This paper deals with the metallogenic model of the sandstone type uranium deposit in the northeastern Ordos Basin from aspects of uranium source, migration and deposition. A superposition metallogenic model has been ...This paper deals with the metallogenic model of the sandstone type uranium deposit in the northeastern Ordos Basin from aspects of uranium source, migration and deposition. A superposition metallogenic model has been established due to complex uranium mineralization processes with superposition of oil-gas reduction and thermal reformation.展开更多
[Objective]The research aimed to understand water conservation capacity of litter from different forest types in Caohai basin. [Method] Current storage amount,water holding capacity and precipitation interception abil...[Objective]The research aimed to understand water conservation capacity of litter from different forest types in Caohai basin. [Method] Current storage amount,water holding capacity and precipitation interception ability of litter from 4 types of forest were investigated and studied. [Result]The order of exist litter amount was grass slope ＆gt;shrub forest ＆gt;mixed broad leaf-conifer forest ＆gt;coniferous forest. The order of natural water holding capacity was mixed broad leafconifer forest ＆gt; coniferous forest ＆gt; grass slope ＆gt; shrub forest. The relevance between water holding capacity of litter and soaking time was in line with this formula： y = kln（ x） ＋ b. During 0-120 min of litter soaking,water holding capacity increased rapidly. After 120 min,the increasing trend remained flat until closing to the maximum water holding capacity. The relevance between water absorption rate of litter and soaking time was in line with this formula： y = a ＋ bx-1. In the beginning of soaking,water absorption rates of litter from different woodlands showed great difference. As soaking time went by,water absorption rates of litter from different woodlands all declined sharply. During 0-120 min,declining velocity of water absorption rate was quicker. After 120 min,the declining trend tended to be slow. The maximum water holding capacity of litter presented the order of shrub forest ＆gt; mixed broad leafconifer forest ＆gt; grass slope ＆gt; coniferous forest. The maximum precipitation interception amount of litter presented the order of shrub forest ＆gt; grass slope ＆gt; mixed broad leafconifer forest ＆gt; coniferous forest. Effective impounding capacity of litter presented the order of shrub forest ＆gt; mixed broad leafconifer forest ＆gt; grass slope ＆gt; coniferous forest. [Conclusion]The research could provide support for the construction of water conservation forest in Caohai basin.展开更多
Objective The Yubei area is located in the mid-east Maigaiti slope of southwestern Tarim Basin, China, with an exploration history of several years. Recent exploration has preliminarily indicated that the Ordovician ...Objective The Yubei area is located in the mid-east Maigaiti slope of southwestern Tarim Basin, China, with an exploration history of several years. Recent exploration has preliminarily indicated that the Ordovician carbonate formations in this area have some oil and gas potential. Carbonate microfacies provides material basis for reservoir development, seal formation and hydrocarbon generation. Therefore, this work utilized the standard microfacies （SMF） types to study the microfacies of the Ordovician formations in the Yubei area in order to provide theoretical basis for the next exploration.展开更多
This study analyzed the characteristics and types of the Lower Silurian shale gas reservoirs in and around Sichuan Basin through field observations, slices, Ar-ion-beam milling, scanning electron microscopy, and x-ray...This study analyzed the characteristics and types of the Lower Silurian shale gas reservoirs in and around Sichuan Basin through field observations, slices, Ar-ion-beam milling, scanning electron microscopy, and x-ray diffraction analysis of 25 black shale outcrops and samples. Two main types of shale gas reservoirs were determined, i.e., fractures and pores. Fractures were classified into five categories, i.e., giant, large, medium, small, and micro, according to the features of the shale gas reservoirs, effect of fracture on gas accumulation, and fracture nature. Pore types include organic matter pores, mineral pores（mineral surface, intraparticle, interparticle, and corrosional pore）, and nanofractures. The various fracture types, fracture scales, pore types, and pore sizes exert different controls over the gas storage and production capacity. Pores serve as a reservoir for gas storage and, the gas storage capacity can be determined using pores; fractures serve as pathways for gas migration, and gas production capacity can be determined using them.展开更多
The Paleogene and Neogene oil and gas in the western Qaidam basin have a regular distribution in three concentric zones from the edge to the center of the basin. Natural gas mainly occurs in the inner zone, and the ga...The Paleogene and Neogene oil and gas in the western Qaidam basin have a regular distribution in three concentric zones from the edge to the center of the basin. Natural gas mainly occurs in the inner zone, and the gas-oil ratio of the northern area of the basin is significantly higher than that of the southern area. Large amounts of carbon isotope data of natural gas, plotted in X- shaped and comprehensive identification diagrams for the southern area and northern area, respectively, were used to identify the types of natural gas. The large-scale distribution of natural gas is highly consistent with the Ro values of major source rocks, but is poorly correlated with the type of organic matter. This indicates that the main controlling factor of natural gas distribution is organic matter maturity, and the kerogen types act as the basis for the formation of different types of natural gas. Paleouplifts and squeezed anticlines near hydrocarbon generation depression centers, which are major natural gas-rich regions, control the migration directions of natural gas, while hydrocarbon migration pathways and fault systems connecting gas sources are the most important factors for natural gas reservoir formation in the inner basin. Therefore, favorable zones for natural gas distribution can be predicted on the basis of the distribution of thermal evolution and the gas generation intensity of major source rocks as well as the structural map. The Shizigou-Youshashan- Yingdong-Dawusi, Youquanzi -Kaitemilike - Youdunzi, and Xiaoliangshan - Nanyishan - Dafengshan structural belts are favorable zones for natural gas accumulation. This study has important theoretical and practical significance for future natural gas exploration.展开更多
The Junggar Basin in the northern part of Xinjiang is the second largest inland basin in China. It is located between the Altai and Tianshan Mountains, which is bounded by the Junggar bounded Mountain in the northwest...The Junggar Basin in the northern part of Xinjiang is the second largest inland basin in China. It is located between the Altai and Tianshan Mountains, which is bounded by the Junggar bounded Mountain in the northwest, the Altai Mountains in the northeast and the North Tianshan Mountains in the south. It belongs to a triangular close inland basin, and extends 700 km in EW and 370 km in NS, covering an area of 38x104 km2. The elevation is about 400 m, high in the east （about 1000 m） and low in the west. The central basin is the Guerbantonggute desert, which accounts for 36.9% of the total basin area.展开更多
