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摘要:The Xining basin is located in the northeastern margin of the Qinghai-Tibet Plateau. It is a rift basin formed in Mesozoic and Cenozoic and structurally belongs to the intersection of Kunlun and Qilian Mountains. Cenozoic fluvial and lacustrine sedimentary strata are continuous in the Xining basin, with a thickness of more than 800 m, completely recording the deformation uplifting, weathering and denudation history and climate change process of the northeastern plateau. Currently, early Miocene Xijia fauna, early Middle Miocene Danshuilu fauna and late Middle Miocene Diaogou fauna are discovered in the Xining basin, which provide an important basis for the stratigraphic correlation of the Cenozoic strata in the Xining basin. However, in the next few decades, there are no reports about the large mammal fossils in the Xining basin, especially about late Miocene fauna. The author discovered a large amount of mammal fossils in the Neogene sedimentary strata in Huzhu area, Xining basin. According to the identification results of the Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, these fossils mainly included Hipparion dongxiangense, Chilotherium sp., Parelasmotherium sp., Stephanocemas sp. and Kubanochoerus sp. and their age was early Late Miocene. Since the discovery of this set of fossils directly filled the blank that there were no large mammal fossils in the Xining basin in Late Miocene, it was very important for studying the magnetic stratigraphic chronology of fossil-forming strata and establishing the paleomagnetic chronology scale plate of mammal fossils. In this paper, the paleomagnetic data of the fossil-forming stratigraphic profile, Banyan profile, were measured and the paleomagnetic records were collected through high density sampling, and finally the paleomagnetic polarity column of the profile was established. The results showed that five positive and five negative polarity segments were recorded in Banyan profile, which corresponded well to the polarity between C3Br.1n-C4n.2n in the standard polarity column. The age of profile top was about 7.25 Ma and profile bottom was about 8.4 Ma, with an age range of 1.15 Ma. The mammal fossils discovered this time were exposed between positive and negative polarities N5 and R5 at the bottom of the profile, corresponding to C4r.1r at negative polarity and C4n.2n at positive polarity in the standard polarity column. The age of mammal fossils was about 8.3 Ma. The paleomagnetic chronology of the strata and paleontological fossils determined the absolute age of late Miocene mammal fossils and expanded the upper age of late Miocene Xianshuihe Formation (N1xn) in the Xining basin, which had provided new basic data for further studying the stratigraphic deposition and correlation of late Cenozoic strata and regional environmental evolution.

摘要:The Oligocene–Miocene carbonate record of the Zagros Mountains, known as the Asmari Formation, constitutes an important hydrocarbon reservoir in southern Iran. This marine carbonate succession, which developed under tropical conditions, is explored in terms of larger foraminiferal biostratigraphy, facies analysis and sequence stratigraphy in a new section at Papoon cropping out in the western Fars sub-basin, in the south-east of the Zagros belt. Facies analysis shows evidence of re-working and transport of skeletal components throughout the depositional system, interpreted here as a carbonate ramp. The foraminifera-based biozones identified include the Globigerina–Turborotalia cerroazulensis–Hantkenina Zone and Nummulites vascus–Nummulites fichteli Zone, both of Rupelian age, the Archaias asmaricus–Archaias hensoni–Miogypsinoides complanatus Zone of Chattian age and the ‘Indeterminate’ Zone of Aquitanian age. The vertical sedimentary evolution of the formation exhibits a progressive shallowing of the facies belts and thus the succession is interpreted as a high-rank low-order regressive systems tract. This long-lasting Rupelian–Aquitanian regressive event is in accordance with accepted global long-term eustatic curves. Accordingly, long-term eustatic trends would have been a factor controlling accommodation during the deposition of the Asmari Formation studied in the western Fars sub-basin.

