2016 Vol. 41, No. 9
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2016, 41(9): 1435-1450.
doi: 10.3799/dqkx.2016.502
Abstract:
As an important component to reveal the metallogenic regularity in the Zhejiang-Anhui-Jiangxi border region, the Datongkeng porphyry W-Mo deposit in Chun'an County is located in the southeastern margin of the Yangtze block, and the W-Mo ore bodies are mainly located in the internal or external contact zones between granite and sandstone of Xiuning Formation. The Datongkeng granite is characterized by quasi-aluminous, showing the nature of Ⅰ-type granite and high-K calc-alkalic series rock. The granite is rich in Rb, K, Th, U, and relatively depleted in Sr, Ba, Nb, Ta, Ti. The total REE contents are relatively low (ΣREE=106.2×10-6-211.5×10-6), and the rocks show obvious LREE and HREE fractionation (ΣLREE/ΣHREE=6.4-12.2), moderately negative Eu anomalies (δEu=0.50-0.63), suggesting that these rocks have the characters of typical volcanic arc rocks. The SHRIMP U-Pb zircon age of 148.3±1.9 Ma for granite is close to the Re-Os isochron age of 146.47±0.81 Ma for five molybdenite samples from the Datongkeng W-Mo deposit, indicating magmatism and mineralization are a continuous process, which took place in the compression tectonic environment related to the subduction of pacific plate at Late Jurassic, and corresponds to the second large-scale W-Mo mineralization in South China.
As an important component to reveal the metallogenic regularity in the Zhejiang-Anhui-Jiangxi border region, the Datongkeng porphyry W-Mo deposit in Chun'an County is located in the southeastern margin of the Yangtze block, and the W-Mo ore bodies are mainly located in the internal or external contact zones between granite and sandstone of Xiuning Formation. The Datongkeng granite is characterized by quasi-aluminous, showing the nature of Ⅰ-type granite and high-K calc-alkalic series rock. The granite is rich in Rb, K, Th, U, and relatively depleted in Sr, Ba, Nb, Ta, Ti. The total REE contents are relatively low (ΣREE=106.2×10-6-211.5×10-6), and the rocks show obvious LREE and HREE fractionation (ΣLREE/ΣHREE=6.4-12.2), moderately negative Eu anomalies (δEu=0.50-0.63), suggesting that these rocks have the characters of typical volcanic arc rocks. The SHRIMP U-Pb zircon age of 148.3±1.9 Ma for granite is close to the Re-Os isochron age of 146.47±0.81 Ma for five molybdenite samples from the Datongkeng W-Mo deposit, indicating magmatism and mineralization are a continuous process, which took place in the compression tectonic environment related to the subduction of pacific plate at Late Jurassic, and corresponds to the second large-scale W-Mo mineralization in South China.
2016, 41(9): 1451-1460.
doi: 10.3799/dqkx.2016.114
Abstract:
Experimental studies of the sound velocity of minerals of the mantle are crucial for understanding the compositions and properties of the Earth's deep interiors. The ultrasonic technique has been globally used in the multianvil press for velocity measurements of various mantle minerals at relevant P-T conditions of the mantle transition zone. However, the ultrasonic velocity measurements in multianvil in China have been limited to < 6 GPa conditions in the past. Recently, we developed a new ultrasonic velocity measurement system in a 1 000 t Walker type multianvil press installed in China University of Geosciences (Wuhan) and measured the velocities of an Mg2SiO4 wadsleyite polycrystalline sample up to 18 GPa. The results are comparable with those of previous ultrasonic studies. For the first time in China, the sound velocity measurement was taken at high pressure conditions of the mantle transition zone in a multianvil with ultrasonic techniques, bridging the gap between the domestic and the international advanced level. The technique would provide not only experimental constraints on the interpretation of the geophysical observation beneath China and surrounding regions, but also experimental supports for the studies on the elastic properties of minerals/rocks and condensed materials in China.
Experimental studies of the sound velocity of minerals of the mantle are crucial for understanding the compositions and properties of the Earth's deep interiors. The ultrasonic technique has been globally used in the multianvil press for velocity measurements of various mantle minerals at relevant P-T conditions of the mantle transition zone. However, the ultrasonic velocity measurements in multianvil in China have been limited to < 6 GPa conditions in the past. Recently, we developed a new ultrasonic velocity measurement system in a 1 000 t Walker type multianvil press installed in China University of Geosciences (Wuhan) and measured the velocities of an Mg2SiO4 wadsleyite polycrystalline sample up to 18 GPa. The results are comparable with those of previous ultrasonic studies. For the first time in China, the sound velocity measurement was taken at high pressure conditions of the mantle transition zone in a multianvil with ultrasonic techniques, bridging the gap between the domestic and the international advanced level. The technique would provide not only experimental constraints on the interpretation of the geophysical observation beneath China and surrounding regions, but also experimental supports for the studies on the elastic properties of minerals/rocks and condensed materials in China.