A group of alluvial fans formed in the early Paleogene represent marginal sedimentary facies at the foot of the South Tianshan Mountain, Kuqa Depression, Tarim Basin, Xinjiang province. Two types of fans occurred in t...A group of alluvial fans formed in the early Paleogene represent marginal sedimentary facies at the foot of the South Tianshan Mountain, Kuqa Depression, Tarim Basin, Xinjiang province. Two types of fans occurred in the middle-late Paleogene Kumugeliemu and Suweiyi formations： one alluvial, and the other fan delta deposited in a lacustrine setting. Within the early Neogene Jidike Formation, coastal subaqueous fans developed, probably in a deeper water lacustrine setting. The three types of fans are stacked vertically in outcrop with the sequence in ascending order： bottom alluvial, middle fan-delta, and top suhaqueous. The subaqueous is a typical coarse-fan deposit occurring in the glutinite member of the Jidike Formation in some wells. Laterally, from the foreland to the lacustrine settings, the distribution pattern of sedimentary facies represents the same three fan types sequentially. The spatial distribution of these fans was controlled by the Paleogene-Neogene Basin transformation, and evolution with different types of fans developed in the Kuqa Depression in response. In the Paleogene, the Kuqa Depression was a rift basin where an alluvial fan was deposited in the foreland setting, which, by early Neogene, became a foreland basin when the lake level changed. With any rise in lake level, fan-deltas migrated from lacustrine to foreland settings, whereas when the lake level fell, fan migration was reversed. In the early Neogene, with increasing slope and rising lake level, fans progressed and covered the previous fan-delta and lacustrine mudstone. Eventually, subaqueous fans developed, forming the present spatial configuration of these three fan types.展开更多
The physical properties and group compositions of crude oils in the western depression of the Liaohe Basin possess such characteristics as to increase gradually in density, viscosity and wax contents, and decrease in ...The physical properties and group compositions of crude oils in the western depression of the Liaohe Basin possess such characteristics as to increase gradually in density, viscosity and wax contents, and decrease in saturated hydrocarbon and non-hydrocarbon and bitumen contents from the deep level to the shallow level and from the center of the depression to its boundary. Saturated hydrocarbons have various spectra, such as single peak and double peak patterns, front peak and rear peak patterns, and smooth peak and serated peak patterns, as well as the chromatograms of biodegraded n-alkanes. The ratios of Pr/Ph in crude oils from the southern part of the depression are generally higher than those in the northern part. The distribution of regular steranes C27-C29 is predominantly of the ramp type, and only a few samples have relatively high C28 contents in the southern part of the depression. As viewed from their physical properties and geochemical characteristics, crude oils in the study area can be divided into two types (I and II) based on oil-generating sources and sedimentary environments, and then further divided into three sub-types (Ia, Ib and Ic:IIa, IIb and IIIc, respectively) based on their degrees of maturation and secondary transformation. This will provide the reliable basis for oil-source correlation and petroleum exploration and prediction.展开更多
Objective The Huashan group（composed of the lower Hongshansi Formation and the upper Liufangzui Formation）is an important Neoproterozoic stratigraphic unit along the northern margin of the Yangtze Block.Previous doc...Objective The Huashan group（composed of the lower Hongshansi Formation and the upper Liufangzui Formation）is an important Neoproterozoic stratigraphic unit along the northern margin of the Yangtze Block.Previous documents have focused on the geochronological and geochemical aspects of the Neoproterozoic sedimentary basin in the Dahongshan region.However.展开更多
Crude oil samples taken from the southern part of western Qaidam Basin were analyzed with GC/MS in order to understand the geochemical characteristics of crude oils.The results reveal that most crude oils are characte...Crude oil samples taken from the southern part of western Qaidam Basin were analyzed with GC/MS in order to understand the geochemical characteristics of crude oils.The results reveal that most crude oils are characterized by high abundance of gammacerane and C35 homohopane,which are the representative characteristics of saline lacustrine crude oils.Based on the variation of the ratios of gammacerane/C30 hopane(G/H) and C35 homoho-pane/C34 homohopane(C35/C34H),two crude oil groups,A and B,are identified.Group-A crude oils mainly occurr in the north of the study area,with higher ratios of G/H(>0.8) and C35/C34H(>1.2),whereas group-B crude oils,selected from the south of the study area,show lower ratios of G/H(<0.8) and C35/C34H(<1.0).In addition,group-A crude oils are distinguished into three subgroups in accordance with their different ratios of G/H and C35/C34H and different distribution characteristics of n-alkanes,isoprenoids and steranes.These may be helpful for understanding the distribution characteristics of crude oils in the southern part of western Qaidam Basin and providing clues to the forthcoming exploration of crude oils and gas.展开更多
The diversity of sandstone diagenesis mechanisms caused by the complex geological conditions of oil/gas basins in China could hardly be reasonably explained by the traditional concept of burial diagenesis. Three genes...The diversity of sandstone diagenesis mechanisms caused by the complex geological conditions of oil/gas basins in China could hardly be reasonably explained by the traditional concept of burial diagenesis. Three genesis types of thermal diagenesis, tectonic diagenesis and fluid diagenesis are presented on the basis of the dynamic environment of the oil/gas basins and.the controlling factors and mechanisms of sandstone diagenesis. Thermal diagenesis of sandstone reservoirs is related not only to the effect of formation temperature on diagenesis, but also to the significant changes in diagenesis caused by geothermal gradients. The concept of thermal compaction is presented. Thermal compaction becomes weaker with increasing depth and becomes stronger at a higher geothermal gradient. At the same formation temperature, the sandstone porosity in the region with a lower geothermal gradient is e^0.077＋0.0042T times higher than that in the region with a higher geothermal gradient. Both sudden and gradual changes are observed in diagenetic evolution caused by structural deformation. Average sandstone compaction increased by 0.1051% for every 1.0MPa increase of lateral tectonic compressional stress, while late tectonic napping helped to preserve a higher porosity of underlying sandstone reservoir. Fluid diagenesis is a general phenomenon. The compaction caused by fluid properties is significant. The coarser the grain size, the stronger the fluid effect on compaction. The greater the burial depth, the weaker the fluid effect on compaction for the specific reservoir lithology and the greater the difference in the fluid effects on compaction between different grain sizes.展开更多
