西秦岭—东昆仑及邻近地区地壳结构——深地震宽角反射/折射剖面结果
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摘要
在青藏高原东北缘,穿过阿尼玛卿缝合带东端完成了一条637km的近南北向深地震宽角反射/折射剖面.获得的地壳结构剖面表明,该地区Moho界面埋深48~51km,北浅南深,横向变化不大,而地壳内部构造在不同的地质构造块体差异明显.在下地壳内出现的两组能量较强的P3、P4波组,反映了研究区下地壳的反射性质和多层结构特征.阿坝弧形断裂以南和阿尼玛卿缝合带附近壳内界面变形强烈,壳内低速异常结构明显,特别是在缝合带下方20km以下的中下地壳异常的低速结构可以解释为存在延伸至中下地壳的破碎带构造特征.在剖面南段反映西秦岭褶皱带至松甘块体相应的地震记录出现复杂、强烈的中下地壳反射和相对较弱的Moho反射震相是该地区地壳结构的明显特征.
A 637 km long wide-angle seismic reflection and refraction profile in the north-south direction was carried out in the northeast margin of Tibet plateau,which crosses A'nyemaqen suture belt. The crust section obtained from the seismic data shows that the depth of the Moho is about 48～51 km. The crust is slightly thicker in the south and it varies smoothly toward the north along the profile with different structures in the various tectonic blocks. The clearly identified overcritical reflections P_3,P_4 on the seismic record sections indicate that the lower crust features multi-layer structure and strong reflectivity in this area. There are severe deformations on the interfaces of the crust,and low velocity distributions on the south of Aba arcuate fault and near A'nyemaqen suture belt. The low velocity zone in the mid and low crust beneath A'nyemaqen suture belt may be explained as the extension of the suture belt into the crust. The crust structure from the West Qinling fold zone to Songpan-Garze block is characterized by strong reflections from the mid and lower crust,and relatively weak Moho reflections on the seismic record sections.
A 637 km long wide-angle seismic reflection and refraction profile in the north-south direction was carried out in the northeast margin of Tibet plateau,which crosses A'nyemaqen suture belt. The crust section obtained from the seismic data shows that the depth of the Moho is about 48～51 km. The crust is slightly thicker in the south and it varies smoothly toward the north along the profile with different structures in the various tectonic blocks. The clearly identified overcritical reflections P_3,P_4 on the seismic record sections indicate that the lower crust features multi-layer structure and strong reflectivity in this area. There are severe deformations on the interfaces of the crust,and low velocity distributions on the south of Aba arcuate fault and near A'nyemaqen suture belt. The low velocity zone in the mid and low crust beneath A'nyemaqen suture belt may be explained as the extension of the suture belt into the crust. The crust structure from the West Qinling fold zone to Songpan-Garze block is characterized by strong reflections from the mid and lower crust,and relatively weak Moho reflections on the seismic record sections.
引文
1)石油部物探局研究院.全国布格重力异常图.1983
[1]万天丰,赵维明.论中国大陆的板内变形机制.地学前缘,2002,9(2):451~463Wan TF,Zhao WM.Onthe mechanismof intraplate deformationin Chinese continent.Earth Science Frontiers(in Chinese),2002,9(2):451~463
