2008 Vol. 33, No. 3
Display Method:
2008, 33(3): 289-300.
PDF 954KB
Abstract:
Clay mineral assemblages, crystallinity, chemistry and micromorphology of clay particles in sediments from ODP Site 1146 in the northern South China Sea (SCS) were analyzed and used to trace sediment sources and obtain proxy records of past changes in the East Asian monsoon climate since the Miocene based on a multi-approach including X-ray diffraction (XRD) and scanning electron microscope combined with energy dispersive X-ray spectrometer (SEM-EDS).Clay minerals mainly consist of illite and smectite, with associated chlorite and kaolinite.The illite at ODP Site 1146 has very well-to-well crystallinity, and smectite has moderate-to-poor crystallinity.In SEM the smectite particles at ODP Site 1146 often appear cauliflower-like, a typical micromorphology of volcanic smecites.The smectite at ODP Site 1146 is relatively rich in Si element, but poor in Fe, very similar to the smectite from the West Philippine Sea.In contrast, the chemical composition of illite at ODP Site 1146 has no obvious differences from those of the Loess, Yellow River, Yangtze River, and Pearl River.Sediment source studies indicate that smectite originates mainly from Luzon, kaolinite from the Pearl River and illite and chlorite from the Pearl River, Taiwan and/or the Yangtze River respectively.The clay mineral assemblages at ODP Site 1146 were not only controlled by the continental weathering regimes surrounding the SCS but also by the changing strength of the transport processes.The ratios of (illite+chlorite) /smectite at ODP Site 1146 were adopted as proxies for East Asian monsoon evolution.The consistent variation of this clay proxy with those from loess, eolian deposition in the North Pacific and planktonic and benthic foraminifera, and black carbon in the SCS since 20 Ma shows that three profound shifts of the East Asian winter monsoon intensity, aridity in the Asian inland and the intensity of winter monsoon relative to summer monsoon, occurred at ~ 15 Ma, ~ 8 Ma and the youngest at about 3 Ma.The phased uplift of the Himalaya-Tibetan plateau may have played a significant role in strengthening the Asian monsoon at 15 Ma, 8 Ma and 3 Ma.
Clay mineral assemblages, crystallinity, chemistry and micromorphology of clay particles in sediments from ODP Site 1146 in the northern South China Sea (SCS) were analyzed and used to trace sediment sources and obtain proxy records of past changes in the East Asian monsoon climate since the Miocene based on a multi-approach including X-ray diffraction (XRD) and scanning electron microscope combined with energy dispersive X-ray spectrometer (SEM-EDS).Clay minerals mainly consist of illite and smectite, with associated chlorite and kaolinite.The illite at ODP Site 1146 has very well-to-well crystallinity, and smectite has moderate-to-poor crystallinity.In SEM the smectite particles at ODP Site 1146 often appear cauliflower-like, a typical micromorphology of volcanic smecites.The smectite at ODP Site 1146 is relatively rich in Si element, but poor in Fe, very similar to the smectite from the West Philippine Sea.In contrast, the chemical composition of illite at ODP Site 1146 has no obvious differences from those of the Loess, Yellow River, Yangtze River, and Pearl River.Sediment source studies indicate that smectite originates mainly from Luzon, kaolinite from the Pearl River and illite and chlorite from the Pearl River, Taiwan and/or the Yangtze River respectively.The clay mineral assemblages at ODP Site 1146 were not only controlled by the continental weathering regimes surrounding the SCS but also by the changing strength of the transport processes.The ratios of (illite+chlorite) /smectite at ODP Site 1146 were adopted as proxies for East Asian monsoon evolution.The consistent variation of this clay proxy with those from loess, eolian deposition in the North Pacific and planktonic and benthic foraminifera, and black carbon in the SCS since 20 Ma shows that three profound shifts of the East Asian winter monsoon intensity, aridity in the Asian inland and the intensity of winter monsoon relative to summer monsoon, occurred at ~ 15 Ma, ~ 8 Ma and the youngest at about 3 Ma.The phased uplift of the Himalaya-Tibetan plateau may have played a significant role in strengthening the Asian monsoon at 15 Ma, 8 Ma and 3 Ma.
2008, 33(3): 301-312.
