This paper discusses the relationship between the volume loss, fluid flow and component variations in the ductile shear zone of the southern Tan-Lu fault belt. The results show that there is a large amount of fluids f...This paper discusses the relationship between the volume loss, fluid flow and component variations in the ductile shear zone of the southern Tan-Lu fault belt. The results show that there is a large amount of fluids flowing through the shear zone during mylonitization, accompanied with the loss of volume of rocks and variations of elements and oxygen isotopes. The calculated temperature for mylonitization in different mylonites ranges from 446 to 484℃, corresponding to that of 475 to 500℃ for the wall rocks. The condition of differential stress during mylonization has been obtained between 99 and 210 MPa, whereas the differential stress in the wall rock gneiss is 70-78 MPa. The mylonites are enriched by factors of 1.32-1.87 in elements such as TiO2, P2O5, MnO, Y, Zr and V and depleted in SiO2, Na2O, K2O, Al203, Sr, Rb and light REEs compared to their protolith gneiss. The immobile element enrichments are attributed to enrichments in residual phases such as ilmentite, zircon, apatite and epidote in mylonites and are interpreted as due to volume losses from 15% to 60% in the ductile shear zone. The largest amount of SiO2 loss is 35.76 g/100 g in the ductile shear zone, which shows the fluid infiltration. Modeling calculated results of the fluid/rock ratio for the ductile shear zone range from 196 to 1192 by assuming different degrees of fluid saturation. Oxygen isotope changes of quartz and feldspar and the calculated fluid are corresponding to the variations of differential flow stress in the ductile shear zone. With increasing differential flow stress, the mylonites show a slight decrease of δ^18O in quartz, K-feldspar and fluid.展开更多
Intrusions in the Zhangbaling uplift zone and the eastern margin of the Dabie orogenic belt belong to the syntectonic intrusions developed during the strike-slip stage in the southern segment of the Tan-Lu fault zone....Intrusions in the Zhangbaling uplift zone and the eastern margin of the Dabie orogenic belt belong to the syntectonic intrusions developed during the strike-slip stage in the southern segment of the Tan-Lu fault zone. However, characteristics of rare earth elements show that intrusions in the Zhangbaling uplift zone have the characteristics of mantle source type and those in the eastern margin of Dabie belt are the typical crust source type. Therefore, Au-deposits related to the intrusions in the Zhangbaling uplift zone are developed better than those in the eastern margin of the Dabieshan. The research results of the rare earth elements coincide with the studies of geophysics, tectonic setting and stable isotope. It is further indicated that the rare earth elements offer effective approach to tracing the material sources of magmatic rocks.展开更多
Bulk separates of porphyroclastic phengite, neoformed phengite and their mixtures from the Tan-Lu HP mylonites overprinted on the Sulu UHP rocks were analyzed with the 40Ar/39Ar step heating method. Two samples of the...Bulk separates of porphyroclastic phengite, neoformed phengite and their mixtures from the Tan-Lu HP mylonites overprinted on the Sulu UHP rocks were analyzed with the 40Ar/39Ar step heating method. Two samples of the neoformed phengite from ultramylonite give 40Ar/39Ar plateau ages of 209.9±1.8 Ma and 214.3±1.8 Ma, which are interpreted as representing cooling times of the TanLu sinistral faulting, and provide geochronological evidence for the syn-orogenic faulting of the Tan-Lu fault zone. The results show that the phengite formed during the retrograde eclogite-facies mylonitization was not contaminated with excess argon and can be used for dating the deformation. Argon closure in previous K-bearing minerals with excess argon under a retrograde HP dry condition is considered to be the reason for lack of excess argon incorporation in the neoformed phengite. Five porphyroclastic phengite samples yield 40Ar/39Ar plateau ages ranging from 666±12 Ma to 307.1±3.3 Ma, which are interpreted as being contaminated with excess argon. Two mixture samples with plateau ages of 239.4±2.1 Ma and 239.3±2.0 Ma show upward-convex age spectra caused by the mixture of older porphyroclastic phengite with excess argon incorporation and younger neoformed phengite without excess argon incorporation. It is demonstrated that excess argon introduced from the previous UHP metamorphism is still preserved in the pre-existing phengite after the Tan-Lu eclogite-facies mylonitization. The intense deformation under HT and HP conditions cannot erase excess argon in the previous phengite totally due to restricted fluid activities. These porphyroclastic phengite previously contaminated with excess argon cannot be used for dating the later HP deformation. This indicates that deformation under a HP dry condition does not play an important role in removing previous 40Are in phengite.展开更多
