Portal de Periódicos da CAPES

Primitive tholeiitic basalt from the Yabakei district, Oita prefecture, southwest Japan.

1990; Japan Association of Mineralogical Sciences; Volume: 85; Issue: 12 Linguagem: Inglês

10.2465/ganko.85.559

1881-3275

Susumu Kakubuchi, Yukio Matsumoto,

Geochemistry and Elemental Analysis

High magnesian tholeiitic basalts of late Miocene to Pliocene age are found in the Yabakei district, northern part of Oita Prefecture, southwest Japan. These basalts (Yabakei basalts) are ± orthopyroxene clinopyroxene olivine basalt and are characterized by high MgO (11.4-9.1 wt %), Cr (859-528 ppm), Ni (206-156 ppm) contents and low FeO*/MgO ratio (0.69-0.78). The most primitive basalt has olivine phenocrysts with narrow range of Fo composition (Fo90-85) and high NiO content (0.35 wt %). Yabakei basalts are plotted into P-type MORB field of 2 Nb-Zr/4-Y diagram. The primordial mantle normalized spidergram for Yabakei basalts have simi-lar configurations to alkali basalts from northen Kyushu, with significant trough at K and peaks at Ba. This suggests that the sources mantle of Yabakei basalts have geochemical characteristics similar to those of northern Kyushu basalts.