Discovery of mantle and lower crust xenoliths from early Cretaceous volcanic rocks of southwestern Tianshan, Xinjiang

In Tuoyun area of southwestern Tianshan, mantle and lower crust xenoliths a re present in the volcanic rocks with ages of 101-123 Ma. Mantle xenoliths include mineral megacrysts such as kaersutite and pargasite, feldspar, biot ite, and rare pyroxene and rock fragments such as perodotite, pyroxenite, a mphibolite, and rare glimmerite. Lower crust xenoliths are mainly banded an d massive granulite. The volcanic rocks were produced by within-plate magma tism. Occurrence of hydrous and volatile mineral megacrysts, amphibolite, a nd some pyroxenite containing hydrous and volatile minerals indicates that mantle metasomatism was intense. Undoubtedly, this discovery is very import ant to understanding of the crust-mantle structure and geodynamic backgroun d in depth in southwestern Tianshan and geological correlation with adjacen t regions.