Possible seismic reflector in the lower crust: Evidence from fabrics and experiments of seismic velocity on layered gabbro at high temperature and high pressure  

作　　者：OUXingong JINZhenmin JINShuyan H.Kern 

机构地区：[1]GraduateSchool,ChinaUniversityofGeosciences,Wuhan430074,China [2]FacultyofEarthSciences,ChinaUniversityofGeosciences,Wuhan430074,China [3]InstitutfürGeowissenschaften,UniversitǎtKiel,24098Kiel,Germany

出　　处：《Chinese Science Bulletin》2003年第9期914-920,共7页

基　　金：This work was supported by the National Natural Science Foundation of China(Grant No.49633120)the Foundation of the Opened I aboratory of Constitution,Interaction and Dynamics of Crust-Mantle System,the Ministry of Land and Resources of China.

摘　　要：Lattice preferred orientations (LPO) of plagioclase and augite are measured on layered gabbro from the Panxi region, Sichuan Province. The LPO concentration [010] of plagioclase and [100] of augite are perpendicular to the foliation, which indicates a kind of growth fabric associated with crystallizing habits of minerals when the magma is solidifying under the compaction. Calculated seismic velocities based on LPO data of minerals give rise to rather strong anisotropy 5.81% and 5.54% for compressional seismic wave (Vp) and shear seismic wave (Vs), respectively. The experiments at high temperature and high pressure show that the P-wave velocity of layered gabbro is 6.44-6.97 km/s with the maximum Vp anisotropy 5.22% and the Poisson's ratio is between 0.28-0.31. According to the comparison of fabrics with seismic velocities of layered gabbro, it is uggested that the large-scale layered intrusive body or the similar layered geological body may exist in the lower crust of this area. Such a layered intrusive body which has strong seismic anisotropy may be the seismic reflector in the lower crust.Lattice preferred orientations (LPO) of plagio-clase and augite are measured on layered gabbro from the Panxi region, Sichuan Province. The LPO concentration [010] of plagioclase and [100] of augite are perpendicular to the foliation, which indicates a kind of growth fabric associated with crystallizing habits of minerals when the magma is solidifying under the compaction. Calculated seismic velocities based on LPO data of minerals give rise to rather strong anisotropy 5.81% and 5.54% for compressional seismic wave (Vp) and shear seismic wave (Vs), respectively. The experiments at high temperature and high pressure show that the P-wave velocity of layered gabbro is 6.44-6.97 km/s with the maximum Vp anisotropy 5.22% and the Poisson's ratio is between 0.28-0.31. According to the comparison of fabrics with seismic velocities of layered gabbro, it is suggested that the large-scale layered intrusive body or the similar layered geological body may exist in the lower crust of this area. Such a layered intrusive body which has strong seismic anisotropy may be the seismic reflector in the lower crust.

关 键 词：地震反射体 地震速率 分层辉长石 高温高压实验 下层地壳 格子首选方向 各向异性 地球物理勘探 

分 类 号：P631.4[天文地球—地质矿产勘探]