Abstract:
Element and Nd-Sr isotopic mobility during the weathering process of stratotypes for the Nanhuaian, Sinian and Cambrian sedimentary strata have been studied in eastern Three Gorges.Stratigraphic bedrocks of mudstone, glacial mudstone, sandstone, limestone and dolomitic limestone coupled with their correspondent soil layers by chemical weathering were analyzed.It demonstrates that (1) the intensity of chemical weathering of bedrocks is dominated by their lithology; (2) Due to its stability, Ti is regarded as immobile during chemical weathering.Thus, the variations of Ti concentrations in soil samples relative to their bedrocks are used to correct volume changes of soil layers during the weathering and accordingly to recalculate relative contents of other elements in the layers.It shows that obviously content decreasing for most elements in soil layers relative to their bedrocks is found for limestone and dolomitic limestone profiles; in contrast, soil samples from the mudstone profiles exhibit a relative stability for most elements.It, thus, suggests that the elemental mobility during chemical weathering of sedimentary rocks is dominated by their rock-forming minerals.Meanwhile, different classical elements show distinct mobility during the chemical weathering.Contents of chalcophile (Cu, Zn, Pb and Mo) and LILE (Rb, K, Sr and Ba) elements varied obviously, whereas those of the HFSE element (Zr, Hf, Nb and Ta) kept relatively constant; (3) Relative to their bedrocks, the variation of REE content in soil layers by mudstone is indistinctively, whereas that in soil layers by carbonate rocks changed evidently characterized both by enrichment in LREE and HREE relative to MREE and negative Eu and positive Ce anomalies; (4) Both Sr isotopic composition and Rb/Sr ratio changed remarkably during the weathering process of both carbonatic and argillaceous rocks, indicating an opening of their Rb-Sr isotopic system.It shows that the variation in Sr isotopic compositions of the soil layers relative to their bedrocks is dominated both by the lithology of their parental rocks and the Sr isotopic composition input during weathering.Accordingly, the Sr isotopic compositions of the soil layers are not indicative of their bedrocks; (5) The Sm/Nd ratio and Nd isotopic compositions of the soil layers weathered from carbonate and mudstone rocks essentially inherited the characters of their bedrocks, and their depleted mantle model ages (tDM) are indicative of their parental rocks.However, variable degree variations in Nd isotopic compositions are recognized for the soil samples weathered by sandstone and glacial mudstone.
Element and Nd-Sr isotopic mobility during the weathering process of stratotypes for the Nanhuaian, Sinian and Cambrian sedimentary strata have been studied in eastern Three Gorges.Stratigraphic bedrocks of mudstone, glacial mudstone, sandstone, limestone and dolomitic limestone coupled with their correspondent soil layers by chemical weathering were analyzed.It demonstrates that (1) the intensity of chemical weathering of bedrocks is dominated by their lithology; (2) Due to its stability, Ti is regarded as immobile during chemical weathering.Thus, the variations of Ti concentrations in soil samples relative to their bedrocks are used to correct volume changes of soil layers during the weathering and accordingly to recalculate relative contents of other elements in the layers.It shows that obviously content decreasing for most elements in soil layers relative to their bedrocks is found for limestone and dolomitic limestone profiles; in contrast, soil samples from the mudstone profiles exhibit a relative stability for most elements.It, thus, suggests that the elemental mobility during chemical weathering of sedimentary rocks is dominated by their rock-forming minerals.Meanwhile, different classical elements show distinct mobility during the chemical weathering.Contents of chalcophile (Cu, Zn, Pb and Mo) and LILE (Rb, K, Sr and Ba) elements varied obviously, whereas those of the HFSE element (Zr, Hf, Nb and Ta) kept relatively constant; (3) Relative to their bedrocks, the variation of REE content in soil layers by mudstone is indistinctively, whereas that in soil layers by carbonate rocks changed evidently characterized both by enrichment in LREE and HREE relative to MREE and negative Eu and positive Ce anomalies; (4) Both Sr isotopic composition and Rb/Sr ratio changed remarkably during the weathering process of both carbonatic and argillaceous rocks, indicating an opening of their Rb-Sr isotopic system.It shows that the variation in Sr isotopic compositions of the soil layers relative to their bedrocks is dominated both by the lithology of their parental rocks and the Sr isotopic composition input during weathering.Accordingly, the Sr isotopic compositions of the soil layers are not indicative of their bedrocks; (5) The Sm/Nd ratio and Nd isotopic compositions of the soil layers weathered from carbonate and mudstone rocks essentially inherited the characters of their bedrocks, and their depleted mantle model ages (tDM) are indicative of their parental rocks.However, variable degree variations in Nd isotopic compositions are recognized for the soil samples weathered by sandstone and glacial mudstone.
2008, 33(3): 313-319.
Abstract:
The velocities of a series of deep-seated xenoliths in Late Mesozoic-Cenozoic basaltic rocks from Tuoyun basin, western Xinjiang (NW China), are calculated.These data, combined with the published seismic velocities for the area, are used to define the composition and structure of the crust-mantle transitional zone beneath southwestern Tianshan.The calculated velocities of peridotite and granulite xenoliths are 6.98-7.36 km/s and 7.96-8.47 km/s, respectively.The comparison of these data with the seismic velocities shows the presence of the crust-mantle transitional zone in 40-48 km beneath southwestern Tianshan.The zone consists of quartz granulite, pyroxene granulite and olivine/garnet granulite from top to bottom, and then transfers into the upper mantle mainly composed of spinel-facies lherzolite with or without volatile component minerals (phlogopite or amphibole).Such crust-mantle structure of lithosphere can be well explained by magma underplating and metamorphism.
