青藏高原东西向差异形变与隆升机制
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摘要
高精度布格重力异常约束下的三维空间域挠曲形变模拟显示,大约以90°E为界,青藏高原东、西两部分的岩石圈强度存在明显的差异.在90°E以东,岩石圈有效弹性厚度为35~45km,该岩层厚度可使刚性的上地壳与上地幔岩石通过中下地壳柔塑性地层的黏滞流动产生构造解耦;地壳处于区域均衡状态,下地壳热物质的流动膨胀是地壳隆升的主控要素.而在90°E以西,断裂带严重削弱了该区域的岩石圈机械强度,岩石圈有效弹性厚度小于15km,向西逐渐减小,至喀喇昆仑断裂带变为零,断裂切穿莫霍面进入地幔,发生纯剪切构造形变;这里的地壳接近局部均衡,厚皮逆冲是地形隆升的主要因素.震源深度大于80km的地幔地震大多发生在青藏高原西部,其岩石圈深部具有的脆裂特征很好地支持了岩石圈机械强度模拟的结果.
Distinct mechanical strength over the eastern and western Tibetan plateau derived from flexural modeling suggests a possible different uplift mechanisms between these two portions of the plateau roughly bounced by 90°E.To the east of this longitude,the mechanical strength of the lithosphere measured by effective elastic thickness(Te)is 35 to 45km which permits the decoupling between the strong upper crust and the strong upper mantle lithosphere by week,viscous and flowing middle and lower crust in the middle.In the crustal regional equilibrium in the eastern plateau,the flow and expansion of hot material in lower crust are the main controlling factors of crustal uplift.However,to the west of the 90°E,the strength of the lithosphere gradually decreases toward west till Te values are close to zero along the Karakorum fault.The nearly strength-less lithosphere to the west implies that the entire lithosphere is significantly faulted from surface to the mantle.The occurrence of the mantle earthquakes with focal depths larger than 80 km in the mantle lithosphere are almost all populated to the western and eastern syntaxes of the Tibetan plateau,particularly in the western end of the Himalayas.In the crustalpartial equilibrium,the thick leather thrusting is the main controlling factor of topographic uplift.This evidence of deep brittle failure in the western lithosphere well supports the results from the mechanical modeling.
Distinct mechanical strength over the eastern and western Tibetan plateau derived from flexural modeling suggests a possible different uplift mechanisms between these two portions of the plateau roughly bounced by 90°E.To the east of this longitude,the mechanical strength of the lithosphere measured by effective elastic thickness(Te)is 35 to 45km which permits the decoupling between the strong upper crust and the strong upper mantle lithosphere by week,viscous and flowing middle and lower crust in the middle.In the crustal regional equilibrium in the eastern plateau,the flow and expansion of hot material in lower crust are the main controlling factors of crustal uplift.However,to the west of the 90°E,the strength of the lithosphere gradually decreases toward west till Te values are close to zero along the Karakorum fault.The nearly strength-less lithosphere to the west implies that the entire lithosphere is significantly faulted from surface to the mantle.The occurrence of the mantle earthquakes with focal depths larger than 80 km in the mantle lithosphere are almost all populated to the western and eastern syntaxes of the Tibetan plateau,particularly in the western end of the Himalayas.In the crustalpartial equilibrium,the thick leather thrusting is the main controlling factor of topographic uplift.This evidence of deep brittle failure in the western lithosphere well supports the results from the mechanical modeling.
引文
Audet P,Mareschal J C.2004.Variations in elastic thickness in theCanadian Shield.Earth and Planet.Sci.Lett.,226(1-2):17-31.
Balakrishnan T S.1997.Major tectonic elements of the Indiansubcontinent and contiguous areas:a geophysical view.Geological Society of India,38:18.
Balakrishnan T S.2003.Impact of gravity and other geophysicaldata on the geology of Indian subcontinent.Journal of theVirtual Explorer,12:83-92.
Bechtel T D,Forsyth D W,Sharpton V L,et al.1990.Variationsin effective elastic thickness of the North American lithosphere.Nature,343(6259):636-638.
