The Baibokoum syenitic pluton(BSP),located in southern Chad,to the NE of the Adamawa-Yadédomain,is one of the few strongly potassic magmatic bodies in the southern part of the Central African Fold Belt(CAFB)in Ch...The Baibokoum syenitic pluton(BSP),located in southern Chad,to the NE of the Adamawa-Yadédomain,is one of the few strongly potassic magmatic bodies in the southern part of the Central African Fold Belt(CAFB)in Chad.It has been previously studied petrologically,but its petrogenesis has remained poorly known.Petrographic and whole-rock geochemical data presented in this article highlight their magma genesis and geodynamic evolution.The BSP consists of medium-to coarse-grained syenites associated with minor microdiorites,which occur as syn-plutonic dikes and mafic microgranular enclaves(MME)coarse-and medium-grained syenites outcrop respectively to the core and the border of the BSP.The syenite displays high-K and alkaline to trans-alkaline affinity.Petrographic and geochemical data suggest that medium-to coarse-grained syenites are from single magma source that evolved and differentiated by fractional crystallization in a magma reservoir.REE profiles show enriched LREEs(La_(N)/Yb_(N)=6.19-45.55)while HREEs show an almost flat profile(Dy_(N)/Yb_(N)=1.0-2.23),and the La/Sm and Sm/Yb ratios have led to propose that the aforementioned rocks derived from the partial melting of a garnet-spinel-lherzolite mantle source.Negative Nb and Ta anomalies indicate that this mantle source was modified by the addition of subduction-related material.Th/Yb ratios associated with high Ba/La ratios indicate that enrichment of the source could be related to slab-derived fluids.The parental magma of the BSP was generated by partial melting of the metasomatized lithospheric mantle that was modified into arc-magmatism material in a subduction setting.Its emplacement took place in two successive stages:a static stage of fractional crystallization and crystal settling in a deep magma source and a dynamic stage in a shear deformation setting during which stratified magma rises towards the upper crust,with evolved syenite magma being emplaced first and diorite later.The emplacement of the BSP was probably controlled by the evolution of the Tcholliré-Banyo Fault and M'BéréShear Zone during the Pan-African orogeny.展开更多
The Suzhou granitic pluton is the first identified Nb-Ta-rich granite in China.To reveal the genetic link between the sequence of magmatic and hydrothermal evolution and Nb-Ta mineralization in different intrusive pha...The Suzhou granitic pluton is the first identified Nb-Ta-rich granite in China.To reveal the genetic link between the sequence of magmatic and hydrothermal evolution and Nb-Ta mineralization in different intrusive phases of the Suzhou granite,whole-rock geochemistry,geochemistry and U-Th-Pb dating of monazite was analyzed.The unique geochemical characteristics show that the Suzhou pluton can be discriminated as an A-type granite.LA-ICP-MS U-Th-Pb dating of monazite in both the medium-and coarse-grained biotite granite(MBG)and the fine-grained biotite granite(FBG)indicates that the granite formed between 124 and 127 Ma.Based on geochemical characteristics and mineral textures,the MBG(Mnz-Ia)and FBG(Mnz-Ib)monazites are classified as magmatic monazites;another monazite(Mnz-II)from the MBG formed during a magmatic-hydrothermal transitional stage.Nb-Ta in the Suzhou pluton gradually concentrated during fractional crystallization and alteration of Ti-rich minerals and biotite.Ultimately,with the involvement of F-Li-rich fluid,Nb-Ta mineralization occurred during the magmatic-hydrothermal transition.The Suzhou pluton is considered part of a 600-km-and NE-SW-trending Nb-rich A-type granite belt together with other Early Cretaceous A-type granites in the Jiangnan Orogen that offers prospects of a new target for Nb-Ta prospecting.展开更多
