2014 Vol. 20, No. 1

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STUDY ON METALLOGENIC PROGNOSIS FOR GOLD POLYMETALLIC DEPOSITS IN HAINAN ISLAND BASED ON EVIDENCE WEIGHTING METHOD
WU Chuan-jun, XU De-ru, GUO Tao, ZHOU Ying-chun, HOU Mao-zhou, ZHOU Yue-qiang
2014, 20(1): 1-15.
Abstract (178) HTML (110) PDF (3158KB)(10)
Abstract:
Based on systematical analysis of regional metallogenic regularity of gold polymetallic deposits in Hainan Island, multivariate favorable geological evidences such as strata, structure, magmatic rock, aeromagnetic, geochemical exploration, and remote sensing data were analyzed and extracted. With the help of MRAS, the authors established an evidence weight prediction model for gold polymetallic deposits in this area. The study area was divided into 2 km×2 km grid units at first and then the posterior probability of every grid unit was calculated. According to the magnitude of evidence weight and the distribution characteristics of mineral resources, the study area was classified into 3 A-level prospective targets, 4 B-level prospective targets and 24 C-level prospective targets. Research results showed that about 90% deposits were located in metallogenic prospective area showing a good prediction effect, which provided an important scientific basis for prospecting work in this region.
DISCUSSION ON DEVELOPMENT MODELS OF THE SHEARING FRACTURES IN FAULT BEND FOLDS
ZU Ke-wei, ZENG Lian-bo, ZHAO Xiang-yuan, LIU Guo-ping
2014, 20(1): 16-24.
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Abstract:
This paper focuses on a typical section of fault-bend fold in Kuqa foreland basin, by use of the shear fractures data measured in different structural position of the outcrop, and the fractures development laws are analyzed and then development models of the shearing fractures in fault-bend fold in Kuqa foreland basin are established. Statistical result shows that the shear fractures in the outcrop can be divided into two types: shear fractures at a high angle to layers extensively develops in each position in the outcrop, and bed-parallel fractures presenting near the fault, mainly develops near the fault with attitudes changing with the deformation of the layers. The intensity of shear fractures development decreases with the distance away from the fault as a whole. The gradient of shear fractures development in the footwall has a greater descending rate than that in the hanging wall. The density of shear fractures in the hanging wall is greater than that in the footwall. The density of shear fractures in the hinge of the fold is less than that in the forelimb and backlimb, besides higher density appears in the internal surface with respect to that in the external surface. The change of the dip angle in the fault bendfold causing the alteration of the movement for the hanging wall makes the stresses concentrating on the axial faces. So the phenomenon of the increase of intensity of shear fractures near this position can be appeared. The development model of shear fractures in the fault-bend fold shall be separated into 3 stages: regional fractures are mainly developed before the generation of fault; after the formation of the fault with dragging deformations near not obvious, new shear fractures will be formed in the position where the axial surface pinned at the lower ramp inflection point passes through, one at a high angle to the layer and the other at a low angle to the fault; the bed-parallel fractures will be presented in the curved sections and the intensity of fractures development near fold hinge is higher than that in two limbs, when the dragging deformations are obvious. The study on the model of shearing fractures development has a guiding significance for exploring the law of fractures development and prospecting the fractured reservoir in the foreland basin, especially in the deep layers with complex tectonic style.
ACTIVITIES OF PALEOGENE FAULTS IN LANGGU SAG, JIZHONG DEPRESSION
ZHANG Dan-dan, DAI Jun-sheng, ZOU Juan, WANG Ke
2014, 20(1): 25-35.
Abstract (130) HTML (77) PDF (3413KB)(13)
Abstract:
By calculating the fault throw index and growth index of the active faults in Langgu sag, Jizhong depression, the fault throw figures and fault growth index figures of this sag in each geological time were drawn out. Research showed that Daxing fault had different activities at different locations. The activity was weakened gradually from the southwest to the northeast as a whole. During the sedimentary period of Ek to Es4, the three-level active faults were mainly located in the southeastern part of the sag, and were active weakly. During the sedimentary period of Es3 to Es2, the distribution of active faults was gradually extended to northeast from the southeastern part of the sag, with intense faults activity. The results suggested that the activity of active faults in Paleogene was mainly controlled by structural evolution background, and the activity of other active faults was also influenced by Daxing Fault.
RESEARCH ON CARBONATE MICROFACIES IN MIOCENE ZHUJIANG FORMATION IN EAST PEARL RIVER MOUTH BASIN
FENG Lin, DENG Min, WEI Zhe, ZENG Yi, ZHOU Xiao-kang
2014, 20(1): 36-47.
Abstract (176) HTML (124) PDF (4328KB)(15)
Abstract:
Based on the microscopic observation and description of Paleontological characteristics and lithological features about the 1483 carbonate conventional or the casting thin sections, which come from the Miocene Zhujiang Formation in East Pearl River Mouth Basin, judging by our study of their particles, textures and structures, the carbonate rock of Zhujiang Formation can be divided into 8 main microfacies types, and according to their grain types and relative amount, these main microfacies can further be divided into 22 primary microfacies types. On the basis of the longitudinal combination features and environmental significances of these microfacies types, the carbonate rock of Zhujiang Formation can be divided into 6 sedimentary facies: carbonate ramp, restricted flatform, open platform, platform-margin shoal, platform margin reef and fore-platform slope. The vertical evolution of sedimentary facies reveals that, Dongsha uplift experienced the evolution from carbonate ramp to carbonate platform in the process of sea level rise in the early-Miocene.
