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    10 June 2015, Volume 29 Issue 3
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    tectonics and stratigraphy
    Synthetical Analyses of  the Formation and Deformation of the Beiling Syncline in Fangshan, Beijing
    LI Dong-xu
    2015, 29(3):  481-493. 
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    The crescent-shaped Beiling syncline is a main structural feature in Zhoukoudian, Beijing, reflecting a very special structural deformation. Originally, it was only the superimposition of a Late Paleozoic continental basin and a Jurassic continental basin, which responded to the tectonic evolution of the North China Plate, but then it experienced the Yanshan Period fold deformation due to the local stress field produced by the Fangshan granodiorite emplacement. The formation process of the syncline is different from what is told about either fold mechanism or tectonic superimposition in general textbooks. This syncline actually occurred in a complicated system which involved deposition, deformation, magmatism, and metamorphism. Therefore, its origin can be better understood only through the thinking line of system theory, that is, by seeing local and seemingly unrelated structural details as parts of a system.

    Engineering Geology and Environmental Geology
    A New Solution for Finite Strain Measurement by Fry Method in the CorelDRAW Platform
    HAN Yang-guang，YAN Dan-ping，LI Zheng-lin
    2015, 29(3):  494-500. 
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    Finite strain measurement is a major means to estimate quantity ductile deformation. Fry method, using deformed grains such as deformed gravels, oolites and rounded or sub-rounded crystals which can be easily identified in the field and labs as strain markers, is a commonly used means of finite strain measurement. The traditional process of this method is notoriously time-consuming, which prevents it from widely-using. Associated computer programs have been designed previously, but the related machine languages are already out of date. CorelDRAW is a widely-used drawing software, the updated version of which provides VBA for designing Macro-programs. This paper reports a macro-program on CorelDRAW platform, the Program FRY-1, for finite strain measurement of Fry method. This program will help us to rapidly obtain the value of R (long/short axes ratio) and the direction of the longer axle of strain ellipsoid with much higher precision. The efficiency and accuracy of this method are testified by comparing the result with that by the “neighbor center-to-center ” method.

    Secondary Joints in Columnar Area of High Island Formation in Sai Kung, Hong Kong
    ZHU Qing-bo，YANG Zhu-liang，JIANG Yang，ZHOU Xiao-hua，WANG Cun-zhi，JIN Guo-dong
    2015, 29(3):  501-513. 
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    The columnar jointed High Island Formation are widely distributed in the Sai Kung volcanic rock region of the Hong Kong Global Geopark. It is the largest columnar jointed rhyolitic porphyroclastic lava in the world. On the basis of field geological investigation, we study the secondary joints in the columnar area of High Island Formation, and investigate the structural deformation characteristics and process. The secondary joints in the columnar area can be divided into steep-dip longitudinal joints and gentle-dip horizontal joints. The former are with the characteristics of conjugate shear joints, which formed in the extrusion environment of multi directions. The latter cut the former structural foliation, developed into normal slip faults, which formed in the environment of gravitational collapse. The columnar was obviously reformed by the secondary joints. The stress inversion of conjugate shear joints reveals the rapid tectonic transition in about 140 Ma. The principal compression stress changed direction from NE-SW to NW-SE, associated with the structure activities of the Lianhuashan fault.

    Polybaric Crystallization of Granitic Magmas and Its Dynamic Significance: A Case from the Fangshan Pluton of Beijing
    LIU Xiao-li，CHENG Su-hua，ZHANG Hong-yuan
    2015, 29(3):  514-528. 
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    The Fangshan pluton exposed in Beijing is one of the typical Yanshanian intermediate-acidic calcalkaline intrusions occurred in the eastern part of North China Craton. For better understanding of the emplacement mechanism and the uplift-erosion history of the Fangshan pluton, we use the suitable Al-in-hornblende geobarometer to estimate the pluton’s emplacement pressure, and the hornblende-plagioclase geothermometer to calculate the temperature of crystallization. The results show that the Fangshan pluton crystallized at the temperature of 655.9-733.7 ℃ and the pressure of (0.39-0.28)±0.06  GPa. Based on the p-t conditions of the pluton crystallization, it is proposed that the Fangshan pluton experienced polybaric crystallization during the emplacement. The p-t estimations for emplacement, integrating with the characteristics of rock structure and the zircon U-Pb ages of the lithological units of the Fangshan pluton, suggest that the Fangshan pluton has experienced slow-rate erosion/uplift during the early epoch of emplacement, followed by a rapid erosion/uplift epoch related to the emplacement of the lithologically dominated granodiorite unit. Overall, the p-t conditions estimated by this study suggest that the uplift distance of the Fangshan pluton during the emplacement is 7-8 km, and the average erosion/uplift rate for the pluton is in range of 2.33-2.67 km/Ma.

