The North China Craton(NCC)is a classic case of the destruction of an ancient craton,in that it records the loss of more than 100 km of ancient refractory lithospheric mantle during the Mesozoic(e.g.,Menzies et al.,19...The North China Craton(NCC)is a classic case of the destruction of an ancient craton,in that it records the loss of more than 100 km of ancient refractory lithospheric mantle during the Mesozoic(e.g.,Menzies et al.,1993).This展开更多
In the present study, the major and trace element compositions, as well as Sr, Nd isotopic compositions and K-Ar age data in mafic dikes from Hainan Island, China, have been analyzed. Whole-rock K-Ar dating yielded a ...In the present study, the major and trace element compositions, as well as Sr, Nd isotopic compositions and K-Ar age data in mafic dikes from Hainan Island, China, have been analyzed. Whole-rock K-Ar dating yielded a magmatic duration of 61-98 Ma for mafic dikes. Mafic dikes have a very high concentration of incompatible elements, for example, Ba, Rb, Sr, K, rare earth elements, and especially light rare earth elements (LREE), and negative anomalies of Nb, Ta, and Ti in the normalized trace element patterns. The initial 87Sr/86Sr ratios and εSr(t) of the mafic dikes are 0.70634- 0.71193 and +27.7 to +112.2, respectively. In the 87Sr/86Sr versus εNd(t) diagram, the Hainan Island mafic dikes plot between fields for depleted mantle and enriched mantle type 2. All these characteristics show that the mantle (source region) of mafic dikes in this area experienced metasomatism by fluids relatively enriched in LREE and large ion lithophUe elements. The genesis of Hainan Island mafic dikes is explained as a result of the mixing of asthenospheric mantle with lithospheric mantle that experienced metasomatism by the subduction of the Pacific Plate. This is different from the Hainan Island Cenozoic basalts mainly derived from depleted asthenospheric mantle, and possibly, minor metasomatised lithospheric mantle. This study suggests that the Mesozoic and Cenozoic lithospheric revolutions in Hainan Island can be divided into three stages: (1) the compression orogenesis stage before 98 Ma. The dominant factor during this stage is the subduction of the ancient Pacific Plate beneath this area. The lithospheric mantle changed into enriched mantle type 2 by metasomatism; (2) the thinning and extension stage during 61-98 Ma. The dominant factor during this stage is that the asthenospheric mantle invaded and corroded the lithospheric mantle; and (3) the large-scale thinning and extension stage after 61 Ma. The large-scale asthenospheric upwelling results in the strong erupting of Cenozoic basalts, large-scale thinning of the lithosphere, the southward translating and counterclockwise rotating of Hainan Island, and the opening of the South China Sea.展开更多
Fabrics of an Archean mélange belt in the Zanhuang Complex of the North China Craton(NCC)were intruded by mafic dikes and a granite pluton(Deng et al.,2013;Wang et al.,2013).Igneous zircons from an undefomed
Based on K-Ar isotope analyses, Mesozoic mafic (and alkali ultramafic) dikes from western and eastern Shandong Province, China, are dated at 88.2±1.70 Ma to 169.5±3.7 Ma with the majority of ages ranging fro...Based on K-Ar isotope analyses, Mesozoic mafic (and alkali ultramafic) dikes from western and eastern Shandong Province, China, are dated at 88.2±1.70 Ma to 169.5±3.7 Ma with the majority of ages ranging from 90 Ma to 140 Ma. The emplacement of the dikes suggests a major Yanshanian (Cretaceous) crustal extension in Shandong province. Together with other available age data, this study suggests four periods of crustal extension at about 80 Ma, 100 Ma, 120 Ma and 140 Ma, respectively. Besides the effect of collapse of the Yanshanian orogenic belt on the emplacement of the mafic dikes in Shandong in the Cretaceous, the mantle plume and the extensive left-lateral advection and extension of the Tanlu fault also have controlled the crustal extension and the emplacement of the mafic dikes in eastern Shandong and western Shandong, respectively.展开更多
Late Mesozoic magmatism in southeastern China has been widely considered to be related to the subduction of the Paleo-Pacific Plate.However,it remains controversial whether mafic rocks are derived from the lithosphere...Late Mesozoic magmatism in southeastern China has been widely considered to be related to the subduction of the Paleo-Pacific Plate.However,it remains controversial whether mafic rocks are derived from the lithosphere or the asthenosphere.Here we present a comprehensive study on mafic dikes from Fujian Province in southeastern China,aiming to understand their source.Two types of mafic rocks have been recognized based on their trace-element features.Type-Ⅰrocks show arc-like trace-elemental characteristics,while type-Ⅱrocks are distinguished by their relatively flat patterns in primitive-mantle-normalized trace-element diagram.Despite such differences between two types of rocks,these mafic dikes show two trends in the plots of^(87)Sr/^(86)Sr(i)versus La/Nb,which can be explained by the influences of crustal contamination and melt-lithospheric mantle interaction,respectively.