Mafic rocks generated from subduction settings have recorded valuable source information about the mantle source.In this study,we present a comprehensive analysis of zircon U–Pb dating,whole-rock major and trace elem...Mafic rocks generated from subduction settings have recorded valuable source information about the mantle source.In this study,we present a comprehensive analysis of zircon U–Pb dating,whole-rock major and trace elements,and Sr–Nd isotopic data for the mafic gabbro located in the Yumen area,on the western part of the Yangtze Block,South China,aiming to constrain the processes of mantle metaso-matism within subduction settings.U–Pb dating results for zircon yield crystallization ages of 800 Ma for type 1 mafic gabbro and 753–734 Ma for type 2 mafic gabbro.Type 1 mafic gabbro exhibits higher SiO_(2)(44.13%–48.93%)and Al_(2)O_(3)content but lower total Fe2O3 and MgO content than type 2 gabbro(SiO_(2):41.02%–43.28%).These gabbros dis-play a high-Mg^(#)signature(52.50–62.81 for type 1,50.89–57.04 for type 2),while they are enriched in significant large-ion lithophile elements(LILEs:Rb,Ba,Sr,K)and depleted in high-field-strength elements(HFSEs:Zr,Hf,Nd,Ta,Ti),which indicates an arc-like element signature.The positive whole-rockεNd(t)values(type 1:3.5–4.4,type 2:5.6–6.3)combined with a narrow range of(^(87)Sr/^(86)Sr)_(i)(type 1:0.7035–0.7043,type 2:0.7035–0.7036)of both gabbro types suggest a depleted lithospheric mantle origin.There-fore,these mafic rocks may derive from a metasomatized spinel lherzolite mantle source(with amphibole)due to the interactions of the deep mantle source and subductionfluid materials.We propose that the long-term metasomatism recorded by mafic gabbro in this study supports the fact that the subduction during the Neoproterozoic contributed to the formation of a metasomatized mantle source in the Yumen area,western Yangtze Block,South China.展开更多
基金The National Natural Science Foundation of China[Grant Nos.42172056,42202048]co-supported this work.
文摘Mafic rocks generated from subduction settings have recorded valuable source information about the mantle source.In this study,we present a comprehensive analysis of zircon U–Pb dating,whole-rock major and trace elements,and Sr–Nd isotopic data for the mafic gabbro located in the Yumen area,on the western part of the Yangtze Block,South China,aiming to constrain the processes of mantle metaso-matism within subduction settings.U–Pb dating results for zircon yield crystallization ages of 800 Ma for type 1 mafic gabbro and 753–734 Ma for type 2 mafic gabbro.Type 1 mafic gabbro exhibits higher SiO_(2)(44.13%–48.93%)and Al_(2)O_(3)content but lower total Fe2O3 and MgO content than type 2 gabbro(SiO_(2):41.02%–43.28%).These gabbros dis-play a high-Mg^(#)signature(52.50–62.81 for type 1,50.89–57.04 for type 2),while they are enriched in significant large-ion lithophile elements(LILEs:Rb,Ba,Sr,K)and depleted in high-field-strength elements(HFSEs:Zr,Hf,Nd,Ta,Ti),which indicates an arc-like element signature.The positive whole-rockεNd(t)values(type 1:3.5–4.4,type 2:5.6–6.3)combined with a narrow range of(^(87)Sr/^(86)Sr)_(i)(type 1:0.7035–0.7043,type 2:0.7035–0.7036)of both gabbro types suggest a depleted lithospheric mantle origin.There-fore,these mafic rocks may derive from a metasomatized spinel lherzolite mantle source(with amphibole)due to the interactions of the deep mantle source and subductionfluid materials.We propose that the long-term metasomatism recorded by mafic gabbro in this study supports the fact that the subduction during the Neoproterozoic contributed to the formation of a metasomatized mantle source in the Yumen area,western Yangtze Block,South China.