    Geochronology,Geochemistry and Tectonic Significance of  Huamugou Highly Fractionated I-type Granitoid Pluton in  Northern Yili Block, Western Tianshan
    WANG Yong-wen1,2，YAN Dan-ping1，LIU Hong-xu1,2，PAN Cheng-yu2，CHEN Feng1,2，MENG Yu
    2015, 29(3):  529-541. 
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    The Tianshan orogenic belt experienced a subduction and split plots during Late Paleozoic. Records of granite magma records provide important constraints on timing of subduction. The geochemical and chronological results show that Huamugou pluton is consistent with highly fractionated I-type granite of high silicon, rich alkali, poor iron. Ba, Sr, P, Ti are poorly concentrated and Cs, Rb, U, K are well concentrated. Pb isotope studies suggest crustal source with added mantle material. The LA-ICP-MS zircon U-Pb dating on zircons yields age of (330.2±5.7) Ma, belonging to the late Early Carboniferous. These geochemical characteristics indicate that the Huamugou pluton formed in a continental arc setting. Northern Tianshan oceanic crust still southward subducted in the late Early Carboniferous and Junggar plate is not collided with Yili plate, which shows that the Tianshan region is in the subduction stage.

    Thermoelectric Characteristics and Trace Element Characteristics of Pyrite from Kangguer Gold Deposit in Eastern Tianshan of Xinjiang and Its Geological Significance
    XU Jie-hui1, GE Wen-sheng1，XING De-chao2，CHEN Xiao-dong1，SONG Wen-jie2，YU Wen-li
    2015, 29(3):  542-552. 
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    The Kangguer gold deposit is controlled by brittle ductile shear zone in Eastern Tianshan, Xinjiang. Based on genetic mineralogy theory, the pyrite which is main mineral loaded gold has been studied systematically on the typomorphic characteristics by the mineralogy and mineral geochemistry methods. The results revealed that thermoelectric properties of pyrites are mainly of the N type,N-P type and P-N type.From the top of the orebody to the bottom (1,000 m→400 m), P-type thermoelectric coefficient occurrence rate shows a marked decline (37.04%→9%).The calculations of pyrite thermoelectric coefficient indicate that the temperature of the deposit is about 75.43-382.79 ℃,with most values in the range of 80-340 ℃. By analysing the contour vertical projections of gold grade and occurrence rate of P-type pyrite in the L2-2 east mine section of Kangguer gold deposit, it can be inferred that there is good exploring prospect below 400 m elevation of line 22, also in the west of line 22. By studying contour vertical projection of trace elements assemblies (As+Sb+Se+Te，Cu+Pb+Zn and Co+Ti+Ni+Cr) in pyrites, it suggests that great prospecting exists under 400 m elevation of the exploration line 22 and 14. All the typomorphic characteristics of the pyrite mentioned above are very significant for deep gold prospecting in Kangguer gold deposit.

    Characteristic of Fluid Inclusions in Jisong Pb-Zn Deposit in South Tibet and Its Geological Significance
    YIN Yuan，LIANG Wei，XIE Jin-cheng，ZHANG Ji-jun
    2015, 29(3):  553-562. 
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    The Jisong Pb-Zn deposit is located at the east of Himalaya orogenic belt. The ore-bodies are quartz-calcite-sulfide veins and mainly controlled by NE faults. The ore mineral assemblage is sphalerite,galena, and a little pyrrhotite, chalcopyrite. The gangue minerals include quartz, calcite, arsenopyrite and pyrite. It can be divided into four stages: Ⅰ.arsenopyrite-pyrite-quartz stage; Ⅱ.pyrrhotite-sphalerite-galena-chalcopyrite-quartz stage; Ⅲ.quartz-calcite-pyrite stage;Ⅳ.supergene oxidation stage. Fluid inclusions in quartz and calcite are dominant in vapor-liquid two-phase inclusion, and also include a small amount of CO2-H2O inclusions with a few pure liquid ones.The ore-forming fluid is characterized by medium-low temperature, low salinity and low density that homogenization temperature ranges between 225 ℃and 345 ℃ and the salinity varies from 0.21% to 11.93% NaCl eqv in the stage Ⅰ,145-339 ℃ and 0.35% to 13.26% NaCl eqv in the stage Ⅱ,210-350 ℃ and 0.35% to 15.31% NaCl eqv in the stage Ⅲ, respectively. All characteristics of fluid inclusions indicate that fluid-boiling during the mineralization stage may be the major cause of ore material precipitation. Analysis supports that Jisong deposit is a medium-low temperature hydrothermal vein-type Pb-Zn deposit.

