中亚造山带东段软流圈分布特征——基于长周期大地电磁探测的结果
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摘要
中亚造山带东段经历了古亚洲洋、蒙古—鄂霍茨克洋和古太平洋构造体制的多重作用,多期次的构造活动不仅改造了地形地貌、岩石圈结构,同时也改造了软流圈分布,因此对软流圈结构研究具有重要的科学意义.为了揭示复杂多重构造体系下软流圈的分布特征,完成了中亚造山带东段约1800km长大地电磁测深剖面,并对数据进行非线性共轭梯度反演,获得二维电性结构模型.研究发现:中亚造山带东段岩石圈内部存在多处低阻异常,地表多对应第四纪火山群或古缝合带,表明这些低阻异常与软流圈上侵有关.软流圈呈现高导特征,南部略薄,电阻率值为10～30Ωm,北部厚度较大,电阻率值为10～0.1Ωm,这种电性结构特征体现了中亚造山带东段软流圈南北两侧厚度、部分熔融程度的不均一性.而已有的层析成像结果显示中亚造山带软流圈东西向则呈现东厚西薄的特征.结合区域地质,提出软流圈与岩石圈一样在碰撞造山过程中厚度、部分熔融程度也会随之变化的动力学认识.中亚造山带东段软流圈主要经历了古亚洲洋构造体系、蒙古—鄂霍茨克构造体系和太平洋构造体系三阶段的构造事件影响,因此中亚造山带东段软流圈的南北向差异,推断为古亚洲洋闭合早于鄂霍茨克洋闭合的时限差异所致,东西向差异则主要受太平洋构造体系的影响.
The eastern section of the Central Asian orogenic belt experienced multiple functions of the Paleo-Asian Ocean,the Mongolia-Okhotsk Ocean,and the Paleo-Pacific tectonic system.The multi-phase tectonic activities have not only reshaped the topography and lithosphere structure,but also changed the geometry of the asthenosphere beneath this belt.To reveal the characteristics of the asthenosphere under the complex background system,we acquired an electromagnetic sounding profile about 1800 km long in the eastern part of the Central Asia orogenic belt.Non-linear conjugate gradient inversion was performed to the data to establish a two-dimensional electrical structure model.The results show that there are many low resistivity anomalies inside the lithosphere beneath this region,which,on the surface,mostly correspond to the Quaternary volcanic groups or ancient suture zones.It implies that these low resistance anomalies are related to asthenosphere uplifting invasion.The asthenosphere exhibits high conductivity and is slightly thin in the south with a resistivity value of 10 to 30Ωm and thicker in the north with a resistivity value of 10 to 0.1Ωm.This electrical structure evidences the heterogeneity of the thickness,and partial melting of the asthenosphere on the north and south sides in the eastern Central Asian orogenic belt.The existing tomographic results show that the thickness of the asthenosphere in this orogenic zone is thicker in the east and thinner in the west.Combining with regional geology,we propose that like the lithosphere,the thickness and partial melting of the asthenosphere also changed in the process of collision orogenesis.The asthenosphere in the eastern Central Asia Orogenic belt has undergone three stages of tectonic events:the Paleo-Asian oceanic tectonic system,the Mongolian-Ihotsk tectonic system,and the Pacific tectonic system.Therefore,we estimate that the north-south difference of the asthenosphere beneath the eastern Central Asian orogenic belt was likely caused by that the closure of the Paleo-Asian Ocean was earlier than the Okhotsk Ocean.And The east-west variation was related with the influence of the Pacific tectonic system.
The eastern section of the Central Asian orogenic belt experienced multiple functions of the Paleo-Asian Ocean,the Mongolia-Okhotsk Ocean,and the Paleo-Pacific tectonic system.The multi-phase tectonic activities have not only reshaped the topography and lithosphere structure,but also changed the geometry of the asthenosphere beneath this belt.To reveal the characteristics of the asthenosphere under the complex background system,we acquired an electromagnetic sounding profile about 1800 km long in the eastern part of the Central Asia orogenic belt.Non-linear conjugate gradient inversion was performed to the data to establish a two-dimensional electrical structure model.The results show that there are many low resistivity anomalies inside the lithosphere beneath this region,which,on the surface,mostly correspond to the Quaternary volcanic groups or ancient suture zones.It implies that these low resistance anomalies are related to asthenosphere uplifting invasion.The asthenosphere exhibits high conductivity and is slightly thin in the south with a resistivity value of 10 to 30Ωm and thicker in the north with a resistivity value of 10 to 0.1Ωm.This electrical structure evidences the heterogeneity of the thickness,and partial melting of the asthenosphere on the north and south sides in the eastern Central Asian orogenic belt.The existing tomographic results show that the thickness of the asthenosphere in this orogenic zone is thicker in the east and thinner in the west.Combining with regional geology,we propose that like the lithosphere,the thickness and partial melting of the asthenosphere also changed in the process of collision orogenesis.The asthenosphere in the eastern Central Asia Orogenic belt has undergone three stages of tectonic events:the Paleo-Asian oceanic tectonic system,the Mongolian-Ihotsk tectonic system,and the Pacific tectonic system.Therefore,we estimate that the north-south difference of the asthenosphere beneath the eastern Central Asian orogenic belt was likely caused by that the closure of the Paleo-Asian Ocean was earlier than the Okhotsk Ocean.And The east-west variation was related with the influence of the Pacific tectonic system.
