2011 Vol. 36, No. 3
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2011, 36(3): 393-408.
doi: 10.3799/dqkx.2011.044
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Abstract:
Tethys Ocean formation and evolvement poses one of the important foundamental geological issues in studies concerning the Tibetan Plateau Integrating the field work, data analysis, previous studies, and particularly with the 1∶250 000 regional geology data, in Bayankala tectonic belt during Permian-Trias, including the normal stratum, lithofacies character and tectonic-paleogeography, we discussed the tectonic evolvement in order to improve the research level of the Tethys ocean development in Tibetan Plateau and Rodinia continent formation. The Permian-Neogene's stratum appears in the main body of Bayankala tectonic belt, characterized by disappearing portion of Trias stratum before Permian. Permian-Trias stratum was continuously aggraded in ocean environment. Bayankala Group is distributed widely and formatting thick in Trias in continent and ocean environment being flysch and little volcanic sediment. Jurassic-Quaternary aggraded in continent formatting river and lake environment. Huangyangling Group aggraded in shallow and deep ocean environment formatting carbonate and fragmentary rock. It evolved from ocean environment to continent environment during Permian-Trias after collision, orogenesis and the blue water vanish, as the north part of main double ocean region contrasting with the south Longmu lake-Shuanghu ocean of Palaeo Tethys ocean lying between Talimu-China-Korea plate and south big continent (Gangwana continent).
Tethys Ocean formation and evolvement poses one of the important foundamental geological issues in studies concerning the Tibetan Plateau Integrating the field work, data analysis, previous studies, and particularly with the 1∶250 000 regional geology data, in Bayankala tectonic belt during Permian-Trias, including the normal stratum, lithofacies character and tectonic-paleogeography, we discussed the tectonic evolvement in order to improve the research level of the Tethys ocean development in Tibetan Plateau and Rodinia continent formation. The Permian-Neogene's stratum appears in the main body of Bayankala tectonic belt, characterized by disappearing portion of Trias stratum before Permian. Permian-Trias stratum was continuously aggraded in ocean environment. Bayankala Group is distributed widely and formatting thick in Trias in continent and ocean environment being flysch and little volcanic sediment. Jurassic-Quaternary aggraded in continent formatting river and lake environment. Huangyangling Group aggraded in shallow and deep ocean environment formatting carbonate and fragmentary rock. It evolved from ocean environment to continent environment during Permian-Trias after collision, orogenesis and the blue water vanish, as the north part of main double ocean region contrasting with the south Longmu lake-Shuanghu ocean of Palaeo Tethys ocean lying between Talimu-China-Korea plate and south big continent (Gangwana continent).
2011, 36(3): 409-428.
doi: 10.3799/dqkx.2011.045
Abstract:
The research on cyclostratigraphy has made great progress over the past 30 years, and it has contributed to the understanding and solutions of numerous scientific problems in the field of Earth Science. Now cyclostratigraphy has been defined as "the subdiscipline of stratigraphy that deals with the identification, characterization, correlation, and interpretation of cyclic variations in the stratigraphic record and, in particular, with their application in geochronology by improving the accuracy and resolution of time-stratigraphic frameworks". The lithological, facies, geophysical and geochemical parameters (i.e., paleoclimate proxies), which can reflect paleoclimate fluctuations, have been adopted extensively in the cyclostratigraphy analysis. A set of methods, including characterization of lithological combination, power spectral analysis, evolutive power spectral analysis, wavelet analysis, filtering and tuning, have been developed to identify the Milankovitch cycles and establish high-resolution astronomical time scales. Some excellent cyclostratigraphy results have been obtained from loess deposits of northern China, Neogene marine deposits in South China Sea, Paleozoic marine sections, and some Meso-Neozoic terrestrial basins by Chinese scholars. We may get some important results if we can carry out cyclostratigraphy research on the Cretaceous terrestrial deposits in Songliao basin, northeastern China, and Lopingian-Midddle Triassic marine sections in South China.
The research on cyclostratigraphy has made great progress over the past 30 years, and it has contributed to the understanding and solutions of numerous scientific problems in the field of Earth Science. Now cyclostratigraphy has been defined as "the subdiscipline of stratigraphy that deals with the identification, characterization, correlation, and interpretation of cyclic variations in the stratigraphic record and, in particular, with their application in geochronology by improving the accuracy and resolution of time-stratigraphic frameworks". The lithological, facies, geophysical and geochemical parameters (i.e., paleoclimate proxies), which can reflect paleoclimate fluctuations, have been adopted extensively in the cyclostratigraphy analysis. A set of methods, including characterization of lithological combination, power spectral analysis, evolutive power spectral analysis, wavelet analysis, filtering and tuning, have been developed to identify the Milankovitch cycles and establish high-resolution astronomical time scales. Some excellent cyclostratigraphy results have been obtained from loess deposits of northern China, Neogene marine deposits in South China Sea, Paleozoic marine sections, and some Meso-Neozoic terrestrial basins by Chinese scholars. We may get some important results if we can carry out cyclostratigraphy research on the Cretaceous terrestrial deposits in Songliao basin, northeastern China, and Lopingian-Midddle Triassic marine sections in South China.