摘要:The Laojiezi alkaline volcanic rocks, which are located in the intraplate region of the Yangtze craton, coincide with the formation of the Jinshajiang-Ailaoshan-Red River alkaline rock belt. Although this belt has been widely studied by geologists because of its porphyry-related Pb-Ag-Au polymetallic deposit and geotectonic location, the material sources of this belt are still debate. Whole-rock analyses show that these rocks have high total alkali contents (3.73–11.08wt%), and their aluminum saturation index (ASI) values widely vary from 0.82 to 3.07, which comprise a metaluminous-peraluminous magma series. These rocks are characterized by high K (K2O/Na2O>1) and low Ti and Mg contents; enrichment in large-ion lithophile elements, such as Rb, Ba, K and light rare earth elements; and depletion in high field strength elements, such as Ta, Nb, P, and Ti. These rocks exhibit moderate Eu (Eu/Eu*=0.86–1.04) and Ce (Ce/Ce*=0.63–0.96) anomalies. Their (87Sr/86Sr)i, εNd(t), zircon εHf(t) and δ18O values range from 0.70839 to 0.71013, from ?10.16 to ?12.45, from ?19.6 to ?5.8, and from 5.69‰ to 8.54‰, respectively, and their Nd and Hf two-stage model ages (TDM2) are 1.67–1.86 Ga and 1.27–2.02 Ga, respectively. These data reflect the primary partial melting of Paleoproterozoic to Mesoproterozoic lower crust with minor residual continental lithospheric mantle and supracrustal metasediments. The lithosphere was likely thickened along the southeastern margin of the Tibetan Plateau following the Indian-Asian continent-continent collision (65–41 Ma). During the post-collision phase (36–16 Ma), the transition from a compressional to extensional setting triggered the convective removal of the over-thickened CLM beneath the Yangtze craton, which led to the upwelling of asthenospheric materials. This process created alkali-rich and high-K magma through the partial melting of the thickened lower crust. Magma that carried Cu-Au-Pb-Ag minerals was emplaced by strike-slip motion along the E- to W- or ENE- to WSW-trending tectonically weak zone, finally forming an alkaline porphyry Cu-Au-Pb-Ag polymetallic deposit.

摘要:A new method for determining?the partial melting depth of mantle-derived magma and lithospheric thickness in continental regions is derived from REE geochemistry. This effective technique uses variations in the Ce/Yb and Sm/Yb ratios found in mainly volcanic rocks in continental China. The ratios change with the depth of origin consistent with the correlation between lithospheric thickness and the Ce/Yb and Sm/Yb ratios found in oceanic basalt. These ratios increase exponentially with the depth of origin, the lithospheric thickness, of a wide variety of Cenozoic volcanic basalt and Paleozoic kimberlite in the North China Craton, northeastern China continent and vicinity. This functional relationship with depth is shown in a plot of the ratios that forms a concordia curve, which is closely expressed by formulas using 8–degree polynomials. These provide a more accurate gage in measuring the lithospheric thickness than the traditional geophysical methods. When applied to volcanic rock of different ages it also reveals how the thickness has changed over time and thus, greatly aids the understanding of the tectonic history. Relations between the CO2 content, mineral reactions and pressure in the upper asthenosphere beneath the base of the lithosphere appears to affect the proportions of REE in partial melts and brings about a close correlation between lithospheric thickness and the Ce/Yb and Sm/Yb ratios in mantle–derived magmatic rock. This thickness gauge, for both continental and oceanic lithosphere, provides a new approach in analyzing the lithospheric thickness in different tectonic settings and geologic times.

摘要:The metasedimentary Lujiapuzi Formation crops out along the northeastern margin of the North China Craton, close to the Yan-Liao Rift. The age and tectonic setting of the formation, and its relationship with the Yan-Liao Rift are currently unclear. Here we present detrital zircon U-Pb ages, and Hf isotopic and geochemical data for the Lujiapuzi Formation to constrain the timing of deposition, the provenance of the formation, and the regional stratigraphy relationship. Zircon U-Pb dating constrains the timing of deposition of the Lujiapuzi Formation to younger than 1780 Ma, and indicates that most grains were sourced from the Longgang Block and the Paleoproterozoic Liao-Ji Belt. Detailed field investigations and a correlation of the regional stratigraphy reveal that much of the Lujiapuzi Formation is equivalent to the Tuanshanzi Formation in the Yan-Liao Rift; the lower section may represent the earliest sediments deposited within the Fanhe Basin. Based on these results and the findings of previous studies, we suggest that the base of the Changcheng System has an age of 1.80 Ga. Zircon Hf isotopic data indicate that the main period of crustal growth along the northeastern margin of the North China Craton occurred at 3.2–2.5 Ga, with a peak at 2.9–2.7 Ga.