The velocities of a series of deep-seated xenoliths in Late Mesozoic-Cenozoic basaltic rocks from Tuoyun basin, western Xinjiang (NW China), are calculated.These data, combined with the published seismic velocities for the area, are used to define the composition and structure of the crust-mantle transitional zone beneath southwestern Tianshan.The calculated velocities of peridotite and granulite xenoliths are 6.98-7.36 km/s and 7.96-8.47 km/s, respectively.The comparison of these data with the seismic velocities shows the presence of the crust-mantle transitional zone in 40-48 km beneath southwestern Tianshan.The zone consists of quartz granulite, pyroxene granulite and olivine/garnet granulite from top to bottom, and then transfers into the upper mantle mainly composed of spinel-facies lherzolite with or without volatile component minerals (phlogopite or amphibole).Such crust-mantle structure of lithosphere can be well explained by magma underplating and metamorphism.
2008, 33(3): 320-328.
Abstract:
Analcime phonolite is a rare alkaline volcanic rock.Using the electron microprobe, X-ray powder diffraction, scanning electron microscope, and Raman spectroscopy, this paper studies characteristics of rock-forming minerals, coexisting relations and crystallization sequences of the analcime phonolite from the Damxung area, Qinghai-Tibet plateau.Phenocrysts are euhedral analcime and feldspar, while the groundmass is composed of K-feldspar, salite, titanomagnetite, and limonite.Analcime is primary and crystallizes in the late magmatic stage.Phenocrystal feldspars have secondary rims of K-feldspar, and their cores are plagioclases.Crystallization sequences are the plagioclase core of feldspar phenocrysts, analcime and K-feldspar in the rim of feldspar phenocrysts, K-feldspar in the groundmass, salite, titanomagnetite and limonite.The balance between analcime and melt places constraints on the P/T regime (5-13) ×108 Pa and 600-640 ℃ respectively, implying depths of origin in the deep crust.
Analcime phonolite is a rare alkaline volcanic rock.Using the electron microprobe, X-ray powder diffraction, scanning electron microscope, and Raman spectroscopy, this paper studies characteristics of rock-forming minerals, coexisting relations and crystallization sequences of the analcime phonolite from the Damxung area, Qinghai-Tibet plateau.Phenocrysts are euhedral analcime and feldspar, while the groundmass is composed of K-feldspar, salite, titanomagnetite, and limonite.Analcime is primary and crystallizes in the late magmatic stage.Phenocrystal feldspars have secondary rims of K-feldspar, and their cores are plagioclases.Crystallization sequences are the plagioclase core of feldspar phenocrysts, analcime and K-feldspar in the rim of feldspar phenocrysts, K-feldspar in the groundmass, salite, titanomagnetite and limonite.The balance between analcime and melt places constraints on the P/T regime (5-13) ×108 Pa and 600-640 ℃ respectively, implying depths of origin in the deep crust.
2008, 33(3): 329-336.
Abstract:
To understand the elemental occurrence phases in the new-type ferromanganese crusts from the East Philippine Sea, chemical extraction method has been utilized to analyze the occurrence phases in three crusts.The occurrence phases of metallic elements and rare earth element (REE) in different types of crusts are coherent as a whole, indicating that they were formed in similar geologic and oceanic conditions.Among the metallic elements, Fe and Cu mainly concentrate in the residual phase, while Mn, Co and Ni mainly concentrate in the manganese oxide phase, organic phase and residual phase.Besides, the manganese oxide phase of the buried crust has higher metallic element proportion.The trivalent REEs mainly concentrate in the manganese oxide phase.Ce mainly concentrates in the residual phase of two crusts on the sediment surface.While Ce mostly concentrates in the manganese oxide phase of the buried crust, which perhaps is associated with the higher Mn content in its manganese oxide phase.The REE contents in the carbonate phase and organic phase are only about 1% of the total REE respectively, which indicates that they have little impact on the enrichment of REE in the crusts.
To understand the elemental occurrence phases in the new-type ferromanganese crusts from the East Philippine Sea, chemical extraction method has been utilized to analyze the occurrence phases in three crusts.The occurrence phases of metallic elements and rare earth element (REE) in different types of crusts are coherent as a whole, indicating that they were formed in similar geologic and oceanic conditions.Among the metallic elements, Fe and Cu mainly concentrate in the residual phase, while Mn, Co and Ni mainly concentrate in the manganese oxide phase, organic phase and residual phase.Besides, the manganese oxide phase of the buried crust has higher metallic element proportion.The trivalent REEs mainly concentrate in the manganese oxide phase.Ce mainly concentrates in the residual phase of two crusts on the sediment surface.While Ce mostly concentrates in the manganese oxide phase of the buried crust, which perhaps is associated with the higher Mn content in its manganese oxide phase.The REE contents in the carbonate phase and organic phase are only about 1% of the total REE respectively, which indicates that they have little impact on the enrichment of REE in the crusts.
2008, 33(3): 337-341.
Abstract:
The analysis of fluid migration and rapid hydrocarbon accumulation is essential for exploring distribution of overpressure and probing into its generaion.Based on the RFT of many drills in Bozhong depression, the characteristics and generation of reservoir overpressure have been discussed in this paper.Three reservoir overpressure systems have been identified in the Bozhong depression: an upper reservoir overpressure in Guantao Formation-Minghuazhen Formation, a middle reservoir overpressure in Dongying Formation-Shahejie Formation-Kongdian Formation, and a lower reservoir overpressure in base (Pre-Cenozoic).Detailed investigation of reservoir overpressure in the Bozhong depression shows that overpressure probably is the result of a combination of following three mechanisms: mechanical compaction disequilibrium, overpressure transference and thermal cracking.Transfer overpressure maybe is common in subsurface reservoirs, but recognizable transfer overpressures are infrequent.A few transfer overpressures preserved in reservoirs at shallower depths named "overpressure fluid fossil", resulted from deeper overpressured fluid charging, helps us to understand the rapid petroleum accumulation in overpressured sedimentary basins.
