• Volume 87,Issue 1,2013 Table of Contents
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    • A Review of the Tetrapod Track Record in China, with Special Reference to Type Ichnospecies: Implications for Ichnotaxonomy and Paleobiology

      2013, 87(1):1-20.

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      Abstract:“Splitting” and “lumping” are perpetual problems in vertebrate, especially dinosaur, ichnotaxonomy. Chinese dinosaur ichnotaxonomy, which began in 1940, provides a series of interesting case studies, highlighting the dual problems of historical and dubious ichnotaxonomy. Chinese Mesozoic tetrapod track types have been placed into 63 ichnospecies (one Triassic, 28 Jurassic, and 34 Cretaceous), exclusive of other, non-type ichnospecies or ichnotaxa identified from China. Fifty-two (~83%) of these 63 tetrapod ichnospecies were placed in monospecific ichnogenera. At the ichnogenus level, we prune—either by recognizing nomina dubia or by synonymy—17 from the list of 53 dinosaurian ichnogenera (a 32% reduction), leaving 36 ichnotaxa that we consider valid. Most of the cuts affect Jurassic theropod ichnotaxa, which are reduced from 23 to only nine because most ichnogenera are subjective junior synonyms of Grallator and Eubrontes. Fewer Chinese Cretaceous ichnotaxa (only six of 21 ichnogenera) are obvious nomina dubia or subjective synonyms, suggesting greater east Asian endemism during this time. Because ichnospecies differences are subtle, we provisionally retain ichnospecies as valid pending detailed comparative analyses of congeneric ichnospecies. This synthesis is long overdue and is necessary to address problems of historical and provincial ichnotaxonomy, which severely hamper comparisons of tetrapod ichnofaunas in space and time.

    • Taxonomy, Zonation and Correlation of the Graptolite Fauna across the Lower/Middle Ordovician Boundary Interval in the Yangtze Gorges Area, South China

      2013, 87(1):32-47.

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      Abstract:The graptolite fauna across the Lower and Middle Ordovician boundary at the Huanghuachang GSSP section, Yichang and the Jianyangping section, Xingshan County is described. The taxonomy of the pendent didymograptids, the graptolite zonations across the base of Middle Ordovician and their correlations are discussed in this paper. The two revised graptolite zones, the Didymograptellus bifidus Zone and the Azygograptus suecicus Zone, can be well correlated to their equivalents elsewhere in the world.

    • Astronomical Dating of the Middle Miocene Hanjiang Formation in the Pearl River Mouth Basin, South China Sea

      2013, 87(1):48-58.

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      Abstract:The Hanjiang Formation of Langhian age (middle Miocene) in the Pearl River Mouth Basin (PRMB), South China Sea consists of deltaic siliciclastic and neritic shelf carbonate rhythmic alternations, which form one of the potential reservoirs of the basin. To improve stratigraphic resolutions for hydrocarbon prospecting and exploration in the basin, the present study undertakes spectral analysis of high-resolution natural gamma-ray (NGR) well-logging record to determine the dominant frequency components and test whether Milankovitch orbital signals are recorded in rhythmic successions. Analytical results indicate the orbital cycles of precession (~19 ka and ~23 ka), obliquity (~41 ka), and eccentricity (~100 ka and ~405 ka), which provide the strong evidence for astronomically driven climate changes in the rhythmic alternation successions. Within biochronological constraint, a high-resolution astronomical timescale was constructed through the astronomical tuning of the NGR record to recent astronomically calculated variation of Earth’s orbit. The astronomically tuned timescale can be applied to calculate astronomical ages for the geological events and bioevents recognized throughout the period. The first downhole occurrences of foraminifers Globorotalia peripheroronda and Globigerinoides sicanus are dated at 14.546 Ma and 14.919 Ma, respectively, which are slightly different from earlier estimates in the South China Sea. When compared with the global sea-level change chart, the astronomical estimate for the sequences recognized based on microfossil distributions have the same end time but the different initiation time. This is probably due to the local or regional tectonic activities superimposed on eustatic rise which postponed the effect of global sea-level rising. Astronomical timescale also resolves the depositional evolution history for the Langhian Stage (middle Miocene) with a variation that strongly resembles that of Earth’s orbital eccentricity predicted from 13.65 Ma to 15.97 Ma. We infer that the main factor controlling the variability of the sedimentation rate in the Hanjiang Formation is related to the ~405-ka-period eccentricity.

