The Erguna ductile shear zone is situated in the Erguna Massif,which has been exposed along the eastern bank of the Erguna River in northeastern China.The authors present comprehensive study results on the macro-and m...The Erguna ductile shear zone is situated in the Erguna Massif,which has been exposed along the eastern bank of the Erguna River in northeastern China.The authors present comprehensive study results on the macro-and micro-structures,finite strain and kinematic vorticity,quartz electron backscatter diffraction(EBSD)fabrics,and geochronology of granitic rocks in the Erguna ductile shear zone.The deformed granitic rocks have experienced significant SE-trending dextral strike-slip shearing.Finite strain and kinematic vorticity in all deformed granitic rocks indicate that the deformation is characterized by simple sheardominated general shearing with S-L tectonites.Mineral deformation behaviors and quartz C-axis textures demonstrate that the deformed granitic rocks developed under greenschist to amphibolite facies conditions at deformation temperatures ranging from 450 to 550℃.New LA-ICP-MS zircon U-Pb ages indicate that these granitic rocks were formed in Early Triassic(~248.6 Ma)and Early Cretaceous(~136.7 Ma).All the evidence indicates that this deformation may have occurred in Early Cretaceous and was related to the compression resulting from the final closure of the Mongol-Okhotsk Ocean.展开更多
The Longgang Block is one of the most important parts of the eastern North China Craton,characterized by extensive Late Neoarchean(~2.5 Ga)granulite facies metamorphism.However,it remains uncertain whether it was infl...The Longgang Block is one of the most important parts of the eastern North China Craton,characterized by extensive Late Neoarchean(~2.5 Ga)granulite facies metamorphism.However,it remains uncertain whether it was influenced by Paleoproterozoic magmatism-metamorphism.The authors provide a comprehensive analysis of amphibolite in Laojinchang area,southern Jilin Province,through petrographic,geochemical,mineralogical,and zircon dating.The main findings are as follows:The mineral assemblage of amphibolite is Hb+Pl+Cpx+Bi+Kf+Q,characteristic of amphibolite facies;zircon U-Pb dating indicates that the metamorphic age of amphibolite is 1834±33 Ma;the amphibolite has geochemical characteristics of calcium alkaline,with depletion of Nb,Ta,Ti and P.The plagioclase in the amphibolite is oligoclase,belonging to acidic plagioclase.It is speculated that the protolith of the amphibolite is diorite;using geothermobarometer,the peak metamorphic P-T conditions of amphibolite are determined to be 536–593℃/3.4–5.0 kbar,and the post-peak conditions are 429–566℃/1.3–3.1 kbar.The above results indicate that the Paleoproterozoic metamorphism has been superimposed on Longgang Block,linked to a new orogenic event on the northern edge of North China Craton.展开更多
The Jiutai area is tectonically situated at the eastern segment of the Central Asian Orogenic Belt(CAOB) and is close to the North China Craton(NCC) to the south, serving as an ideal place to investigations of the clo...The Jiutai area is tectonically situated at the eastern segment of the Central Asian Orogenic Belt(CAOB) and is close to the North China Craton(NCC) to the south, serving as an ideal place to investigations of the closure of the PaleoAsian Ocean(PAO). Sandstone samples collected from the Yangjiagou Formation and the Lujiatun Formation in this area have been studied in detail in terms of petrology, geochronology and geochemistry. The maximum depositional time of the Yangjiagou and Lujiatun formations has been constrained to early Middle Triassic(ca. 245 Ma) and middle Late Triassic(ca. 219 Ma), respectively. The Yangjiagou Formation, with a major provenance of dissected island arcs, is dominantly composed of Phanerozoic sediments from Northeastern China(NE China) massifs. The Lujiatun Formation, with major sediments from active continental margins, has a relatively larger proportion of Precambrian sediments, in which the ~1.85 Ga and ~2.5 Ga sediments are typical of the crystalline basements of the NCC and NE China massifs, which were uplifted and eroded during the closure of the PAO. Besides, both formations show the enrichment in LREEs and the depletion in HREEs, the common Eu negative anomalies, and trace element contents similar to that of the upper continental crust. Based on the provenance analysis of these two formations, the final closure time of the PAO in this area is constrained as from the early Middle Triassic(ca. 245 Ma) to the middle Late Triassic(ca. 219 Ma).展开更多
