The Dharwar Craton(DC)in India consists of three distinct Archean blocks.Previous research suggests that the Central Dharwar Block(CDB)experienced a geological history(3.3-2.5 Ga)comparable to the Western Dharwar Crat...The Dharwar Craton(DC)in India consists of three distinct Archean blocks.Previous research suggests that the Central Dharwar Block(CDB)experienced a geological history(3.3-2.5 Ga)comparable to the Western Dharwar Craton(WDC).However,3.0-2.7 Ga geological records are missed in the CDB.This study identified the 2.85 Ga gabbroic xenoliths within the Closepet batholith in the CDB.The~2.85 Ga inherited zircons and zircon Hf model ages in CDB further provide evidence for this significant magmatic event.The gabbroic xenoliths are characterized by E-MORB REE patterns and Nb,Ta,and Ti depletions,together with high radiogenic isotopic signatures,including zircon Hf(ε_(Hf)(t)_(min)=-3.2),whole-rock Nd(ε_(Nd)(t)=-0.8-0.7),and Pb isotopes(κ=4.9-7.9),indicating derivation from a slightly enriched mantle source.Additionally,they have high Nb(4.41 to 4.73 ppm),low Ti/V(23.4 to 22.5),and elevated Th/Yb(0.38 to 0.61).All these suggest a subduction-related back-arc basin setting.Coupled with widespread early Neoarchean subduction-related igneous rocks in the DC,the 2.85 Ga gabbroic magmatism signifies that the DC had transitioned into a tectonic stage dominated by lateral movement of continental blocks around 2.85 Ga,corresponding to global~2.85 Ga magmatic events.展开更多
The Dharwar Craton in India,as one of the oldest cratons in the world,preserves key information of early continental crust evolution.However,a~3.0 Ga tectonothermal event was previously recognized only in the Western ...The Dharwar Craton in India,as one of the oldest cratons in the world,preserves key information of early continental crust evolution.However,a~3.0 Ga tectonothermal event was previously recognized only in the Western Dharwar Craton,and the coeval tectono-thermal event has been rarely reported in the Central Dharwar Block.In this study,zircon U-Pb dating of the gabbroic diorite xenolith from Neoarchean Closepet batholith yields an age of 2995±13 Ma,confirming the~3.0 Ga magmatism in the Central Dharwar Block.The gabbroic diorite is characterized by low SiO_(2)(52.62%-53.42%)and high MgO(5.38%-5.42%),Cr(48-70)×10^(-6),and Ni(115-124)×10^(-6),with relative enrichment in LILEs and LREE and depletion in HFSEs as well as negative Nd(ε_(Nd)(t)=−4.8 to−4.5)and Hf(ε_(Hf)(t)=−6.64 to−2.36)isotopes,indicating an enriched mantle source.Furthermore,geochemical signatures of zircon,clinopyroxene,and hornblende indicate that this magmatism occurred in an environment with water enrichment and high oxygen fugacity,similar to the island-arc setting,suggesting that the gabbroic diorite was produced by partial melting of enriched mantle source under a subduction zone.Additionally,the mafic magmatism in the Dharwar Craton evidently decreased from 3.2 to 3.0 Ga,accompanied by a transition of crustal components from Na-rich to K-rich,implying that a significant tectonic regime shift had already happened in the Dharwar Craton around~3.0 Ga.Considering the enriched isotopic composition of the gabbroic diorite and previous studies on the Dharwar Craton from 3.2 to 3.0 Ga,it suggests that the Dharwar Craton might have undergone a vertical-to-lateral tectonic transition beginning at~3.2 Ga and lasting until~3.0 Ga,and the subduction related to the plate tectonic probably started in a specific scale.展开更多
Introduction The rectangular block of Proterozoic formation lying between north of the Singhbhum Mobile Belt(SMB,2.3-2.4 Ga,Saha 1994),Neogene sediments of the Bengal basin and the Quaternary-Recent alluvium of the Ganga
In the present era,the competitive producers are forced to use maximally newer advanced technology and its effective fast implementation using various available tools for synthesis of new product requirement.Use of c...In the present era,the competitive producers are forced to use maximally newer advanced technology and its effective fast implementation using various available tools for synthesis of new product requirement.Use of current state of art computer aided technology supports the creation of flexible assemblies and their built up though unified modular approach.The design of robotic mechanism is a complex process involving geometric,kinematic,singularity analyses during its synthesis phase.The present work is aimed at the effective utilization of CAx system Pro/Engineer tools for creation,ease in modifi-cation and analysis of spatial parallel manipulator.Three degrees of freedom of 3-PRS parallel manipulator is obtained using mobility analysis.Parallel manipulator with 3-DOF with 3-PRS configuration is investigated.The kinematics simulation of the robot is carried out using mechanism simulation and compared with closed form solutions.The concept of reachable,orientation and dexterous workspace is expressed.Tool tip coordinates obtained through simulation are plotted for workspace development.Inner and outer workspace boundaries are developed and analyzed for four different cases to understand the problem of interior singularity within workspace.展开更多