摘要:Post-collisional volcanic rocks of Mesozoic age occur in the regions adjacent to Gerze, part of the southern Qiangtang Terrane of northern Tibet, China. Geochronological, geochemical, and whole-rock Sr-Nd isotopic analyses were performed on the volcanic rocks to better characterize their emplacement age and models for their origin. Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) U-Pb zircon analyses yielded consistent ages ranging from 123.1±0.94 Ma to 124.5±0.89 Ma for six volcanic rocks from the study area. The intermediate volcanic rocks belong to the alkaline and sub-alkaline magma series in terms of K2O+Na2O contents (5.9%–9.0%), and to the shoshonitic and calc-alkaline series on the basis of their high K2O contents (1.4%–3.3%). The Gerze volcanic rocks are characterized by the enrichment of light rare earth elements [(La/Yb)N=34.9–49.5] and large–ion lithophile elements (e.g., Rb, Ba, Th, U, K, Pb, and Sr), slightly negative Eu anomalies (Eu/Eu*=0.19–0.24), and negative anomalies in high field strength elements (e.g., Nb, Ta, Hf and Ti), relative to primitive mantle. The samples show slightly elevated (87Sr/86Sr)i values that range from 0.7049 to 0.7057, and low εNd(t) values from ?0.89 to ?2.89. These results suggest that the volcanic rocks studied derived from a compositionally heterogeneous mantle source and that their parent magmas were basaltic. The more mafic, parental magmas to the Gerze volcanic rocks likely underwent fractional crystallization of clinopyroxene, hornblende, biotite, and potassium feldspar, during ascent, with little to no crustal contamination, prior to their eruption/emplacement. While these volcanic rocks exhibit geochemical signatures typical of magmas formed in a destructive plate-margin setting, it is plausible that their mantle source might also have acquired such characteristics in an earlier episode of subduction.

摘要:Unusual carbonaceous matter, termed here chiemite, composed of more than 90% C from the Alpine Foreland at Lake Chiemsee in Bavaria, southeastern Germany has been investigated using optical and atomic force microscopy, X-ray fluorescence spectroscopy, scanning and transmission electron microscopy, high-resolution Raman spectroscopy, X-ray diffraction and differential thermal analysis, as well as by δ13C and 14C radiocarbon isotopic data analysis. In the pumice-like fragments, poorly ordered carbon matter co-exists with high-ordering monocrystalline α-carbyne, and contains submicrometer-sized inclusions of complex composition. Diamond and carbyne add to the peculiar mix of matter. The required very high temperatures and pressures for carbyne formation point to a shock event probably from the recently proposed Holocene Chiemgau meteorite impact. The carbon material is suggested to have largely formed from heavily shocked coal, vegetation like wood, and peat from the impact target area. The carbonization/coalification high PT process may be attributed to a strong shock that instantaneously caused the complete evaporation and loss of volatile matter and water, which nevertheless preserved the original cellular structure seen fossilized in many fragments. Relatively fresh wood encapsulated in the purported strongly shocked matter point to quenched carbon melt components possibly important for the discussion of survival of organic matter in meteorite impacts, implying an astrobiological relationship.