Braitenberg C,Wang Y,Fang J,et al.2003.Spatial variations offlexure parameters over the Tibet-Quinghai plateau.EarthPlanet.Sci.Lett.,205(3-4):211-224.
Clark M K,Royden L H.2000.Topographic ooze:Building theeastern margin of Tibet by lower crustal flow.Geology,28(8):703-706.
Dewey J F,Burke K C.1973.Tibetan,Variscan,and Precambrianbasement reactivation:Products of continental collision.TheJournal of Geology,81(6):683-692.
England P,Houseman G.1989.Extension during continentalconvergence,with application to the Tibetan Plateau.J.Geophys.Res.:Solid Earth(1978—2012),94(B12):17561-17579.
Forsyth D W.1985.Subsurface loading and estimates of the flexuralrigidity of continental lithosphere.J.Geophys.Res.:SolidEarth(1978—2012),90(B14):12623-12632.
Gao R Q,Zhao Z Z.2001.The Frontier Petroleum Exploration inChina-Petroleum Geology of Qinghai-Tibetan Plateau(inChinese).Beijing:Petroleum Industry Press,28-30.
Jiang M,GalvéA,Hirn A,et al.2006.Crustal thickening andvariations in architecture from the Qaidam basin to the QangTang(North-Central Tibetan Plateau)from wide-anglereflection seismology.Tectonophysics,412(3-4):121-140.
Jiang X D,Jin Y,McNutt M K.2004.Lithospheric deformationbeneath the Altyn Tagh and West Kunlun faults from recentgravity surveys.J.Geophys.Res.:Solid Earth(1978—2012),109(B5):B05406,doi:10.1029/2003JB002444.
Jiang X D,Jin Y.2005.Mapping the deep lithospheric structurebeneath the eastern margin of the Tibetan Plateau from gravityanomalies.J.Geophys.Res.:Solid Earth(1978—2012),110(B7):B07407,doi:10.1029/2004JB003394.
Jin Y,Jiang X D.2002.Lithosphere Dynamics(in Chinese).Beijing:Sciences Press,113-119.
Jin Y,McNutt M K,Zhu Y S.1994.Evidence from gravity andtopography data for folding of Tibet.Nature,371:669-674.
Jin Y,Wang E,Jiang X D.2008.The dynamic support anddecoupling process of the Tibetan lithosphere based on theintegration of flexural modeling with other geological andgeophysical studies.//Burchfiel B C,Wang E.Investigationsinto the Tectonics of the Tibetan Plateau,GSA Special Paper,444:89-104.
Jordan T A,Watts A B.2005.Gravity anomalies,flexure and theelastic thickness structure of the India-Eurasia collisionalsystem.Earth and Planetary Science Letters,236(3-4):732-750,doi:10.1016/j.epsl.2005.05.036.
Kind R,Yuan X,Saul J,et al.2002.Seismic images of crust andupper mantle beneath Tibet:Evidence for Eurasian platesubduction.Science,298(5596):1219-1221.
Kirby J F,Swain C J.2008.An accuracy assessment of the fanwavelet coherence method for elastic thickness estimation.Geochemistry,Geophysics,Geosystems,9(3):Q03022,doi:10.1029/2007GC001773.
Kogan M G,McNutt M K.1993.Gravity field over northernEurasia and variations in the strength of the upper mantle.Science,259(5094):473-479.
Li Q S,Peng S P,Gao R,et al.2003.Seismic evidence of thebasement uplift in the Bayan Har tectonic belt,Qinghai,andits tectonic significance.Geological Bulletin of China(inChinese),22(10):782-788.
Li S L,Zhang X K,Zhang C K,et al.2002.A preliminary study onthe crustal velocity structure of Maqin-Lanzhou-Jingbian bymeans of deep seismic sounding profile.Chinese J.Geophys.(in Chinese),45(2):210-217.
Liu M J,Li S L,Fang S M,et al.2008.Study on crustalcomposition and geodynamics using seismic velocities in thenortheastern margin of the Tibetan Plateau.Chinese J.Geophys.(in Chinese),51(2):412-430.
McNutt M K.1983.Influence of plate subduction on isostaticcompensation in northern California.Tectonics,2(4):399-415.
