青藏高原东缘及四川盆地的壳幔导电性结构研究
详细信息 本馆镜像全文    |  推荐本文 | | 获取馆网全文
摘要
自从2008年MS8.0级汶川大地震发生以来,青藏高原东缘便成为地质与地球物理研究的热点区域.该区域的龙门山断裂带标志着青藏高原东缘与四川盆地的边界.汶川地震即发生于龙门山断裂带内的映秀—北川断裂上.该地区现有的研究工作多集中于青藏高原东缘及四川盆地的西部,对四川盆地东部构造情况的研究目前较少.在SinoProbe项目的资助下,完成了一条跨越青藏高原东缘及整个四川盆地的大地电磁测深剖面.该剖面自西北始于青藏高原内部的松潘—甘孜地块,向东南延伸穿过龙门山断裂带、四川盆地内部及四川盆地东部的华蓥山断裂,最终止于重庆东南的川东滑脱褶皱带附近.维性分析表明剖面数据整体二维性较好,通过二维反演得到了最终的电性结构模型.该模型表明,从电性结构上看,沿剖面可分为三个主要的电性结构单元,分别为:浅部高阻、中下地壳低阻的松潘—甘孜地块,浅部低阻、中下地壳相对高阻的四川盆地,以及华蓥山以东整体为高阻特征的扬子克拉通地块.龙门山断裂带在电性结构上表现为倾角较缓、北西倾向的逆冲低阻体,反映了青藏高原东缘相对四川盆地的推覆作用.其在地下向青藏高原内部延伸,深度约为20km左右.在标志逆冲推覆滑脱面的低阻层下存在一电性梯度带,表征着低阻的青藏高原中下地壳与高阻的扬子地壳之间的电性转换.位于四川盆地东边界的华蓥山断裂在电性结构上表现为一倾向为南东向的低阻体插入高阻的扬子克拉通结晶基底,切割深度约为30km左右.这一结构反映出华蓥山向西的推覆作用.在电性结构模型的基础上,进一步讨论了青藏高原东缘的壳内物质流、青藏块体与扬子块体的深部关系以及青藏高原东部的隆升机制等构造问题.
Studies on the geology and tectonics of the eastern margin of the Tibetan Plateau have increased over recent years since the MS8.0 Wenchuan earthquake happened in 2008.The Longmenshan fault zone located in this region marks the boundary between the plateau and the Sichuan Basin.The Wenchuan earthquake happened on the Yingxiu-Beichuan fault in this fault zone.Previous studies in this region are mostly focused on the eastern margin of the Tibetan Plateau and the western Sichuan Basin,while studies on tectonics of the eastern Sichuan Basin are still very limited.Under the auspices of the SinoProbe Project,a long magnetotelluric(MT) profile was acquired across the eastern margin of the Tibetan Plateau and the whole Sichuan Basin.The profile starts within the Songpan-Ganze block of the plateau in the northwest,extends southeastward across the Longmenshan fault zone,Sichuan Basin and the Huayingshan fault in the eastern basin,and ends around the East Sichuan decollement fold belt southeast of Chongqing.Dimensionality analysis has shown a good 2D character along the profile,and subsurface electrical structure was obtained through 2D inversions.Electrical structure along the profile could be divided into three major blocks: The Songpan-Ganze block with conductive mid to lower crust and a relatively resistive shallow region,the Sichuan Basin with conductive shallow sediments and relatively resistive mid to lower crust,and the highly resistive part of the Yangtze craton east of Huayingshan fault.The Longmenshan fault presents as a northwestward dipping conductor with a low dip angle,which reflects the overthrusting between the eastern margin of the plateau and the Sichuan Basin.The fault extends beneath the plateau to the depth around 20 km.Below the conductive layer which marks the detachment surface under the Longmenshan nappe structure is an electrical gradient zone within the range of mid to lower crust,which presents the boundary between the conductive Tibetan crust and the resistive Yangtze crust.The Huayingshan fault in the eastern margin of the Sichuan Basin performs as a southeastward dipping conductor which cuts into the resistive basement of the Yangtze craton to the depth of about 30 km.This structure reflects the westward overthrusting of the Huayingshan Mountains.Based on the electrical model,we further discussed some important tectonic issues in this study area,such as the crustal flow,the relationship between Tibetan and Yangtze blocks,and the uplift mechanism of eastern Tibet.
引文
[1]Rowley D B.Age of initiation of collision between India andAsia:A review of stratigraphic data.Earth and PlanetaryScience Letters,1996,145(1):1-13.
    [2]Yin A,Harrison T M.Geologic Evolution of the Himalayan-Tibetan Orogen.Annual Review of Earth and PlanetarySciences,2000,28:211-280.
    [3]Tapponnier P,Peltzer G,LeDain A Y,et al.Propagatingextrusion tectonics in Asia:New insights from simpleexperiments with plasticine.Geology,1982,10(12):611-616.
    [4]Clark M K,Royden L H.Topographic ooze:Building theeastern margin of Tibet by lower crustal flow.Geology,2000,28(8):703-706.