The analysis of fluid migration and rapid hydrocarbon accumulation is essential for exploring distribution of overpressure and probing into its generaion.Based on the RFT of many drills in Bozhong depression, the characteristics and generation of reservoir overpressure have been discussed in this paper.Three reservoir overpressure systems have been identified in the Bozhong depression: an upper reservoir overpressure in Guantao Formation-Minghuazhen Formation, a middle reservoir overpressure in Dongying Formation-Shahejie Formation-Kongdian Formation, and a lower reservoir overpressure in base (Pre-Cenozoic).Detailed investigation of reservoir overpressure in the Bozhong depression shows that overpressure probably is the result of a combination of following three mechanisms: mechanical compaction disequilibrium, overpressure transference and thermal cracking.Transfer overpressure maybe is common in subsurface reservoirs, but recognizable transfer overpressures are infrequent.A few transfer overpressures preserved in reservoirs at shallower depths named "overpressure fluid fossil", resulted from deeper overpressured fluid charging, helps us to understand the rapid petroleum accumulation in overpressured sedimentary basins.
2008, 33(3): 342-348.
Abstract:
Gas source rock of K1sh, traps of volcanic rock and transport pathway of fault are three main factors that influence Xujianweizi gas reservoirs in volcanic rock.By studying the time and space matching relation of the three factors, we find that traps of volcanic rock can directly contact gas source rock of K1sh, or a distance can exist between gas source rock of K1sh and traps of volcanic rock, however, traps of volcano rock are all connected with gas source rock of K1sh by faults.The time matching relation among gas source rock of K1sh, traps of volcanic rock and faults is the best from the end of K1q to the middle of K1qn, the end of K1n and the end of K2m.It is favorable for gas to accumulate in a large scale.According to the study of relation between time and space distribution of gas reservoirs of volcanic rock, gas source rock area of K1sh, traps of best and better volcanic rock and the distribution of faults spacely controlled the distribution and formation of gas reservoirs of volcano rock.The end of K1q to the middle of K1qn, the end of K1n and the end of K2m are main accumulation periods of gas reservoirs of volcano rock in Xujiaweizi region.The good matching relation among three accumulation essential factors is the basic cause for the formation of large and medium gas fields in volcanic rock.
Gas source rock of K1sh, traps of volcanic rock and transport pathway of fault are three main factors that influence Xujianweizi gas reservoirs in volcanic rock.By studying the time and space matching relation of the three factors, we find that traps of volcanic rock can directly contact gas source rock of K1sh, or a distance can exist between gas source rock of K1sh and traps of volcanic rock, however, traps of volcano rock are all connected with gas source rock of K1sh by faults.The time matching relation among gas source rock of K1sh, traps of volcanic rock and faults is the best from the end of K1q to the middle of K1qn, the end of K1n and the end of K2m.It is favorable for gas to accumulate in a large scale.According to the study of relation between time and space distribution of gas reservoirs of volcanic rock, gas source rock area of K1sh, traps of best and better volcanic rock and the distribution of faults spacely controlled the distribution and formation of gas reservoirs of volcano rock.The end of K1q to the middle of K1qn, the end of K1n and the end of K2m are main accumulation periods of gas reservoirs of volcano rock in Xujiaweizi region.The good matching relation among three accumulation essential factors is the basic cause for the formation of large and medium gas fields in volcanic rock.
2008, 33(3): 349-356.
Abstract:
In order to understand the dynamic mechanism of formation and evolution of the Yinggehai basin, the backstripping and strain rate inversion methods are used to study the stratigraphic sections and boreholes by analyzing the relevant data.The results show a discrepancy between observed post-rift subsidence and theoretically predicted post-rift subsidence based on a multiple rift model.Our modeling results of two seismic sections show clearly that the anomalous subsidence during the post-rift stage in the northwestern part of the basin, between 300 m and 500 m, is much less than that in the middle and southeastern parts, which ranges from 900 to 1 200 m.We compare these results with those of time-dependent dynamic topography subsidence based on the global mantle flow model.The computed dynamic topography decreases by about 300 m from 20 Ma ago to the present in the northern South China Sea area.Observed anomalous subsidence within a range of less than 300 m during the post-rift stage can be interpreted as the effect of dynamic topography.However, the huge anomalous subsidence in the middle and southeastern areas may originate from a combination of the dextral strike-slip movements of marginal faults since the Late Miocene, rapid thermal subsidence after rifting and the response of dynamic topography.
