地球物理学进展 ›› 2014, Vol. 29 ›› Issue (6): 2620-2627.doi: 10.6038/pg20140623

• 固体地球物理学 • 上一篇    下一篇

三江盆地重磁场特征与深部结构

周稳生, 董平, 王良书, 孙斌   

  1. 南京大学地球科学与工程学院, 南京 210046
  • 收稿日期:2013-12-12 修回日期:2014-03-17 出版日期:2014-12-20 发布日期:2014-12-20
  • 通讯作者: 董平, 男, 博士, 副教授, 1963年生, 江苏南京人, 主要从事应用地球物理研究.(E-mail:dongping@ndjc.com). E-mail:dongping@ndjc.com
  • 作者简介:周稳生, 男, 1989年生, 江苏徐州人, 硕士研究生, 从事地球物理重磁研究.(E-mail:zhouwensheng9@163.com).
  • 基金资助:

    国家科技重大专项(2009ZX05009-001)和国家自然科学基金(41074084)联合资助.

Gravity and magnetic anomalies and deep structure in the Sanjiang Basin

ZHOU Wen-sheng, DONG Ping, WANG Liang-shu, SUN Bin   

  1. School of Earth Sciences and Engineering, Nanjing University, Nanjing 210046, China
  • Received:2013-12-12 Revised:2014-03-17 Online:2014-12-20 Published:2014-12-20

摘要:

三江盆地位于古亚洲洋域和滨太平洋域的叠加区域,是东北盆地群的典型盆地之一.研究三江盆地的深部结构,包括基底、地壳密度、莫霍面和居里面等,有利于解决盆地群地球动力学等基础性问题.本文在研究布格重力异常和航磁异常数据基础上,结合其他地质资料,利用小波多尺度分解对三江盆地重磁场进行四阶分离,结合对数功率谱确定1-4阶细节异常的视深度,提取盆地深部界面信息.以盆地重磁异常的2-3阶细节异常之和进行水平方向一阶导数计算,以此强化不同方向上的基底断层的线性表现,并据此划分出5条深断裂.根据重力异常四阶逼近,利用Parker 法反演了研究区的莫霍面深度,研究表明,研究区莫霍面深度介于29.5~30.5 km之间,总体上西北高,东南低.以航磁异常的4阶逼近反演了研究区居里面深度,其总体上是北低南高,深度介于21~24 km之间.

Abstract:

The Sangjiang Basin is one of the typical basin among the NE China Basin Groups,which is situated in the northeast of NE china. The analysis of the basin's deep tectonics, including the basement,crustal density, Moho and Curie, will be conducive to the solution of fundamental promblems in geodynamics.This research is based on Bouguer gravity and aeromagnetic anomalies data, combined with other geology data.The gravity and magnetic methods are commonly used in basin structural research which have better horizontal resolution than seismic profiling exploring. Forward and inversion modeling approaches, such as Wavelet Multiscale Decomposition, Logarithmic Power Spectrum Analysis, Horizontal derivative method and Parker method, are utilized in this research. Gravity and magnetic anomalies of the Sanjiang Basin mainly strike NNE and NE, followed by WE, which indicates that the pre-existing WE Paleo-Asian Ocean tectonics domain superposed and modified by the NE Pacific domain.Zoning characteristics of gravity and magnetic fields prove a significant mosaic tectonic background of the study area.Gravity and magnetic fields of Sanjiang Basin are separated with Wavelet Multi-scale Decomposition of order 4. The apparent depths of causative sources were then assessed by Power Spectrum Analysis of each order.Low-order wavelet detail anomalies were used to study the basin's basement structure such as major faults, the basement lithology, uplifts and depressions. High-order ones were used for the inversion of Moho and Curie discontinuities using the Parker method.To extract linear basement faults, the first derivative of the Summation of details of order 2-3 wavelet gravity and magnetic is calculated. Finally, 5 major basement faults are identified in the study area and their occurrence characters are established after the gravity gradient belt characteristics are enhanced.The 4th order gravity magnetic approximation anomalies after Wavelet Multiscale Decomposition may reflect the 3D shape of the Moho and Curie in the Sanjiang Basin. Based on order 4 approximation of gravity anomalies, the Moho depth of the study area is inversed using Parker method. The depth of the study area ranges from 29.5 km to 30.5 km with high value in the northwest and low value in the southeast,that of the northwestis deep while that of the southeast is shallow.Based on order 4 approximation of magnetic anomalies, the Curia depth of the study area is also inversed using Parker method. The Curia depth of the study area ranges from 21 km to 24 km with high value in the north and low value in the south.

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