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    20 June 2011, Volume 17 Issue 2
    The energy prospect of China and frontiers of energy science and technology
    Jia Cheng-Zao
    2011, 17(2):  151-160. 
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     Exploitation of energy  resources  is  the base  for  the economic society,s orderly development of our nation. From  the analysisof domestic and overseas energy consumption structures, we found that coal consumption still takes large proportion in the national primary energy consumption structure. The national energy consumption structure  forecast of 2030 shows  that  the drop in coal consumption is limited, nuclear energy, hydro-electric, and other new energy proportion will increase slightly. The paper, based on our national energy consumption structure, analyzes the national energy resources status and prospect, summarizes the frontiers of energy science and technology, and raises major technological problems of all energy resources fields, to accelerate the exploit ation of national energy resources.

    Methods in studying petroleum accumulation systems in a superimposed basin: A case study of petroleum reserviors in the central Junggar basin
    JIN Zhi-Jun
    2011, 17(2):  161-169. 
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    The basic method  in studying petroleum accumulation system  in superimposed basins was demonstrated by a case
    investigation  in petroleum  reserviors of  the central Junggar Basin. The method can be summarized  into  two points. The  first  is
    that  the study  is  focused on petroleum reserviors. The second  is  that both organic and  inorganic geochemical methods are used.
    The case study  in  the central Junggar Basin shows  that  the area has at  least  two petroleum accumulation systems according  to
    the organic (biomarker in particular) studies, i.e., the Permian system in the eastern area to the Penyijingxi sag, and the Permian
    and Jurassic system in the middle-eastern Mosuowan area. The study using inorganic geochemical method on reservoir diagenetic
    calcite shows  that  the area has  two additional petroleum accumulation systems,  i.e.,  the Permian and Jurassic system  in  the
    surrounding area of the Dongdaohaizi sag and the Permian system in the Shidong area. Moreover, the potential of retaining oil and
    gas  for each petroleum accumulation system was assessed  to provide  information  for  the exploration. Therefore,  it  is concluded
    that the research method of petroleum accumulation system can help to improve the guidance on petroleum exploration, and the
    organic and inorganic geochemical methods are complementary to each other. In particular, the new application of the inorganic
    geochemical method is a supplement to and improvement for the previously and commonly used organic geochemical method, and
    thus deserves to be studied further.

    Basin types and distribution of the global giant oil and gas fields
    Jia Dong, WU Long, YAN Bin, LI Hai-Bin, LI Yi-Quan, WANG Mao-Mao
    2011, 17(2):  170-184. 
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    After summarizing previous research material of global giant oil and gas fields, the USGS data, and typical proto-type
    basinal classification schemes, we classify the world’s 877 giant oil and gas fields and 153 main basins in which they are located.
    In  this paper, we present  four maps and eight statistical histograms showing distributions of giant oil and gas  fields and basins
    based on different basinal classification schemes. Basin types and distribution of global giant oil and gas fields are identified, and
    then  the effects of different proto-type basin categories on  the distribution of giant oil and gas  fields are discussed. At  the same
    time, considering the complex tectonic evolution of basins as well as their association with hydrocarbon accumulation, we attempt
    to classify superimposed basins according to their tectonic transformation or inheritance characteristics. Our results indicate that
    basins with positive inversion features are optimum for the formation of giant oil and gas fields; successor rift basins and successor
    foreland basins are less prominent, leaving negative inversion basin type to the least option.