In order to understand the dynamic mechanism of formation and evolution of the Yinggehai basin, the backstripping and strain rate inversion methods are used to study the stratigraphic sections and boreholes by analyzing the relevant data.The results show a discrepancy between observed post-rift subsidence and theoretically predicted post-rift subsidence based on a multiple rift model.Our modeling results of two seismic sections show clearly that the anomalous subsidence during the post-rift stage in the northwestern part of the basin, between 300 m and 500 m, is much less than that in the middle and southeastern parts, which ranges from 900 to 1 200 m.We compare these results with those of time-dependent dynamic topography subsidence based on the global mantle flow model.The computed dynamic topography decreases by about 300 m from 20 Ma ago to the present in the northern South China Sea area.Observed anomalous subsidence within a range of less than 300 m during the post-rift stage can be interpreted as the effect of dynamic topography.However, the huge anomalous subsidence in the middle and southeastern areas may originate from a combination of the dextral strike-slip movements of marginal faults since the Late Miocene, rapid thermal subsidence after rifting and the response of dynamic topography.
2008, 33(3): 357-364.
Abstract:
The Neogene strata of central beach area in the Dagang Oilfield are important for reserve exploration and strategic substitution.The main depositional system of Neogene was regarded as meandering rivers and braided rivers.However, based on the analysis of ichnofabric, microfossils, organic compounds, oxygen and carbon isotope, seismic data, as well as the experiences of petroleum exploration in the shallow strata of Bohai Bay, lacustrine environment can be recognized in the east district of central beach, which is supported by the following evidence: typical Palaeophycus ichnofabric is found, which develops particularly in the shallow lake; abundant phytoplanktonic algae fossils are discovered, which live generally in the shallow lake.Moreover, as an indicator of ancient and modern lakes' existence, lots of ostracodas such as Candona and Cypris are discovered.The type of kerogen, organic compounds, oxygen and carbon isotope, and seismic data are also the existent evidences of lacustrine environment.The paleolake expanded till its maximum during the middle and late periods of Guantao Formation and the early period of Minghuazhen Formation.
The Neogene strata of central beach area in the Dagang Oilfield are important for reserve exploration and strategic substitution.The main depositional system of Neogene was regarded as meandering rivers and braided rivers.However, based on the analysis of ichnofabric, microfossils, organic compounds, oxygen and carbon isotope, seismic data, as well as the experiences of petroleum exploration in the shallow strata of Bohai Bay, lacustrine environment can be recognized in the east district of central beach, which is supported by the following evidence: typical Palaeophycus ichnofabric is found, which develops particularly in the shallow lake; abundant phytoplanktonic algae fossils are discovered, which live generally in the shallow lake.Moreover, as an indicator of ancient and modern lakes' existence, lots of ostracodas such as Candona and Cypris are discovered.The type of kerogen, organic compounds, oxygen and carbon isotope, and seismic data are also the existent evidences of lacustrine environment.The paleolake expanded till its maximum during the middle and late periods of Guantao Formation and the early period of Minghuazhen Formation.
2008, 33(3): 365-370.
Abstract:
Founding lithologic reservoir is of greater potential as the exploration changing from the structural reservoir into the lithologic reservoir, while the reservoir analysis is the focus of the lithologic reservoir exploration.In the Liangjia area, Yitong basin, drilling shows that most of oil & gas reservoirs lie in the Sheling Formation, which belong to the fan delta facies deposited jointly by two provenances.A new method is needed to analyze this fan delta detail and its control on the reservoir because of the big space of wells in the study area.In this paper, a new analysis method and idea on the fan delta deposited jointly is presented on the basis of the interpretation of the sandstone in the impedance cube and the shape of the different layers of sandstone created on the map, then the details of fan delta are analyzed.Three major findings are as follows: (1) Fan deltas of four periods are identified in the Sheling Formation, expanding gradually in the area; (2) The fan deltas were deposited jointly by the two provenances, which controlled different layers of sandstone; (3) The application of impedance cube offers a new approach to interpret, analyze the different layers of sandstone, and to identify the fan delta facies.
Founding lithologic reservoir is of greater potential as the exploration changing from the structural reservoir into the lithologic reservoir, while the reservoir analysis is the focus of the lithologic reservoir exploration.In the Liangjia area, Yitong basin, drilling shows that most of oil & gas reservoirs lie in the Sheling Formation, which belong to the fan delta facies deposited jointly by two provenances.A new method is needed to analyze this fan delta detail and its control on the reservoir because of the big space of wells in the study area.In this paper, a new analysis method and idea on the fan delta deposited jointly is presented on the basis of the interpretation of the sandstone in the impedance cube and the shape of the different layers of sandstone created on the map, then the details of fan delta are analyzed.Three major findings are as follows: (1) Fan deltas of four periods are identified in the Sheling Formation, expanding gradually in the area; (2) The fan deltas were deposited jointly by the two provenances, which controlled different layers of sandstone; (3) The application of impedance cube offers a new approach to interpret, analyze the different layers of sandstone, and to identify the fan delta facies.
2008, 33(3): 371-376.