The western margin of the Yangtze Block hosts diverse Neoproterozoic igneous rocks,with exposed S-type granites serving as key indicators for deciphering regional geological evolution.This study focuses on the Jiudaow...The western margin of the Yangtze Block hosts diverse Neoproterozoic igneous rocks,with exposed S-type granites serving as key indicators for deciphering regional geological evolution.This study focuses on the Jiudaowan granite pluton,located on the western margin of the Yangtze Block,through systematic petrographic,whole-rock geochemical,zircon and monazite U-Pb geochronology,and whole-rock Nd isotopic analyses aiming to elucidate its petrogenesis and tectonic significance.The Jiudaowan granite pluton is a composite body,consisting of the Luotaijiu,Jiudaowan,and Daheishan units,characterized by biotite monzogranites,muscovite-plagioclase granites,and two-mica monzogranites,respectively.LA-ICP-MS zircon and monazite U-Pb dating reveals crystallization ages between 832 and 798 Ma.The three units are peraluminous,containing minerals such as muscovite,garnet,and tourma-line,and exhibiting high SiO_(2)(72.99-77.83 wt%),Al_(2)O_(3)(12.36-15.02 wt%),and A/CNK values(1.06-1.43),con-firming their classification as peraluminous S-type granites.Compositional variations within the Jiudaowan granite pluton are primarily controlled by protolith composition and melting mechanisms.The pluton is distinguished by low CaO/Na_(2)O ratios(0.02-0.18),high Rb/Sr(0.83-113)and Rb/Ba(0.33-15.2)ratios,and negativeεNd(t)values(−13.6 to−9.1),indicating derivation from partial melting of het-erogeneous metasedimentary sources.MgO,TiO_(2),Rb/Sr,and whole-rock Zr saturation temperatures suggest that the Luotaijiu and Daheishan units formed via biotite dehydration melting,whereas the Jiudaowan unit resulted from muscovite dehydration melting.Additionally,the Jiudaowan granite pluton displays a clear negative correlation between Al_(2)O_(3),CaO,Fe_(2)O_(3)T,MgO,TiO_(2),and SiO_(2),along with pronounced Eu negative anomalies and depletions in Sr and Ti,suggesting fractional crystallization of feldspar,mica,and Fe-Ti oxides during magma emplacement.Similarly,variable incompatible element ratios of Nb/U(1.07-18.97)and Nb/La(0.24-26.88)further indicate minor crustal assimilation and contamination during magma evolution.Integrating regional geological data,we propose that the Jiudaowan pluton formed during crustal thickening associated with post-collisional extension,likely related to the breakup of the Rodinia supercontinent.展开更多
Composite granitic pluton with distinct units is a potential target for identifying its detailed magma evolution.Here,we present zircon U-Pb ages and Hf isotope,whole-rock major and trace element compositions and Nd-P...Composite granitic pluton with distinct units is a potential target for identifying its detailed magma evolution.Here,we present zircon U-Pb ages and Hf isotope,whole-rock major and trace element compositions and Nd-Pb isotopes of the Wangxiang composite pluton,South China.New ages obtained show that these rocks were generated in Late Jurassic(ca.156–158 Ma).The rocks are divided into low silica(SiO_(2)<67 wt.%,biotite granodiorites and their dioritic enclaves)and high silica ones(SiO_(2)>71 wt.%,two-mica granites,garnet-bearing muscovite granites and muscovite granites).The high silica rocks are enriched in light rare earth elements(LREEs)relative to heavy REEs(HREEs)((La/Yb)_(N)=15.6–41.9,while the low silica rocks are not(0.7–76.6).All rocks show various negative Ti,Sr,Eu and strong positive Pb anomalies.The low silica rocks have less negative values ofε_(Nd)(t)(-8.79 to-6.99),similar values of~((206)Pb/^(204)Pb)_(i)(18.155–18.346)andε_(Hf)(t)(-9.51 to-3.47,except one-12.84),compared to the high silica rocks(ε_(Nd)(t)=-11.14 to-10.26;^((206)Pb/^(204)Pb)_(i)=17.935–19.093;ε_(Hf)(t)=-12.03 to-7.15,except one-2.41).Data suggest that the parental magma of the studied rocks(represented by enclaves)was produced by partial melting of a garnet-free crustal source.Subsequently those crustal magmas formed the more evolved units through assimilation and fractional crystallization processes,and fluid enrichment during the final magmatic activity.Combining our results with previous multidisciplinary studies,we propose that the key factor to control the evolution of Wangxiang composite pluton is discrete emplacement of crustal magmas by dyking.展开更多