^(87)Sr/^(86)Sr(i),La/Nb,Sr/Y and Zr/Y ratios of type-I rocks are significantly correlated to the thickness of the underlying lithosphere,and the signals of lithosphere are clearer with increasing lithospheric thickness.This highlights the important influences of melt-lithosphere interaction during their formation.Such observations also indicate that these mafic rocks are more likely to have been originated from the asthenosphere rather than the lithospheric mantle.展开更多
We studied an Archean mafic dike in the TransNorth China Orogen of the North China Craton, which has a magmatic age of 2701 ± 83 Ma and is currently the oldest mafic dike in the North China Craton. Such an old di...We studied an Archean mafic dike in the TransNorth China Orogen of the North China Craton, which has a magmatic age of 2701 ± 83 Ma and is currently the oldest mafic dike in the North China Craton. Such an old dike is extremely rare in the world. The presence of mafic dikes indicates that the North China Craton was in a tensional tectonic environment at 2.7 Ga. Geochemical characteristics reveal that this mafic dike belongs to continental tholeiitic basalt. Results from Hf isotope analysis reveal that the mafic dike originates from a depleted mantle. The plate assembly in the North China landmass was realized during the Archean era(2.7 Ga), and a thick and stable continental crust was formed. Therefore, the first cratonization of the North China Craton was completed before 2.7 Ga. The intrusion of the 2.7-Ga-old mafic dike from the deep lithospheric mantle of the continent indicates that the North China Craton has undergone a period of extensional tectonic activity. This event marks a significant extensional event that occurred after the cratonization of the North China Craton.展开更多
It is well established that Cretaceous magmatism in the South China Block(SCB)is related to the Paleo-Pacific subduction.However,the starting time and the associated deep crust-mantle processes are still debatable.Maf...It is well established that Cretaceous magmatism in the South China Block(SCB)is related to the Paleo-Pacific subduction.However,the starting time and the associated deep crust-mantle processes are still debatable.Mafic dike swarms carry important information on the deep earth(including mantle)geodynamics and geochemical evolution.In the Jiangnan Orogen(South China).there is no information on whether the Mesozoic magmatic activities in this region are also directly related to the Pacific subduction or not.In this study,we present detailed zircon U-Pb geochronological,wholerock element and Sr-Nd isotope data for Early Cretaceous Tuanshanbei dolerite dikes,and provide new constraints on the condition of the lithospheric mantle and mantle dynamics of the SCB during that time.LA-ICP-MS zircon U-Pb dating suggests that this dolerite erupted in the Early Cretaceous(~145 Ma).All samples have alkaline geochemical affinities with K_(2)O+Na_(2)O=3.11-4.04 wt%,K_(2)O/Na_(2)O=0.50-0.72,and Mg^(#)=62.24-65.13.They are enriched in LILE but depleted in HFSE with higher initial^(87)Sr/^(86)Sr ratio(0.706896-0.714743)and lower ε_(Nd)(t)(-2.61 to-1.67).They have high Nb/U,Nb/La,La/Sm and Rb/Sr,and low La/Nb,La/Ta,Ce/Pb,Ba/Rb,Tb/Yb and Gd/Yb ratios.Such geochemical signatures suggest that the fractional crystallization is obvious but crustal contamination play a negligible role during magmatic evolution.Tuanshanbei dolerite were most likely derived from low-degree(2%-5%)partial melting of a phlogopite-bearing mantle material consisted of~85% spinel peridotite and~15% garnet peridotite previously metasomatized by asthenospherederived fluids/melts with minor subduction-derived fluids/melts.Slab-rollback generally lead to the upwelling of the hot asthenosphere.The upwelling of asthenosphere consuming the lithospheric mantle by thermo-mechanical-chemical erosion.The lithospheric mantle may have partially melted due to the heating by the upwelling asthenosphere and lithospheric extension.It is inferred that the Tuanshanbei dolerite might be associated with the initial slab rollback and corresponding lithospheric extension occurred potentially at ca.145 Ma.展开更多
Mafic dike swarms are well-developed within the Tethyan Himalaya,southern Tibet,in response to the breakup of Gondwana supercontinent,seafloor spreading of the Tethyan Ocean,and forearc hyperextension during the
文摘The North China Craton(NCC)is a classic case of the destruction of an ancient craton,in that it records the loss of more than 100 km of ancient refractory lithospheric mantle during the Mesozoic(e.g.,Menzies et al.,1993).This
