Various extensional structures,e.g.,half grabens,detachment faults,and metamorphic core complexes,were formed in the Liaodong Peninsula.There are two metamorphic core complexes (mcc's) in the western part of the P...Various extensional structures,e.g.,half grabens,detachment faults,and metamorphic core complexes,were formed in the Liaodong Peninsula.There are two metamorphic core complexes (mcc's) in the western part of the Peninsula,i.e.the Liaonan mcc and the Wanfu mcc.They share the same lower plate and constitute a conjugate mcc pair.The Dayingzi detachment fault system and the three half grabens are exposed in the central and eastern parts,respectively.U-Pb dating of zircons from syntectonic plutons in the lower plates of the detachment faults and volcanic rocks from half graben basins indicates that their formation spans from 135 to 106 Ma,although the individual structure may be formed at a particular stage.Despite the differences in age of formation,in the regional attitudes,and in rooting depths,the extensional structures have great similarities in their kinematics,geometrical asymmetry,and coeval tectono-magmatic activities etc.Macroscopically,the extensional structures constitute conjugate associations,but a particular one generally has asymmetric patterns.Early Cretaceous extensional structures extend from the Liaodong Peninsula to North China,Northeast China,South China,and eastern Mongolia and Transbaikal area in Russia.The extensional structures from different areas share many common features.The Liaodong Peninsula is the miniature of the East Asia with respect to the formation of extensional structures in Early Cretaceous.It is suggested that the interaction of the Izanagi Plate with Eurasia Plate is responsible for the extension of crust.The structural mobility of the lithosphere,partly attributed to the fluid flow at the depth,and detachment faulting in both the crustal and mantle lithosphere provide important constraints on the development of Early Cretaceous extensional structures in the East Asia.展开更多
Unlike most Precambrian cratons that have thick sub-continental lithospheric roots,the Archean lithosphere beneath the North China Craton is thin (reduced from 200 km to about 80 km),and has been replaced by a geochem...Unlike most Precambrian cratons that have thick sub-continental lithospheric roots,the Archean lithosphere beneath the North China Craton is thin (reduced from 200 km to about 80 km),and has been replaced by a geochemically juvenile lithospheric mantle.This is a unique regional geological event,which has attracted worldwide attention.In the North China Block,Late Mesozoic extensional tectonics is evident by low-angle detachment faults,syntectonic plutons bounded by ductile faults,metamorphic core complexes (MCC) and widespread Jurassic to Cretaceous half-grabens filled by continental terrigenous deposits and volcanic rocks.At a regional scale,these structures share the same NW-SE extensional direction,while maintaining their own individual kinematics.In other words,the MCC feature a top-to-the-NW sense of shear,and syntectonic plutons are typified by a top-to-the-SE shearing deformations.Geochronological results indicate that the extensional structures were formed between 130-120 Ma.These extensional events lead to magmatic rock emplacement,distributed at the footwall of the detachment faults.Two different exhumation stages can be identified based on regional structural and magmatic interpretation:a Jurassic slow or negligible exhumation and a Cretaceous fast one assisted by normal faulting.These two cooling stages correspond to distinct geodynamic processes that occurred during the Jurassic and Cretaceous.Extensional tectonics appear to have been insignificant before the Early Cretaceous,and the process may be demonstrated by partial melting of the crust.The second stage,dominated by an extensional regime,developed after ca 120 Ma,and is tentatively correlated with crustal extension caused by lithospheric removal of the North China Craton.展开更多
The Wulong lode deposit contains over 80 tonnes of gold with an average grade of 5.35 g/t.It is one of the largest deposits in Dandong City,Liaoning Province in northeast China.Previous studies on the deposit focused ...The Wulong lode deposit contains over 80 tonnes of gold with an average grade of 5.35 g/t.It is one of the largest deposits in Dandong City,Liaoning Province in northeast China.Previous studies on the deposit focused on its geological characteristics,geochemistry,fluid inclusions,and the timing of gold mineralization.However,controversy remains regarding the origin of the ore-forming fluids and metals,and the genesis of the gold deposit.This paper presents zircon U-Pb and pyrite Rb-Sr ages and S,Pb,He,and Ar isotopic results along with quartz H and O isotopic data for all litho-units associated with the deposit.Laser ablation inductively coupled mass spectrometry measurements yielded zircon U-Pb dates for samples of pre-mineralization rocks like