2011, 36(3): 429-439.
doi: 10.3799/dqkx.2011.046
Abstract:
The study of the geochemistry of the Late Cretaceous rhyolites of Daxingzhuang Formation in Yixian area, western Liaoning Province, shows that these rocks demonstrate characteristics of adakitic rocks with SiO2≥68.62%, Al2O3≥14.40%, MgO < 1.2% (Mg# < 0.45), Sr > 360μg/g, Yb < 1.1μg/g, Y < 12μg/g, La/Yb > 40, Sr/Y≥39, Nb/Ta > 17.5 and with δEu weak negative anomaly, LREE enrichment, HREE depletion, HFSEs (Nb, Ta, Ti) strong depletion, lower 143Nd/144Nd ratios (0.511376 to 0.511441, -23.45 to -22.16 in εNd (t)), moderate 87Sr/86Sr ratios (0.7073 to 0.7074, 32.38 to 32.8 in εSr(t)) which have the features of the enriched mantle EMI. The above geochemical features of the rhyolites indicate the magmas originated from the partial melting of eclogite of the lower thicken basaltic crust of the North China craton and perhaps also represent the thicken crust still existed in partial area of Yanshan orogenic belt. It falicitates the understanding of the processes of the lithosphere thinning of the North China craton during the Mesozoic and Cenozoic period.
The study of the geochemistry of the Late Cretaceous rhyolites of Daxingzhuang Formation in Yixian area, western Liaoning Province, shows that these rocks demonstrate characteristics of adakitic rocks with SiO2≥68.62%, Al2O3≥14.40%, MgO < 1.2% (Mg# < 0.45), Sr > 360μg/g, Yb < 1.1μg/g, Y < 12μg/g, La/Yb > 40, Sr/Y≥39, Nb/Ta > 17.5 and with δEu weak negative anomaly, LREE enrichment, HREE depletion, HFSEs (Nb, Ta, Ti) strong depletion, lower 143Nd/144Nd ratios (0.511376 to 0.511441, -23.45 to -22.16 in εNd (t)), moderate 87Sr/86Sr ratios (0.7073 to 0.7074, 32.38 to 32.8 in εSr(t)) which have the features of the enriched mantle EMI. The above geochemical features of the rhyolites indicate the magmas originated from the partial melting of eclogite of the lower thicken basaltic crust of the North China craton and perhaps also represent the thicken crust still existed in partial area of Yanshan orogenic belt. It falicitates the understanding of the processes of the lithosphere thinning of the North China craton during the Mesozoic and Cenozoic period.
2011, 36(3): 440-454.
doi: 10.3799/dqkx.2011.047
Abstract:
Ningxiang-type iron deposits are widely distributed in Devonian strata in southern China with huge reserves, but exploitation of this type iron deposits have been severely circumscribed due to their high phosphorus content. Occurrences of phosphorus are theoretical foundations for dephosphorization researches, which should be solved first. Preliminary researches of occurrence, formation and origin of phosphorus in Late Devonian phosphate-bearing ooidal ironstones from Western Hubei in China have been done in this study by means of whole-rock element analysis (wet chemical whole-rock analysis, inductively coupled plasma mass spectrometry), mineral phase analysis (scanning electron microscopy, X-ray diffraction analysis) and in-situ element analysis (electron microprobe analysis, laser ablation inductively coupled plasma mass spectrometry). Phosphorous-bearing minerals are mainly carbonate fluorapatite in ironstone and there are three formations, including prismatic apatite crystal particles (more than 65% particle sizes < 20 μm), apatite intraclasts (very coarse and coarse sand size level particles concentrate in lenticular and banded beddings), and layered gelatinous apatite entangled by hematite in ooids (layer thickness are of 10-50 μm). Apatite crystals recrystallized from pore water, and might have originated from phosphorite in late Sinian strata. Apatite intraclasts were the product of in-situ chemical deposition in seawater, and might have come from land around paleo-ocean. Gelatinous apatite also was in-situ chemical deposition product, but formed at iron deposition position and mixed or mutual parcel with chamosite and formed ooids.
Ningxiang-type iron deposits are widely distributed in Devonian strata in southern China with huge reserves, but exploitation of this type iron deposits have been severely circumscribed due to their high phosphorus content. Occurrences of phosphorus are theoretical foundations for dephosphorization researches, which should be solved first. Preliminary researches of occurrence, formation and origin of phosphorus in Late Devonian phosphate-bearing ooidal ironstones from Western Hubei in China have been done in this study by means of whole-rock element analysis (wet chemical whole-rock analysis, inductively coupled plasma mass spectrometry), mineral phase analysis (scanning electron microscopy, X-ray diffraction analysis) and in-situ element analysis (electron microprobe analysis, laser ablation inductively coupled plasma mass spectrometry). Phosphorous-bearing minerals are mainly carbonate fluorapatite in ironstone and there are three formations, including prismatic apatite crystal particles (more than 65% particle sizes < 20 μm), apatite intraclasts (very coarse and coarse sand size level particles concentrate in lenticular and banded beddings), and layered gelatinous apatite entangled by hematite in ooids (layer thickness are of 10-50 μm). Apatite crystals recrystallized from pore water, and might have originated from phosphorite in late Sinian strata. Apatite intraclasts were the product of in-situ chemical deposition in seawater, and might have come from land around paleo-ocean. Gelatinous apatite also was in-situ chemical deposition product, but formed at iron deposition position and mixed or mutual parcel with chamosite and formed ooids.
2011, 36(3): 455-470.
doi: 10.3799/dqkx.2011.048
Abstract:
Based on analysis of petrological and geochemical information of igneous rocks sampled from central sub-basin of the South China Sea, this article attempts to address the magmatic processes and tectonic background of the research area. By renewing the available datas and combining them with latest test results of igneous rock samples collected from 6 seamount chains in the central sub-basin of South China Sea (SCS), we analyze the alkali basalt, transitional tholeiite, trachyte, trachyandesite and rhyodacite under a unified magmatic differentiation system in this paper. The geochemical indices show that the evolutionary relationship of these igneous rocks was relatively consistent and the regional mantle source was heterogeneous, consisting of two end-members: EMⅠ and DMM. According to the Mg#, differentiation index (DI), attributes of major and minor elements, we conclude that subsequent to the fractional crystallization of olivine and pyroxene in upper mantle, the primitive magma continues its evolution to bring about this rock association. Furthermore, geological datas also indicate that during the process of magma evolving, different degrees of contamination occurred in different stages of sea-floor expansion, which may be one of the most important heritage left by the rupture of passive continental margin.