基金supported by the State Key Program of National Natural Science of China (Grant no.40634020)
文摘In the present study, the major and trace element compositions, as well as Sr, Nd isotopic compositions and K-Ar age data in mafic dikes from Hainan Island, China, have been analyzed. Whole-rock K-Ar dating yielded a magmatic duration of 61-98 Ma for mafic dikes. Mafic dikes have a very high concentration of incompatible elements, for example, Ba, Rb, Sr, K, rare earth elements, and especially light rare earth elements (LREE), and negative anomalies of Nb, Ta, and Ti in the normalized trace element patterns. The initial 87Sr/86Sr ratios and εSr(t) of the mafic dikes are 0.70634- 0.71193 and +27.7 to +112.2, respectively. In the 87Sr/86Sr versus εNd(t) diagram, the Hainan Island mafic dikes plot between fields for depleted mantle and enriched mantle type 2. All these characteristics show that the mantle (source region) of mafic dikes in this area experienced metasomatism by fluids relatively enriched in LREE and large ion lithophUe elements. The genesis of Hainan Island mafic dikes is explained as a result of the mixing of asthenospheric mantle with lithospheric mantle that experienced metasomatism by the subduction of the Pacific Plate. This is different from the Hainan Island Cenozoic basalts mainly derived from depleted asthenospheric mantle, and possibly, minor metasomatised lithospheric mantle. This study suggests that the Mesozoic and Cenozoic lithospheric revolutions in Hainan Island can be divided into three stages: (1) the compression orogenesis stage before 98 Ma. The dominant factor during this stage is the subduction of the ancient Pacific Plate beneath this area. The lithospheric mantle changed into enriched mantle type 2 by metasomatism; (2) the thinning and extension stage during 61-98 Ma. The dominant factor during this stage is that the asthenospheric mantle invaded and corroded the lithospheric mantle; and (3) the large-scale thinning and extension stage after 61 Ma. The large-scale asthenospheric upwelling results in the strong erupting of Cenozoic basalts, large-scale thinning of the lithosphere, the southward translating and counterclockwise rotating of Hainan Island, and the opening of the South China Sea.
文摘Fabrics of an Archean mélange belt in the Zanhuang Complex of the North China Craton(NCC)were intruded by mafic dikes and a granite pluton(Deng et al.,2013;Wang et al.,2013).Igneous zircons from an undefomed
文摘Based on K-Ar isotope analyses, Mesozoic mafic (and alkali ultramafic) dikes from western and eastern Shandong Province, China, are dated at 88.2±1.70 Ma to 169.5±3.7 Ma with the majority of ages ranging from 90 Ma to 140 Ma. The emplacement of the dikes suggests a major Yanshanian (Cretaceous) crustal extension in Shandong province. Together with other available age data, this study suggests four periods of crustal extension at about 80 Ma, 100 Ma, 120 Ma and 140 Ma, respectively. Besides the effect of collapse of the Yanshanian orogenic belt on the emplacement of the mafic dikes in Shandong in the Cretaceous, the mantle plume and the extensive left-lateral advection and extension of the Tanlu fault also have controlled the crustal extension and the emplacement of the mafic dikes in eastern Shandong and western Shandong, respectively.
基金financially supported by the National Natural Science Foundation of China(Nos.41672048,41802045)the State Key Laboratory for Mineral Deposits ResearchNanjing University(No.ZZKT-201908)。
文摘Late Mesozoic magmatism in southeastern China has been widely considered to be related to the subduction of the Paleo-Pacific Plate.However,it remains controversial whether mafic rocks are derived from the lithosphere or the asthenosphere.Here we present a comprehensive study on mafic dikes from Fujian Province in southeastern China,aiming to understand their source.Two types of mafic rocks have been recognized based on their trace-element features.Type-Ⅰrocks show arc-like trace-elemental characteristics,while type-Ⅱrocks are distinguished by their relatively flat patterns in primitive-mantle-normalized trace-element diagram.Despite such differences between two types of rocks,these mafic dikes show two trends in the plots of^(87)Sr/^(86)Sr(i)versus La/Nb,which can be explained by the influences of crustal contamination and melt-lithospheric mantle interaction,respectively.^(87)Sr/^(86)Sr(i),La/Nb,Sr/Y and Zr/Y ratios of type-I rocks are significantly correlated to the thickness of the underlying lithosphere,and the signals of lithosphere are clearer with increasing lithospheric thickness.This highlights the important influences of melt-lithosphere interaction during their formation.Such observations also indicate that these mafic rocks are more likely to have been originated from the asthenosphere rather than the lithospheric mantle.
