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    20 March 2016, Volume 22 Issue 1
    Fluid Inclusion Studies of the Jiande Copper Deposit,Zhejiang Province,China
    CHEN Hui, NI Pei*, CHEN Renyi, YE Tianzhu, WANG Guoguang,
    2016, 22(1):  1.  DOI: 10.16108/j.issn1006-7493.
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    Jiande copper deposit in Zhejiang Province was found in the 1960, and it is located in the northeastern part of
    Qinzhou-Hangzhou suture belt between Yangtze and Cathaysia blocks. Research about ore-forming fluids on it is still lacking. This
    study made a systematic investigation of fluid inclusions in the Jiande copper deposit. Based on petrographic observations of
    ore-bearing quartz collected from the massive ores, there are three types of primary inclusions of Jiande deposit: two-phase liquid-rich
    (type I), two-phase vapor-rich (type II), and halite-bearing (type III) fluid inclusions. Type I inclusions occur widely in the Jiande

    deposit and show homogenization temperatures of 220~377℃ and salinities of 0.63~8.00 wt.%NaCl equivalent. Type II and type III
    inclusions primarily coexist in ore veins. Homogenization temperatures of type II and type III reveal peak temperatures at 296~334℃
    and 290~326℃ , respectively, and their salinities at 1.22~2.00 wt.% NaCl and 31.87~38.16 wt.% NaCl, respectively. The results
    indicate that fluid boiling process took place, and metal precipitation was probably induced by extensive fluid boiling events during the
    ore stage. Raman analysis of fluid inclusions indicates that, in the gaseous phase, water is dominant with small amount of CO2, CH4, and
    N2. Our study suggests that the Jiangde copper deposit is a Yanshanian Skarn deposit rather than a Hycernian Sedex Cu deposit.

    Study on Petrogenesis and Uranium Mineralization Potential of Taojindong Granite in Southern Zhuguangshan Composite Pluton
    LAN Hongfeng, LING Hongfei*, SUN Liqiang, WANG Kaixing, OUYANG Pingning,LIU Jian
    2016, 22(1):  12.  DOI: 10.16108/j.issn1006-7493.
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    In this paper, geochronology and petrogeochemistry and Sr-Nd isotopic geochemistry of Taojindong granite are studied and
    compared with those of other Indosinian granites in the eastern part of the southern Zhuguangshan composite pluton. LA-ICP-MS
    zircon U-Pb dating for Taojindong granite yields an age of 204 ± 2.1 Ma, suggesting its intrusion in the late Indosinian period.
    Chemically, this granite is peraluminou, and shows relatively high contents of silica(SiO2=69.7%~75.0%), alkali(K2O+Na2O=7.74%~
    9.08%)and FeOT, and low abundance of magnesium. Thus, the Taojindong granite is characterized as calc-alkalic- to alkali-calcic,
    peraluminous, and ferroan. The rock samples display high total REE contents(ΣREE=226~272×10-6), with LREE/HREE ratios of
    6.27~11.4 and(La/Yb)N ratios of 4.01~15.0, and a negative Eu anomaly(δEu=0.15~0.42). This granite is enriched in Rb, Th and U,

    and depleted in Ba, Sr, Ti and Eu, showing characteristics of a typical low Ba and Sr granite. Isotope geochemical analysis reveals high
    and variable initial 87Sr/86Sr ratios(0.71922~0.72040), yet low and constant εNd(t)values(-10.0~-10.2)with two stage model age of
    1.80~1.82 Ga. All these features suggest that the Taojindong granite is a typical crust-derived granite. The granitic magma may have
    been derived from low-intermediate degree partial melting in a crustal extension-thinning tectonic environment in the late Indosinian
    period, of metagreywackes rocks whose origin was crust rocks separated from the mantle in the Paleoproterozoic. In the southern
    Zhuguangshan composite pluton, compared with non-uranium-mineralization-bearing granites, the uranium-mineralization- bearing
    granites experienced stronger hydrothermal alterations, and show wider variations in FeOT(/ FeOT + MgO)ratios, higher uranium
    concentration, more depletion in CaO, Ba, Sr, Ti and Eu, lower εNd(t) values and more ancient two stage model ages. The
    non-uranium-mineralization-bearing granites were derived from metagreywackes and relatively depleted in U. Taojindong granites have
    not experienced significant hydrothermal alteration and have no characteristics of intense alteration like uranium-mineralizationbearing
    granites. The geochemical features of the Taojindong granites are similar to those of the Indosinian non-uranium-mineralizationbearing
    granites in the southern part of the Zhuguangshan composite pluton, and its uranium potential is slight.