2016, 41(9): 1461-1478.
doi: 10.3799/dqkx.2016.512
Abstract:
The porphyraceous hornblende biotite granodiorite is generated in the Ziyunshan pluton, Central Hunan Province, which hosts many mafic microgranular enclaves (MMEs). This paper presents petrography, major and trace elements of whole-rock, and mineral chemistry of feldspar, pyroxene, as well as biotite of the igneous-texture mafic microgranular enclaves and host rocks, their genetic mechanism and geotectonic significance were investigated. The whole-rock geochemistry of host rocks is more stable than those of mafic microgranular enclaves, and the latter were characterized by relatively depleted SiO2 and enriched Na2O. Both of them are represented by metaluminous, calc-alkaline and magnesian, and enrichment of LREE and LILE and depletion of HREE and HFSE. The plagioclase, pyroxene and biotite of host rocks and mafic microgranular enclaves belong to andesine, ferrosalite-salite and ferribiotite, respectively, showing similar characteristics of mineral chemistry. According to a comprehensive analysis of petrographical characteristics and geochemical data, it is suggested that (1) the host rock belongs to I-type and ACG-type granite, showing the characteristics of crust-mantle mixing; (2) the mafic microgranular enclaves were formed in liquid state, having liquidity and featuring both mechanical and chemical interactions with host rocks; (3) the crystallization of the mafic microgranular enclaves can be classified into two stages: the initial one is undercooling and rapid crystallization stage, and the latter is slow crystallization stage. To sum up, the mafic microgranular enclaves in the Ziyunshan pluton were generated by mixing of mafic magmas (sub-alkaline tholeiite which formed from mantle) and its induced crustal felsic magma (products of partial melting of arenaceous rock in crust) in the relaxation period after the compressive stress period in the late Indo-Chinese epoch.
The porphyraceous hornblende biotite granodiorite is generated in the Ziyunshan pluton, Central Hunan Province, which hosts many mafic microgranular enclaves (MMEs). This paper presents petrography, major and trace elements of whole-rock, and mineral chemistry of feldspar, pyroxene, as well as biotite of the igneous-texture mafic microgranular enclaves and host rocks, their genetic mechanism and geotectonic significance were investigated. The whole-rock geochemistry of host rocks is more stable than those of mafic microgranular enclaves, and the latter were characterized by relatively depleted SiO2 and enriched Na2O. Both of them are represented by metaluminous, calc-alkaline and magnesian, and enrichment of LREE and LILE and depletion of HREE and HFSE. The plagioclase, pyroxene and biotite of host rocks and mafic microgranular enclaves belong to andesine, ferrosalite-salite and ferribiotite, respectively, showing similar characteristics of mineral chemistry. According to a comprehensive analysis of petrographical characteristics and geochemical data, it is suggested that (1) the host rock belongs to I-type and ACG-type granite, showing the characteristics of crust-mantle mixing; (2) the mafic microgranular enclaves were formed in liquid state, having liquidity and featuring both mechanical and chemical interactions with host rocks; (3) the crystallization of the mafic microgranular enclaves can be classified into two stages: the initial one is undercooling and rapid crystallization stage, and the latter is slow crystallization stage. To sum up, the mafic microgranular enclaves in the Ziyunshan pluton were generated by mixing of mafic magmas (sub-alkaline tholeiite which formed from mantle) and its induced crustal felsic magma (products of partial melting of arenaceous rock in crust) in the relaxation period after the compressive stress period in the late Indo-Chinese epoch.
2016, 41(9): 1479-1488.
doi: 10.3799/dqkx.2016.516
Abstract:
Lithostratigraphic units established correct or not, which is related to the regional stratum sequence, the comparison of the stratum, the analysis and the structural evolution of the basin, is one of the most important research contents in the study of geology. Recently, regional geological survey of 1:50 000 scale in Hala'alate area confirmed that "Jiamuhe Formation" in West Junggar was not previously described sandwich-like interbedded volcanic rocks and continental clastic rocks, but constituted by the lower continental coarse clastic rocks and the upper volcanic rocks with regional angular unconformity relations, clear sequence, and obvious rock associations. The upper portion of volcanic rocks develops complete volcanic edifice including volcanic channel with aggromerate and subvolcanic rocks, strains and dikes intruded continental coarse clastic rocks, and volcanic eruption with basic lavas and tuffs angular unconformity contacted with continental coarse clastic rocks. Moreover, the lower portion of terrestrial conglomerate-gravel coarse sandstone has typical molasse features, containing plant and pollen fossils in Early Permian, such as Paracalamites stenocostatus, Lepidodendrales, and Striatoabietites. Based on Stratigraphic Guide of China and stratum lithostratigraphic standard, as well as the principle of formation's naming priority, we remove the continental volcanic rocks with typical volcanic edifice from initial Jiamuhe Formation (redefining as Baiyanghe Formation), to update a new Jiamuhe Formation only including terrestrial conglomerate-gravel coarse sandstone. The results provide significant evidence for the correct establishment of the stratigraphic unit, a reasonable regional stratigraphic division and comparison.
