大陆深俯冲带的地壳速度结构——东大别造山带深地震宽角反射/折射研究
摘要
在安徽大别山 (东大别 )进行的深地震宽角反射 折射探测获得 6条二维地壳速度结构剖面 .结果显示 ,东大别造山带地壳为一高速穹隆构造 ,在其核部中、下地壳变质岩出露于地表 ,波速高达 5 .0km s;在其翼部 ,上、中地壳发育速度约 6 .1km s的壳内低速层 (体 ) .莫霍面的起伏变化较大 ,中心部位深达 41km左右 ,周边地区则抬升到 32～ 34km .在晓天—磨子潭断裂一线下方莫霍面垂向错断 ,断距约 4km .东大别造山带具有大陆深俯冲 -碰撞造山带地壳结构的典型式样 .莫霍面错断与扬子陆块深俯冲有关 ,错断处表征扬子与华北陆块碰撞缝合的深部位置 .高速穹隆构造可能是两陆块碰撞挤压的产物 ,穹隆翼部上、中地壳发育的低速滑脱带 (面 )可能在碰撞期之后的地壳伸展、超高压变质岩从中地壳抬升出露于地表过程中起到重要作用 .
Six two-dimensional crustal structure profiles in the eastern Dabie, Anhui Province, have been obtained by the wide-angle reflection/refraction. The results reveal that the crust of the eastern Dabie orogen presents a high-velocity dome, the velocity in the middle- and lower-crust′s metamorphic rocks exposed on the surface in the core of the dome approaches 5.0 km/s, the low velocity layers (body) with about 6.1 km/s has developed in upper-middle crust in it′s both sides wing, the Moho discontinuity relatively largely varies and ranges from ～ 41km in the core to 32～34 km in both sides, and a 4 km Moho-offset is observed beneath along Xiaotian-Muzitan Fault. We recognize that the eastern Dabie orogen shows a velocity-pattern of typical continent-continent deep subduction/collision style. The Moho offset may be related with the deep subductionof the Yangtze Block, and represents the suture zone between the Yangtze/Sino-Korean Block collision. Therefore, the high-velocity dome may occur by collision/extrusion between the both continental Blocks and the low velocity layers (body) mentioned above may play an important role in the post-collisional crust extension and exhumation of the ultra-high press metamorphic rocks.
Six two-dimensional crustal structure profiles in the eastern Dabie, Anhui Province, have been obtained by the wide-angle reflection/refraction. The results reveal that the crust of the eastern Dabie orogen presents a high-velocity dome, the velocity in the middle- and lower-crust′s metamorphic rocks exposed on the surface in the core of the dome approaches 5.0 km/s, the low velocity layers (body) with about 6.1 km/s has developed in upper-middle crust in it′s both sides wing, the Moho discontinuity relatively largely varies and ranges from ～ 41km in the core to 32～34 km in both sides, and a 4 km Moho-offset is observed beneath along Xiaotian-Muzitan Fault. We recognize that the eastern Dabie orogen shows a velocity-pattern of typical continent-continent deep subduction/collision style. The Moho offset may be related with the deep subductionof the Yangtze Block, and represents the suture zone between the Yangtze/Sino-Korean Block collision. Therefore, the high-velocity dome may occur by collision/extrusion between the both continental Blocks and the low velocity layers (body) mentioned above may play an important role in the post-collisional crust extension and exhumation of the ultra-high press metamorphic rocks.
引文
1)据袁学诚在国家自然科学基金委95重大项目“超高压变质作用与碰撞造山动力学”年度工作会议上的口头报告(2001年6月).