    Tectonic control on the hydrocarbon accumulation and prospect for large oil-gas field exploration in the southern Junggar basin
    GUO Shao-Jie, TUN Chao-Dong, ZHANG Zhi-Cheng, CHEN Wei
    2011, 17(2):  185-195. 
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    A series of  thrust-fold belts were  formed  in  the southern Junggar  foreland basin during  the Cenozoic. This paper
    provides  regional structural analyses of  the  thrust  fold belts based on  the growth strata,  interpretation of seismic profiles, and
    balanced cross-sections,  together with available magnetostratigraphic  results. Our analyses show  that  three paralleled  rows of
    anticlinal belts have been developed sequentially from the south to the north since ~7 Ma for the southern, ~2 Ma for the middle,
    and ~1 Ma for the northern  anticlinal belt, respectively. The systemic studies of the sedimentary sequences show that the source
    rocks, reservoirs, seal rocks, and traps between the northern and southem margins of the Tian Shan are similar and there are three
    petroleum systems (or plays) in the southern Junggar Basin. The reason why there has been no discovery large oil-gas field of so far
    in the southern Junggar may be mainly due to the very late deformation and the existence of two detachment layers, i. e., the upper
    detachment  layer of  the Ahjihaihe Formation  (E2-3a) and  the  lower detachment  layer of  the middle Jurassic coal beds  (J2x). This
    paper proposes  that  the  lower play,  i.e.,  the Upper Jurassic  reservoirs sealed by  the Lower Cretaceous,  is  favorable  for  forming
    large-scale oil-gas field and should be potential targets for future exploration.

    The Geochemical Model of Petroleum, Natural Gas and Coal Multi-resource System
    YAO Su-Peng, HU Wen-Xuan, JIAO Kun
    2011, 17(2):  196-205. 
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    Through diagenesis, catagenesis and metagenesis, biological sources  form petroleum, natural gas, and coal. These
    processes are controlled by organic  facies.  Integrating  sedimentology, organic petrology, and organic geochemistry, organic
    facies  is  the most effective method  to evaluate  the petroleum, natural gas, and coal productivity potential of a certain basin. By
    comprehensively analyzing  the geochemical condition  for petroleum, natural gas, and coal productivity,  this paper proposes
    the  four end models based on maceral analysis  to characterize organic  facies and evaluate  the petroleum, natural gas, and coal
    productivity potential. With the method, Mesozoic strata of the Ordos basin and late Permian Wujiaping age strata of the Southeast
    China are depicted as upper woody plants facies (A), lower woody plants facies (B), lower woody plants-exinite facies (C), shallow
    water woody plants-algae  facies  (D), deep water herb-algae  facies  (E), and aquatic algae  facies  (F). Typical oil source  rock and
    humic coal are respectively  formed  in aquatic algal  facies and upper woody  facies. Upper woody  facies and aquatic algal  facies
    are  the main  types of petroleum, natural gas and coal  rich basin such as Ordos basin, but other  transitional  facies are  found  in
    Mesozoic strata of  the Ordos basin and Late Permian Wujiaping Age strata of  the Southeast China which extend  the genesis
    theory of petroleum, gas and coal and multienergy exploration. By utilizing multistatistic analysis the authors develop an approach
    to numerical  representation of organic  facies, build up  the organic  facies  type  index model which computes  the model value of
    contribution of organic facies to the genesis of petroleum, gas and coal and provide the basic method for geochemical quantitative

    modeling of combustible organic mineral concentration.

    Source Rock Features and Resource Potential of the Lower Cretaceous Strata in Coastal Southeast China
    HU Guan, HU Wen-Xuan, Cao-Jian, TAO Su-Peng, XIE Xiao-Min, GAO Yu-Qiao
    2011, 17(2):  206-219. 
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    By detailed field survey and organic geochemical analyses including organic matter abundance, type, and maturity of
    the Lower Cretaceous strata  in  the coastal Southeast China,  the source rock  features of  the strata were obtained. These  features
    allow a discussion on the hydrocarbon resource potential of the strata. The results demonstrate that there are in general two sets
    of argillaceous hydrocarbon source sequences, i.e., the early Lower Cretaceous represented by the black mudstone of the Bantou
    Formation  in Fujian Province and  the  late Lower Cretaceous represented by  the black mudstone or calcareous mudstones of  the
    Guantou Formation in Zhejiang Province. The organic matter abundance of the sources reached the moderate to good quality by
    the hydrocarbon source rock standards, and  the average TOC values and  the chloroform bitumen “A” of  the early stage sources
    are high. The  type of organic matter  is mainly Type  III, Types  II and  I can also be  found and generally  the  types of  late stage
    sources are better  than  those of early stage sources. The  thermal maturity of most samples  is high  to over mature, and organic
    matter  that was not significantly affected by volcanism  is still  in maturing stage. Thus, a  relatively comprehensive hydrocarbon
    resource evaluation indicates that the favorable regions are the northern Guangdong Province for the early Lower Cretaceous, andthe coastal region of Zhejiang Province and the western Fujian Province for the late Lower Cretaceous. These results may provide
    new petroleum targets for oil-gas exploration in Southeast China.