    • Physical Modeling of Fold-and-Thrust Belt Evolution and Triangle Zone Development: Dabashan Foreland Belt (Northeast Sichuan basin, China) as an Example

      2013, 87(1):59-72.

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      Abstract:Triangle zones, generally found in foreland fold-and-thrust belts, serve as favorable objects of petroleum exploration. Taking the Dabashan foreland belt as an example, we studied the formation and development of triangle zones, and investigated the effect of décollements and the mechanical contrast of lithology by employing the method of physical modeling. Four experimental models were conducted in the work. The results showed that ‘sand wedges’ grew episodically, recorded by deformational length, height and slope angle. The height versus shortening rate presented an S-shape curve, and uplifting occurred successively in the direction of the foreland belt. During the formation of the triangle zone, layer-parallel shortening took place at the outset; deformation decoupling then occurred between the upper and lower brittle layers, divided by a middle-embedded silicone polymers layer. The upper brittle layers deformed mainly by folding, while the lower sand layers by thrusting. As shortening continued, the geometry of a triangle zone was altered. We consider that the triangle zone in the Dabashan foreland belt was modified from an early one based on available seismic profiles and the experimental results. In addition, décollements and mechanical contrast impose significant influence on structural development, which can directly give rise to structural discrepancies. More décollements and obvious mechanical contrast between brittle layers can promote the coupling between the upper and lower brittle layers. Basal décollement controls the whole deformation and decreases the slope angle of the wedge, while roof décollement determines whether a triangle zone can be formed.

    • Study of Distal Pyroclastic-flow Stratum from Tianchi Volcano in 1215 (±15) Eruption: Pyroclastic-flow Over Water

      2013, 87(1):73-81.

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      Abstract:In this paper, we describe three strata at the distal part of the pyroclastic-flow from the Tianchi volcano in 1215 (±15) eruption. One of the strata with crosslayers that are different from typical pyroclastic-flow strata may come from a ground-surge. The grain-size and scanning electron microscopy (SEM) analysis was performed to study the origin of the pyroclastic-flow. Characteristics of grain-size distribution show that it is similar with the ash cloud. Through the SEM analyses, we found some quench structures with less damage on the surfaces of the vitric pumices. These phenomena indicate that there has been hydration in the transportation processes at the distal of pyroclastic-flow. It has partly changed the transportation mechanism of pyroclastic-flow, which transitions form dense flow to diluted flow. This paper develops a new distal pyroclastic-flow model in the Tianchi volcano that can be divided into three stages, i.e. the quench stage, expanding stage and depositing stage.

    • Response of Macromolecular Structure to Deformation in Tectonically Deformed Coal

      2013, 87(1):82-90.

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      Abstract:The structural evolution of tectonically deformed coals (TDC) with different deformational mechanisms and different deformational intensities are investigated in depth through X-ray diffraction (XRD) analysis on 31 samples of different metamorphic grades (Ro, max: 0.7%–3.1%) collected from the Huaibei coalfield. The results indicated that there are different evolution characteristics between the ductile and brittle deformational coals with increasing of metamorphism and deformation. On the one hand, with the increase of metamorphism, the atomic plane spacing (d002) is decreasing at step velocity, the stacking of the BSU layer (Lc) is increasing at first and then decreasing, but the extension of the BSU layer (La) and the ratio of La/Lc are decreasing initially and then increasing. On the other hand, for the brittle deformational coal, d002 is increasing initially and then decreasing, which causes an inversion of the variation of Lc and La under the lower-middle or higher-middle metamorphism grade when the deformational intensity was increasing. In contrast, in the ductile deformational coals, d002 decreased initially and then increased, and the value of Lc decreased with the increase of deformational intensity. But the value of La increased under the lower-middle metamorphism grade and increased at first and then decreased under the higher-middle metamorphism grade. We conclude that the degradation and polycondensation of TDC macromolecular structure can be obviously impacted during the ductile deformational process, because the increase and accumulation of unit dislocation perhaps transforms the stress into strain energy. Meanwhile, the brittle deformation can transform the stress into frictional heat energy, and promote the metamorphism and degradation as well. It can be concluded that deformation is more important than metamorphism to the differential evolution of the ductile and brittle deformational coals.