基金supported by the open fund from the Key Laboratory of Deep-Earth Dynamics of Ministry of Natural Resources,Institute of Geology,Chinese Academy of Geological Sciences (Number J1901-16)the project of graduate education and teaching reform in Shanxi Province (Number 2021YJJG147)+3 种基金the teaching reform project"Geographic Modeling,Simulation and Visualization"established by Shanxi Normal University (Number2019JGXM-39)"The Research Start-up Fund of Shanxi Normal University for Dr.Peng Chong in 2016"(Number 0505/02070438)"The Research Start-up Fund of Shanxi Normal University for Dr.Liu Haiyan in 2017"(Number 0505/02070458)"The Research Fund for Outstanding Doctor in 2017"(Number 0503/02010168),established by the Education Department of Shanxi Province for Dr.Liu Haiyan。
文摘We studied an Archean mafic dike in the TransNorth China Orogen of the North China Craton, which has a magmatic age of 2701 ± 83 Ma and is currently the oldest mafic dike in the North China Craton. Such an old dike is extremely rare in the world. The presence of mafic dikes indicates that the North China Craton was in a tensional tectonic environment at 2.7 Ga. Geochemical characteristics reveal that this mafic dike belongs to continental tholeiitic basalt. Results from Hf isotope analysis reveal that the mafic dike originates from a depleted mantle. The plate assembly in the North China landmass was realized during the Archean era(2.7 Ga), and a thick and stable continental crust was formed. Therefore, the first cratonization of the North China Craton was completed before 2.7 Ga. The intrusion of the 2.7-Ga-old mafic dike from the deep lithospheric mantle of the continent indicates that the North China Craton has undergone a period of extensional tectonic activity. This event marks a significant extensional event that occurred after the cratonization of the North China Craton.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.42302235,41830211,42272100)Fundamental Research Funds for the Central Universities,Sun Yat-sen University(Grant No.23ptpy143)。
文摘It is well established that Cretaceous magmatism in the South China Block(SCB)is related to the Paleo-Pacific subduction.However,the starting time and the associated deep crust-mantle processes are still debatable.Mafic dike swarms carry important information on the deep earth(including mantle)geodynamics and geochemical evolution.In the Jiangnan Orogen(South China).there is no information on whether the Mesozoic magmatic activities in this region are also directly related to the Pacific subduction or not.In this study,we present detailed zircon U-Pb geochronological,wholerock element and Sr-Nd isotope data for Early Cretaceous Tuanshanbei dolerite dikes,and provide new constraints on the condition of the lithospheric mantle and mantle dynamics of the SCB during that time.LA-ICP-MS zircon U-Pb dating suggests that this dolerite erupted in the Early Cretaceous(~145 Ma).All samples have alkaline geochemical affinities with K_(2)O+Na_(2)O=3.11-4.04 wt%,K_(2)O/Na_(2)O=0.50-0.72,and Mg^(#)=62.24-65.13.They are enriched in LILE but depleted in HFSE with higher initial^(87)Sr/^(86)Sr ratio(0.706896-0.714743)and lower ε_(Nd)(t)(-2.61 to-1.67).They have high Nb/U,Nb/La,La/Sm and Rb/Sr,and low La/Nb,La/Ta,Ce/Pb,Ba/Rb,Tb/Yb and Gd/Yb ratios.Such geochemical signatures suggest that the fractional crystallization is obvious but crustal contamination play a negligible role during magmatic evolution.Tuanshanbei dolerite were most likely derived from low-degree(2%-5%)partial melting of a phlogopite-bearing mantle material consisted of~85% spinel peridotite and~15% garnet peridotite previously metasomatized by asthenospherederived fluids/melts with minor subduction-derived fluids/melts.Slab-rollback generally lead to the upwelling of the hot asthenosphere.The upwelling of asthenosphere consuming the lithospheric mantle by thermo-mechanical-chemical erosion.The lithospheric mantle may have partially melted due to the heating by the upwelling asthenosphere and lithospheric extension.It is inferred that the Tuanshanbei dolerite might be associated with the initial slab rollback and corresponding lithospheric extension occurred potentially at ca.145 Ma.
基金supported by National Science Foundation of China (Grant No. 41425010, 41503023 &41273034)China Geological Survey (Grant No. 12120114022701 & 12120115027101)
文摘Mafic dike swarms are well-developed within the Tethyan Himalaya,southern Tibet,in response to the breakup of Gondwana supercontinent,seafloor spreading of the Tethyan Ocean,and forearc hyperextension during the