granite porphyry dike,the Sanguliu granodiorite,fine-grained diorite,and syn-mineralization diorite,as well as post-mineralization dolerite,and lamprophyre;their emplacement ages are 126±1 Ma,124±1 Ma,123±1 Ma,120±1 Ma,119±2 Ma,and 115±2 Ma,respectively.The pyrite Rb-Sr isochron age is 119±1 Ma,indicating that both magmatism and mineralization occurred during the Early Cretaceous.The δ18OH2 O values of ore-forming hydrothermal fluids from the quartz-polymetallic sulfide vein stage vary from 4.8‰to 6.5‰,and the δDv-SMOW values are between-67.7‰and-75.9‰,indicating that the ore-forming fluids were primarily magmatic.The noble gas isotope compositions of fluid inclusions hosted in pyrite suggest that the ore-forming fluids were dominantly derived from crustal sources with minor mantle input.Sulfur isotopic values of pyrite vary between 0.2‰and 3.5‰,suggesting that S was derived from a homogeneous magmatic source or possibly from fluids derived from the crust.The Pb isotopic compositions of sulfides（207 Pb/204 Pb=15.51-15.71,206 Pb/204 Pb=17.35-18.75,208 Pb/204 Pb=38.27-40.03） indicate that the Pb of the Wulong gold deposit is a mixture of crust and mantle components.Geochronological and geochemical data,together with the regional geological history,i展开更多
Large scale lithosphere thinning is an important characteristic of the destruction of the North China Craton （NCC） during the late Mesozoic. A series of extensional structures were developed under extensional settin...Large scale lithosphere thinning is an important characteristic of the destruction of the North China Craton （NCC） during the late Mesozoic. A series of extensional structures were developed under extensional setting, among which is the Dayingzi detachment fault system （DFS）. The DFS is constituted by three parts, volcano-sedimentary basins at the hanging wall, the Dayingzi-Huanghuadian detachment fault zone, and Paleoproterozoic metamorphic rock series and Mesozoic plutons at the footwall. In the section across the detachment fault zone, there is a sequence of tectonites including fault gouge, microbreccia, cataclastic-mylonites, mylonites, and gneissic biotite monzonite granite. Microstructural characteristics of tectonites and electron backscatter diffraction （EBSD） patterns of quartz indicate that the rocks from the footwall experienced a process from upper greenschist facies to lower greenschist facies. SHRIMP and LA-ICP MS U-Pb dating of zircons from the volcanic rocks in the basins, the tectonic evolution of the DFS is summarized as follows： 1） regional extension started at 135.0±1.2 Ma ago, when the detachment fault cut through the middle crust. Faulting induced the upwelling of magma and eruption of volcanic rocks and deformed a series of medium-acid volcanic rocks; 2） after 135.0±1.2 Ma, a large scale detachment faulting was active cross-cutting the mid-upper crust. The western margin of Jurassic and Triassic granite was ductilly and brittly sheared; besides, the Cretaceous volcanoedimentary rocks were tilted when the master fault approached the surface; 3） at around 127±1 Ma, the detachment fault stopped its activity and was intruded by the unsheared Cretaceous granite near Chaoyang. Comparison with the Liaonan metamorphic core complex （MCC） and other extensional structures in Liaodong Peninsula led to a general trend of including three zones in the Peninsula： MCC zone, detachment fault systems （DFS） zone, and half graben zone. MCC commonly cuts through the mid-lower cr展开更多
Pb isotopic analyses were reported for sulfide and hydrothermal carbonate minerals and marble of the Xiquegou lead-zinc, the Zhenzigou zinc-lead and the Gaojiapuzi silver deposits from the Qingchengzi ore field and th...Pb isotopic analyses were reported for sulfide and hydrothermal carbonate minerals and marble of the Xiquegou lead-zinc, the Zhenzigou zinc-lead and the Gaojiapuzi silver deposits from the Qingchengzi ore field and the Beiwagou zinc-lead deposit in the west, Proterozoic Liaodong rift zone. Pb isotopic ratios of the marble from the Qingchengzi ore field range from 18.24 to 30.63 for 206 Pb/204Pb, 15.59 to 17.05 for207Pb/204Pb and 37.43 to 38.63 for 208Pb/204Pb. The marble gives a Pb-Pb isochron age of 1822±92 Ma, which is interpreted as the age of the metamorphism of the marble. Ore Pb, including Pb of sulfide and hydrothermal car- bonate minerals, from the Qingchengzi ore field shows limited variation with 206 Pb/204Pb=17.66- 17.96, 207 Pb/204Pb=15.60-15.74 and 208Pb/204Pb=37.94-38.60. In contrast, ore Pb from the Beiwagou deposit gives different Pb isotopic ratios with 206Pb/204Pb=15.68-15.81, 207 Pb/204Pb= 15.34-15.45 and 208Pb/204Pb=35.30-35.68. Pb of all deposits from the Liaodong rift zone is derived from the upper crust. Ore Pb of the Qingchengzi deposits is derived from a young upper crust. The model Th/U ratios of 4.40 to 4.74 for ore Pb are significantly different from that of 1.7 to 4.4 given by the marble of the Qingchengzi ore field, suggesting that marble is not the source of the ore Pb. Ore Pb of the Beiwagou deposit is extracted from its source and the deposit is formed at the Paleoproterozoic era. Different Pb isotopic ratios of the Qingchengzi ore field and the Beiwagou deposit are due to different ages of the deposits and suggest that the two types of deposits are derived from different sources and are possibly formed by different ore-forming processes.展开更多