    • The Ore-forming Mechanism of the Jiajika Pegmatite-Type Rare Metal Deposit in Western Sichuan Province: Evidence from Isotope Dating

      2013, 87(1):91-101.

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      Abstract:Granitic pegmatites are commonly thought to form by fractional crystallization or by liquid immiscibility of granitic magma; however, these proposals are based mainly on analyses of fluid and melt inclusions. Here, we use the Jiajika pegmatite deposit, the largest spodumene deposit in Asia, as a case study to investigate ore forming processes using isotope dating. Dating of a single granite sample from the Jiajika deposit using multiple methods gave a zircon U–Pb SHRIMP age of 208.4 ± 3.9 Ma, an 40Ar/39Ar age for muscovite of 182.9 ± 1.7 Ma, and an 40Ar/39Ar age for biotite of 169.9 ± 1.6 Ma. Based on these dating results and the 40Ar/39Ar age of muscovite from the Jiajika pegmatite, a temperature–time cooling track for the Jiajika granite was constructed using closure temperatures of the different isotope systems. This track indicates that the granite cooled over ~40 m. y., with segregation of the pegmatite fluid from the granitic magma at a temperature of ~700°C. This result suggests that the Jiajika pegmatite formed not by fractional crystallization, but by segregation of an immiscible liquid from the granitic magma. When compared with fractional crystallization, the relatively early timing of segregation of an immiscible liquid from a granitic magma can prevent the precipitation of ore-forming elements during crystallization, and suggests that liquid immiscibility could be an important ore-forming process for rare metal pegmatities. We also conclude that isotope dating is a method that can potentially be used to determine the dominant ore-forming processes that occurred during the formation of granite-related ore deposits, and suggest that this method can be employed to determine the formation history of the W–Sn ore deposits found elsewhere within the Nanling Metallogenic Belt.

    • Petrogenesis of Cenozoic Basaltic Rocks from Jiangsu Province, China: Evidence from Geochemical Constraints

      2013, 87(1):102-117.

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      Abstract:Cenozoic (Miocene to Pleistocene) basaltic rocks in Jiangsu province of eastern China include olivine tholeiite and alkali basalt. We present major, trace element and Sr-Nd isotopic data as well as Ar-Ar dating of these basalts to discuss the petrogenesis of the basalts and identify the geological processes beneath the study area. On the basis of chemical compisitions and Ar-Ar dating of Cenonoic basaltic rocks from Jiangsu province, we suggest that these basalts may belong to the same magmatic system. The alkali basalts found in Jiangsu province have higher ΣFeO, MgO, CaO, Na2O, TiO2 and P2O5 and incompatible elements, but lower Al2O3 and compatible elements contents than olivine tholeiite which may be caused by fractional crystallization of olivine, pyroxene and minor plagioclase. In Jiangsu basaltic rocks the incompatible elements increase with decreasing MgO/ΣFeO ratios. The primitive mantle-normalized incompatible elements and chondrite-normalized REE patterns of basaltic rocks found in Jiangsu province are similar to those of OIB. Partial loss of the mantle lithosphere accompanied by rising of asthenospheric mantle may accelerate the generation of the basaltic magma. The 143Nd/144Nd vs. 87Sr/86Sr plot indicates a mixing of a depleted asthenospheric mantle source and an EM1 component in the study area. According to Shaw’s equation, the basalts from Jiangsu province may be formed by 1%–5% partial melting of a depleted asthenospheric mantle source. On the basis of Ar-Ar ages of this study and the fractional crystallization model proposed by Brooks and Nielsen (1982), we suggest that basalts from Jiangsu province may belong to a magmatic system with JF-2 as the primitive magma which has undergone fractional crystallization and evolved progressively to produce other types of basalts.

    • Neoproterozoic Volcanic Rocks in the Southern Quruqtagh of Northwest China: Geochemistry, Zircon Geochronology and Tectonic Implications

      2013, 87(1):118-130.