The paper studies CO2 degassing and controlling factors under the condition of contact metamorphism in the Shuangshan area, southern Tan-Lu fault belt and the method of calculating the amount of CO2 degassing. The res...The paper studies CO2 degassing and controlling factors under the condition of contact metamorphism in the Shuangshan area, southern Tan-Lu fault belt and the method of calculating the amount of CO2 degassing. The results show that the amount of CO2 degassing is controlled by the characteristics of the country rocks, including the thermal conductivity, penetrability, porosity and connectivity. Compositions, size and depth of intrusive rock also have an important influence on CO2 degassing, i.e., they generated numerous cracks in the country rocks, and thus allowed the easy flow and accumulation of fluids. The amount of CO2 flux in contact metamorphism is calculated quantitatively based on the metamorphic reaction and time-integrated fluid flux. The value （0.729- 2.446×10^4 mol/cm^2） of CO2 flux suggests that CO2 was provided mainly by the contact metamorphic reaction. The generation and releasing of CO2 are positively correlated with the degree of metamorphism, and XCO2 in fluids gradually increases from dolomite zone to calcite zone, but in the zone of grossular, fluid flux is the largest and XCO2 sharply decreases due to involvement of magmatic water. This study presents evidence that a large amount of industrial-scale CO2 can be produced during contact metamorphism. On the basis of theoretical and practical studies, a cone model has been proposed to response CO2 degassing for the contact metamorphism, and it can be used to explore CO2 accumulations beyond the oil-gas basins. This model can also be applied to the study of inorganic genesis of CO2 accumulations.展开更多
We study the nonlinear parabolic equations for travelling wave solutions of Burger’s equations. The purpose of the present work is to study various types of Burger’s equations describing waves and those are based on...We study the nonlinear parabolic equations for travelling wave solutions of Burger’s equations. The purpose of the present work is to study various types of Burger’s equations describing waves and those are based on nonlinear equations. We focus on to describe the analytic solution in the special pattern of travelling wave solutions using tan-cot function method. We discuss about inviscid and viscous version of Burger’s equation for fluid flow and investigate the effects of internal friction of a fluid via Reynolds number. By changing the velocity amplitude, the nature of flows with shock wave and disturbance are observed. For numerical solutions, the Crank-Nicolson scheme is introduced to establish the wave solutions.展开更多
The Tan-Lu fault zone across the eastern margin of the Cenozoic basins offshore the Bohai Sea is a NNE-trending right-lateral strike-slip fault system developed in the Cenozoic basin cover. It cuts through NE-to NNE-s...The Tan-Lu fault zone across the eastern margin of the Cenozoic basins offshore the Bohai Sea is a NNE-trending right-lateral strike-slip fault system developed in the Cenozoic basin cover. It cuts through NE-to NNE-striking major extensional faults that controlled the formation of Paleogene basins. Recent petroleum exploration indicates that Cenozoic structural activities of the Tan-Lu fault system have directly or indirectly affected oil and gas distribution offshore the Bohai Sea. As part of a deep fault zone the Tan-Lu fault zone has been activated since the Oligocene,and obviously affected the tectonic evolution of offshore Bohai basins since then. The formation of Paleogene rift basins offshore the Bohai Sea has utilized the pre-existing structural elements of the Tan-Lu fault zone that developed in the late Mesozoic.展开更多