     

    Provenance Analysis of the Upper Triassic Flysch in Renbu Area, Southern Tibet
    XU Wen-Li, LI Xiang-Hui, WANG Yin, ZENG Qiang-Gao, SUN Yong, NI Ma-Ci-Ren
    2011, 17(2):  220-230. 
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    The sandstone clastic composition, paleocurrent,  trace element and  rare earth clement are combined  to analyze    the
    provenance of the Upper Triassic Langjiexue Group and the Nieru Formation in Renbu area, southern Tibet. Results of the clastic
    composition and geochemistry  indicate  that most of  the clastic materials were derived  from  the  recycled orogenic belt; Some of
    them were from the mixed area before the orogeny; Few was from the continental basement and recorded continental margin arc
    process prior  to  the orogeny.  It  is verified  that parent  rocks came  from  the  recycled sediments of  the orogen and post-Archean.
    Paleocurrent measurement shows that the Langjiexue Group and the Nieru Formation were probably sourced from the North. The
    former was from the northeast, but the latter was from the northwest. The latter is closer to the source region than the former. These
    are consistent with  the present distribution of strata. These results suggest  that  the upper Triassic  flysch were probably sourced
    from the north or even the Lhasa Block

    Analysis of the Percolation Characteristics and Their Influence Factors on the Chang-8 Sandstone Reservoir in Jiyuan Area
    YANG Yan-Fang, LUO Jing-Lan, YANG Jin-Long, LIU Xiao-Hong
    2011, 17(2):  231-239. 
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    The Chang-8 Unit of the Yanchang Formation is a major reservoir in Jiyuan area, Ordos Basin. However, the reservoir
    shows strong heterogeneity and oil production varies  from well  to well dramatically. In  this paper, samples  from 4 dr  lling wells
    were selected  to conduct  relative permeability sensitivity  test so  that  the percolation characteristics and  their  influence  factors
    can be   studied during the reservoir water-flooding process. Twenty casting thin sections were observed carefully, and the image
    analysis of grain size and  the analysis of pore-throat were carried out. Other  tests were also done  including capillary pressure
    measurement, scanning electron microscope  (SEM), X-ray diffraction and sensitivity analysis of clay minerals  in  the sandstones,
    and  the oil-water displacement experiment. The purpose of  the work  is  to analyze micro-pore structures of  the  reservoir, clay
    minerals, and the impact of diagenesis on relative permeability curve. Results show that the permeability curve of the reservoir in
    the study area can be further divided into two types: the up-concaved and linear percolation curves. The up-concaved curve of the
    corresponding reservoir belongs to the distributary channel microfacies with a high content of skeleton minerals, coarse grain size,abundant primary  intergranular pores and  large-diameter dissolution pore and good connectivity between pores. Mineral grain
    contacts mainly occur as point to point and point to line, and the throat is coarse and long. The porosity and permeability of the
    reservoir are high, and  the  fluid percolation  is good. In addition, as  to reservoirs with micro-cracks, proper water—flooding rate
    can  improve  the efficiency of oil displacement. Because of  the strong heterogeneity and high content of sensitive clay-minerals
    of  the  reservoir, pressure should be  increased gradually  to  raise  the water-flooding pressure  to eventually solve  the problem of
    clogging of pores by clay mineral. This research is important for understanding of reservoir percolation characteristics in the initial
    stage of exploitation and is useful to enhance oil recovery