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      Abstract:The Early Neoproterozoic Beiyixi Formation volcanic rocks of the southern Quruqtagh comprise mainly of a suite of tholeiitic basalts, alkaline andesites, and calc-alkaline rhyolites. The rhyolites are characterized by variably fractionated enrichment in light rare earth elements (LREE) and flat in heavy rare earth elements (HREE), and strongly negative Eu anomalies. Compared to the rhyolites, the andesites also exhibit enrichment in LREE and flat HREE (chondrite-normalized values of La/Yb,and La/Sm are 13.30-41.09, 3.18-6.89 respectively). Their rare earth element patterns display minor negative Eu anomalies. Both of them exhibit coherent patterns with strongly to moderately negative anomalies of Nb, Zr, Ti, and Hf on spider diagrams. Two rhyolite and one andesite magmatic zircons with defined oscillatory zoning yielded weighted mean 206Pb/238U ages of 743 ± 7 Ma, 741±2 Ma, and 727±4 Ma. These ages are interpreted to represent the timing of volcanic eruptions. According to geochemistry and rock type, these volcanic rocks formed within a continental island-arc environment following subduction of the oceanic crust during the Early Neoproterozoic period.

    • Geochronological and Geochemical Constrains on Petrogenesis of the Jietebutiao A-type Granite in West Junggar, Xinjiang

      2013, 87(1):131-147.

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      Abstract:Late Paleozoic post-collisional granitoids are widespread in West Junggar, as well as northern Xinjiang. As a representative of those intrusions, the Jietebutiao granite occurs in the southwestern margin of the West Junggar (northwest China), and is mainly composed of mid-coarse-grained monzogranite and syenogranite. In the present study, we report the results of high-precision zircon laser-ablation–inductively-coupled plasma mass–spectrometry U–Pb dating on the Jietebutiao granite for the first time, and yield weighted mean 206Pb/238U ages of 287 ± 9 Ma and 278 ± 3 Ma for monzogranite and syenogranite, respectively. The Jietebutiao granite has a pronounced A-type affinity; it is metaluminous to slightly peraluminous; has a high-K calc-alkaline composition; high concentrations of Na2O + K2O, varying from 6.8 to 8.5 wt%; high FeOt/MgO; 10 000Ga/Al ratios, a low CaO, MgO, and TiO2 content; enriched in some large ion lithophile elements (LILE, such as Rb and Th) and high field strength elements (HFSE, such as Zr, Hf, and Y); and depleted in Sr, Ba, and Ti. In addition, the granite has a relatively high rare earth element (REE) content (except for Eu), with significant negative Eu anomalies (Eu/Eu* = 0.01–0.72), and showing slight tetrad REE patterns and non-charge and radius controlled (CHARAC) trace element behavior. Petrographic, geochemical, and geochronological data suggest that the parental magma of Jietebutiao intrusions are of mixed origin, and are most probably formed by the interaction between the lower crust- and mantle-derived magmas in the Early Permian post-collisional tectonic setting. The basaltic magmas underplated and interacted with the lower crust that was dominated by deeply buried arc (and back-arc basin) series and the oceanic crust formed in the Paleozoic, and then triggered the partial melting of the juvenile lower crust, producing voluminous granitic melts and forming the Jietebutiao A2-type monzogranites, with the lithospheric mantle progressively thinning and rifting to form A1-type granites, such as syenogranites, in the Jietebutiao pluton. This further proves the important contribution of Late Paleozoic granitic magmatism in terms of vertical crustal growth in northern Xinjiang.

    • Geochemical Characteristics and Genesis of the Metallogenic Rocks in the Chagande’ersi Molybdenum Deposit in Wulatehouqi, Inner Mongolia

      2013, 87(1):148-157.

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      Abstract:Geochemical characteristics of the Chagande’ersi molybdenum deposit in Inner Mongolia and its genesis were analyzed in this study using rock mineralography and rock geochemical testing. The mineralized country rocks of the Chagande’ersi molybdenum deposit consist mainly of medium-to fine-grained monzogranite, medium-to fine-grained rich-K granite, with minor fine-grained K-feldspar granite veins and quartz veins. The rocks are characterized by high silica, rich alkali, high potassium, which are favorable factors for molybdenum mineralization. The rocks have the Rittmann index ranging from 1.329 to 1.961, an average Na2O+K2O value of 7.41, and Al2O3/(CaO+Na2O+K2O)>1, suggesting that the rocks belong to the high-K calc-alkaline peraluminous granite. The typical rock samples are enriched in Rb, Th, K and light rare earth elements, depleted in Sr, Ba, Nb, P and Ti, and these features are similar to that of the melt granite resulting from collision of plate margins. The δEu of the rocks falls the zone between the crust granite and crust-mantle granite, and are close to that of the crust granite; (La/Lu)N indicates the formation environment of granite is a continental margin setting. The Nb/Ta ratios are close to that of the average crust (10); the Zr/Hf ratios of monzogranite are partly below the mean mantle (34–60), while the Zr/Hf ratio of K-feldspar granite are close to the mean value in the crust. Comprehensive analyses show that the granite in this area formed during the transition period between tectonic collision and post-collision. During the plate collision and orogeny, the crust and mantle material were mixed physically, remelting into lava and then crystal fractionation, finally gave rise to the formation of the rock body in this area. This has close spatial and temporal relation with the molybdenum mineralization.

