华北克拉通岩石圈三维密度结构
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摘要
显生宙以来华北克拉通岩石圈遭到破坏,这一现象的科学问题已受到世界地学家广泛关注.本文首先将地震层析成像反演得到的P波速度扰动转化为密度扰动,以此作为初始密度模型,然后利用布格重力异常反演得到了华北克拉通岩石圈高分辨三维密度结构.为了避开大型稀疏矩阵求逆计算,提高计算效率,我们将代数重构技术用于密度反演解算.反演结果表明:华北克拉通岩石圈密度在横向和纵向上均存在明显的不均匀性,密度分布形态与地表构造格局有很好的相关性;研究区地壳整体表现为低密度异常,地壳以下岩石圈部分则以高密度异常为主;鄂尔多斯块体地壳范围内以低密度异常为主,80～120km深度上为呈南北两端集中分布的高密度异常,并分别与秦岭造山带和阴山造山带的高密度异常分布相连,这暗示了鄂尔多斯块体可能受到了来自其南北两端造山带深部动力学过程的影响;80～120km深度上,华北克拉通东部地区呈现出显著的南北向非均匀的高密度异常,这表明遭到破坏后该地区上地幔物质分布具有强烈的南北向非均匀性.
Geoscientists all over the world paid a broad attention to the lithosphere of North China Craton(NCC),which was destructed since phanerozoic.A three dimensional P-wave velocity model obtained from seismic tomography was used to construct an initial 3D density model.Then,we got high resolution three dimensional density distributions of the lithosphere in NCC by gravity inversion using bouguer gravity anomaly.In order to improve the inversion speed,Algebraic Reconstruction Technique(ART) was applied for it can avoid the large and sparse matrix inversion of observation equations by using row iterative technique.The results indicate as follows: density distributions of lithosphere beneath North China Craton are inhomogeneous both in horizontal direction and vertical direction.And the density distribution underground is coherent with surfical tectonic.In NCC crust the density anomaly is low,while it is strongly high at 80～120 km depth.The Ordos block crust exhibit a low density distribution,and high density anomaly with big amplitude exists at 80～120 km.The high density distribution is conjoint with the high density anomalies of Qinling and Yinshan orogen in the south and north,respectively.That may indicate that Ordos block underwent the deep dynamic process from orogen in the south and north.High density anomaly is visible beneath the mid Taihang Mountain Orogen and eastern basin region at 80～120 km depth.At the same depth,remarkable high density anomalies exist beneath eastern of NCC with strong lateral heterogeneous in NS direction.It indicates that the upper mantles are inhomogeneous in NS direction beneath this region.
Geoscientists all over the world paid a broad attention to the lithosphere of North China Craton(NCC),which was destructed since phanerozoic.A three dimensional P-wave velocity model obtained from seismic tomography was used to construct an initial 3D density model.Then,we got high resolution three dimensional density distributions of the lithosphere in NCC by gravity inversion using bouguer gravity anomaly.In order to improve the inversion speed,Algebraic Reconstruction Technique(ART) was applied for it can avoid the large and sparse matrix inversion of observation equations by using row iterative technique.The results indicate as follows: density distributions of lithosphere beneath North China Craton are inhomogeneous both in horizontal direction and vertical direction.And the density distribution underground is coherent with surfical tectonic.In NCC crust the density anomaly is low,while it is strongly high at 80～120 km depth.The Ordos block crust exhibit a low density distribution,and high density anomaly with big amplitude exists at 80～120 km.The high density distribution is conjoint with the high density anomalies of Qinling and Yinshan orogen in the south and north,respectively.That may indicate that Ordos block underwent the deep dynamic process from orogen in the south and north.High density anomaly is visible beneath the mid Taihang Mountain Orogen and eastern basin region at 80～120 km depth.At the same depth,remarkable high density anomalies exist beneath eastern of NCC with strong lateral heterogeneous in NS direction.It indicates that the upper mantles are inhomogeneous in NS direction beneath this region.
引文
[1]邓金福,苏尚国,刘翠等.关于华北克拉通燕山期岩石圈减薄的机制与过程的讨论:是拆沉,还是热侵蚀和化学交代?地学前缘,2006,13(2):105-119.Deng J F,Su S G,Liu C,et al.Discussion on the lithosphericthinning of the North China Craton:delamination?or thermalerosion and chemical metasomatism?Earth Science Frontiers(inChinese),2006,13(2):105-119.