[1] 王清晨,孙枢,李继亮等.秦岭的大地构造演化.地质科学,1989,(2):129～142WANGQingchen,SUNShu,LIJiliang,etal.TectonicevolutionoftheQinlingmountains.ScientiaGeologicaSinica(inChinese),1989,(2):129～142
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[4] XuShutong,OkayAI,JiShouyuan,etal.DiamondsfromDabieShanmetamorphicrocksanditsimplicationfortectonicsetting.Science,1992,256:80～82
[5] CongB ,ZhaiM ,CarswellDA ,etal.Petrogenesisoftheultrahigh pressurerocksandtheircountryrocksatShuangheinDabieshan,centralChina.EuropeanJ.Mineralogy,1995,7:119～138
[6] Yekai,HirajimaT ,IshiwatariA ,etal.ThediscoveryofintergranularcoesiteineclogiteofYangkou,Qingdaoanditssignificance.ChineseScienceBulletin,1996,41(15):1407～1408
[7] 董树文,吴宣志,高锐等.大别造山带地壳速度结构与动力学.地球物理学报,1998,41(3):349～361DONGShuwen,WUXuanzhi,GAORui,etal.OnthecrustvelocitylevelsanddynamicsoftheDabieshanorogenicbelt.ChineseJ .Geophys.(inChinese),1998,41(3):349～361
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[9] 董树文,孙先如,张勇等.大别山碰撞造山带基本结构.科学通报,1993,38(6):542～545DONGShuwen,SUNXianru,ZHANGYong,etal.ThebasictectonicsofDabieshancollisionalorogen.ChineseScienceBulletin,1993,38(6):542～545
[10] 徐佩芬,刘福田,王清晨等.大别—苏鲁碰撞造山带的地震层析成像研究———岩石圈三维速度结构.地球物理学报,2000,43(3):377～385XUPeifen,LIUFutian,WANGQingchen,etal.SeismictomographybeneaththeDabieSulucollisionorogen──3Dvelocitystructuresoflithosphere.ChineseJ .Geophys.,2000,43(3):377～385
[11] LiS,XiaoY ,LiuD ,etal.CollisionoftheNorthChinaandYangtzeBlocksandformationofcoesite bearingeclogites:Timingandprocesses.Chem.Geol.,1993,109:89～111
[12] CongB ,WangQ ,ZhaiM ,etal.UHPmetamorphicrocksintheDabieSuLuregion,China:Theirformationandexhumation.IslandArc,1994,3:135～150
[13] XuPeifen,LiuFutian,WangQingchen,etal.Slab likehighvelocityanomalyintheuppermostmantlebeneaththeDabieSuluorogen.GeophysicalResearchLetters,2001,28(9):1847～1850
[14] SuoShutian,ZhongZengqiu,YouZhendong,etal.Post collisionalductileextensionaltectonicframeworkintheUHPandHPmetamorphicbeltsintheDabieSuluregion,China.ActaGeologicaSinica,2001,75(2):151～160
[15] ZhongZengqiu,SuoShutian,YouZhendong.Regional scaleextensionaltectonicpatternofultrahigh pressureandhigh pressuremetamorphicbeltsfromtheDabiemassif,China.InternationalGeologyReview,1999,41:1033～1041
[16] 王国灿,杨巍然.大别山核部罗田穹隆形成的构造及年代学证据.地球科学———中国地质大学学报,1996,21:524～528WANGGuocan,YANGWeiran.StructuralandchronologicalevidenceoftheLuotiandomeinthecoreoftheeasternDabiemoutains,centralChina.EarthScience—JournalofChinaUniversityofGeosciences,1996,21:524～528
[17] 李曙光,黄 方,李 晖.大别—苏鲁造山带碰撞后的岩石圈拆离.科学通报,2001,46(17):1487～1490LIShuguang,HuangFang,LIHui.Post collisionaldelaminationofthelithospherebeneathDabieSuluorogenicbelt.ChineseScienceBulletin,2001,46(17):1487～1490
[18] 桑隆康,王人镜,张泽明等.九资河—天堂寨地区燕山晚期花岗岩与大别造山带核部隆升.地质学报,2001,74(3):234～246SANGLongkang,WANGRenjing,ZHANGZeming,etal.LateYanshanianGranitesintheJiuziheTiantangzhaiareaandupliftofthecoreoftheDabieorgenicbelt.ActaGeologicalSinica,74(3):234～246
[19] CervenyV ,PsencikI.SEIS83 numericalmodelingofseismicwavefieldin2Dlaterallyvaryinglayeredstructuresbytheraymethod,In:EngdahlE .R .ed.,DocumentationofEarthquakeAlgorithm,WorldDataCenter(A)forSolidEarthGeophysics.Boulder,Colo,1984,Rep.SE 35,36～40
[20] SYe,JAnsorge,E .Kissling,etal.CrustalstructurebeneaththeeasternSwissAlpsderivedfromseismicrefractiondata.Tectonophysics,1995,242:199～221
[21] WenjinZhao,KDNelson
[1] 王清晨,孙枢,李继亮等.秦岭的大地构造演化.地质科学,1989,(2):129～142WANGQingchen,SUNShu,LIJiliang,etal.TectonicevolutionoftheQinlingmountains.ScientiaGeologicaSinica(inChinese),1989,(2):129～142