    Ore-controlling Characteristics of Fault Structures and Their Relations to Mineralization at Fulechang Zn-Pb Mining District in Deposit Concentration District of Northeastern Yunnan, China
    Lv Yu-hui1,2,3，HAN Run-sheng 1,2，REN Tao1,2，QIU Wen-long1,2，RANG Hao1,2，GAO Yua
    2015, 29(3):  563-575. 
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    The Fulechang Zn-Pb deposit is one of the typical deposits at the southeastern region in the deposit concentration district of Northeastern Yunnan. In this paper, the geological characteristics for faults of different trends and phases and their relations to mineralization have been systematically elucidated based on large-scale mapping and the dynamics theory and method of tectonic ore-forming processes. Typical faults are selected for identification of the mechanical nature of fault planes and for division into tectonic episodes and tectonic systems. The area experienced EW-trending compressive stress from the Jinning period to the Chengjiang period, NW-SE-trending extrusion from the Indosinian period to the early Yanshanian and NE-SW-trending tectonic process from the mid-late Yanshanian to the Himalayan period. At first, the primary stress process from the Indosinian to the early Yanshanian provided a favorable metallogenic geological background; and NE-trending compressional-shear faults and NW-trending tensional faults twist made metallogenic fluid filling, enrichment and mineralization; then EW-trending shear faults are ore-breaking structure. Based on the relationship between structure and mineralization, the research provides important evidences for forecasting concealed deposits or ore-bodies.

    Implications of Precambrian Unconformity to Basement Paleo-uplift and Its Tectonic Evolution of Bachu-Markit Area, Tarim Basin
    CHEN Gang1,2，TANG Liang-jie1,2，YU Teng-xiao3，GUO Ying1,2，YUE Yong3， LI Jiu-mei1,
    2015, 29(3):  576-583. 
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    An unconformity analysis method is provided to study the basement paleo-uplift of Bachu-Markit area, Tarim basin. On the basis of regional tectonic and sedimentary evolution of previous research, we divided the Precambrian top surface to angle unconformity, nonconformity, overlap unconformity and parallel unconformity through the recognition of well data and seismic data. The four types of unconformity reflect rift, basement paleo-uplift, slope and depression, respectively. Furthermore, the distribution of unconformity has a gradual transition pattern, which is arrangement from nonconformity, overlap unconformity to conformity. We consider that the north boundary of basement paleo-uplift is Tumuxiuke fault zone and that the south boundary is possibly Tiekelike zone. Therefore, it could be affirmed that the main part of paleo-uplift is located in Markit area and the southern Bachu area; that the slope of paleo-uplift is distributed in present southwestern Tarim depression and the northern Bachu area. The tectonic evolution of basement paleo-uplift can be divided into 3 stages, which are gentle Precambrian archicontinent stage, final Precambrian uplifting stage and Early-Middle Cambrian subsidence stage. As a whole, the paleo-uplift is gentle at the south and steep at the north in Precambrian; while it is contrary in Early-Middle Cambrian, which controls the strata development and distribution of Nanhuaian-Sinian and Early-Middle Cambrian.