Based on analysis of petrological and geochemical information of igneous rocks sampled from central sub-basin of the South China Sea, this article attempts to address the magmatic processes and tectonic background of the research area. By renewing the available datas and combining them with latest test results of igneous rock samples collected from 6 seamount chains in the central sub-basin of South China Sea (SCS), we analyze the alkali basalt, transitional tholeiite, trachyte, trachyandesite and rhyodacite under a unified magmatic differentiation system in this paper. The geochemical indices show that the evolutionary relationship of these igneous rocks was relatively consistent and the regional mantle source was heterogeneous, consisting of two end-members: EMⅠ and DMM. According to the Mg#, differentiation index (DI), attributes of major and minor elements, we conclude that subsequent to the fractional crystallization of olivine and pyroxene in upper mantle, the primitive magma continues its evolution to bring about this rock association. Furthermore, geological datas also indicate that during the process of magma evolving, different degrees of contamination occurred in different stages of sea-floor expansion, which may be one of the most important heritage left by the rupture of passive continental margin.
2011, 36(3): 471-482.
doi: 10.3799/dqkx.2011.049
Abstract:
This paper reports zircon U-Pb geochronology, Hf isotope, and whole-rock geochemical data, aimed at constraining the petrogenesis of the hornblende (Hb)-gabbros from the Xi'anli intrusion in the southern Taihang Mountains (Mts.). The intrusion is composed mainly of olivine-bearing Hb-gabbro, Hb-diorite, and diorite. Zircons from the Hb-gabbros display euhedral shape and zonal homogeneous absorption on CL images, and have high Th/U ratio (1.44-2.85), suggesting a magmatic origin. Their 206Pb/238U ages range from 135 to 127 Ma, yielding a mean age of 131±1 Ma (MSWD=6.5, n=15), which suggests that the Xi'anli Hb-gabbros were formed in the Early Cretaceous. The εHf(t) values of selected zircons range from -23.5 to -19.2. The Xi'anli Hb-gabbros have SiO2 = 50.27%-50.89%, Mg# =0.76-0.78, and Na2O/K2O= 2.18-2.37, and are enriched in transitional elements such as Sc (19.2-20.3)×10-6, Cr (939-1 050)×10-6, Co (54.6-58.2)×10-6, and Ni (645-718)×10-6. Moreover, these gabbros are characterized by relative enrichment in large ion lithophile elements (LILEs, such as Cs, Ba, Sr) and light rare earth elements (LREEs), and intensive depletion in high field strength elements (HFSEs, such as Nb, Ta, Zr, Hf) and heavy rare earth elements (HREEs). Combined with the mineralogical and geochemical study of the dunite xenolith and the olivine xenocrysts hosted in the Hb-gabbros, we propose that the Xi'anli Hb-gabbros may have been produced by the reaction of the delaminated lower continental crust-derived melt and mantle peridotite.
This paper reports zircon U-Pb geochronology, Hf isotope, and whole-rock geochemical data, aimed at constraining the petrogenesis of the hornblende (Hb)-gabbros from the Xi'anli intrusion in the southern Taihang Mountains (Mts.). The intrusion is composed mainly of olivine-bearing Hb-gabbro, Hb-diorite, and diorite. Zircons from the Hb-gabbros display euhedral shape and zonal homogeneous absorption on CL images, and have high Th/U ratio (1.44-2.85), suggesting a magmatic origin. Their 206Pb/238U ages range from 135 to 127 Ma, yielding a mean age of 131±1 Ma (MSWD=6.5, n=15), which suggests that the Xi'anli Hb-gabbros were formed in the Early Cretaceous. The εHf(t) values of selected zircons range from -23.5 to -19.2. The Xi'anli Hb-gabbros have SiO2 = 50.27%-50.89%, Mg# =0.76-0.78, and Na2O/K2O= 2.18-2.37, and are enriched in transitional elements such as Sc (19.2-20.3)×10-6, Cr (939-1 050)×10-6, Co (54.6-58.2)×10-6, and Ni (645-718)×10-6. Moreover, these gabbros are characterized by relative enrichment in large ion lithophile elements (LILEs, such as Cs, Ba, Sr) and light rare earth elements (LREEs), and intensive depletion in high field strength elements (HFSEs, such as Nb, Ta, Zr, Hf) and heavy rare earth elements (HREEs). Combined with the mineralogical and geochemical study of the dunite xenolith and the olivine xenocrysts hosted in the Hb-gabbros, we propose that the Xi'anli Hb-gabbros may have been produced by the reaction of the delaminated lower continental crust-derived melt and mantle peridotite.
2011, 36(3): 483-499.
doi: 10.3799/dqkx.2011.050
Abstract:
Detrial zircon from clastic sediment or sands of modern rivers is an ideal sample for studying the growth and evolution of the continental crust. In order to reveal the crustal growth of eastern North China craton and Sulu orogen, 396 concordant detrital zircons in three sand samples from the Daqing River, Chaobai River, Liao River, Dagu River and Jiaolai River in eastern North China were measured for U-Pb age and Hf isotopic compositions by excimer laser-ablation ICP-MS and MC-ICP-MS, respectively. The Daqing River, Chaobai River and Liao River are characterized by two age peaks of 2.4-2.5 Ga and 1.8-1.9 Ga, which indicate contributions from the eastern North China craton. Some 100-500 Ma zircons from the Liao River with positive εHf(t) values and young Hf model ages, suggesting Phanerozoic crustal growth. In contrast, U-Pb ages of the Dagu River and Jiaolai River, which run through the Sulu orogen, are more complicated and characterized by age groups of 2.4-2.5 Ga, 1.8-1.9 Ga and 700-800 Ma, implying a mixed provenance of eastern North China craton and Yangtze craton. The Lu-Hf isotope compositions of the Daqing River, Chaobai River and Liao River demonstrate the dominant growth at 2.4-3.0 Ga, with a peak at 2.6-2.7 Ga and minor growth during 1.3-2.3 Ga. However, there is insignificant crustal growth during other periods. In addition, 80% of the existing crust in eastern North China craton was produced before Paleoproterozoic and reworking of preexisting continental crust became dominant since then. Meanwhile, a Paleozoic (300-500 Ma) crustal growth characterizes zircon Hf isotopes of the Dagu River of the Sulu orogen.
