航磁全轴梯度异常特征研究

因提供多参量、压制深部异常突出浅部异常等优点,近几年航磁梯度测量在国内航空物探领域成为新的研究热点.以AGS-863航磁全轴梯度勘查系统为依托,介绍了航磁梯度理论基础和应用研究现状,为了总结归纳航磁梯度异常与地下地质体的对应关系,设计了典型理论地磁模型,进行了大量正演模拟计算工作,并结合野外应用实例,得出以下几点结论:相比于总场异常,梯度异常在圈定磁性体方面更具优势;对于独立磁性体,垂向梯度的峰值精确对应异常体的中心位置,当模型走向延伸越长,主剖面异常的零值点越靠近异常体边界,主剖面的纵向梯度的最大值和最小值可精确对应异常体的左右边界,垂直于主剖面的横向梯度的最大值和最小值精确对应异常的上下边界;对于组合磁性体,利用主剖面的纵向梯度峰值和垂直于主剖面的横向梯度峰值锁定的磁性体范围有所扩大,并且垂向梯度峰值向附近磁性体方向偏移;对比实测梯度数据与理论梯度数据,发现实测梯度数据存在明显的优势,可以在人文干扰识别、高频地质信息挖掘等方面发挥突出作用.这些工作可以为实测航磁梯度的野外数据获取者认识异常、鉴别异常和区分真假异常等提供参考,并为异常解释工作者提供一定的帮助.

Study on characteristics of three axis airborne magnetic gradient anomaly

Because of the advantages of multi-parameter and the suppression of the shallow anomaly,the measurement of airborne mag-netic gradient has become a new research hotspot in the field of airborne geophysical exploration in recent years. Based on AGS-863 three axis airborne magnetic gradiometer,it described the aeromagnetic gradient theory and the application research status. In order to summarize the relationship between aeromagnetic anomaly and the underground geological bodies,it designed some typical geomagnetic models,took a large number of forward simulation work, and drew the following conclusions: compared with the total field anomaly, gradient anomaly had more advantageous in the delineation of the magnetic bodies;for single magnetic body,the vertical gradient peak corresponded precisely to the center position of the magnetic body,and the longer of strike length of the magnetic body, the closer of the zero point of the main section to the abnormal body boundary,and the main section longitudinal gradient's maximum and minimum values exactly corresponded to abnormal body's left and right boundary and the main section's perpendicular section transverse gradient's minimum and maximum values exactly corresponded to abnormal body's up and down boundary;for the combined magnetic bodies,the range of the magnetic body which was locked with the main section longitudinal gradient peak and the main section's perpendicular sec-tion transverse gradient was enlarged,and the vertical gradient peak was shifted to the direction of the nearby magnetic body. By com-paring the measured gradient data with the theoretical gradient data,it found that the measured gradient data has obvious advantages, and it can play a prominent role in the identification of human interference and high frequency geological information. These work could provide reference for the field data acquisition workers to understand and identify anomaly and distinguish between true and false anom-aly,and provide some help for the anomaly interpretation workers.