摘要:Organic-inorganic interactions occurring in petroleum-related mud volcanoes can help predict the chemical processes that are responsible for methane emissions to the atmosphere. Seven samples of mud breccia directly ejected from one crater were collected in the Dushanzi mud volcano, along with one argillite sample of the original reddish host rocks distal from the crater, for comparison purposes. The mineral and chemical compositions as well as iron species of all samples were determined using XRD, XRF and M?ssbauer spectroscopy, respectively. The results indicate that a series of marked reactions occurred in the mud volcano systems, more specifically in the mud breccia when compared to the original rocks. Changes mainly included: (1) some conversion of clay minerals from smectite into chlorite and illite, and the precipitation of secondary carbonate minerals such as calcite and siderite; (2) silicon depletion and significant elemental enrichment of iron, manganese, magnesium, calcium and phosphorus; and (3) transformation of iron from ferric species in hematite and smectite into ferrous species in siderite, chlorite and illite. These geochemical reactions likely induced the color changes of the original reddish Neogene argillite to the gray or black mud breccia, as a result of reduction of elements and/or alteration of minerals associated with the oxidation of hydrocarbons. Our results also suggest that greenhouse gases emitted from the mud volcanoes are lowered through a series of methane oxidation reactions and carbon fixation (i.e., through carbonate precipitation).

摘要:The 300±20 Ma anomalously radioactive trachytes of Wadi El Kareim, central Eastern Desert, are a significant example of U-mineralization related to the alkaline volcanics in Egypt. Extensive portable gamma-ray spectrometric data has been utilized to identify geological factors controlling uranium mobility in the geological units along the three detailed study locations of Kab Al-Abyad, South Wadi (W) Al-Tarafawy and W. Al-Farkhah; their eTh/eU ratios averaging around 4.1, 3.7 and 5.6 respectively. Quantitative analysis with the integration of mobility maps and geological studies suggest two systems controlling U-migration within the geological units (confined system and unconfined system). In the confined system, the syngenetically formed U have experienced mobility after leaching and are redistributed in the presence of an incorporation carrier during transportation (probably as carbonate complexes). Then the retardant for uranium is achieved by sorption or by coprecipitation with the aid of Fe oxy-hydroxide, and finally the formation of immobile secondary U-bearing minerals takes place along a lithogeochemical trap. In contrast to the confined system, the unconfined one is basically lacking the lithogeochemical trap which in?uences the final accumulation of U-bearing minerals. The radioactivity of the trachyte rocks arises from the radioactive minerals uranophane and beta-uranophane with U- and/or Th-bearing minerals samarskite, Th-rich REE silicates, monazite and allanite.

摘要:Potassium-rich brine in the Sichuan Basin has been much studied in recent years, but few studies have focused on the distribution and migration of salt basin and the differences of potassium formation mechanisms. This work examined the salt-gathering and potassium formation of potassium-rich brine during the Triassic in the Sichuan Basin using lithofacies palaeogeographic depiction and geochemical analyses. (1) The favorable sedimentary facies controlling the formation of potassium-rich brine during the Triassic in the Sichuan Basin are evaporation platform and restricted platform, whereas the salt basin is one of the main factors controlling the poly-salt center. (2) The distribution and migration of this salt basin were affected by certain factors. The salt basin of the Jialingjiang Formation was mainly distributed in the east and central Sichuan Basin, whereas that of the Leikoupo Formation was mainly distributed in the central and west Sichuan Basin. The sedimentary centers have gradually moved westward and become smaller. (3) Three main formation mechanisms were identified for the potassium-rich brine during the Triassic in the Sichuan Basin, i.e., evaporation and concentration of seawater, surface fresh water leaching, and deep water-rock reaction. Fresh water leaching was characterized by low anomaly δ18O and δ13C values. Water-rock reaction was mainly related to temperature, and high temperature environment (caused by burial depth, overthrust and deep hydrothermal fluids) was beneficial to water-rock reaction. The characteristics of water-rock reaction do not correspond to the increase ratio of K?103/Cl and Br?103/Cl in brine, and the Rb+ content of the brine was high. (4) The formation mechanisms of potassium-rich brine differed between different areas of the Sichuan Basin. In east Sichuan, the evaporation and concentration of seawater, together with meteoric fresh water leaching, was the main formation factor, whereas the evaporation and concentration of seawater and water–rock reaction predominated in west Sichuan. This study of the sedimentary environment and formation mechanisms is of significance to the exploration and exploitation of potassium-rich brine in the Sichuan Basin.