    Uranium-bearing Volcanic-intrusive Complexes in the Daqiaowu:Magma Mixing and Implications for Uranium Metallogenic Potential in the Gan-Hang Tectonic Belt
    WANG Hongzuo, WU Junqi*, CHEN Peirong, TANG Jiangwei, LING Hongfei, ZHAO Yo
    2016, 22(1):  30.  DOI: 10.16108/j.issn1006-7493.
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    The Daqiaowu uranium deposit is a volcanic-intrusive rock-hosted uranium deposit, where zircon ε Hf(t) values of the
    volcanic-intrusive complex (dated at 138~125 Ma) exhibit a remarkable rise from approximately -13.0 to -3.0 through time. Zircon
    saturation temperatures of these rocks also show an increase from ~749℃ to ~846℃. These characteristics suggest that volcanicintrusive
    rocks in the Daqiaowu were generated by mixing of magmas derived from mantle and crust, and that more inputs of
    mantle-derived materials were added to younger rocks. Together with a compilation of granitic intrusive rocks associated with magma
    mixing in Xiangshan, Furongshan and Muchen, we found that whole-rock εNd(t) and zircon εHf(t) values of these granitic rocks increased

    from -9.0 to -2.0 and -10.0 to 2.0 during 135~112 Ma, respectively, suggesting more contributions of mantle-derived magma through
    time in the eastern part of Gan-Hang Tectonic Belt (GHTB) than in the western part. Sr-Nd isotopic modelling results indicate that the
    percentage of mantle-derived magma has increased from 0% to ~60% during 135~112 Ma. Generally, mantle-derived magma has lower
    uranium contents than does the derived magma. The magma mixing/mingling between them would be expected to dilute the uranium
    contents of the crust-derived magma and lower its uranium metallogenic potentials. More mantle-derived materials in the commingled
    magmas would lead to much lower uranium metallogenic potential. The fact that magma mixing is more intense in the eastern part of the
    GHTB than in the western part probably is one of the reasons for the emplacement of larger uranium deposits in the western GHTB.
    Thus, in order to find larger uranium deposits in the eastern part of the GHTB, more attention should be paid to such areas with both
    uranium-rich basement (granites or felsic metamorphic rocks) and the overlying Early Cretaceous volcanic rocks.

    Study on the Source of Ore-forming Fluid and Ore-forming Material of the 302 Uranium Deposit in Northern Guangdong Province :Evidence from H-O-Sr-Nd Isotope Geochemistry
    FU Liwen,SUN Liqiang,LING Hongfei*,SHEN Weizhou,LI Kun,FENG Shangjie
    2016, 22(1):  43.  DOI: 10.16108/j.issn1006-7493.
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    The 302 uranium deposit, located at the eastern part of the Zhuguangshan granite composite in northern Guangdong
    province which is the most important large ore-concentrated area of granite-hosted uranium deposit in China, is a large-scale, deeply
    buried and largely vertical mineralized granite-hosted uranium deposit. Uranium ore bodies occur mainly as vein type, flat beanpod-like
    and lens-like, and are hosted within hydrothermally altered fault zones in the Indosinian Youdong granite and the early Yanshanian
    Changjiang granite. And the dominant uranium-bearing mineral is pitchblende. Despite intensive research over the past few decades,
    the source of ore-forming fluid and ore-forming material of this uranium deposit remains controversial. The results of hydrogen and
    oxygen isotopes in this article show that δDH2O and δDH2O values of ore-forming fluids range from -7.09‰ to 3.24‰ and from -105‰
    to -63‰ , respectively, indicating that ore-forming fluids were mainly formed by deeply circulating meteoric water which have

    experienced water-rock interaction. The relatively low δDH2O value may be caused by hydrothermal boiling action of ore-forming fluids
    or mixing up with small amount of organic water ( δOH2O -90‰ to -250‰) in the process of deep circulation. The εNd(t) values (-11.9
    to -11.4) and rare earth element distribution patterns of the fluorite of metallogenic period are similar to those of the Changjiang granite
    but obviously different from those of the Youdong granite. Fluorites are in or near the scope of Changjiang granite in Gd/Yb-Nb/Ta
    diagram, indicating that uranium source of the 302 deposit was mainly derived from the Changjiang granite.