The meta-basic volcanic rocks in the Tengtiaohe Zone yield zircon U–Pb ages of 258.8±2.5 Ma and 259.2±1.8 Ma, respectively which agree with the ages of flood basalts of ELIP and are similar to the basaltic ...The meta-basic volcanic rocks in the Tengtiaohe Zone yield zircon U–Pb ages of 258.8±2.5 Ma and 259.2±1.8 Ma, respectively which agree with the ages of flood basalts of ELIP and are similar to the basaltic rocks and komatiites from the Song Da Zone in northern Vietnam. The results suggest that the age of meta-basic volcanic rocks is Late Permian, rather than the Early Permian or Early Carboniferous ages as previously inferred. Most meta-basic volcanic rocks are strongly enriched in LREEs relative to HREEs and display trace element patterns similar to the ELIP high-Ti basalts, and are enriched in LILEs with negative Sr anomalies. Their initial 87^Sr/86^Sr ratios range from 0.705974 to 0.706188 and εNd（t） from-0.82 to-2.11. Their magmas were derived from an enriched and deep mantle source without significant crustal contamination. These meta-basic volcanic rocks formed in ELIP. Therefore, the Tengtiaohe Zone is not an ophiolite zone and can link to the Song Da Zone in northern Vietnam.展开更多
Early Paleozoic magmatism in the West Kunlun Orogenic Belt(WKOB)preserves important information about the tectonic evolution of the Proto-Tethys Ocean.This paper reports whole-rock compositions,zircon and apatite U-Pb...Early Paleozoic magmatism in the West Kunlun Orogenic Belt(WKOB)preserves important information about the tectonic evolution of the Proto-Tethys Ocean.This paper reports whole-rock compositions,zircon and apatite U-Pb dating,and zircon Hf isotopes for the Qiaerlong Pluton(QEL)at the northwestern margin of WKOB,with the aim of elucidating the petrogenesis of the pluton and shedding insights into the subduction-collision process of this oceanic slab.The QEL is mainly composed of Ordovician quartz monzodiorite(479±3 Ma),quartz monzonite(467–472 Ma),and syenogranite(463±4 Ma),and is intruded by Middle Silurian peraluminous granite(429±20 Ma)and diabase(421±4 Ma).Zirconε_(Hf)(t)values reveal that quartz monzodiorites(+2.1 to+9.9)and quartz monzonites(+0.6 to+6.8)were derived from a mixed source of juvenile crust and older lower crust,and syenogranites(−5.6 to+4.5)and peraluminous granites(−2.9 to+2.0)were generated from a mixed source of lower crust and upper crust;diabases had zirconε_(Hf)(t)values ranging from−0.3 to+4.1,and contained 463±5 Ma captured zircon and 1048±39 Ma inherited zircon,indicating they originated from enriched lithospheric mantle and were contaminated by crustal materials.The Ordovician granitoids are enriched in LILEs and light rare-earth elements,and depleted in HFSEs with negative Nb,Ta,P,and Ti anomalies,suggesting that they formed in a subduction environment.Middle Silurian peraluminous granites have the characteristics of leucogranites with high SiO_(2)contents(74.92 wt.%–75.88 wt.%)and distinctly negative Eu anomalies(δEu=0.03–0.14),indicating that they belong to highly fractionated granite and were formed in a post-collision extension setting.Comparative analysis of these results with other Early Paleozoic magmas reveals that the Proto-Tethys ocean closed before the Middle Silurian and its southward subduction resulted in the formation of QEL.展开更多