摘要:The Mohe permafrost in northeast China possesses favorable subsurface ambient temperature, salinity, Eh values and pH levels of groundwater for the formation of microbial gas, and the Mohe Basin contains rich organic matter in the Middle Jurassic dark mudstones. This work conducted gas chromatography and isotope mass spectrometry analyses of nearly 90 core gas samples from the Mk-2 well in the Mohe Basin. The results show that the dryness coefficient (C1/C1–5) of core hydrocarbon gas from approximately 900 m intervals below the surface is larger than 98%, over 70% of the δ13C values of methane are smaller than ?55‰, and almost all δD values of methane are smaller than ?250‰, indicative of a microbial origin of the gas from almost 900 m of the upper intervals in the Mohe permafrost. Moreover, the biomarker analyses of 72 mudstone samples from the Mohe area indicate that all of them contain 25-norhopane series compounds, thereby suggesting widely distributed microbial activities in the permafrost. This work has confirmed the prevailing existence of microbial gas in the Mohe area, which may be a potential gas source of gas hydrate formation in the Mohe permafrost. This result is of great significance to gas hydrate accumulation in the permafrost across China.

摘要:Micropores of shale are significant to the gas content and production potential of shale, which has been verified in the research of marine shale gas; while, few studies have been conducted on lacustrine shales. This study collected 42 samples from three wells in the Late Cretaceous Qingshankou Formation of the southern Songliao Basin, NE China, and investigated these samples by the focused ion beam-scanning electron microscope (FIB–SEM) and nitrogen adsorption analysis techniques. Four types of micropores were identified in the samples, i.e., intergranular pore, intracellular pore, organic matter pore and microfracture. The pore structure type is characterized by open slit pores and “ink type” pores which are mainly 1.5–5 nm in diameter with mesopores as the main pores. The mesopores account for 74.01% of the pore volume and 54.68% of the pore surface area. Compared with the lacustrine shales from the Triassic Yanchang Formation in the Ordos Basin and Xujiahe Formation in the Sichuan Basin, the intergranular clay mineral interlayer pores are considered to be the main reservoir space for shale gas storage in the study area, followed by intraparticle pores, organic matter pores and microfractures. Maturity and micropore are the key controlling factors which affect the shale gas content of the Qingshankou Formation in southern Songliao Basin.

摘要:After two well tests in the Asmari well#A, located in the North Dezful zone, it was concluded that in the Jurassic Mus/Alan/Neyriz and Upper Sargelu reservoirs, highly mature colorless oil and gas were trapped, including 4%-6% H2S. The alternation of Garau shale and the Gotnia anhydrite seal was so efficient that it did not allow the upward migration of petroleum from Jurassic reservoirs to higher levels. Descriptive ratios, chromatograms, pick correlation and cross plots demonstrated that the oil and gas have been derived from a TOC-enriched sequence, consisting of the base of the Garau and the top of the Sargelu Formations. This highly organic matter-rich sequence is traceable as an oil shale in other parts of the North Dezful zone, such as the Gashun section. The petroleum accumulations in both reservoirs are identical, have the same maturity and the same source. Diagrams of δ13C2 versus δ13C3, δ13C1 versus wetness of gas (C1/C2+C3) and δ13C1 versus δDC1 suggest that the gas is derived from a highly mature source. There are indications of TSR effects on the original petroleum that could have changed the volumetric and isotopic composition of the oil and gas. This result requires more careful study of the petroleum components to be undertaken.