[2]郑建平.不同时空背景幔源物质对比与华北深部岩石圈破坏和增生置换过程.科学通报,2009,54(14):1990-2007.Zheng J P.Comparison of mantle-derived matierals fromdifferent spatiotemporal settings:Implications for destructiveand accretional processes of the North China Craton.ChineseSci Bull.(in Chinese),2009,54(14):3397-3416,doi:10.1007/s11434-009-0308-y.
[3]嘉世旭,张先康.华北不同构造块体地壳结构及其对比研究.地球物理学报,2005,48(3):611-620.Jia S X,Zhang X K.Crustal structure and comparison ofdifferent tectonic blocks in North China.Chinese J.Geophys.(in Chinese),2005,48(3):611-620.
[4]Tang Y J,Zhang H F,Ying J F.Asthenosphere-lithosphericmantle interaction in an extensional regime:Implication fromthe geochemistry of Cenozoic basalts from Taihang Mountains,North China Craton.Chemical Geology,2006,233:309-327.
[5]Zhu R X,Zheng T Y.Destruction geodynamics of the NorthChina Craton and its Paleoproterozoic plate tectonics.ChineseSci Bull.,2009,54(19):3354-3366,doi:10.1007/s11434-009-0451-5.
[6]Chen L.Concordant structural variations from the surface tothe base of the upper mantle in the North China Craton andits tectonic implications.Lithos,2010,120(1-2):96-115.
[7]吴福元,徐义刚,高山等.华北岩石圈减薄与克拉通破坏研究的主要学术争论.岩石学报,2008,24(6):1145-1174.Wu F Y,Xu Y G,Gao S,et al.Lithospheric thinning anddestruction of the North China Craton.Acta PetrologicaSinica(in Chinese),2008,24(6):1145-1174.
[8]陈立华,宋仲和.华北地区地壳上地幔P波速度结构.地球物理学报,1990,33(5):540-546.Chen L H,Song Z H.Crustal-upper mantle P wave velocitystructure beneath northern China.Chinese J.Geophys.(inChinese),1990,33(5):540-546.
[9]陈国英,宋仲和,安昌强等.华北地区三维地壳上地幔结构.地球物理学报,1991,34(2):172-181.Chen G Y,Song Z H,An C Q,et al.Three-dimensionalcrust and upper mantle structure of the North China region.Chinese J.Geophys.(in Chinese),1991,34(2):172-181.
[10]段永红,张先康,方盛明.华北地区上部地壳结构的三维有限差分层析成像.地球物理学报,2002,45(3):362-369.Duan Y H,Zhang X K,Fang S M.Three-dimensional finite-difference tomography of velocity structure of the uppercrustal in north china.Chinese J.Geophys.(in Chinese),2002,45(3):362-369.
[11]Hearn T M,Wang S Y,Ni J F,et al.Uppermost mantlevelocities beneath China and surrounding regions.J.Geophys.Res.,2004,109:B11301.
[12]彭艳菊,黄忠贤,苏伟等.中国大陆及邻区海域地壳上地幔各向异性研究.地球物理学报,2007,50(3):752-759.Peng Y J,Huang Z X,Su W,et al.Anisotropy in crust andupper mantle beneath China continent and its adjacent seas.Chinese J.Geophys.(in Chinese),2007,50(3):752-759.
[13]Zheng T Y,Chen L,Zhao L,et al.Crust-mantle structuredifference across the gravity gradient zone in North ChinaCraton:Seismic image of the thinned continental crust.Phys.Earth Planet.Interiors,2006,159(1-2):43-58.
[14]Zhao L,Allen R M,Zheng T Y,et al.Reactivation of anArchean craton:Constraints from P-and S-wave tomographyin North China.Geophys.Res.Lett.,2009,36:L17306,doi:10.1029/2009GL039781.
[15]Tian Y,Zhao D P,Sun R M,et al.Seismic imaging of thecrust and upper mantle beneath the North China Craton.Phys.Earth Planet.Interiors,2009,172(3-4):169-182.
[16]Huang Z X,Li H Y,Zheng Y J,et al.The lithosphere ofNorth China Craton from surface wave tomography.Phys.Earth Planet.Interiors.,2009,288(1-2):164-173.
[17]方剑.华北地区岩石圈三维密度分布.物化与物探,1996,23(3):179-184.Fang J.Three-dimensional density distribution of lithospherein North China.Geophysical&Geochemical Exploration(inChinese),1996,23(3):179-184.
[18]Zhang Z J,Zhang X,Badal J.Composition of the crustbeneath southeastern China derived from an integratedgeophysical data set.J.Geophys.Res.,2008,113:B04417.