Lithostratigraphic units established correct or not, which is related to the regional stratum sequence, the comparison of the stratum, the analysis and the structural evolution of the basin, is one of the most important research contents in the study of geology. Recently, regional geological survey of 1:50 000 scale in Hala'alate area confirmed that "Jiamuhe Formation" in West Junggar was not previously described sandwich-like interbedded volcanic rocks and continental clastic rocks, but constituted by the lower continental coarse clastic rocks and the upper volcanic rocks with regional angular unconformity relations, clear sequence, and obvious rock associations. The upper portion of volcanic rocks develops complete volcanic edifice including volcanic channel with aggromerate and subvolcanic rocks, strains and dikes intruded continental coarse clastic rocks, and volcanic eruption with basic lavas and tuffs angular unconformity contacted with continental coarse clastic rocks. Moreover, the lower portion of terrestrial conglomerate-gravel coarse sandstone has typical molasse features, containing plant and pollen fossils in Early Permian, such as Paracalamites stenocostatus, Lepidodendrales, and Striatoabietites. Based on Stratigraphic Guide of China and stratum lithostratigraphic standard, as well as the principle of formation's naming priority, we remove the continental volcanic rocks with typical volcanic edifice from initial Jiamuhe Formation (redefining as Baiyanghe Formation), to update a new Jiamuhe Formation only including terrestrial conglomerate-gravel coarse sandstone. The results provide significant evidence for the correct establishment of the stratigraphic unit, a reasonable regional stratigraphic division and comparison.
2016, 41(9): 1489-1498.
doi: 10.3799/dqkx.2016.504
Abstract:
The western Qiongnan suture zone, i.e., Jiusuo-Lingshui fault belt, at the northern margin of the South China Sea, is important in tectonics. To better understand the tectonic evidences and ductile shear belts, a study is done in this area. Three types of rocks are sampled from the Xiaomei ductile shear zone on Hainan island, including granite, garnet quartz schist and granitic gneiss. Their shear surfaces were observed and analyzed through scanning electron microscope (SEM) at nanoscale. The results show multiple nano-textures and nanostructures in all three kinds of rocks and a positive relationship between the development degree of nanoparticles and the stress of the rocks. The authors propose several possible formation machanism of nanoparticles on the shear surfaces in this area, which may be thermal decomposition of sheet silicates under shear stress, or brittle deformation of minerals (especially feldspar with mechanical twins) after ductile deformation, then followed by crushing and grinding of the particles to nanoscale under shear force. Samples from the Taroko ductile shear belt, a part of the Taroko fault zone in Taiwan show similar nano characteristics to the Xiaomei ductile shear zone, implying both may have been in the same tectonic setting of a deep fracture as the Jiusuo-Lingshui fault belt. This study can therefore provide important observational facts for determining the structural properties and spatial positions of the Jiusuo-Lingshui fault belt.
The western Qiongnan suture zone, i.e., Jiusuo-Lingshui fault belt, at the northern margin of the South China Sea, is important in tectonics. To better understand the tectonic evidences and ductile shear belts, a study is done in this area. Three types of rocks are sampled from the Xiaomei ductile shear zone on Hainan island, including granite, garnet quartz schist and granitic gneiss. Their shear surfaces were observed and analyzed through scanning electron microscope (SEM) at nanoscale. The results show multiple nano-textures and nanostructures in all three kinds of rocks and a positive relationship between the development degree of nanoparticles and the stress of the rocks. The authors propose several possible formation machanism of nanoparticles on the shear surfaces in this area, which may be thermal decomposition of sheet silicates under shear stress, or brittle deformation of minerals (especially feldspar with mechanical twins) after ductile deformation, then followed by crushing and grinding of the particles to nanoscale under shear force. Samples from the Taroko ductile shear belt, a part of the Taroko fault zone in Taiwan show similar nano characteristics to the Xiaomei ductile shear zone, implying both may have been in the same tectonic setting of a deep fracture as the Jiusuo-Lingshui fault belt. This study can therefore provide important observational facts for determining the structural properties and spatial positions of the Jiusuo-Lingshui fault belt.
2016, 41(9): 1499-1510.
doi: 10.3799/dqkx.2016.513
Abstract:
The occurrence of geogenic arsenic in natural water environment is one of the significant hazards to human beings in the world. In high-temperature, sulfide-rich geothermal waters, thioarsenicals are likely the major species of arsenic. In view that there has been so far no quantitative test method for thioarsenic species in China, a hydrogeochemical code, PHREEQC, with its wateq4f.dat database being updated by the latest thermodynamic data for thioarsenicals, was used for calculating the arsenic species distribution in various types of hot springs from the Rehai hydrothermal area located in the Tengchong geothermal belt, Yunnan Province. The results show that the major species of arsenic in the Rehai hot springs is thioarsenate, arsenate and arsenite comes second, and the thioarsenite concentrations are extremely low; the descending order of thioarsenate species in terms of their average percentages is: monothioarsenate, trithioarsenate, tetrathioarsenate, and dithioarsenate. pH, Eh and total sulfide concentration are the controlling factors for the arsenic speciation in hot springs. Under acidic condition, the main species of arsenic are thioarsenate and arsenite, whereas under neutral/weak alkaline conditions, thioarsenate is predominant with arsenate being the second most important species. Comparative reducing environment and high sulfide concentration in geothermal water are favorable for the stable existence of thioarsenicals, especially trithioarsenate and tetrathioarsenate.