[2]马杏垣主编.中国岩石圈动力学地图集.北京:中国地图出版社,1989Ma X Y.Lithospheric Dynamics Atlas of China(in Chinese).Beijing:China Cartographic Publishing House,1989
[3]杨经绥,许志琴,李海兵等.东昆仑阿尼玛卿地区古特提斯火山作用和板块构造体系.岩石矿物学杂志,2005,24(5):369~380Yang J S,Xu Z Q,Li HB,et al.The plate-Tethyan volcanismand plate tectonic regime in the A’nyemaqen region of East Kunlun,northern Tibet Plateau.Acta Petrologica et Mineralogica(in Chinese),2005,24(5):369~380
[4]边千韬,罗小全,陈海泓等.阿尼玛卿蛇绿岩带花岗—英云闪长岩锆石U-Pb同位素定年及大地构造意义.地质科学,1999,34(4):420~426Bian QT,Luo X Q,Chen H H,et al.Zircon U-Pb age of granodiorite-tonalite in the A’nyemaqen ophiolitic belt and its tectonic significance.Scientia Geologica Sinica(in Chinese),1999,34(4):420~426
[5]许志琴,侯立玮,王大可等.“西康式”褶皱以及变形机制——一种新的造山带褶皱类型.中国区域地质,1991,(1):1~9Xu Z Q,Hou L W,Wang D K,et al.“Xikang-type”fold and their deformation mechanism-Anewfold type in orogenic belts.Regional GeologyofChina(in Chinese),1991,(1):1~9
[6]王椿镛,韩渭宾,吴建平等.松潘—甘孜造山带地壳速度结构.地震学报,2003,25(3):229~241Wang C Y,Han WB,Wu J P,et al.Crustal structure beneath the Songpen-Ganze orogenic belt.Acta Seismologica Sinica(in Chinese),2003,25(3):229~241
[7]李松林,张先康,张成科等.玛沁—兰州—靖边地震测深剖面地壳速度结构初步研究.地球物理学报,2002,45(2):210~217Li S L,Zhang X K,Zhang C K,et al.A preliminary study on the crustal velocitystructure of Maqin-Lanzhou-Jingbian by means of deep seismic sounding profile.Chinese J.Geophys.(in Chinese),2002,45(2):210~217
[8]崔作舟,陈纪平,吴苓.阿尔泰—台湾岩石圈地学断面综合研究:见:花石峡—邵阳深部地壳的结构和构造.北京:地质出版社,1996.49~168Cui Z Z,Chen J P,Wu L.Acomprehensive study of the Alatai—Taiwan lithospheric geotransect.In:Deep Crustal Structure and Tectonics fromHuashixiato Shaoyang.Beijing:Geological Publishing House,1996.49~168
[9]王椿镛,林中洋,陈学波.青海门源—福建宁德地学断面综合地球物理研究.地球物理学报,1995,38(5):590~598Wang C Y,Lin Z Y,Chen X B.Comprehensive study of geophysics on geoscience transect from Menyuan,Qinghai Province,to Ningde,Fujian Province,China.Chinese J.Geophys.(in Chinese),1995,38(5):590~598
[10]闵祥仪,周民都,郭建康等.灵台—阿木去乎剖面地壳速度结构.西北地震学报,1991,13(增刊):37~43Min X Y,Zhou MD,Guo J K,et al.The crustal velocitystructure in Lingtai-Amuquhu profile.Northwestern Seismological Journal(in Chinese),1991,13(Suppl.):37~43
[11]高锐,马永生,李秋生等.松潘地块与西秦岭造山带下地壳的性质和关系—深地震反射剖面的揭露.地质通报,2006,25(12):1361~1367Gao R,Ma YS,Li QS,et al.Structure of thelower crust beneaththe Songpan block and West Qinling orogen andtheir relation as revealed by deep seismic reflection profiling.Geological Bulletin ofChina(in Chinese),2006,25(12):1361~1367
[12]张国伟,张本仁,袁学诚等.秦岭造山带与大陆动力学.北京:科学出版社,2001.743~805Zhang G W,Zhang B R,Yuan X C,et al.Qinling Orogen and The Continental Dynamics.Beijing:Science Press,2001.743~805
[13]滕吉文,尹周勋,熊绍柏.西藏高原北部地区色林错—篷错—那曲—索县地带地壳结构与速度分布.地球物理学报,1985,28(增刊Ⅰ):28~42Teng J W,Yin Z X,Xiong S B.Crustal structure and velocity distribution beneath Selin Co-Peng Co-Na Qu-Suo County region in the Northern Xizang plateau.Chinese J.Geophys.(Acta Geophysica Sinica)(in Chinese),1985,28(Suppl.Ⅰ):28~42