    The Enrichment of Calcite and the Genesis of Uranium Deposits in Dongsheng Uranium Sandstone
    FENG Qiao, QIN Yu*, FU Suotang, LIU Yiqun, ZHOU Dingwu
    2016, 22(1):  43.  DOI: 10.16108/j.issn1006-7493.
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    Research on calcite in Dongsheng uranium area is carried out including the enrichment characteristics, inorganic carbon
    and oxygen isotopes, neighboring gas reservoirs inclusions trapping pressure, organic carbon isotopes and 3He/4He ratios. The results
    show that there is a close relationship between Dongsheng uranium mineralization and deep natural gas. The δ13C values range
    from -19.6‰ to -1.11‰ and the δ18O values range from -17.13‰ to -9.00‰ in calcite. The values of δ13C vary widely, maybe due to
    the influence of surface water and deep natural gas. The gas reservoirs inclusion trapping pressures decreased from the deep to the
    superficial part and from southwest to northeast in northern Ordos Basin, indicating that natural gas has supplied sufficient reducer for
    the conversion of uranium necessary for the formation of large-scale uranium. The 3He/4He ratio in natural gas indicates that Dongsheng
    Zhiluo uranium sandstone has no meaningful contribution from mantle fluids. The evidence shows that the calcite is a result of joint
    actions of surface water and deep gas in Dongsheng uranium sandstone, suggesting that Dongsheng large-scale uranium deposit was
    formed by the effect of cryogenically mixed mineralization.

    New Ideas on the Origins of Potash Deposits in Yunnan China and Laos
    LI Minghui,YAN Maodu,FANG Xiaomin,ZHANG Zengjie,SUN Shurui
    2016, 22(1):  60.  DOI: 10.16108/j.issn1006-7493.
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    The Lanping-Simao basin in the southwestern China is located at the junction of the Eurasian and Indian Plates, and
    adjacent to a large potash deposit of Khorat Basin and Sakon Nakhon Basin in Thailand and Laos. Chinese scientists thought that the
    potash deposit in Lanping-Simao basin should be as large or important as that in Khorat Basin and Sakon Nakhon Basin. The
    relationship between Mengyejing potash in Lanping-Simao basin and potash deposits in the Sakon Nakhon Basin and Khorat Basins has
    long been discussed in many respects such as tectonic belt, depositional features, salt minerals, geochemical elements, and forming era.
    Many scientists thought that they had similar brine origins, and hydrothermal fluid was one important origin for the potash deposit.
    However, the ideas have received no supporting evidence. The type of hydrothermal fluid was not clear either. This study presents δ18O
    and δD of halite inclusions from a ZK2893 core in Laos to provide isotopic evidence for the idea. The values of δ18O are from -2.3 to
    9.5‰ with an average of 2.9‰ , while those of δD are from -78 to -150‰ with an average of -108.6‰ . Most of δD was less
    than -90‰. The relationship between δ18O and δD shows that the hydrothermal fluid is metasomatic hydrothermal fluid which was
    originated from reactions between rainwater and surrounding rocks. Surrounding rocks are important origin for potash deposits. Most
    data were plotted near to the 150℃-curve in the δ18O-δD diagram. The possible forming temperature of halite inclusion in Laos could be

    about 150℃. On the other hand, the forming temperature of halite inclusion in Lanping-Simao Basin was about 145℃ with the highest
    value of 170℃. The similar temperatures provide new evidence for their similar brine origins of the two basins.

    Analysis of Mineralization and Prospecting of Deep Gold Deposit in Shuiyindong, Guizhou
    LIU Shuai, PENG Jin, LIU Jianzhong*, WANG Zepeng, YANG Chengfu
    2016, 22(1):  66.  DOI: 10.16108/j.issn1006-7493.
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    The Shuiyindong gold deposit is one of the most important gold deposits in Yunnan-Guizhou-Guangxi“golden triangle”area,
    southwestern China and it is a typical Carlin-type strata-bound gold deposits. In this study, we analyzed the borehole data of No.0~427
    prospecting line by drawing a contour map and a distribution map of mineralization trending degree in ore-bearing strata. The study
    uses the Surfer software to draw the simulation diagram of deposits boundary and the mineralization trend. The study is focused on
    analyzing the structure geometry and mineralization pattern of ore-bearing strata in the Shuiyindong mining area. Our analysis reveals
    that interface contour line reflects the shape of the anticline. Also, the main locations of gold deposits are at the hinge area of the
    anticline and the plunging end of the anticline in the Shuiyindong gold deposit. There existed a negative correlation between Sbt
    (structurally altered rock body) and the upper part of the Longtan Formation in the mineralization degree; and the mineralization of the
    Shuiyindong gold deposit shows obvious inhomogeneity; In addition, the mineralization degree of Sbt has a regular distribution of a
    weak-strong-weak pattern along the east-west directionn and the mineralization degree in the Longtan Formation shows a negative
    correlation with the SARB. The mineralization degree is enhanced at the plunging end of the anticline in the Longtan Formation,
    suggesting that a large-scale industrial ore body may exist in the deep part of the strata.

