基于Theta法改进的均衡滤波器在位场边界识别中的应用——以庐枞矿集区为例

Application of the improved filter based on the Theta method to edge detection of potential field data:an example from the Luzong ore district

利用观测数据确定地质体的边界位置是位场数据解译中的一项重要工作,传统的边界识别滤波器通常不能均衡深、浅部的地质体边界,近些年相关研究开始致力于发展均衡边界滤波器.本文基于Theta图法定义了新的边界识别滤波器,详述了滤波器波数域及空间域的主要计算公式,通过模型验证,该滤波器显著压制了Theta图法对深部地质体边界的放大作用,较好地平衡了深部和浅部边界.通过与传统的边界识别滤波器对比,本文定义的滤波器能够清晰且更加收敛地圈定出地质体的水平边界位置.以长江中下游成矿带庐枞矿集区为例,开展了1∶5万重磁数据的处理分析,并结合物性资料进行了讨论,结果表明:重磁数据的检测结果精确刻画了郯庐断裂带的位置;庐枞盆地的磁力数据检测边界整体与盆地的地质边缘一致,明确了边界断裂在深部倾向盆地内部;识别出庐枞盆地外围一系列环形边界,这些边界封闭区域与最新勘探发现的深部岩体及铁铜矿化体相对应,对于指导区域深部找矿工作有着重要的意义.

Edge detection plays an important role has been widely used to image geologic boundaries geologic boundaries can be determined by tracing in interpretation of potential field data, which such as contacts and faults. The outlines of the the enhanced analytic signal. Many filters are employed to detect and enhance the edges. The horizontal and vertical derivatives are commonly used to enhance edge features, but they can only outline the edges of large-amplitude anomalies. In order to display large and small amplitude anomalies simultaneously, some balanced filters have been proposed. We define new filters based on the Theta map method, using second-order horizontal and vertical directional derivatives, and display large and small amplitude edges simultaneously. These methods were tested on synthetic gravity data, and compared with other traditional filters. The results show that the new filters can achieve better results and reveal more details. The method has been applied to gravity and magnetic data acquired in the Luzong ore district in the Middle and Lower Yangtze River Valley mineralization belt. Based on the analysis of relations between lithology, density and magnetic susceptibility, calculated results are analyzed. Analysis results on gravity and magnetic data accurately depict the location of the Tanlu fault zone. A boundary feature in the regional gravity to the north of the Yangtze River is interpreted to be part of the Yangtze River fault. The identified boundaries from the magnetic data are consistent with the margins of the Luzong basin, and indicate that the bounding structures are normal faults that dip toward the basin. Some circular or approximately circular closed boundaries occur around the periphery of the Luzong basin. Recent exploration results confirm that there are intrusions hidden beneath the enclosed area, where skarn with iron copper mineralization is present. The results of this study provide significant guidance for further exploration.