【作者】 熊绍柏； 滕吉文； 尹周勋； 赖明惠； 黄一平；

【Author】 Xiong Shaobai Teng Jiwen Yin Zhouxun Lai Minghui Huang Yiping (Institute of Geophysics,Chinese Academy of Sciences)

【机构】 中国科学院地球物理研究所；

【摘要】 本文对中国西南地区攀(枝花)-西(昌)构造带的爆炸地震资料进行了初步研究,对横穿构造带长350 km的东西向测线上的六个记录剖面进行了震相对比和解释.结果表明,本区地壳可分为上、中、下三个大的构造层,其厚度分别约为20、20和15 km.地壳厚度约为55 km,平均P波速度为6.22 km/s.位于构造带轴部的渡口地区,近地表有一高速岩体,它可能与攀枝花钒钛磁铁矿的富集有关.中地壳下部,在距地表23—27 km深度之下有一个P波低速带,其厚度为9—14 km,这一结果与天然地震震源分布和居里面的深度非常一致,说明低速带的存在可能与地壳介质的热状态有关.剖面中,有几条可能延伸到上地幔顶部的深断裂带,以及下地壳上部有高速夹层,说明地壳中有地幔物质侵入.本区上地幔顶部P_n波速度为7.62—7.90 km/s,这一结果与大陆裂谷地区的P_n波速度接近.通过与其它地区的对比研究,我们推断所讨论地区有可能是一个被后期构造运动强烈改造过的古裂谷带.更多还原

【Abstract】 Based on the explosion seismology data in the Panzhihua-Xichang tectonic belt region, the structures of the crust and upper mantle are studied in this paper.The results reveal that: (1) The crust can be divided into three big layers,of which the thicknesses are 20,20 and 15 km respectively;(2) The crustal thickness is about 55 km,and the average velocity ofcrust is 6.22 km/ s;(3) There is a low-velocity zone in the middle crust,in which the velocity is 5.6-6.0 km/s and the thickness is 9-14 km.(4) The velocity at the top of upper mantle is 7.62-7.90 km/s,which is consistent with those of recent continental rifting regions;(5) There are several deep faults which probably go down to upper mantle in the region,and some high-velocity bodies in the lower crust. To sum up,we concluded that the axis area very possibly used to be a channal through which the mantle material intruded up,and the Panzhihua-Xichang tectonic belt is perhaps an anciant rift which was strongly transformed by later period’s tectogenesis.更多还原