The Tan-Lu Fault zone (TLFZ) is a significant fractural zone in eastern China and also a seismicity belt in North China. Based on total 4000-km-long shallow penetrated single seismic data with high-resolution, structu...The Tan-Lu Fault zone (TLFZ) is a significant fractural zone in eastern China and also a seismicity belt in North China. Based on total 4000-km-long shallow penetrated single seismic data with high-resolution, structural deformation and fault activity of the TLFZ in the Bohai Sea since the late Pleistocene are discussed in detail. The results show that the TLFZ with a discontinuous distribution and a general NNE-trending consists of 14 active subfaults with an NNE or NE strike in the Bohai Sea. Seismic data reveal that deformation zones along the subfaults in the central Bohai Sea and the Laizhou Bay are wider and more complex than those in the Liaodong Gulf. Related folds and lots of secondary normal faults which are characterized by nearly vertical fault planes and a same or reverse dip construct the fractural zone in the Laizhou Bay and the central Bohai Sea. Usually, micro sym-metrical grabens develop on the top of anticlines. In the Liaodong Gulf, subfault fractural zones usually consist of secondary normal faults with the same inclination or opposite inclination. Ages of seismic sequences and cutting relation between subfaults and seismic sequences suggest that the latest faulting age of the TLFZ is the end of the late Pleistocene in the Liaodong Gulf and the early Holocene in the Laizhou Bay and the central Bohai Sea. There is a good match between distribution of earthquakes and that of the subfaults in the Laizhou Bay and the central Bohai. Statistical result shows that total vertical offset of the TLFZ since the late Pleistocene ranges from 6 to 11 m. On the basis of offsets of the subfaults, the vertical slip rate is calculated and results show that average vertical slip rates in the central Bohai Sea are larger than those in the Liaodong Gulf and the Laizhou Bay. Slip rates more than 0.06 mm/a during 23-10 ka B.P. and 85-65 ka B.P. are larger than those in other stages. The TLFZ was mainly dominated by tensional normal component since the late Pleistocene. Synthesizing shallow deformation, activity and distribution of earthquakes, the TLFZ in the Bohai Sea can be divided into three segments: the Laizhou-Bay segment, the Bozhong segment, and the Liaodong-Gulf segment.展开更多
Samples of mylonite, ultramylonite and phyllonite were collected from 5 localities in the Anhui part of the Tan-Lu fault zone for 40Ar/39Ar chronological studies. Among them 4 samples from 3 localities on the eastern ...Samples of mylonite, ultramylonite and phyllonite were collected from 5 localities in the Anhui part of the Tan-Lu fault zone for 40Ar/39Ar chronological studies. Among them 4 samples from 3 localities on the eastern margin of the Dabie orogenic belt yielded 40Ar/39Ar plateau ages of 128 -132 Ma; and 2 samples from the western margin of the Zhangbalin uplift and eastern margin of the Bengbu uplift gave the same 40Ar/39Ar plateau ages of 120 Ma. Isochron analyses and other lines of evidence suggest that the data are reliable. The data are interpreted as cooling ages of sinistral strike-slip deformation of the Tan-Lu fault zone. The younger ages from the north might be related to slower strike-slip rising. These results indicate that the large-scale left-lateral displacement in the Tan-Lu fault zone took place in the Early Cretaceous, rather than in Late Triassic (Indosinian) as proposed by some geologists. Therefore, this fault zone is an intracontinental wrench fault rather than a transform fault or suture line developed during formation of the Dabie orogenic belt.展开更多
Two grabens were developed in the Yi-Shu segment of the Tan-Lu fault zone (TLFZ) during its extensional activities, and are now confined by four major NNE-trending normal faults and filled with Cretaceous sediments. T...Two grabens were developed in the Yi-Shu segment of the Tan-Lu fault zone (TLFZ) during its extensional activities, and are now confined by four major NNE-trending normal faults and filled with Cretaceous sediments. These faults were developed due to their reactivities, containing gouge and cutting the graben sediments. Detailed fieldwork demonstrates that the faults experienced sinistral transtensional moment related to regional NE-SW extension during the reactivity. X-ray diffraction (XRD) analysis of the finest gouge samples gives illite crystallinity values higher than 0.42°Δ2θ, indicating temperatures experienced by the gouge samples were less than 150°C. From the relation between K-Ar data and proportions of detrital illite in different size fractions of the gouge samples, we conclude that refaulting for the western boundary fault of the TLFZ, abbreviated to F4, took place at ca. 90 Ma and for the eastern boundary fault, abbreviated to F1, happened from 70 to 60 Ma. During the two phases of reactivity imposed by the same NE-SW extension, the TLFZ experienced uplifting and no sediments were deposited in the two grabens. It is suggested that the TLFZ experienced extension during the Late Cretaceous, which supports the inference that lithospheric thinning was still undergoing in the east of the North China Craton during the Late Cretaceous magmatic hiatus.展开更多