    Mid-ocean Ridge Jump and Extension in the Context of Hotspots:Discussion on the Tectonic Evolution of Indian Ocean
    LI Jianghai, ZHANG Huatian*, LI Honglin, LIU Zhonglan
    2016, 22(1):  74.  DOI: 10.16108/j.issn1006-7493.
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    This paper is based on the compilation of the Indian Ocean Tectonic Map and the analyses of the tectonic pattern and
    significant tectonic events of Indian Ocean. Three problems are further discussed concerning the initial breakup mechanism of Indian
    Ocean, ridge jump and hotspots, and mid-ocean ridge extension. We draw the following conclusions: 1) The Indian mid-ocean ridges
    can be divided into two systems: Southeast Indian Ridge-central Indian Ridge-Carlsberg Ridge (East Branch), and Southwest Indian
    Ridge (West Branch). The former system is the product of Pacific Ocean Ridge system extension. The latter one is the product of the
    tectonic adjustment of Pacific-Southeast Indian Ridge system and Atlantic Ocean ridge system. 2) The initial breakup was controlled by
    vertical compression-horizontal extension and developed along pre-Cambrian orogen. 3) Indian Ocean experienced two major ridge
    jump processes. The directions of ridge jump and hotspot movement are consistent, illustrating internal connection of the two tectonic
    processes. 4) The Atlantic and Pacific mid-ocean ridge systems joined in Indian Ocean in Paleogene. Its terminal was continuously
    fragmented. This can be called Fish-Tail Tectonics, which illustrates that Indian Ocean links up and adjusts the development of three
    major ocean basins. The Indian Ocean is therefore a key hinge of global oceanic basins.

    Zircon U-Pb Ages and Hf Isotopic Compositions of the Sangsang Granitic Pluton in the Middle Segment of the Gangdese Belt: Constraints on the Petrogenesis and Tectonic Evolution
    WANG Ruiqiang, QIU Jiansheng*, YU Sibin, ZHAO Jiaolong
    2016, 22(1):  81.  DOI: 10.16108/j.issn1006-7493.
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    To better understand the petrogenesis and tectonic implications of the Sangsang granitic pluton located in the western part of
    the middle segment of the Gangdese belt, we have conducted an integrated study of the geochronology, elemental geochemistry, and
    zircon Hf isotopic compositions of the granitic pluton. Zircon LA-ICP-MS U-Pb dating for the Sangsang granitic rocks yields ages of
    49~54 Ma, indicating that they were emplaced during Eocene. Chemically, all the rocks are subalkaline, metaluminous and poor in
    phosphorus (A/NKC<1.10,P2O5<0.20%), thus can be grouped into calc-alkaline I-type granites. They are enriched in Cs, Rb, Ba, Th, U,
    K, Pb and LREE, and depleted in Nb, Ta, P, Ti, showing the geochemical characteristics of arc magmatic rocks. The granitic rocks have
    variable zircon εHf(t) values which are scattered from positive to negative values (=-4.24~ + 5.49), implying that different source
    components have contributed to magma genesis. The integrated petrologic, elemental and isotopic compositions suggest that the
    Sangsang granitic rocks were mainly originated by partial melting of juvenile crust, with some ancient crustal materials involved in their

    petrogenesis. In combination with the regional tectonic setting, the authors suggest that the ancient crustal components were likely derived
    fromthesubductedIndiacrust,andherebyinferredthattheinitialtimeoftheIndia-Eurasiacollisionshouldbeearlierthan54Ma