The occurrence of geogenic arsenic in natural water environment is one of the significant hazards to human beings in the world. In high-temperature, sulfide-rich geothermal waters, thioarsenicals are likely the major species of arsenic. In view that there has been so far no quantitative test method for thioarsenic species in China, a hydrogeochemical code, PHREEQC, with its wateq4f.dat database being updated by the latest thermodynamic data for thioarsenicals, was used for calculating the arsenic species distribution in various types of hot springs from the Rehai hydrothermal area located in the Tengchong geothermal belt, Yunnan Province. The results show that the major species of arsenic in the Rehai hot springs is thioarsenate, arsenate and arsenite comes second, and the thioarsenite concentrations are extremely low; the descending order of thioarsenate species in terms of their average percentages is: monothioarsenate, trithioarsenate, tetrathioarsenate, and dithioarsenate. pH, Eh and total sulfide concentration are the controlling factors for the arsenic speciation in hot springs. Under acidic condition, the main species of arsenic are thioarsenate and arsenite, whereas under neutral/weak alkaline conditions, thioarsenate is predominant with arsenate being the second most important species. Comparative reducing environment and high sulfide concentration in geothermal water are favorable for the stable existence of thioarsenicals, especially trithioarsenate and tetrathioarsenate.
2016, 41(9): 1511-1525.
doi: 10.3799/dqkx.2016.115
Abstract:
Graphic granite, found predominantly in granitic pegmatite, is a leucocratic granitic rock consisting of an intimate intergrowth of alkali feldspar and quartz with a distinctive texture as ancient cuneiform writing when viewed in certain cross sections. Deciphering the graphic texture is important for understanding its origin and the crystallization process of granitic rocks. In this paper, we present investigations on petrology, mineral compositions, crystallographic relationship and topotaxy of quartz and alkali feldspar in graphic granites from the Fangshan pluton, North China and Huilanshan, Central China. The results indicate follows (1) The volume content of quartz usually ranges from 20% to 45%, and the composition of feldspar in graphic granites depends greatly on the formation conditions. However, the quartz-feldspar ratio and the composition of feldspar in graphic granites are relatively stable in coeval graphic granites in the same area. (2) The euhedral to subhedral coarse-grained feldspar host in graphic granites can be alkali feldspar or plagioclase. Microscopically, the feldspar host is usually a perthite, which is decomposed into irregular intergrowth of sodic and potassic feldspar. (3) The majority of the quartz grains undergrown with host feldspar are in the form of sub-parallel tabular, long rods and unconnected dendritic crystals, which only show a distinctive graphic texture in certain cross sections. (4) Under cross polarized light microscopy, multiple domains of quartz grains exhibit a nearly simultaneous extinction within a single crystal of feldspar. (5) Dauphiné twin of quartz, occasionally accompanied by Japan twin, is commonly developed in graphic granites. (6) Intergrowth of sodic and potassic feldspar, resulted from sub-solidus exsolution of precursor host feldspar solid solution, has almost the same orientations of (100), (010) and (001) planes and [001] axis. (7) A definite crystallographic orientation relationship between the majority of quartz grains and the feldspar host is identified in that[1123]Quartz//[001]Feldspar. These results suggest that the nucleation and growth of quartz are controlled by the host feldspar, which supports the simultaneous growth model of quartz and feldspar in graphic granites.
Graphic granite, found predominantly in granitic pegmatite, is a leucocratic granitic rock consisting of an intimate intergrowth of alkali feldspar and quartz with a distinctive texture as ancient cuneiform writing when viewed in certain cross sections. Deciphering the graphic texture is important for understanding its origin and the crystallization process of granitic rocks. In this paper, we present investigations on petrology, mineral compositions, crystallographic relationship and topotaxy of quartz and alkali feldspar in graphic granites from the Fangshan pluton, North China and Huilanshan, Central China. The results indicate follows (1) The volume content of quartz usually ranges from 20% to 45%, and the composition of feldspar in graphic granites depends greatly on the formation conditions. However, the quartz-feldspar ratio and the composition of feldspar in graphic granites are relatively stable in coeval graphic granites in the same area. (2) The euhedral to subhedral coarse-grained feldspar host in graphic granites can be alkali feldspar or plagioclase. Microscopically, the feldspar host is usually a perthite, which is decomposed into irregular intergrowth of sodic and potassic feldspar. (3) The majority of the quartz grains undergrown with host feldspar are in the form of sub-parallel tabular, long rods and unconnected dendritic crystals, which only show a distinctive graphic texture in certain cross sections. (4) Under cross polarized light microscopy, multiple domains of quartz grains exhibit a nearly simultaneous extinction within a single crystal of feldspar. (5) Dauphiné twin of quartz, occasionally accompanied by Japan twin, is commonly developed in graphic granites. (6) Intergrowth of sodic and potassic feldspar, resulted from sub-solidus exsolution of precursor host feldspar solid solution, has almost the same orientations of (100), (010) and (001) planes and [001] axis. (7) A definite crystallographic orientation relationship between the majority of quartz grains and the feldspar host is identified in that[1123]Quartz//[001]Feldspar. These results suggest that the nucleation and growth of quartz are controlled by the host feldspar, which supports the simultaneous growth model of quartz and feldspar in graphic granites.