Meng Q R,Fang X.2008.Cenozoic tectonic development of theQaidam basin in the northeastern Tibetan Plateau.GSA SpecialPaper,444:1-24.
Ojeda G Y,Whitman D.2002.Effect of windowing on lithosphereelastic thickness estimates obtained via the coherence method:results from northern South America.J.Geophys.Res.:SolidEarth(1978—2012),107(B11):ETG 3-1-ETG 3-12,doi:10.1029/200JB000114.
Parker R L.1973.The rapid calculation of potential anomalies.Geophys,J.R.Astr.Soc.,31(4):447-455.
Pérez-GussinyéM,Lowry A R,Phipps Morgan J,et al.2008.Effective Elastic thickness variations along the Andean marginand their relationship to subduction geometry.Geochemistry,Geophysics,Geosystems,9(2):Q02003,doi:10.1029/2007GC001786.
Pérez-GussinyéM,Lowry A R,Watts A B,et al.2004.On therecovery of effective elastic thickness using spectral methods:examples from synthetic data and from the FennoscandianShield.J.Geophys.Res.:Solid Earth(1978—2012),109(B10),doi:10.1029/2003JB002788.
Pérez-GussinyéM,Lowry A R,Watts A B.2007.Effective elasticthickness of South America and its implications for intracontinentaldeformation.Geochemistry,Geophysics,Geosystems,8(5):Q05009,doi:10.1029/2006GC001511.
Royden L H,Burchfiel B C,King R W,et al.1997.Surfacedeformation and lower crustal flow in Eastern Tibet.Science,276(5313):788-790.
Royden L H,Burchfiel B C,van der Hilst R D.2008.Thegeological evolution of the Tibetan Plateau.Science,321(5892):1054-1058.
Simons F J,van der Hilst R D,Zuber M T.2000.Spatiospectrallocalization of isostatic coherence anisotropy in Australia and itsrelation to seismic anisotropy:Implications for lithosphericdeformation.J.Geophys.Res.:Solid Earth(1978—2012),108(B5):19163-19184.
Stewart J,Watts A B.1997.Gravity anomalies and spatialvariations of flexural rigidity at mountain ranges.J.Geophys.Res.:Solid Earth(1978—2012),102(B3):5327-5352.
Swain C J,Kirby J F.2006.An effective elastic thickness map ofAustralia from wavelet transforms of gravity and topographyusing Forsyth′s method.Geophys.Res.Lett.,33(2),doi:10.1029/2005GL025090.
Tapponnier P,Xu Z Q,Roger F,et al.2001.Oblique stepwise riseand growth of the Tibet Plateau.Science,294(5547):1671-1677.
Teng J W,Zhang Z J,Zhang X K,et al.2013.Investigation of theMoho discontinuity beneath the Chinese mainland using deepseismic sounding profiles.Tectonophysics,608:202-216,doi:10.1016/j.tecto.2012.11.024.
Thomson D J.1982.Spectrum estimation and harmonic analysis.Proceedings of the IEEE,70(9):1055-1096.
Torne M,Fernàndez M,Comas M C,et al.2000.Lithosphericstructure beneath the Alboran Basin:results from 3Dgravitymodeling and tectonic relevance.J.Geophys.Res.:SolidEarth(1978—2012),105(B2):3209-3228.
Van Wees J D,Cloetingh S.1994.A finite-difference technique toincorporate spatial variations in rigidity and planar faults into 3-D models for lithospheric flexure.Geophys.J.Int.,117(1):179-195.
Wang Q S,An Y L.2001.Gravity field and deep structure ofMadoi-Shama region in eastern Qinghai-Xizang(Tibetan)plateau.Progress in Geophysics(in Chinese),16(4):4-10.
Wang Y X,Mooney W D,Yuan X C,et al.2013.Crustal Structureof the Northeastern Tibetan Plateau from the Southern TarimBasin to the Sichuan Basin,China.Tectonophysics,584:191-208.
Zhang Z J,Bai Z M,Klemperer S L,et al.2013.Crustal structureacross northeastern Tibet from wide-angle seismic profiling:Constraints on the Caledonian Qilian orogeny and its reactivation.Tectonophysics,606:140-159,doi:10.1016/j.tecto.2013.02.040.