In this study,the Chinese carbon cyle dataassimilation system Tan-Tracker is developed based on the atmospheric chemical transport model(GEOS-Chem)platform.Tan-Tracker is a dual-pass data-assimilation system in which ...In this study,the Chinese carbon cyle dataassimilation system Tan-Tracker is developed based on the atmospheric chemical transport model(GEOS-Chem)platform.Tan-Tracker is a dual-pass data-assimilation system in which both CO2concentrations and CO2fluxes are simultaneously assimilated from atmospheric observations.It has several advantages,including its advanced data-assimilation method,its highly efficient computing performance,and its simultaneous assimilation of CO2concentrations and CO2fluxes.Preliminary observing system simulation experiments demonstrate its robust performance with high assimilation precision,making full use of observations.The Tan-Tracker system can only assimilate in situ observations for the moment.In the future,we hope to extend Tan-Tracker with functions for using satellite measurements,which will form the quasioperational Chinese carbon cycle data-assimilation system.展开更多
Two phases of sinistral strike-slip ductile shear belts occur on the eastern margin of the Dabie orogenic belt. A muscovite ^40Ar/^39Ar plateau age of 128 Ma was obtained from mylonite in the later ductile shear zone....Two phases of sinistral strike-slip ductile shear belts occur on the eastern margin of the Dabie orogenic belt. A muscovite ^40Ar/^39Ar plateau age of 128 Ma was obtained from mylonite in the later ductile shear zone. Three muscovite samples separated from mylonites of 3 localities in the earlier ductile shear belts yield ^40Ar/^39Ar plateau ages of 192.5±0.7 Ma, 189.7±0.6 Ma and 188.7±0.7 Ma, respectively. They are interpreted as cooling ages of the earlier sinistral strike-slip deformation. It is suggested that left-lateral displacement of the Tan-Lu fault zone started in a late stage of the collision orogeny in the Dabie-Sulu orogenic belt between the North and South China plates. Therefore, the earlier Tan-Lu fault zone was syn-orogenic strike-slip tectonics. The fault zone was used again for sinistral displacement during tectonic activities of peri-Pacific regime in Early Cretaceous. It is proposed that the fault zone occurred as a transform fault during the orogenic process.展开更多
基金the National Basic Research Development Program of China (No. 2005CB523306)National Natural Science Foundation of China (No. 30670721)+1 种基金Science and Technology Commission of Shanghai Municipality (No. 06DZ19734, 04DZ19836, 05DZ19745)The 6th Postgraduate Student Foundation of Fudan University and NIH (No. HD-34852)
基金National Natural Science Foundation of China （Grant 40473021） the National 973- Project of the Ministry of Science and Technology of China （2003CB214600） the Foundation of the State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, and the jointed project of Max-Planck-Institute of Society and Chinese Academy of Sciences in Max-Planck-Institute of Nuclear Physics,Heidelberg, Germany.
文摘This paper discusses the relationship between the volume loss, fluid flow and component variations in the ductile shear zone of the southern Tan-Lu fault belt. The results show that there is a large amount of fluids flowing through the shear zone during mylonitization, accompanied with the loss of volume of rocks and variations of elements and oxygen isotopes. The calculated temperature for mylonitization in different mylonites ranges from 446 to 484℃, corresponding to that of 475 to 500℃ for the wall rocks. The condition of differential stress during mylonization has been obtained between 99 and 210 MPa, whereas the differential stress in the wall rock gneiss is 70-78 MPa. The mylonites are enriched by factors of 1.32-1.87 in elements such as TiO2, P2O5, MnO, Y, Zr and V and depleted in SiO2, Na2O, K2O, Al203, Sr, Rb and light REEs compared to their protolith gneiss. The immobile element enrichments are attributed to enrichments in residual phases such as ilmentite, zircon, apatite and epidote in mylonites and are interpreted as due to volume losses from 15% to 60% in the ductile shear zone. The largest amount of SiO2 loss is 35.76 g/100 g in the ductile shear zone, which shows the fluid infiltration. Modeling calculated results of the fluid/rock ratio for the ductile shear zone range from 196 to 1192 by assuming different degrees of fluid saturation. Oxygen isotope changes of quartz and feldspar and the calculated fluid are corresponding to the variations of differential flow stress in the ductile shear zone. With increasing differential flow stress, the mylonites show a slight decrease of δ^18O in quartz, K-feldspar and fluid.