Abstract:
Jiyang depression, one of the most important oil-bearing basins in eastern China, has been studied with the theory and method of molecular stratigraphy.Eocene was the main period of the basin formation.The results suggest that molecular stratigraphy is helpful to determine the source of the amorphous solid organic matter which is widely dispersed in lacustrine source rocks, open out the existence and types of the microbe in paleoenviroment rebuilding, finely distinguish the organic facies, and build and consummate the sequence stratigraphy framework.Molecular stratigraphy provides a new important stratigraphical technique in petroleum geology, which may be especially valuable where methods based on paleontology failed.
Jiyang depression, one of the most important oil-bearing basins in eastern China, has been studied with the theory and method of molecular stratigraphy.Eocene was the main period of the basin formation.The results suggest that molecular stratigraphy is helpful to determine the source of the amorphous solid organic matter which is widely dispersed in lacustrine source rocks, open out the existence and types of the microbe in paleoenviroment rebuilding, finely distinguish the organic facies, and build and consummate the sequence stratigraphy framework.Molecular stratigraphy provides a new important stratigraphical technique in petroleum geology, which may be especially valuable where methods based on paleontology failed.
2008, 33(3): 377-386.
Abstract:
For discussing the geochemistry characteristics of paleokarstic products of Lower-Middle Ordovician in Tahe oilfield, and evaluating the areas influenced by different stages of paleokarst, the carbon, oxygen and strontium isotopes of karstic fissure-cave calcites have been systematically analyzed.The carbon and oxygen isotopes of different attitude calcites are characterized by meteoric water karst, and the early paleokarstic products are featured with enriched 13C and lower 87Sr/86Sr ratios.The wide ranges of δ13C and high 87Sr/86Sr ratios are the characteristics of early Herlynian paleokarst, and both have wide ranges of δ18O.The areas covered with O3s Formation are enriched with more 13C than those of north areas, indicating the increased proportion of 13C from the host rock.And another reason is the higher δ13C of early paleokastic products.Under the influence of the early Herlynian paleokarst, the strontium isotopes of different attitude calcites are heavier than the background values, indicating the join of the terrestrial strontium.The features of heavier strontium in north areas are lower than those of the areas covered with O3s Formation, indicating the increased proportion of the dissolved strontium from the wall rock.According to the regional variations of carbon, strontium isotopes and geologic background, the early Herlynian paleokarst exerted important impact on the carbonate rocks of the Lower-Middle Ordovician in the north areas and the areas covered with O3s Formation, and it is the main karst episode of Tahe oilfield and also the main formation episode of reservoir.
For discussing the geochemistry characteristics of paleokarstic products of Lower-Middle Ordovician in Tahe oilfield, and evaluating the areas influenced by different stages of paleokarst, the carbon, oxygen and strontium isotopes of karstic fissure-cave calcites have been systematically analyzed.The carbon and oxygen isotopes of different attitude calcites are characterized by meteoric water karst, and the early paleokarstic products are featured with enriched 13C and lower 87Sr/86Sr ratios.The wide ranges of δ13C and high 87Sr/86Sr ratios are the characteristics of early Herlynian paleokarst, and both have wide ranges of δ18O.The areas covered with O3s Formation are enriched with more 13C than those of north areas, indicating the increased proportion of 13C from the host rock.And another reason is the higher δ13C of early paleokastic products.Under the influence of the early Herlynian paleokarst, the strontium isotopes of different attitude calcites are heavier than the background values, indicating the join of the terrestrial strontium.The features of heavier strontium in north areas are lower than those of the areas covered with O3s Formation, indicating the increased proportion of the dissolved strontium from the wall rock.According to the regional variations of carbon, strontium isotopes and geologic background, the early Herlynian paleokarst exerted important impact on the carbonate rocks of the Lower-Middle Ordovician in the north areas and the areas covered with O3s Formation, and it is the main karst episode of Tahe oilfield and also the main formation episode of reservoir.
2008, 33(3): 387-392.
Abstract:
The array acoustic logging information extraction had been focused on processing the velocities and attenuations of the primary wave, shear wave and stoneley wave, and people have not still paid enough attention to the analysis on the frequency characteristics of waveform.In order to make up for this defect, the time-frequency analysis method of Hilbert-Huang transform (HHT) and the conception of transient frequency were introduced, and the empirical mode decomposition (EMD) and its time-frequency distribution about digital array acoustic logging waveform signals were given.This method was provided with the abilities to distinguish and identify the different kinds of structural fracture zones responses.The application of Hilbert-Huang transform on array acoustic logging waveform yields ideal results.Therefore, in terms of signal processing and geophysics theory, the intrinsic mode function (IMF) reflected properly the intrinsic physical properties in waveform and the method of EMD was effective and feasible.All these researches have contributed a lot to confirming the HHT in array acoustic logging waveform processing by providing effective and feasible methods.
The array acoustic logging information extraction had been focused on processing the velocities and attenuations of the primary wave, shear wave and stoneley wave, and people have not still paid enough attention to the analysis on the frequency characteristics of waveform.In order to make up for this defect, the time-frequency analysis method of Hilbert-Huang transform (HHT) and the conception of transient frequency were introduced, and the empirical mode decomposition (EMD) and its time-frequency distribution about digital array acoustic logging waveform signals were given.This method was provided with the abilities to distinguish and identify the different kinds of structural fracture zones responses.The application of Hilbert-Huang transform on array acoustic logging waveform yields ideal results.Therefore, in terms of signal processing and geophysics theory, the intrinsic mode function (IMF) reflected properly the intrinsic physical properties in waveform and the method of EMD was effective and feasible.All these researches have contributed a lot to confirming the HHT in array acoustic logging waveform processing by providing effective and feasible methods.