Generally, sandstone-type uranium deposits can be divided into three zones according to their redox conditions: oxidized zone, ore zone and reduced zone. The Dongsheng uranium deposit belongs to this type. In order to...Generally, sandstone-type uranium deposits can be divided into three zones according to their redox conditions: oxidized zone, ore zone and reduced zone. The Dongsheng uranium deposit belongs to this type. In order to study its geochemical characteristics, 11 samples were taken from the three zones of the Dongsheng uranium deposit. Five samples of them were collected from the oxidized zone, four samples from the ore zone and two samples from the reduced zone. These samples were analyzed using organic and inorganic geochemical methods. The results of GC traces and ICP-MASS indicate that the three zones show different organic and inorganic geochemical characteristics.展开更多
The surface of sequence boundary is a negative record. Its recognition largely depends on the physics of the sediments below and above the boundaries, or on the different sedimentary structures are synthetic marks for...The surface of sequence boundary is a negative record. Its recognition largely depends on the physics of the sediments below and above the boundaries, or on the different sedimentary structures are synthetic marks for the sedimentation and tectonic movements in the sedimentary basin. The Qiangtang Basin that is in 5000m above the sea level is located in Northern Tibet. The Lazhulung—Jinshajiang suture zone now bound it to the north and the Bangong—Nujiang suture zone to the south. Three second\|order tectonic units have been distinguished, i.e. North Qiangtang depression, Central rise and South Qiangtang depression from north to south.The Upper Permian Riejuichaka Formation is built up of mudstone and mud\|limestone, which is represented by sediments in seamarsh. The Lower Triassic Kuanglu Formation, which exhibits the structure unconformable contact with the overlying Upper Permian strata, is characterized by terrigenous clastic rocks in the lower area and is carbonate rocks in the upwarding area and the Middle Triassic Kuangnan Formation. The Upper Triassic Xiachaka Formation consisting of terrigenous clastic rocks, carbonates rocks and mixed sediments, is confined to the uplift zones. The lower Jurassic volcanic rocks are deposited in continental rift. The middle and Upper Jurassic Yangshiping Group are conformable contact and assembled by the gypsum\|bearing terrigenous clastic rock formations and carbonate rock formation. The Middle Cretaceous and the Paleocene strata is built up of the terrigenous clastic rock formations.展开更多
The molecular compositions and stable carbon and hydrogen isotopic compositions of natural gas from the Xinchang gas field in the Sichuan Basin were investigated to determine the genetic types. The natural gas is main...The molecular compositions and stable carbon and hydrogen isotopic compositions of natural gas from the Xinchang gas field in the Sichuan Basin were investigated to determine the genetic types. The natural gas is mainly composed of methane （88.99%-98.01%）, and the dryness coefficient varies between 0.908 and 0.997. The gas generally displays positive alkane carbon and hydrogen isotopic series. The geochemical characteristics and gas-source correlation indicate that the gases stored in the 5th member of the Upper Triassic Xujiahe Formation are coal-type gases which are derived from source rocks in the stratum itself. The gases reservoired in the 4th member of the Xujiahe Formation and Jurassic strata in the Xinchang gas field are also coal-type gases that are derived from source rocks in the 3rd and 4th members of the Xujiahe Formation. The gases reservoired in the 2nd member of the Upper Triassic Xujiahe Formation are mainly coal-type gases with small amounts of oil-type gas that is derived from source rocks in the stratum itself. This is accompanied by a small amount of contribution brought by source rocks in the Upper Triassic Ma＇antang and Xiaotangzi formations. The gases reservoired in the 4th member of the Middle Triassic Leikoupo Formation are oil-type gases and are believed to be derived from the secondary cracking of oil which is most likely to be generated from the Upper Permian source rocks.展开更多
The major elements, trace elements and REEs were analyzed on the samples collected from the sandstone-type uranium deposits in the Ordos Basin to constrain the mechanism of uranium enrichment. The total REE amount ran...The major elements, trace elements and REEs were analyzed on the samples collected from the sandstone-type uranium deposits in the Ordos Basin to constrain the mechanism of uranium enrichment. The total REE amount ranges from 36.7 to 701.8 μg/g and the REE distribution patterns of the sandstone-type uranium samples are characterized by LREE enrichment and high REE depletion. The results also indicated a high Y abundance and Eu anomalies between 0.77-1.81. High-precision ICP-MS results showed that U abundances are within the range of 0.73-150 μg/g, showing some strong correlation between U enrichment and related elements such as Ti, V, Zr, Mo, and Au. In addition, Th abundance is correlated with ΣREE.展开更多
Late Paleozoic to Early Mesozoic granites are widespread in the southern Qaidam Basin, northern margin of the eastern Kunlun orogenic belt. Their petrogenesis can provide us insights into the tectonic evolution and cr...Late Paleozoic to Early Mesozoic granites are widespread in the southern Qaidam Basin, northern margin of the eastern Kunlun orogenic belt. Their petrogenesis can provide us insights into the tectonic evolution and crustal growth process in the Qaidam Basin. This paper reports Permian–Triassic granites from the Kunbei area, southwestern Qaidam Basin. Detailed zircon LA-ICP MS U-Pb dating reveals that the granites from the four drilling cores（q404, q406, q1612-8, q1613-8） have identical ages of 251±3, 256±4, 247±2, and 251±6 Ma, respectively, these ages are identical with the Permian–Triassic granites from the eastern Qaidam Basin. Detailed geochemical analyses indicate that these granites display typical affinities of highly-fractionated I-type granites：（1） they have high SiO_2（up to 76.5 wt.%）, Na_2O＋K_2O（7.91 wt.% to 9.48 wt.%） contents and high FeO^T/MgO values of 4.7 to 9.3, suggesting significant fractional crystallization;（2） their low A/CNK values of 0.54 to 1.03, no normative Al-rich minerals, inconsistent with the per-aluminous S-type granites;（3） their low Ga（14.5 ppm to 20.7 ppm） and 10 000×Ga/Al（2.23 to 3.03, most of them 〈2.6） values are inconsistent with the A-type granites;（4） the high Rb（191 ppm to 406 ppm） contents and Rb/Sr（2.1 to 13.4） ratios, as well as the significant negative Eu anomalies（0.10 to 0.42） also indicate significant fractional crystallization of feldspars;（5） their low P_2O_5 contents（0.02 wt.% to 0.10 wt.%） suggest the limited solubility of phosphorus in primitive metaluminous melts. In combination with the geological background, we propose that the Permian–Triassic highly-fractionated I-type granites resulted from partial melting of intra-crustal mafic rocks, and the primitive I-type granitic melts underwent significant fractional crystallization of feldspars. The occurrence of highly-fractionated I-type granites in the southwestern Qaidam Basin suggests a Permian–Triassic active continental margin in the northern margin of the East Kunlun orogenic belt.展开更多