With a comprehensive geological and geophysical data base,the Paleogene in the Liaodong Bay area,which consists of the Kongdian,Shahejie and Donghying Formations from the base to top,was divided into 4 second-order se...With a comprehensive geological and geophysical data base,the Paleogene in the Liaodong Bay area,which consists of the Kongdian,Shahejie and Donghying Formations from the base to top,was divided into 4 second-order sequences and 8 third-order sequences based on the characteristics of the se-quence boundaries. Each third-order sequence is subdivided into the lowstand,lake transgressive and highstand systems tracts. The Lowstand systems tract (LST) is mainly composed of progradational parasequence sets,while the lake transgressive systems tract (TST) largely consists of the retrograda-tional parasequence sets and the highstand systems tract (HST) is dominated by the progradational parasequence sets. The main types of depositional systems include the shallow lake,semi-deep lake,deep lake,delta,fan delta,braided fluvial delta and nearshore subaqueous fan. The braided fluvial delta and fan delta depositional systems are mainly confined to the sequences of the lower SEs4-Ek,SEs3 and SEs1+2,while the sequences of SEd3,SEd2 and SEd1 are dominated by the delta and nearshore subaqueous fan depositional systems with the latter being developed at the downthrown side of the basin-bounding fault in each sequence. The evolution of the depositional systems is always con-trolled by the paleo-tectonic setting and the ancient landform in the space and geological time. It is concluded that the most favorable reservoirs are distributed in the Liaoxi low uplift and the central Liaozhong sag.展开更多
Mafic rocks are widespread on the Liaodong Peninsula and adjacent regions of the North China Craton. The majority of this magmatism was originally thought to have occurred during the Pre-Sinian, although the precise g...Mafic rocks are widespread on the Liaodong Peninsula and adjacent regions of the North China Craton. The majority of this magmatism was originally thought to have occurred during the Pre-Sinian, although the precise geochronological framework of this magmatism was unclear. Here, we present the results of more than 60 U-Pb analyses of samples performed over the past decade, with the aim of determining the spatial and temporal distribution of mafic magmatism in this area. These data indicate that Paleoproterozoic-Mesoproterozoic mafic rocks are not as widely distributed as previously thought. The combined geochronological data enabled the subdivision of the mafic magmatism into six episodes that occurred during the middle Paleoproterozoic, the late Paleoproterozoic, the Mesoproterozoic, the Late Triassic, the Middle Jurassic, and the Early Cretaceous. The middle Paleoproterozoic （2.1-2.2 Ga） mafic rocks formed in a subduction-related setting and were subsequently metamorphosed during a ca. 1.9 Ga arc-continent collision event. The late Paleoproterozoic （ca. 1.87-1.82 Ga） bimodal igneous rocks mark the end of a Paleoproterozoic tectono- thermal event, whereas Mesoproterozoic mafic dike swarms record global-scale Mesoproterozoic rifting associated with the final breakup of the Columbia supercontinent. The Late Triassic mafic magmatism is part of a Late Triassic magmatic belt that was generated by post-coilisional extension. The Middle Jurassic mafic dikes formed in a compressive tectonic setting, and the Early Cretaceous bimodal igneous rocks formed in an extensional setting similar to a back-arc basin. These latter two periods of magmatism were possibly related to subduction of the Paleo-Pacific plate.展开更多
Liaodong Bay is one of the largest semi-enclosed bays located in Bohai Sea,in northeast China.It is an important feeding and spawning place,even wintering and breeding migration base for many marine organisms.The size...Liaodong Bay is one of the largest semi-enclosed bays located in Bohai Sea,in northeast China.It is an important feeding and spawning place,even wintering and breeding migration base for many marine organisms.The size structure of phytoplankton communities is a key feature of marine ecosystems and can be used as an indicator for algae disaster,but the methods to evalute is still challenging.Here,we compared the size-fractionated chlorophyll-a method with a high-throughout sequencing method in an evaluation of the size structure of phytoplankton assemblages in Liaodong Bay,China,in 2014.The proportion of picophytoplankton was estimated at just 19%according to the results based on size-fractionated chlorophyll-a,which likely represents a severe underestimation.The sequencing method confirmed that many kinds of phytoplankton species appeared in more than one size-fractionated filter membrane,with some even dominating where the filter membrane pore size was greater than the individual phytoplankton size.According to the sequencing method,the phytoplankton assemblages in Liaodong Bay were dominated by picophytoplankton(average proportion=44%),followed by the nanophytoplankton(average 32%),a composition that is more consistent with other studies.The sequencing method provides a more robust way to assess the size structure and taxonomic diversity of marine phytoplankton communities.展开更多