摘要:Original organisms are the biological precursors of organic matter in source rocks. Original organisms in source rocks are informative for oil-source rock correlation and hydrocarbon potential evaluation, especially for source rocks which have high-over level of thermal maturity. Systematic identification of original organism assemblages of the Lower Paleozoic potential source rocks and detailed carbon isotopic composition of kerogen analyses were conducted for four outcrop sections in the Tarim basin. Results indicated that the original organism assemblages of the lower part of the Lower Cambrian were composed mainly of benthic algae, whereas those of the Upper Cambrian and the Ordovician were characterized by planktonic algae. Kerogen carbon isotopic data demonstrated that the δ13Ckerogen values of source rocks dominated by benthic algae are lower than ?34‰, whereas the δ13Ckerogen values of source rocks dominated by planktonic algae are higher than ?30‰ in general. We tentatively suggested that the carbon species those are utilized by algae and the carbon isotopic fractionation during photosynthesis are the major controls for the δ13Ckerogen values in the Lower Paleozoic source rocks in the Tarim basin. Correlating the δ13C values of oils exploited in the Tarim basin, the original organism assemblages, and δ13Ckerogen values of source rocks, it implied that the Lower Paleozoic oils exploited in the Tarim basin should be sourced from the source rocks with original organism assemblages dominated by planktonic algae, and the hydrocarbon sourced from the Cambrian benthic algae should be of great exploration potential in future. Original organism assemblages in source rocks can provide important clues for oil-source rocks correlation, especially for the source rocks with high thermal maturity.

摘要:Coalbed methane (CBM) resources in No.15 coal seam of Taiyuan Formation account for 55% of the total CBM resources in southern Qinshui Basin (SQB), and have a great production potential. This study aims at investigating the CBM production in No.15 coal seam and its influence factors. Based on a series of laboratory experiments and latest exploration and development data from local coal mines and CBM companies, the spatial characteristics of gas production of No.15 coal seam were analyzed and then the influences of seven factors on the gas productivity of this coal seam were discussed, including coal thickness, burial depth, gas content, ratio of critical desorption pressure to original coal reservoir pressure (RCPOP), porosity, permeability, and hydrogeological condition. The influences of hydrological condition on CBM production were analyzed based on the discussions of four aspects: hydrogeochemistry, roof lithology and its distribution, hydrodynamic field of groundwater, and recharge rate of groundwater. Finally, a three-level analytic hierarchy process (AHP) evaluation model was proposed for predicting the CBM potentials of the No.15 coal seam in the SQB. The best prospective target area for CBM production of the No.15 coal seam is predicted to be in the districts of Panzhuang, Chengzhuang and south of Hudi.

摘要:The Jurassic Yanan Formation is one of the most important coal-producing formations and hydrocarbon source rocks in the Ordos Basin, North China. To evaluate the shale gas potential of the Yanan shale, a total of 48 samples from north Ordos Basin were sampled, and their geochemical, petrological, mineralogical and pore characteristics were investigated. It was found that the shale samples are a suite of early mature source rock. The total organic carbon (TOC) content ranges from 0.33% to 24.12% and the hydrogen index (HI) ranges from 43.31mg/g to 330.58 mg/g. The relationship between Tmax and HI indicates the organic matter is type Ⅱ-Ⅲ. This conclusion is also supported by the organic petrological examination results, which shows that the kerogen is mainly liptinite and vitrinite. Minerals in the samples are composed mainly of quartz, clay and feldspar, and the clay minerals are composed of prevailing kaolinite, illite/smectite, chlorite and a small amount of illite. Under scanning electron microscope, OM pores in the Yanan shale are scarce except pores come from the kerogen intrinsic texture or clay aggregates within the organic particles. As the weak compaction caused by shallow burial depth, interparticle pores and intraparticle pores are common, the hydrocarbon storage capacity of the Yanan shale was improved. According to evaluation, the Yanan shale is considered as a good shale gas reservoir, but its hydrocarbon potential is more dependent on biogenic and coal-derived gas as the thermogenic gas is limited by the lower thermal maturity.