Zhang Z J,Deng Y F,Teng J W,et al.2011a.An overview of thecrustal structure of the Tibetan plateau after 35years of deepseismic soundings.Journal of Asian Earth Sciences,40(4):977-989.
Zhang Z J,Klemperer S,Bai Z M,et al.2011b.Crustal structureof the Paleozoic Kunlun orogeny from an active-source seismicprofile between Moba and Guide in East Tibet,China.Gondwana Research,19(4):994-1007.
Zhang Z J,Yuan X H,Chen Y,et al.2010.Seismic signature ofthe collision between the east Tibetan escape flow and theSichuan Basin.Earth and Planetary Science Letters,292(3-4):254-264.
Zhao W L,Morgan W J.1987.Injection of Indian crust into Tibetanlower crust:a two-dimensional finite element model study.Tectonics,6(4):489-504.
高瑞祺,赵政璋.2001.中国油气新区勘探-第六卷-青藏高原石油地质.北京:石油工业出版社,28-30.
金煜,姜效典.2002.岩石圈动力学.北京:科学出版社,113-119.
李秋生,彭苏萍,高锐等.2003.青藏高原北部巴颜喀拉构造带基底隆起的地震学证据.地质通报,22(10):782-788.
李松林,张先康,张成科等.2002.玛沁—兰州—靖边地震测深剖面地壳速度结构的初步研究.地球物理学报,45(2):210-217.
刘明军,李松林,方盛明等.2008.利用地震波速研究青藏高原东北缘地壳组成及其动力学.地球物理学报,51(2):412-430.
王谦身,安玉林.2001.青藏高原东部玛多—沙马地区的重力场与深部构造.地球物理学进展,16(4):4-10.
Balakrishnan T S.1997.Major tectonic elements of the Indiansubcontinent and contiguous areas:a geophysical view.Geological Society of India,38:18.
Balakrishnan T S.2003.Impact of gravity and other geophysicaldata on the geology of Indian subcontinent.Journal of theVirtual Explorer,12:83-92.
Bechtel T D,Forsyth D W,Sharpton V L,et al.1990.Variationsin effective elastic thickness of the North American lithosphere.Nature,343(6259):636-638.
Braitenberg C,Wang Y,Fang J,et al.2003.Spatial variations offlexure parameters over the Tibet-Quinghai plateau.EarthPlanet.Sci.Lett.,205(3-4):211-224.
Clark M K,Royden L H.2000.Topographic ooze:Building theeastern margin of Tibet by lower crustal flow.Geology,28(8):703-706.
Dewey J F,Burke K C.1973.Tibetan,Variscan,and Precambrianbasement reactivation:Products of continental collision.TheJournal of Geology,81(6):683-692.
England P,Houseman G.1989.Extension during continentalconvergence,with application to the Tibetan Plateau.J.Geophys.Res.:Solid Earth(1978—2012),94(B12):17561-17579.
Forsyth D W.1985.Subsurface loading and estimates of the flexuralrigidity of continental lithosphere.J.Geophys.Res.:SolidEarth(1978—2012),90(B14):12623-12632.
Gao R Q,Zhao Z Z.2001.The Frontier Petroleum Exploration inChina-Petroleum Geology of Qinghai-Tibetan Plateau(inChinese).Beijing:Petroleum Industry Press,28-30.
Jiang M,GalvéA,Hirn A,et al.2006.Crustal thickening andvariations in architecture from the Qaidam basin to the QangTang(North-Central Tibetan Plateau)from wide-anglereflection seismology.Tectonophysics,412(3-4):121-140.
Jiang X D,Jin Y,McNutt M K.2004.Lithospheric deformationbeneath the Altyn Tagh and West Kunlun faults from recentgravity surveys.J.Geophys.Res.:Solid Earth(1978—2012),109(B5):B05406,doi:10.1029/2003JB002444.
Jiang X D,Jin Y.2005.Mapping the deep lithospheric structurebeneath the eastern margin of the Tibetan Plateau from gravityanomalies.J.Geophys.Res.:Solid Earth(1978—2012),110(B7):B07407,doi:10.1029/2004JB003394.
