小波多尺度分析与磁异常分离实践--以朱冲铁矿为例

A PRACTICE IN WAVELET MULTI-SCALE ANALYSIS AND MAGNETIC ANOMALY SEPARATION—AN EXAMPLE FROM THE ZHUCHONG IRON ORE DEPOSIT

小波多尺度分析是重磁异常分离的一个重要方法,它不同于如窗口滑动平均法、趋势分析法、匹配滤波等常用方法,因这些方法分离出的局部异常是地质体从某个深度往上直到地表的综合反应,由于近地表地质体及干扰源的作用使得被分离出的局部异常成分复杂、形态较为凌乱、不规整;而用小波多尺度分析分解出的N(N>1)阶细节异常划分的局部异常则为地质体从深度A往上到深度B这一空间段的综合反应,由于其不包含以一阶细节异常为代表的浅层地质体及干扰源异常,异常成分简单、形态规整、为深部地质体的自然反应,适用于研究隐伏岩体与隐伏矿床。通过二次开发解释20世纪80年代采集的月山地区1∶1万地面磁测数据,并最终提交由小波多尺度分析法分解的局部异常成果,其中3个异常与朱冲铁矿的3个矿段相吻合,而这些局部异常却是在未知朱冲铁矿的前提下提取的,可预见其它几个有类似地质条件的局部异常也具找矿前景。

Wavelet multi-scale analysis is a major method for gravitational and magnetic anomaly separation, different from usual methods of window moving average, trend analysis and matched filtering, which give a separated local anomaly that is a comprehensive reflection of a range from a geological body at a depth upward to the surface. Due to the interference of near-surface geological bodies and other sources, the separated local anomaly is complicated in composition, messy in form and irregular. Wavelet multi-scale analysis gives N-order （N〉I） detail anomaly to mark off local anomaly that represents an integrated reflection of a geological body from depth A to depth B. Without first-order detail anomaly that corresponds to shallow geological bodies and interfering sources, this anomaly is simple in composition, regular in form as a natural reflection of deep geological body, applicable to study of concealed rock masses and ore deposits. This paper interpreted 1：10000 ground magnetic survey data collected from the Yueshan area in 1980s by secondary development, presented local anomaly results by wavelet multi-scale analysis, of which 3 anomalies are coincided with 3 mineral sections in the Zhuchong iron ore deposit that are later found. So the rest several local anomalies with similar geological conditions are prospective for finding new deposits.