The calcite mylonites in the Xar Moron-Changchun shear zone show a significance dextral shearing characteristics. The asymmetric(σ-structure) calcite/quartz grains or aggregates, asymmetry of calcite c-axes fabric di...The calcite mylonites in the Xar Moron-Changchun shear zone show a significance dextral shearing characteristics. The asymmetric(σ-structure) calcite/quartz grains or aggregates, asymmetry of calcite c-axes fabric diagrams and the oblique foliation of recrystallized calcite grains correspond to a top-to-E shearing. Mineral deformation behaviors, twin morphology, C-axis EBSD fabrics, and quartz grain size-frequency diagrams demonstrate that the ductile shear zone was developed under conditions of greenschist facies, with the range of deformation temperatures from 200 to 300°C. These subgrains of host grains and surrounding recrystallized grains, strong undulose extinction, and slightly curved grain boundaries are probably results of intracrystalline deformation and dynamic recrystallization implying that the deformation took place within the dislocation-creep regime at shallow crustal levels. The calculated paleo-strain rates are between 10-7.87s-1 and 10-11.49s-1 with differential stresses of 32.63-63.94 MPa lying at the higher bound of typical strain rates in shear zones at crustal levels, and may indicate a relatively rapid deformation. The S-L-calcite tectonites have undergone a component of uplift which led to subhorizontal lifting in an already non-coaxial compressional deformation regime with a bulk pure shear-dominated general shear. This E-W large-scale dextral strike-slip movement is a consequence of the eastward extrusion of the Xing’an-Mongolian Orogenic Belt, and results from far-field forces associated with Late Triassic convergence domains after the final closure of the Paleo-Asian Ocean.展开更多
There is a controversy regarding the amalgamation of Xing’an and Songnen Blocks along the Hegenshan-Heihe Suture(HHS)in the eastern Central Asian Orogenic Belt(CAOB).To solve this problem,we performed detailed study ...There is a controversy regarding the amalgamation of Xing’an and Songnen Blocks along the Hegenshan-Heihe Suture(HHS)in the eastern Central Asian Orogenic Belt(CAOB).To solve this problem,we performed detailed study on the granites from the Zhangdaqi area,adjacent to the north of the HHS in the northern part of the Great Xing’an Range,NE China.Geochemically,the granites in the study area are metaluminous-weak peraluminous and high-K calc-alkaline series.Trace elements of the granites show that LREEs are relatively enriched,while HREEs are relatively deficient and obvious REE fractionation.The granites are characterized by obvious negative Eu anomalies,meanwhile,they are relatively enriched in Rb,K,Th and depleted in Ba,Nb,Sr,P,Ti.All the geochemical features suggest that the granites in the Zhangdaqi area are aluminum A-type granites.The zircon LA-ICP-MS U-Pb ages of these granites are 294-298 Ma,indicating that they formed in the Early Permian.These granites also have positiveεHf(t)values(8.4-14.2)and a relatively young two-stage model age between 449 Ma and 977 Ma,implying that the magma was derived from the re-melting of the Early Paleozoic-Neoproterozoic juvenile crust.Combined with geochemical characteristics(Nb/Ta ratios of 9.0-22.2,and Zr/Hf ratios of 52.3-152.0),we believe that the magmatic source area is a mixture of partial melting of the lower crust and depleted mantle.A-type granites and bimodal volcanic rocks along the Hegenshan-Heihe Suture formed during the Late Carboniferous-Early Permian,indicating that the HHS between Xing’an and Songnen Blocks closed in the late EarlyCarboniferous.Subsequently,the Zhangdaqi area was in a post-orogenic extensional environment from Late Carboniferous to Early Permian and resulted in the formation of the A-type granites.展开更多