    Control of Boerjianghaizi Fault on Gas Accumulation of Upper Paleozoic in Northern Ordos Basin
    LI Wei-lian1,2，JI Wen-ming1,3，LIU Zhen1,2，LEI Ting1,2，ZHU Jing-yu1,2
    2015, 29(3):  584-590. 
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    In order to reveal the control functions of Boerjianghaizi fault on natural gas accumulation of Upper Paleozoic in Hangjinqi block of the northern Ordos Basin, the history of the fault activity, the lateral and vertical sealing ability of the fault were studied by using fault growth index evolution, fault shale gouge ratio method and fault connectivity probability method through seismic and drilling data of this area. Then Boerjianghaizi fault effects on the natural gas enrichment zones were discussed. The results showed that Boerjianghaizi fault had three obvious peaks of activity in the history of evolution, which were Caledonian to Early Hercynian fracture period, Indosinian to Early Yanshanian squeezing thrust fault activity period, and Mid-late-Yanshanian strike-slip tearing activity period. Mid-late-Yanshanian strike-slip tearing activity period matched well with the main stage of gas accumulation of Upper Paleozoic. It was pointed out that sealing ability of Boerjianghaizi fault had the characteristics of “horizontal sectioning, vertical layering”. In the horizontal direction, Boerjianghaizi faults were divided into lateral migration fault areas and lateral sealed fault areas according to the shale gouge ratio (SGR) which equals to 0.3 as the dividing line. In the vertical direction , the fault plane was vertically sealed in Upper Shihezi and Shiqianfeng formations because the fault sealing coefficients were almost less than 1.0 in the section, while the fault plane was vertically open in Lower Shihezi and Shanxi formations because the fault sealing coefficients mostly range from 4.0 to 10.0 in the section. Meanwhile, in the lateral migration fault areas, natural gas generated from the main source areas which were in the south side of Boerjianghaizi fault was transmitted in the vertical and lateral direction through the fault, then natural gas accumulated in large amount in the north side of the fault easily, but in the lateral sealed fault areas, it is easy to find the natural gas pools in the south side of the fault.

    “Cabbage” Tectonic Characteristics and Its Relations to Hydrocarbon in Northeast Qikou Sag
    HUANG Sheng-bing，LIU Li-fang，LI Hong-yi，CHEN Shao-ping，CHEN Jian-hua
    2015, 29(3):  591-598. 
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    With the advance of exploration and development of seismic data quality，we discovered a tectonic style called “cabbage” structure in Qibei and Shaxi tectonic zone of Qikou Sag. Applying the geometric characteristics，stratigraphic distribution，fault type and the migration of flower’s centre，we have made clear of the formation mechanism and hydrocarbon enrichment of “cabbage” structure in the two zones. The results show that the “cabbage” structure in Qibei tectonic zone formed in the period of neotectonic movement. Shaxi tectonic zone controlled by extension has experienced three stages，including extrusion uplift，thermal subsidence and neotectonic movement. The difference of tectonic evolution leads to the difference of hydrocarbon accumulation. Qibei tectonic zone has the characteristics of late-stage accumulation. Mid-shallow strata is favorable section. Meanwhile Shaxi tectonic zone has two periods of reservoir-forming，the middeep strata is favorable section as the influence of thick shale in Dongying Formation.

    Carbonate Sequence Structure and Microfacies Distribution of the Middle and Lower Ordovician in Northwestern Tarim Basin
    HAN Jian-fa1，WANG Qing-long2，CHEN Jun1，LIN Chang-song3，SONG Yu-bin1， XU Jun-bo1，
    2015, 29(3):  599-608. 
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    The high-resolution sequence structure and depositional model of Yingshan and Yijianfang formations were established by the study of outcrops in Shuinichang of Keping and Dabantage of Bachu in northwestern Tarim Basin combined with 3-D seismic data in Tazhong area. Carbonates in the Middle and Lower Ordovician (Yingshan and Yijianfang formations) can be divided into 2 composite (second-order) sequences (CS1 and CS2), in which CS1 is composed of 2 third-order sequences and CS2 contains 3 third-order sequences. In addition, 17 to 19 high-frequency cycles or fourth-order sequences were also identified. Based on macro sedimentary structure and micro characteristics of the outcrops,9 kinds of microfacies and 4 kinds of microfacies combination were concluded to reflect the specific sedimentary environment and reef building characteristics, which contain reef-beach complex, bioclastic beach, intraclastic beach, lagoon and interbank sea. Furthermore, the evolution of microfacies combination was revealed in the sequence structure. Sq1 and Sq2 consist of lagoon and interbank sea with strong evaporation, in which the dolomite and its transition types are common and the bioclast particles are not found. In Sq3 a thick intraclastic beach is developed, and a few bioclasts appear. On the top of Sq4, a middle-thin layer of bioclast beach emerges. In Sq5, the reef-building organism is blooming and consequently the reef-beach complex becomes to be the dominant facies of Yijianfang Formation.

