关键词: 轻变质—沉积岩, 岩石波速—压力, 大陆碰撞, 块体拼贴, 造山作用, 裂谷作用

Abstract: Xuefengshan belt is located in the central part of South China. China’s Sinoprobe Project obtained a 400-kmlong high-resolution seismic-reflection profile across the central South China including Xuefeng-Jiangnan thrust belt. Interpretation of seismic data suggests that there is a hidden orogenic belt under Xuefengshan belt, which is Paleoproterozoic (2.05-1.75ga) and modified by Neoproterozoic rifting. This rifting may be related to the breakup of Rodinia supercontinent, and thus is of great significance for understanding the tectonic evolution history of South China and reconstructing the evolution of supercontinents Rodinia and Columbia. In this paper, the wave velocity characteristics of the low-grade metamorphic sedimentary rocks of the Neoproterozoic Banxi Group and Lengjiaxi Group in the Xuefengshan area are studied using the ultrasonic pulse transmission method. The results show that the wave velocity increases rapidly and nonlinearly with pressure, after the critical pressure, velocity increases slowly and linearly with the pressure. For rocks with lineation and foliation, the fastest wave propagation direction is parallel to the foliation and lineation, and the slowest wave propagation direction is vertical to the foliation and lineation. The anisotropy of rock seismic wave is 2%~12%. The theoretical calculation results are in good agreement with the actual measurement data. Therefore, the experimental measurements of velocity provide velocity data for the seismic data interpretation in Xuefengshan belt. 

Key words: low-grade metamorphic-sedimentary rocks, rock velocity-pressure, continental collision, assembly of blocks;
orogenesis, rifting