    Cenozoic Tectonic Evolution of the East Java Basin, Indonesia
    YANG Fu-Zhong, LUO Liang, Jia Dong, ZHU Hou-Qi, WU Long, LI Xia
    2011, 17(2):  240-248. 
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    The East  Java Basin  is one of  the most  important oil and gas bearing basins  in  Indonesia.  Its Cenozoic  tectonic
    evolution can be summarized as  two  rifting phases and  two compressional events. The Eocene back-arc  rifting basin  resulted
    from  the northward subduction of  the  Indo-Australian plate under Sundaland. The subduction changed  its direction  to NE-SW
    in the Oligocene, which induced the second phase of E-W extension and rifting. The Roo Rise ocean plateau, south of East Java,
    collided with Sundaland at about 15 Ma, which resulted in the formation of major type of oil traps and positive inversion structures
    in the basin. Part of the Australian proximal continental slope collided with the Banda Volcanic Arc at about 3.5-2 Ma and caused
    the second phase of compressional deformation in the East Java Basin.

    Geochemical Characteristics and Genesis of Crude Oils of Carboniferous and Triassic in Tahe Oil field of Tarim Basin
    ZHENG Chao-Yang, LIU Yi-Qun, DUAN Yi, XU Wen-Xiu, FAN Ting-Ting, ZHANG Xue-Jun
    2011, 17(2):  249-259. 
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    Because Tahe oil field is the largest marine carbonate rock oil field of the Tarim Basin, its genesis is of great interest.
    By means of  to  the high-resolution GC-MS analysis of  the oil samples  from Carboniferous and Triassic Tahe oil  field,  this paper
    studies biomarkers and discuss  their genesis. The Pr/Ph, Pr/nC17 and Ph/nC18 data  indicated  that oil  formed  from  sapropel
    organic matters of reducing environment. Abundance of gammacerane C30+ hopane  indicates  that  the oils  formed  from saltwater
    environment. The abundance of C27  sterane,  tricyclic  terpane,  tetracyclic  terpane, and higher  tricyclic  terpane vs hopane
    parameters show that original source materials are homonemeaes. Rearranged sterane/sterane, Ts/(Ts+Tm), and C29ββ/(ββ+αα)
    are 0.24~0.40,0.28~0.50 and 0.56~0.63,respectively. All of  these show  that  the maturity of  the oil  is high. The occurrence of
    25-norhopane  indicates  that  the oil experienced some degree of biodegradation. Comparison of oil and source rock suggests  that
    the oils of the main source rock came from the middle-upper Ordovician source rocks.

    Quality of Reservoir Sandstones of Funing Formation in Yaotan Area from  Jinhu Depression, Subei Basin, and Its Influencing Factors
    ZHANG Ni, LIN Chun-Ming, YU Hao, YAO Yu-Lai, ZHOU Jian
    2011, 17(2):  260-270. 
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    Reservoir sandstones of  the Paleogene Funing Formation  in Yaotan Area of Jinhu Depression mainly consist of  lithic
    arkose and arkose, with medium compositional maturity and median-high  textural maturity. The Funing Formation  reservoir
    sandstones  in Yaotan area are  in  the A stage of epigenesis,  the main diagenesis of which  includes compaction, cementation,
    dissolution, and replacement. Diagenesis and  tectonic movement  influence  the reservoir physical properties  together, especially
    affect the porosity and permeability of the reservoir in the study area. Compaction and cementation rapidly decrease the porosity
    and permeability of  the reservoir as well as  the whole reservoir quality, while dissolution can  improve  the reservoir quality and
    cause the development of secondary pores. Compaction in the reservoir of the study area mostly show as brittle fractures of rigid
    particles, compressional deformation of plastic particles,  rigid particles embedding  into plastic particles,  linear and concave-
    convex contacts between particles, and  the obvious directional alignment of detrital grains. Dissolution mainly present as  the
    dissolution of carbonate minerals, with  the sements between detrital grains mostly being authigenic caly minerals, carbonate
    minerals and authigenic quartz. The replacement in the study area mainly show as the replacement between the carbonate cements
    and quartz, the feldspars and lithic debris, or inside the carbonate cements. The tectonic movement can partly improve reservoir physical properties in the study area.