[19]高山,章军锋,许文良等.拆沉作用与华北克拉通破坏.科学通报,2009,54(14):1962-1973.Gao S,Zhang J F,Xu W L,et al.Delamination anddestruction of the North China Craton.Chinese Sci.Bull.(in Chinese),2009,54(14):1962-1973,doi:10.1007/s11434-009-0395-9.
[20]高山,金振民.拆沉作用(delamination)及其壳-幔演化动力学意义.地质科技情报,1997,16(1):1-9.Gao S,Jin Z M.Delamination and its geodynamicalsignificance for the crust-mantle evolution.Geological Scienceand Technology Information(in Chinese),1997,16(1):1-9.
[21]郑伟,许厚泽,钟敏等.基于半解析法有效和快速估计GRACE全球重力场的精度.地球物理学报,2008,51(6):1704-1710.Zheng W,Xu H Z,Zhong M,et al.Efficient and rapidestimation of the accuracy of GRACE global gravitationalfield using the semi-analytical method.Chinese J.Geophys.(in Chinese),2008,51(6):1143-1150.
[22]郑伟,许厚泽,钟敏等.GRACE卫星关键载荷实测数据的有效处理和地球重力场的精确解算.地球物理学报,2009,52(8):1966-1975.Zheng W,Xu H Z,Zhong M,et al.Effective processing ofmeasured data from GRACE key payloads and accuratedetermination of Earth′s gravitational field.Chinese J.Geophys.(in Chinese),2009,52(8):1966-1975.
[23]田有.中国华北和美国加州地壳地震层析成像研究[博士论文].北京:中国科学院地质与地球物理研究所,2008.Tian Y.Seismic imaging beneath the North China Craton andSouthern California[Ph.D.thesis](in Chinese).Beijing:Institute of Geology and Geophysics,Chinese Academy ofSciences,2008.
[24]冯锐,严惠芬,张若水.三维位场的快速反演方法及程序设计.地质学报,1986,60(4):390-403.Feng R,Yan H F,Zhang R S.The rapid inversion of 3-Dpotential field and program design.Acta Geologica Sinica(inChinese),1986,60(4):390-403.
[25]Parker R L.The rapid calculation of potential anomalies.Geophys.J.R.Astr.Soc.,1972,31(3):447-455.
[26]Bowin C.Depth of principle mass anomalies contributing tothe earth′s geoidal undulation and gravity anomalies.MarineGeodesy,1983,7(1):61-100.
[27]方剑,许厚泽.中国及邻区岩石层密度三维结构.地球物理学进展,1999,14(2):88-93.Fang J,Xu H Z.Three dimensional distribution ofliothspheric density beneath the China and its adjacentregion.Progress in Geophys.(in Chinese),1999,14(2):88-93.
[28]方剑,许厚泽.青藏高原及其邻区岩石层三维密度结构.地球物理学报,1997,40(5):661-666.Fang J,Xu H Z.Three-dimensional lithospheric densitystructure beneath Qinghai-Tibet and its adjacent area.Chinese J.Geophys.(in Chinese),1997,40(5):661-666.
[29]柯小平,王勇,许厚泽等.青藏高原地壳三维密度结构的重力反演.地球物理学进展,2009,24(2):448-455.Ke X P,Wang Y,Xu H Z,et al.The three-dimensionalcrustal density structure of the Tibetan plateau form gravityinversion.Progress in Geophys.(in Chinese),2009,24(2):448-455.
[30]邹玉华.GPS地面台网和掩星观测结合时的时变三维电离层层析[博士论文].武汉:武汉大学,2004.Zou Y H.A study of time-dependent 3-D ionospherictomography with ground-based GPS network and occultationobservations[Ph.D.thesis](in Chinese).Wuhan:WuhanUniversity,2004.
[31]滕吉文,王夫运,赵文智等.阴山造山带—鄂尔多斯盆地岩石圈层、块速度结构与深层动力过程.地球物理学报,2010,53(1):67-85.Teng J W,Wang F Y,Zhao W Z,et al.Velocity structure oflayered block and deep dynamic process in the lithospherebeneath the Yinshan orogenic belt and Ordos Basin.ChineseJ.Geophys.(in Chinese),2010,53(1):67-85.
[32]Tian X B,Teng J W,Zhang H S,et al.Structure of crustand upper mantle beneath the Ordos Block and the YinshanMountains revealed by receiver function analysis.Physics ofthe Earth and Planetary Interiors,2011,184(34):186-193.
[33]Huang J L,Zhao D P.High-resolution mantle tomography ofChina and surrounding regions.J.Geophys.Res.,2006,111:B09305.