The uplift is a positive structural unit of the crust. It is an important window for continental dynamics owing to its abundant structural phenomena, such as fault, fold, unconformity and denudation of strata. Meanwhi...The uplift is a positive structural unit of the crust. It is an important window for continental dynamics owing to its abundant structural phenomena, such as fault, fold, unconformity and denudation of strata. Meanwhile, it is the very place to store important minerals like oil, natural gas, coal and uranium. Giant and large-scale oil and gas fields in China, such as the Daqing Oilfield, Lunnan-Tahe Oilfield, Penglai 19-3 Oilfield, Puguang Gas Field and Jingbian Gas Field, are developed mainly on uplifts. Therefore, it is the main target both for oil and gas exploration and for geological study. The uplift can be either a basement uplift, or one developed only in the sedimentary cover. Extension, compression and wrench or their combined forces may give rise to uplifts. The development process of uplifting, such as formation, development, dwindling and destruction, can be taken as the uplifting cycle. The uplifts on the giant Precambrian cratons are large in scale with less extensive structural deformation. The uplifts on the medium- and small-sized cratons or neo-cratons are formed in various shapes with strong structural deformation and complicated geological structure. Owing to changes in the geodynamic environment, uplift experiences a multi-stage or multi-cycle development process. Its geological structure is characterized in superposition of multi-structural layers. Based on the basement properties, mechanical stratigraphy and development sequence, uplifts can be divided into three basic types-the succession, superposition and destruction ones. The succession type is subdivided into the maintaining type and the lasting type. The superposition type can be subdivided into the composite anticlinal type, the buried-hill draped type, the faulted uplift type and the migration type according to the different scales and superimposed styles of uplifts in different cycles. The destruction type is subdivided into the tilting type and the negative inverted type. The development history of uplifts and their controlling effects on sedimentation and fluids are quite different from one another, although the uplifts with different structural types store important minerals. Uplifts and their slopes are the main areas for oil and gas accumulation. They usually become the composite oil and gas accumulation zones （belts） with multiple productive formations and various types of oil and gas reservoirs.展开更多
In this contribution we use VMS mineral systems in the Bryah rift-basin to constrain the tectonic setting of the widespread mafic and ultramafic magmatism that characterises the rift-basin in question.Two distinct,but...In this contribution we use VMS mineral systems in the Bryah rift-basin to constrain the tectonic setting of the widespread mafic and ultramafic magmatism that characterises the rift-basin in question.Two distinct,but temporally closely associated,lithostratigraphic sequences,Narracoota and Karalundi Formations,are discussed.The Karalundi Formation is the main host of VMS mineral systems in the region.The Karalundi Formation consists of turbiditic and immature clastic sediments,which are locally intercalated with basaltic hyaloclastites,dolerites and banded jaspilites.We propose that the basaltic hyaloclastites,dolerites and elastics and jaspilites rocks,form a distinct unit of the Karalundi Formation,named Noonyereena Member.The VMS mineral systems occur near the north-east trendingJenkin Fault and comprise the giant and world-class DeCrussa and the Red Bore deposits.The nature of these deposits and their intimate association with terrigenous clastic rocks and dominantly marine mafic volcanic and subvolcanic rocks,as well as the common development of peperitic margins,are considered indicative of a Besshi-type environment,similar to that of present-day Gulf of California.Our Re-Os age data from a primary pyrite yielded a mean model age of 2012 ± 48 Ma,which coincides（within error） with recent published Re-Os data（Hawke et al.,2015） and confirms the timing of the proposed geodynamic evolution.We propose a geodynamic model that attempts to explain the presence of the Narracoota and Karalundi Formations as the result of mantle plume activity,which began with early uplift of continental crust with intraplate volcanism,followed by early stages of rifting with the deposition of the Karalundi Formation（and Noonyereena Member）,which led to the formation of Besshi-type VMS deposits.With on-going mantle plume activity and early stages of continental separation,an oceanic plateau was formed and is now represented by mafic-ultramafic rocks of the Narracoota Formation.展开更多
Early Cretaceous A-type rhyolites of the Shangkuli Formation in the Hailar Basin of NE China exhibit geochemical characteristics of high silicon,alkali,Fe/Mg,Ga/Al,Zr,Pb,HFSEs,and REE contents but low Ca,Ba,Sr and Eu,...Early Cretaceous A-type rhyolites of the Shangkuli Formation in the Hailar Basin of NE China exhibit geochemical characteristics of high silicon,alkali,Fe/Mg,Ga/Al,Zr,Pb,HFSEs,and REE contents but low Ca,Ba,Sr and Eu,which meet the criteria of typical reduced A-type granite.The A-type rhyolites are most probably derived from magmatic underplating and partial melting of quartz-feldspathic lower crust,with the lithospheric mantle material involved,due to the extensional deformation of the Erguna-Hulun Fault.Although the A-type rhyolites show A1-type trace elements characteristics,they were formed in a post-orogenic extensional background together with the coeval widespread bimodal volcanic rocks,metamorphic core complexes,volcanic fault basins and metallogenic province in the Sino-Russia-Mongolia border tract.This extension event was related to the collapse of thickened region of the continental crust after the closure of the Mongol-Okhotsk Ocean.展开更多
文摘This paper deals with the metallogenic model of the sandstone type uranium deposit in the northeastern Ordos Basin from aspects of uranium source, migration and deposition. A superposition metallogenic model has been established due to complex uranium mineralization processes with superposition of oil-gas reduction and thermal reformation.