    Geochronology, Hf Isotopic Compositions and Geochemical Characteristics of the Pingying Granite Pluton in Northern Guangxi,South China, and Its Geological Significance
    ZHANG Shitao,MA Dongsheng*,LU Jianjun,ZHANG Rongqing,CAI Yang,DING Chaochao
    2016, 22(1):  92.  DOI: 10.16108/j.issn1006-7493.
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    Granite samples from the Pingying plutons have been analyzed for zircon U-Pb ages, Hf isotope and whole-rock geochemical
    compositions to discuss the emplacement age, genetic type, source and relationship with the Baotan tin deposit. Zircon
    LA-MC-ICP-MS U-Pb dating gives a weighted mean 206Pb/238U age of 834.2±5.1 Ma for the coarse-grained biotite granite in the central
    phase, indicating that it was formed in the Neoproterozoic. The granite samples are strongly peraluminous with high silica and alkali
    contents and enriched in Cs, Rb, U and Ta, but relatively low in Ba, Sr and Ti. Chondrite-normalized REE diagrams of the granite are

    right inclined and show strongly negative Eu anomalies with Eu/Eu* values ranging from 0.05 to 0.31. Theε Hf(t ) values of zircon grains
    vary from -12.6 to -1.6 with a peak of -4.8~-3.0, and the two-stage Hf model ages range from 1.83 to 2.51 Ga with a peak of 1.9~2.0
    Ga. These characteristics indicate that the Pingying granite was formed by partial melting of the Paleoproterozoic basement rich in
    boron, and experienced strong differentiation. This study shows that the Neoproterozoic biotite granite in the Jiuwandashan-
    Yuanbaoshan area has the potential for tin mineralization and it is an important part of the evolution of multi-period granite and tin
    polymetallic metallogenic series in South China as well.

    Application of the Weighted Logistic Regression Model in Prediction of Volcanic Rock-Hosted Copper Deposits-Taking the Middle Part of Ning-Wu Basin as an Example
    ZHAO Zengyu, CHEN Huogen, PAN Mao, JIA Gen, LI Xiangqian, XU Shiyin,GUO Gang, ZH
    2016, 22(1):  105. 
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    Application of the Weighted Logistic Regression model in prediction of volcanic rock type Copper deposits in the Middle
    part of Ning-Wu Basin is studied. First, the geological setting of ore-forming processes is analyzed. Three kinds of factors including
    geological body, structure and wall rock alteration are extracted based on the spatial distribution of copper deposits from the geologic
    map. Then, the spatial relationships between Copper mineral occurrence and each evidence factor are analyzed. It is suggested that
    Niangniangshan and Gushan volcanic edifice play an important role in spatial distributions of volcanic rock-hosted Copper deposits.
    The ten evidence raster layers including Longwangshan Formation, Gushan Formation, trachyte porphyry of Gushan volcanic edifice,
    monzonite porphyry of Niangniangshan volcanic edifice, buffers of the structure lines with NE, NW and EW trending, and the alteration
    areas of chalcopyrite, silicide and Limonite are selected. Finally, metallogenic probabilities are calculated using the Weighted Logistic
    Regression model. Four ore-forming prospects, including P1, P2, P3 and P4, are indicated based on the geological conditions of

    metallogenesis and model results. Among these prospecting areas, P1, P2 and P3, which are controlled by Niangniangshan and Gushan
    volcanic edifice, are spread in the northeast direction. P4 extends in the west-east direction and is controlled by Longwangshan volcanic
    edifice. The copper ore bodies are already found in these prospecting areas, suggesting that the results should be generally reliable.

    Geochronology and Significance of Intermediate-acid Intrusive Rocks in Quanji Area, Gangcha, Qinghai
    ZHANG Guodong, XU Zhengqi, GONG Jun, FENG Jun, HAN Yabiao, ZHANG Jianwa
    2016, 22(1):  113.  DOI: 10.16108/j.issn1006-7493.
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    There are many intermediate-acid intrusive rocks in Quanji area. In order to better understand of the characteristics,
    intrusion age, and formation environment, we have studied the geology, geochemistry, and geochronology of intermediate-acid intrusive
    rocks in Quanji area. LA-ICP-MS zircon U-Pb results show that the intrusion age of granitoid rocks is 430~455 Ma, indicating that
    magmatic intrusion took place in different phases during Late Ordovician to Early Silurian in the study area. U-Pb age data show that
    the granodiorite was formed at 444±11 Ma, i.e., late Ordovician. Thus, the Balonggonggaer Formation should be earlier than the Late
    Ordovician. Geochemical characteristics show that granitoid is rich in K and excessive in Al, enriched in LILE(Rb, K and Ba) ,
    depleted in HFSE (Nb,Ti and P) with a weak negative europium anomaly. Diorites are rich in K, and quasi-aluminous and have a
    negative europium anomaly that is not obvious. Granite and granodiorite have a weak europium negative anomaly. Quartz diorite is not

    obvious. Intermediate-acid intrusive rocks have characteristics of continental collision in terms of formation environment. Based on
    regional tectonic setting and previous research results, we infer that intermediate-acid intrusive rocks were produced in a subduction or
    collision setting during the Caledonian orogeny from Late Ordovician to Early Silurian.