[2]郑建平.不同时空背景幔源物质对比与华北深部岩石圈破坏和增生置换过程.科学通报,2009,54(14):1990-2007.Zheng J P.Comparison of mantle-derived matierals fromdifferent spatiotemporal settings:Implications for destructiveand accretional processes of the North China Craton.ChineseSci Bull.(in Chinese),2009,54(14):3397-3416,doi:10.1007/s11434-009-0308-y.
[3]嘉世旭,张先康.华北不同构造块体地壳结构及其对比研究.地球物理学报,2005,48(3):611-620.Jia S X,Zhang X K.Crustal structure and comparison ofdifferent tectonic blocks in North China.Chinese J.Geophys.(in Chinese),2005,48(3):611-620.
[4]Tang Y J,Zhang H F,Ying J F.Asthenosphere-lithosphericmantle interaction in an extensional regime:Implication fromthe geochemistry of Cenozoic basalts from Taihang Mountains,North China Craton.Chemical Geology,2006,233:309-327.
[5]Zhu R X,Zheng T Y.Destruction geodynamics of the NorthChina Craton and its Paleoproterozoic plate tectonics.ChineseSci Bull.,2009,54(19):3354-3366,doi:10.1007/s11434-009-0451-5.
[6]Chen L.Concordant structural variations from the surface tothe base of the upper mantle in the North China Craton andits tectonic implications.Lithos,2010,120(1-2):96-115.
[7]吴福元,徐义刚,高山等.华北岩石圈减薄与克拉通破坏研究的主要学术争论.岩石学报,2008,24(6):1145-1174.Wu F Y,Xu Y G,Gao S,et al.Lithospheric thinning anddestruction of the North China Craton.Acta PetrologicaSinica(in Chinese),2008,24(6):1145-1174.
[8]陈立华,宋仲和.华北地区地壳上地幔P波速度结构.地球物理学报,1990,33(5):540-546.Chen L H,Song Z H.Crustal-upper mantle P wave velocitystructure beneath northern China.Chinese J.Geophys.(inChinese),1990,33(5):540-546.
[9]陈国英,宋仲和,安昌强等.华北地区三维地壳上地幔结构.地球物理学报,1991,34(2):172-181.Chen G Y,Song Z H,An C Q,et al.Three-dimensionalcrust and upper mantle structure of the North China region.Chinese J.Geophys.(in Chinese),1991,34(2):172-181.
[10]段永红,张先康,方盛明.华北地区上部地壳结构的三维有限差分层析成像.地球物理学报,2002,45(3):362-369.Duan Y H,Zhang X K,Fang S M.Three-dimensional finite-difference tomography of velocity structure of the uppercrustal in north china.Chinese J.Geophys.(in Chinese),2002,45(3):362-369.
[11]Hearn T M,Wang S Y,Ni J F,et al.Uppermost mantlevelocities beneath China and surrounding regions.J.Geophys.Res.,2004,109:B11301.
[12]彭艳菊,黄忠贤,苏伟等.中国大陆及邻区海域地壳上地幔各向异性研究.地球物理学报,2007,50(3):752-759.Peng Y J,Huang Z X,Su W,et al.Anisotropy in crust andupper mantle beneath China continent and its adjacent seas.Chinese J.Geophys.(in Chinese),2007,50(3):752-759.
[13]Zheng T Y,Chen L,Zhao L,et al.Crust-mantle structuredifference across the gravity gradient zone in North ChinaCraton:Seismic image of the thinned continental crust.Phys.Earth Planet.Interiors,2006,159(1-2):43-58.
[14]Zhao L,Allen R M,Zheng T Y,et al.Reactivation of anArchean craton:Constraints from P-and S-wave tomographyin North China.Geophys.Res.Lett.,2009,36:L17306,doi:10.1029/2009GL039781.
[15]Tian Y,Zhao D P,Sun R M,et al.Seismic imaging of thecrust and upper mantle beneath the North China Craton.Phys.Earth Planet.Interiors,2009,172(3-4):169-182.
[16]Huang Z X,Li H Y,Zheng Y J,et al.The lithosphere ofNorth China Craton from surface wave tomography.Phys.Earth Planet.Interiors.,2009,288(1-2):164-173.
[17]方剑.华北地区岩石圈三维密度分布.物化与物探,1996,23(3):179-184.Fang J.Three-dimensional density distribution of lithospherein North China.Geophysical&Geochemical Exploration(inChinese),1996,23(3):179-184.
[18]Zhang Z J,Zhang X,Badal J.Composition of the crustbeneath southeastern China derived from an integratedgeophysical data set.J.Geophys.Res.,2008,113:B04417.