引文
Barrell J.1914.The strength of the earth's crust partⅡ.Regional distribution of isostatic compensation.The Journal of Geology,22(2):145-165.
Cai J T,Chen X B.2010.Refined techniques for data processing and two-dimensional inversion in magnetotelluricⅡ:Which data polarization mode should be used in 2Dinversion.Chinese J.Geophys.(in Chinese),53(11):2703-2714,doi:10.3969/j.issn.0001-5733.2010.11.018.
Cai X L,Zhu J S,Cao J M,et al.2006.3Dstructure of the asthenosphere beneath China and adjacent land and sea areas and its interaction with the lithosphere.Geology in China(in Chinese),33(4):804-815.
Chen X B,Cai J T,Wang L F,et al.2014.Refined techniques for magnetotelluric data processing and two-dimensional inversion(IV):Statistical image method based on multi-site,multifrequency tensor decomposition.Chinese Journal of Geophysics(in Chinese),57(6):1946-1957,doi:10.6038/cjg20140625.
Debayle E,Ricard Y.2012.A global shear velocity model of the upper mantle from fundamental and higher Rayleigh mode measurements.Journal of Geophysical Research:Solid Earth,117(B10):B10308,doi:10.1029/2012JB009288.
Deng S H,Wan C B,Yang J G.2009.Discovery of a Late Permian Angara-Cathaysia mixed flora from Acheng of Heilongjiang,China,with discussions on the closure of the Paleoasian Ocean.Sci.China Ser.D-Earth Sci.,52(11):1746-1755.
Farquharson C G,Oldenburg D W,Kowalczyk P.2004.Threedimensional inversion of MT data from the Turquoise Ridge mine,Nevada.∥SEG Int′l Exposition and 74th Annual Meeting.Denver,Colorado:SEG.
Geng S F,Liu P,Zheng H W,et al.2012.A tentative discussion and new recognition of Mesozoic geodynamic mechanism in eastern China.Geological Bulletin of China(in Chinese),31(7):1061-1068.
Gu Z J,Sun T Z,Tao J L.2001.Experiment of wet peridotite under high temperature-pressure and asthenosphere genesis.Progress in Geophysics(in Chinese),16(3):40-46.
Hu Y C,Li T L,Fan C S,et al.2015.Three-dimensional tensor controlled-source electromagnetic modeling based on the vector finite-element method.Applied Geophysics,12(1):35-46.
Huang S Q,Dong S W,Hu J M,et al.2016.The formation and tectonic evolution of the Mongol-Okhotsk Belt.Acta Geologica Sinica(in Chinese),90(9):2192-2205.
Kroner U,Romer R L.2013.Two plates-Many subduction zones:The Variscan orogeny reconsidered.Gondwana Research,24(1):298-329.
Kroner U,Roscher M,Romer R L.2016.Ancient plate kinematics derived from the deformation pattern of continental crust:Paleoand Neo-Tethys opening coeval with prolonged Gondwana-Laurussia convergence.Tectonophysics,681:220-233.
Li S Z,Yang C,Zhao S J,et al.2016.Global early paleozoic orogens(Ⅱ):subduction-accretionary-type orogeny.Journal of Jilin University(Earth Science Edition)(in Chinese),46(4):968-1004.
Lou X H,Ai Y S,Zhang Y Y,et al.2017.Study of lithospheric structure in the central and western North China craton.Progress in Geophysics(in Chinese),32(4):1458-1464,doi:10.6038/pg20170406.
Ren J Y,Li S T.2000.Spreading and dynamic setting of marginal basins of the western Pacific.Earth Science Frontiers(in Chinese),7(3):203-213.
Rodi W,Mackie R L.2000.Nonlinear conjugate gradients algorithm for2-D magnetotelluric inversion.Geophysics,66(1):174-187.