    Sequence Stratigraphy Framework and Depositional System Distribution of Fuyu Reservoir in Shuangcheng Area, Northern Songliao Basin
    DENG Qing-jie1,2，HU Ming-yi1,2，HU Zhong-gui1,2，WU Yu-kun3
    2015, 29(3):  609-622. 
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    Based on core observation, combined with 135 exploration wells data, various sedimentary microfacies signs were identified. All these showed that Fuyu reservoir mainly developed meandering river-shallow water delta depositional system in Shuangcheng area, Northern Songliao Basin, furtherly divided into 5 subfacies and 11 microfacies. With the guidance of high resolution sequence stratigraphy, using the technologies of rock-electric combination, well-seismic combination and so on, several sequence boundaries were identified. Fuyu reservoir can be divided into 2 long-term base level hemicycles and 7 middle-term base level cycles, and in this way, isochronous sequence stratigraphy framework has been established. Taking middle-term base level cycle as compilation unit, combined with the analysis of seismic attribute, lithofacies paleographic maps in different period were compiled and depositional model was established. Research show that Fuyu reservoir in study area mainly experienced two evolutionary stages: during the period of Q3-sq1—Q4-sq1, shallow delta plain gradually converted to meandering river; while during the period of Q4-sq2—Q4-sq3, meandering river depositional system converted to delta plain subfaceis and delta front subfacies. All these reflected a lake retreat-lake transgression depositional process during which the sedimentary water is firstly shallowing then gradually deepening. The results of above studies provide an important guidance for recent oil and gas exploration.

    Sea-Level Relative Movement of Middle Permian Wujiatun Formation in Eastern Inner Mongolia: Evidence from Mudstones Geochemistry
    MING Cheng-dong1，HOU Du-jie2，ZHAO Xing-min3，SONG Jian4，DENG Jian3，WU Sai-sai3
    2015, 29(3):  623-632. 
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    Through studying the ICP- MS trace elements and organic geochemistry of the Middle Permian Wujiatun Formation mudstones in eastern Inner Mongolia, it indicates that Wujiatun Formation mainly belongs to semi-salt water sedimentary environment; the range of palaeosalnity is 16.6‰ to 28.7‰. The paleosalinity and the change of water depth are showed by the trace elements and their ratios, which are impacted by the relative change of sea- level. Palaeosalinity and relative change of sea-level have a good correlation with sedimentary facies evolution. Using the quantitative calculation palaeosalinity and the values of Sr/ Ba and B/Ga which reflect the paleosalinity and the water depth, the curve of relative change of sea-level of Wujiatun Formation was established. The Wujiatun Formation had undergone two transgression-regression cycles and the transgressions took place in the bottom and middle part of Wujiatun Formation. According to the geochemical index of V/(V+Ni) values, rare earth element Ceanom and saturated hydrocarbon gas chromatogram, combined with sedimentary facies analysis, showed that main body of Wujiatun Formation was formed in a neritic shelf environment characterized by reductive conditions, which is conducive to the preservation of organic matter and development of hydrocarbon source rock.

    Characteristics of Mudstone Compaction and Paleo-pressure Restoration  of Chang 7 Shale in the Middle of Shanbei Slop
    LIU Jing-jing，LIU Zhen，ZHU Wen-qi， HU Xiao-dan
    2015, 29(3):  633-643. 
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    The undercompaction increment of Chang 7 shale is not great in the middle of Shanbei Slope, so the power of the hydrocarbon migration in Chang 7 is suspected. However, the characteristics of pressure today, does not reflect the pressure when hydrocarbons were accumulating. Firstly, this paper, based on the mudstone compaction curve, made a study on the characteristics of mudstone compaction in the middle of Shanbei Slope, Ordos Basin. The results show that the mudstone compaction sections are all composed of normal compaction and abnormal compaction. Although the undercompaction increment is not great, the phenomenon of undercompaction is widespread in this area. There is a better consistency among the normal compaction tendencies, and the acoustic travel time on the surface for wells is about 320 μs/m. The initial depths of undercompaction for present compaction section gradually increase from east to west. However, after restoring the largest burial depth, the initial depths of undercompaction distribute between 2,250 m and 2,400 m. Secondly, this paper restored the paleo-porosity and predicted the paleo-pressure of the source rock bed (shale in Chang 7) when hydrocarbons were accumulating. The phenomenon of overpressure is widespread in Chang 7 shale during the period of accumulation, especially in the southern part of the area, and the maximum pressure coefficient is 1.56, which reflects a strong hydrocarbon expulsion power in the source rock during that time. The pressure mainly ranges from 17 MPa to 28.5 MPa, and the pressure coefficient mainly ranges from 1.12 to 1.56. They have the same distribution, with the characteristics of northeastward-decreasing, and it could well explain the distribution of reservoirs in the middle of Shanbei Slope．This research has the important guiding significance for further oil-gas exploration.