    Shallow Borehole Drilling of the Lower Silurian Black Shale in Jiangsu Province and the Shale Gas Potential Analysis
    JIA Dong*, HU Wenxuan, YAO Suping, YIN Hongwei, LI Yiquan, WANG Wenhui,
    2016, 22(1):  127.  DOI: 10.16108/j.issn1006-7493.
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    The shale gas exploration of the Longmaxi formation in the Lower Silurian in the upper Yangtze region obtained great
    breakthrough in recent years. More and more attention is focused on the shale gas resource potential and exploration prospect in the
    lower Yangtze zone, which is in the same tectonic block with the upper Yangtze. The Gaojiabian formation in the lower Yangtze is the
    equivalent layer of the Longmaxi formation in the upper Yangtze. Due to the strong erosion on the surface and the bad exposure, the
    distribution and the thickness of the black shale rock are unclear, which restrict the evaluation and prospection of the shale gas
    exploration potential. In this respect, this study performed the shallow well drilling project for the black shale in the Tangshan in
    Nanjing and Lunshan in Jurong. On basis of the analysis of the cores from these 5 boreholes, this study revealed the characteristics of
    the black shale, including the thickness, geochemical features, petrology, and biostratigraphy. The results suggest that the black shale
    is well comparable with the Jiaoshiba in the upper Yangtze and that at least 4 graptolite fossil zones are consistent with each other. The
    thickness of the Wufeng-Gaojiabian black graptolite shale is larger than 80.5 m in Tangshan zone, and larger than 39.5 m in Lunshan.

    The organic abundance is relatively high. The TOC content is from 1.2% to 4%, which implies relative strong hydrocarbon generation
    capacity. The Ro ranges from 1.5% to 2.6%, which indicates the thermal evolution degree is high-over mature. The hydrocarbon
    entered the gas generation stage. The organic pattern of the black shale is mainly kerogen Ⅰ and Ⅱ1. Therefore, we considered the
    lower Silurian shale has good shale gas resource potential in the lower Yangtze zone.

    A Preliminary Investigation of the Development and Hydrocarbon Potential of the the Black Shales in the Upper Permian Dalong Formation,Southern Anhui Province in the Lower Yangze Region, China
    LIAO Zhiwei, HU Wenxuan*, CAO Jian, YAO Suping, XU Zhimin, ZHANG Yuexia, WAN Ye,
    2016, 22(1):  138.  DOI: 10.16108/j.issn1006-7493.
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    The upper Permian Dalong Formation in the Lower Yangtze Region with black shales is potential for hydrocarbon source
    rock. Little attention has been paid to this issue. In order to improve the understanding about it, we conducted a comprehensively
    combined study of petrology and organic geochemistry based on three recently-discovered Dalong black shales outcrops in the southern
    Anhui province, with the aim to characterize the development and hydrocarbon potential of the Dalong black shales. The results show
    that the black shales developed widely in all the three outcrops, including the Niushan (Xuancheng City), Caicun (Jingxian County) and
    Changqiao (Jingxian County). Lithology of the shales is variable from chert to calcareous shale, as well as siliceous mudstone.
    Stratigraphic correlation and sedimentology of the shales imply that the study area has been subjected to a complete sequence of marine
    transgression and regression and the black shales generally developed in the environment of deep seawater under reducing, restricted
    and undercompensated conditions. The results from the study of petrology and organic geochemistry show that the Dalong black shales

    are rich in organic with the average total organic carbon content being around 2.0%. In terms of kerogen types, the organic matter is
    primarily II2 and III. Combined with the high to over maturation of organic matter, we propose that the regional exploration should be
    focused on natural gas reservoir. Based on the comparison of the distribution of Mesozoic-Cenozoic igneous rocks and black shales in
    the study area, we infer that the over maturation of organic matter may be primarily influenced by large-scale magmatism in South
    China during the Mesozoic to Cenozoic period. Thus, petroleum exploration potential can also be considered in the areas where there
    was no/little significant influence of magmatism (e.g., the Jingxian-Guangde area). These results and understanding can also provide
    highlights for the fundamental geological study of the black shales in this region.