Detrial zircon from clastic sediment or sands of modern rivers is an ideal sample for studying the growth and evolution of the continental crust. In order to reveal the crustal growth of eastern North China craton and Sulu orogen, 396 concordant detrital zircons in three sand samples from the Daqing River, Chaobai River, Liao River, Dagu River and Jiaolai River in eastern North China were measured for U-Pb age and Hf isotopic compositions by excimer laser-ablation ICP-MS and MC-ICP-MS, respectively. The Daqing River, Chaobai River and Liao River are characterized by two age peaks of 2.4-2.5 Ga and 1.8-1.9 Ga, which indicate contributions from the eastern North China craton. Some 100-500 Ma zircons from the Liao River with positive εHf(t) values and young Hf model ages, suggesting Phanerozoic crustal growth. In contrast, U-Pb ages of the Dagu River and Jiaolai River, which run through the Sulu orogen, are more complicated and characterized by age groups of 2.4-2.5 Ga, 1.8-1.9 Ga and 700-800 Ma, implying a mixed provenance of eastern North China craton and Yangtze craton. The Lu-Hf isotope compositions of the Daqing River, Chaobai River and Liao River demonstrate the dominant growth at 2.4-3.0 Ga, with a peak at 2.6-2.7 Ga and minor growth during 1.3-2.3 Ga. However, there is insignificant crustal growth during other periods. In addition, 80% of the existing crust in eastern North China craton was produced before Paleoproterozoic and reworking of preexisting continental crust became dominant since then. Meanwhile, a Paleozoic (300-500 Ma) crustal growth characterizes zircon Hf isotopes of the Dagu River of the Sulu orogen.
2011, 36(3): 500-510.
doi: 10.3799/dqkx.2011.051
Abstract:
Early Lower Triassic plants are little known in China, especially in South China. This paper presents the paleofloral assemblage from the top of Xuanwei and the lower of the Kayitou Formations in western Guizhou and eastern Yunnan, China. Fossil plants in this area (Annularia shirakii, Lobatannularia sp., Paracalamites stenocostatus, Gigantopteris sp., Pecopteris sp., which are all the Permian relicts) from the bottom of the Kayitou Formation described by other people in 1970s are covered. In addition, many important new fossil plants in the evolution during the Permian-Triassic interval, such as Isoetes Annalepis (including A. zeilleri, A. brevicystis), Peltaspermacae Peltaspermum (including P. martinsii, P. lobutalum, P. sp.), Lepidodendron and Stigmaria and so on are also reported. Both the new type and the "Gigantopteris-flora" relicts are characterized with the Early Triassic Induan paleofloral features in South China. This paleofloral assemblage contains 31 species in 14 genera. These fossil plants are in association with an early Lower Triassic marine fauna (Bivalves, Ostracods, Brachiopods and Ammonites). So the geological age of this paleoflora is Early Triassic Induan stage, while the FAD of Annalepis is regarded as the marker, representing the beginning of Triassic. Based on analyzing paleoflora and limnology of the top of Xuanwei and the lower of Kayitou Formations, it is concluded that tropical and humid conditions persisted in western Guizhou and eastern Yunnan throughout the Permian and Earliest Triassic.
Early Lower Triassic plants are little known in China, especially in South China. This paper presents the paleofloral assemblage from the top of Xuanwei and the lower of the Kayitou Formations in western Guizhou and eastern Yunnan, China. Fossil plants in this area (Annularia shirakii, Lobatannularia sp., Paracalamites stenocostatus, Gigantopteris sp., Pecopteris sp., which are all the Permian relicts) from the bottom of the Kayitou Formation described by other people in 1970s are covered. In addition, many important new fossil plants in the evolution during the Permian-Triassic interval, such as Isoetes Annalepis (including A. zeilleri, A. brevicystis), Peltaspermacae Peltaspermum (including P. martinsii, P. lobutalum, P. sp.), Lepidodendron and Stigmaria and so on are also reported. Both the new type and the "Gigantopteris-flora" relicts are characterized with the Early Triassic Induan paleofloral features in South China. This paleofloral assemblage contains 31 species in 14 genera. These fossil plants are in association with an early Lower Triassic marine fauna (Bivalves, Ostracods, Brachiopods and Ammonites). So the geological age of this paleoflora is Early Triassic Induan stage, while the FAD of Annalepis is regarded as the marker, representing the beginning of Triassic. Based on analyzing paleoflora and limnology of the top of Xuanwei and the lower of Kayitou Formations, it is concluded that tropical and humid conditions persisted in western Guizhou and eastern Yunnan throughout the Permian and Earliest Triassic.