[19]高山,章军锋,许文良等.拆沉作用与华北克拉通破坏.科学通报,2009,54(14):1962-1973.Gao S,Zhang J F,Xu W L,et al.Delamination anddestruction of the North China Craton.Chinese Sci.Bull.(in Chinese),2009,54(14):1962-1973,doi:10.1007/s11434-009-0395-9.
[20]高山,金振民.拆沉作用(delamination)及其壳-幔演化动力学意义.地质科技情报,1997,16(1):1-9.Gao S,Jin Z M.Delamination and its geodynamicalsignificance for the crust-mantle evolution.Geological Scienceand Technology Information(in Chinese),1997,16(1):1-9.
[21]郑伟,许厚泽,钟敏等.基于半解析法有效和快速估计GRACE全球重力场的精度.地球物理学报,2008,51(6):1704-1710.Zheng W,Xu H Z,Zhong M,et al.Efficient and rapidestimation of the accuracy of GRACE global gravitationalfield using the semi-analytical method.Chinese J.Geophys.(in Chinese),2008,51(6):1143-1150.
[22]郑伟,许厚泽,钟敏等.GRACE卫星关键载荷实测数据的有效处理和地球重力场的精确解算.地球物理学报,2009,52(8):1966-1975.Zheng W,Xu H Z,Zhong M,et al.Effective processing ofmeasured data from GRACE key payloads and accuratedetermination of Earth′s gravitational field.Chinese J.Geophys.(in Chinese),2009,52(8):1966-1975.
[23]田有.中国华北和美国加州地壳地震层析成像研究[博士论文].北京:中国科学院地质与地球物理研究所,2008.Tian Y.Seismic imaging beneath the North China Craton andSouthern California[Ph.D.thesis](in Chinese).Beijing:Institute of Geology and Geophysics,Chinese Academy ofSciences,2008.
[24]冯锐,严惠芬,张若水.三维位场的快速反演方法及程序设计.地质学报,1986,60(4):390-403.Feng R,Yan H F,Zhang R S.The rapid inversion of 3-Dpotential field and program design.Acta Geologica Sinica(inChinese),1986,60(4):390-403.
[25]Parker R L.The rapid calculation of potential anomalies.Geophys.J.R.Astr.Soc.,1972,31(3):447-455.
[26]Bowin C.Depth of principle mass anomalies contributing tothe earth′s geoidal undulation and gravity anomalies.MarineGeodesy,1983,7(1):61-100.
[27]方剑,许厚泽.中国及邻区岩石层密度三维结构.地球物理学进展,1999,14(2):88-93.Fang J,Xu H Z.Three dimensional distribution ofliothspheric density beneath the China and its adjacentregion.Progress in Geophys.(in Chinese),1999,14(2):88-93.
[28]方剑,许厚泽.青藏高原及其邻区岩石层三维密度结构.地球物理学报,1997,40(5):661-666.Fang J,Xu H Z.Three-dimensional lithospheric densitystructure beneath Qinghai-Tibet and its adjacent area.Chinese J.Geophys.(in Chinese),1997,40(5):661-666.
[29]柯小平,王勇,许厚泽等.青藏高原地壳三维密度结构的重力反演.地球物理学进展,2009,24(2):448-455.Ke X P,Wang Y,Xu H Z,et al.The three-dimensionalcrustal density structure of the Tibetan plateau form gravityinversion.Progress in Geophys.(in Chinese),2009,24(2):448-455.
[30]邹玉华.GPS地面台网和掩星观测结合时的时变三维电离层层析[博士论文].武汉:武汉大学,2004.Zou Y H.A study of time-dependent 3-D ionospherictomography with ground-based GPS network and occultationobservations[Ph.D.thesis](in Chinese).Wuhan:WuhanUniversity,2004.
[31]滕吉文,王夫运,赵文智等.阴山造山带—鄂尔多斯盆地岩石圈层、块速度结构与深层动力过程.地球物理学报,2010,53(1):67-85.Teng J W,Wang F Y,Zhao W Z,et al.Velocity structure oflayered block and deep dynamic process in the lithospherebeneath the Yinshan orogenic belt and Ordos Basin.ChineseJ.Geophys.(in Chinese),2010,53(1):67-85.
[32]Tian X B,Teng J W,Zhang H S,et al.Structure of crustand upper mantle beneath the Ordos Block and the YinshanMountains revealed by receiver function analysis.Physics ofthe Earth and Planetary Interiors,2011,184(34):186-193.
[33]Huang J L,Zhao D P.High-resolution mantle tomography ofChina and surrounding regions.J.Geophys.Res.,2006,111:B09305.
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