    Geological Comparison of Silurian Gaojiabian Formation of Lower Yangtze Area and Middle Devonian Marcellus Formation in the Appalachian Basin in North America
    ZHANG Tao, YIN Hongwei*, JIA Dong, DING Hai
    2016, 22(1):  152.  DOI: 10.16108/j.issn1006-7493.
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    Based on paleogeography and tectonic settings, strata spatial distribution characteristics, basic geochemistry indexes and
    mineral composition, we compared lower part of Lower Silurian Gaojiabian Formation of Lower Yangtze area and middle Devonian
    Marcellus Formation in the Appalachian basin. The results show that the two sets of shales shared similar paleogeography and tectonic
    settings, both accumulated in tranquil anoxic basinal waters and their euxinic depositional site allowed the preservation of the finely
    organic detritus. The stratigraphy and thickness trends of both formations reflect the interplay of tectonism during the formation time
    and the later stage. These events shaped the stratigraphic architecture of both formations and can impact the exploration and production
    strategies of shale gas. Both formations are considered to be good source rocks for the exploration of shale gas and they both have high

    thermal maturity and contain relatively high total organic carbon (TOC) content, as well as large amount of brittle minerals. Compared
    with Marcellus shale, Gaojiabian Formation contains less TOC content, has a deeper burial depth burial depth and has been reworked
    by multicycle tectonism, which bring higher risks for the exploration of shale gas.

    Pore Structure of Organic-rich Shales in the Lower Silurian Gaojiabian Formation from Ningzhen Area,Jiangsu Province
    LI Jinning, YAO Suping*, SUN Chao, DING Hai
    2016, 22(1):  159.  DOI: 10.16108/j.issn1006-7493.
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    To provide data for the reservoir evaluation of the lower Silurian organic-rich shales in the Lower Yangtze Region, in this
    study we analyze the characteristics of pore structures of the shales based on the study of samples from the LunShan 5 well in the
    Ningzhen Area. Comprehensive methods were employed, mainly including field emission scanning electron microscopy (FE-SEM),
    small angle X-ray scattering (SAXS) and low-temperature nitrogen adsorption(LT-N2GA). Results indicate that the pores in the shales
    are generally nanoscale and can be classified into four types in general, i.e., organic pores, interparticle pores, mineral matrix pores and
    microfractures. The interparticle pores dominate among these multiple types of pores. The pore size distribution of the shales are
    complex, as mesopores (2~50 nm) were distributed most widely and some micropores (<2 nm) and macropores (>50 nm) have also
    been observed. In terms of the controls of the pore size distribution of the shales, we conduct a correlation between pore volume and
    brittle minerals (e.g., quartz, pyrite and albite) contents, clay contents and TOC. It is implied that mineral compositions are the primary
    control, contents of brittle minerals and clay minerals also play a certain influence (especially for micropores and mesopores), whereas
    TOC has the least impacts.

    Structural Analogue Modeling and PIV Finite Strain Analysis: Implications to Tectonic Fracture Prediction
    SHEN Li, JIA Dong*, YIN Hongwei, WEI Dongtao, CHEN Zhuxin, SUN Chuang,
    2016, 22(1):  171.  DOI: 10.16108/j.issn1006-7493.
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    The development of structural fractures and finite strain state are closely related in the oil and gas reservoir. In order to
    explore a new method of finite strain analysis and structural fracture prediction, this study designed and performed a set of sandbox
    experiments. The particle image velocimetry (PIV) technique was applied to quantitatively analyze the experimental process. The
    experimental model was a unilateral indentation model with a viscous layer in the vertical direction, and the results represent a

    macroscopic box fold. Using the PIV technique, we can obtain the displacement field data during the deformation process in each stage
    of the experiments, calculate the incremental strain in each step, and analyze the finite strain state during the whole deformation
    process from the initial stage to the time after the fold was formed. Furthermore, the genesis mechanism and distribution can be
    discussed to quantiatively predict the fractures. At the beginning of the deformation, the finite strain was weak (about 4-8%) and
    widely distributed. Weak compressive linear strain was represented in the direction of indentation and weak tensile linear strain in the
    vertical direction. These phenomena were interpreted as the results of the pure shear deformation, such as the thickening and parallel
    shortening of the layers before the folding and faulting initiated. It is also the main mechanism of the formation of the regional tension
    fissures and shear cracks. The finite strain was localized in the fault zone and the adjacent area when the fold and fault formed. Strong
    shear and tensile shear strain (up to 20%) was revealed. These were the results of the simple shear deformation along the fault plane. It
    is also the main mechanism of the formation of the local shear fractures and tensile shear cracks.