    Characteristics and Dominating Factors of Reservoirs in Leikoupo Formation, Southwest Sichuan Basin
    DING Xiong1,2,3，TAN Xiu-cheng1,3，LI Ling1，TIAN Jing-chun2，DU Ben-qiang4
    2015, 29(3):  644-652. 
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    On the basis of comprehensive analysis of drilling, logging and core data, it is considered that carbonate reservoir of grain shoal is an important reservoir type in Leikoupo Formation, Middle Triassic, southwest Sichuan Basin. The reservoir types of two different patterns of porosity and permeability have been mainly developed:(1) Dolarenite reservoirs are dominated by residual intergranular pores and intergranular dissolved pores in the reservoir space, and are possessed of well developed throats with neck down and shaped tube, and are characterized by the good reservoir capability with medium porosity and permeability;(2) Oolitic limestone and residual bioclastic dolomite reservoirs are dominated by isolated intragranular dissolved, moldic and organisms pores in the reservoir space, and are possessed of less developed throats which mainly are miniature in the dimension, and manifest as medium porosity and low permeability. Analysis to the controlling factors of these reservoirs suggests as follows: (1)Grain shoals lay the foundation to the reservoir; (2)Reservoir pattern is controlled by the thickness of a single shoal; (3)The preservation of primary intergranular pores is the key to dolarenite reservoirs, while syndiagenetic meteoric leaching is crucial to reservoirs of oolitic limestones and residual bioclastic dolomites.

    High Pressure Simulation Experiment and Porosity Characteristics of Cambrian-Ordovician Deep Buried Dolostones in Tarim Basin
    TAN Jun-ying，ZHU Jing-quan，LIU Ling
    2015, 29(3):  653-664. 
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    Cambrian-Ordovician dolostone in Tarim Basin is an important oil and gas reservoir with the characteristics of deep buried depth and old geological age. According to the preliminary tests of properties, several dolostones with good porosity and permeability: stromatolite dolostone, crystalline dolostone and patchy dolostone, are chosen. In order to fully consider the impact of buried depth, rock composition and structure on reservoir physical property, an in situ simulation experiment to research the permeability changing law of these dolostones under the buried condition is designed, and the causes and influence factors are analyzed. At the same time, its petrology characteristics and pore types are studied by means of optical microscope and scanning electron microscope. Of all the samples for this experiment, stromatolite dolostone shows the best permeability, whose pore system has good connectivity and compressive resistance, and is composed of  fenestral pores and intercrystal pores, so its good permeability can be maintained under the deep buried condition. Crystalline dolostone with good permeability owes to its larger intercrystal pores, which depends on the content, size and crystal shape of the dolomite. Patchy dolostone reviews poor permeability under the deep buried condition, as its stylolite pores under high confining pressure is difficult to preserve.