[14]张中杰,李英康,王光杰等.藏北地壳东西向结构与“下凹”莫霍面—来自宽角反射剖面的启示.中国科学(D辑),2001,31(11):881~888Zhang ZJ,Li Y K,Wang GJ,et al.E-Wcrustal structure under the northern Tibet and“down-bowing”Moho under the northern Tibet revealed by wide-angle seismic profile.Science in China(Series D)(in Chinese),2001,31(11):881~888
[15]徐朝繁,张先康,张建狮等.射线数分布分析法及其在地壳上部复杂结构探测中的应用.地震学报,2006,28(2):167~175Xu Z F,Zhang X K,ZhangJ S,et al.Ray hit analysis method andits application to complex upper crustal structure survey.Acta Seismological Sinica,2006,28(2):167~175
[16]Cerveny V,Psencik I.SEIS83-numerical modeling of seismic wavefield in2-D laterally varying layered structures by the ray method.In:Engdahl E R ed.Documentation of Earthquake Algorithm.Boulder Colo Rep:World Data Center for Solid Earth Geohpysical,SE-35,1984,36~40
[17]嘉世旭,刘昌铨.动力学射线追踪方法及其在二维非均匀介质理论地震图计算中的应用.见:中国大陆深部构造的研究与进展.北京:地质出版社,1988.279~287Jia S X,Liu C Q.Dynamic ray tracing and its application to the computation of synthetic seismograms in2-D heterogeneous medium.In:Developments in the Research of Deep Structures of China’s Continent.Beijing:Geological Publishing House,1988.279~287
[18]张先康,赵金仁,张成科等.帕米尔东北侧地壳结构研究.地球物理学报,2002,45(5):665~671Zhang X K,Zhao J R,Zhang C K,et al.Crustal structure at the northeast side of the Pamirs.Chinese J.Geophys.(in Chinese),2002,45(5):665~671
[1]万天丰,赵维明.论中国大陆的板内变形机制.地学前缘,2002,9(2):451~463Wan TF,Zhao WM.Onthe mechanismof intraplate deformationin Chinese continent.Earth Science Frontiers(in Chinese),2002,9(2):451~463
[2]马杏垣主编.中国岩石圈动力学地图集.北京:中国地图出版社,1989Ma X Y.Lithospheric Dynamics Atlas of China(in Chinese).Beijing:China Cartographic Publishing House,1989
[3]杨经绥,许志琴,李海兵等.东昆仑阿尼玛卿地区古特提斯火山作用和板块构造体系.岩石矿物学杂志,2005,24(5):369~380Yang J S,Xu Z Q,Li HB,et al.The plate-Tethyan volcanismand plate tectonic regime in the A’nyemaqen region of East Kunlun,northern Tibet Plateau.Acta Petrologica et Mineralogica(in Chinese),2005,24(5):369~380
[4]边千韬,罗小全,陈海泓等.阿尼玛卿蛇绿岩带花岗—英云闪长岩锆石U-Pb同位素定年及大地构造意义.地质科学,1999,34(4):420~426Bian QT,Luo X Q,Chen H H,et al.Zircon U-Pb age of granodiorite-tonalite in the A’nyemaqen ophiolitic belt and its tectonic significance.Scientia Geologica Sinica(in Chinese),1999,34(4):420~426
[5]许志琴,侯立玮,王大可等.“西康式”褶皱以及变形机制——一种新的造山带褶皱类型.中国区域地质,1991,(1):1~9Xu Z Q,Hou L W,Wang D K,et al.“Xikang-type”fold and their deformation mechanism-Anewfold type in orogenic belts.Regional GeologyofChina(in Chinese),1991,(1):1~9
[6]王椿镛,韩渭宾,吴建平等.松潘—甘孜造山带地壳速度结构.地震学报,2003,25(3):229~241Wang C Y,Han WB,Wu J P,et al.Crustal structure beneath the Songpen-Ganze orogenic belt.Acta Seismologica Sinica(in Chinese),2003,25(3):229~241
[7]李松林,张先康,张成科等.玛沁—兰州—靖边地震测深剖面地壳速度结构初步研究.地球物理学报,2002,45(2):210~217Li S L,Zhang X K,Zhang C K,et al.A preliminary study on the crustal velocitystructure of Maqin-Lanzhou-Jingbian by means of deep seismic sounding profile.Chinese J.Geophys.(in Chinese),2002,45(2):210~217