基金Supported by National "Twelfth Five-year"Science and Technology Support Plan,China(2011BAC02B02)Graduate Innovation Fund of Guizhou University,China
文摘[Objective]The research aimed to understand water conservation capacity of litter from different forest types in Caohai basin. [Method] Current storage amount,water holding capacity and precipitation interception ability of litter from 4 types of forest were investigated and studied. [Result]The order of exist litter amount was grass slope ＆gt;shrub forest ＆gt;mixed broad leaf-conifer forest ＆gt;coniferous forest. The order of natural water holding capacity was mixed broad leafconifer forest ＆gt; coniferous forest ＆gt; grass slope ＆gt; shrub forest. The relevance between water holding capacity of litter and soaking time was in line with this formula： y = kln（ x） ＋ b. During 0-120 min of litter soaking,water holding capacity increased rapidly. After 120 min,the increasing trend remained flat until closing to the maximum water holding capacity. The relevance between water absorption rate of litter and soaking time was in line with this formula： y = a ＋ bx-1. In the beginning of soaking,water absorption rates of litter from different woodlands showed great difference. As soaking time went by,water absorption rates of litter from different woodlands all declined sharply. During 0-120 min,declining velocity of water absorption rate was quicker. After 120 min,the declining trend tended to be slow. The maximum water holding capacity of litter presented the order of shrub forest ＆gt; mixed broad leafconifer forest ＆gt; grass slope ＆gt; coniferous forest. The maximum precipitation interception amount of litter presented the order of shrub forest ＆gt; grass slope ＆gt; mixed broad leafconifer forest ＆gt; coniferous forest. Effective impounding capacity of litter presented the order of shrub forest ＆gt; mixed broad leafconifer forest ＆gt; grass slope ＆gt; coniferous forest. [Conclusion]The research could provide support for the construction of water conservation forest in Caohai basin.
基金funded by the National Natural Science Foundation of China(grant No.41572117)Technological&Developmental Department of China Petroleum&Chemical Corporation(grants No.P13040 and P14128)China Geological Survey(grant No.DD20160175-1-1)
文摘Objective The Yubei area is located in the mid-east Maigaiti slope of southwestern Tarim Basin, China, with an exploration history of several years. Recent exploration has preliminarily indicated that the Ordovician carbonate formations in this area have some oil and gas potential. Carbonate microfacies provides material basis for reservoir development, seal formation and hydrocarbon generation. Therefore, this work utilized the standard microfacies （SMF） types to study the microfacies of the Ordovician formations in the Yubei area in order to provide theoretical basis for the next exploration.
基金supported by the National Natural Science Foundation of China(Grant No.41202103)
文摘This study analyzed the characteristics and types of the Lower Silurian shale gas reservoirs in and around Sichuan Basin through field observations, slices, Ar-ion-beam milling, scanning electron microscopy, and x-ray diffraction analysis of 25 black shale outcrops and samples. Two main types of shale gas reservoirs were determined, i.e., fractures and pores. Fractures were classified into five categories, i.e., giant, large, medium, small, and micro, according to the features of the shale gas reservoirs, effect of fracture on gas accumulation, and fracture nature. Pore types include organic matter pores, mineral pores（mineral surface, intraparticle, interparticle, and corrosional pore）, and nanofractures. The various fracture types, fracture scales, pore types, and pore sizes exert different controls over the gas storage and production capacity. Pores serve as a reservoir for gas storage and, the gas storage capacity can be determined using pores; fractures serve as pathways for gas migration, and gas production capacity can be determined using them.
基金supported financially by the National Science and Technology Major Project"Chinese large gasfields’formation conditions,accumulation and objective evaluation"(2011ZX05007)the Major Special Project of Chinese Petroleum Development Technologies"A study on comprehensive supporting technologies for building oil-gas field of ten million tons in Qaidam basin"(2011E-03)
文摘The Paleogene and Neogene oil and gas in the western Qaidam basin have a regular distribution in three concentric zones from the edge to the center of the basin. Natural gas mainly occurs in the inner zone, and the gas-oil ratio of the northern area of the basin is significantly higher than that of the southern area. Large amounts of carbon isotope data of natural gas, plotted in X- shaped and comprehensive identification diagrams for the southern area and northern area, respectively, were used to identify the types of natural gas. The large-scale distribution of natural gas is highly consistent with the Ro values of major source rocks, but is poorly correlated with the type of organic matter. This indicates that the main controlling factor of natural gas distribution is organic matter maturity, and the kerogen types act as the basis for the formation of different types of natural gas. Paleouplifts and squeezed anticlines near hydrocarbon generation depression centers, which are major natural gas-rich regions, control the migration directions of natural gas, while hydrocarbon migration pathways and fault systems connecting gas sources are the most important factors for natural gas reservoir formation in the inner basin. Therefore, favorable zones for natural gas distribution can be predicted on the basis of the distribution of thermal evolution and the gas generation intensity of major source rocks as well as the structural map. The Shizigou-Youshashan- Yingdong-Dawusi, Youquanzi -Kaitemilike - Youdunzi, and Xiaoliangshan - Nanyishan - Dafengshan structural belts are favorable zones for natural gas accumulation. This study has important theoretical and practical significance for future natural gas exploration.