The fault system of Liaodong Bay developed extensively under the control of the Tanlu Fault. The fault system can be grouped into strike-slip faults of grade Ⅰ, trunk faults of grade Ⅱand branch faults （induced fau...The fault system of Liaodong Bay developed extensively under the control of the Tanlu Fault. The fault system can be grouped into strike-slip faults of grade Ⅰ, trunk faults of grade Ⅱand branch faults （induced faults） of grade Ⅲ respectively based on its developmental scale. The faults of grade Ⅰ and Ⅱwere deep, early and large while the faults of grade Ⅲwere shallow, late and small. The formation, evolution and distribution features played a significant role in controlling the migration of oil and gas in both horizontal and vertical directions. The fluid transfer in the fault system occurred in the process of faulting. The strike-slip and trunk faults moved actively forming predominant pathways for oil and gas migration. The branch faults, with weak activity, generally controlled the development of traps and were beneficial for the accumulation and preservation of oil and gas. The faults of grade Ⅰ and Ⅱ formed the major migration pathways for oil and gas, but their fault activity rates appeared to vary along their strikes. The zones with a relatively low fault activity rate might be favorable for oil and gas accumulation. When the activities of strike-slip, trunk, and branch faults came to a halt, the fault seal behavior had a vitally important effect on the accumulation of oil and gas. The controlling role of the fault over fluid distribution was further analyzed by calculating the fault activity quantitatively.展开更多
The western Liaodong （辽东） Bay subbasin displays examples of segment, linkage of extensional fault, and fault-related folds. The Liaoxi （辽西） extensional fault system consists of a series of NNE- and NE-trending...The western Liaodong （辽东） Bay subbasin displays examples of segment, linkage of extensional fault, and fault-related folds. The Liaoxi （辽西） extensional fault system consists of a series of NNE- and NE-trending segments that were linked through relay ramps. The fault hanging walls are characterized by a series of en echelon synclines with axial traces sub-parallel to the faults. The synclines are doubly plunging located on the hanging wall of normal faults, with the strata dip sub-parallel to the fault. These folds result from along-strike displacement variations of the individual fault segments, as well as from extensional fault-related folding. In the study area, the synclines are separated by transverse intra-basin highs and relay ramps that formed where segment linkage occurred. These hanging wall synclines and their relation to fault displacement variations indicate that they are formed by extensional fault-related fold.展开更多
The sources and ecological risk from sixteen polycyclic aromatic hydrocarbons in surface sediment in the Liaodong Bay were investigated from 2014 to 2015.The total concentrations of PAHs ranged from 88.5 to 347.1 ng/g...The sources and ecological risk from sixteen polycyclic aromatic hydrocarbons in surface sediment in the Liaodong Bay were investigated from 2014 to 2015.The total concentrations of PAHs ranged from 88.5 to 347.1 ng/g,and the high value occurred in the central region of the Liaodong Bay.Cluster analysis identified two site clusters representing the coastal region affected by land-based pollution and the central region of the Liaodong Bay.Principal component analysis-multiple linear regression and diagnostic ratios suggested that PAHs contaminants originated from a mixture of combustion and petroleum sources,and the major was combustion sources.Based on sediment quality guideline,naphthalene,acenaphthylene,acenaphthene,phenanthrene and dibenz[a,h]anthracene may occasionally cause adverse biological effects in some stations.The toxic equivalent concentrations of carcinogenic PAHs indicated low carcinogenic risk for the Liaodong Bay.The ecological risk and toxic pollution levels of PAHs were higher in the central region than in the coastal region along the Liaodong Bay.展开更多