基金Project supported by the National Natural Science Foundation of China (40272094)
文摘Intrusions in the Zhangbaling uplift zone and the eastern margin of the Dabie orogenic belt belong to the syntectonic intrusions developed during the strike-slip stage in the southern segment of the Tan-Lu fault zone. However, characteristics of rare earth elements show that intrusions in the Zhangbaling uplift zone have the characteristics of mantle source type and those in the eastern margin of Dabie belt are the typical crust source type. Therefore, Au-deposits related to the intrusions in the Zhangbaling uplift zone are developed better than those in the eastern margin of the Dabieshan. The research results of the rare earth elements coincide with the studies of geophysics, tectonic setting and stable isotope. It is further indicated that the rare earth elements offer effective approach to tracing the material sources of magmatic rocks.
基金This study was funded by the National Natural Science Foundation of China （grant numbers 40272094, 40672131） We gratefully acknowledge Mr. Luo Xiuquan and Zhang Youquan from the Petroleum Geology Research and Laboratory Center, Institute of Petroleum Exploration and Development, Beijing, for their work on the 40Ar/39Ar analysis.
文摘Bulk separates of porphyroclastic phengite, neoformed phengite and their mixtures from the Tan-Lu HP mylonites overprinted on the Sulu UHP rocks were analyzed with the 40Ar/39Ar step heating method. Two samples of the neoformed phengite from ultramylonite give 40Ar/39Ar plateau ages of 209.9±1.8 Ma and 214.3±1.8 Ma, which are interpreted as representing cooling times of the TanLu sinistral faulting, and provide geochronological evidence for the syn-orogenic faulting of the Tan-Lu fault zone. The results show that the phengite formed during the retrograde eclogite-facies mylonitization was not contaminated with excess argon and can be used for dating the deformation. Argon closure in previous K-bearing minerals with excess argon under a retrograde HP dry condition is considered to be the reason for lack of excess argon incorporation in the neoformed phengite. Five porphyroclastic phengite samples yield 40Ar/39Ar plateau ages ranging from 666±12 Ma to 307.1±3.3 Ma, which are interpreted as being contaminated with excess argon. Two mixture samples with plateau ages of 239.4±2.1 Ma and 239.3±2.0 Ma show upward-convex age spectra caused by the mixture of older porphyroclastic phengite with excess argon incorporation and younger neoformed phengite without excess argon incorporation. It is demonstrated that excess argon introduced from the previous UHP metamorphism is still preserved in the pre-existing phengite after the Tan-Lu eclogite-facies mylonitization. The intense deformation under HT and HP conditions cannot erase excess argon in the previous phengite totally due to restricted fluid activities. These porphyroclastic phengite previously contaminated with excess argon cannot be used for dating the later HP deformation. This indicates that deformation under a HP dry condition does not play an important role in removing previous 40Are in phengite.
基金supported by grants from the Natural Science Foundation of China(grant Nos:40473021 and 40472074)the National Basic Research Program of China(grant No:2003CB214600).
文摘The paper studies CO2 degassing and controlling factors under the condition of contact metamorphism in the Shuangshan area, southern Tan-Lu fault belt and the method of calculating the amount of CO2 degassing. The results show that the amount of CO2 degassing is controlled by the characteristics of the country rocks, including the thermal conductivity, penetrability, porosity and connectivity. Compositions, size and depth of intrusive rock also have an important influence on CO2 degassing, i.e., they generated numerous cracks in the country rocks, and thus allowed the easy flow and accumulation of fluids. The amount of CO2 flux in contact metamorphism is calculated quantitatively based on the metamorphic reaction and time-integrated fluid flux. The value （0.729- 2.446×10^4 mol/cm^2） of CO2 flux suggests that CO2 was provided mainly by the contact metamorphic reaction. The generation and releasing of CO2 are positively correlated with the degree of metamorphism, and XCO2 in fluids gradually increases from dolomite zone to calcite zone, but in the zone of grossular, fluid flux is the largest and XCO2 sharply decreases due to involvement of magmatic water. This study presents evidence that a large amount of industrial-scale CO2 can be produced during contact metamorphism. On the basis of theoretical and practical studies, a cone model has been proposed to response CO2 degassing for the contact metamorphism, and it can be used to explore CO2 accumulations beyond the oil-gas basins. This model can also be applied to the study of inorganic genesis of CO2 accumulations.
