关键词: 郯庐断裂带, 幔源包体, 上地幔, 包体结构, 古地温线

Abstract: The mantle xenoliths from 6 localities along and eastward of the active Tanlu fault zone are mostly spinel lherzolite, with few exception of wehrlite. The textures are variable from initial porphyroclastic through granuloblaslic to mylonitic. The analysis of mineral equilibria has revealed that these xenoliths attained to a good state of equilibrium.The equilibrium temperatures determined by using 3 different methods are 700-1000℃, while the pressures have been estimated to be in a range of 0.9-2.5 GPa. The constructed geotherms have shown that most of the points lie above the theorectical continental geotherm, indicating the existence of an upper mantle diapir associated with tectonic extension known to occur in thus region. The low temperature of mylonitic xenoliths indicates the existence of an active shear zone just below the crust. It might control the development of seismically active zone in this region.

Key words: Tanlu fault zone, Upper mantle, Mantle xenolith, Texture of xenolith, Palaeogeotherm