关键词: 拉蒙特海山, 玄武岩, 地幔柱, 西太平洋

Abstract: In this study, we report new major and trace element, Sr-Nd-Pb-Hf isotopic compositions for ten basaltic lavas from the poorly studied Lamont seamount in the western Pacific Ocean. The results show that the rock types of the Lamont Seamount are basalt, trachybasalt, alkali basalt and picrite basalt, which belong to silica-undersaturated alkaline rocks. The lavas are generally enriched in LILE and HFSE, depleted in HREE, Zr, Hf and Ti, and show a positive Nb-Ta anomaly. Around 80 Ma, the Lamont Seamount formed the initial shape that mainly was influenced by the Arago hotspot, and then underwent vertical uplift and subsidence movements to change into the current morphology. The magmatic material of the seamount mainly originated from the DM and FOZO mantle, and was also influenced by the HIMU and EMI mantle end-member components. The mantle lithology of the source area is mainly pyroxenite. The basaltic magma mainly originated from the melts of secondary plume emanating from the Pacific Large Low Shear Velocity Province (LLSVP), and multiple batches of magma were stored in the upper mantle magma chamber, and experienced significant crystallization processes of Fe-Ti oxides, amphibole, olivine and plagioclase. Different volcanic rocks underwent different degrees of magmatic fractional crystallization. 

Key words: Lamont Seamount, basalt, mantle plume, Western Pacific Ocean