    [5]Jones A G.Imaging the continental upper mantle usingelectromagnetic methods.Lithos,1999,48(1-4):57-80.
    [6]Bai D H,Unsworth M J,Meju M A,et al.Crustaldeformation of the eastern Tibetan plateau revealed bymagnetotelluric imaging.Nature Geoscience,2010,3(5):358-362.
    [7]赵国泽,陈小斌,王立凤等.青藏高原东边缘地壳“管流”层的电磁探测证据.科学通报,2008,53(3):345-350.Zhao G Z,Chen X B,Wang L F,et al.Evidence of crustal'channel flow'in the eastern margin of Tibetan Plateau fromMT measurements.Chinese Science Bulletin,2008,53(12):1887-1893.
    [8]万战生,赵国泽,汤吉等.青藏高原东边缘冕宁—宜宾剖面电性结构及其构造意义.地球物理学报,2010,53(3):585-594.Wan Z S,Zhao G Z,Tang J,et al.The electrical structureof the crust along Mianning-Yibin profile in the eastern edgeof Tibetan plateau and its tectonic implications.Chinese J.Geophys.(in Chinese),2010,53(3):585-594.
    [9]Wang Q,Qiao X J,Lan Q G,et al.Rupture of deep faults inthe 2008 Wenchuan earthquake and uplift of the LongmenShan.Nature Geoscience,2011,4(9):634-640.
    [10]张培震,徐锡伟,闻学泽等.2008年汶川8.0级地震发震断裂的滑动速率、复发周期和构造成因.地球物理学报,2008,51(4):1066-1073.Zhang P Z,Xu X W,Wen X Z,et al.Slip rates andrecurrence intervals of the Longmen Shan active fault zone,and tectonic implications for the mechanism of the May 12Wenchuan earthquake,2008,Sichuan,China.Chinese J.Geophys.(in Chinese),2008,51(4):1066-1073.
    [11]嵇少丞,王茜,孙圣思等.亚洲大陆逃逸构造与现今中国地震活动.地质学报,2008,82(12):1644-1667.Ji S C,Wang Q,Sun S S,et al.Continental extrusion andseismicity in China.Acta Geologica Sinica(in Chinese),2008,82(12):1644-1667.
    [12]Xu Z Q,Ji S C,Li H B,et al.Uplift of the Longmen Shanrange and the Wenchuan earthquake.Episodes,2008,31(3):291-301.
    [13]Dong S W,Li T D,Gao R,et al.A multidisciplinary Earthscience research program in China.Eos Trans.AGU,2011,92(38):313-314.
    [14]董树文,李廷栋.SinoProbe——中国深部探测实验.地质学报,2009,83(7):895-909.Dong S W,Li T D.SinoProbe:the exploration of the deepinterior beneath the Chinese continent.Acta Geologica Sinica(in Chinese),2009,83(7):895-909.
    [15]金胜,张乐天,魏文博等.中国大陆深探测的大地电磁测深研究.地质学报,2010,84(6):808-817.Jin S,Zhang L T,Wei W B,et al.Magnetotelluric methodfor deep detection of Chinese continent.Acta GeologicaSinica(in Chinese),2010,84(6):808-817.
    [16]Styron R,Taylor M,Okoronkwo K.Database of activestructures from the Indo-Asian collision.Eos Trans.AGU,2010,91(20):181-182.
    [17]Gamble T,Goubau W,Clarke J.Magnetotellurics with aremote magnetic reference.Geophysics,1979,44(1):53-68.
    [18]Egbert G D,Booker J R.Robust estimation of geomagnetictransfer functions.Geophysical Journal of the RoyalAstronomical Society,1986,87(1):173-194.
    [19]Swift C M.A magnetotelluric investigation of an electricalconductivity anomaly in the southwestern United States[Ph.D.thesis].Cambridge:Massachusetts Institute of Technology,1967.
    [20]Bahr K.Geological noise in magnetotelluric data:aclassification of distortion types.Physics of the Earth andPlanetary Interiors,1991,66(1-2):24-38.
    [21]Caldwell T G,Bibby H M,Brown C.The magnetotelluricphase tensor.Geophysical Journal International,2004,158(2):457-469.
    [22]Moorkamp M.Comment on‘The magnetotelluric phasetensor’by T.Grant Caldwell,Hugh M.Bibby and ColinBrown.Geophysical Journal International,2007,171(2):565-566.
    [23]Groom R W,Bailey R C.Decomposition of magnetotelluricimpedance tensors in the presence of Local three-Dimensionalgalvanic distortion.Journal of Geophysical Research,1989,94(B2):1913-1925.
    [24]McNeice G W,Jones A G.Multisite,multifrequency tensordecomposition of magnetotelluric data.Geophysics,2001,66(1):158-173.
    [25]Rodi W,Mackie R L.Nonlinear conjugate gradientsalgorithm for 2-D magnetotelluric inversion.Geophysics,2001,66(1):174-187.