    • Platinum-Group Element Geochemical Characteristics of the Picrites and High-Ti Basalts in the Binchuan Area, Yunnan Province

      2013, 87(1):158-175.

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      Abstract:The Binchuan area of Yunnan is located in the western part of the Emeishan large igneous province in the western margin of the Yangtze Block. In the present study, the Wuguiqing profile in thickness of about 1440?m is mainly composed of high-Ti basalts, with minor picrites in the lower part and andesites, trachytes, and rhyolites in the upper part. The picrites have relatively higher platinum-group element (PGE) contents (ΣPGE=16.3–28.2 ppb), with high Cu/Zr and Pd/Zr ratios, and low S contents (5.03–16.9 ppm), indicating the parental magma is S-unsaturated and generated by high degree of partial melting of the Emeishan large igneous province (ELIP) mantle source. The slightly high Cu/Pd ratios (11?000–24?000) relative to that of the primitive mantle suggest that 0.007% sulfides have been retained in the mantle source. The PGE contents of the high-Ti basalts exhibit a wider range (ΣPGE=0.517–30.8 ppb). The samples in the middle and upper parts are depleted in PGE and have εNd (260?Ma) ratios ranging from ?2.8 to ?2.2, suggesting that crustal contamination of the parental magma during ascent triggered sulfur saturation and segregation of about 0.446%–0.554% sulfides, and the sulfide segregation process may also provide the ore-forming material for the magmatic Cu-Ni-PGE sulfide deposits close to the studied basalts. The samples in this area show Pt-Pd type primitive mantle-normalized PGE patterns, and the Pd/Ir ratios are higher than that of the primitive mantle (Pd/Ir=1), indicating that the obvious differentiation between Ir-group platinum-group elements (IPGE) and Pd-group platinum-group elements (PPGE) are mainly controlled by olivine or chromites fractionation during magma evolution. The Pd/Pt ratios of most samples are higher than the average ratio of mantle (Pd/Pt=0.55), showing that the differentiation happened between Pt and Pd. The differentiation in picrites may be relevant to Pt hosted in discrete refractory Pt-alloy phase in the mantle; whereas the differentiation in the high-Ti basalts is probably associated with the fractionation of Fe-Pt alloys, coprecipitating with Ir-Ru-Os alloys. Some high-Ti basalt samples exhibit negative Ru anomalies, possibly due to removal of laurite collected by the early crystallized chromites.

    • Rare Earth Elements Geochemistry of Sheikh-Marut Laterite Deposit, NW Mahabad, West-Azarbaidjan Province, Iran

      2013, 87(1):176-185.

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      Abstract:Laterite deposit at Sheikh-Marut (NW Mahabad, West-Azarbaidjan province, Iran) occurred within middle–upper Permian carbonate rocks. It consists of seven stratiform and/or discontinuous lenticular layers extending over 4.2 km in length and having thicknesses ranging from 3 to 14 m. Mineralogical data show that the ores contain kaolinite and hematite as major and boehmite, diaspore, halloysite, amesite, anatase, and muscovite-illite as minor mineral phases. The computed Ce anomaly values in the ores range from 0.05 to 20.84. Conservative index (e.g., Eu/Eu*) suggests that this deposit is a product of alteration and weathering of basaltic rocks. Rhythmic increment of ΣREE values of the ores with approaching to the carbonate bedrocks shows an in-situ occurrence of lateritization processes. Mass change calculations of elements indicate that two competing processes namely leaching and fixation were the major regulating factors in concentration variation of REEs (La–Lu) in this deposit. The obtained results show that pH increase of weathering solutions by carbonate bedrocks, existence of organic matters, and the degree of comlexation with organic ligands played remarkable role in distribution of REEs during lateritization. Further geochemical considerations revealed that secondary phosphates, Mn-oxides and -hydroxides, diaspore, and anatase were the potential hosts for REEs in this deposit.

