The granites of ambiguous geodynamic mechanism in the Qin-Fang tectonic belt(SW China)were studied in detail based on petrological,element geochemical,zircon U-Pb geochronological,and Hf isotopic data.LA-ICPMS U-Pb an...The granites of ambiguous geodynamic mechanism in the Qin-Fang tectonic belt(SW China)were studied in detail based on petrological,element geochemical,zircon U-Pb geochronological,and Hf isotopic data.LA-ICPMS U-Pb analyses on zircon yield ages of 248-245 Ma for the granites from the Qin-Fang tectonic belt.The geochemical data show that they are high-K,calc-alkaline,and peraluminous series.Their ε_(Hf)(t)values are from -14.01 to -7.75 with two-stage model ages of 1.74-1.43 Ga.These data,integrated with low Al_(2)O_(3)/TiO_(2),Rb/Sr,Rb/Ba,and(Na_(2)O+K_(2)O)/(FeO^(T)+MgO+TiO_(2))ratios,and high CaO/Na_(2)O ratios for the granite,suggest an origin from psammite source which was contaminated by mantle-derived components.These observations,in combination with the age data and stratigraphic records in the Jinshajiang,Ailaoshan,and Hainan Island areas suggest that the granites were formed in a post-collision tectonic setting.The Qin-Fang tectonic belt was likely a branched ocean basin of the eastern Paleo-Tethys.展开更多
基金financially supported by the National Natural Science Foundation of China(No.42372102)the Guangxi Natural Science Foundation Program(Nos.2017GXNSFAA198209 and 2022GXNSFAA035620)the Guangxi Key R&D Program(No.AB22035045).
文摘The granites of ambiguous geodynamic mechanism in the Qin-Fang tectonic belt(SW China)were studied in detail based on petrological,element geochemical,zircon U-Pb geochronological,and Hf isotopic data.LA-ICPMS U-Pb analyses on zircon yield ages of 248-245 Ma for the granites from the Qin-Fang tectonic belt.The geochemical data show that they are high-K,calc-alkaline,and peraluminous series.Their ε_(Hf)(t)values are from -14.01 to -7.75 with two-stage model ages of 1.74-1.43 Ga.These data,integrated with low Al_(2)O_(3)/TiO_(2),Rb/Sr,Rb/Ba,and(Na_(2)O+K_(2)O)/(FeO^(T)+MgO+TiO_(2))ratios,and high CaO/Na_(2)O ratios for the granite,suggest an origin from psammite source which was contaminated by mantle-derived components.These observations,in combination with the age data and stratigraphic records in the Jinshajiang,Ailaoshan,and Hainan Island areas suggest that the granites were formed in a post-collision tectonic setting.The Qin-Fang tectonic belt was likely a branched ocean basin of the eastern Paleo-Tethys.