文摘We study the nonlinear parabolic equations for travelling wave solutions of Burger’s equations. The purpose of the present work is to study various types of Burger’s equations describing waves and those are based on nonlinear equations. We focus on to describe the analytic solution in the special pattern of travelling wave solutions using tan-cot function method. We discuss about inviscid and viscous version of Burger’s equation for fluid flow and investigate the effects of internal friction of a fluid via Reynolds number. By changing the velocity amplitude, the nature of flows with shock wave and disturbance are observed. For numerical solutions, the Crank-Nicolson scheme is introduced to establish the wave solutions.
基金Supported by National Natural Science Foundation of China (Grant No.40372072)National Basic Research Program of China (Grant No.2006CB202301)
文摘The Tan-Lu fault zone across the eastern margin of the Cenozoic basins offshore the Bohai Sea is a NNE-trending right-lateral strike-slip fault system developed in the Cenozoic basin cover. It cuts through NE-to NNE-striking major extensional faults that controlled the formation of Paleogene basins. Recent petroleum exploration indicates that Cenozoic structural activities of the Tan-Lu fault system have directly or indirectly affected oil and gas distribution offshore the Bohai Sea. As part of a deep fault zone the Tan-Lu fault zone has been activated since the Oligocene,and obviously affected the tectonic evolution of offshore Bohai basins since then. The formation of Paleogene rift basins offshore the Bohai Sea has utilized the pre-existing structural elements of the Tan-Lu fault zone that developed in the late Mesozoic.
基金supported by the National Natural Science Foundation of China (40606014)the State Level Scientific Research Institutes' Basic R & D Operations Special Fund (2008G12)
文摘The Tan-Lu Fault zone (TLFZ) is a significant fractural zone in eastern China and also a seismicity belt in North China. Based on total 4000-km-long shallow penetrated single seismic data with high-resolution, structural deformation and fault activity of the TLFZ in the Bohai Sea since the late Pleistocene are discussed in detail. The results show that the TLFZ with a discontinuous distribution and a general NNE-trending consists of 14 active subfaults with an NNE or NE strike in the Bohai Sea. Seismic data reveal that deformation zones along the subfaults in the central Bohai Sea and the Laizhou Bay are wider and more complex than those in the Liaodong Gulf. Related folds and lots of secondary normal faults which are characterized by nearly vertical fault planes and a same or reverse dip construct the fractural zone in the Laizhou Bay and the central Bohai Sea. Usually, micro sym-metrical grabens develop on the top of anticlines. In the Liaodong Gulf, subfault fractural zones usually consist of secondary normal faults with the same inclination or opposite inclination. Ages of seismic sequences and cutting relation between subfaults and seismic sequences suggest that the latest faulting age of the TLFZ is the end of the late Pleistocene in the Liaodong Gulf and the early Holocene in the Laizhou Bay and the central Bohai Sea. There is a good match between distribution of earthquakes and that of the subfaults in the Laizhou Bay and the central Bohai. Statistical result shows that total vertical offset of the TLFZ since the late Pleistocene ranges from 6 to 11 m. On the basis of offsets of the subfaults, the vertical slip rate is calculated and results show that average vertical slip rates in the central Bohai Sea are larger than those in the Liaodong Gulf and the Laizhou Bay. Slip rates more than 0.06 mm/a during 23-10 ka B.P. and 85-65 ka B.P. are larger than those in other stages. The TLFZ was mainly dominated by tensional normal component since the late Pleistocene. Synthesizing shallow deformation, activity and distribution of earthquakes, the TLFZ in the Bohai Sea can be divided into three segments: the Laizhou-Bay segment, the Bozhong segment, and the Liaodong-Gulf segment.
基金the National Natural Science Foundation of China (Grant No.49872074).