    Structural Anaysis of Binxian-Wangfu Sag in Songliao Basin
    CHENG San-You, LIU Shao-Feng, SU San
    2011, 17(2):  271-280. 
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    By means of  two dimensional structure-stratigraphy  interpretation of several seismic profiles, cross-section balancing,
    and calculation of extension amount and extension  rates,  the paper  investigated developing process of  the Binxian-Wangfu sag
    and analyzed  the structural  features and forming mechanism of the basin. The results show that Binxian-Wangfu sag was in the
    initial stage of rifting  in  the Huoshiling Formation, Shahezi Formation and Yingchengzi Formation, and  the  fault depression was
    mainly controlled by normal faults before the deposition of the Denglouku Formation. The sag onlaps to the Tangfangzhen uplift,
    and was also controlled to some extent by normal faulting within the basin during the deposition. The sag completely turned into
    depression and exhibited regional subsidence after the deposition of the Denglouku Formation, and the subsidence center was not
    obviously corresponding  to  the early  fault depression, and  the subsidence of  the Binxian-Wangfu sag was not controlled by  the
    early fault depression. During the Quantou Formation period, especially the third segment and the Qingshankou Formation period
    the sag mainly showed depressional subsidence; The general structure of  the basin was clearly marked by  faults  in  the  lower
    section and onlap in the upper section. The basin formation was associated with the the NS-trending dextral transtension.

    Research on Faults and Structures of Hulin Basin in Heilongjiang Province by  Gravity Gradient Tensor
    GAO Li-Kun, JIANG Fu-Yu, HUANG Lin-Yun
    2011, 17(2):  281-286. 
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    The  full gravity gradient  tensor was calculated  from gravity anomaly data of Hulin Basin with    fast Fourier  transform.
    Based on zero values of Vxx and Vyy components  indicating boundaries of sources and  their orientations approximately along x
    or y axes, Vzz indicating the location and extent of anomalies, Vzx, Vzy and Vxy highlighting structure of NS, EW and NE (NW),
    a comprehensive analysis was conducted on  the characteristics of Hulin Basin gravity and  its gradient  tensor. We deduced  that
    there are NE-NW-NEE-and EW- and NS-trending  faults  in    the study area,  five of which were described. Based on  the synthetic
    characteristics of gravity anomalies and their tensor, and fault distribution, Hulin Basin consists of three uplifts and two depressions,
    corresponding to Yinchun uplift, Hulin River depression, central Hulin uplift, Donglinzi depression and Xingkai lake uplift.

    Establishment and 3-D Visualization of Deep Structures in Foreland Thrust Belts: Taking the Jinfosi Thrust Belt in the Southern Margin of Jiuquan Basin as an Example
    ZHU Min, CHEN Han-Lin, CHENG Xiao-Gan
    2011, 17(2):  287-296. 
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    Jinfosi Pluton  is seismically highly  reflective medium and  it has been difficult  to obtain velocity data of  the pluton
    directly. The deep structures of Jinfosi  thrust belt  revealed by  time-domain and depth-domain seismic data show significant
    difference. We used the velocity data that were derived in laboratory under high temperatures and pressures simulating conditions
    at depth  to quautify  the  relationship between velocity and depth underground. This allows  time-depth conversion  for  the 2-D
    seismic data of  the Jinfosi pluton and comparison of  the deep structures of Jinfosi  thrust belt  revealed by  the  time-domain and
    depth-domain seismic data. Based on  the new depth data and  interpretation, GOCAD software was employed  to establish a 3-D
    geological model, which allowed further discussion of the deep structures. The model shows that the Mesozoic-Cenozoic rocks form
    a deeply buried monocline which dips SW and structural highs are relatively deeply buried with dips diminishing toward the two
    limbs.