    [26]蔡军涛,陈小斌.大地电磁资料精细处理和二维反演解释技术研究(二)——反演数据极化模式选择.地球物理学报,2010,53(11):2703-2714.Cai J T,Chen X B.Refined techniques for data processingand two-dimensional inversion in magnetotelluric II:Whichdata polarization mode should be used in 2D inversion.Chinese J.Geophys.(in Chinese),2010,53(11):2703-2714.
    [27]Ledo J.2-D versus 3-D magnetotelluric data interpretation.Surveys in Geophysics,2005,26(5):511-543.
    [28]Berdichevsky M N.Marginal Notes On Magnetotellurics.Surveys in Geophysics,1999,20(3-4):341-375.
    [29]Zhang Z,Wang Y,Chen Y,et al.Crustal structure acrossLongmenshan fault belt from passive source seismic profiling.Geophys.Res.Lett.,2009,36(17):L17310.
    [30]Robert A,Pubellier M,de Sigoyer J,et al.Structural andthermal characters of the Longmen Shan(Sichuan,China).Tectonophysics,2010,491(1-4):165-173.
    [31]Wang C,Gao R,Yin A,et al.A mid-crustal strain-transfermodel for continental deformation:A new perspective fromhigh-resolution deep seismic-reflection profiling across NETibet.Earth and Planetary Science Letters,2011,306(3-4):279-288.
    [32]徐锡伟,闻学泽,陈桂华等.巴颜喀拉地块东部龙日坝断裂带的发现及其大地构造意义.中国科学(D辑:地球科学),2008,38(5):529-542.Xu X W,Wen X Z,Chen G H,et al.Discovery of theLongriba faults,eastern part of the Bayankela tectonic blockand its geodynamic implications.Sciences in China(SeriesD:Earth Sciences)(in Chinese),2008,38(5):529-542.
    [33]Burchfiel B C,Chen Z L,Yupinc L,et al.Tectonics of theLongmen Shan and Adjacent Regions,Central China.InternationalGeology Review,1995,37(8):661-735.
    [34]王绪本,朱迎堂,赵锡奎等.青藏高原东缘龙门山逆冲构造深部电性结构特征.地球物理学报,2009,52(2):564-571.Wang X B,Zhu Y T,Zhao X K,et al.Deep conductivitycharacteristics of the Longmen Shan,Eastern Qinghai-TibetPlateau.Chinese J.Geophys.(in Chinese),2009,52(2):564-571.
    [35]王伟涛,贾东,李传友等.四川龙泉山断裂带变形特征及其活动性初步研究.地震地质,2008,30(4):968-979.Wang W T,Jia D,Li C Y,et al.Preliminary investigationon deformation characteristics and activity of Longquanshanfault belt in Sichuan.Seismology and Geology(in Chinese),2008,30(4):968-979.
    [36]万天丰.中国大地构造学.北京:地质出版社,2011:258-262.Wan T F.The Tectonics of China:Data,Maps andEvolution.New York:Springer,2011:300-304.
    [37]刘启元,李昱,陈九辉等.汶川MS8.0地震:地壳上地幔S波速度结构的初步研究.地球物理学报,2009,52(2):309-319.Liu Q Y,Li Y,Chen J H,et al.Wenchuan MS8.0earthquake:preliminary study of the S-wave velocitystructure of the crust and upper mantle.Chinese J.Geophys.(in Chinese),2009,52(2):309-319.
    [38]张季生,高锐,曾令森等.龙门山及邻区重、磁异常特征及与地震关系的研究.地球物理学报,2009,52(2):572-578.Zhang J S,Gao R,Zeng L S,et al.Relationship betweencharacteristics of gravity and magnetic anomalies and theearthquakes in Longmenshan range and adjacent areas.Chinese J.Geophys.(in Chinese),2009,52(2):572-578.
    [39]许志琴,杨经绥,姜枚等.大陆俯冲作用及青藏高原周缘造山带的崛起.地学前缘,1999,6(3):139-151.Xu Z Q,Yang J S,Jiang M,et al.Continental subductionand uplifting of the orogenic belts at the margin of theQinghai-Tibet Plateau.Earth Science Frontiers(in Chinese),1999,6(3):139-151.
    [40]吴建平,黄媛,张天中等.汶川MS8.0级地震余震分布及周边区域P波三维速度结构研究.地球物理学报,2009,52(2):320-328.Wu J P,Huang Y,Zhang T Z,et al.Aftershock distributionof the MS8.0Wenchuan earthquake and three dimensional P-wave velocity structure in and around source region.ChineseJ.Geophys.(in Chinese),2009,52(2):320-328.
    [41]Zhao W J,Kumar P,Mechie J,et al.Tibetan plateoverriding the Asian plate in central and northern Tibet.Nature Geoscience,2011,4(12):870-873.
    [42]Hubbard J,Shaw J H.Uplift of the Longmen Shan andTibetan plateau,and the 2008Wenchuan(M=7.9)earthquake.Nature,2009,458(7235):194-197.

版权所有:© 2023 中国地质图书馆 中国地质调查局地学文献中心