大陆深俯冲带的地壳速度结构——东大别造山带深地震宽角反射/折射研究  

THE CRUSTAL VELOCITY STRUCTURE OF THE CONTINENTAL DEEP SUBDUCTION BELT:STUDY ON THE EASTERN DABIE OROGEN BY SEISMIC WIDE-ANGLE REFLECTION / REFRACTION

作　　者：刘福田[1] 徐佩芬[1] 刘劲松[1] 尹周勋[1] 秦建业[2] 张先康[3] 张成科[3] 赵金仁[3] 

机构地区：[1]中国科学院地质与地球物理研究所,北京100029 [2]多伦多大学物理系 [3]中国地震局郑州地球物理勘探中心,郑州450002

出　　处：《地球物理学报》2003年第3期366-372,共7页Chinese Journal of Geophysics

基　　金：国家基础研究发展规划项目 (G19990 75 5 0 5 );国家自然科学基金重大项目 ( 497940 44) .

摘　　要：在安徽大别山 (东大别 )进行的深地震宽角反射 折射探测获得 6条二维地壳速度结构剖面 .结果显示 ,东大别造山带地壳为一高速穹隆构造 ,在其核部中、下地壳变质岩出露于地表 ,波速高达 5 .0km s;在其翼部 ,上、中地壳发育速度约 6 .1km s的壳内低速层 (体 ) .莫霍面的起伏变化较大 ,中心部位深达 41km左右 ,周边地区则抬升到 32～ 34km .在晓天—磨子潭断裂一线下方莫霍面垂向错断 ,断距约 4km .东大别造山带具有大陆深俯冲 -碰撞造山带地壳结构的典型式样 .莫霍面错断与扬子陆块深俯冲有关 ,错断处表征扬子与华北陆块碰撞缝合的深部位置 .高速穹隆构造可能是两陆块碰撞挤压的产物 ,穹隆翼部上、中地壳发育的低速滑脱带 (面 )可能在碰撞期之后的地壳伸展、超高压变质岩从中地壳抬升出露于地表过程中起到重要作用 .Six two-dimensional crustal structure profiles in the eastern Dabie, Anhui Province, have been obtained by the wide-angle reflection/refraction. The results reveal that the crust of the eastern Dabie orogen presents a high-velocity dome, the velocity in the middle- and lower-crust′s metamorphic rocks exposed on the surface in the core of the dome approaches 5.0 km/s, the low velocity layers (body) with about 6.1 km/s has developed in upper-middle crust in it′s both sides wing, the Moho discontinuity relatively largely varies and ranges from ～ 41km in the core to 32～34 km in both sides, and a 4 km Moho-offset is observed beneath along Xiaotian-Muzitan Fault. We recognize that the eastern Dabie orogen shows a velocity-pattern of typical continent-continent deep subduction/collision style. The Moho offset may be related with the deep subductionof the Yangtze Block, and represents the suture zone between the Yangtze/Sino-Korean Block collision. Therefore, the high-velocity dome may occur by collision/extrusion between the both continental Blocks and the low velocity layers (body) mentioned above may play an important role in the post-collisional crust extension and exhumation of the ultra-high press metamorphic rocks.

关 键 词：大陆深俯冲带 深地震测深 地壳速度结构 东大别造山带 

分 类 号：P315.6[天文地球—地震学]