Constituent minerals of nepheline-olivine basalt in Bolaven plateau, Laos.

Abstract

Nepheline-olivine (Ne-Ol) basalt is distributed at the east area of the Bolaven plateau in Southern Laos. The Ne-Ol basalt is massive and dark blue gray in color. Olivine, Ti-pyroxene, Ti-Fe oxide, spinel, are occurred as microphenocryst in the Ne-Ol basalt. Especially, nepheline occurs as three modes; 1) euhedral microphenocryst, 2) anhedral interstitial mineral, and 3) inclusions in Ti-pyroxene and Ti-Fe oxide. By these observations, an order of crystallization is considered as follows; Ol+Nep+Px+Sp+Opq -> Nep+Px+Opq.