文摘The Baibokoum syenitic pluton(BSP),located in southern Chad,to the NE of the Adamawa-Yadédomain,is one of the few strongly potassic magmatic bodies in the southern part of the Central African Fold Belt(CAFB)in Chad.It has been previously studied petrologically,but its petrogenesis has remained poorly known.Petrographic and whole-rock geochemical data presented in this article highlight their magma genesis and geodynamic evolution.The BSP consists of medium-to coarse-grained syenites associated with minor microdiorites,which occur as syn-plutonic dikes and mafic microgranular enclaves(MME)coarse-and medium-grained syenites outcrop respectively to the core and the border of the BSP.The syenite displays high-K and alkaline to trans-alkaline affinity.Petrographic and geochemical data suggest that medium-to coarse-grained syenites are from single magma source that evolved and differentiated by fractional crystallization in a magma reservoir.REE profiles show enriched LREEs(La_(N)/Yb_(N)=6.19-45.55)while HREEs show an almost flat profile(Dy_(N)/Yb_(N)=1.0-2.23),and the La/Sm and Sm/Yb ratios have led to propose that the aforementioned rocks derived from the partial melting of a garnet-spinel-lherzolite mantle source.Negative Nb and Ta anomalies indicate that this mantle source was modified by the addition of subduction-related material.Th/Yb ratios associated with high Ba/La ratios indicate that enrichment of the source could be related to slab-derived fluids.The parental magma of the BSP was generated by partial melting of the metasomatized lithospheric mantle that was modified into arc-magmatism material in a subduction setting.Its emplacement took place in two successive stages:a static stage of fractional crystallization and crystal settling in a deep magma source and a dynamic stage in a shear deformation setting during which stratified magma rises towards the upper crust,with evolved syenite magma being emplaced first and diorite later.The emplacement of the BSP was probably controlled by the evolution of the Tcholliré-Banyo Fault and M'BéréShear Zone during the Pan-African orogeny.
基金supported by the National Natural Science Foundation of China(Grant Nos.41903025 and 41803048)the National Nonprofit Institute Research Grant of IGGE(Grant Nos.AS2024J03,JY202106 and AS2022P03)+2 种基金the Hebei Key Science and Technology Program(Grant No.19057411Z)the National Science and Technology Major Project(Grant No.2024ZD1002402)the China Geological Survey Project(Grant No.DD20221807).
文摘The Suzhou granitic pluton is the first identified Nb-Ta-rich granite in China.To reveal the genetic link between the sequence of magmatic and hydrothermal evolution and Nb-Ta mineralization in different intrusive phases of the Suzhou granite,whole-rock geochemistry,geochemistry and U-Th-Pb dating of monazite was analyzed.The unique geochemical characteristics show that the Suzhou pluton can be discriminated as an A-type granite.LA-ICP-MS U-Th-Pb dating of monazite in both the medium-and coarse-grained biotite granite(MBG)and the fine-grained biotite granite(FBG)indicates that the granite formed between 124 and 127 Ma.Based on geochemical characteristics and mineral textures,the MBG(Mnz-Ia)and FBG(Mnz-Ib)monazites are classified as magmatic monazites;another monazite(Mnz-II)from the MBG formed during a magmatic-hydrothermal transitional stage.Nb-Ta in the Suzhou pluton gradually concentrated during fractional crystallization and alteration of Ti-rich minerals and biotite.Ultimately,with the involvement of F-Li-rich fluid,Nb-Ta mineralization occurred during the magmatic-hydrothermal transition.The Suzhou pluton is considered part of a 600-km-and NE-SW-trending Nb-rich A-type granite belt together with other Early Cretaceous A-type granites in the Jiangnan Orogen that offers prospects of a new target for Nb-Ta prospecting.
基金supported by the Deep Earth Probe and Mineral Resources Exploration-National Science and Technology Major Project(Grant No.2024ZD1001600)National Natural Science Foundation of China(Grants Nos.42302223,42162012 and 42402069)Yunnan Fundamental Research Projects(Grants No.202401CF070093).