    Buried Karstification Period and Contribution to Reservoirs of Ordovician Yingshan Formation in Tazhong Area
    ZHENG Jian1,2，WANG Zhen-yu1,2，YANG Hai-jun3，SUN Chong-hao3，ZHANG Yun-feng2，CHEN
    2015, 29(3):  665-674. 
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    By using of cores, core slices, logging and geochemical analysis of test data, researchers studied the characteristics, stages and the control mechanism for reservoir distribution of buried karstification in the deep carbonate rocks of Ordovician Yingshan Formation in Tazhong area. Researches showed that three periods of different development scales, degrees and karst-fracture characteristics of buried karstification in Ordovician Yingshan Formation have been identified. The first period which occurred in the Late Caledonian to the Early Hercynian period distributed in the whole region, but its corrosion is weak; the second occurred in the Late Hercynian to the Early Indosinian period is obviously controlled by tectonic action, previous pore layers and favorable sedimentary facies belts, and may be associated with the magmatic hydrothermalism activity of the Late Hercynian period, thus fracture and pore forming are filled with calcite and fluorite; the third happened in the Himalayan period, controlled by strike-slip faults and fracture development, then fractures and holes are filled by light crude oil and natural gas. Overall, the deep burial dissolution usually associated with acidic hydrothermal fluid and dissolution of carbonate minerals which are related to the thermal evolution of organic matter, and often the early dissolution occured along the previous pore and fracture cracks with the characteristics of multi-stages, unequal sizes, proximal dissolution and distal cementation, solution cave forming on the inheritance of original fracture-cave system, which is a key factor in the reconstruction of reservoir formation and optimization.

    Genesis Characteristics and Research Means of Paleokarst Collapse
    TANG Pan1，WU Shi-qiang2，YU Bing-song1，QIAN Yi-xiong3，PENG Shou-tao2
    2015, 29(3):  675-683. 
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     In the development and evolution of the paleokarst, the collapse of paleocave is a common  phenomenon, and the collapsed-paleocave systems are good oil/gas reservoirs. Based on the formation mechanism of karst collapse, this paper illustrates the similarity of paleokarst collapse and karst collapse, then combs the genesis characteristics combined with the formation mechanism and the cause of coalesced collapsed-paleocave systems as high quality reservoirs. The collapsed-paleocave systems can be studied on the basis of characteristics of well drilling, cores, ground penetrating radar, seismic interpretation, conventional logging and FMI imaging logging. As the patterns of collapsed-paleocave systems vary in different geological settings, many problems remain to be resolved. To solve these problems, this paper put forward three proposals that are to be carried out urgently.

    Influence of Differential Tectonic Uplift on Karst Development in the Southern Slope of Tabei Uplift
    LI Meng1,2，TANG Liang-jie1,2，LI Zong-jie3，ZHEN Su-jing1,2
    2015, 29(3):  684-691. 
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    The temporal and spatial variations of sub-structural units in the southern slope of Tabei uplift were analyzed by using balanced section technology, and then the control of differential evolution on ancient karstification, especially on epigenic karstification was discussed combined with the analysis of Cambrian-Ordovician unconformity types. The result indicated that Yingmaili uplift and Halahatang sag were being formed in the early episode of Middle Caledonian period and formed in Late Yanshanian period corresponding to the early episode of Middle Caledonian-Middle Yanshanian karstification, which has the characteristics of long duration, strong dissolution and erosion. Akekule uplift and Caohu sag were being formed in the episode Ⅰ of Middle Caledonian period and formed in Indosinian period corresponding to the early episode of Middle Caledonian-Late Hercynian karstification, which has the characteristics of moderate exposure and good condition for karst formation and conservation. Halahatang sag was being formed in the episode Ⅰ of Middle Caledonian period and formed in Late Hercynian period corresponding to the  episode I and episode Ⅲ of Middle Caledonian karstification, which has the characteristics of relatively weak erosional dissolution.

    Reservoir Characteristics and the Effect of Diagenesis on E2s4 Reservoir in the West Slope of West Depression，Liaohe Oilfield
    LIU Sheng-qian1，JIANG Zai-xing1，WANG Xia-bin1，CHEN Ji1，GAO Yi1，WU Ming-hao1，SUN
    2015, 29(3):  692-701. 
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    Based on the observation and analysis of rock thin sections, cast thin sections,physical properties and intrusive mercury curves of cores derived from sandstone reservoirs(E2s4) in the west slope of west depression of Liaohe oilfield, the lithology, diagenesis and physical properties of E2s4 were analyzed. The results show that the main lithological types are feldspathic lithic sandstone and lithic sandstone in the study area, and the common diagenesis types are compaction, cementation, metasomatism, dissolution and alteration; pore types mainly include primary intergranular pore, intergranular dissolved pore and intragranular dissolved pore, among which the expanded intergranular pore is the most common type; pore structure types are mainly fine-medium pores with fine throat and the physical property of reservoirs is good with mediumlow porosity and medium permeability. The influence of diagenesis on reservoir development shows that compaction and cementation have destructive effect while dissolution plays a constructive role in improving reservoir property. This study indicates that intergranular dissolved pore, intragranular dissolved pore, expanded intergranular pore and oversize macropore formed by dissolution make the greatest contribution to the reservoir, resulting in the formation of high quality reservoirs with medium-high porosity and medium-high permeability. Two abnormal high porosity-permeability intervals in which dissolution widely develops are identified in depths of 900-1,900 meters and 2,300-2,900  meters, and these two intervals should be the focus of next exploration targets to find favorable reservoirs.

