Peridotite xenoliths occurring in late Neocene intraplate alkaline basalt from Baegryeong west-northern part of the Korean peninsula, are mainly anhydrous spinel lherzolites. The xenoliths display coarse grained protogranular through inequigranular to cumulate textures, grading into each other. They often show wTell-developed annealed textures and the triple junctions, suggesting that they went through static( dynamic) recrystallization. "f hey also contain left leftover olivine grains within orthopyroxene, indicating replacement of olivine by orthopyroxene. The constituent minerals are compositionally homogeneous and appear to he equilibrated. The xenoliths are characterized by the high Mg#]=100 xMg/(Mg+Fetotd) atomic ratio] of olivine, orthopyroxene and clinopyroxene (89-93) and the CO [=100xCr/(Cr+A1)] atomic ratio] of spine] (9-15). The calculated equilibrium temperatures and oxygen fu,gacities resulted in 920-L070 C. and 2if02(Qt-M)=-1.5-0.5, respectively. Clinopyroxenes of the xenoliths are mostly enriched in incompatible trace elements, exhibiting three types of REF patterns: (J) LREE-depleted [(La/Yh)N=0.3-0.4, (La/Ce)5=0.9-1.01, 2 LREE-enriched [(La/Yb)N=1.8-2.7, (La/Ce)N=1.6-1.7], and 2 a enrichment in La over Ce [(La/Yb)N=0.2-0.5, (La/Ce)N=1.0-1.1]. They also show depletion in high field strength elements(e.g., Nh-Ta, Zr-Hf, Ti) and low field strength elements (e.g., RI) and Baj. We thus propose the Baegryeong peridotite xenoliths represent residues left after early melt extraction, which was subsequently subjected to different degrees of modal/cryptic metasomatism by silica- and LREE-enriched fluids (or melts).