Rychert C A,Shearer P M.2009.A global view of the lithosphereasthenosphere boundary.Science,324(5926):495-498.
Tang J,Zhao G Z,Wang J J,et al.2006.Study of the formation mechanism for volcanism in Northeast China based on deep electric structure.Acta Petrologica Sinica(in Chinese),22(6):1503-1510.
Tauzin B,Debayle E,Wittlinger G.2010.Seismic evidence for a global low-velocity layer within the earth′s upper mantle.Nature Geoscience,3(10):718-721.
Van der Voo R,Spakman W,Bijwaard H.1999.Tethyan subducted slabs under India.Earth&Planetary Science Letters,171(1):7-20.
Wei W B,Jin S,Ye G F,et al.2009.Conductivity structure and rheological property of lithosphere in Southern Tibet inferred from super-broadband magnetotelluric sounding.Science in China Series D:Earth Sciences,39(11):1591-1606.
Wu G Y.2014.Late Paleozoic evolution of south branch of Central Asian Orogenic Belt:With reference to creation of the MiddleLate Permian residual marine basins bordering Mongolia and China.Journal of Palaeogeography(in Chinese),16(6):907-925.
Zhang L T,Wei W B,Jin S,et al.2011.Studies on the temperature dependence of electrical conductivity of upper mantle rocks.Progress in Geophysics(in Chinese),26(2):505-510,doi:10.3969/j.issn.1004-2903.2011.02.015.
Zhu J S,Cao J M,Cai X L,et al.2002.High resolution surface wave tomography in East Asia and West Pacific marginal seas.Chinese J.Geophys.(in Chinese),45(5):646-664.
Zhu J S,Cao J M,Cai X L,et al.2003.Study for three-dimensional structure of earth interior and geodynamics in China and adjacent land and sea regions.Advance in Earth Sciences(in Chinese),18(4):497-503.
Zhu J S,Xuan R Q,Liu K,et al.2005.Studying the structure of crust and upper mantle in East Asia and west pacific marginal sea by Rayleigh surface wave.Computing Techniques for Geophysical and Geochemical Exploration(in Chinese),27(3):185-193.
蔡军涛,陈小斌.2010.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,53(11):2703-2714,doi:10.3969/j.issn.0001-5733.2010.11.018.
蔡学林,朱介寿,曹家敏等.2006.中国及邻近陆海地区软流圈三维结构及其与岩石圈的相互作用.中国地质,33(4):804-815.
陈小斌,蔡军涛,王立凤等.2014.大地电磁资料精细处理和二维反演解释技术研究(四)---阻抗张量分解的多测点-多频点统计成像分析.地球物理学报,57(6):1946-1957,doi:10.6038/cjg20140625.
邓胜徽,万传彪,杨建国.2009.黑龙江阿城晚二叠世安加拉-华夏混生植物群---兼述古亚洲洋的关闭问题.中国科学D辑:地球科学,39(12):1744-1752.
耿树方,刘平,郑洪伟等.2012.对中国东部中生代动力学机制的新认识.地质通报,31(7):1061-1068.
顾芷娟,孙天泽,陶京岭.2001.高温高压下橄榄石含水实验和软流圈成因.地球物理学进展,16(3):40-46.
黄始琪,董树文,胡健民等.2016.蒙古-鄂霍次克构造带的形成与演化.地质学报,90(9):2192-2205.
李三忠,杨朝,赵淑娟等.2016.全球早古生代造山带(Ⅱ):俯冲-增生型造山.吉林大学学报(地球科学版),46(4):968-1004.
娄辛辉,艾印双,张耀阳等.2017.华北克拉通中西部岩石圈结构研究.地球物理学进展,32(4):1458-1464,doi:10.6038/pg20170406.
任建业,李思田.2000.西太平洋边缘海盆地的扩张过程和动力学背景.地学前缘,7(3):203-213.
汤吉,赵国泽,王继军等.2006.基于地下电性结构探讨中国东北活动火山形成机制.岩石学报,22(6):1503-1510.
魏文博,金胜,叶高峰等.2009.藏南岩石圈导电性结构与流变性-超宽频带大地电磁测深研究结果.中国科学(D辑:地球科学),39(11):1591-1606.
吴根耀.2014.中亚造山带南带晚古生代演化:兼论中蒙交界区中-晚二叠世残留海盆的形成.古地理学报,16(6):907-925.
张乐天,魏文博,金胜等.2011.上地幔岩石的电性-温度依赖关系研究.地球物理学进展,26(2):505-510,doi:10.3969/j.issn.1004-2903.2011.02.015.
