喜马拉雅“东构造结”地区的特异重力场与深部地壳结构
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摘要
跨越中、印、缅三国交界的喜马拉雅“东构造结”地区(92°E~97°E,26°N~30°N)有一半以上的面积尚没有重力测点,是重力数据空白区,故无法直接研究其重力场特征与深部地壳结构(构造).本文应用卫星重力异常资料作为近似空间重力异常,经计算给出的布格重力异常,其特征与该地区的地形高程呈很好的镜像相关.据此得到该区不同方位的3个地壳深部结构剖面.重力异常反演求得青藏高原地壳厚度>70 km;喜马拉雅造山带为55 km左右;布拉马普特拉河谷盆地为33~35 km;那加山山脉地区为40~45 km,即呈现出3个不同构造单元的展布.同时求得“东构造结”区由高密度的刚性物质构成,在印度洋板块的碰撞、挤压作用下呈向北运移,并插入青藏高原东缘.基于这样的构造格局和深层动力过程,导致了青藏高原东南缘和东北缘的强烈构造运动,大、小地震的频频发生和矿产资源的聚集.
More than a half of the 'Himalayas east structural knot' area(92°E～97°E,26°N～30°N) that straddles boundaries between China,India and Burma has no ground gravity measuring point yet.Here it is hard to research directly the gravity field characteristic and the deep crustal structure.In this paper,the satellite gravity anomaly data are employed as pseudo free air gravity anomaly to calculate Bouguer gravity anomaly.The calculated Bouguer gravity anomaly exhibits well mirror correlation with the topography altitude of this district.Three profiles of deep crustal structure according to above calculation are obtained.In the Qinghai-Xizang Plateau the crust thickness is more than 70 km,in the orogenic belt of Himalayan Mountains it is about 55 km,in the Brahmaputra basin valley it is 33 to 35 km,and in the Naga mountain it is 40 to 45 km.The 'east structural knot' is composed of high-density matter,moves northward after the collision and extrusion by the Indian Ocean plate,and then inserts into the eastern margin of the Qinghai-Xizang Plateau.This dynamic process results in violent tectonic movement of the southeastern and northeastern edges of the Qinghai-Xizang Plateau,induces a series of earthquakes frequently,and accumulates a large amount of mineral resources.
More than a half of the 'Himalayas east structural knot' area(92°E～97°E,26°N～30°N) that straddles boundaries between China,India and Burma has no ground gravity measuring point yet.Here it is hard to research directly the gravity field characteristic and the deep crustal structure.In this paper,the satellite gravity anomaly data are employed as pseudo free air gravity anomaly to calculate Bouguer gravity anomaly.The calculated Bouguer gravity anomaly exhibits well mirror correlation with the topography altitude of this district.Three profiles of deep crustal structure according to above calculation are obtained.In the Qinghai-Xizang Plateau the crust thickness is more than 70 km,in the orogenic belt of Himalayan Mountains it is about 55 km,in the Brahmaputra basin valley it is 33 to 35 km,and in the Naga mountain it is 40 to 45 km.The 'east structural knot' is composed of high-density matter,moves northward after the collision and extrusion by the Indian Ocean plate,and then inserts into the eastern margin of the Qinghai-Xizang Plateau.This dynamic process results in violent tectonic movement of the southeastern and northeastern edges of the Qinghai-Xizang Plateau,induces a series of earthquakes frequently,and accumulates a large amount of mineral resources.