摘要:Shale gas has currently attracted much attention during oil and gas exploration and development. Fractures in shale have an important influence on the enrichment and preservation of shale gas. This work studied the developmental period and formation mechanism of tectonic fractures in the Longmaxi Formation shale in the Dingshan area of ??southeastern Sichuan Basin based on extensive observations of outcrops and cores, rock acoustic emission (Kaiser) experiments, homogenization temperature of fracture fill inclusions, apatite fission track, thermal burial history. The research shows that the fracture types of the Longmaxi Formation include tectonic fractures, diagenetic fractures and horizontal slip fractures. The main types are tectonic high-angle shear and horizontal slip fractures, with small openings, large spacing, low densities, and high degrees of filling. Six dominant directions of the fractures after correction by plane included NWW, nearly SN, NNW, NEE, nearly EW and NW. The analysis of field fracture stage and fracture system of the borehole suggests that the fractures in the Longmaxi Formation could be paired with two sets of plane X-shaped conjugate shear fractures, i.e., profile X-shaped conjugate shear fractures and extension fractures. The combination of qualitative geological analysis and quantitative experimental testing techniques indicates that the tectonic fractures in the Longmaxi Formation have undergone three periods of tectonic movement, namely mid-late Yanshanian movement (82–71.1 Ma), late Yanshanian and middle Himalaya movements (71.1–22.3 Ma), and the late Himalayan movement (22.3–0 Ma). The middle-late period of the Yanshanian movement and end of the Yanshanian movement-middle period of the Himalayan movement were the main fracture-forming periods. The fractures were mostly filled with minerals, such as calcite and siliceous. The homogenization temperature of fracture fill inclusions was high, and the paleo-stress value was large; the tectonic movement from the late to present period was mainly a slight transformation and superposition of existing fractures and tectonic systems. Based on the principle of tectonic analysis and theory of geomechanics, we clarified the mechanism of the fractures in the Longmaxi Formation, and established the genetic model of the Longmaxi Formation. The research on the qualitative and quantitative techniques of the fracture-phase study could be effectively used to analyze the causes of the marine shale gas fractures in the Sichuan Basin. The research findings and results provide important references and technical support for further exploration and development of marine shale gas in South China.

摘要:The Permian global mass extinction events and the eruption of the Emeishan flood basalts in the Upper Yangtze region should display certain responses during the evolution of carbon isotope. In this paper, the Permian carbon isotopic evolution in the Upper Yangtze region is examined through systematic stratotype section sampling and determination of 13C in the northern Upper-Yangtze regions and Southern China. Additionally, the carbon isotopic evolution response characteristics of the geological events in the region are evaluated, comparing the sea-level changes in the Upper Yangtze region and the global sea-level change curves. Results of this study indicated that the carbon isotopic curves of the Permian in the Upper Yangtze region are characterized by higher background carbon-isotope baseline values, with three distinct negative excursions, which are located at the Middle–Late Permian boundary and the late period and end of the Late Permian. The three distinct negative excursions provide an insightful record of the global Permian mass extinction events and the eruption of the Emeishan flood basalts in the Upper Yangtze region. The first negative excursion at the Middle–Late Permian boundary reflected the eruption of the Emeishan flood basalts, a decrease in sea level, and biological extinction events of different genera in varying degrees. The second negative excursion in the Late Permian included a decrease in sea level and large-scale biological replacement events. The third negative excursion of the carbon isotope at the end of the Permian corresponded unusually to a rise rather than a decrease in sea level, and it revealed the largest biological mass extinction event in history.

摘要:This study considered the possibility of using visible and near infrared (VNIR) spectral absorption feature parameters (SAFPs) in predicting the concentration and mapping the distribution of heavy metals in sediments of the Takab area. In total, 60 sediment samples were collected along main streams draining from the mining districts and tailing sites, in order to measure the concentration of As, Co, V, Cu, Cr, Ni, Hg, Ti, Pb and Zn and the reflectance spectra (350–2500 nm). The quantitative relationship between SAFPs (Depth500nm, R610/500nm, R1344/778nm, Area500nm, Depth2200nm, Area2200nm, Asym2200nm) and geochemical data were assessed using stepwise multiple linear regression (SMLR) and enter multiple linear regression (EMLR) methods. The results showed a strong negative correlation between Ni and Cr with Area2200nm, a significant positive correlation between As and Asym2200nm, Ni and Co with Depth2200nm, as well as Co, V and total values with Depth500nm. The EMLR method eventuated in a significant prediction result for Ni, Cr, Co and As concentrations based on spectral parameters, whereas the prediction for Zn, V and total value was relatively weak. The spatial distribution pattern of geochemical data showed that mining activities, along with the natural weathering of base metal occurrences and rock units, has caused high concentrations of heavy metals in sediments of the Sarough River tributaries.