朱介寿,曹家敏,蔡学林等.2002.东亚及西太平洋边缘海高分辨率面波层析成像.地球物理学报,45(5):646-664.
朱介寿,曹家敏,蔡学林等.2003.中国及邻近陆域海域地球内部三维结构及动力学研究.地球科学进展,18(4):497-503.
朱介寿,宣瑞卿,刘魁等.2005.用瑞利面波研究东亚及西太平洋地壳上地幔三维结构.物探化探计算技术,27(3):185-193.
Cai J T,Chen X B.2010.Refined techniques for data processing and two-dimensional inversion in magnetotelluricⅡ:Which data polarization mode should be used in 2Dinversion.Chinese J.Geophys.(in Chinese),53(11):2703-2714,doi:10.3969/j.issn.0001-5733.2010.11.018.
Cai X L,Zhu J S,Cao J M,et al.2006.3Dstructure of the asthenosphere beneath China and adjacent land and sea areas and its interaction with the lithosphere.Geology in China(in Chinese),33(4):804-815.
Chen X B,Cai J T,Wang L F,et al.2014.Refined techniques for magnetotelluric data processing and two-dimensional inversion(IV):Statistical image method based on multi-site,multifrequency tensor decomposition.Chinese Journal of Geophysics(in Chinese),57(6):1946-1957,doi:10.6038/cjg20140625.
Debayle E,Ricard Y.2012.A global shear velocity model of the upper mantle from fundamental and higher Rayleigh mode measurements.Journal of Geophysical Research:Solid Earth,117(B10):B10308,doi:10.1029/2012JB009288.
Deng S H,Wan C B,Yang J G.2009.Discovery of a Late Permian Angara-Cathaysia mixed flora from Acheng of Heilongjiang,China,with discussions on the closure of the Paleoasian Ocean.Sci.China Ser.D-Earth Sci.,52(11):1746-1755.
Farquharson C G,Oldenburg D W,Kowalczyk P.2004.Threedimensional inversion of MT data from the Turquoise Ridge mine,Nevada.∥SEG Int′l Exposition and 74th Annual Meeting.Denver,Colorado:SEG.
Geng S F,Liu P,Zheng H W,et al.2012.A tentative discussion and new recognition of Mesozoic geodynamic mechanism in eastern China.Geological Bulletin of China(in Chinese),31(7):1061-1068.
Gu Z J,Sun T Z,Tao J L.2001.Experiment of wet peridotite under high temperature-pressure and asthenosphere genesis.Progress in Geophysics(in Chinese),16(3):40-46.
Hu Y C,Li T L,Fan C S,et al.2015.Three-dimensional tensor controlled-source electromagnetic modeling based on the vector finite-element method.Applied Geophysics,12(1):35-46.
Huang S Q,Dong S W,Hu J M,et al.2016.The formation and tectonic evolution of the Mongol-Okhotsk Belt.Acta Geologica Sinica(in Chinese),90(9):2192-2205.
Kroner U,Romer R L.2013.Two plates-Many subduction zones:The Variscan orogeny reconsidered.Gondwana Research,24(1):298-329.
Kroner U,Roscher M,Romer R L.2016.Ancient plate kinematics derived from the deformation pattern of continental crust:Paleoand Neo-Tethys opening coeval with prolonged Gondwana-Laurussia convergence.Tectonophysics,681:220-233.
Li S Z,Yang C,Zhao S J,et al.2016.Global early paleozoic orogens(Ⅱ):subduction-accretionary-type orogeny.Journal of Jilin University(Earth Science Edition)(in Chinese),46(4):968-1004.
Lou X H,Ai Y S,Zhang Y Y,et al.2017.Study of lithospheric structure in the central and western North China craton.Progress in Geophysics(in Chinese),32(4):1458-1464,doi:10.6038/pg20170406.
Ren J Y,Li S T.2000.Spreading and dynamic setting of marginal basins of the western Pacific.Earth Science Frontiers(in Chinese),7(3):203-213.
Rodi W,Mackie R L.2000.Nonlinear conjugate gradients algorithm for2-D magnetotelluric inversion.Geophysics,66(1):174-187.
Rychert C A,Shearer P M.2009.A global view of the lithosphereasthenosphere boundary.Science,324(5926):495-498.
Tang J,Zhao G Z,Wang J J,et al.2006.Study of the formation mechanism for volcanism in Northeast China based on deep electric structure.Acta Petrologica Sinica(in Chinese),22(6):1503-1510.
Tauzin B,Debayle E,Wittlinger G.2010.Seismic evidence for a global low-velocity layer within the earth′s upper mantle.Nature Geoscience,3(10):718-721.
