-445.
Abstract (292) HTML (146) PDF (2247KB)(24)
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Based on the regional geological survey, the characteristics of the faults in Jianchuan-Hutiaoxia area and the boundary of the Yangtze Craton and Tibet-Sanjiang Orogenic System were discussed. The results show that there exist EW trending large-scale thrust nappe structures in this region. Through the observation of several sections which started from Jianchuan to Baihanchang-Ruhanping and Zhongyi Village in Lijiang, and ended in Hutiaoxia town (Xiatiaotou) in Shangri-La, it is revealed that the stable sequences including Paleozoic and Mesozoic Triassic strata of Yangtze craton are thrust nappes, overlying westward on the strata sequences of the Tibetan-Sanjiang orogenic system, with the thrusting distance over 50 km. Therefore the Jianchuan-Hutiaoxia fault is a narrow tectonic window instead of the boundary of the Yantze Craton and the Sanjiang orogenic system. The Erhai-Jianchuan-Lijiang-Muli fault is suggested as the boundary of the two plates, extending southward to the Red River fault.
EVALUATION OF THE HYDROCARBON GENERATION POTENTIAL OF SOURCE ROCKS OF THE JURASSIC YAOJIE FORMATION IN MULI DEPRESSION OF QILIAN MOUNTAINS
XU Jiu-sheng, WEN Zhi-gang, HU Dao-gong, ZHANG Yao-ling, QI Bang-shen
2015, 21(3): 446-452.
Abstract (173) HTML (104) PDF (3292KB)(38)
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The research results of the abundance, types and maturity of the organic matter of mudstone and coal seam of Yaojie coal-bearing formation in Muri depression of Qilian Mountains show that the mudstone of Yaojie coal-bearing formation is good hydrocarbon source rock and the organic matter type is sapropelic-humic (Ⅱ1) during the mature stage in which gas generation is predominant. While the coal seams are relatively poor hydrocarbon source rocks, with the organic matter of humic type (Ⅲ) at the mature stage, which have a certain hydrocarbon generating potential. Based on the analysis of hydrocarbon source rocks in others formation, it is concluded that the mudstone of Yaojie coal-bearing formation and the lacustrine mudstone of Galedesi formation in late Triassic are the main source rocks of gas hydrates in Muri depression.