RESEARCH ON SEDIMENTARY FACIES OF THE ZHENZHUCHONG SEGMENT IN THE LOWER JURASSIC ZILIUJING FORMATION IN JIULONGSHAN REGION, NORTHWEST SICHUAN BASIN
JIANG Wen-jian, HOU Ming-cai, MA Hua-ling, LI Yong, WANG Wen-kai
2014, 20(1): 48-60.
Abstract (141) HTML (129) PDF (5021KB)(16)
Abstract:
Based on the single factor analysis and multifactor comprehensive mapping method, a detailed study of the Jiulongshan region Zhenzhuchong segment lithology, sedimentary structures, fossil plants characteristics had been carried out. Combining with logging data analysis, the author studied the sedimentary facies and the plane distribution feature in-depth, discussed its evolution, and established sedimentary facies development patterns in the region. The result showed that the sedimentary facies in Jiulongshan region during Zhenzhuchong segment sedimentary period was a fan delta wetland, and it developed a positive cycle of the sequence, which provided guidance to oil and gas exploration in the region.
GENESIS AND SOURCES OF NON-CONVENTIONAL WATER SOLUBLE METHANE GAS IN GUSHI SAG
LIU Jian-chao, ZHANG Lin, WANG Xing-yun, BAI Jian-feng, FENG Long
2014, 20(1): 61-69.
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Abstract:
The genetic types of water soluble methane gas in Gushi sag in Weihe Basin were studied. Research on carbon isotope δ13C1 and content of heavy hydrocarbon in water soluble gas methane showed that the genetic types of water soluble methane gas in different formations were different. Water soluble gas in Neogene Zhangjiapo Formation was mainly biogenetic. It came from biological decomposition of dark grey muddy limestone with higher content of carbon, which was self-generated and self-reserved. Water soluble methane gas in the Lantian-Bahe Formation was mainly immature coal-type pyrolysis gas (coal humic pyrolysis gas), which came from the lower layer. Analysis of the carbon isotope of CO2 showed that δ13CCO2 < -10‰, being typical crust source type of organic origin. This proved that the water soluble methane and CO2 in the Lantian-Bahe Formation came from the lower strata. Combining the above results and ethane carbon isotope analysis, the authors concluded that the biogenetic pyrolysis gas probably existed in the lower strata.
QUANTITATIVE EVALUATION OF CRUSTAL STABILITY ALONG THE BAOSHAN-RUILI SECTION OF DALI-RUILI RAILWAY AND ITS ADJACENT REGION
GUO Chang-bao, ZHANG Yong-shuang, QU Ke, XIONG Tan-yu, FU Xiao-xiao, DU Yu-ben
2014, 20(1): 70-81.
Abstract (147) HTML (65) PDF (4409KB)(21)
Abstract:
The Dali-Ruili Railway is located near the India and Eurasian plate's collision belt, where the geologic structure conditions are very complicated. The railway planning and constructions are restricted by the complex engineering geological problems related to the crustal stability, such as active fault, high geo-stress, rock burst of deep tunnel, large deformation of soft rock. This paper make the crustal stability zoning assessment on the basis of crustal stability influencing factors analysis, including the geological background, new tectonic movement, crust uplift rates, potential seismic source area analysis, tectonic stress field, engineering geological characteristics of rock and soil mass, as well as the geological hazards characteristics. The AHP method based on GIS was used in the analyzing process. As a result, the crustal stability is divided into 4 grades: stable area, relatively-stable area, relatively unstable area and unstable area. 88 zoning sections are made along the Baoshan-Ruili section of Dali-Ruili Railway and its adjacent region. According to the zoning result, there are 19 crustal stability zoning sections along the recommended C12K scheme, including 9.79% of unstable area, 46.71% of relatively unstable area, 36.7% of relatively-stable area, and 6.18% of stable area. The regional crustal stability assessments have some important significance for the railway construction and line optimization.
CHARACTERISTICS OF PALEOTECTONIC STRESS FILED ON THE AILAOSHAN STRUCTURAL BELT
WANG Ming-liang, ZHANG Jia-gui, WANG Xin-wen, LUAN Qiu-lei
2014, 20(1): 82-93.
Abstract (200) HTML (97) PDF (4066KB)(18)
Abstract:
By observing and recording structural feature and deformation of the Ailaoshan Group in the field at Mosha and Jiasa, the stress filed shall be preliminarily divided into two stages: the ductile deformation and brittle deformation. Based on the structural analysis of the stress field for all sorts of small structures, such as schistosity, cleavage, fold, tectonic lens, scratch and the conjugated joints, etc. in the field, it reveals that there exists two tectonic stress fields in the Ailaoshan structural belts, with main stress orientations of NE-SW and NW-SE compressions. The present stress filed sustains the paleotectonic stress filed. Combing with the previous research results, the dynamic sources of two different tectonic stress fields on the Ailaoshan belt are studied briefly, which may be critically linked to its peripheral plates and deep fluid extrusion.
ANALYTICAL TECHNIQUE OF HORIZONTAL MAXIMUM PRINCIPAL STRESS FOR PETROLEUM ENGINEERING
CHEN Zhao-wei, YANG Xiang-tong, WANG Gang, YUAN Xue-fang, LIU Jun-yan, ZHOU Peng-yao, BA Dan
2014, 20(1): 94-102.
Abstract (145) HTML (99) PDF (2898KB)(21)
Abstract:
Fundamental principles on determination of horizontal maximum principal stress from wellbore damage information were summarized systematically. On the basis, analysis procedure for horizontal maximum principal stress was established. A field example was analyzed, and the procedure showed that the method had a reliable theoretical evidence, clear analysis procedure, and simple operation. The promotion of its application to petroleum industry in China is recommended.