    • Magnetic Fabric Study of Late Holocene Sediments in Huangqihai Lake, Inner Mongolia and its Sedimentary Significance

      2013, 87(1):186-196.

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      Abstract:The detailed magnetic susceptibility anisotropy study on the sediments of two sections, which are located in the lake-center and the lakeshore of the Huangqihai Lake, Inner Mongolia, revealed their hydrodynamics and sedimentary environment changes in the recent 2000 years. The results show that the sediments of two sections both display normal depositional magnetic fabrics, of which the minimum susceptibility axes (K3) are oriented perpendicular to the bedding plane and the maximum magnetic susceptibility axes (K1) lie parallel with the bedding plane. In addition, the lakeshore presents higher magnetic anisotropy degree (P), magnetic foliation (F) and current factor (Fs) than the lake-center, showing that the lakeshore has higher flow velocity. For the west Huangqihai Lake (HQW) section in the lake-center, the magnetic matrix grain degree (Q) and the inclination of the minimum susceptibility axes sharply increased and decreased, respectively, at a depth of about 10?cm, 24?cm, 45?cm and 74?cm, which indicate abnormal depositional events with strong kinetic energy. Through comparative analysis, the HQW section can be divided into three stages from top to bottom. The upper stage was a stable depositional environment with strong hydrodynamic energy and low water level, which shows relatively higher Fs value and the Q value varies similarly with P and F. The middle stage was a stable depositional environment with high water level and low hydrodynamic energy, intermitted with high-energy abnormal events, which shows relatively lower Fs and the Q value was negatively correlated with P and F. The lower stage was an unstable depositional environment with low hydrodynamic energy and high water level, which shows relatively lower P, F, and Fs value.

    • Deep-water Depositional Features of Miocene Zhujiang Formation in Baiyun Sag, Pearl River Mouth Basin

      2013, 87(1):197-210.

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      Abstract:Eleven lithofacies and five lithofacies associations were indentified in the Miocene Zhujiang Formation on the basis of detailed core analysis. It could be determined that three depositional types developed, namely submarine fan, basin and deep-water traction current. Six microfacies were further recognized within the fan, including main channels in the inner fan, distributary channels in the middle fan, inter-channels, levees and the outer fan. The lower Zhujiang Formation, mainly sandstone associations, was inner fan and inner-middle fan deposits of the basin fan and the slope fan. The middle part, mainly mudstone associations, was outer fan deposits. With the transgression, the submarine fan was finally replaced by the basinal pelagic deposits which were dominated by mudstone associations, siltstone associations, and deep-water limestone associations. During the weak gravity flow activity, the lower channels, the middle-upper outer fans and basin deposits were strongly modified by the deep-water traction current. The identification of the deep-water traction deposition in Miocene Zhujiang Formation would be of great importance. It could be inferred that the deep-water traction current had been existing after the shelf-break formation since the Late Oligocene (23.8?Ma) in the Baiyun sag, influencing and controlling the sediment composition, the distribution, and depositional processes. It would provide great enlightenment to the paleo-oceanic current circulation in the northern South China Sea.

    • Effect of Uncertainty of the Pre-Exponential Factor on Kinetic Parameters of Hydrocarbon Generation from Organic Matter and its Geological Applications

      2013, 87(1):211-218.

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      Abstract:The source rock sample of the Shahejie Formation (upper Es4) in Jiyang Sag was pyrolyzed under open system with the Rock-Eval-II apparatus, and then kinetic model parameters were calibrated for investigating the effect of uncertainty of pre-exponential factors on kinetic parameters and geological applications, where the parallel first-order reaction rate model with an average pre-exponential factor and discrete distribution activity energies was used. The results indicate that when the pre-exponential factor changes from low to high, an extreme value for residual errors occurs. And with the increasing pre-exponential factor, the distribution shape of activation energies are nearly the same, but the values of activation energies move higher integrally, and the average activation energy increases about 12?kJ/mol for every 10-fold of the pre-exponential factors. Extrapolating the geological heating rate of 3.3 °C/Ma, the results show that with the increases in pre-exponential factor, the geological temperature corresponding to TR0.5 (transforming ratio of hydrocarbon generation is 50%) increases gradually, and the additional temperature gradually decreases. Combined with geochemical data of source rock, the kinetic parameters with different pre-exponential factors are used to calculate the transformation ratio of hydrocarbon generation, and the result indicates that kinetic parameters corresponding to the better optimized pre-exponential factor are more suitable. It is suggested that the risk assessment of hydrocarbon generation kinetic parameters should be enhanced when using the kinetic method to appraise the oil-gas resources. Meantime, the application result of different kinetic parameters should be verified with geological and geochemical data of source rock in the target area; therefore, the most suitable kinetic parameters for target can be obtained.