2011, 36(3): 511-520.
doi: 10.3799/dqkx.2011.052
Abstract:
The fluid-rock interactions and fluid circulations in subduction zone have been a focus for geologists. As a kind of high-grade gem material, the genesis of jadeite rocks attracts an increasing concern. The jadeite rocks generally occur in the serpentinized ultramafic rocks in subduction zones and its formation is related to the interaction between subduction-related fluids and ultramafic rocks (peridotite). Based on rock association, petrography, microstructure and mineral chemical characteristics, the processes of interaction between peridotite and fluid can be divided into five stages, that is, serpentine→ (chlorite, phlogopite) →amphibole→pyroxene→ (analcime, albite). Combined with analysis of thermodynamic phase diagrams, the evolutionary series of minerals in the processes of interaction are identified. Formation of jadeite requires the fluids enrich in Na, Al, Si and under relatively higher pressure. In the jadeite rocks from Myanmar, the sodium amphiboles with various chemical components are always associated with the jadeite, and rebalance of the amphiboles with fluids can regulate the compositions of minerals and fluids. Sodium amphiboles act as a buffer in the formation process of jade and the jadeite was crystallized when the Na, Al and Si were concentrated to certain percentage.
The fluid-rock interactions and fluid circulations in subduction zone have been a focus for geologists. As a kind of high-grade gem material, the genesis of jadeite rocks attracts an increasing concern. The jadeite rocks generally occur in the serpentinized ultramafic rocks in subduction zones and its formation is related to the interaction between subduction-related fluids and ultramafic rocks (peridotite). Based on rock association, petrography, microstructure and mineral chemical characteristics, the processes of interaction between peridotite and fluid can be divided into five stages, that is, serpentine→ (chlorite, phlogopite) →amphibole→pyroxene→ (analcime, albite). Combined with analysis of thermodynamic phase diagrams, the evolutionary series of minerals in the processes of interaction are identified. Formation of jadeite requires the fluids enrich in Na, Al, Si and under relatively higher pressure. In the jadeite rocks from Myanmar, the sodium amphiboles with various chemical components are always associated with the jadeite, and rebalance of the amphiboles with fluids can regulate the compositions of minerals and fluids. Sodium amphiboles act as a buffer in the formation process of jade and the jadeite was crystallized when the Na, Al and Si were concentrated to certain percentage.
2011, 36(3): 521-529.
doi: 10.3799/dqkx.2011.053
Abstract:
The former understanding about actual hydrocarbon migration paths is mainly based on the micro-scale physical simulation or the computer simulation, and the actual oil and gas migration paths only rely on indirect evidence. This paper takes Puwei area of Dongpu depression as an example, firstly we find out the dominated migration pathways of main sandbodies and faults, then analyze their relationships with hydrocarbon kitchens and reservoirs to evaluate their effectiveness, and lastly identify the paths of hydrocarbon migration by combining the tracking of nitrogen compounds indicators. The results show that ridge-like structures analysis combined with geochemical indicators tracking can identify actual hydrocarbon migration paths accurately. Ridge-like structures of sandbody top and fault plane are the dominated migration pathways, their ability to become actual migration paths, as well as the amount of hydrocarbon carried depend on the oil and gas volume supplied by hydrocarbon kitchens. In Puwei area, oil and gas mainly migrated vertically along ridge-like structures of fault plane, followed by lateral migration along ridge-like structures of sandbody top in Puwei sag and Pucheng right-wing slope. Nitrogen compounds indicators tracking shows that the majority of ridge-like structures in this area are actual oil and gas migration paths.
The former understanding about actual hydrocarbon migration paths is mainly based on the micro-scale physical simulation or the computer simulation, and the actual oil and gas migration paths only rely on indirect evidence. This paper takes Puwei area of Dongpu depression as an example, firstly we find out the dominated migration pathways of main sandbodies and faults, then analyze their relationships with hydrocarbon kitchens and reservoirs to evaluate their effectiveness, and lastly identify the paths of hydrocarbon migration by combining the tracking of nitrogen compounds indicators. The results show that ridge-like structures analysis combined with geochemical indicators tracking can identify actual hydrocarbon migration paths accurately. Ridge-like structures of sandbody top and fault plane are the dominated migration pathways, their ability to become actual migration paths, as well as the amount of hydrocarbon carried depend on the oil and gas volume supplied by hydrocarbon kitchens. In Puwei area, oil and gas mainly migrated vertically along ridge-like structures of fault plane, followed by lateral migration along ridge-like structures of sandbody top in Puwei sag and Pucheng right-wing slope. Nitrogen compounds indicators tracking shows that the majority of ridge-like structures in this area are actual oil and gas migration paths.
2011, 36(3): 530-540.
doi: 10.3799/dqkx.2011.054
Abstract:
The heterogeneity of source rock, the uncertainty of frequency factor and the simulation experiment conditions (such as being open or closed, adding water or not, heating rates and the reproducibility) all affect the kinetic parameters of hydrocarbon generation from organic matter, which in turn, affect the reliability of appraised hydrocarbon potential. To this point, eighteen organic matter (OM) samples were pyrolyzed by using the Rock-Eval equipment, and parallel first-order reaction models including the model with a single frequency factor and a discrete distribution of activation energies (SFF model) and the model with multiple frequency factors and a discrete distribution of activation energies (MFF model) are adopted to analyze kinetic characteristics of hydrocarbon generation of all samples and to contrast the results difference of geological extrapolation. The comparison and analysis shows that the MFF model can avoid miscalculating the hydrocarbon generation potential (reaction ratio) in the low and high evolution stages, which appears in SFF model. For comparing the discrepancy of hydrocarbon generation from different type of kerogens, the arithmetic mean and weighted mean methods with pyrolysis parameter S2 are employed to get averaged kinetic parameters, and then averaged kinetic parameters are extrapolated with a heating rate of 3.3 ℃/Ma. At last, the application of two kind kinetic models with the kinetic parameters of the weighted mean methods in Heiyupao Sag of Songliao basin shows that if taking the hydrocarbon transformation ratio of 10% as the onset of the hydrocarbon generation threshold, the threshold depth of hydrocarbon generation is about 1 700 m, which is consistent with the appraisement result by using other geochemical parameters. Therefore, it is recommended that the kinetic method with the MFF model and the weighted mean kinetic parameters is used to appraise the hydrocarbon resource potential.