The NE-striking Jiamusi-Yitong fault zone(JYFZ) is the most important branch in the northern segment of the Tancheng-Lujiang fault zone. The precise shearing time of its large-scale sinistral strike-slip has yet to de...The NE-striking Jiamusi-Yitong fault zone(JYFZ) is the most important branch in the northern segment of the Tancheng-Lujiang fault zone. The precise shearing time of its large-scale sinistral strike-slip has yet to determined and must be constrained. Detailed field investigations and comprehensive analyses show that strike-slip faults or ductile shear belts exist as origination structures along the western region of Yitong Graben. The strike of the shear belts trend to the NE-SW with steep mylonitic foliation. The zircon U-Pb dating result for the granite was 264.1±1 Ma in the ductile shear belt of the JYFZ. The microstructural observation(rotated feldspar porphyroclasts, S-C fabrics, and quartz c-axis fabrics, etc.) demonstrated the sinistral shearing of the ductile shear zones. Moreover, the recrystallized quartz types show a transitional stage of the subgrain rotation toward the recrystallization of the grain boundary migration(SR-GBM). Therefore, we suggest that the metamorphic grade of the shear zone in the ductile shear zones should have reached high greenschist facies conditions, and the deformation temperatures should approximately 450-500°C, which is obviously higher than the blocking temperature of muscovite(300-400°C). Hence, the ^40Ar/^39Ar isochron age of muscovite from ductile shear zones should be a cooling age(162.7±1 Ma). We infer that the sinistral strike-slipping event at the JYFZ occurred in the late Jurassic period, and it was further inferred from the ages of the main geological events in this region that the second sinistral strike-slip age of the Tancheng-Lujiang fault zone occurred during the period of tectonic movements in the Circum-Pacific tectonic domain. This discovery also indicates the age of the Tancheng-Lujiang fault zone that stretches to northeastern China. The initiation of the JYFZ in the late Jurassic is related to the speed and direction of oblique subduction of the west Pacific Plate under the Eurasian continent and is responsible for collision during the Jurassic period.展开更多
基金Supported by the National Key R&D Program(No.2017YFC0601401-03).
文摘The Erguna ductile shear zone is situated in the Erguna Massif,which has been exposed along the eastern bank of the Erguna River in northeastern China.The authors present comprehensive study results on the macro-and micro-structures,finite strain and kinematic vorticity,quartz electron backscatter diffraction(EBSD)fabrics,and geochronology of granitic rocks in the Erguna ductile shear zone.The deformed granitic rocks have experienced significant SE-trending dextral strike-slip shearing.Finite strain and kinematic vorticity in all deformed granitic rocks indicate that the deformation is characterized by simple sheardominated general shearing with S-L tectonites.Mineral deformation behaviors and quartz C-axis textures demonstrate that the deformed granitic rocks developed under greenschist to amphibolite facies conditions at deformation temperatures ranging from 450 to 550℃.New LA-ICP-MS zircon U-Pb ages indicate that these granitic rocks were formed in Early Triassic(~248.6 Ma)and Early Cretaceous(~136.7 Ma).All the evidence indicates that this deformation may have occurred in Early Cretaceous and was related to the compression resulting from the final closure of the Mongol-Okhotsk Ocean.
基金Supported by projects of the National Natural Science Foundation of China(Nos.42172213,42372255).
文摘The Longgang Block is one of the most important parts of the eastern North China Craton,characterized by extensive Late Neoarchean(~2.5 Ga)granulite facies metamorphism.However,it remains uncertain whether it was influenced by Paleoproterozoic magmatism-metamorphism.The authors provide a comprehensive analysis of amphibolite in Laojinchang area,southern Jilin Province,through petrographic,geochemical,mineralogical,and zircon dating.The main findings are as follows:The mineral assemblage of amphibolite is Hb+Pl+Cpx+Bi+Kf+Q,characteristic of amphibolite facies;zircon U-Pb dating indicates that the metamorphic age of amphibolite is 1834±33 Ma;the amphibolite has geochemical characteristics of calcium alkaline,with depletion of Nb,Ta,Ti and P.The plagioclase in the amphibolite is oligoclase,belonging to acidic plagioclase.It is speculated that the protolith of the amphibolite is diorite;using geothermobarometer,the peak metamorphic P-T conditions of amphibolite are determined to be 536–593℃/3.4–5.0 kbar,and the post-peak conditions are 429–566℃/1.3–3.1 kbar.The above results indicate that the Paleoproterozoic metamorphism has been superimposed on Longgang Block,linked to a new orogenic event on the northern edge of North China Craton.
