Pliocene–Holocene Alkali-Basaltoid Volcanism of the Tsushima Basin of the Sea of Japan: New Geochemical and Geodynamic Data

Abstract

Abstract—The paper contains original data on the rock-forming and rare element compositions in the Pliocene–Holocene alkaline basaltoids of the Tsushima Basin Sea of Japan, obtained by the “wet chemistry” method, atomic emission spectrometry, and inductively coupled plasma mass spectrometry. Based on interpretation of these data, the geochemical and geodynamic features of this stage of volcanism were established; the source of magmogenesis was revealed, represented by garnet peridotites. The withinplate plume–continental nature of the alkaline basaltoids was established, indicated by the high alkalinity and potassium content of rocks, Ta–Nb maximum, high normalized La/Yb (22–28) and La/Sm (3–6) values, as well as high Ti/V, Nb/Y, Zr/Y, Zr/Hf, Th/Yb, and Nb/Ta indices close to chondrite. The withinplate nature is also to some degree confirmed by the closeness of the chemical features of Tsushima basaltoids to rocks of Zinbochu and Udalyanche volcanoes of the Central Asian withinplate province (CAWP) located to west from the Sea of Japan, and it was formed in the Late Cenozoic under the influence of the North Asian superplume.