文摘The western margin of the Yangtze Block hosts diverse Neoproterozoic igneous rocks,with exposed S-type granites serving as key indicators for deciphering regional geological evolution.This study focuses on the Jiudaowan granite pluton,located on the western margin of the Yangtze Block,through systematic petrographic,whole-rock geochemical,zircon and monazite U-Pb geochronology,and whole-rock Nd isotopic analyses aiming to elucidate its petrogenesis and tectonic significance.The Jiudaowan granite pluton is a composite body,consisting of the Luotaijiu,Jiudaowan,and Daheishan units,characterized by biotite monzogranites,muscovite-plagioclase granites,and two-mica monzogranites,respectively.LA-ICP-MS zircon and monazite U-Pb dating reveals crystallization ages between 832 and 798 Ma.The three units are peraluminous,containing minerals such as muscovite,garnet,and tourma-line,and exhibiting high SiO_(2)(72.99-77.83 wt%),Al_(2)O_(3)(12.36-15.02 wt%),and A/CNK values(1.06-1.43),con-firming their classification as peraluminous S-type granites.Compositional variations within the Jiudaowan granite pluton are primarily controlled by protolith composition and melting mechanisms.The pluton is distinguished by low CaO/Na_(2)O ratios(0.02-0.18),high Rb/Sr(0.83-113)and Rb/Ba(0.33-15.2)ratios,and negativeεNd(t)values(−13.6 to−9.1),indicating derivation from partial melting of het-erogeneous metasedimentary sources.MgO,TiO_(2),Rb/Sr,and whole-rock Zr saturation temperatures suggest that the Luotaijiu and Daheishan units formed via biotite dehydration melting,whereas the Jiudaowan unit resulted from muscovite dehydration melting.Additionally,the Jiudaowan granite pluton displays a clear negative correlation between Al_(2)O_(3),CaO,Fe_(2)O_(3)T,MgO,TiO_(2),and SiO_(2),along with pronounced Eu negative anomalies and depletions in Sr and Ti,suggesting fractional crystallization of feldspar,mica,and Fe-Ti oxides during magma emplacement.Similarly,variable incompatible element ratios of Nb/U(1.07-18.97)and Nb/La(0.24-26.88)further indicate minor crustal assimilation and contamination during magma evolution.Integrating regional geological data,we propose that the Jiudaowan pluton formed during crustal thickening associated with post-collisional extension,likely related to the breakup of the Rodinia supercontinent.
基金provided by the National Natural Science Foundation of China(No.41002022)the National Key R&D Program of China(No.2017YFC0602402)+3 种基金the Provincial Natural Science Foundation of Hunan(No.2019JJ50831)the Opening Foundation of State Key Laboratory of Continental Dynamics,Northwest University(No.20LCD08)the Funded by Open Research Fund Programme of the Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring(Central South University),Ministry of Education(No.2018YSJS07)Bruna B.Carvalho is thankful to MIUR(Ministero dell’Istruzione,dell’Universitàe della Ricerca)for the award of a grant(No.PNRA18_00103)。
文摘Composite granitic pluton with distinct units is a potential target for identifying its detailed magma evolution.Here,we present zircon U-Pb ages and Hf isotope,whole-rock major and trace element compositions and Nd-Pb isotopes of the Wangxiang composite pluton,South China.New ages obtained show that these rocks were generated in Late Jurassic(ca.156–158 Ma).The rocks are divided into low silica(SiO_(2)<67 wt.%,biotite granodiorites and their dioritic enclaves)and high silica ones(SiO_(2)>71 wt.%,two-mica granites,garnet-bearing muscovite granites and muscovite granites).The high silica rocks are enriched in light rare earth elements(LREEs)relative to heavy REEs(HREEs)((La/Yb)_(N)=15.6–41.9,while the low silica rocks are not(0.7–76.6).All rocks show various negative Ti,Sr,Eu and strong positive Pb anomalies.The low silica rocks have less negative values ofε_(Nd)(t)(-8.79 to-6.99),similar values of~((206)Pb/^(204)Pb)_(i)(18.155–18.346)andε_(Hf)(t)(-9.51 to-3.47,except one-12.84),compared to the high silica rocks(ε_(Nd)(t)=-11.14 to-10.26;^((206)Pb/^(204)Pb)_(i)=17.935–19.093;ε_(Hf)(t)=-12.03 to-7.15,except one-2.41).Data suggest that the parental magma of the studied rocks(represented by enclaves)was produced by partial melting of a garnet-free crustal source.Subsequently those crustal magmas formed the more evolved units through assimilation and fractional crystallization processes,and fluid enrichment during the final magmatic activity.Combining our results with previous multidisciplinary studies,we propose that the key factor to control the evolution of Wangxiang composite pluton is discrete emplacement of crustal magmas by dyking.