基金financially co-supported by the National Key R&D Program of China (Grant No. 2017YFC0601401 and 2017YFC0601300-01)Self-determined Foundation of Key Laboratory of Mineral Resources Evaluation in Northeast Asia, Ministry of Natural Resources, China (Grant No. DBY–ZZ–18–09)
文摘The Jiutai area is tectonically situated at the eastern segment of the Central Asian Orogenic Belt(CAOB) and is close to the North China Craton(NCC) to the south, serving as an ideal place to investigations of the closure of the PaleoAsian Ocean(PAO). Sandstone samples collected from the Yangjiagou Formation and the Lujiatun Formation in this area have been studied in detail in terms of petrology, geochronology and geochemistry. The maximum depositional time of the Yangjiagou and Lujiatun formations has been constrained to early Middle Triassic(ca. 245 Ma) and middle Late Triassic(ca. 219 Ma), respectively. The Yangjiagou Formation, with a major provenance of dissected island arcs, is dominantly composed of Phanerozoic sediments from Northeastern China(NE China) massifs. The Lujiatun Formation, with major sediments from active continental margins, has a relatively larger proportion of Precambrian sediments, in which the ~1.85 Ga and ~2.5 Ga sediments are typical of the crystalline basements of the NCC and NE China massifs, which were uplifted and eroded during the closure of the PAO. Besides, both formations show the enrichment in LREEs and the depletion in HREEs, the common Eu negative anomalies, and trace element contents similar to that of the upper continental crust. Based on the provenance analysis of these two formations, the final closure time of the PAO in this area is constrained as from the early Middle Triassic(ca. 245 Ma) to the middle Late Triassic(ca. 219 Ma).
基金financially co-supported by the National Key R&D Program of China (Grant No.2017YFC0601401 and 2017YFC0601300-01)the National Natural Science Foundation of China (Grant no. 41602211 and 41230206)
文摘The calcite mylonites in the Xar Moron-Changchun shear zone show a significance dextral shearing characteristics. The asymmetric(σ-structure) calcite/quartz grains or aggregates, asymmetry of calcite c-axes fabric diagrams and the oblique foliation of recrystallized calcite grains correspond to a top-to-E shearing. Mineral deformation behaviors, twin morphology, C-axis EBSD fabrics, and quartz grain size-frequency diagrams demonstrate that the ductile shear zone was developed under conditions of greenschist facies, with the range of deformation temperatures from 200 to 300°C. These subgrains of host grains and surrounding recrystallized grains, strong undulose extinction, and slightly curved grain boundaries are probably results of intracrystalline deformation and dynamic recrystallization implying that the deformation took place within the dislocation-creep regime at shallow crustal levels. The calculated paleo-strain rates are between 10-7.87s-1 and 10-11.49s-1 with differential stresses of 32.63-63.94 MPa lying at the higher bound of typical strain rates in shear zones at crustal levels, and may indicate a relatively rapid deformation. The S-L-calcite tectonites have undergone a component of uplift which led to subhorizontal lifting in an already non-coaxial compressional deformation regime with a bulk pure shear-dominated general shear. This E-W large-scale dextral strike-slip movement is a consequence of the eastward extrusion of the Xing’an-Mongolian Orogenic Belt, and results from far-field forces associated with Late Triassic convergence domains after the final closure of the Paleo-Asian Ocean.