Van der Voo R,Spakman W,Bijwaard H.1999.Tethyan subducted slabs under India.Earth&Planetary Science Letters,171(1):7-20.
Wei W B,Jin S,Ye G F,et al.2009.Conductivity structure and rheological property of lithosphere in Southern Tibet inferred from super-broadband magnetotelluric sounding.Science in China Series D:Earth Sciences,39(11):1591-1606.
Wu G Y.2014.Late Paleozoic evolution of south branch of Central Asian Orogenic Belt:With reference to creation of the MiddleLate Permian residual marine basins bordering Mongolia and China.Journal of Palaeogeography(in Chinese),16(6):907-925.
Zhang L T,Wei W B,Jin S,et al.2011.Studies on the temperature dependence of electrical conductivity of upper mantle rocks.Progress in Geophysics(in Chinese),26(2):505-510,doi:10.3969/j.issn.1004-2903.2011.02.015.
Zhu J S,Cao J M,Cai X L,et al.2002.High resolution surface wave tomography in East Asia and West Pacific marginal seas.Chinese J.Geophys.(in Chinese),45(5):646-664.
Zhu J S,Cao J M,Cai X L,et al.2003.Study for three-dimensional structure of earth interior and geodynamics in China and adjacent land and sea regions.Advance in Earth Sciences(in Chinese),18(4):497-503.
Zhu J S,Xuan R Q,Liu K,et al.2005.Studying the structure of crust and upper mantle in East Asia and west pacific marginal sea by Rayleigh surface wave.Computing Techniques for Geophysical and Geochemical Exploration(in Chinese),27(3):185-193.
蔡军涛,陈小斌.2010.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,53(11):2703-2714,doi:10.3969/j.issn.0001-5733.2010.11.018.
蔡学林,朱介寿,曹家敏等.2006.中国及邻近陆海地区软流圈三维结构及其与岩石圈的相互作用.中国地质,33(4):804-815.
陈小斌,蔡军涛,王立凤等.2014.大地电磁资料精细处理和二维反演解释技术研究(四)---阻抗张量分解的多测点-多频点统计成像分析.地球物理学报,57(6):1946-1957,doi:10.6038/cjg20140625.
邓胜徽,万传彪,杨建国.2009.黑龙江阿城晚二叠世安加拉-华夏混生植物群---兼述古亚洲洋的关闭问题.中国科学D辑:地球科学,39(12):1744-1752.
耿树方,刘平,郑洪伟等.2012.对中国东部中生代动力学机制的新认识.地质通报,31(7):1061-1068.
顾芷娟,孙天泽,陶京岭.2001.高温高压下橄榄石含水实验和软流圈成因.地球物理学进展,16(3):40-46.
黄始琪,董树文,胡健民等.2016.蒙古-鄂霍次克构造带的形成与演化.地质学报,90(9):2192-2205.
李三忠,杨朝,赵淑娟等.2016.全球早古生代造山带(Ⅱ):俯冲-增生型造山.吉林大学学报(地球科学版),46(4):968-1004.
娄辛辉,艾印双,张耀阳等.2017.华北克拉通中西部岩石圈结构研究.地球物理学进展,32(4):1458-1464,doi:10.6038/pg20170406.
任建业,李思田.2000.西太平洋边缘海盆地的扩张过程和动力学背景.地学前缘,7(3):203-213.
汤吉,赵国泽,王继军等.2006.基于地下电性结构探讨中国东北活动火山形成机制.岩石学报,22(6):1503-1510.
魏文博,金胜,叶高峰等.2009.藏南岩石圈导电性结构与流变性-超宽频带大地电磁测深研究结果.中国科学(D辑:地球科学),39(11):1591-1606.
吴根耀.2014.中亚造山带南带晚古生代演化:兼论中蒙交界区中-晚二叠世残留海盆的形成.古地理学报,16(6):907-925.
张乐天,魏文博,金胜等.2011.上地幔岩石的电性-温度依赖关系研究.地球物理学进展,26(2):505-510,doi:10.3969/j.issn.1004-2903.2011.02.015.
朱介寿,曹家敏,蔡学林等.2002.东亚及西太平洋边缘海高分辨率面波层析成像.地球物理学报,45(5):646-664.
朱介寿,曹家敏,蔡学林等.2003.中国及邻近陆域海域地球内部三维结构及动力学研究.地球科学进展,18(4):497-503.
朱介寿,宣瑞卿,刘魁等.2005.用瑞利面波研究东亚及西太平洋地壳上地幔三维结构.物探化探计算技术,27(3):185-193.
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