    Discussion on Concealed Rock Mass Delineation and  Gold Source in Southwestern Guizhou
    WANG Liang，LONG Chao-lin，LIU Yi
    2015, 29(3):  702-712. 
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    The exploration of gold deposits in southwestern Guizhou has been upgraded to the national strategic level, and it is important to clarify the gold-deposit formation mechanism. The deep substrate material has been studied using regional gravity and magnetic data in this paper. Through the delineation of the shallow and deep concealed-rock masses and the fitting calculation of the geology-gravity model anomalies, this paper has analyzed the gold mineral source combined with regional geological, geochemical and mineral data of the study area. The gold mineral source has two main supply models. One is the surface layer of sedimentary rocks providing ore-source layer previously proposed，and the other is the deep Mesozoic granite or metamorphic basement (containing basic-ultrabasic magmatite) providing ore-source layer firstly proposed in this paper.This study has determined 12 anomaly areas of the shallow concealed-rock masses,and has separated 4 large deep-magmatite blocks.The result basically reflects the general geology situation of the study area, and can provide relevant basis for gold exploration in southwestern Guizhou.

    Prospecting Effect on Geochemical Primary Halos of Polymetallic Ore Belt in Eastern Bogda, Xinjiang Combined with Induced Polarization Survey
    YUSUPU AILI Kadier1,2, CHEN Chuan1,2 ,LIU Lei1,2
    2015, 29(3):  713-720. 
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    The surface of eastern Bogda in Xinjiang is heavily covered, and the rock weathering and erosion is serious,so the direct prospecting signs are not obvious. The large-scale geochemical measurement method played a significant role in the discovery and delineation of concealed ore bodies combined with the auxiliary function method of highgradient induced polarization measurement. The quantitative analysis of trace elements in the study area showed that Cu, Zn, Mo and As elements are relatively extra enriched, and Pb, Sn, Co and Ba elements are enriched, and the single element has horizontal zonation. According to the characteristics of elements combination and spatial distribution of geochemical primary halos, it would be delineated four Ⅲ-grade geochemical anomaly areas by the criteria of single-element anomalies’ lower limit and continental crust Clark value. The anomaly evaluation indicates that Cu-Pb-Zn-Mo-As-Sn-Co-Ba-Fe-Ni-Hg multi-element superimposed anomaly form is favorable for prospecting. According to the results of geochemical, geophysical induced polarization and drilling data, the predicting preliminary reveals that the geological mineralization condition of this predicting area is conducive to the formation of pyrite-type copper deposits, and further exploration could be done in the other anomalous areas to prospect small-size copper deposits.

    Magnetic Properties of Soil Profile in Quartz-sand Industrial Area and the Environmental Significance
    LI Yong1, LI Hai-yan2
    2015, 29(3):  721-726. 
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    Mineral magnetic parameters and SiO2 contents were measured on a typical soil profile at quartz sand industrial area in Fengyang County, Anhui. Results showed that the magnetic mineral content of the soil profile was low, and the magnetic property was controlled by the maghemite. The soil profile from top to bottom can be divided into three magnetic layers, and the magnetism gradually became weaken from the first layer to the third layer. The magnetic property of the third layer was mainly controlled by the soil parent material. The first layer had obviously magnetic enhancement phenomenon, which may be caused by secondary maghemite and combustion. The magnetic parameters and SiO2contents showed that the first layer of the soil profile had been polluted by weakly-magnetic quartz tail sands. In the dilution of quartz tail sands, the magnetic structure of the first layer had changed, and the magnetic mineral content reduced. The combined characteristics of magnetic parameters and SiO2 contents can reflect the pollution process of the first layer soil by quartz tail sands.

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