The heterogeneity of source rock, the uncertainty of frequency factor and the simulation experiment conditions (such as being open or closed, adding water or not, heating rates and the reproducibility) all affect the kinetic parameters of hydrocarbon generation from organic matter, which in turn, affect the reliability of appraised hydrocarbon potential. To this point, eighteen organic matter (OM) samples were pyrolyzed by using the Rock-Eval equipment, and parallel first-order reaction models including the model with a single frequency factor and a discrete distribution of activation energies (SFF model) and the model with multiple frequency factors and a discrete distribution of activation energies (MFF model) are adopted to analyze kinetic characteristics of hydrocarbon generation of all samples and to contrast the results difference of geological extrapolation. The comparison and analysis shows that the MFF model can avoid miscalculating the hydrocarbon generation potential (reaction ratio) in the low and high evolution stages, which appears in SFF model. For comparing the discrepancy of hydrocarbon generation from different type of kerogens, the arithmetic mean and weighted mean methods with pyrolysis parameter S2 are employed to get averaged kinetic parameters, and then averaged kinetic parameters are extrapolated with a heating rate of 3.3 ℃/Ma. At last, the application of two kind kinetic models with the kinetic parameters of the weighted mean methods in Heiyupao Sag of Songliao basin shows that if taking the hydrocarbon transformation ratio of 10% as the onset of the hydrocarbon generation threshold, the threshold depth of hydrocarbon generation is about 1 700 m, which is consistent with the appraisement result by using other geochemical parameters. Therefore, it is recommended that the kinetic method with the MFF model and the weighted mean kinetic parameters is used to appraise the hydrocarbon resource potential.
2011, 36(3): 541-554.
doi: 10.3799/dakx.2011.055
Abstract:
The Silurian, influenced by the Late Caledonian movement, is a significant change stage of palaeoenvironments and palaeotectonics in Tarim basin. The transformation from Pre-Silurian marine carbonate dominant deposits into Silurian marine clastic dominant deposits is bounded by the basin-scale unconformity surface at the bottom of Silurian. It is important to recognize the character of the tectonic movement and its depositional response by studying the sedimentary successions and mineral and lithological feature of sandstone in this period. Therefore, the outcrops in Keping area, where the Silurian depositional sequence is continuous and of perfect exposure, were selected for this study. Based on the detailed outcrop observation, sampling and laboratory tests, the sedimentary environments and successions of the Early-Middle Silurian, and its responses to sea-level changes are reconstructed, and then sequence stratigraphy units are divided. Continental shelf, deltas and tidal influenced shoreline etc. are recognized from the Lower-Middle Silurian in Keping area. Large scale deltas deposits have been founded in the Lower Silurian. The study results of sandstone framework mineralogy composition, compared with Dickinson's framework modes, reveal that the Early-Middle Silurian sandstone were mainly derived from the provenance of collision orogenes, forebulge, and continental block. It directly reflects that the orogene around the Tarim plate's impact was due to the Late Caledonian compression during the Early Silurian. As a result, the north and the south of the Tarim plate were uplifted and a large denudation area was formed. Sedimentary successions analysis reveals the tectonics and eustatic fluctuation in the period of the Early-Middle Silurian. During the early stage (Kepingtage stage) of the Early-Middle Silurian, tectonic activity was intensive and eustatic fluctuation was obvious under the influence of the Late Caledonian movement. As a result, large scale delta systems with lower maturity and higher lithic content sandstone on the background of continental shelf environments developed, which reflects that as a result of rapid uplifting, there was an abundance of source input from the north of Tarim block. During the later stage of the Early-Middle Silurian, tectonic activities decreased and got stabilized, and low-amplitude eustatic fluctuation was dominant. Tidal action was obvious, and tidal flat, tidal channel, small deltas, and lagoon were developed, which sandstone was charactered by higher maturity and lower lithic content. Sedimentary successions of the Early-Middle Silurian indicate that tectonic activities decreased, and the depression area was filled with sediments.
The Silurian, influenced by the Late Caledonian movement, is a significant change stage of palaeoenvironments and palaeotectonics in Tarim basin. The transformation from Pre-Silurian marine carbonate dominant deposits into Silurian marine clastic dominant deposits is bounded by the basin-scale unconformity surface at the bottom of Silurian. It is important to recognize the character of the tectonic movement and its depositional response by studying the sedimentary successions and mineral and lithological feature of sandstone in this period. Therefore, the outcrops in Keping area, where the Silurian depositional sequence is continuous and of perfect exposure, were selected for this study. Based on the detailed outcrop observation, sampling and laboratory tests, the sedimentary environments and successions of the Early-Middle Silurian, and its responses to sea-level changes are reconstructed, and then sequence stratigraphy units are divided. Continental shelf, deltas and tidal influenced shoreline etc. are recognized from the Lower-Middle Silurian in Keping area. Large scale deltas deposits have been founded in the Lower Silurian. The study results of sandstone framework mineralogy composition, compared with Dickinson's framework modes, reveal that the Early-Middle Silurian sandstone were mainly derived from the provenance of collision orogenes, forebulge, and continental block. It directly reflects that the orogene around the Tarim plate's impact was due to the Late Caledonian compression during the Early Silurian. As a result, the north and the south of the Tarim plate were uplifted and a large denudation area was formed. Sedimentary successions analysis reveals the tectonics and eustatic fluctuation in the period of the Early-Middle Silurian. During the early stage (Kepingtage stage) of the Early-Middle Silurian, tectonic activity was intensive and eustatic fluctuation was obvious under the influence of the Late Caledonian movement. As a result, large scale delta systems with lower maturity and higher lithic content sandstone on the background of continental shelf environments developed, which reflects that as a result of rapid uplifting, there was an abundance of source input from the north of Tarim block. During the later stage of the Early-Middle Silurian, tectonic activities decreased and got stabilized, and low-amplitude eustatic fluctuation was dominant. Tidal action was obvious, and tidal flat, tidal channel, small deltas, and lagoon were developed, which sandstone was charactered by higher maturity and lower lithic content. Sedimentary successions of the Early-Middle Silurian indicate that tectonic activities decreased, and the depression area was filled with sediments.