文摘The Junggar Basin in the northern part of Xinjiang is the second largest inland basin in China. It is located between the Altai and Tianshan Mountains, which is bounded by the Junggar bounded Mountain in the northwest, the Altai Mountains in the northeast and the North Tianshan Mountains in the south. It belongs to a triangular close inland basin, and extends 700 km in EW and 370 km in NS, covering an area of 38x104 km2. The elevation is about 400 m, high in the east （about 1000 m） and low in the west. The central basin is the Guerbantonggute desert, which accounts for 36.9% of the total basin area.
基金supported by the National scientific special:Tectonic and sedimentary and reservoir features of foreland basin in west-central China(2008zx05000-003-01).
文摘A group of alluvial fans formed in the early Paleogene represent marginal sedimentary facies at the foot of the South Tianshan Mountain, Kuqa Depression, Tarim Basin, Xinjiang province. Two types of fans occurred in the middle-late Paleogene Kumugeliemu and Suweiyi formations： one alluvial, and the other fan delta deposited in a lacustrine setting. Within the early Neogene Jidike Formation, coastal subaqueous fans developed, probably in a deeper water lacustrine setting. The three types of fans are stacked vertically in outcrop with the sequence in ascending order： bottom alluvial, middle fan-delta, and top suhaqueous. The subaqueous is a typical coarse-fan deposit occurring in the glutinite member of the Jidike Formation in some wells. Laterally, from the foreland to the lacustrine settings, the distribution pattern of sedimentary facies represents the same three fan types sequentially. The spatial distribution of these fans was controlled by the Paleogene-Neogene Basin transformation, and evolution with different types of fans developed in the Kuqa Depression in response. In the Paleogene, the Kuqa Depression was a rift basin where an alluvial fan was deposited in the foreland setting, which, by early Neogene, became a foreland basin when the lake level changed. With any rise in lake level, fan-deltas migrated from lacustrine to foreland settings, whereas when the lake level fell, fan migration was reversed. In the early Neogene, with increasing slope and rising lake level, fans progressed and covered the previous fan-delta and lacustrine mudstone. Eventually, subaqueous fans developed, forming the present spatial configuration of these three fan types.
文摘The physical properties and group compositions of crude oils in the western depression of the Liaohe Basin possess such characteristics as to increase gradually in density, viscosity and wax contents, and decrease in saturated hydrocarbon and non-hydrocarbon and bitumen contents from the deep level to the shallow level and from the center of the depression to its boundary. Saturated hydrocarbons have various spectra, such as single peak and double peak patterns, front peak and rear peak patterns, and smooth peak and serated peak patterns, as well as the chromatograms of biodegraded n-alkanes. The ratios of Pr/Ph in crude oils from the southern part of the depression are generally higher than those in the northern part. The distribution of regular steranes C27-C29 is predominantly of the ramp type, and only a few samples have relatively high C28 contents in the southern part of the depression. As viewed from their physical properties and geochemical characteristics, crude oils in the study area can be divided into two types (I and II) based on oil-generating sources and sedimentary environments, and then further divided into three sub-types (Ia, Ib and Ic:IIa, IIb and IIIc, respectively) based on their degrees of maturation and secondary transformation. This will provide the reliable basis for oil-source correlation and petroleum exploration and prediction.
基金financially supported by the National Natural Science Foundation of China(grant No. 41402103,41502114 and 41372124)
文摘Objective The Huashan group（composed of the lower Hongshansi Formation and the upper Liufangzui Formation）is an important Neoproterozoic stratigraphic unit along the northern margin of the Yangtze Block.Previous documents have focused on the geochronological and geochemical aspects of the Neoproterozoic sedimentary basin in the Dahongshan region.However.
文摘Crude oil samples taken from the southern part of western Qaidam Basin were analyzed with GC/MS in order to understand the geochemical characteristics of crude oils.The results reveal that most crude oils are characterized by high abundance of gammacerane and C35 homohopane,which are the representative characteristics of saline lacustrine crude oils.Based on the variation of the ratios of gammacerane/C30 hopane(G/H) and C35 homoho-pane/C34 homohopane(C35/C34H),two crude oil groups,A and B,are identified.Group-A crude oils mainly occurr in the north of the study area,with higher ratios of G/H(>0.8) and C35/C34H(>1.2),whereas group-B crude oils,selected from the south of the study area,show lower ratios of G/H(<0.8) and C35/C34H(<1.0).In addition,group-A crude oils are distinguished into three subgroups in accordance with their different ratios of G/H and C35/C34H and different distribution characteristics of n-alkanes,isoprenoids and steranes.These may be helpful for understanding the distribution characteristics of crude oils in the southern part of western Qaidam Basin and providing clues to the forthcoming exploration of crude oils and gas.
文摘The diversity of sandstone diagenesis mechanisms caused by the complex geological conditions of oil/gas basins in China could hardly be reasonably explained by the traditional concept of burial diagenesis. Three genesis types of thermal diagenesis, tectonic diagenesis and fluid diagenesis are presented on the basis of the dynamic environment of the oil/gas basins and.the controlling factors and mechanisms of sandstone diagenesis. Thermal diagenesis of sandstone reservoirs is related not only to the effect of formation temperature on diagenesis, but also to the significant changes in diagenesis caused by geothermal gradients. The concept of thermal compaction is presented. Thermal compaction becomes weaker with increasing depth and becomes stronger at a higher geothermal gradient. At the same formation temperature, the sandstone porosity in the region with a lower geothermal gradient is e^0.077＋0.0042T times higher than that in the region with a higher geothermal gradient. Both sudden and gradual changes are observed in diagenetic evolution caused by structural deformation. Average sandstone compaction increased by 0.1051% for every 1.0MPa increase of lateral tectonic compressional stress, while late tectonic napping helped to preserve a higher porosity of underlying sandstone reservoir. Fluid diagenesis is a general phenomenon. The compaction caused by fluid properties is significant. The coarser the grain size, the stronger the fluid effect on compaction. The greater the burial depth, the weaker the fluid effect on compaction for the specific reservoir lithology and the greater the difference in the fluid effects on compaction between different grain sizes.