Jin Y,Jiang X D.2002.Lithosphere Dynamics(in Chinese).Beijing:Sciences Press,113-119.
Jin Y,McNutt M K,Zhu Y S.1994.Evidence from gravity andtopography data for folding of Tibet.Nature,371:669-674.
Jin Y,Wang E,Jiang X D.2008.The dynamic support anddecoupling process of the Tibetan lithosphere based on theintegration of flexural modeling with other geological andgeophysical studies.//Burchfiel B C,Wang E.Investigationsinto the Tectonics of the Tibetan Plateau,GSA Special Paper,444:89-104.
Jordan T A,Watts A B.2005.Gravity anomalies,flexure and theelastic thickness structure of the India-Eurasia collisionalsystem.Earth and Planetary Science Letters,236(3-4):732-750,doi:10.1016/j.epsl.2005.05.036.
Kind R,Yuan X,Saul J,et al.2002.Seismic images of crust andupper mantle beneath Tibet:Evidence for Eurasian platesubduction.Science,298(5596):1219-1221.
Kirby J F,Swain C J.2008.An accuracy assessment of the fanwavelet coherence method for elastic thickness estimation.Geochemistry,Geophysics,Geosystems,9(3):Q03022,doi:10.1029/2007GC001773.
Kogan M G,McNutt M K.1993.Gravity field over northernEurasia and variations in the strength of the upper mantle.Science,259(5094):473-479.
Li Q S,Peng S P,Gao R,et al.2003.Seismic evidence of thebasement uplift in the Bayan Har tectonic belt,Qinghai,andits tectonic significance.Geological Bulletin of China(inChinese),22(10):782-788.
Li S L,Zhang X K,Zhang C K,et al.2002.A preliminary study onthe crustal velocity structure of Maqin-Lanzhou-Jingbian bymeans of deep seismic sounding profile.Chinese J.Geophys.(in Chinese),45(2):210-217.
Liu M J,Li S L,Fang S M,et al.2008.Study on crustalcomposition and geodynamics using seismic velocities in thenortheastern margin of the Tibetan Plateau.Chinese J.Geophys.(in Chinese),51(2):412-430.
McNutt M K.1983.Influence of plate subduction on isostaticcompensation in northern California.Tectonics,2(4):399-415.
Meng Q R,Fang X.2008.Cenozoic tectonic development of theQaidam basin in the northeastern Tibetan Plateau.GSA SpecialPaper,444:1-24.
Ojeda G Y,Whitman D.2002.Effect of windowing on lithosphereelastic thickness estimates obtained via the coherence method:results from northern South America.J.Geophys.Res.:SolidEarth(1978—2012),107(B11):ETG 3-1-ETG 3-12,doi:10.1029/200JB000114.
Parker R L.1973.The rapid calculation of potential anomalies.Geophys,J.R.Astr.Soc.,31(4):447-455.
Pérez-GussinyéM,Lowry A R,Phipps Morgan J,et al.2008.Effective Elastic thickness variations along the Andean marginand their relationship to subduction geometry.Geochemistry,Geophysics,Geosystems,9(2):Q02003,doi:10.1029/2007GC001786.
Pérez-GussinyéM,Lowry A R,Watts A B,et al.2004.On therecovery of effective elastic thickness using spectral methods:examples from synthetic data and from the FennoscandianShield.J.Geophys.Res.:Solid Earth(1978—2012),109(B10),doi:10.1029/2003JB002788.
Pérez-GussinyéM,Lowry A R,Watts A B.2007.Effective elasticthickness of South America and its implications for intracontinentaldeformation.Geochemistry,Geophysics,Geosystems,8(5):Q05009,doi:10.1029/2006GC001511.
Royden L H,Burchfiel B C,King R W,et al.1997.Surfacedeformation and lower crustal flow in Eastern Tibet.Science,276(5313):788-790.
Royden L H,Burchfiel B C,van der Hilst R D.2008.Thegeological evolution of the Tibetan Plateau.Science,321(5892):1054-1058.