Similarity and Difference of Hydrocarbon Accumulation History in Liaoxi Low Uplift and Liaozhong Sag
2011, 36(3): 555-564.
doi: 10.3799/dqkx.2011.056
Abstract:
In order to get an accurate understanding of the formation and distribution of hydrocarbon reservoirs, on the premise of reconstructing the strata denudation thickness in Liaodong bay area of late-stage of Paleogene based on analysis of sonic time difference and stratigraphy trend thickness method, the hydrocarbon accumulation history in Liaoxi low uplift and Liaozhong sag has been revealed based on hydrocarbon generating history, homogenization temperatures of fluid inclusions, geothermal history, burial history, oil characteristics, temperature and pressure of reservoir as well. The research indicates that the denudation ranges from 150 to 450 m in range, and the key hydrocarbon charging time of the oil and gas in Liaoxi low uplift and Liaozhong sag are after 12 Ma, both are late-stage petroleum accumulation. The difference is: the oil from Shahejie Formation of Liaoxi low uplift was charged twice, the later is the chief one, and the charging of the oil in buried hill is after the one from Shahejie Formation. However, the oil in Liaozhong sag was charged only once.
In order to get an accurate understanding of the formation and distribution of hydrocarbon reservoirs, on the premise of reconstructing the strata denudation thickness in Liaodong bay area of late-stage of Paleogene based on analysis of sonic time difference and stratigraphy trend thickness method, the hydrocarbon accumulation history in Liaoxi low uplift and Liaozhong sag has been revealed based on hydrocarbon generating history, homogenization temperatures of fluid inclusions, geothermal history, burial history, oil characteristics, temperature and pressure of reservoir as well. The research indicates that the denudation ranges from 150 to 450 m in range, and the key hydrocarbon charging time of the oil and gas in Liaoxi low uplift and Liaozhong sag are after 12 Ma, both are late-stage petroleum accumulation. The difference is: the oil from Shahejie Formation of Liaoxi low uplift was charged twice, the later is the chief one, and the charging of the oil in buried hill is after the one from Shahejie Formation. However, the oil in Liaozhong sag was charged only once.
2011, 36(3): 565-571.
doi: 10.3799/dqkx.2011.057
Abstract:
Based on large quantity of organic geochemistry data, the geochemistry characteristics are systematically analyzed on organic carbonate content (TOC), chloroform bitumen "A", overall hydrocarbon content, S1+S2, organic matter types and maturity (Ro%) and so on. It shows that the Dong 3 Member, Sha 1 Member and Sha 3 Member are the main oil source beds of Beitang sag, especially, Sha 3 Member is the best in source rock quality. The model results indicate that (1) The depth of oil generative threshold is about 2 390 m, and the temperature is about 94.2℃, and the time entering on the oil generative threshold is from 25 Ma to 28 Ma in Beitang sag; (2) The present-day temperature of Sha 3 Layer is 140-160℃, the present-day Ro ranges between 0.9%-1.4%, It is in its peak of oil generation. The temperature of Sha 1+2 Layer is 100-140℃, the Ro ranged between 0.75%-1.0%, which suggests that it is in the middle-maturity at present. The present-day temperature of Dongying Layer is 80-100℃, the present-day Ro ranges between 0.45%-0.75%, which indicates that the present-day source rocks are in low maturation.
Based on large quantity of organic geochemistry data, the geochemistry characteristics are systematically analyzed on organic carbonate content (TOC), chloroform bitumen "A", overall hydrocarbon content, S1+S2, organic matter types and maturity (Ro%) and so on. It shows that the Dong 3 Member, Sha 1 Member and Sha 3 Member are the main oil source beds of Beitang sag, especially, Sha 3 Member is the best in source rock quality. The model results indicate that (1) The depth of oil generative threshold is about 2 390 m, and the temperature is about 94.2℃, and the time entering on the oil generative threshold is from 25 Ma to 28 Ma in Beitang sag; (2) The present-day temperature of Sha 3 Layer is 140-160℃, the present-day Ro ranges between 0.9%-1.4%, It is in its peak of oil generation. The temperature of Sha 1+2 Layer is 100-140℃, the Ro ranged between 0.75%-1.0%, which suggests that it is in the middle-maturity at present. The present-day temperature of Dongying Layer is 80-100℃, the present-day Ro ranges between 0.45%-0.75%, which indicates that the present-day source rocks are in low maturation.
2011, 36(3): 572-580.
doi: 10.3799/dqkx.2011.058
Abstract:
By summarizing the researching situation of Quasicrystals, quintic symmetry Quasicrystal structure model was put forward, including Quasicrystal conjugate structural model of Icosahedra and Dodecahedra, and blocky Quasicrystal conjugate structure model generated by Al-Cu-Li. Also, by discussing basic feature of two-dimensional Quasicrystal and the selecting of two-dimensional Quasicrystal cell, we put forward two-dimensional Quasicrystal model. And then, two-dimensional Quasicrystal model with 8-fold symmetry, 10-fold symmetry, 12-fold symmetry was gotten. At last, structure model of multifractional demension on nano-particles was discussed and the multifractional demension representation value was gotten.
By summarizing the researching situation of Quasicrystals, quintic symmetry Quasicrystal structure model was put forward, including Quasicrystal conjugate structural model of Icosahedra and Dodecahedra, and blocky Quasicrystal conjugate structure model generated by Al-Cu-Li. Also, by discussing basic feature of two-dimensional Quasicrystal and the selecting of two-dimensional Quasicrystal cell, we put forward two-dimensional Quasicrystal model. And then, two-dimensional Quasicrystal model with 8-fold symmetry, 10-fold symmetry, 12-fold symmetry was gotten. At last, structure model of multifractional demension on nano-particles was discussed and the multifractional demension representation value was gotten.