In studying sand beach erosion and protection tactics in Liaoning Province, the authors calculated the wavedata of 27 a Period (1963-1991) at Bayuquan Observation Station in Liaodong Gulf. Together with the beach leve...In studying sand beach erosion and protection tactics in Liaoning Province, the authors calculated the wavedata of 27 a Period (1963-1991) at Bayuquan Observation Station in Liaodong Gulf. Together with the beach levellingsand some simple marking stakes monitoring and by having the aid of local annals, the paper analysed the present situationsof the coastline and the causes of sand coastal recession and serious consequences, and then discussed the dynamic processof alongshore sand transport. Simultaneously, based on alongshore sand transport model, oneline cut-and-fill theory anddynamical water model(sea level rise), the authors preliminary estimated beach process for the future in the area.Recently, the coastline is being eroded and 2/3 of the sand coast is subjected to erosion, which the recession rate ofthe individual sector exceed 7. 0 m/a. Coastal erosion has threatened villages, roads, factories and tourist resources. Sealevel rises and the decreasing amount of materials by rivers discharged into the sea and the activities of man, made coast line recession rate accelerate, and cause a great loss of land in the area.展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 90814006)111 Project (Grant No. B07011)
文摘Various extensional structures,e.g.,half grabens,detachment faults,and metamorphic core complexes,were formed in the Liaodong Peninsula.There are two metamorphic core complexes (mcc's) in the western part of the Peninsula,i.e.the Liaonan mcc and the Wanfu mcc.They share the same lower plate and constitute a conjugate mcc pair.The Dayingzi detachment fault system and the three half grabens are exposed in the central and eastern parts,respectively.U-Pb dating of zircons from syntectonic plutons in the lower plates of the detachment faults and volcanic rocks from half graben basins indicates that their formation spans from 135 to 106 Ma,although the individual structure may be formed at a particular stage.Despite the differences in age of formation,in the regional attitudes,and in rooting depths,the extensional structures have great similarities in their kinematics,geometrical asymmetry,and coeval tectono-magmatic activities etc.Macroscopically,the extensional structures constitute conjugate associations,but a particular one generally has asymmetric patterns.Early Cretaceous extensional structures extend from the Liaodong Peninsula to North China,Northeast China,South China,and eastern Mongolia and Transbaikal area in Russia.The extensional structures from different areas share many common features.The Liaodong Peninsula is the miniature of the East Asia with respect to the formation of extensional structures in Early Cretaceous.It is suggested that the interaction of the Izanagi Plate with Eurasia Plate is responsible for the extension of crust.The structural mobility of the lithosphere,partly attributed to the fluid flow at the depth,and detachment faulting in both the crustal and mantle lithosphere provide important constraints on the development of Early Cretaceous extensional structures in the East Asia.
基金supported by the Innovative Project of the Chinese Academy of Sciences (Grant No. KZCX2-YW-Q05-05-03)the National Natural Science Foundation of China (Grants Nos. 90714007,40872142)
文摘Unlike most Precambrian cratons that have thick sub-continental lithospheric roots,the Archean lithosphere beneath the North China Craton is thin (reduced from 200 km to about 80 km),and has been replaced by a geochemically juvenile lithospheric mantle.This is a unique regional geological event,which has attracted worldwide attention.In the North China Block,Late Mesozoic extensional tectonics is evident by low-angle detachment faults,syntectonic plutons bounded by ductile faults,metamorphic core complexes (MCC) and widespread Jurassic to Cretaceous half-grabens filled by continental terrigenous deposits and volcanic rocks.At a regional scale,these structures share the same NW-SE extensional direction,while maintaining their own individual kinematics.In other words,the MCC feature a top-to-the-NW sense of shear,and syntectonic plutons are typified by a top-to-the-SE shearing deformations.Geochronological results indicate that the extensional structures were formed between 130-120 Ma.These extensional events lead to magmatic rock emplacement,distributed at the footwall of the detachment faults.Two different exhumation stages can be identified based on regional structural and magmatic interpretation:a Jurassic slow or negligible exhumation and a Cretaceous fast one assisted by normal faulting.These two cooling stages correspond to distinct geodynamic processes that occurred during the Jurassic and Cretaceous.Extensional tectonics appear to have been insignificant before the Early Cretaceous,and the process may be demonstrated by partial melting of the crust.The second stage,dominated by an extensional regime,developed after ca 120 Ma,and is tentatively correlated with crustal extension caused by lithospheric removal of the North China Craton.
