Basalts from the Late Carboniferous to Early Permian are extensively developed in the central Lhasa subterrane,southern Xizang.Studying the petrogenesis of these rocks may have implications for the late Paleozoic arc ...Basalts from the Late Carboniferous to Early Permian are extensively developed in the central Lhasa subterrane,southern Xizang.Studying the petrogenesis of these rocks may have implications for the late Paleozoic arc magmatism along the central Lhasa subterrane uncovering more of the evolution of the Sumdo Paleo-Tethys Ocean and its dynamic mechanism.Basalt samples from the Luobadui Formation in the Leqingla area,NW of Linzhou City in the central Lhasa subterrane,southern Xizang exhibit arc-like geochemical signatures in a subduction-zone tectonic setting characterized by high Al_(2)O_(3)and low TiO_(2)contents,fractionated REE patterns with low Nb/La ratios and high LREE concentrations,and negative HFSE anomalies.Based on their higher Th/Ce,Nb/Zr,and lower Ba/Th,Pb/Nd ratios,slightly negative to positiveε_(Nd)(t)values,and the relatively high Sr-Pb isotopic compositions,these samples were probably derived from partial melting of a depleted mantle source of garnet+spinel lherzolite,metasomatized by subducted sediments around 297 Ma.Modeling of the trace elements indicates that these basalts experienced fractional crystallization of olivine,clinopyroxene and minor plagioclase during magma ascent and eruption.It is proposed that these Late Carboniferous–Early Permian basalts are associated with the northward subduction of the Sumdo Paleo-Tethys Ocean seafloor along the southern margin of the central Lhasa subterrane.展开更多
Feldspar Pb isotopes have been widely used to trace magmatic formation and evolution processes.However,it remains unclear whether post-magmatic thermal events can affect feldspar Pb isotopic ratios.Here,the in situ Pb...Feldspar Pb isotopes have been widely used to trace magmatic formation and evolution processes.However,it remains unclear whether post-magmatic thermal events can affect feldspar Pb isotopic ratios.Here,the in situ Pb isotopic composition of feldspar hosted in granitic rocks(thirteen Archean and one Paleoproterozoic)from the northern Kongling terrane,Yangtze Craton,South China,is analyzed.The samples reveal a substantial variation in their Pb isotopic composition,spanning the gap between the 1.9 Ga and present-day geochrons,which indicates extensive resetting by later tectonothermal events.This resetting was interpreted to have likely resulted from Paleoproterozoic and Neoproterozoic tectonothermal events related to the assembly and breakup of the Columbia and Rodinia supercontinents.These results suggest that Pb isotopes should be used cautiously when tracing magma sources and petrogenesis in magmatic rocks that have experienced post-magmatic reworking.However,the in situ Pb isotopic composition of feldspar in ancient granitoids may also potentially be used to reveal later tectonothermal events.The extensive resetting of the Pb isotopic composition in feldspar by regional thermal events may also provide new insights into our understanding of the Pb isotope paradox.展开更多
基金the National Key Research and Development Program of China(Grant No.2022YFF0800903)the National Natural Science Foundation of China(Grant Nos.42302107,92162322,42261144669,41922022,42003036)+4 种基金the China Geological Survey(Grant Nos.DD20243512,DD20230008)the National Postdoctoral Research Program of China(Grant No.GZC20232489)the Second Tibetan Plateau Scientific Expedition and Research(Grant No.2021QZKK0304)Xing Dian Youth Talent Plan of Yunnan Province(Grant No.XDYC-QNRC-2022-0136)the UNESCO:IUGS IGCP-662 Program。
文摘Basalts from the Late Carboniferous to Early Permian are extensively developed in the central Lhasa subterrane,southern Xizang.Studying the petrogenesis of these rocks may have implications for the late Paleozoic arc magmatism along the central Lhasa subterrane uncovering more of the evolution of the Sumdo Paleo-Tethys Ocean and its dynamic mechanism.Basalt samples from the Luobadui Formation in the Leqingla area,NW of Linzhou City in the central Lhasa subterrane,southern Xizang exhibit arc-like geochemical signatures in a subduction-zone tectonic setting characterized by high Al_(2)O_(3)and low TiO_(2)contents,fractionated REE patterns with low Nb/La ratios and high LREE concentrations,and negative HFSE anomalies.Based on their higher Th/Ce,Nb/Zr,and lower Ba/Th,Pb/Nd ratios,slightly negative to positiveε_(Nd)(t)values,and the relatively high Sr-Pb isotopic compositions,these samples were probably derived from partial melting of a depleted mantle source of garnet+spinel lherzolite,metasomatized by subducted sediments around 297 Ma.Modeling of the trace elements indicates that these basalts experienced fractional crystallization of olivine,clinopyroxene and minor plagioclase during magma ascent and eruption.It is proposed that these Late Carboniferous–Early Permian basalts are associated with the northward subduction of the Sumdo Paleo-Tethys Ocean seafloor along the southern margin of the central Lhasa subterrane.
基金supported by the Key Laboratory of Gold Mineralization Processes and Resource Utilization,MNRShandong Provincial Key Laboratory of Metallogenic Geological Process and Resource Utilization(Grant No.KFKT202103)National Natural Science Foundation of China(Grant No.41876037)。
文摘Feldspar Pb isotopes have been widely used to trace magmatic formation and evolution processes.However,it remains unclear whether post-magmatic thermal events can affect feldspar Pb isotopic ratios.Here,the in situ Pb isotopic composition of feldspar hosted in granitic rocks(thirteen Archean and one Paleoproterozoic)from the northern Kongling terrane,Yangtze Craton,South China,is analyzed.The samples reveal a substantial variation in their Pb isotopic composition,spanning the gap between the 1.9 Ga and present-day geochrons,which indicates extensive resetting by later tectonothermal events.This resetting was interpreted to have likely resulted from Paleoproterozoic and Neoproterozoic tectonothermal events related to the assembly and breakup of the Columbia and Rodinia supercontinents.These results suggest that Pb isotopes should be used cautiously when tracing magma sources and petrogenesis in magmatic rocks that have experienced post-magmatic reworking.However,the in situ Pb isotopic composition of feldspar in ancient granitoids may also potentially be used to reveal later tectonothermal events.The extensive resetting of the Pb isotopic composition in feldspar by regional thermal events may also provide new insights into our understanding of the Pb isotope paradox.