引文
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[11]许厚泽,张赤军,蒋福珍等.青藏高原的大地测量学研究.湖北:湖北科学技术出版社,2001.37~44Xsu H Z,Zhang C J,Jiang F Z,et al.The Study of Geodesy inTibetan Plateau(in Chinese).Hubei:Hubei Science and TechnologyPress,2001.37~44
[12]周国藩,陈建国,张健.青藏高原卫星重力场及所反映的壳幔结构和深部构造特征.地球科学—中国地质大学学报,1996,21(2):191~197Zhou G F,Chen J G,Zhang J.Characters of crust_mantleconstruction and deep structure in Tibetan plateau.Earth Science_Journal of China University of Geosciences(in Chinese),1996,21(2):191~197
[13]王谦身,张赤军,安玉林等.重力学.北京:地震出版社,2003.33~36Wang Q S,Zhang C J,An Y L,et al.Gravity(in Chinese).Beijing:Seismological Press,2003.33~36
[14]王谦身,杨新社.分层重力图像方法及其应用.地球物理学报,1997,40(5):649~659Wang Q S,Yang X S.The method of stratified gravity images and itsapplication.Chinese J.Geophy.(Acta Geophysica Sinica)(inChinese),1997,40(5):649~659
[15]马杏垣主编.中国岩石圈动力学地图集.北京:中国地图出版社,1989.8~10Ma X Y eds.Lithospheric Dynamics Atlas of China(in Chinese).Beijing:China Cartographic Publishing House,1989.8~10
[16]Bowin C.Depth of principal mass anomalies contributing to theearth s geoidal undulations and gravity anomalies.Marine Geodesy,1983,7:61~100
[2]王二七,Barchfiel B C,季建清.喜马拉雅构造结区新生代地壳缩短量的估算及其地质依据.中国科学(D辑),2001,31(1):1~9Wang E Q,Barchfiel B C,Ji J Q.Estimation of Cenozoic crustshortening and its geological evidence in Himalayas structure knot.Science in China(Series D)(in Chinese),2001,31(1):1~9
[3]钟大赉,丁林.青藏高原隆起过程及其机制探讨.中国科学(D辑),1996,26(3):289~295Zhong D L,Ding L.The study of uplift process and its mechanism ofQinghai_Xizang Plateau.Science in China(Series D)(in Chinese),1996,26(3):289~295
[4]Bai D H,Maxwell Meju.Deep structure of the Longling_Ruili faultunderneath Kuili Basin near the eastern Himalayan Syntax insightfrom Magnetotelluric imaging.Tectonophysics,2003,364:131~146
[5]Holt W E,Ni J F,Wallace T C,et al.The active tectonics of theeastern Himalayan syntaxis and surrounding regions.J.Geophys.Res.,1991,96:14596~14632
[6]熊熊,滕吉文.青藏高原东缘地壳运动与深部过程的研究.地球物理学报,2002,45(4):507~515Xiong X,Teng J W.Study on crustal movement and deep progress inEastern Qinghai_Xizang Plateau.Chinese J.Geophys.(inChinese),2002,45(4):507~515
[7]王谦身,安玉林.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,2001,16(4):4~10Wang Q S,An Y L.Gravity field and deep structure of Madoi_Shamaregion in Eastern Qinghai_Xizang(Tibetan)Plateau.Progress inGeophysics(in Chinese),2001,16(4):4~10
[8]张健,石耀霖.青藏高原隆升及伸展变形中的重力位能.地球物理学报,2002,45(2):226~232Zhang J,Shi Y L.The role of gravitational potential energy in raisingand spreading of Qinghai_Xizang Plateau.Chinese J.Geophys.(inChinese),2002,45(2):226~232
[9]胡家富,朱雄关,夏静瑜等.利用面波和接收函数联合反演滇西地区壳幔速度结构.地球物理学报,2005,48(5):1069~1076Hu J F,Zhu X G,Xia J Y,et al.Using surface wave and receiverfunction to jointly inverse the crust_mantle velocity structure in theWest Yunnan area.Chinese J.Geophys.(in Chinese),2005,48(5):1069~1076
[10]汤懋苍,钟大赉,李少华等.雅鲁藏布江“大峡弯”是地球“热点”的证据.中国科学(D辑),1998,28(5):463~468Tang M C,Zhong D L,Li S H,et al.Evidence for the Daxiawan asa hot spot in the Earth.Science in China(Series D)(in Chinese),1998,28(5):463~468
[11]许厚泽,张赤军,蒋福珍等.青藏高原的大地测量学研究.湖北:湖北科学技术出版社,2001.37~44Xsu H Z,Zhang C J,Jiang F Z,et al.The Study of Geodesy inTibetan Plateau(in Chinese).Hubei:Hubei Science and TechnologyPress,2001.37~44
[12]周国藩,陈建国,张健.青藏高原卫星重力场及所反映的壳幔结构和深部构造特征.地球科学—中国地质大学学报,1996,21(2):191~197Zhou G F,Chen J G,Zhang J.Characters of crust_mantleconstruction and deep structure in Tibetan plateau.Earth Science_Journal of China University of Geosciences(in Chinese),1996,21(2):191~197
[13]王谦身,张赤军,安玉林等.重力学.北京:地震出版社,2003.33~36Wang Q S,Zhang C J,An Y L,et al.Gravity(in Chinese).Beijing:Seismological Press,2003.33~36
[14]王谦身,杨新社.分层重力图像方法及其应用.地球物理学报,1997,40(5):649~659Wang Q S,Yang X S.The method of stratified gravity images and itsapplication.Chinese J.Geophy.(Acta Geophysica Sinica)(inChinese),1997,40(5):649~659
[15]马杏垣主编.中国岩石圈动力学地图集.北京:中国地图出版社,1989.8~10Ma X Y eds.Lithospheric Dynamics Atlas of China(in Chinese).Beijing:China Cartographic Publishing House,1989.8~10
[16]Bowin C.Depth of principal mass anomalies contributing to theearth s geoidal undulations and gravity anomalies.Marine Geodesy,1983,7:61~100
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