    Technology of Strain Analysis and Fracture Prediction Based on DEM Numerical Simulation
    CAI Shenyang, YIN Hongwei*, Li Changsheng, JIA Dong, WANG Wei CHEN Zhuxin
    2016, 22(1):  183.  DOI: 10.16108/j.issn1006-7493.
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    The application of strain analysis and fracture prediction technology is of great importance in geosciences. However, the
    discrete element method (DEM), which is suitable for solving problems with discontinuous property, has not been widely used in this
    field. This paper presents an attempt to construct DEM model of a bulk of rock with realistic properties, followed by a simulation of the
    evolution of a compressional detachment structure. The strain distribution and fracture formation are analyzed afterwards. As to the
    detachment structure, the result shows that the interval in which the fracture generation reaches its peak precedes the one in which the
    fault appears the most active. Additionally, fractures and strain distribution share the same concentrating areas, and the number of
    fractures is proportional to the intensity of the strain. Also, fractures that are related to the same fault first concentrate on its fault plane,
    then appear in the vicinity of that plane. It indicates that, within the range of fault influence, the further a fracture is from the fault
    plane, the later it is generated. Above all, the result has revealed a great application potential of DEM in the field of strain analysis and
    fracture prediction.

    Numerical Simulation of Hydraulic Fracturing Based on Discrete Element Method
    GU Yingfan, LU Yi, LIU Bing, LIU Chun
    2016, 22(1):  194.  DOI: 10.16108/j.issn1006-7493.
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    The studies on the characteristics of hydraulic fracturing under different conditions have an important meaning to the
    effective shale gas exploration. As rocks are composed of grains and pores at micro scale, the discrete element method is introduced to
    simulate hydraulic fracturing processes. The rules of energy calculation and energy conversion in the models are proposed and a 3D
    discrete element model is built. Furthermore, 3D discrete element numerical simulation software“MatDEM3D”is developed. The
    variations of strata stress and hydraulic speed are simulated by varying the model vertical strain and the particle diameters,
    respectively. The simulation results indicate: (1) the number and direction of hydraulic fractures are influenced by the anisotropic
    properties of rocks, stress state, and hydraulic speed. (2) Fractures are generated when the compressive wave passes. When hydraulic
    pressure increases at a high rate, the number of induced fractures is much greater. Furthermore, the percentage of effective energy

    (fracturing energy) is also greater, and as a result, the efficiency of hydraulic fracturing is higher. (3) When the vertical strain is zero,
    50% of the fractures are vertical. When the vertical strain is -1×10-4, the fractures tend to develop along the direction of the maximum
    compressive stress, and the percentages of vertical fractures are greater. The numerical simulation and energy analysis provide a new
    method for researching the hydraulic fracturing processes of rocks.

    The Characteristics of the Core Fracture Structure Based on The Industrial CT Scanning
    YUAN Jingwen,JIA Dong*,WEI Dongtao, CHEN Zhuxin, CUI Jian, WU Xiaojun
    2016, 22(1):  200.  DOI: 10.16108/j.issn1006-7493.
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    In order to study the characteristics of fractures in the shale,we used the industrial CT to scan the shale core in the Jurong
    basin,and analyzed the CT scanning data of shale by the digital processing technology. We established the model of CT scanning data
    and extracted the fracture by VGStudio MAX software. In this way we could study the differences between the structure of fractures in the
    shale which is composed of different mineral composition and the various CT image. The research results show that there are two groups
    of fractures with different strike and dip of fracture developed. The dip of one group with high angle was approximately 70°~90°;the other
    group with low angle was approximately 30°~40°. Jurong basin may have experienced at least two tectonic events after the Rhuddanian.
    The comparison of the shale composed of different composition indicated that the greater density differences of mineral component,the
    industrial CT scanning image will be more clear, and that the larger size of mineral grain, the effect of scanning will be more obvious.

    A Study into the Microscopic Pore Structure of Microfossils with Focused Ion Beam Scanning Electron Microscopy (FIB-SEM)
    XU Chang, WANG Wenhui*, YAO Suping
    2016, 22(1):  207.  DOI: 10.16108/j.issn1006-7493.
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    Focused ion beam scanning electron microscopy(FIB-SEM) is a dual beam system which combines focused ion beam (FIB)
    and scanning electron microscopy (SEM) to cut samples and display real-time images at nanometer scale. This study observed several
    kinds of microfossils from the Lungmachi Formation (Llandovery, Silurian) with FIB-SEM. The results reveal that submicron-nano
    pores, which provide valid space for shale gas reservoirs, are well-developed in conodonts, chitinozoans and acritarchs. Disparities of
    micro-pores in different fossil groups shown in this study will help to explain the cause of organic pore heterogeneity in shales.