2008, 33(3): 393-398.
Abstract:
According to the displacement-time sequence data of several slopes, the multivariable chaotic features of slope evaluation process are discussed, including reconstruction for their phase-space by the estimation of delayed time and embedded dimension method, calculation for the correlation dimension D2 of the slope system by eliminating the time correlative points.Then, the multivariable chaotic features of the slopes are studied by calculating their maximum Lyapunov index using the improved Kantz method and taking K2 as the similar one of Kolmogorov entropy, and by introducing the approximation entropy-ApEn and the chaotic feature index describing the complexity degree of the system.Example analysis shows that the correlation dimension D2 is a non-integral number for most of slope systems, the maximum Lyapunov index and the entropy value are all bigger than 0, and the complexity degree of the system is located on the interval of (0, 1).By comparing the calculated data with the actual characteristic value of the slope systems, the chaotic features of the slope system are revealed and the chaotic features are clearer in the time period closed to sliding.
According to the displacement-time sequence data of several slopes, the multivariable chaotic features of slope evaluation process are discussed, including reconstruction for their phase-space by the estimation of delayed time and embedded dimension method, calculation for the correlation dimension D2 of the slope system by eliminating the time correlative points.Then, the multivariable chaotic features of the slopes are studied by calculating their maximum Lyapunov index using the improved Kantz method and taking K2 as the similar one of Kolmogorov entropy, and by introducing the approximation entropy-ApEn and the chaotic feature index describing the complexity degree of the system.Example analysis shows that the correlation dimension D2 is a non-integral number for most of slope systems, the maximum Lyapunov index and the entropy value are all bigger than 0, and the complexity degree of the system is located on the interval of (0, 1).By comparing the calculated data with the actual characteristic value of the slope systems, the chaotic features of the slope system are revealed and the chaotic features are clearer in the time period closed to sliding.
2008, 33(3): 399-404.
Abstract:
To understand the interactions between dissolved organic matter (DOM) and environmental endocrine disruptors (EEDs) in landfill leachate, sorption experiments and the interaction between targets EEDs, including BPA, E2, E1, and DOM from leachate were investigated.It was found that adsorption isotherms fit the Freundlich equation well.The regression equation between binding coefficient, Kf, and the logarithm value of Kow or Kdoc of compounds was determined (R2=0.995 8, P=0.041 < 0.05).Both the unreacted DOM and the DOM that reacted with EEDs were analyzed by FTIR, 1HNMR and ESR.The results suggested that multiple binding mechanisms might occur simultaneously in the adsorption process with the formation of (1) ionic bonds (proton-transfer) between carboxylate groups of DOM and positively charged compounds; (2) hydrogen bonds between structure moieties of EEDs and DOM; and (3) charge-transfer bonds in electron donor-acceptor processes.
To understand the interactions between dissolved organic matter (DOM) and environmental endocrine disruptors (EEDs) in landfill leachate, sorption experiments and the interaction between targets EEDs, including BPA, E2, E1, and DOM from leachate were investigated.It was found that adsorption isotherms fit the Freundlich equation well.The regression equation between binding coefficient, Kf, and the logarithm value of Kow or Kdoc of compounds was determined (R2=0.995 8, P=0.041 < 0.05).Both the unreacted DOM and the DOM that reacted with EEDs were analyzed by FTIR, 1HNMR and ESR.The results suggested that multiple binding mechanisms might occur simultaneously in the adsorption process with the formation of (1) ionic bonds (proton-transfer) between carboxylate groups of DOM and positively charged compounds; (2) hydrogen bonds between structure moieties of EEDs and DOM; and (3) charge-transfer bonds in electron donor-acceptor processes.
2008, 33(3): 405-410.
Abstract:
Carbonic clay was discovered on the banks of Yangtze River during geological engineering investigations in the new towns of Wushan, Fengjie and Yunyang counties in the Three Gorges reservoir area, Yangtze River, China.The age of the carbonic clay was estimated by 14C dating.The results indicate that there is a considerable discrepancy in the age of the carbonic clay and the age of the terrace, located at the same altitude.The carbonic clay proves to represent sediment from an abnormal environment.The discovery of the abnormal carbonic clay indicates that the formation and evolution of the slope along the Yangtze River, in immigrant settlement regions (such as Wushan), is abnormal.It also shows that there were outbreaks of geological hazards in the evolutionary history of the Yangtze River valley in the Three Gorges reservoir area.
Carbonic clay was discovered on the banks of Yangtze River during geological engineering investigations in the new towns of Wushan, Fengjie and Yunyang counties in the Three Gorges reservoir area, Yangtze River, China.The age of the carbonic clay was estimated by 14C dating.The results indicate that there is a considerable discrepancy in the age of the carbonic clay and the age of the terrace, located at the same altitude.The carbonic clay proves to represent sediment from an abnormal environment.The discovery of the abnormal carbonic clay indicates that the formation and evolution of the slope along the Yangtze River, in immigrant settlement regions (such as Wushan), is abnormal.It also shows that there were outbreaks of geological hazards in the evolutionary history of the Yangtze River valley in the Three Gorges reservoir area.