基金supported by China Geological Survey Project (Grant NO. DD20160047-02, DD20190042-03)National Key Research and Development Program (Grant NO. 2017YFC0601300-01, 2017YFC0601401, 2017YFC 0601305-02)Qingdao Leading innovation talents project (19–3–2–19–zhc)
文摘There is a controversy regarding the amalgamation of Xing’an and Songnen Blocks along the Hegenshan-Heihe Suture(HHS)in the eastern Central Asian Orogenic Belt(CAOB).To solve this problem,we performed detailed study on the granites from the Zhangdaqi area,adjacent to the north of the HHS in the northern part of the Great Xing’an Range,NE China.Geochemically,the granites in the study area are metaluminous-weak peraluminous and high-K calc-alkaline series.Trace elements of the granites show that LREEs are relatively enriched,while HREEs are relatively deficient and obvious REE fractionation.The granites are characterized by obvious negative Eu anomalies,meanwhile,they are relatively enriched in Rb,K,Th and depleted in Ba,Nb,Sr,P,Ti.All the geochemical features suggest that the granites in the Zhangdaqi area are aluminum A-type granites.The zircon LA-ICP-MS U-Pb ages of these granites are 294-298 Ma,indicating that they formed in the Early Permian.These granites also have positiveεHf(t)values(8.4-14.2)and a relatively young two-stage model age between 449 Ma and 977 Ma,implying that the magma was derived from the re-melting of the Early Paleozoic-Neoproterozoic juvenile crust.Combined with geochemical characteristics(Nb/Ta ratios of 9.0-22.2,and Zr/Hf ratios of 52.3-152.0),we believe that the magmatic source area is a mixture of partial melting of the lower crust and depleted mantle.A-type granites and bimodal volcanic rocks along the Hegenshan-Heihe Suture formed during the Late Carboniferous-Early Permian,indicating that the HHS between Xing’an and Songnen Blocks closed in the late EarlyCarboniferous.Subsequently,the Zhangdaqi area was in a post-orogenic extensional environment from Late Carboniferous to Early Permian and resulted in the formation of the A-type granites.
基金funded by the National Key R&D Program of China (Grant No. 2017YFC0601300–01)973 Program (Grant 2013CB429802)NSFC (Grant 41102140,41303175)
文摘The NE-striking Jiamusi-Yitong fault zone(JYFZ) is the most important branch in the northern segment of the Tancheng-Lujiang fault zone. The precise shearing time of its large-scale sinistral strike-slip has yet to determined and must be constrained. Detailed field investigations and comprehensive analyses show that strike-slip faults or ductile shear belts exist as origination structures along the western region of Yitong Graben. The strike of the shear belts trend to the NE-SW with steep mylonitic foliation. The zircon U-Pb dating result for the granite was 264.1±1 Ma in the ductile shear belt of the JYFZ. The microstructural observation(rotated feldspar porphyroclasts, S-C fabrics, and quartz c-axis fabrics, etc.) demonstrated the sinistral shearing of the ductile shear zones. Moreover, the recrystallized quartz types show a transitional stage of the subgrain rotation toward the recrystallization of the grain boundary migration(SR-GBM). Therefore, we suggest that the metamorphic grade of the shear zone in the ductile shear zones should have reached high greenschist facies conditions, and the deformation temperatures should approximately 450-500°C, which is obviously higher than the blocking temperature of muscovite(300-400°C). Hence, the ^40Ar/^39Ar isochron age of muscovite from ductile shear zones should be a cooling age(162.7±1 Ma). We infer that the sinistral strike-slipping event at the JYFZ occurred in the late Jurassic period, and it was further inferred from the ages of the main geological events in this region that the second sinistral strike-slip age of the Tancheng-Lujiang fault zone occurred during the period of tectonic movements in the Circum-Pacific tectonic domain. This discovery also indicates the age of the Tancheng-Lujiang fault zone that stretches to northeastern China. The initiation of the JYFZ in the late Jurassic is related to the speed and direction of oblique subduction of the west Pacific Plate under the Eurasian continent and is responsible for collision during the Jurassic period.
基金supported by National Natural Science Foundation of China (Grant No. 40739905)Specialized Research Fund for the Doctoral Program of Higher Education (Grant No. 200801830041)+2 种基金Science and Technology Project of Sinopec (Grant No. G0800-06-ZS-327)China Scholarship Council (Grant No. 2008617114)the Opening Foundation of the State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration
