青藏高原中部北北东向深部负磁异常带的成因及其意义
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摘要
根据最新测量获得的青藏高原中西部航磁异常图 ,经不同高度向上延拓后 ,发现在测区东部 ,即青藏高原中部自柴达木向西南延伸的广大地区 ,出现一条极为明显的北北东向负磁异常带。从对航磁区域场的分析 ,并结合人工地震、重力计算莫霍面深度、热水活动、最新火山岩活动、地貌特征和天然地震活动等多种资料的解释 ,认为负异常带是由于深部热流沿北北东向上升引起局部岩浆熔融 ,使上地壳下部具有较高的地温 ,导致磁性层底部消磁作用的结果。与此同时也加快了青藏高原隆升的幅度 ,为高原形成和演化的研究提供了新的证据
The different altitudes upward continuation of the recently surveyed aeromagnetic anomalies in central and western Qinghai Tibet plateau revealed an extremely distinct NNE trending negative magnetic anomaly zone in the eastern part of the surveyed area, i.e., in the vast area extending from Qaidam southwestward within central Qinghai Tibet plateau. According to an analysis of the aeromagnetic regional field in combination with man made earthquake, Moho depth calculated by gravity, hydrothermal activity, recent volcanic activity, morphologic characteristics and natural seismic activity, it is held that the upward migration of deep heat flow in NNE direction caused local melting of magma and hence the rising of geotemperature in the lower part of the upper crust, which led to the demagnetization at the bottom of the magnetic bed, the appearance of negative magnetic anomalies, and the acceleration of the uplifting of Qinghai Tibet plateau. All this has provided new evidence for the study of the formation and evolution of the plateau.
The different altitudes upward continuation of the recently surveyed aeromagnetic anomalies in central and western Qinghai Tibet plateau revealed an extremely distinct NNE trending negative magnetic anomaly zone in the eastern part of the surveyed area, i.e., in the vast area extending from Qaidam southwestward within central Qinghai Tibet plateau. According to an analysis of the aeromagnetic regional field in combination with man made earthquake, Moho depth calculated by gravity, hydrothermal activity, recent volcanic activity, morphologic characteristics and natural seismic activity, it is held that the upward migration of deep heat flow in NNE direction caused local melting of magma and hence the rising of geotemperature in the lower part of the upper crust, which led to the demagnetization at the bottom of the magnetic bed, the appearance of negative magnetic anomalies, and the acceleration of the uplifting of Qinghai Tibet plateau. All this has provided new evidence for the study of the formation and evolution of the plateau.
引文
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[2] 孙鸿烈,潘裕生,孔祥儒,等青藏高原岩石圈结构演化和动力学[M]广州:广东科学技术出版社,1999.
[3] 青海省地矿局青海省区域地质志[M ]地质出版社,1991.
[4] HackerBR ,GnosE ,RatschbacherL ,etal.HotanddrydeepcrustalxenolithsfromTibet[J].Science,2000,287:2463-2466.
[5] 钱辉,姜枚,宿和平,等中国天然地震探测深部构造的研究现状与发展[J].物探与化探,2000,24(1):1-6
[6] 孟令顺,齐立,高锐,等青藏高原北缘重力场研究[J].物探与化探,1998,22(3):183-190
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