大别造山带与郯庐断裂带壳、幔结构和陆内“俯冲”的耦合效应

地质学家基于岩石年代学、峰期变质的压力差和阿尔卑斯变质沉积岩中柯石英的发现，推断在大别造山带地区发现的柯石英和榴辉岩乃是地幔深处120km左右折返至地壳浅部的结果.为了提供大别造山带与郯庐断裂带地域的壳、幔深部结构与深层动力过程的定量判据，本文利用瑞利（Rayleigh）波的频散效应反演该区S波的三维群速度结构分布.研究结果表明：（1）该区存在一由东向西陆内俯冲的高速板舌，其下插深度仅达160 km.在秦岭—大别造山带地域上地幔70km深处存在一顶部宽约500km的低速地幔热点.（2）出露的含柯石英榴辉岩是大别造山带深部物质和能量的交换，郯庐断裂带强烈平移错动及板内俯冲效应共同作用导致的深部物质(上地幔)运移和动力学效应的综合产物.

Structure of Earth's crust and upper mantle, inland subduction and its coupling effects on the Dabie orogenic belt and the Tancheng-Lujiang fault zone

Based on the rock chronology, the metamorphic pressure difference in the peak period and the discovered coesite in Alpine metase sedimentary rock, the coesite and eclogite from the Dabie orogenic belt is inferred to be the consequence resulted from their reentry from mantle around the depth of 120km to the shallow crust. To introduce the quantitative evidence of the deep structure and dynamic process in the Dabie orogenic belt, the 3_D group velocity structure of S wave in the studied area is investigated by the dispersion effects of Rayleigh wave. The results show that a high velocity subduction slab of tongue shape with underthrusting depth 160km extending from east to west. A low velocity mantle hotspot with a 500km wide head is found at depth of 70km in the upper mantle beneath the Qinling_Dabie orogenic belt. The outcrop of coesite and eclogites in the Dabie orogenic belt is the synthetical consequence of the movement and dynamic effects of deep (upper mantle) material resulted from the deep substance and energy exchange, strong strike-slip motion of the TanLu fault belt and the inland subduction.