摘要:Water-rich clay to sand suspensions show a shear rate dependent flow behavior and knowledge of the appropriate rheological model is relevant for sedimentological, industrial and hydraulic studies. We present experimental rheological measurements of water-rich (40 to 60 wt%) clay to silt (population A) and silt to sand (population B) suspensions mixed in different proportions. The data evidence a shear rate dependent shear thinning-shear thickening transition. At lower shear rates, the suspensions organize in chains of particles, whereas at higher shear rates, these chains disrupt so increasing the viscosity. The viscosity, consistency and yield stress decrease as the A+B fraction decreases as the content of B particles increases. This behavior reflects the competing effects of the lubrication and frictional processes as a function of particle size and water content. Transitional flows form by the incorporation of small amounts of the finer fraction while ‘oceanic floods’ form at the estuary of rivers and the submarine debris-flows increase their velocity by incorporating water. The critical Reynolds number of the studied suspensions is ~2000±100 suggesting that the grainsize plays a major role in the laminar to turbulent transition. Our results have implications for the modeling of sediment flows and the hazard related to floods.

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摘要:Located in Iranian sector of the Persian Gulf, Foroozan Oilfield has been producing hydrocarbons via seven different reservoirs since the 1970s. However, understanding fluid interactions and horizontal continuity within each reservoir has proved complicated in this field. This study aims to determine the degree of intra-reservoir compartmentalization using gas geochemistry, light hydrocarbon components, and petroleum bulk properties, comparing the results with those obtained from reservoir engineering indicators. For this purpose, a total of 11 samples of oil and associated gas taken from different producing wells in from the Yammama Reservoir were selected. Clear distinctions, in terms of gas isotopic signature and composition, between the wells located in northern and southern parts of the reservoir (i.e. lighter δ13C1, lower methane concentration, and negative sulfur isotope in the southern part) and light hydrocarbon ratios (e.g. nC7/toluene, 2,6-dmC7/1,1,3-tmcyC5 and m-xylene/4-mC8) in different oil samples indicated two separate compartments. Gradual variations in a number of petroleum bulk properties (API gravity, V/Ni ratios and asphaltene concentration) provided additional evidence on the reservoir-filling direction, signifying that a horizontal equilibrium between reservoir fluids across the Yammama Reservoir is yet to be achieved. Finally, differences in water-oil contacts and reservoir types further confirmed the compartmentalization of the reservoir into two separate compartments.

摘要:Sequences of wave-enhanced sediment-gravity flows (WESGFs) have been widely recognized in the marine shelf environment. In this study, we show observations of WESGF deposits in lacustrine settings using well core and thin section data from the Paleogene in the Jiyang sub-basin, Bohai Bay basin, eastern China. The findings of this study include the following: 1) the sequence of WESGFs in the lacustrine basin is similar to that of marine; it consists of three units, MF1 unit: siltstone with basal erosion surface, MF2 unit: silt-streaked claystone, and MF3 unit: silty-mudstone; and 2) prodelta sand sheets are found in the lacustrine WESGF sequence and are classified as the MFd unit: clay-streaked siltstone. However, because the system size and variability in hydrodynamic conditions are different between the lacustrine and marine basins, lacustrine WESGFs do appear to have three distinguishable features: 1) the sediment grain size and sand content are slightly higher than those of the marine WESGFs; 2) lacustrine WESGFs may contain prodelta sediments or sedimentary sequences of other types of gravity flows, such as hyperpycnal flows; and 3) the scale of the sedimentary structures for lacustrine WESGFs is smaller. The WESGFs found in the continental lacustrine basin provide a new model for sediment dispersal processes in lake environments and may be helpful to explain and predict the distribution of sandy reservoirs for oil and gas exploration.

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