LI Ying-kang, GAO Rui, YAO Yu-tao, MI Sheng-xin, LI Wen-hui, XIONG Xiao-song, GAO Jian-wei. The crust velocity structure of Da Hinggan Ling orgenic belt and the basins on both sides. Progress in Geophysics, 2014, 29(1): 73-83, doi: 10.6038/pg20140110
The crust velocity structure of Da Hinggan Ling orgenic belt and the basins on both sides
LI Ying-kang1, GAO Rui2, YAO Yu-tao1, MI Sheng-xin1, LI Wen-hui2, XIONG Xiao-song2, GAO Jian-wei1
1. Geological Information Centre, Ministry of Land and Resource, Sanhe 065201, China; 2. Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China
Abstract: Xinbaerhu-Qiqihaer Deep Seismic Sounding profile is about 630 km long, which goes across Hailaer basin, Da Hinggan Ling orgenic belt and Songliao basin. According to travel-time data of 5 seismic phases and the amplitude information which were recognized by the recorded sections in 9 shots, the authors obtained the two-dimensional P waves velocity structure along the profile, the thickness of crust is about 39.0～41.0 km in Hailaer basin, the thickness of crust from 38.5～43.5 km in the west to 34.5～36.4 km in the east of Da Hinggan Ling orgenic belt, the thickness of crust is about 32.4～36.2 km in Songliao basin, analyzed the difference structure of crust and upper mantle of Da Hinggan Ling orgenic belt and the basins on both side, to discuss the relation of basin-mountain structure.
Key words:
da Hinggan Lingdeep seismic soundingstructure of crust and upper mantle
图 1大兴安岭及两侧盆地地质简图
(据邵济安，2005，略改)
Fig.1eological sketch map of Daxinganling orgenic
belt and the basins on both side(Modified
from Shao Jian et al. ,2005)
阿尔山火山群位于中蒙边界东段的大兴安岭重力梯度带上，属于西太平洋俯冲板块弧后边缘区(国家地震局，1989)，因受太平洋俯冲板块的俯冲和欧亚板块的阻挡，发育一系列北东向的断裂，自新生代以来，曾发生过多次强烈的玄武岩喷发(朱勤文等，1997)，是大兴安岭地区重要的火山群之一.汤吉等(2005)阿尔山活火山区进行大地电磁测深点观测，研究表明新、老两条火山喷发带存在通往深部的岩浆通道，其中新的活火山带在地下10~12 km还保持着较高的热状态，很可能富含流体，在30~50 km处可能是地慢向上的供热通道，而老火山带30 km以上可能存在一个正在冷却的岩浆通道，两条火山条带在深部可能是同源的.对于中国东北地区的火山形成机制，Miyashiro(1986)提出在上地幔存在一个不同于热点的热区，热区自澳大利亚一直运移到我国的东北地区，造成我国东北的火山.Iwamori(1992)提出的湿区形成机制认为，在俯冲板块的岛弧和弧后区的火山活动是由于非亏损的地幔上涌引起的，地幔上涌积累了挥发性物质，它引起固相线温度的降低，这时称为“湿区”，刘若新等从岩石学角度研究的结果(刘若新等，1998)认为，太平洋板片消减到我国东北时的深度达600 km 左右，板块运动使上地幔的岩浆向上运移，在上地幔顶部和地壳内分别生成地幔岩浆房和地壳岩浆房.吴福元等(2000)提出太平洋俯冲板片在我国东北600 km 处折曲脱“水”，上涌至上地幔，造成地幔流体聚集而形成岩浆房.马莉和刘德来(1999)提出软流圈单向环流模式等.