2008, 33(3): 411-415.
Abstract:
Badong landslide is one of the most serious landslides in the Three Gorges Reservoir Area for its large scale and complex formation and deformation processes.It was formed as a result of intense tectonic uplift of the Three Gorges Reservoir Area, rapid cut-down of the river and slope unloading.The deep creep deformation of No.1 collapse deposits under backwater conditions is obviously observed and has been paid special attention to.By the geological process analogy and analysis, we analyze the formation of slopes, deformation and destruction process, the mechanism of geological processes of formation and deformation under backwater conditions.We predict the trend that slide may happen in the front and middle part of the collapse deposits on a large scale, and it finds that deep creep distortion of No.1 collapse deposits is mainly caused by the coupling of reservoir water and rain water.
Badong landslide is one of the most serious landslides in the Three Gorges Reservoir Area for its large scale and complex formation and deformation processes.It was formed as a result of intense tectonic uplift of the Three Gorges Reservoir Area, rapid cut-down of the river and slope unloading.The deep creep deformation of No.1 collapse deposits under backwater conditions is obviously observed and has been paid special attention to.By the geological process analogy and analysis, we analyze the formation of slopes, deformation and destruction process, the mechanism of geological processes of formation and deformation under backwater conditions.We predict the trend that slide may happen in the front and middle part of the collapse deposits on a large scale, and it finds that deep creep distortion of No.1 collapse deposits is mainly caused by the coupling of reservoir water and rain water.
2008, 33(3): 416-422.
Abstract:
The study of the apatite pseudomorphic turquoise's thermal property plays a significant role in the investigation of the coloring mechanism and the structural characteristics of water in turquoise.In this paper, thermal property of the apatite pseudomorphic turquoise from Maanshan, Anhui Province, has been studied by using the thermogravimetric and thermal analysis (TG-DSC), infrared (IR) spectrum and X-ray powder (XRD) diffraction.From room temperature to 1 100 ℃, its thermal phase transformation can be divided into six stages: 100-200 ℃, the removal of the absorption water; 250-330 ℃, the release of the hydroxyl and lattice water; 330-750 ℃, the formation of non-crystalline structure; about 750 ℃, a new phase formed; 750-1 100 ℃, the generation of aluminum phosphate with tridymite structure, and 1 100 ℃, the degree of crystalline order of aluminum phosphate is improved.The color of pseudomorphic turquoise is controlled by the structure, the existence form and total amount of water, together with the binding mode of water molecules.
The study of the apatite pseudomorphic turquoise's thermal property plays a significant role in the investigation of the coloring mechanism and the structural characteristics of water in turquoise.In this paper, thermal property of the apatite pseudomorphic turquoise from Maanshan, Anhui Province, has been studied by using the thermogravimetric and thermal analysis (TG-DSC), infrared (IR) spectrum and X-ray powder (XRD) diffraction.From room temperature to 1 100 ℃, its thermal phase transformation can be divided into six stages: 100-200 ℃, the removal of the absorption water; 250-330 ℃, the release of the hydroxyl and lattice water; 330-750 ℃, the formation of non-crystalline structure; about 750 ℃, a new phase formed; 750-1 100 ℃, the generation of aluminum phosphate with tridymite structure, and 1 100 ℃, the degree of crystalline order of aluminum phosphate is improved.The color of pseudomorphic turquoise is controlled by the structure, the existence form and total amount of water, together with the binding mode of water molecules.
2008, 33(3): 423-430.
Abstract:
How to efficiently manage and reuse the existeing geoscience data of eastern China is an urgent problem.Based on the geochemical data model, we established the East China geochemical science database (ECGD) that applied the relational database and WebGIS technology.Using the ECGD, researchers can query, analyze, output and implement spatial visualization to the geochemical data via a website.Because integration of WebGIS technology, the query results can be mapped on digital map based on WebGIS and can generate classification thematic maps.Meanwhile, researchers can make online analysis of the query results using offered geochemical diagram.ECGD is the first web-based geochemical science database that integrated the functions of data retrieval, spatial visualization and online analysis, and it provides a geochemical data sharing, access and exchange collaboration platform for researchers.
How to efficiently manage and reuse the existeing geoscience data of eastern China is an urgent problem.Based on the geochemical data model, we established the East China geochemical science database (ECGD) that applied the relational database and WebGIS technology.Using the ECGD, researchers can query, analyze, output and implement spatial visualization to the geochemical data via a website.Because integration of WebGIS technology, the query results can be mapped on digital map based on WebGIS and can generate classification thematic maps.Meanwhile, researchers can make online analysis of the query results using offered geochemical diagram.ECGD is the first web-based geochemical science database that integrated the functions of data retrieval, spatial visualization and online analysis, and it provides a geochemical data sharing, access and exchange collaboration platform for researchers.