基金supported by the National Key Research and Development Program (Grand Nos. 2018YFC0603804, 2016YFC0600108-09)the National Natural Science Foundation of China (41502093)the Geological Investigation Project of the China Geological Survey (DD20160049)
文摘The Wulong lode deposit contains over 80 tonnes of gold with an average grade of 5.35 g/t.It is one of the largest deposits in Dandong City,Liaoning Province in northeast China.Previous studies on the deposit focused on its geological characteristics,geochemistry,fluid inclusions,and the timing of gold mineralization.However,controversy remains regarding the origin of the ore-forming fluids and metals,and the genesis of the gold deposit.This paper presents zircon U-Pb and pyrite Rb-Sr ages and S,Pb,He,and Ar isotopic results along with quartz H and O isotopic data for all litho-units associated with the deposit.Laser ablation inductively coupled mass spectrometry measurements yielded zircon U-Pb dates for samples of pre-mineralization rocks like granite porphyry dike,the Sanguliu granodiorite,fine-grained diorite,and syn-mineralization diorite,as well as post-mineralization dolerite,and lamprophyre;their emplacement ages are 126±1 Ma,124±1 Ma,123±1 Ma,120±1 Ma,119±2 Ma,and 115±2 Ma,respectively.The pyrite Rb-Sr isochron age is 119±1 Ma,indicating that both magmatism and mineralization occurred during the Early Cretaceous.The δ18OH2 O values of ore-forming hydrothermal fluids from the quartz-polymetallic sulfide vein stage vary from 4.8‰to 6.5‰,and the δDv-SMOW values are between-67.7‰and-75.9‰,indicating that the ore-forming fluids were primarily magmatic.The noble gas isotope compositions of fluid inclusions hosted in pyrite suggest that the ore-forming fluids were dominantly derived from crustal sources with minor mantle input.Sulfur isotopic values of pyrite vary between 0.2‰and 3.5‰,suggesting that S was derived from a homogeneous magmatic source or possibly from fluids derived from the crust.The Pb isotopic compositions of sulfides（207 Pb/204 Pb=15.51-15.71,206 Pb/204 Pb=17.35-18.75,208 Pb/204 Pb=38.27-40.03） indicate that the Pb of the Wulong gold deposit is a mixture of crust and mantle components.Geochronological and geochemical data,together with the regional geological history,i
基金supported by National Natural Science Foundation of China (Grant No. 90814006)111 Project (Grant No. B07011)
文摘Large scale lithosphere thinning is an important characteristic of the destruction of the North China Craton （NCC） during the late Mesozoic. A series of extensional structures were developed under extensional setting, among which is the Dayingzi detachment fault system （DFS）. The DFS is constituted by three parts, volcano-sedimentary basins at the hanging wall, the Dayingzi-Huanghuadian detachment fault zone, and Paleoproterozoic metamorphic rock series and Mesozoic plutons at the footwall. In the section across the detachment fault zone, there is a sequence of tectonites including fault gouge, microbreccia, cataclastic-mylonites, mylonites, and gneissic biotite monzonite granite. Microstructural characteristics of tectonites and electron backscatter diffraction （EBSD） patterns of quartz indicate that the rocks from the footwall experienced a process from upper greenschist facies to lower greenschist facies. SHRIMP and LA-ICP MS U-Pb dating of zircons from the volcanic rocks in the basins, the tectonic evolution of the DFS is summarized as follows： 1） regional extension started at 135.0±1.2 Ma ago, when the detachment fault cut through the middle crust. Faulting induced the upwelling of magma and eruption of volcanic rocks and deformed a series of medium-acid volcanic rocks; 2） after 135.0±1.2 Ma, a large scale detachment faulting was active cross-cutting the mid-upper crust. The western margin of Jurassic and Triassic granite was ductilly and brittly sheared; besides, the Cretaceous volcanoedimentary rocks were tilted when the master fault approached the surface; 3） at around 127±1 Ma, the detachment fault stopped its activity and was intruded by the unsheared Cretaceous granite near Chaoyang. Comparison with the Liaonan metamorphic core complex （MCC） and other extensional structures in Liaodong Peninsula led to a general trend of including three zones in the Peninsula： MCC zone, detachment fault systems （DFS） zone, and half graben zone. MCC commonly cuts through the mid-lower cr
文摘Pb isotopic analyses were reported for sulfide and hydrothermal carbonate minerals and marble of the Xiquegou lead-zinc, the Zhenzigou zinc-lead and the Gaojiapuzi silver deposits from the Qingchengzi ore field and the Beiwagou zinc-lead deposit in the west, Proterozoic Liaodong rift zone. Pb isotopic ratios of the marble from the Qingchengzi ore field range from 18.24 to 30.63 for 206 Pb/204Pb, 15.59 to 17.05 for207Pb/204Pb and 37.43 to 38.63 for 208Pb/204Pb. The marble gives a Pb-Pb isochron age of 1822±92 Ma, which is interpreted as the age of the metamorphism of the marble. Ore Pb, including Pb of sulfide and hydrothermal car- bonate minerals, from the Qingchengzi ore field shows limited variation with 206 Pb/204Pb=17.66- 17.96, 207 Pb/204Pb=15.60-15.74 and 208Pb/204Pb=37.94-38.60. In contrast, ore Pb from the Beiwagou deposit gives different Pb isotopic ratios with 206Pb/204Pb=15.68-15.81, 207 Pb/204Pb= 15.34-15.45 and 208Pb/204Pb=35.30-35.68. Pb of all deposits from the Liaodong rift zone is derived from the upper crust. Ore Pb of the Qingchengzi deposits is derived from a young upper crust. The model Th/U ratios of 4.40 to 4.74 for ore Pb are significantly different from that of 1.7 to 4.4 given by the marble of the Qingchengzi ore field, suggesting that marble is not the source of the ore Pb. Ore Pb of the Beiwagou deposit is extracted from its source and the deposit is formed at the Paleoproterozoic era. Different Pb isotopic ratios of the Qingchengzi ore field and the Beiwagou deposit are due to different ages of the deposits and suggest that the two types of deposits are derived from different sources and are possibly formed by different ore-forming processes.