2011, 36(3): 581-586.
doi: 10.3799/dqkx.2011.059
Abstract:
Weak rock tunnel in the engineering practice and experiment research have shown strong, easy to cause the rheological properties of rock deformation caused by excessive instability. We established anti-analysis system based on viscoelastic finite element method theory by monitoring the weak surrounding rock excavation process of Yunling left cave entrance according to the New Austria Tunneling Method and analyzing the initial value of surrounding rock displacement convergence and secondary support and lining of the pressure changes. By using ANSYS finite element program, the excavation process was simulated, and the actual field measured values were compared with the calculated data. The study provides a scientific basis and technical guidance for support design and construction of tunnel with safety and reliability.
Weak rock tunnel in the engineering practice and experiment research have shown strong, easy to cause the rheological properties of rock deformation caused by excessive instability. We established anti-analysis system based on viscoelastic finite element method theory by monitoring the weak surrounding rock excavation process of Yunling left cave entrance according to the New Austria Tunneling Method and analyzing the initial value of surrounding rock displacement convergence and secondary support and lining of the pressure changes. By using ANSYS finite element program, the excavation process was simulated, and the actual field measured values were compared with the calculated data. The study provides a scientific basis and technical guidance for support design and construction of tunnel with safety and reliability.
2011, 36(3): 587-593.
doi: 10.3799/dqkx.2011.060
Abstract:
Stability analysis of pile group in soft soil foundation is one of the difficult issues challenging geotechnical engineering. According to Energy Balance Principle, the equilibrium relationship among dissipation energy caused by additional stress (including excess pore water pressure) in penetration process, external work and Elastic Potential Energy is established, based on mechanical analysis of the whole process of pile group penetration test in soft soil foundation, combined with pile group effect and working performance of pile group. Meanwhile, quantitative expressions of potential energy of excess pore water pressure, soil-compacting dissipated energy, work of gravity, work of excess pore water pressure, friction energy dissipation and elastic potential energy of soil are given in accordance with the soil-compacting characteristic of pipe pile prestressed high strength and current code of pile foundation design, and energy dissipation model of PHC pile group in penetration process is constructed. Furthermore, the safety factor of local energy and total energy is derived on the basis of above-mentioned work. The reliability of the energy model is verified by its application to the stability analysis of PHC pile group foundation in a project and the comparison with the numerical simulation results, which is of significance for guiding discrimination of the stability of PHC pile group in soft soil foundation.
Stability analysis of pile group in soft soil foundation is one of the difficult issues challenging geotechnical engineering. According to Energy Balance Principle, the equilibrium relationship among dissipation energy caused by additional stress (including excess pore water pressure) in penetration process, external work and Elastic Potential Energy is established, based on mechanical analysis of the whole process of pile group penetration test in soft soil foundation, combined with pile group effect and working performance of pile group. Meanwhile, quantitative expressions of potential energy of excess pore water pressure, soil-compacting dissipated energy, work of gravity, work of excess pore water pressure, friction energy dissipation and elastic potential energy of soil are given in accordance with the soil-compacting characteristic of pipe pile prestressed high strength and current code of pile foundation design, and energy dissipation model of PHC pile group in penetration process is constructed. Furthermore, the safety factor of local energy and total energy is derived on the basis of above-mentioned work. The reliability of the energy model is verified by its application to the stability analysis of PHC pile group foundation in a project and the comparison with the numerical simulation results, which is of significance for guiding discrimination of the stability of PHC pile group in soft soil foundation.
2011, 36(3): 594-598.
doi: 10.3799/dqkx.2011.061
Abstract:
In order to understand the effect of microbial activities on the occurrence of high arsenic groundwater,microcosm experiments were conducted using the indigenous microbe (YH002) isolated from high arsenic groundwater collected from Hetao Plain. The experiments show that the microcosm supplemented with bacteria and glucose,bacterial metabolism can excrete the organic acid which can cause pH decline. Under anoxic conditions,the maximal OD values reached 0.189 on the 7th day and the pH reduced to 6.22. However,under oxic conditions,the maximum of OD value also occurred on the 7th day with the value of 0.286,while pH values reduced to 6.04 at the end of the experiment. The initial concentration of As (III) was 74 μg/L,accounting for 11.2% of the total arsenic,when at the presence of the microbe and glucose,As (III) concentrations were 278 μg/L and 310 μg/L,accounting for 42% and 47% of the total arsenic,in the N2 and O2 atmosphere,respectively. The experimental results show that the indigenous microbe is capable of reducing As (V) to As (III) in groundwater.
In order to understand the effect of microbial activities on the occurrence of high arsenic groundwater,microcosm experiments were conducted using the indigenous microbe (YH002) isolated from high arsenic groundwater collected from Hetao Plain. The experiments show that the microcosm supplemented with bacteria and glucose,bacterial metabolism can excrete the organic acid which can cause pH decline. Under anoxic conditions,the maximal OD values reached 0.189 on the 7th day and the pH reduced to 6.22. However,under oxic conditions,the maximum of OD value also occurred on the 7th day with the value of 0.286,while pH values reduced to 6.04 at the end of the experiment. The initial concentration of As (III) was 74 μg/L,accounting for 11.2% of the total arsenic,when at the presence of the microbe and glucose,As (III) concentrations were 278 μg/L and 310 μg/L,accounting for 42% and 47% of the total arsenic,in the N2 and O2 atmosphere,respectively. The experimental results show that the indigenous microbe is capable of reducing As (V) to As (III) in groundwater.