    A Review on Mixed Rocks of Terrigenous Clastics and Carbonates and Their Petroleum-Gas Geological Significance
    FENG Jin-Lai, HU Kai, CAO Jian, CHEN Yan, WANG Long-Gang, ZHANG Ying, WANG Mu, ZHAO Jian
    2011, 17(2):  297-307. 
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    The present progress in research on mixed rock of terrigenous clastics and carbonates is reviewed in this paper, mainly
    including classification,  terminology, depositional environment, depositional modes and petroleum-gas geological significance.
    It  is proposed by a comprehensive analysis  that  the depositional  facies  favorable  for  the mixed deposition mainly cover coastal
    and shallow-lake  faicies,  following by shallow-sea shelf, shore-shallow  lacustrine and delta  facies. The study on  the depositional
    environment  implies  that  the  factors controlling  the development of coastal mixed-rocks  include  tidal effect,  relatively strong
    hydrodynamic condition and a shallow sea environment favorable for the living of lower organisms. In contrast, with respect to the
    shore-shallow  lacustrine  rocks,  the  factors are  frequent  lake-level and climate changes. Consequently, a deep discussion on  the
    depositional micro-facies and associated environmental  factors may be an effective way  to  improve and better  the classification
    and  terminology of  the mixed  rocks. Furthermore, a synthetic depositional model  for  the marine and  lacustrine environment  is
    suggested based on above-mentioned analyses, combined with case studies in Paleogene and Neogene middle-deep mixed rocks in
    the northwestern Qaidam Basin. In addition, the shore-shallow sea and lake areas of mixed deposition can form high-quality targets of

    reservoir and source rocks, based on factual research data on source and reservoir sequences associated with mixed rocks.

    Characteristics and Mechanics of Cenozoic Salt-Related Structures in Kuqa Foreland Basins: Insights from Physical Modeling and Discussion
    YIN Hong-Wei, WANG Zhe, WANG Xin, WU Zhen-Yun
    2011, 17(2):  308-317. 
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    Salt  layer has a significant  influence on  the structural deformation and evolution of Kuqa  foreland basin. Structural
    styles are quite different in the strata beneath and above salt. Strata above salt are mainly deformed by broad folding, while strata
    beneath salt are mostly deformed by closely-spaced thrusts. Based on scaled physical experiments, we investigate the deformation
    pattern and mechanics of Kuqa salt-related structures. Modeling  results show  that Kuqa salt-related structures are primarily
    controlled by  regional compression and growth sedimentation. Salt structures near  the back end, such as Kelasu  fold belt, are
    controlled by regional compression, and salt structures near the front end, such as Qiulitake fold belt, have a significant influence
    from the heavy growth sedimentation in the nearby Baicheng syncline.

    Salt Structures in the Eastern Margin of Precaspian Basin and Their Relationship with Ural Orogeny
    YANG Xiao-Qun, TANG Liang-Jie, ZHU Yong
    2011, 17(2):  318-326. 
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    Based on  the  interpretation of seismic profiles, salt structures  in  the eastern margin of  the Precaspian Basin and
    their relationships with Ural orogeny were analyzed. The salt structures  in  this study area  include salt diapirs, salt pillows, salt
    rollers, salt welds,  turtle structures and minibasins, which are  featured by  the zonation of deformation. There are zones of salt
    weld, salt rollers, salt pillows, and salt diapirs from the east to the west. Salt controls the tectonic deformation of the suprasalt and
    the subsalt, in which normal faults and thrust faults were developed, respectively. The cross sections show that salt experienced
    two stages of deformation  including  the gravity spreading and differential  loading halokinesis, and  the salt structures had close
    relationship with the Ural orogeny. Ural orogeny had reversed the strata in the eastern margin of the Precaspian basin, and exerted
    strong influence on salt deposition and the subsquent deformation of salt driven by gravity spreading and differential loading.