天然地震层析成像结果提供了华北克拉通及相关区域上地幔结构的一些基本特征，华北克拉通东部上下地幔过渡带为高速体，在高速体上、下存在一些低速异常体(朱日祥和郑天愉，2009；朱日祥等，2011).华北克拉通东部下方的地幔过渡带结构保存了太平洋板块俯冲物质在过渡带停滞的特性.华北克拉通中部上地幔的低速结构以及横波分裂观测结果表明，存在局部不均匀的地幔对流状态.华北克拉通东部上地幔在晚中生代的流动主要是受太平洋板块俯冲导致的大地幔楔的影响(Zhao et al.，2007).华北克拉通西部的高速体表明, 厚的古老岩石圈根没有被破坏，并给出了太平洋板块的俯冲模型与地幔对流机制(朱日祥等，2011).总之，这些地球物理的结果展示了大兴安岭及邻区的地壳、上地幔结构的概貌, 提供了窥视深部构造特征的图像.
表3 各炮P2震相的追踪距离(km)、平均速度(km/s)和振幅能量
Table 3 The tracking distance and average speed, the amplitude of energy of P2-waves seismic phases of every shot point
炮点
S1
S2
S3
S4
S5
S6
S7
S8
S10
P2
左支
40~80
30~100
45~130
50~100
50~130
60~120
40~100
50~140
50~140
5.73
5.96
5.98
6.0
6.02
6.0
5.98
6.01
5.90
右支
40~120
35~120
35~100
40~140
50~110
50~120
50~140
40~120
70~110
5.8
6.0
6.0
6.0
5.98
5.98
6.0
5.98
5.87
各炮振 幅能量
在60至100 km，初至清晰，能量较强.
在60至110 km，初至清晰，能量较强.
在60至120 km，初至清晰，能量较强.
在60至120 km，初至可见，能量不是很强.
在60至120 km，初至可见，能量较强.
在60至110 km，初至清晰，左支能量强，右支能量较弱.
在80至120 km，初至清晰，能量较强.
在60至90 km，初至清晰，能量最强.
在70至110 km，初至清晰，能量最强.
表3 各炮P2震相的追踪距离(km)、平均速度(km/s)和振幅能量
Table 3The tracking distance and average speed, the amplitude of energy of P2-waves seismic phases of every shot point
表4 各炮P3震相的追踪距离(km)、平均速度(km/s)和振幅能量
Table 4 The tracking distance and average speed, the amplitude of energy of P3-waves seismic phases of every shot point
炮点
S1
S2
S3
S4
S5
S6
S7
S8
S10
P3
左支
60~80
60~120
70~170
70~170
80~170
80~180
70~180
70~200
70~180
6.07
6.16
6.22
6.23
6.21
6.22
6.25
6.26
6.14
右支
50~170
60~160
80~190
80~165
80~170
80~190
85~190
80~150
50~90
6.15
6.24
6.21
6.24
6.23
6.24
6.25
6.23
5.98
各炮振 幅
能量
在120至160 km变为初至波，能量较强.
在100至140 km初至明显，右支能量较强，左支能量较弱.
在100至170 km能量较强，尾部初至明显.
在90至140 km能量较强，初至清晰，尾部能量较弱.
在80至120 km能量较强，后部能看相对较弱，初至不够清晰.
左支在100至160 km能量较强，右支能量较弱.
在130至150 km能量稍强，尾部初至不明显.
在80至140 km能量较强.
在110至150 km能量较强.
表4各炮P3震相的追踪距离(km)、平均速度(km/s)和振幅能量
Table 4The tracking distance and average speed, the amplitude of energy of P3-waves seismic phases of every shot point
表5 各炮Pm震相的追踪距离(km)、地壳平均速度(km/s)和地幔顶部速度
Table 5 Track distance, average speed of the crust and uppermost mantle velocity of Pm-waves seismic phases of every shot point
炮点
S1
S2
S3
S4
S5
S6
S7
S8
S10
P3
左支
100~160
85~175
80~170
80~215
100~240
95~240
90~300
90~280
6.35
6.38
6.35
6.35
6.42
6.41
6.38
6.39
右支
90~290
90~210
100~190
80~260
80~260
100~250
100~200
95~150
70~80
6.36
6.41
6.41
6.40
6.39
6.38
6.41
6.42
6.29
各炮振 幅能量
在120至220 km能量很强.在追踪范围的两侧震相清楚.