Simons F J,van der Hilst R D,Zuber M T.2000.Spatiospectrallocalization of isostatic coherence anisotropy in Australia and itsrelation to seismic anisotropy:Implications for lithosphericdeformation.J.Geophys.Res.:Solid Earth(1978—2012),108(B5):19163-19184.
Stewart J,Watts A B.1997.Gravity anomalies and spatialvariations of flexural rigidity at mountain ranges.J.Geophys.Res.:Solid Earth(1978—2012),102(B3):5327-5352.
Swain C J,Kirby J F.2006.An effective elastic thickness map ofAustralia from wavelet transforms of gravity and topographyusing Forsyth′s method.Geophys.Res.Lett.,33(2),doi:10.1029/2005GL025090.
Tapponnier P,Xu Z Q,Roger F,et al.2001.Oblique stepwise riseand growth of the Tibet Plateau.Science,294(5547):1671-1677.
Teng J W,Zhang Z J,Zhang X K,et al.2013.Investigation of theMoho discontinuity beneath the Chinese mainland using deepseismic sounding profiles.Tectonophysics,608:202-216,doi:10.1016/j.tecto.2012.11.024.
Thomson D J.1982.Spectrum estimation and harmonic analysis.Proceedings of the IEEE,70(9):1055-1096.
Torne M,Fernàndez M,Comas M C,et al.2000.Lithosphericstructure beneath the Alboran Basin:results from 3Dgravitymodeling and tectonic relevance.J.Geophys.Res.:SolidEarth(1978—2012),105(B2):3209-3228.
Van Wees J D,Cloetingh S.1994.A finite-difference technique toincorporate spatial variations in rigidity and planar faults into 3-D models for lithospheric flexure.Geophys.J.Int.,117(1):179-195.
Wang Q S,An Y L.2001.Gravity field and deep structure ofMadoi-Shama region in eastern Qinghai-Xizang(Tibetan)plateau.Progress in Geophysics(in Chinese),16(4):4-10.
Wang Y X,Mooney W D,Yuan X C,et al.2013.Crustal Structureof the Northeastern Tibetan Plateau from the Southern TarimBasin to the Sichuan Basin,China.Tectonophysics,584:191-208.
Zhang Z J,Bai Z M,Klemperer S L,et al.2013.Crustal structureacross northeastern Tibet from wide-angle seismic profiling:Constraints on the Caledonian Qilian orogeny and its reactivation.Tectonophysics,606:140-159,doi:10.1016/j.tecto.2013.02.040.
Zhang Z J,Deng Y F,Teng J W,et al.2011a.An overview of thecrustal structure of the Tibetan plateau after 35years of deepseismic soundings.Journal of Asian Earth Sciences,40(4):977-989.
Zhang Z J,Klemperer S,Bai Z M,et al.2011b.Crustal structureof the Paleozoic Kunlun orogeny from an active-source seismicprofile between Moba and Guide in East Tibet,China.Gondwana Research,19(4):994-1007.
Zhang Z J,Yuan X H,Chen Y,et al.2010.Seismic signature ofthe collision between the east Tibetan escape flow and theSichuan Basin.Earth and Planetary Science Letters,292(3-4):254-264.
Zhao W L,Morgan W J.1987.Injection of Indian crust into Tibetanlower crust:a two-dimensional finite element model study.Tectonics,6(4):489-504.
高瑞祺,赵政璋.2001.中国油气新区勘探-第六卷-青藏高原石油地质.北京:石油工业出版社,28-30.
金煜,姜效典.2002.岩石圈动力学.北京:科学出版社,113-119.
李秋生,彭苏萍,高锐等.2003.青藏高原北部巴颜喀拉构造带基底隆起的地震学证据.地质通报,22(10):782-788.
李松林,张先康,张成科等.2002.玛沁—兰州—靖边地震测深剖面地壳速度结构的初步研究.地球物理学报,45(2):210-217.
刘明军,李松林,方盛明等.2008.利用地震波速研究青藏高原东北缘地壳组成及其动力学.地球物理学报,51(2):412-430.
王谦身,安玉林.2001.青藏高原东部玛多—沙马地区的重力场与深部构造.地球物理学进展,16(4):4-10.
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