大别山榴辉岩的密度和波速及其对壳—幔循环的启示

测定了大别山地区榴辉岩和麻粒岩的密度和高温高压 (至 5 .0GPa和 130 0℃ )的纵波速度 (Vp)。超高压榴辉岩具有较高的密度和Vp 及较弱的各向异性。榴辉岩的压力系数为 0 .2 2～ 0 .33km/s·GPa ,超高压榴辉岩的温度系数为 - 3.41× 10 -4 km/s·℃。榴辉岩的密度和波速的分析表明 ,地幔深部的超高压榴辉岩形成后可能包含了两个过程 ,即一部分榴辉岩通过拆沉作用进入深部地幔 ,另一部分快速折返至地壳内或地表 ,榴辉岩的形成过程代表了壳幔物质循环。现今的大别山深部可能只存在少量榴辉岩。

Density and Pwave Velocity of the Eclogite from Dabieshan and Its Implications for Crust-Mantle Recycling

P-wave velocities in the rocks of Dabieshan, Central China weremeasured at pressures up to 5.0 GPa and temperatures up to 1300℃. The ultrahigh pressure eclogites have the highest density and P-wave velocity (Vp) and lower anisotropy. Pressure derivatives of the eclogites range from 0.22 to 0.33 km／s．GPa. Average temperature derivatives of the eclogites are -3.41×10－4 km/s．℃. The density and VP of the eclogites imply that, there will be two united possibilities related to crust-mantle recycling after the eclogite formed in the deep lithosphere. One is that some eclogite in the deep lithosphere was detached and sank into deeper mantle caused by their denser density. Another is that some eclogite return to the crust and exposed in the surface.