文摘Samples of mylonite, ultramylonite and phyllonite were collected from 5 localities in the Anhui part of the Tan-Lu fault zone for 40Ar/39Ar chronological studies. Among them 4 samples from 3 localities on the eastern margin of the Dabie orogenic belt yielded 40Ar/39Ar plateau ages of 128 -132 Ma; and 2 samples from the western margin of the Zhangbalin uplift and eastern margin of the Bengbu uplift gave the same 40Ar/39Ar plateau ages of 120 Ma. Isochron analyses and other lines of evidence suggest that the data are reliable. The data are interpreted as cooling ages of sinistral strike-slip deformation of the Tan-Lu fault zone. The younger ages from the north might be related to slower strike-slip rising. These results indicate that the large-scale left-lateral displacement in the Tan-Lu fault zone took place in the Early Cretaceous, rather than in Late Triassic (Indosinian) as proposed by some geologists. Therefore, this fault zone is an intracontinental wrench fault rather than a transform fault or suture line developed during formation of the Dabie orogenic belt.
基金Supported by National Natural Science Foundation of China (Grant Nos. 90714004, 40672131)
文摘Two grabens were developed in the Yi-Shu segment of the Tan-Lu fault zone (TLFZ) during its extensional activities, and are now confined by four major NNE-trending normal faults and filled with Cretaceous sediments. These faults were developed due to their reactivities, containing gouge and cutting the graben sediments. Detailed fieldwork demonstrates that the faults experienced sinistral transtensional moment related to regional NE-SW extension during the reactivity. X-ray diffraction (XRD) analysis of the finest gouge samples gives illite crystallinity values higher than 0.42°Δ2θ, indicating temperatures experienced by the gouge samples were less than 150°C. From the relation between K-Ar data and proportions of detrital illite in different size fractions of the gouge samples, we conclude that refaulting for the western boundary fault of the TLFZ, abbreviated to F4, took place at ca. 90 Ma and for the eastern boundary fault, abbreviated to F1, happened from 70 to 60 Ma. During the two phases of reactivity imposed by the same NE-SW extension, the TLFZ experienced uplifting and no sediments were deposited in the two grabens. It is suggested that the TLFZ experienced extension during the Late Cretaceous, which supports the inference that lithospheric thinning was still undergoing in the east of the North China Craton during the Late Cretaceous magmatic hiatus.
基金supported by the Strategic Priority Research Program-Climate Change: Carbon Budget and Relevant Issues (XDA05040200)the National High Technology Research and Development Program of China (Grant No. 2013AA122002)+1 种基金the National Natural Science Foundation of China (41075076)the Knowledge Innovation Program of the Chinese Academy of Sciences (KZCX2-EW-QN207)
文摘In this study,the Chinese carbon cyle dataassimilation system Tan-Tracker is developed based on the atmospheric chemical transport model(GEOS-Chem)platform.Tan-Tracker is a dual-pass data-assimilation system in which both CO2concentrations and CO2fluxes are simultaneously assimilated from atmospheric observations.It has several advantages,including its advanced data-assimilation method,its highly efficient computing performance,and its simultaneous assimilation of CO2concentrations and CO2fluxes.Preliminary observing system simulation experiments demonstrate its robust performance with high assimilation precision,making full use of observations.The Tan-Tracker system can only assimilate in situ observations for the moment.In the future,we hope to extend Tan-Tracker with functions for using satellite measurements,which will form the quasioperational Chinese carbon cycle data-assimilation system.
文摘Two phases of sinistral strike-slip ductile shear belts occur on the eastern margin of the Dabie orogenic belt. A muscovite ^40Ar/^39Ar plateau age of 128 Ma was obtained from mylonite in the later ductile shear zone. Three muscovite samples separated from mylonites of 3 localities in the earlier ductile shear belts yield ^40Ar/^39Ar plateau ages of 192.5±0.7 Ma, 189.7±0.6 Ma and 188.7±0.7 Ma, respectively. They are interpreted as cooling ages of the earlier sinistral strike-slip deformation. It is suggested that left-lateral displacement of the Tan-Lu fault zone started in a late stage of the collision orogeny in the Dabie-Sulu orogenic belt between the North and South China plates. Therefore, the earlier Tan-Lu fault zone was syn-orogenic strike-slip tectonics. The fault zone was used again for sinistral displacement during tectonic activities of peri-Pacific regime in Early Cretaceous. It is proposed that the fault zone occurred as a transform fault during the orogenic process.