整体能量很强.在追踪距离170至210 km初至清晰.
在追踪距离170至210 km初至清晰，能量很强，干扰较大.
在追踪距离110至160 km和230至260 km能量很强，初至清晰.
在追踪距离100至160 km，右支170至240 km能量很强，初至清晰.
在追踪距离120至180 km，右支170至240 km能量很强，初至清晰.
在追踪距离120至190 km能量很强，初至清晰.
在追踪距离120至190 km能量很强，初至清晰.
在追踪距离160至220 km，能量很强，初至清晰.
Pn
距离
185~290
220~300
190~320
速度
7.85~7.9
8.0~8.1
7.91~8.0
振幅能量
在250 km 能量最强.
在240 km 能量最强.
在290至 300 km 能量最强.
表5各炮Pm震相的追踪距离(km)、地壳平均速度(km/s)和地幔顶部速度
Table 5Track distance, average speed of the crust and uppermost mantle velocity of Pm-waves seismic phases of every shot point
大兴安岭造山带及两侧盆地二维速度结构是在震相识别的基础上建立的,并以测线通过地形最高点的高程1360 m为模型零点，构制了剖面的初始二维地壳模型.正演拟合计算采用基于地震波的渐近射线理论方法(Cerveny et al，1977，1982，1984)，对各炮拾取的到时进行拟合, 通过不断修改反射界面深度和层速度，逐步改进初始二维速度结构.并在同一二维速度结构模型中，逐步完成9炮、每炮4个震相的地震波到时拟合，达到满意的程度，限制模型的多解性(图6.1～图6.3).图6.1～图6.3中的三角表示拾取的震相到时，方框表示理论计算的震相到时.
图 6-1
Fig.6-1
图 6-1S8 S5 S1 炮地震记录波型图、走时拟合图和射线追踪图
Fig.6-1 Seismic phases, travel time fitting and ray tracing diagram of S1 shot
图 6-2
Fig.6-2
图 6-2S8 S5 炮地震记录波型图、走时拟合图和射线追踪图
Fig.6-2 Seismic phases, travel time fitting and ray tracing diagram of S5 shot
图 6-3
Fig.6-3
图 6-3S8 炮地震记录波型图、走时拟合图和射线追踪图
Fig.6-3Seismic phases, travel time fitting and ray tracing diagram of S8 shot
大兴安岭西部的伊尔施镇至天池镇一带，即大兴安岭重力梯级带和阿尔山火山群的位置，属于西太平洋俯冲板块弧后边缘区(国家地震局，1989)，下地壳存在一个明显的高速度区，最高速度达到7.0～7.1 km/s.认为是火山喷发的岩浆通道或岩浆囊，形成了高速、高密度体(邵济安等，2000；汤吉等，2005).因受太平洋俯冲板块的俯冲和欧亚板块的阻挡，发育一系列北东向的断裂，自新生代以来，曾发生过多次强烈的玄武岩喷发(Liu et al.，2001)，地表被玄武岩覆盖，是大兴安岭地区重要的火山群之一(图3).
嫩江断裂(F2)在深部的延伸方向与满洲里—绥芬河地学断面的结果(金旭和杨宝俊，1994)一致.虽然，大地电磁研究在松辽盆地西部的结果中，证明上地壳存在向东逆冲构造.但本文在松辽盆地与大兴安岭之间的地壳结构中，未发现“鳄鱼结构”式构造(Meissner et al.，1991；王椿镛等，2003).而从地壳中的界面形态看，特别是莫霍面的形态，大兴安岭与海拉尔盆地之间，可能存在“鳄鱼结构”式构造(图8)，逆冲断裂的作用使大兴安岭叠置于两侧的盆地之上.
图 8
Fig.8
图 8根据二维地壳速度结构推断的动力学模型
Fig.8Dynamics model concluded by the two-dimensional crustal velocity structure
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2014, Vol. 29