文摘Generally, sandstone-type uranium deposits can be divided into three zones according to their redox conditions: oxidized zone, ore zone and reduced zone. The Dongsheng uranium deposit belongs to this type. In order to study its geochemical characteristics, 11 samples were taken from the three zones of the Dongsheng uranium deposit. Five samples of them were collected from the oxidized zone, four samples from the ore zone and two samples from the reduced zone. These samples were analyzed using organic and inorganic geochemical methods. The results of GC traces and ICP-MASS indicate that the three zones show different organic and inorganic geochemical characteristics.
文摘The surface of sequence boundary is a negative record. Its recognition largely depends on the physics of the sediments below and above the boundaries, or on the different sedimentary structures are synthetic marks for the sedimentation and tectonic movements in the sedimentary basin. The Qiangtang Basin that is in 5000m above the sea level is located in Northern Tibet. The Lazhulung—Jinshajiang suture zone now bound it to the north and the Bangong—Nujiang suture zone to the south. Three second\|order tectonic units have been distinguished, i.e. North Qiangtang depression, Central rise and South Qiangtang depression from north to south.The Upper Permian Riejuichaka Formation is built up of mudstone and mud\|limestone, which is represented by sediments in seamarsh. The Lower Triassic Kuanglu Formation, which exhibits the structure unconformable contact with the overlying Upper Permian strata, is characterized by terrigenous clastic rocks in the lower area and is carbonate rocks in the upwarding area and the Middle Triassic Kuangnan Formation. The Upper Triassic Xiachaka Formation consisting of terrigenous clastic rocks, carbonates rocks and mixed sediments, is confined to the uplift zones. The lower Jurassic volcanic rocks are deposited in continental rift. The middle and Upper Jurassic Yangshiping Group are conformable contact and assembled by the gypsum\|bearing terrigenous clastic rock formations and carbonate rock formation. The Middle Cretaceous and the Paleocene strata is built up of the terrigenous clastic rock formations.
基金financially supported by the National Natural Science Foundation of China (grants No.41625009, 41302118 and U1663201)the National Key Foundational Research and Development Project (Grant No:2016YFB0600804)the National Science & Technology Special Project (grant No.2016ZX05002-006)
文摘The molecular compositions and stable carbon and hydrogen isotopic compositions of natural gas from the Xinchang gas field in the Sichuan Basin were investigated to determine the genetic types. The natural gas is mainly composed of methane （88.99%-98.01%）, and the dryness coefficient varies between 0.908 and 0.997. The gas generally displays positive alkane carbon and hydrogen isotopic series. The geochemical characteristics and gas-source correlation indicate that the gases stored in the 5th member of the Upper Triassic Xujiahe Formation are coal-type gases which are derived from source rocks in the stratum itself. The gases reservoired in the 4th member of the Xujiahe Formation and Jurassic strata in the Xinchang gas field are also coal-type gases that are derived from source rocks in the 3rd and 4th members of the Xujiahe Formation. The gases reservoired in the 2nd member of the Upper Triassic Xujiahe Formation are mainly coal-type gases with small amounts of oil-type gas that is derived from source rocks in the stratum itself. This is accompanied by a small amount of contribution brought by source rocks in the Upper Triassic Ma＇antang and Xiaotangzi formations. The gases reservoired in the 4th member of the Middle Triassic Leikoupo Formation are oil-type gases and are believed to be derived from the secondary cracking of oil which is most likely to be generated from the Upper Permian source rocks.
基金This study is supported by the Chinese 973 National Key Research and Development Program (2003CB214606) on Accumulation and Formation of Multi-Energy Mineral Deposits Coexisting in the same Basin and Open Foundation of the State Laboratory of Geological Processes and Mineral Resources.
文摘The major elements, trace elements and REEs were analyzed on the samples collected from the sandstone-type uranium deposits in the Ordos Basin to constrain the mechanism of uranium enrichment. The total REE amount ranges from 36.7 to 701.8 μg/g and the REE distribution patterns of the sandstone-type uranium samples are characterized by LREE enrichment and high REE depletion. The results also indicated a high Y abundance and Eu anomalies between 0.77-1.81. High-precision ICP-MS results showed that U abundances are within the range of 0.73-150 μg/g, showing some strong correlation between U enrichment and related elements such as Ti, V, Zr, Mo, and Au. In addition, Th abundance is correlated with ΣREE.