    • Main Controlling Factors and Dominant Reservoir Series Analysis of Es3 in the Qibei Area of Qikou Sag

      2013, 87(1):219-231.

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      Abstract:Based on analysis of geophysical data such as core observation, rock slices identification, physical property, scanning electron microscope, X-ray diffraction, logging data etc., 16 factors of sedimentation, diagenesis, fluid pressure, and their relationships with reservoir physical property were analyzed, and the results indicate sedimentation is the internal factor controlling the reservoir property, diagenesis is the external and final decisive factor and abnormal fluid pressure is an important factor preserving the deep reservoir property. Quantitative characterization of diagenesis indicates that compaction and dissolution are more important than cementation and they respectively cause porosity change of ?23.6% and 7.7% and ?6.2%. Through optimizing 11 main controlling factors and constructing reservoir evaluation index (REI) according to the hierarchical cluster and principal component analysis, reservoir classification standard was established and reservoirs were divided into four classes. The studies show that Es32SQ4 consists mainly of class I and II, while Es32SQ6 is mainly of class III and II; the favorable zone is the north and south slope of Qibei sub-sag and the Liujianfang fault-nose. The successful application of the quantitative and comprehensive evaluation in the Qibei area verifies the advanced, practicable method of less artificial factor is suitable for the low porosity and permeability reservoir.

    • Quantitative Analysis Model and Application of the Hydrocarbon Distribution Threshold

      2013, 87(1):232-242.

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      Abstract:Hydrocarbon source rock obviously controls the formation and distribution of hydrocarbon reservoirs. Based on the geological concept of “source control theory”, the concept of a hydrocarbon distribution threshold was put forward. This means the maximum range for hydrocarbon controlled by the source rock conditions to migrate in the hydrocarbon basins. Three quantitative analysis models are proposed on this basis, namely the hydrocarbon accumulation probability, maximum hydrocarbon scale threshold and reserve distribution probability, which respectively refer to the probability of forming a hydrocarbon reservoir, the possible maximum scale of the hydrocarbon reservoir and the percentage of reserve distribution in a certain area within the hydrocarbon distribution threshold. Statistical analysis on 539 hydrocarbon reservoirs discovered in 28 hydrocarbon source kitchens from seven sedimentary basins and sags of eastern China shows the maximum reservoir scale possibly formed in the hydrocarbon basin, hydrocarbon accumulation probability and oil and gas reserve distribution probability are all controlled by the characteristics of the hydrocarbon source rock. Generally, as the distances from the hydrocarbon source rock center and hydrocarbon discharge boundary get longer and the hydrocarbon discharge intensity of hydrocarbon source rock center gets smaller, there will be lower probability of hydrocarbon accumulation. Corresponding quantitative models are established based on single factor statistics and multivariate analysis. Practical application in the Jiyang Depression shows that the prediction from the quantitative analysis model for the hydrocarbon distribution threshold agree well with the actual exploration results, indicating that the quantitative analysis model is likely to be a feasible tool.

    • Groundwater Flow Simulation and its Application in Groundwater Resource Evaluation in the North China Plain, China

      2013, 87(1):243-253.