    Study on the Fluid Inclusions of Maoping Tungsten Deposit, Southern Jiangxi Province
    HU Dong-Quan, HUA Ren-Min, LI Guang-Lai, WUI Xing-Lin, HUANG Xiao-E
    2011, 17(2):  327-336. 
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    Maoping  tungsten deposit  is a  large W-Sn-polymetallic deposit discovered  recently  in southern Jiangxi Province.
    It comprises  two  types of ore-bodies,  i.e. quartz-vein  type and greisenized-granite  type. This paper studies  the  fluid  inclusions
    in quartz and  topaz occurring  in wolframite-quartz-veins, which mainly  includes microthermometry and Laser Raman analysis.
    Besides,  the homogenization  temperatures of  fluid  inclusions  in wolframite were determined under an  infra-red microscope.
    Results show  that  fluid  inclusions  in both quartz and  topaz are mainly  liquid-rich  two-phase aqueous solution  (H2O-NaCl),  in
    addition  to small amount of CO2-bearing  three-phase aqueous solution  in quartz. The homogenization  temperatures  from quartz
    show a wider range variations and can be divided into two main periods, indicating two stages of ore precipitation. The CO2-bearing
    three-phase inclusions have homogenization temperatures similar to those of the higher temperature period of the above inclusions,
    but  lower salinities and different homogenizing ways. Fluid  inclusions  in wolframite have highest homogenization  temperatures
    and salinities, whereas those in topaz also show high homogenization temperatures and salinities, and narrow variation range. The
    characteristics of homogenization temperatures and salinities from fluid inclusions in quartz reveal multiple-stages of ore-forming process and  the complexity of  fluid evolution.  It  is concluded  from  fluid  inclusions  that  the early-stage boiling and  late-stage
    mixing are probably the major mechanism of formation of wolframite-quartz-vein type ore in the Maoping deposit

    Genesis and Prospecting Significance of Lead-Zinc Ore Bodies in Jiama Mining Area, Tibet
    ZHENG Wen-Bao, TANG Ju-Xing, LI Feng-Ji, YING Li-Juan, WANG Huan, TANG Xiao-Qian
    2011, 17(2):  337-350. 
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    Jiama copper polymetallic deposit is one of the large deposits that gained prospecting breakthrough in recent years in
    Gangdese metallogenic belt, Tibet. By comparing with    typical SEDEX deposits,  this article means  to point out  the genetic  type
    of Jiama deposit as porphyry-skarn  type, related  to porphyry metallogenesis. The porphyry system of Jiama hosts many different
    mineralization  types owing  to different wall  rocks,  including porphyry Mo-Cu deposits centered  in  intrusions, skarns, hornfels,

    and Au deposits in independent peripheral locations. The differences between Jiama and typical SEDEX deposits are as follows.
    ① Geologic  features show that the magmatic hydrothermal solutions not only formed layered skarns in the space of K1 l  and J3 d,
    but also small-scale, lensing and cystiform skarns in the pelitic limestone interlayers of K1 l . There are no exhalative sedimentary
    rocks in Jiama mining area, and the so-called exhalative sedimentary rocks in the previous papers, in fact, are skarnized hornfels.
    The mineralization with an age of 14~16 Ma might be related to the delamination and large-scale crust stretching due to Gangdese
    collision orogenesis in Miocene epoch, and the porphyry intrusion event in later period. The copper polymetallic deposit of skarn
    has no double-layer structure,  typical of SEDEX. The upper skarn with  the wall  rock  roof has a gradual  transition  relationship.
    Skarn with coarse grained texture is the result of minerals, self-growth because of long time magmatic supplies. ② Geochemical
    characteristics. The combination of ore-forming elements is mainly of Cu, Mo, Au, Ag association, and in less amount Pb, Zn. Mn
    contents in limestone of J3d show negative anomaly compared with the regional background. The Zn / (Pb+Zn) ratio in Jiama Pb-
    Zn deposit mainly concentrates in two ranges of 0-0.1 and 0.2-0.45. Mineralization  of the deposit presents a zoning Mo→Cu+Mo
    →Cu→Pb+Zn. Isotopically, in contrast to SEDEX deposits, the δ 34S values of Jiama deposit are negative and concentrated, and its δ 30
    Si values are positive. Besides, an ore-prospection model is set up in this article based on the magmatic-hydrothermal theory
    of metallogenesis to search for the areas in Nyainqentanglha region with geological conditions similar to Jiama deposit, and to find
    the Pb-Zn ores in shallow, peripheral parts of porphyry bodies and Cu-Mo-W ores in their deeper, central parts.