Petrological investigations on the granulite xenoliths from Hannuoba basalts, northern Sino-Korean Craton

Abstract

According to their mineral assemblages, the granulite xenoliths entrained by Cenozoic Hannuoba basalts are divided into four groups: felsic granulites, noritic granulites, two-pyroxene two-feldspar granulites and two-pyroxene granulites, with the two-pyroxene granulites most common. The xenoliths are all in recrystallized structure and homogeneous or layered texture. The modes of the xenoliths and the composition of the major phases are different from group to group, but some potential compositional connection exists between clinopyroxene, orthopyroxene and plagioclase. As the major component of the lower crust, the two-pyroxene granulites are concentrated in the P-T range of 800°~950°C and 0.6~1.1 GPa, with the two-pyroxene two-feldspar granulites in the similar P-T range. The extinction of the two-pyroxene-bearing granulites within the temperature ranger higher than 950°C indicates the position of petrological crustmantle boundary beneath Hannuoba area.