基金financially supported by the National Natural Science Foundations of China(41890831,41421002)the MOST Special Fund from the State Key Laboratory of Continental Dynamics,Northwest University(201210133)。
文摘The Dharwar Craton(DC)in India consists of three distinct Archean blocks.Previous research suggests that the Central Dharwar Block(CDB)experienced a geological history(3.3-2.5 Ga)comparable to the Western Dharwar Craton(WDC).However,3.0-2.7 Ga geological records are missed in the CDB.This study identified the 2.85 Ga gabbroic xenoliths within the Closepet batholith in the CDB.The~2.85 Ga inherited zircons and zircon Hf model ages in CDB further provide evidence for this significant magmatic event.The gabbroic xenoliths are characterized by E-MORB REE patterns and Nb,Ta,and Ti depletions,together with high radiogenic isotopic signatures,including zircon Hf(ε_(Hf)(t)_(min)=-3.2),whole-rock Nd(ε_(Nd)(t)=-0.8-0.7),and Pb isotopes(κ=4.9-7.9),indicating derivation from a slightly enriched mantle source.Additionally,they have high Nb(4.41 to 4.73 ppm),low Ti/V(23.4 to 22.5),and elevated Th/Yb(0.38 to 0.61).All these suggest a subduction-related back-arc basin setting.Coupled with widespread early Neoarchean subduction-related igneous rocks in the DC,the 2.85 Ga gabbroic magmatism signifies that the DC had transitioned into a tectonic stage dominated by lateral movement of continental blocks around 2.85 Ga,corresponding to global~2.85 Ga magmatic events.
基金funded by the National Science Foundation of China(grant Nos.41890831 and 41772189)the Most Special Fund from State Key Laboratory of Continental Dynamics,Northwest University,Xi’an,China(grant No.201210133).
文摘The Dharwar Craton in India,as one of the oldest cratons in the world,preserves key information of early continental crust evolution.However,a~3.0 Ga tectonothermal event was previously recognized only in the Western Dharwar Craton,and the coeval tectono-thermal event has been rarely reported in the Central Dharwar Block.In this study,zircon U-Pb dating of the gabbroic diorite xenolith from Neoarchean Closepet batholith yields an age of 2995±13 Ma,confirming the~3.0 Ga magmatism in the Central Dharwar Block.The gabbroic diorite is characterized by low SiO_(2)(52.62%-53.42%)and high MgO(5.38%-5.42%),Cr(48-70)×10^(-6),and Ni(115-124)×10^(-6),with relative enrichment in LILEs and LREE and depletion in HFSEs as well as negative Nd(ε_(Nd)(t)=−4.8 to−4.5)and Hf(ε_(Hf)(t)=−6.64 to−2.36)isotopes,indicating an enriched mantle source.Furthermore,geochemical signatures of zircon,clinopyroxene,and hornblende indicate that this magmatism occurred in an environment with water enrichment and high oxygen fugacity,similar to the island-arc setting,suggesting that the gabbroic diorite was produced by partial melting of enriched mantle source under a subduction zone.Additionally,the mafic magmatism in the Dharwar Craton evidently decreased from 3.2 to 3.0 Ga,accompanied by a transition of crustal components from Na-rich to K-rich,implying that a significant tectonic regime shift had already happened in the Dharwar Craton around~3.0 Ga.Considering the enriched isotopic composition of the gabbroic diorite and previous studies on the Dharwar Craton from 3.2 to 3.0 Ga,it suggests that the Dharwar Craton might have undergone a vertical-to-lateral tectonic transition beginning at~3.2 Ga and lasting until~3.0 Ga,and the subduction related to the plate tectonic probably started in a specific scale.
文摘Introduction The rectangular block of Proterozoic formation lying between north of the Singhbhum Mobile Belt(SMB,2.3-2.4 Ga,Saha 1994),Neogene sediments of the Bengal basin and the Quaternary-Recent alluvium of the Ganga
文摘In the present era,the competitive producers are forced to use maximally newer advanced technology and its effective fast implementation using various available tools for synthesis of new product requirement.Use of current state of art computer aided technology supports the creation of flexible assemblies and their built up though unified modular approach.The design of robotic mechanism is a complex process involving geometric,kinematic,singularity analyses during its synthesis phase.The present work is aimed at the effective utilization of CAx system Pro/Engineer tools for creation,ease in modifi-cation and analysis of spatial parallel manipulator.Three degrees of freedom of 3-PRS parallel manipulator is obtained using mobility analysis.Parallel manipulator with 3-DOF with 3-PRS configuration is investigated.The kinematics simulation of the robot is carried out using mechanism simulation and compared with closed form solutions.The concept of reachable,orientation and dexterous workspace is expressed.Tool tip coordinates obtained through simulation are plotted for workspace development.Inner and outer workspace boundaries are developed and analyzed for four different cases to understand the problem of interior singularity within workspace.