2016, 41(9): 1526-1538.
doi: 10.3799/dqkx.2016.511
Abstract:
The reservoir in Upper Miocene Huangliu Formation of Yinggehai basin, which is located between Kuntum paleo-uplift and Hainan paleo-uplift, is shallow-marine gravity flow deposits with burial depth ranging from 2 600 to 3 500 m. Analyzing the provenance of the sandbody is significant in understanding its distribution and "source to sink system", hence for the oil-gas exploration and development in this area. The provenance of sediments in Upper Miocene Huangliu Formation was analyzed by integrating the components of the sandstones, assemblage styles of the heavy mineral, paleo-current direction and geochemistry characteristics of the sandstones. Results show follows. (1) There are two provenances, one from west and the other from east, in the study area. Western sourced sandstones form the shallow-marine gravity flow which are mainly sublitharenite with high feldspar (average is 6.1%) and lithic (average is 11.7%) contents, low shale content (average is 3.8%). However, eastern sourced sandstones, which are mainly subarkose-quartz siltstone with low feldspar and lithic contents with averages of 4.6% and 2.7%, respectively, high compositional maturity, high shale contents (average is 18.6%), form the neritic sand bar. (2) The shallow-marine gravity flow sandstones exhibit low zircon, tourmaline contents, and high magnetite, garnet contents, while the neritic sand bar sandstones exhibit high zircon, tourmaline and leucosphenite contents, and low magnetite, garnet contents. The direction of paleo-current in study area is from southeastward to eastward. (3) The similar rare earth element (REE) patterns of 28 sandstones from three western wells indicate that they were sourced from the same provenance. The diagrams of Th-Sc and Co/Th-La/Sc and elemental ratios of these sandstone samples show that they were derived from intermediate to felsic source rocks. The measured geochemistry data of these core samples fall into the fields of active continental margin or continental island arc in the diagrams of La-Th-Sc, Th-Sc-Zr/10, Ti/Zr-La/Sc and major element discrimination, indicating that the source rocks of the shallow-marine gravity flow sandstones were formed under the tectonic setting of an convergent environment. (4) The integrated method for provenance analysis indicates that the shallow-marine gravity flow sandstones were derived from the western Kuntum uplift. The shallow-marine gravity flow sandstones in western mud diaper belts are large in scale, rich in gas, better in reservoir properties and the main favorable exploration target towards the west, whereas the neritic sand bar sandstones in eastern mud diaper belts are small in scale, poor in reservoir quality.
The reservoir in Upper Miocene Huangliu Formation of Yinggehai basin, which is located between Kuntum paleo-uplift and Hainan paleo-uplift, is shallow-marine gravity flow deposits with burial depth ranging from 2 600 to 3 500 m. Analyzing the provenance of the sandbody is significant in understanding its distribution and "source to sink system", hence for the oil-gas exploration and development in this area. The provenance of sediments in Upper Miocene Huangliu Formation was analyzed by integrating the components of the sandstones, assemblage styles of the heavy mineral, paleo-current direction and geochemistry characteristics of the sandstones. Results show follows. (1) There are two provenances, one from west and the other from east, in the study area. Western sourced sandstones form the shallow-marine gravity flow which are mainly sublitharenite with high feldspar (average is 6.1%) and lithic (average is 11.7%) contents, low shale content (average is 3.8%). However, eastern sourced sandstones, which are mainly subarkose-quartz siltstone with low feldspar and lithic contents with averages of 4.6% and 2.7%, respectively, high compositional maturity, high shale contents (average is 18.6%), form the neritic sand bar. (2) The shallow-marine gravity flow sandstones exhibit low zircon, tourmaline contents, and high magnetite, garnet contents, while the neritic sand bar sandstones exhibit high zircon, tourmaline and leucosphenite contents, and low magnetite, garnet contents. The direction of paleo-current in study area is from southeastward to eastward. (3) The similar rare earth element (REE) patterns of 28 sandstones from three western wells indicate that they were sourced from the same provenance. The diagrams of Th-Sc and Co/Th-La/Sc and elemental ratios of these sandstone samples show that they were derived from intermediate to felsic source rocks. The measured geochemistry data of these core samples fall into the fields of active continental margin or continental island arc in the diagrams of La-Th-Sc, Th-Sc-Zr/10, Ti/Zr-La/Sc and major element discrimination, indicating that the source rocks of the shallow-marine gravity flow sandstones were formed under the tectonic setting of an convergent environment. (4) The integrated method for provenance analysis indicates that the shallow-marine gravity flow sandstones were derived from the western Kuntum uplift. The shallow-marine gravity flow sandstones in western mud diaper belts are large in scale, rich in gas, better in reservoir properties and the main favorable exploration target towards the west, whereas the neritic sand bar sandstones in eastern mud diaper belts are small in scale, poor in reservoir quality.
2016, 41(9): 1539-1547.
doi: 10.3799/dqkx.2016.521
Abstract:
It is generally held that most gas in Qiongdongnan basin, the South China Sea, is coal type gas and comes from the Oligocene and Miocene marine source rocks, while the existence of Eocene source rocks is uncertain. Determining Eocene source rocks will provide significant foundation for oil and gas exploration. The systematical analysis of fluid inclusions of 45 samples and geochemical characteristics of gas and light hydrocarbons indicate that most of the gas is oil type gas and oil-coal gas with 4 gas charging episodes. The first gas charging episode probably comes from Eocene source rocks in eastern of Qiongdongnan basin, the South China Sea. The results indicate that it probably develops kerogen type Ⅰ of Eocene source, distributed in Songnan-Baodao-Changchang depression and Beijiao depression of Qiongdongnan basin, the South China Sea, which can be regarded as advantage exploration targets.
It is generally held that most gas in Qiongdongnan basin, the South China Sea, is coal type gas and comes from the Oligocene and Miocene marine source rocks, while the existence of Eocene source rocks is uncertain. Determining Eocene source rocks will provide significant foundation for oil and gas exploration. The systematical analysis of fluid inclusions of 45 samples and geochemical characteristics of gas and light hydrocarbons indicate that most of the gas is oil type gas and oil-coal gas with 4 gas charging episodes. The first gas charging episode probably comes from Eocene source rocks in eastern of Qiongdongnan basin, the South China Sea. The results indicate that it probably develops kerogen type Ⅰ of Eocene source, distributed in Songnan-Baodao-Changchang depression and Beijiao depression of Qiongdongnan basin, the South China Sea, which can be regarded as advantage exploration targets.
2016, 41(9): 1548-1560.
doi: 10.3799/dqkx.2016.508
Abstract:
Tan-Lu strike-slip fault in Bohai sea area is an important hydrocarbon enrichment zone. But it is not clear whether strike-slip transfer zone controls on the formation of medium and large-sized oilfields. This paper systematically analyzes the Tan-Lu strike-slip transfer zone and its control on the development of medium and large-sized oilfields on the basis of detailed interpretation of 400 wells and 3-D seismic data over the fault zone. Three types of transfer zones developed in the Tan-Lu strike-slip fault zone are recognized according to the position of the transition zone in the strike-slip fault zone, which are named as fault-edge transfer zones, fault-overlap transfer zones and fault terminal transfer zones respectively. These transitions can be further divided into seven types, which are sigmoid, overlapping, duplex, broom-like, shingled, conjugated and compound types of transfer zones. According to the local stress state, each type of transfer zone is further subdivided into contractional and extensional types of transfer zones. Contractional transfer zones control the formation of large-scale traps, whereas extensional transfer zones control the formation of small-scale traps. Geological oil reserves related to contractional transfer zones account for up to 81% of total geological oil reserve of the Tan-Lu strike-slip fault zones. Therefore, contractional transfer zones developed in the strike-slip fault zones should serve as excellent exploration targets for the large-scale oilfield with great potential.
Tan-Lu strike-slip fault in Bohai sea area is an important hydrocarbon enrichment zone. But it is not clear whether strike-slip transfer zone controls on the formation of medium and large-sized oilfields. This paper systematically analyzes the Tan-Lu strike-slip transfer zone and its control on the development of medium and large-sized oilfields on the basis of detailed interpretation of 400 wells and 3-D seismic data over the fault zone. Three types of transfer zones developed in the Tan-Lu strike-slip fault zone are recognized according to the position of the transition zone in the strike-slip fault zone, which are named as fault-edge transfer zones, fault-overlap transfer zones and fault terminal transfer zones respectively. These transitions can be further divided into seven types, which are sigmoid, overlapping, duplex, broom-like, shingled, conjugated and compound types of transfer zones. According to the local stress state, each type of transfer zone is further subdivided into contractional and extensional types of transfer zones. Contractional transfer zones control the formation of large-scale traps, whereas extensional transfer zones control the formation of small-scale traps. Geological oil reserves related to contractional transfer zones account for up to 81% of total geological oil reserve of the Tan-Lu strike-slip fault zones. Therefore, contractional transfer zones developed in the strike-slip fault zones should serve as excellent exploration targets for the large-scale oilfield with great potential.
2016, 41(9): 1561-1571.
doi: 10.3799/dqkx.2016.116
Abstract:
Source rock in Yueguifeng Formation of Lower Paleocene is the main source rock series in Lishui-Jiaojiang hydrocarbon generating sag of the East China Sea shelf basin. Using drilling, seismic data combined with organic geochemistry and paleontology data of hydrocarbon source rock, the development controlling factors for the Yueguifeng Formation of Lower Paleocene are discussed and the forming model also is established based on the analysis of characteristics of the hydrocarbon source rock and tectonic-sedimentary-paleoclimate development background in this study. It is found that source rocks in Yueguifeng Formation of Lishui-Jiaojiang sag are characterized by wide distribution, large thickness and multiple thickness centers abundance of organic matter, type Ⅱ2 dominated organic matter, and relatively high maturity. Development background of Yueguifeng Formation is an intensive separation and relatively closed lake environment with subhumid-humid subtropical climate condition, and predominantly aquatic organic matter contribution. Development of hydrocarbon source rocks in Yueguifeng Formation is mainly affected by deposit-sedimentation rate, parent material source and preservation condition of organic matter, and it could be concluded that its forming model features with "rapid subsidence, humid climate, aquatic organic matter contribution, fresh-brackish water, and weak oxidation-reduction environment".
Source rock in Yueguifeng Formation of Lower Paleocene is the main source rock series in Lishui-Jiaojiang hydrocarbon generating sag of the East China Sea shelf basin. Using drilling, seismic data combined with organic geochemistry and paleontology data of hydrocarbon source rock, the development controlling factors for the Yueguifeng Formation of Lower Paleocene are discussed and the forming model also is established based on the analysis of characteristics of the hydrocarbon source rock and tectonic-sedimentary-paleoclimate development background in this study. It is found that source rocks in Yueguifeng Formation of Lishui-Jiaojiang sag are characterized by wide distribution, large thickness and multiple thickness centers abundance of organic matter, type Ⅱ2 dominated organic matter, and relatively high maturity. Development background of Yueguifeng Formation is an intensive separation and relatively closed lake environment with subhumid-humid subtropical climate condition, and predominantly aquatic organic matter contribution. Development of hydrocarbon source rocks in Yueguifeng Formation is mainly affected by deposit-sedimentation rate, parent material source and preservation condition of organic matter, and it could be concluded that its forming model features with "rapid subsidence, humid climate, aquatic organic matter contribution, fresh-brackish water, and weak oxidation-reduction environment".
2016, 41(9): 1572-1582.
doi: 10.3799/dqkx.2016.505
Abstract:
Paleolakes on Martian surface have attracted great interests of researchers as they contain information on ancient aqueous environment of Mars and are important for the detection of habitable environment on Mars. With the implementing of Chinese Mars exploration program, it's of great significances to review the achievements in Martian paleolake study. We summarize the sedimentary geomorphology, mineral compositions, activity periods and global distribution of the paleolakes. On this basis, we discussed the unresolved questions in paleolake study and proposed that future studies should focus on the detailed investigation and geologic mapping of paleolakes, post-lacustrine modification processes, identification of other paleolake types and the comparative study of Martian and terrestrial paleolakes.
Paleolakes on Martian surface have attracted great interests of researchers as they contain information on ancient aqueous environment of Mars and are important for the detection of habitable environment on Mars. With the implementing of Chinese Mars exploration program, it's of great significances to review the achievements in Martian paleolake study. We summarize the sedimentary geomorphology, mineral compositions, activity periods and global distribution of the paleolakes. On this basis, we discussed the unresolved questions in paleolake study and proposed that future studies should focus on the detailed investigation and geologic mapping of paleolakes, post-lacustrine modification processes, identification of other paleolake types and the comparative study of Martian and terrestrial paleolakes.
2016, 41(9): 1583-1592.
doi: 10.3799/dqkx.2016.117
Abstract:
Evolution mechanism and movement process of rock avalanche are dominated by rock mass structure. The geometric information on rock discontinuities in Jiweishan landslide area was collected using terrestrial laser scanner (TLS). In addition, discrete element method (DEM), which takes into account the rock mass structure, was employed to investigate the evolution process and deposit areas of Jiweishan landslide. Results show that: (1) the features of rock mass structure were determined by rock discontinuities whose orientation was obtained by geometric calculations and cluster analysis on point cloud in a short time, and the identification and clustering of rock discontinuities were completed based on the distribution of orientation; (2) DEM and features of rock mass structure were combined to assess the deposit areas of rock avalanche, and simulation results have a good agreement with the actual situations.
Evolution mechanism and movement process of rock avalanche are dominated by rock mass structure. The geometric information on rock discontinuities in Jiweishan landslide area was collected using terrestrial laser scanner (TLS). In addition, discrete element method (DEM), which takes into account the rock mass structure, was employed to investigate the evolution process and deposit areas of Jiweishan landslide. Results show that: (1) the features of rock mass structure were determined by rock discontinuities whose orientation was obtained by geometric calculations and cluster analysis on point cloud in a short time, and the identification and clustering of rock discontinuities were completed based on the distribution of orientation; (2) DEM and features of rock mass structure were combined to assess the deposit areas of rock avalanche, and simulation results have a good agreement with the actual situations.
2016, 41(9): 1593-1602.
doi: 10.3799/dqkx.2016.118
Abstract:
Landslides in Three Gorges reservoir area are affected by both the rainfall and the reservoir water, but their respective contribution and the laws of the landslide evolution remain unclear. In this paper, we analyzed the rainfall and water level data, and applied a varying coefficient regression model for landslide displacement prediction taking Shuping landslide and Bazimen landslide in the reservoir area as the study area. The results of experiments show that the improved varying coefficient regression model is not only more accurate than traditional linear regression model, auto-regressive Integrated moving average model and support vector mchine model, but also it can give quantitative contribution of each factor on the landslide displacement.
Landslides in Three Gorges reservoir area are affected by both the rainfall and the reservoir water, but their respective contribution and the laws of the landslide evolution remain unclear. In this paper, we analyzed the rainfall and water level data, and applied a varying coefficient regression model for landslide displacement prediction taking Shuping landslide and Bazimen landslide in the reservoir area as the study area. The results of experiments show that the improved varying coefficient regression model is not only more accurate than traditional linear regression model, auto-regressive Integrated moving average model and support vector mchine model, but also it can give quantitative contribution of each factor on the landslide displacement.
2016, 41(9): 1603-1610.
doi: 10.3799/dqkx.2016.519
Abstract:
The energy dissipation and energy release of fault gouge could be explained by analyzing the characteristics of stick-slip of glass beads. The glass beads of 0.6-0.8 mm were used to conduct the test from CVP company. The triaxial tests of dry and loose glass beads were carried out under the cell pressure of 30, 60, 100, 200, 400 and 600 kPa with axial strain rate of 0.02 mm/min. The energy dissipation and energy release in the process of failure are discussed with the axial strain rate of 10% in order to decrease the errors due to the rotation of principal stress. The results show that with increasing of cell pressure, the frequency of main shock decreases, the deviatoric stress drop increases, the ratio of deviatoric stress drop to maximum deviatoric stress becomes stable gradually. The volume of sample shrinks and acoustic emission appears in the moment of deviatoric stress drop. The energy controls the deformation and failure properties of the sample during stick-slip: the more the dissipation is, the less the frequency of sliding becomes. Stick-slip can be expressed as the process of energy dissipation and energy release. Finally, the three stages of sliding during stick-slip are discussed from the aspect of thermodynamics. The stick-slip motion is a combined effect of irreversible dissipated energy and releasable strain energy.
The energy dissipation and energy release of fault gouge could be explained by analyzing the characteristics of stick-slip of glass beads. The glass beads of 0.6-0.8 mm were used to conduct the test from CVP company. The triaxial tests of dry and loose glass beads were carried out under the cell pressure of 30, 60, 100, 200, 400 and 600 kPa with axial strain rate of 0.02 mm/min. The energy dissipation and energy release in the process of failure are discussed with the axial strain rate of 10% in order to decrease the errors due to the rotation of principal stress. The results show that with increasing of cell pressure, the frequency of main shock decreases, the deviatoric stress drop increases, the ratio of deviatoric stress drop to maximum deviatoric stress becomes stable gradually. The volume of sample shrinks and acoustic emission appears in the moment of deviatoric stress drop. The energy controls the deformation and failure properties of the sample during stick-slip: the more the dissipation is, the less the frequency of sliding becomes. Stick-slip can be expressed as the process of energy dissipation and energy release. Finally, the three stages of sliding during stick-slip are discussed from the aspect of thermodynamics. The stick-slip motion is a combined effect of irreversible dissipated energy and releasable strain energy.
2016, 41(9): 1611-1618.
doi: 10.3799/dqkx.2016.119
Abstract:
The core task of the third stage of China's Lunar Exploration Program is to realize the lunar drilling and sampling and returning to the earth. 2-meter-deep lunar soil sampling is required through drilling method. Due to the extreme environment on the lunar surface, an auger core drillig tool with joint inner and outer pipe is proposed in this paper. The core in the inner pipe is obtained by pulling the soft bag, and the core in the outer pipe is transported to the collector by the helical blade. Drilling tests on the lunar soil simulant indicate that the auger drilling tool is reliable for coring, especially for the superficial lunar soil with depth less than 0.6 meters. The influences of drilling parameters on core recovery and drilling power consumption in the tests are studied Relationships between rotation speed, the range of drilling footage speed and power are concluded, which can facilitate the development of core drilling tools and the determination of drilling parameters in the lunar environment.
The core task of the third stage of China's Lunar Exploration Program is to realize the lunar drilling and sampling and returning to the earth. 2-meter-deep lunar soil sampling is required through drilling method. Due to the extreme environment on the lunar surface, an auger core drillig tool with joint inner and outer pipe is proposed in this paper. The core in the inner pipe is obtained by pulling the soft bag, and the core in the outer pipe is transported to the collector by the helical blade. Drilling tests on the lunar soil simulant indicate that the auger drilling tool is reliable for coring, especially for the superficial lunar soil with depth less than 0.6 meters. The influences of drilling parameters on core recovery and drilling power consumption in the tests are studied Relationships between rotation speed, the range of drilling footage speed and power are concluded, which can facilitate the development of core drilling tools and the determination of drilling parameters in the lunar environment.
