Search for replacement resources of Meishan iron mine based on potential field separation methods
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摘要: 在重力勘探中，重力异常分离的目的是消除干扰，有针对性地突出目标异常.为探讨各种分离方法的理论基础及使用效果，应用位场分离方法对理论模型产生的重力场进行分离并做误差分析.试验结果表明：趋势分析法和解析延拓法获得的区域异常场重力等值线呈长轴为南北向的椭圆状特征，局部异常在南北向呈"两低夹一高"的特征，与理论模型布格重力异常图有差别.经剖面线形态比较和误差分析，二阶趋势分析、向上延拓225 m分离出的局部场高值区基本与理论模型相符.插值切割法和匹配滤波法获得的异常场重力等值线仍呈同心圆状，与模型重力等值线形态吻合.当切割半径为4 m、切割2次时，其剖面线整体拟合效果好于解析延拓法，但中心点附近的曲线拟合效果较差，且切割次数增大时，易产生震荡效应.匹配滤波法的关键在于合理地选取功率谱曲线的中高、低频段，通过适宜的滤波器滤波以提取不同波数成分的异常场.为寻找梅山铁矿接替资源，对该区重力异常进行分离.实践表明：二阶趋势分析、向上延拓700 m、切割半径10 m切割一次、匹配滤波法的分离结果具有较好的一致性：萝卜山-刘家村带、梅山村南部、黄林库-吴家洼带、主矿区深部及东南部存在幅值较高的剩余重力异常，揭示了铁矿资源分布的一般特征，为寻找梅山铁矿接替资源指明了方向.Abstract: In gravity exploration, the aim of gravity anomaly separation is to eliminate the interference and to target the abnormal. In order to explore the theoretical basis and the use effect of various methods of separation, the gravity field generated by the field separation method is used to separate the gravity field and make the error analysis.To investigate the application effect of various separation method, a theoretical model was established that the rectangular are upright and overlay, which was separated by trend analysis, analytical continuation, interpolating cut method and matched filter, error analysis and separation comparison was done by selecting a center line of the model. The results showed that:The gravity contours of separated regional field were oval shape which the long axis was north-south by trend analysis and analytical continuation, the feature of local anomaly is "two low and one high clip", but they differed from the anomaly map of theoretical model. The high value area of the local field were basically separated when 2 order trend analysis and upward contuniation 225 m.The gravity contours of separated regional field were also concentrically, fitting the shape of model. The overall fitting effect of theory field by interpolating cut method was better than analytical continuation when 4 m cutting radius and 2-time iteration, but the fitting effect was poor near the center of the model. And it was easy to produce shock effect when the number was increasing. It was important to analysis the power spectrum of observed gravity, choosing suitable wave bands and building low-pass and band-pass filter,matched filtering can extract different wave anomaly fields. For searching alternative resources of the Meishan iron mine,its gravity anomaly was separated. The results showed that when the order of trend analysis was 2, the distance of upward continuation was 700 meters, the cutting radius was 10 meters and the cutting times was 1, using matched filter, there were residual and higher magnitude gravity anomalies existing at the Radish Hill-Liu village, the south of Meishan village, Huanglin Library-Wujia Wa, deep and southeast of the main mining area, it revealed general characteristics of the distribution of iron ore resources, and they pointed out the direction of looking for alternative resources.
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