Phlogopite Amphibole Pyroxenite Xenoliths in Langao, Shaanxi Province: Evidences for Mantle Metasomatism
岚皋金云角闪辉石岩类捕虏体：地幔交代作用的证据

Phlogopite amphibole pyroxenite xenoliths included in alkali basic ultrabasic subvolcanic complex in Langao, Shaanxi Province are composed of diopside, Ti rich pargasite, phlogopite, apatite, sphene and ilmenite, which have triple points, cataclastic, kink banded textures. Mineral chemistry shows that clinopyr oxene, amphibole, phlogopite are fromed by mantle metasomatism. Compared with original spinel lherzolite from Eastern China, the xenoliths are enriched in TiO 2, Fe 2O 3, CaO, Na 2O, K 2O, with an apparent depletion in MgO. Chondrite normalized REE patterns and primordial mantle normalized trace elements data show that they are enriched in REE (especially LREE) and incompatible trace elements. The petrographic, mineralogical and geochemcial characteristics indicate that the xenoliths are metasomatized mantle xenoliths, which offer the evidences for mantle metasomatism and represent the anomalous mantle of early Palaeozic rift in North Daba Mts. The processes of metasomatism varied from liquid metasomatism in the deep mantle (>90km) to siliceous melt metasomatism.