广东大湾—港口地震剖面的地质新意义
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摘要
以花岗岩原地重熔理论为依据重新解释了广东大湾—港口地震剖面。大湾—港口地震剖面可具体细分为上地幔层(Vp>8.05 km/s)、下地壳层(Vp=6.6-6.8 km/s)、中上地壳的壳内低速层(Vp=5.8 km/s)、基底层(Vp=5.9-6.3 km/s)以及沉积盖层(Vp<5.9 km/s);壳内多次重熔形成多层花岗岩,重熔层上方原始岩石物质组成的差异导致熔融后产生的重熔花岗岩层在横向上由不均一的物质组成,从而使得8 km深度以上的地震界面波动起伏,而在约8 km深度之下,波速界面起伏平缓或近于水平,表明在此深度之下的岩石物质组成在横向上相对均一:壳内重熔过程导致物质成分垂向深度变化是壳内地震波速自上而下增高的原因;壳内低速层的存在表明本区上陆壳重熔层的底部到目前尚未完全固化。地震界面起伏的特点与根据地表地质资料勾画的重熔界面波动形态有极好的吻合性,显示地震资料能够准确地揭示重熔界面位置和形态。
The seismic profile between Dawan and Cangkou in Guangdong is reinterpreted based on the theory of in-situ melting on granite genesis.The results show that the seismic profile can be divided into five layers,the mantle with V_p>8.05km/s,lower crust with V_p=6.6-6.8km/s,a mid-upper crustal lower velocity zone with V_p=5.8km/s,the basement layer with V_p=5.9-6.3km/s and sedimentary cover with V_p<5.9km/s.Multiple crustal remelting formed the multiple granite layers.The difference in substance above the melting interface is the reason of fluctuation of the velocity interfaces above 8km.However,they tend to flat with the reason that the rocks show homogenous below 8km.The seismic velocity increases with the variety of the substance in the depths of the crust caused by the crustal remelting and the low velocity zone below the basement layer to represent the youngest cooling magma layer.The research also displays that fluctuation of the velocity interfaces in the shallow part of the seismic profile is considered to mirror the irregular shapes of the melting interface' s.
The seismic profile between Dawan and Cangkou in Guangdong is reinterpreted based on the theory of in-situ melting on granite genesis.The results show that the seismic profile can be divided into five layers,the mantle with V_p>8.05km/s,lower crust with V_p=6.6-6.8km/s,a mid-upper crustal lower velocity zone with V_p=5.8km/s,the basement layer with V_p=5.9-6.3km/s and sedimentary cover with V_p<5.9km/s.Multiple crustal remelting formed the multiple granite layers.The difference in substance above the melting interface is the reason of fluctuation of the velocity interfaces above 8km.However,they tend to flat with the reason that the rocks show homogenous below 8km.The seismic velocity increases with the variety of the substance in the depths of the crust caused by the crustal remelting and the low velocity zone below the basement layer to represent the youngest cooling magma layer.The research also displays that fluctuation of the velocity interfaces in the shallow part of the seismic profile is considered to mirror the irregular shapes of the melting interface' s.
引文
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[13]Chen G N,Grapes R,Zhang K.A model for Mesozoic crustal melting and tectonic deformation in SE China. International Geology Review,2003,45:948-957
[14]马浩明,陈国能,彭卓伦,等.广东上磜复式花岗岩体地质特征及形成机制[J].中山大学学报(自然科学版),2006,45(2):105-108.
[15]邱燕.华南大陆边缘新生代构造地貌演化机制研究[D].广州:中山大学,2006.
[2]徐树桐,袁学诚,吴维平,等.大别山黄石—六安反射地震剖面新的地质解释[J].地质通报,2008,27 (1):19-26.
[3]陈国能.大陆地质学研究的若干问题思考[J].高校地质学报,1997,3(3):342-347.
[4]陈国能,曹建劲,张珂.原地重熔与元素地球化学场—论花岗岩的成因与成矿及大陆内部的物质旋回[M].北京:地质出版社,1996.
[5]Chen G N,Grapes R.Granite Genesis:In-Situ Melting and Crustal Evolution.Netherlands:Springer,2007
[6]尹周勋,赖明惠,熊绍柏,等.华南连县—博罗—港口地带地壳结构及速度分布的爆炸地震探测结果[J].地球物理学报,1999,42(3):383-392.
[7]黄镇国,张伟强,钟新基,等.台湾板块构造与环境演变[M].北京:海洋出版社,1995.
[8]高山,骆庭川,张本仁,等.中国东部地壳的结构和组成[J].中国科学(D辑),1999,29(3):205-213.
[9]王光杰,腾吉文,张中杰,等.中国华南大陆及陆缘地带的大地构造基本格局[J].地球物理学进展, 2000,15(3):25-41.
[10]杨晓松,金振民.部分熔融与青藏高原地壳加厚的关系综述[J].地质科技情报,1999,18(1):24-28.
[11]Schmitz M,Heinsohn W D,Schilling F R.Seismic,gravity and petrological evidence for partial melt beneath the thickened Central Andean crust(21-23○),Tectonophysics,1997,270:313-326.
[12]Chen G N,Grapes R.In-situ melting model of granite formation evidence from SE China.International Geology Review,2003,45:611-622.
[13]Chen G N,Grapes R,Zhang K.A model for Mesozoic crustal melting and tectonic deformation in SE China. International Geology Review,2003,45:948-957
[14]马浩明,陈国能,彭卓伦,等.广东上磜复式花岗岩体地质特征及形成机制[J].中山大学学报(自然科学版),2006,45(2):105-108.
[15]邱燕.华南大陆边缘新生代构造地貌演化机制研究[D].广州:中山大学,2006.
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