Geochronological and geochemical constraints on the petrogenesis and geodynamic process of Hemler,Vlinder,and Il'ichev seamount lavas in NW Pacific  

作　　者：Xun WEI Yan ZHANG Xuefa SHI Hui ZHANG 

机构地区：[1]Key Laboratory of Marine Geology and Metallogeny,First Institute of Oceanography,Ministry of Natural Resources,Qingdao 266061,China [2]Laboratory for Marine Geology,Qingdao Marine Science and Technology Center,Qingdao 266237,China [3]Shandong Key Laboratory of Deep Sea Mineral Resources Development(Preparatory),Qingdao 266061,China

出　　处：《Science China Earth Sciences》2024年第6期1856-1871,共16页中国科学（地球科学英文版）

基　　金：supported by the Basic Scientific Fund for National Public Research Institutes of China(Grant No.2023S02);the National Natural Science Foundation of China(Grant Nos.42076076&42376075);the Taishan Scholar Program of Shandong Province。

摘　　要：Oceanic intraplate volcanoes with linear age progressions are usually accepted to be derived from melting of an upwelling mantle plume.Several seamount groups in NW Pacific,however,show complex age-distance relationships that are difficult to explain using the classic“mantle plume hypothesis”,and thus their origins are controversial.In this study,we present ^(40)Ar-^(39)Ar age,geochemical,and Sr-Nd-Pb-Hf isotopic data of lavas from Hemler,Vlinder,and Il’ichev seamounts in NW Pacific,to elucidate their petrogenesis and geodynamic process.The lavas from Hemler,Vlinder,and Il’ichev seamounts are classified as alkali basalt,basanite/nephelinite,and trachyte.Lavas with Mg O>8 wt.%exhibit high contents of CaO,FeO^(T),and TiO_(2),similar to the composition of melts formed from reaction between carbonated eclogite-derived melts and fertile peridotite.These lavas have elevated Zr/Hf ratios(40.6-45.2)and negative Zr and Hf anomalies,indicating the presence of a carbonate component in the mantle source.They are enriched in incompatible trace elements and have enriched mantle 1(EM1)-like SrNd-Pb-Hf isotopic compositions.The isotopic compositions of Vlinder,Il’ichev basanite,and Hemler lavas in this study are similar to the Rarotonga hotspot.Although occurring at the same seamount,the Il’ichev alkali basalts display more depleted SrNd-Hf isotopic compositions compared to Il’ichev basanite.According to plate tectonic reconstruction results,the ages of Hemler(100.1 Ma),Vlinder pre-(100.2 Ma)and post-shield(87.5 Ma),and Il’ichev(56.4 Ma)lavas clearly deviate from the Macdonald,Arago,Rarotonga,and Samoa hotspot tracks,indicating that they cannot directly originate from mantle plumes.We propose that in the mid-Cretaceous,when the Pacific plate passed over Rarotonga hotspot,melting of Rarotonga plume formed the Vlinder(main-shield stage),Pako,and Ioah seamounts.The Rarotonga(and possibly Samoa)plume materials would have been dispersed into the surrounding asthenosphere by mantle convection.These diffuse plume materi

关 键 词：Mantle plume Magellan seamount trail Carbonated mantle component Hotspot Lithosphere extension 

分 类 号：P736[天文地球—海洋地质]