[8]崔作舟,陈纪平,吴苓.阿尔泰—台湾岩石圈地学断面综合研究:见:花石峡—邵阳深部地壳的结构和构造.北京:地质出版社,1996.49~168Cui Z Z,Chen J P,Wu L.Acomprehensive study of the Alatai—Taiwan lithospheric geotransect.In:Deep Crustal Structure and Tectonics fromHuashixiato Shaoyang.Beijing:Geological Publishing House,1996.49~168
[9]王椿镛,林中洋,陈学波.青海门源—福建宁德地学断面综合地球物理研究.地球物理学报,1995,38(5):590~598Wang C Y,Lin Z Y,Chen X B.Comprehensive study of geophysics on geoscience transect from Menyuan,Qinghai Province,to Ningde,Fujian Province,China.Chinese J.Geophys.(in Chinese),1995,38(5):590~598
[10]闵祥仪,周民都,郭建康等.灵台—阿木去乎剖面地壳速度结构.西北地震学报,1991,13(增刊):37~43Min X Y,Zhou MD,Guo J K,et al.The crustal velocitystructure in Lingtai-Amuquhu profile.Northwestern Seismological Journal(in Chinese),1991,13(Suppl.):37~43
[11]高锐,马永生,李秋生等.松潘地块与西秦岭造山带下地壳的性质和关系—深地震反射剖面的揭露.地质通报,2006,25(12):1361~1367Gao R,Ma YS,Li QS,et al.Structure of thelower crust beneaththe Songpan block and West Qinling orogen andtheir relation as revealed by deep seismic reflection profiling.Geological Bulletin ofChina(in Chinese),2006,25(12):1361~1367
[12]张国伟,张本仁,袁学诚等.秦岭造山带与大陆动力学.北京:科学出版社,2001.743~805Zhang G W,Zhang B R,Yuan X C,et al.Qinling Orogen and The Continental Dynamics.Beijing:Science Press,2001.743~805
[13]滕吉文,尹周勋,熊绍柏.西藏高原北部地区色林错—篷错—那曲—索县地带地壳结构与速度分布.地球物理学报,1985,28(增刊Ⅰ):28~42Teng J W,Yin Z X,Xiong S B.Crustal structure and velocity distribution beneath Selin Co-Peng Co-Na Qu-Suo County region in the Northern Xizang plateau.Chinese J.Geophys.(Acta Geophysica Sinica)(in Chinese),1985,28(Suppl.Ⅰ):28~42
[14]张中杰,李英康,王光杰等.藏北地壳东西向结构与“下凹”莫霍面—来自宽角反射剖面的启示.中国科学(D辑),2001,31(11):881~888Zhang ZJ,Li Y K,Wang GJ,et al.E-Wcrustal structure under the northern Tibet and“down-bowing”Moho under the northern Tibet revealed by wide-angle seismic profile.Science in China(Series D)(in Chinese),2001,31(11):881~888
[15]徐朝繁,张先康,张建狮等.射线数分布分析法及其在地壳上部复杂结构探测中的应用.地震学报,2006,28(2):167~175Xu Z F,Zhang X K,ZhangJ S,et al.Ray hit analysis method andits application to complex upper crustal structure survey.Acta Seismological Sinica,2006,28(2):167~175
[16]Cerveny V,Psencik I.SEIS83-numerical modeling of seismic wavefield in2-D laterally varying layered structures by the ray method.In:Engdahl E R ed.Documentation of Earthquake Algorithm.Boulder Colo Rep:World Data Center for Solid Earth Geohpysical,SE-35,1984,36~40
[17]嘉世旭,刘昌铨.动力学射线追踪方法及其在二维非均匀介质理论地震图计算中的应用.见:中国大陆深部构造的研究与进展.北京:地质出版社,1988.279~287Jia S X,Liu C Q.Dynamic ray tracing and its application to the computation of synthetic seismograms in2-D heterogeneous medium.In:Developments in the Research of Deep Structures of China’s Continent.Beijing:Geological Publishing House,1988.279~287
[18]张先康,赵金仁,张成科等.帕米尔东北侧地壳结构研究.地球物理学报,2002,45(5):665~671Zhang X K,Zhao J R,Zhang C K,et al.Crustal structure at the northeast side of the Pamirs.Chinese J.Geophys.(in Chinese),2002,45(5):665~671
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