      Abstract (1650) HTML (0) PDF 8.09 M (1682) Comment (0) Favorites

      Abstract:The purpose of this study is to establish a 3D groundwater flow modelling for evaluating groundwater resources of the North China Plain. First, the North China Plain was divided into three aquifers vertically through a characterization of hydrogeological conditions. Groundwater model software GMS was used for modeling to divide the area of simulation into a regular network of 164 rows and 148 lines. This model was verified through fitting of the observed and the simulated groundwater flow fields at deep and shallow layers and comparison between the observed and simulated hydrographs at 64 typical observation wells. Furthermore, water budget analysis was also performed during the simulation period (2002-2003). Results of the established groundwater flow model showed that the average annual groundwater recharge of the North China Plain during 1991 to 2003 was 256.68×108 m3/yr with safe yield of groundwater resources up to 213.49×108 m3/yr, in which safe yield of shallow groundwater and that of deep groundwater was up to 191.65×108 m3/yr and 22.64×108 m3/yr respectively. Finally, this model was integrated with proposal for groundwater withdrawal in the study area after commencement of water supply by South-North Water Transfer Project, aiming to predict the changing trend of groundwater regime. As indicated by prediction results, South-North Water Transfer Project, which is favorable for effective control of expansion and intensification of existing depression cone, would play a positive role in alleviation of short supply of groundwater in the North China Plain as well as maintenance and protection of groundwater.

    • Recurrence Characteristics of Major Earthquakes in the Tangshan area, North China

      2013, 87(1):254-271.

      Abstract (2145) HTML (0) PDF 7.89 M (1789) Comment (0) Favorites

      Abstract:The Tangshan area lies in the North China plain where an Ms 7.8 earthquake occurred in 1976, which is associated with a hidden active fault. To reveal the recurrence characteristics of major quakes in this area over a relatively long time, we have conducted a comprehensive study using geological investigations, shallow seismic exploration, boreholes, trench observations and geological dating. Five paleoearthquakes were recognized in a 6.4m-deep trench west to the Tangshan Asylum. Among them, the former three events occurred between 56.78?±?4.83ka and 89.39?±?7.60?ka, and the fourth event occurred around 6.9?ka, respectively, and then followed by the fifth in 1976. Seven boreholes were deployed crossing the ground fissure formed by the 1976 Tangshan earthquake at the site of No. 10 Middle School, where we have identified 25 liquefaction events in the boreholes TZC6–5 and 6–7. By the comprehensive analysis of the trench, the liquefaction events from the boreholes and the depth-time curves of drill cores, we suggest a new recurrence model of major quakes in this area. It is not a constant recurring cycle since 210?ka, instead consisting of six alternating seismically quiet and active stages. Of them, stage I (>177?ka) was a quiescent period in seismicity, stage II (from 143?ka to 177?ka) was an active one, stage III (from 102?ka to 143?ka) was quiescent again, stage IV (from 56?ka to 102?ka) had many quakes, stage V (from 6.9?ka to 56?ka) became quiet, and stage VI (from 6.9?ka to now) was the beginning of a new seismically active period.

    • Application of the Engineering-Geological Conditions in Land-Use Plans in the Petrvald Region (Czech Republic)

      2013, 87(1):272-285.

      Abstract (1634) HTML (0) PDF 7.42 M (1950) Comment (0) Favorites

      Abstract:The objective of this paper is to demonstrate necessity to inform relevant parties about engineering-geological conditions for various practical purposes, especially including appropriate land-use planning. However, the relationship between relevant geological information and the geological environment is vital for foundation engineering purposes, especially where demanding structures are involved. This information is most conveniently structured when accumulated information concerning engineering-geological zones is utilized. This necessarily includes knowledge of rock workability and also of the pre-Quaternary bedrock, and these characteristics were then related to the current built-up area and future development according to the land-use plans in a case study are from the Petrvald Region (Czech Republic). The geological environment of area has been severely influenced by anthropogenic effects of deep black coal mining. Results of this research showed that future development should be founded on spoil banks, dumps, and settling basins. According to the land-use plan, this zone occupies 44.9% of the area of interest, and its materials predominantly emanate from mining in the Ostrava–Karvina Coal District. For future foundation structures planned there, it is imperative to consult detailed engineering-geological study. However, attention to and reliance on this necessity is not reflected in the existing land-use plan.

    • Comprehensive Utilization of Vanadium–Titanium Magnetite Deposits in China Has Come to a New Level

      2013, 87(1):286-287.

      Abstract (1575) HTML (0) PDF 1.28 M (1548) Comment (0) Favorites

      Abstract:

    • China Output of Crude Oil Hits High in 2012

      2013, 87(1):287-287.

      Abstract (1614) HTML (0) PDF 547.39 K (1452) Comment (0) Favorites

      Abstract:

Chief Editor:HOU Zengqian

Governing Body:China Association for Science and Technology

Organizer:Geological Society of China

start publication :1922

ISSN:ISSN 1000-9515

CN:CN 11-2001/P

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