The velocities of a series of deep-seated xenoliths in Late Mesozoic-Cenozoic basaltic rocks from Tuoyun basin, western Xinjiang (NW China), are calculated. These data, combined with the published seismic velocities for the area, are used to define the composition and structure of the crust-mantle transitional zone beneath southwestern Tianshan. The calculated velocities of peridotite and granulite xenoliths are 6.98-7.36 km/s and 7.96-8.47 km/s, respectively. The comparison of these data with the seismic velocities shows the presence of the crust-mantle transitional zone in 40-48 km beneath southwestern Tianshan. The zone consists of quartz granulite, pyroxene granulite and olivine/garnet granulite from top to bottom, and then transfers into the upper mantle mainly composed of spinel-facies lherzolite with or without volatile component minerals (phlogopite or amphibole). Such crust-mantle structure of lithosphere can be well explained by magma underplating and metamorphism.
|Number of pages||7|
|Journal||Diqiu Kexue - Zhongguo Dizhi Daxue Xuebao/Earth Science - Journal of China University of Geosciences|
|Publication status||Published - May 2008|
- Crust-mantle transitional zone
- Magma underplating
- Southwestern Tianshan