基金supported by National Natural Science Foundation of China(Grant No.41172202,No.41190073 and No.41302178)China Geological Survey(Grant No.1212011121256)+2 种基金National Basic Research Program of China(2014CB440901)the Fundamental Research Funds for the Central Universities to SYSUState Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences in Wuhan(MSFGPMR201402)
文摘The meta-basic volcanic rocks in the Tengtiaohe Zone yield zircon U–Pb ages of 258.8±2.5 Ma and 259.2±1.8 Ma, respectively which agree with the ages of flood basalts of ELIP and are similar to the basaltic rocks and komatiites from the Song Da Zone in northern Vietnam. The results suggest that the age of meta-basic volcanic rocks is Late Permian, rather than the Early Permian or Early Carboniferous ages as previously inferred. Most meta-basic volcanic rocks are strongly enriched in LREEs relative to HREEs and display trace element patterns similar to the ELIP high-Ti basalts, and are enriched in LILEs with negative Sr anomalies. Their initial 87^Sr/86^Sr ratios range from 0.705974 to 0.706188 and εNd（t） from-0.82 to-2.11. Their magmas were derived from an enriched and deep mantle source without significant crustal contamination. These meta-basic volcanic rocks formed in ELIP. Therefore, the Tengtiaohe Zone is not an ophiolite zone and can link to the Song Da Zone in northern Vietnam.
基金financially supported by the Natural Science Foundation of China(NSFC Nos.U1603245,41703051,U1812402)the Chinese Academy of Sciences“Light of West China”Programthe Natural Science Foundation of Guizhou Province(No.[2018]1171).
文摘Early Paleozoic magmatism in the West Kunlun Orogenic Belt(WKOB)preserves important information about the tectonic evolution of the Proto-Tethys Ocean.This paper reports whole-rock compositions,zircon and apatite U-Pb dating,and zircon Hf isotopes for the Qiaerlong Pluton(QEL)at the northwestern margin of WKOB,with the aim of elucidating the petrogenesis of the pluton and shedding insights into the subduction-collision process of this oceanic slab.The QEL is mainly composed of Ordovician quartz monzodiorite(479±3 Ma),quartz monzonite(467–472 Ma),and syenogranite(463±4 Ma),and is intruded by Middle Silurian peraluminous granite(429±20 Ma)and diabase(421±4 Ma).Zirconε_(Hf)(t)values reveal that quartz monzodiorites(+2.1 to+9.9)and quartz monzonites(+0.6 to+6.8)were derived from a mixed source of juvenile crust and older lower crust,and syenogranites(−5.6 to+4.5)and peraluminous granites(−2.9 to+2.0)were generated from a mixed source of lower crust and upper crust;diabases had zirconε_(Hf)(t)values ranging from−0.3 to+4.1,and contained 463±5 Ma captured zircon and 1048±39 Ma inherited zircon,indicating they originated from enriched lithospheric mantle and were contaminated by crustal materials.The Ordovician granitoids are enriched in LILEs and light rare-earth elements,and depleted in HFSEs with negative Nb,Ta,P,and Ti anomalies,suggesting that they formed in a subduction environment.Middle Silurian peraluminous granites have the characteristics of leucogranites with high SiO_(2)contents(74.92 wt.%–75.88 wt.%)and distinctly negative Eu anomalies(δEu=0.03–0.14),indicating that they belong to highly fractionated granite and were formed in a post-collision extension setting.Comparative analysis of these results with other Early Paleozoic magmas reveals that the Proto-Tethys ocean closed before the Middle Silurian and its southward subduction resulted in the formation of QEL.