[2] OkayAI,SengerAMC ,SatnM .Tectonicsofanultrahigh pressuremetamorphicterrane:theDabieShanTongbaiShanorogen,China.Tectonics,1993,12(6):1320～1334
[3] WangXiaomin,LiuJG ,MaoHK .Coesite bearingeclogitefromDabieMountainsincentralChina.Geology,1989,17:1085～1088
[4] XuShutong,OkayAI,JiShouyuan,etal.DiamondsfromDabieShanmetamorphicrocksanditsimplicationfortectonicsetting.Science,1992,256:80～82
[5] CongB ,ZhaiM ,CarswellDA ,etal.Petrogenesisoftheultrahigh pressurerocksandtheircountryrocksatShuangheinDabieshan,centralChina.EuropeanJ.Mineralogy,1995,7:119～138
[6] Yekai,HirajimaT ,IshiwatariA ,etal.ThediscoveryofintergranularcoesiteineclogiteofYangkou,Qingdaoanditssignificance.ChineseScienceBulletin,1996,41(15):1407～1408
[7] 董树文,吴宣志,高锐等.大别造山带地壳速度结构与动力学.地球物理学报,1998,41(3):349～361DONGShuwen,WUXuanzhi,GAORui,etal.OnthecrustvelocitylevelsanddynamicsoftheDabieshanorogenicbelt.ChineseJ .Geophys.(inChinese),1998,41(3):349～361
[8] 王椿镛,张先康,陈步云等.大别造山带的地壳结构研究.中国科学(D辑),1997,27(3):221～226WANGChuenyong,ZHANGXiankang,CHENGBuyun,etal.ThestudyonthecrustalstructureofDabieorogenicbelt.ScienceinChina(SeriesD),1997,27(3):221～226
[9] 董树文,孙先如,张勇等.大别山碰撞造山带基本结构.科学通报,1993,38(6):542～545DONGShuwen,SUNXianru,ZHANGYong,etal.ThebasictectonicsofDabieshancollisionalorogen.ChineseScienceBulletin,1993,38(6):542～545
[10] 徐佩芬,刘福田,王清晨等.大别—苏鲁碰撞造山带的地震层析成像研究———岩石圈三维速度结构.地球物理学报,2000,43(3):377～385XUPeifen,LIUFutian,WANGQingchen,etal.SeismictomographybeneaththeDabieSulucollisionorogen──3Dvelocitystructuresoflithosphere.ChineseJ .Geophys.,2000,43(3):377～385
[11] LiS,XiaoY ,LiuD ,etal.CollisionoftheNorthChinaandYangtzeBlocksandformationofcoesite bearingeclogites:Timingandprocesses.Chem.Geol.,1993,109:89～111
[12] CongB ,WangQ ,ZhaiM ,etal.UHPmetamorphicrocksintheDabieSuLuregion,China:Theirformationandexhumation.IslandArc,1994,3:135～150
[13] XuPeifen,LiuFutian,WangQingchen,etal.Slab likehighvelocityanomalyintheuppermostmantlebeneaththeDabieSuluorogen.GeophysicalResearchLetters,2001,28(9):1847～1850
[14] SuoShutian,ZhongZengqiu,YouZhendong,etal.Post collisionalductileextensionaltectonicframeworkintheUHPandHPmetamorphicbeltsintheDabieSuluregion,China.ActaGeologicaSinica,2001,75(2):151～160
[15] ZhongZengqiu,SuoShutian,YouZhendong.Regional scaleextensionaltectonicpatternofultrahigh pressureandhigh pressuremetamorphicbeltsfromtheDabiemassif,China.InternationalGeologyReview,1999,41:1033～1041
[16] 王国灿,杨巍然.大别山核部罗田穹隆形成的构造及年代学证据.地球科学———中国地质大学学报,1996,21:524～528WANGGuocan,YANGWeiran.StructuralandchronologicalevidenceoftheLuotiandomeinthecoreoftheeasternDabiemoutains,centralChina.EarthScience—JournalofChinaUniversityofGeosciences,1996,21:524～528
[17] 李曙光,黄 方,李 晖.大别—苏鲁造山带碰撞后的岩石圈拆离.科学通报,2001,46(17):1487～1490LIShuguang,HuangFang,LIHui.Post collisionaldelaminationofthelithospherebeneathDabieSuluorogenicbelt.ChineseScienceBulletin,2001,46(17):1487～1490
[18] 桑隆康,王人镜,张泽明等.九资河—天堂寨地区燕山晚期花岗岩与大别造山带核部隆升.地质学报,2001,74(3):234～246SANGLongkang,WANGRenjing,ZHANGZeming,etal.LateYanshanianGranitesintheJiuziheTiantangzhaiareaandupliftofthecoreoftheDabieorgenicbelt.ActaGeologicalSinica,74(3):234～246
[19] CervenyV ,PsencikI.SEIS83 numericalmodelingofseismicwavefieldin2Dlaterallyvaryinglayeredstructuresbytheraymethod,In:EngdahlE .R .ed.,DocumentationofEarthquakeAlgorithm,WorldDataCenter(A)forSolidEarthGeophysics.Boulder,Colo,1984,Rep.SE 35,36～40
[20] SYe,JAnsorge,E .Kissling,etal.CrustalstructurebeneaththeeasternSwissAlpsderivedfromseismicrefractiondata.Tectonophysics,1995,242:199～221
[21] WenjinZhao,KDNelson
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