基金Financial support for this study was jointly provided by the National Natural Science Foundation of China (No.41102037)the foundation for the author of National Excellent Doctoral Dissertation of China (No.201324)+1 种基金the Foundation of Young Excellent Scientists of the Shaanxi Province (No.2014KJXX-60)the MOST Special Fund from the State Key Laboratory of Continental Dynamics
文摘Late Paleozoic to Early Mesozoic granites are widespread in the southern Qaidam Basin, northern margin of the eastern Kunlun orogenic belt. Their petrogenesis can provide us insights into the tectonic evolution and crustal growth process in the Qaidam Basin. This paper reports Permian–Triassic granites from the Kunbei area, southwestern Qaidam Basin. Detailed zircon LA-ICP MS U-Pb dating reveals that the granites from the four drilling cores（q404, q406, q1612-8, q1613-8） have identical ages of 251±3, 256±4, 247±2, and 251±6 Ma, respectively, these ages are identical with the Permian–Triassic granites from the eastern Qaidam Basin. Detailed geochemical analyses indicate that these granites display typical affinities of highly-fractionated I-type granites：（1） they have high SiO_2（up to 76.5 wt.%）, Na_2O＋K_2O（7.91 wt.% to 9.48 wt.%） contents and high FeO^T/MgO values of 4.7 to 9.3, suggesting significant fractional crystallization;（2） their low A/CNK values of 0.54 to 1.03, no normative Al-rich minerals, inconsistent with the per-aluminous S-type granites;（3） their low Ga（14.5 ppm to 20.7 ppm） and 10 000×Ga/Al（2.23 to 3.03, most of them 〈2.6） values are inconsistent with the A-type granites;（4） the high Rb（191 ppm to 406 ppm） contents and Rb/Sr（2.1 to 13.4） ratios, as well as the significant negative Eu anomalies（0.10 to 0.42） also indicate significant fractional crystallization of feldspars;（5） their low P_2O_5 contents（0.02 wt.% to 0.10 wt.%） suggest the limited solubility of phosphorus in primitive metaluminous melts. In combination with the geological background, we propose that the Permian–Triassic highly-fractionated I-type granites resulted from partial melting of intra-crustal mafic rocks, and the primitive I-type granitic melts underwent significant fractional crystallization of feldspars. The occurrence of highly-fractionated I-type granites in the southwestern Qaidam Basin suggests a Permian–Triassic active continental margin in the northern margin of the East Kunlun orogenic belt.
基金co-supported by the National Key Basic Research and Development Program of China(No.2006CB202300)the National Natural Science Foundation Important Project(No.40739906).
文摘The uplift is a positive structural unit of the crust. It is an important window for continental dynamics owing to its abundant structural phenomena, such as fault, fold, unconformity and denudation of strata. Meanwhile, it is the very place to store important minerals like oil, natural gas, coal and uranium. Giant and large-scale oil and gas fields in China, such as the Daqing Oilfield, Lunnan-Tahe Oilfield, Penglai 19-3 Oilfield, Puguang Gas Field and Jingbian Gas Field, are developed mainly on uplifts. Therefore, it is the main target both for oil and gas exploration and for geological study. The uplift can be either a basement uplift, or one developed only in the sedimentary cover. Extension, compression and wrench or their combined forces may give rise to uplifts. The development process of uplifting, such as formation, development, dwindling and destruction, can be taken as the uplifting cycle. The uplifts on the giant Precambrian cratons are large in scale with less extensive structural deformation. The uplifts on the medium- and small-sized cratons or neo-cratons are formed in various shapes with strong structural deformation and complicated geological structure. Owing to changes in the geodynamic environment, uplift experiences a multi-stage or multi-cycle development process. Its geological structure is characterized in superposition of multi-structural layers. Based on the basement properties, mechanical stratigraphy and development sequence, uplifts can be divided into three basic types-the succession, superposition and destruction ones. The succession type is subdivided into the maintaining type and the lasting type. The superposition type can be subdivided into the composite anticlinal type, the buried-hill draped type, the faulted uplift type and the migration type according to the different scales and superimposed styles of uplifts in different cycles. The destruction type is subdivided into the tilting type and the negative inverted type. The development history of uplifts and their controlling effects on sedimentation and fluids are quite different from one another, although the uplifts with different structural types store important minerals. Uplifts and their slopes are the main areas for oil and gas accumulation. They usually become the composite oil and gas accumulation zones （belts） with multiple productive formations and various types of oil and gas reservoirs.
文摘In this contribution we use VMS mineral systems in the Bryah rift-basin to constrain the tectonic setting of the widespread mafic and ultramafic magmatism that characterises the rift-basin in question.Two distinct,but temporally closely associated,lithostratigraphic sequences,Narracoota and Karalundi Formations,are discussed.The Karalundi Formation is the main host of VMS mineral systems in the region.The Karalundi Formation consists of turbiditic and immature clastic sediments,which are locally intercalated with basaltic hyaloclastites,dolerites and banded jaspilites.We propose that the basaltic hyaloclastites,dolerites and elastics and jaspilites rocks,form a distinct unit of the Karalundi Formation,named Noonyereena Member.The VMS mineral systems occur near the north-east trendingJenkin Fault and comprise the giant and world-class DeCrussa and the Red Bore deposits.The nature of these deposits and their intimate association with terrigenous clastic rocks and dominantly marine mafic volcanic and subvolcanic rocks,as well as the common development of peperitic margins,are considered indicative of a Besshi-type environment,similar to that of present-day Gulf of California.Our Re-Os age data from a primary pyrite yielded a mean model age of 2012 ± 48 Ma,which coincides（within error） with recent published Re-Os data（Hawke et al.,2015） and confirms the timing of the proposed geodynamic evolution.We propose a geodynamic model that attempts to explain the presence of the Narracoota and Karalundi Formations as the result of mantle plume activity,which began with early uplift of continental crust with intraplate volcanism,followed by early stages of rifting with the deposition of the Karalundi Formation（and Noonyereena Member）,which led to the formation of Besshi-type VMS deposits.With on-going mantle plume activity and early stages of continental separation,an oceanic plateau was formed and is now represented by mafic-ultramafic rocks of the Narracoota Formation.
基金Supported by National Basic Research Program of China(No.2009CB219305)
文摘Early Cretaceous A-type rhyolites of the Shangkuli Formation in the Hailar Basin of NE China exhibit geochemical characteristics of high silicon,alkali,Fe/Mg,Ga/Al,Zr,Pb,HFSEs,and REE contents but low Ca,Ba,Sr and Eu,which meet the criteria of typical reduced A-type granite.The A-type rhyolites are most probably derived from magmatic underplating and partial melting of quartz-feldspathic lower crust,with the lithospheric mantle material involved,due to the extensional deformation of the Erguna-Hulun Fault.Although the A-type rhyolites show A1-type trace elements characteristics,they were formed in a post-orogenic extensional background together with the coeval widespread bimodal volcanic rocks,metamorphic core complexes,volcanic fault basins and metallogenic province in the Sino-Russia-Mongolia border tract.This extension event was related to the collapse of thickened region of the continental crust after the closure of the Mongol-Okhotsk Ocean.
