14:15 〜 14:30
[MGI33-02] 微量元素組成から考察する海洋プレート内アルカリ玄武岩の再分類
キーワード：海洋島玄武岩、プチスポット、主成分分析
Oceanic hotspot and petit-spot basalts are generally categorized as oceanic island basalts (OIBs) in their geochemical characteristics of enriched incompatible element compositions. The basalts derived from hotspot volcanoes show systematic evolution in magmatic compositions for several volcanic stages. The petit-spot basalts showing similar composition to OIB, on the other hand, must have different processes in their petrogenesis from hotspot magmas. Here, we adopt the principal component analysis (PCA) for selected trace elements in order to explain their geochemical features along the eruptive settings and magmatic evolution. The compositional variations of OIBs from selected intraplate volcanism in the Pacific Ocean and their structure of high-dimensional geochemical data are recognized using PCA for 26 incompatible elements in this study. The first principal component simply demonstrates their concentrations of all incompatible elements. The second principal component expresses depletions of HREE and fertilizations of LREE designating residual garnet in source mantle. The third principal component enhances HFSE anomaly, particularly in negative Nb, Ta, Zr, Hf and Ti, and positive Ba, Pb and Sr anomalies. This component evidently discriminates between the petit-spot basalts together with some rejuvenated stage lavas and other OIBs. The data suggest the similar mechanism in the petrogenesis of both petit-spots and lavas on the rejuvenated stage.