基金Supported by Key Technologies Research and Development Program (Grant No.2001BA605A09-1)
文摘With a comprehensive geological and geophysical data base,the Paleogene in the Liaodong Bay area,which consists of the Kongdian,Shahejie and Donghying Formations from the base to top,was divided into 4 second-order sequences and 8 third-order sequences based on the characteristics of the se-quence boundaries. Each third-order sequence is subdivided into the lowstand,lake transgressive and highstand systems tracts. The Lowstand systems tract (LST) is mainly composed of progradational parasequence sets,while the lake transgressive systems tract (TST) largely consists of the retrograda-tional parasequence sets and the highstand systems tract (HST) is dominated by the progradational parasequence sets. The main types of depositional systems include the shallow lake,semi-deep lake,deep lake,delta,fan delta,braided fluvial delta and nearshore subaqueous fan. The braided fluvial delta and fan delta depositional systems are mainly confined to the sequences of the lower SEs4-Ek,SEs3 and SEs1+2,while the sequences of SEd3,SEd2 and SEd1 are dominated by the delta and nearshore subaqueous fan depositional systems with the latter being developed at the downthrown side of the basin-bounding fault in each sequence. The evolution of the depositional systems is always con-trolled by the paleo-tectonic setting and the ancient landform in the space and geological time. It is concluded that the most favorable reservoirs are distributed in the Liaoxi low uplift and the central Liaozhong sag.
基金financially supported by the National Key Basic Research Program of China(Grant No.2012CB416603)the National Natural Science Foundation of China(Grant No.90914001)+1 种基金the Opening Foundation of the Peking University(Grant No. 0000010541)Undergraduates Innovating Experimentation Project of Jilin University(Grant No.2010C61164)
文摘Mafic rocks are widespread on the Liaodong Peninsula and adjacent regions of the North China Craton. The majority of this magmatism was originally thought to have occurred during the Pre-Sinian, although the precise geochronological framework of this magmatism was unclear. Here, we present the results of more than 60 U-Pb analyses of samples performed over the past decade, with the aim of determining the spatial and temporal distribution of mafic magmatism in this area. These data indicate that Paleoproterozoic-Mesoproterozoic mafic rocks are not as widely distributed as previously thought. The combined geochronological data enabled the subdivision of the mafic magmatism into six episodes that occurred during the middle Paleoproterozoic, the late Paleoproterozoic, the Mesoproterozoic, the Late Triassic, the Middle Jurassic, and the Early Cretaceous. The middle Paleoproterozoic （2.1-2.2 Ga） mafic rocks formed in a subduction-related setting and were subsequently metamorphosed during a ca. 1.9 Ga arc-continent collision event. The late Paleoproterozoic （ca. 1.87-1.82 Ga） bimodal igneous rocks mark the end of a Paleoproterozoic tectono- thermal event, whereas Mesoproterozoic mafic dike swarms record global-scale Mesoproterozoic rifting associated with the final breakup of the Columbia supercontinent. The Late Triassic mafic magmatism is part of a Late Triassic magmatic belt that was generated by post-coilisional extension. The Middle Jurassic mafic dikes formed in a compressive tectonic setting, and the Early Cretaceous bimodal igneous rocks formed in an extensional setting similar to a back-arc basin. These latter two periods of magmatism were possibly related to subduction of the Paleo-Pacific plate.
基金financed by the National Natural Science Funds Project (No. 51779066)the Marine and Fisheries Research Project of Liaoning Province (No. 201710)the High-level Talents Innovative Supporting Plans-Young Scientific and Technical Star Project (No. 2016RQ080)
文摘Liaodong Bay is one of the largest semi-enclosed bays located in Bohai Sea,in northeast China.It is an important feeding and spawning place,even wintering and breeding migration base for many marine organisms.The size structure of phytoplankton communities is a key feature of marine ecosystems and can be used as an indicator for algae disaster,but the methods to evalute is still challenging.Here,we compared the size-fractionated chlorophyll-a method with a high-throughout sequencing method in an evaluation of the size structure of phytoplankton assemblages in Liaodong Bay,China,in 2014.The proportion of picophytoplankton was estimated at just 19%according to the results based on size-fractionated chlorophyll-a,which likely represents a severe underestimation.The sequencing method confirmed that many kinds of phytoplankton species appeared in more than one size-fractionated filter membrane,with some even dominating where the filter membrane pore size was greater than the individual phytoplankton size.According to the sequencing method,the phytoplankton assemblages in Liaodong Bay were dominated by picophytoplankton(average proportion=44%),followed by the nanophytoplankton(average 32%),a composition that is more consistent with other studies.The sequencing method provides a more robust way to assess the size structure and taxonomic diversity of marine phytoplankton communities.
文摘The fault system of Liaodong Bay developed extensively under the control of the Tanlu Fault. The fault system can be grouped into strike-slip faults of grade Ⅰ, trunk faults of grade Ⅱand branch faults （induced faults） of grade Ⅲ respectively based on its developmental scale. The faults of grade Ⅰ and Ⅱwere deep, early and large while the faults of grade Ⅲwere shallow, late and small. The formation, evolution and distribution features played a significant role in controlling the migration of oil and gas in both horizontal and vertical directions. The fluid transfer in the fault system occurred in the process of faulting. The strike-slip and trunk faults moved actively forming predominant pathways for oil and gas migration. The branch faults, with weak activity, generally controlled the development of traps and were beneficial for the accumulation and preservation of oil and gas. The faults of grade Ⅰ and Ⅱ formed the major migration pathways for oil and gas, but their fault activity rates appeared to vary along their strikes. The zones with a relatively low fault activity rate might be favorable for oil and gas accumulation. When the activities of strike-slip, trunk, and branch faults came to a halt, the fault seal behavior had a vitally important effect on the accumulation of oil and gas. The controlling role of the fault over fluid distribution was further analyzed by calculating the fault activity quantitatively.
基金supported by the project of the State Key Labo-ratory of Petroleum Resource and Prospecting and Tianjin Oil Company, CNOOC Limited (No. SC06TJ-TQL-004)
文摘The western Liaodong （辽东） Bay subbasin displays examples of segment, linkage of extensional fault, and fault-related folds. The Liaoxi （辽西） extensional fault system consists of a series of NNE- and NE-trending segments that were linked through relay ramps. The fault hanging walls are characterized by a series of en echelon synclines with axial traces sub-parallel to the faults. The synclines are doubly plunging located on the hanging wall of normal faults, with the strata dip sub-parallel to the fault. These folds result from along-strike displacement variations of the individual fault segments, as well as from extensional fault-related folding. In the study area, the synclines are separated by transverse intra-basin highs and relay ramps that formed where segment linkage occurred. These hanging wall synclines and their relation to fault displacement variations indicate that they are formed by extensional fault-related fold.
基金The Liaoning Province Natural Science Foundation under contract No.201602409the Public Science and Technology Research Funds Projects of Ocean under contract No.201505019
文摘The sources and ecological risk from sixteen polycyclic aromatic hydrocarbons in surface sediment in the Liaodong Bay were investigated from 2014 to 2015.The total concentrations of PAHs ranged from 88.5 to 347.1 ng/g,and the high value occurred in the central region of the Liaodong Bay.Cluster analysis identified two site clusters representing the coastal region affected by land-based pollution and the central region of the Liaodong Bay.Principal component analysis-multiple linear regression and diagnostic ratios suggested that PAHs contaminants originated from a mixture of combustion and petroleum sources,and the major was combustion sources.Based on sediment quality guideline,naphthalene,acenaphthylene,acenaphthene,phenanthrene and dibenz[a,h]anthracene may occasionally cause adverse biological effects in some stations.The toxic equivalent concentrations of carcinogenic PAHs indicated low carcinogenic risk for the Liaodong Bay.The ecological risk and toxic pollution levels of PAHs were higher in the central region than in the coastal region along the Liaodong Bay.
文摘In studying sand beach erosion and protection tactics in Liaoning Province, the authors calculated the wavedata of 27 a Period (1963-1991) at Bayuquan Observation Station in Liaodong Gulf. Together with the beach levellingsand some simple marking stakes monitoring and by having the aid of local annals, the paper analysed the present situationsof the coastline and the causes of sand coastal recession and serious consequences, and then discussed the dynamic processof alongshore sand transport. Simultaneously, based on alongshore sand transport model, oneline cut-and-fill theory anddynamical water model(sea level rise), the authors preliminary estimated beach process for the future in the area.Recently, the coastline is being eroded and 2/3 of the sand coast is subjected to erosion, which the recession rate ofthe individual sector exceed 7. 0 m/a. Coastal erosion has threatened villages, roads, factories and tourist resources. Sealevel rises and the decreasing amount of materials by rivers discharged into the sea and the activities of man, made coast line recession rate accelerate, and cause a great loss of land in the area.
